Fault parameter constraints using relocated earthquakes: A validation of first-motion focal-mechanism data

USGS Publications Warehouse

Kilb, Debi; Hardebeck, J.L.

2006-01-01

We estimate the strike and dip of three California fault segments (Calaveras, Sargent, and a portion of the San Andreas near San Jaun Bautistia) based on principle component analysis of accurately located microearthquakes. We compare these fault orientations with two different first-motion focal mechanism catalogs: the Northern California Earthquake Data Center (NCEDC) catalog, calculated using the FPFIT algorithm (Reasenberg and Oppenheimer, 1985), and a catalog created using the HASH algorithm that tests mechanism stability relative to seismic velocity model variations and earthquake location (Hardebeck and Shearer, 2002). We assume any disagreement (misfit >30° in strike, dip, or rake) indicates inaccurate focal mechanisms in the catalogs. With this assumption, we can quantify the parameters that identify the most optimally constrained focal mechanisms. For the NCEDC/FPFIT catalogs, we find that the best quantitative discriminator of quality focal mechanisms is the station distribution ratio (STDR) parameter, an indicator of how the stations are distributed about the focal sphere. Requiring STDR > 0.65 increases the acceptable mechanisms from 34%–37% to 63%–68%. This suggests stations should be uniformly distributed surrounding, rather than aligning, known fault traces. For the HASH catalogs, the fault plane uncertainty (FPU) parameter is the best discriminator, increasing the percent of acceptable mechanisms from 63%–78% to 81%–83% when FPU ≤ 35°. The overall higher percentage of acceptable mechanisms and the usefulness of the formal uncertainty in identifying quality mechanisms validate the HASH approach of testing for mechanism stability.

Neo-Deterministic Seismic Hazard Assessment at Watts Bar Nuclear Power Plant Site, Tennessee, USA

NASA Astrophysics Data System (ADS)

Brandmayr, E.; Cameron, C.; Vaccari, F.; Fasan, M.; Romanelli, F.; Magrin, A.; Vlahovic, G.

2017-12-01

Watts Bar Nuclear Power Plant (WBNPP) is located within the Eastern Tennessee Seismic Zone (ETSZ), the second most naturally active seismic zone in the US east of the Rocky Mountains. The largest instrumental earthquakes in the ETSZ are M 4.6, although paleoseismic evidence supports events of M≥6.5. Events are mainly strike-slip and occur on steeply dipping planes at an average depth of 13 km. In this work, we apply the neo-deterministic seismic hazard assessment to estimate the potential seismic input at the plant site, which has been recently targeted by the Nuclear Regulatory Commission for a seismic hazard reevaluation. First, we perform a parametric test on some seismic source characteristics (i.e. distance, depth, strike, dip and rake) using a one-dimensional regional bedrock model to define the most conservative scenario earthquakes. Then, for the selected scenario earthquakes, the estimate of the ground motion input at WBNPP is refined using a two-dimensional local structural model (based on the plant's operator documentation) with topography, thus looking for site amplification and different possible rupture processes at the source. WBNNP features a safe shutdown earthquake (SSE) design with PGA of 0.18 g and maximum spectral amplification (SA, 5% damped) of 0.46 g (at periods between 0.15 and 0.5 s). Our results suggest that, although for most of the considered scenarios the PGA is relatively low, SSE values can be reached and exceeded in the case of the most conservative scenario earthquakes.

Earthquake processes in the Rainbow Mountain-Fairview Peak-Dixie Valley, Nevada, region 1954-1959

NASA Astrophysics Data System (ADS)

Doser, Diane I.

1986-11-01

The 1954 Rainbow Mountain-Fairview Peak-Dixie Valley, Nevada, sequence produced the most extensive pattern of surface faults in the intermountain region in historic time. Five earthquakes of M>6.0 occurred during the first 6 months of the sequence, including the December 16, 1954, Fairview Peak (M = 7.1) and Dixie Valley (M = 6.8) earthquakes. Three 5.5≤M≤6.5 earthquakes occurred in the region in 1959, but none exhibited surface faulting. The results of the modeling suggest that the M>6.5 earthquakes of this sequence are complex events best fit by multiple source-time functions. Although the observed surface displacements for the July and August 1954 events showed only dip-slip motion, the fault plane solutions and waveform modeling suggest the earthquakes had significant components of right-lateral strike-slip motion (rakes of -135° to -145°). All of the earthquakes occurred along high-angle faults with dips of 40° to 70°. Seismic moments for individual subevents of the sequence range from 8.0 × 1017 to 2.5 × 1019 N m. Stress drops for the subevents, including the Fairview Peak subevents, were between 0.7 and 6.0 MPa.

Joint Inversion of Source Location and Source Mechanism of Induced Microseismics

NASA Astrophysics Data System (ADS)

Liang, C.

2014-12-01

Seismic source mechanism is a useful property to indicate the source physics and stress and strain distribution in regional, local and micro scales. In this study we jointly invert source mechanisms and locations for microseismics induced in fluid fracturing treatment in the oil and gas industry. For the events that are big enough to see waveforms, there are quite a few techniques can be applied to invert the source mechanism including waveform inversion, first polarity inversion and many other methods and variants based on these methods. However, for events that are too small to identify in seismic traces such as the microseismics induced by the fluid fracturing in the Oil and Gas industry, a source scanning algorithms (SSA for short) with waveform stacking are usually applied. At the same time, a joint inversion of location and source mechanism are possible but at a cost of high computation budget. The algorithm is thereby called Source Location and Mechanism Scanning Algorithm, SLMSA for short. In this case, for given velocity structure, all possible combinations of source locations (X,Y and Z) and source mechanism (Strike, Dip and Rake) are used to compute travel-times and polarities of waveforms. Correcting Normal moveout times and polarities, and stacking all waveforms, the (X, Y, Z , strike, dip, rake) combination that gives the strongest stacking waveform is identified as the solution. To solve the problem of high computation problem, CPU-GPU programing is applied. Numerical datasets are used to test the algorithm. The SLMSA has also been applied to a fluid fracturing datasets and reveal several advantages against the location only method: (1) for shear sources, the source only program can hardly locate them because of the canceling out of positive and negative polarized traces, but the SLMSA method can successfully pick up those events; (2) microseismic locations alone may not be enough to indicate the directionality of micro-fractures. The statistics of source mechanisms can certainly provide more knowledges on the orientation of fractures; (3) in our practice, the joint inversion method almost always yield more events than the source only method and for those events that are also picked by the SSA method, the stacking power of SLMSA are always higher than the ones obtained in SSA.

Source parameter inversion of compound earthquakes on GPU/CPU hybrid platform

NASA Astrophysics Data System (ADS)

Wang, Y.; Ni, S.; Chen, W.

2012-12-01

Source parameter of earthquakes is essential problem in seismology. Accurate and timely determination of the earthquake parameters (such as moment, depth, strike, dip and rake of fault planes) is significant for both the rupture dynamics and ground motion prediction or simulation. And the rupture process study, especially for the moderate and large earthquakes, is essential as the more detailed kinematic study has became the routine work of seismologists. However, among these events, some events behave very specially and intrigue seismologists. These earthquakes usually consist of two similar size sub-events which occurred with very little time interval, such as mb4.5 Dec.9, 2003 in Virginia. The studying of these special events including the source parameter determination of each sub-events will be helpful to the understanding of earthquake dynamics. However, seismic signals of two distinctive sources are mixed up bringing in the difficulty of inversion. As to common events, the method(Cut and Paste) has been proven effective for resolving source parameters, which jointly use body wave and surface wave with independent time shift and weights. CAP could resolve fault orientation and focal depth using a grid search algorithm. Based on this method, we developed an algorithm(MUL_CAP) to simultaneously acquire parameters of two distinctive events. However, the simultaneous inversion of both sub-events make the computation very time consuming, so we develop a hybrid GPU and CPU version of CAP(HYBRID_CAP) to improve the computation efficiency. Thanks to advantages on multiple dimension storage and processing in GPU, we obtain excellent performance of the revised code on GPU-CPU combined architecture and the speedup factors can be as high as 40x-90x compared to classical cap on traditional CPU architecture.As the benchmark, we take the synthetics as observation and inverse the source parameters of two given sub-events and the inversion results are very consistent with the true parameters. For the events in Virginia, USA on 9 Dec, 2003, we re-invert source parameters and detailed analysis of regional waveform indicates that Virginia earthquake included two sub-events which are Mw4.05 and Mw4.25 at the same depth of 10km with focal mechanism of strike65/dip32/rake135, which are consistent with previous study. Moreover, compared to traditional two-source model method, MUL_CAP is more automatic with no need for human intervention.

A quantitative approach to the loading rate of seismogenic sources in Italy

NASA Astrophysics Data System (ADS)

Caporali, Alessandro; Braitenberg, Carla; Montone, Paola; Rossi, Giuliana; Valensise, Gianluca; Viganò, Alfio; Zurutuza, Joaquin

2018-03-01

To investigate the transfer of elastic energy between a regional stress field and a set of localized faults we project the stress rate tensor inferred from the Italian GNSS velocity field onto faults selected from the Database of Individual Seismogenic Sources (DISS 3.2.0). For given Lamé constants and friction coefficient we compute the loading rate on each fault in terms of the Coulomb Failure Function (CFF) rate. By varying the strike, dip and rake angles around the nominal DISS values, we also estimate the geometry of planes that are optimally oriented for maximal CFF rate. Out of 86 Individual Seismogenic Sources (ISSs), all well covered by GNSS data, 78 to 81 (depending on the assumed friction coefficient) load energy at a rate of 0-4 kPa/yr. The faults displaying larger CFF rates (4 to 6 ± 1 kPa/yr) are located in the central Apennines and are all characterized by a significant strike-slip component. We also find that the loading rate of 75 per cent of the examined sources is less than 1 kPa/yr lower than that of optimally oriented faults. We also analyzed the 24 August and 30 October 2016, central Apennines earthquakes (Mw 6.0-6.5 respectively). The strike of their causative faults based on seismological and tectonic data and the geodetically inferred strike differ by < 30°. Some sources exhibit a strike oblique to the direction of maximum strain rate, suggesting that in some instances the present-day stress acts on inherited faults. The choice of the friction coefficient only marginally affects this result.

Source Rupture Process of the 2016 Kumamoto Prefecture, Japan, Earthquake Derived from Near-Source Strong-Motion Records

NASA Astrophysics Data System (ADS)

Zheng, A.; Zhang, W.

2016-12-01

On 15 April, 2016 the great earthquake with magnitude Mw7.1 occurred in Kumamoto prefecture, Japan. The focal mechanism solution released by F-net located the hypocenter at 130.7630°E, 32.7545°N, at a depth of 12.45 km, and the strike, dip, and the rake angle of the fault were N226°E, 84° and -142° respectively. The epicenter distribution and focal mechanisms of aftershocks implied the mechanism of the mainshock might have changed in the source rupture process, thus a single focal mechanism was not enough to explain the observed data adequately. In this study, based on the inversion result of GNSS and InSAR surface deformation with active structures for reference, we construct a finite fault model with focal mechanism changes, and derive the source rupture process by multi-time-window linear waveform inversion method using the strong-motion data (0.05 1.0Hz) obtained by K-NET and KiK-net of Japan. Our result shows that the Kumamoto earthquake is a right-lateral strike slipping rupture event along the Futagawa-Hinagu fault zone, and the seismogenic fault is divided into a northern segment and a southern one. The strike and the dip of the northern segment are N235°E, 60° respectively. And for the southern one, they are N205°E, 72° respectively. The depth range of the fault model is consistent with the depth distribution of aftershocks, and the slip on the fault plane mainly concentrate on the northern segment, in which the maximum slip is about 7.9 meter. The rupture process of the whole fault continues for approximately 18-sec, and the total seismic moment released is 5.47×1019N·m (Mw 7.1). In addition, the essential feature of the distribution of PGV and PGA synthesized by the inversion result is similar to that of observed PGA and seismic intensity.

Source Rupture Process of the 2016 Kumamoto, Japan, Earthquake Inverted from Strong-Motion Records

NASA Astrophysics Data System (ADS)

Zhang, Wenbo; Zheng, Ao

2017-04-01

On 15 April, 2016 the great earthquake with magnitude Mw7.1 occurred in Kumamoto prefecture, Japan. The focal mechanism solution released by F-net located the hypocenter at 130.7630°E, 32.7545°N, at a depth of 12.45 km, and the strike, dip, and the rake angle of the fault were N226°E, 84˚ and -142° respectively. The epicenter distribution and focal mechanisms of aftershocks implied the mechanism of the mainshock might have changed in the source rupture process, thus a single focal mechanism was not enough to explain the observed data adequately. In this study, based on the inversion result of GNSS and InSAR surface deformation with active structures for reference, we construct a finite fault model with focal mechanism changes, and derive the source rupture process by multi-time-window linear waveform inversion method using the strong-motion data (0.05 1.0Hz) obtained by K-NET and KiK-net of Japan. Our result shows that the Kumamoto earthquake is a right-lateral strike slipping rupture event along the Futagawa-Hinagu fault zone, and the seismogenic fault is divided into a northern segment and a southern one. The strike and the dip of the northern segment are N235°E, 60˚ respectively. And for the southern one, they are N205°E, 72˚ respectively. The depth range of the fault model is consistent with the depth distribution of aftershocks, and the slip on the fault plane mainly concentrate on the northern segment, in which the maximum slip is about 7.9 meter. The rupture process of the whole fault continues for approximately 18-sec, and the total seismic moment released is 5.47×1019N·m (Mw 7.1). In addition, the essential feature of the distribution of PGV and PGA synthesized by the inversion result is similar to that of observed PGA and seismic intensity.

A quantitative approach to the loading rate of seismogenic sources in Italy

NASA Astrophysics Data System (ADS)

Caporali, Alessandro; Braitenberg, Carla; Montone, Paola; Rossi, Giuliana; Valensise, Gianluca; Viganò, Alfio; Zurutuza, Joaquin

2018-06-01

To investigate the transfer of elastic energy between a regional stress field and a set of localized faults, we project the stress rate tensor inferred from the Italian GNSS (Global Navigation Satellite Systems) velocity field onto faults selected from the Database of Individual Seismogenic Sources (DISS 3.2.0). For given Lamé constants and friction coefficient, we compute the loading rate on each fault in terms of the Coulomb failure function (CFF) rate. By varying the strike, dip and rake angles around the nominal DISS values, we also estimate the geometry of planes that are optimally oriented for maximal CFF rate. Out of 86 Individual Seismogenic Sources (ISSs), all well covered by GNSS data, 78-81 (depending on the assumed friction coefficient) load energy at a rate of 0-4 kPa yr-1. The faults displaying larger CFF rates (4-6 ± 1 kPa yr-1) are located in the central Apennines and are all characterized by a significant strike-slip component. We also find that the loading rate of 75% of the examined sources is less than 1 kPa yr-1 lower than that of optimally oriented faults. We also analysed 2016 August 24 and October 30 central Apennines earthquakes (Mw 6.0-6.5, respectively). The strike of their causative faults based on seismological and tectonic data and the geodetically inferred strike differ by <30°. Some sources exhibit a strike oblique to the direction of maximum strain rate, suggesting that in some instances the present-day stress acts on inherited faults. The choice of the friction coefficient only marginally affects this result.

Fault Slip Distribution of the 2016 Fukushima Earthquake Estimated from Tsunami Waveforms

NASA Astrophysics Data System (ADS)

Gusman, Aditya Riadi; Satake, Kenji; Shinohara, Masanao; Sakai, Shin'ichi; Tanioka, Yuichiro

2017-08-01

The 2016 Fukushima normal-faulting earthquake (Mjma 7.4) occurred 40 km off the coast of Fukushima within the upper crust. The earthquake generated a moderate tsunami which was recorded by coastal tide gauges and offshore pressure gauges. First, the sensitivity of tsunami waveforms to fault dimensions and depths was examined and the best size and depth were determined. Tsunami waveforms computed based on four available focal mechanisms showed that a simple fault striking northeast-southwest and dipping southeast (strike = 45°, dip = 41°, rake = -95°) yielded the best fit to the observed waveforms. This fault geometry was then used in a tsunami waveform inversion to estimate the fault slip distribution. A large slip of 3.5 m was located near the surface and the major slip region covered an area of 20 km × 20 km. The seismic moment, calculated assuming a rigidity of 2.7 × 1010 N/m2 was 3.70 × 1019 Nm, equivalent to Mw = 7.0. This is slightly larger than the moments from the moment tensor solutions (Mw 6.9). Large secondary tsunami peaks arrived approximately an hour after clear initial peaks were recorded by the offshore pressure gauges and the Sendai and Ofunato tide gauges. Our tsunami propagation model suggests that the large secondary tsunami signals were from tsunami waves reflected off the Fukushima coast. A rather large tsunami amplitude of 75 cm at Kuji, about 300 km north of the source, was comparable to those recorded at stations located much closer to the epicenter, such as Soma and Onahama. Tsunami simulations and ray tracing for both real and artificial bathymetry indicate that a significant portion of the tsunami wave was refracted to the coast located around Kuji and Miyako due to bathymetry effects.

Normal Faulting in the 1923 Berdún Earthquake and Postorogenic Extension in the Pyrenees

NASA Astrophysics Data System (ADS)

Stich, Daniel; Martín, Rosa; Batlló, Josep; Macià, Ramón; Mancilla, Flor de Lis; Morales, Jose

2018-04-01

The 10 July 1923 earthquake near Berdún (Spain) is the largest instrumentally recorded event in the Pyrenees. We recover old analog seismograms and use 20 hand-digitized waveforms for regional moment tensor inversion. We estimate moment magnitude Mw 5.4, centroid depth of 8 km, and a pure normal faulting source with strike parallel to the mountain chain (N292°E), dip of 66° and rake of -88°. The new mechanism fits into the general predominance of normal faulting in the Pyrenees and extension inferred from Global Positioning System data. The unique location of the 1923 earthquake, near the south Pyrenean thrust front, shows that the extensional regime is not confined to the axial zone where high topography and the crustal root are located. Together with seismicity near the northern mountain front, this indicates that gravitational potential energy in the western Pyrenees is not extracted locally but induces a wide distribution of postorogenic deformation.

Sumatran orangutans differ in their cultural knowledge but not in their cognitive abilities.

PubMed

Gruber, Thibaud; Singleton, Ian; van Schaik, Carel

2012-12-04

Animal cultures are controversial because the method used to isolate culture in animals aims at excluding genetic and environmental influences rather than demonstrating social learning. Here, we analyzed these factors in parallel in captivity to determine their influences on tool use. We exposed Sumatran orangutan (Pongo abelii) orphans from tool-using and non-tool-using regions (western swamps and eastern Langkat, respectively) that differed in both genetic and cultural backgrounds to a raking task and a honey-dipping task to assess their understanding of stick use. Orangutans from both regions were equally successful in raking; however, swamp orangutans were more successful than Langkat orangutans in honey dipping, where previously acquired knowledge was required. A larger analysis suggested that the Alas River could constitute a geographical barrier to the spread of this cultural trait. Finally, honey-dipping individuals were on average less than 4 years old, but this behavior is not observed in the wild before 6 years of age. Our results suggest first that genetic differences between wild Sumatran populations cannot explain their differences in stick use; however, their performances in honey dipping support a cultural differentiation in stick knowledge. Second, the results suggest that the honey-dippers were too young when arriving at the quarantine center to have possibly mastered the behavior in the wild individually, suggesting that they arrived with preestablished mental representations of stick use or, simply put, "cultural ideas." Copyright © 2012 Elsevier Ltd. All rights reserved.

Inversion analysis of slip distribution of the 2008 Iwate-Miyagi Nairiku earthquake: Very high stress-drop or a conjugate fault slip?

NASA Astrophysics Data System (ADS)

Fukahata, Y.; Fukushima, Y.

2009-05-01

On 14 June 2008, the Iwate-Miyagi Nairiku earthquake struck northeast Japan, where active seismicity has been observed under east-west compressional stress fields. The magnitude and hypocenter depth of the earthquake are reported as Mj 7.2 and 8 km, respectively. The earthquake is considered to have occurred on a west-dipping reverse fault with a roughly north-south strike. The earthquake caused significant surface displacements, which were detected by PALSAR, a Synthetic Aperture Radar (SAR) onboard the Japanese ALOS satellite. Several pairs of PALSAR images from six different paths are available to measure the coseismic displacements. Interferometric SAR (InSAR) is useful to obtain crustal displacements in the region where coseismic displacement is not so large (less than 1 m), whereas range and azimuth offsets provide displacement measurements up to a few meters on the whole processed area. We inverted the obtained displacement data to estimate slip distribution on the fault. Since the precise location and direction of the fault are not well known, the inverse problem is nonlinear. Following the method of Fukahata and Wright (2008), we resolved the weak non-linearity based on Akaike's Bayesian Information Criterion. We first estimated slip distribution by assuming a pure dip slip. The optimal fault geometry was estimated at dip 26 and strike 203 degrees. The maximum slip is more than 8 m and most slips concentrate at shallow depths (less than 4 km). The azimuth offset data suggest non-negligible right lateral slip components, so we next estimated slip distribution without fixing the rake angle. Again, a large slip area with the maximum slip of about 8 m in the shallow depth was obtained. Such slip models contradict with our existing common sense; our results indicate that the released strain is more than 10 to the power of -3. Range and azimuth offsets computed from SAR images obtained from both ascending and descending orbits appear to be more consistent with a conjugate fault slip, which contributes to lower the stress drop possibly to a level typical to this kind of earthquakes.

Investigating the Local Three-dimensional Velocity Structure of the 2008 Taoyuan Earthquake Sequence of Kaohsiung, Taiwan

NASA Astrophysics Data System (ADS)

Shih, M. H.; Huang, B. S.

2016-12-01

March 4, 2008, a moderate earthquake (ML 5.2) occurred in Taoyuan district of Kaohsiung County in the southern Taiwan. It was followed by numerous aftershocks in the following 48 hours, including three events with magnitude larger than 4. The Taoyuan earthquake sequence occurred during the TAIGER (Taiwan Integrated Geodynamic Research) project which is to image lithospheric structure of Taiwan orogeny. The high-resolution waveform data of this sequence were well-recorded by a large number of recording stations belong to several different permanent and TAIGER networks all around Taiwan. We had collected the waveform data and archived to a mega database. Then, we had identified 2,340 events from database in the preliminary locating process by using 1-D velocity model. In this study, we applied the double-difference tomography to investigate not only the fault geometry of the main shock but also the detailed 3-D velocity structure in this area. A total of 3,034 events were selected from preliminary locating result and CWBSN catalog in the vicinity. The resulting aftershocks are extended along the NE-SW direction and located on a 45° SE-dipping plane which agrees to one of the nodal planes of Global CMT solution (strike = 45°, dip = 40° and rake = 119°). We can identify a clear low-velocity area which is enclosed by events next to the main shock in the final 3D velocity model. We also recognized a 45°-dipping zone which is extended to the ground surface with low-velocity; meanwhile, velocity structure variation in study area correspond with major geologic units in Taiwan.

Characteristics of fractures in crystalline bedrock determined by surface and borehole geophysical surveys, eastern surplus superfund site, Meddybemps, Maine

USGS Publications Warehouse

Hansen, Bruce P.; Stone, Janet Radway; Lane, John W.

1999-01-01

Surface and borehole geophysical methods were used to determine fracture orientation in crystalline bedrock at the Eastern Surplus Superfund Site in Meddybemps, Maine. Fracture-orientation information is needed to address concerns about the fate of contaminants in ground water at the site. Azimuthal square-array resistivity surveys were conducted at 3 locations at the site, borehole-acoustic televiewer and borehole-video logs were collected in 10 wells, and single-hole directional radar surveys were conducted in 9 wells. Borehole-video logs were used to supplement the results of other geophysical techniques and are not described in this report. Analysis of azimuthal square-array resistivity data indicated that high-angle fracturing generally strikes northeast-southwest at the three locations. Borehole-acoustic televiewer logs detected one prominent low-angle and two prominent high-angle fracture sets. The low-angle fractures strike generally north-northeast and dip about 20 degrees west-northwest. One high-angle fracture set strikes north-northeast and dips east-southeast; the other high-angle set strikes east-northeast and dips south-southeast. Single-hole directional radar surveys identified two prominent fracture sets: a low-angle set striking north-northeast, dipping west-northwest; and a high-angle fracture set striking north-northeast, dipping east-southeast. Two additional high-angle fracture sets are defined weakly, one striking east-west, dipping north; and a second striking east-west, dipping south. Integrated results from all of the geophysical surveys indicate the presence of three primary fracture sets. A low-angle set strikes north-northeast and dips west-northwest. Two high-angle sets strike north-northeast and east-northeast and dip east-southeast and south-southeast. Statistical correction of the fracture data for orientation bias indicates that high-angle fractures are more numerous than observed in the data but are still less numerous than the low-angle fractures. The orientation and distribution of water-yielding fractures sets were determined by correlating the fracture data from this study with previously collected borehole-flowmeter data. The water-yielding fractures are generally within the three prominent fracture sets observed for the total fracture population. The low-angle water-yielding fractures primarily strike north-northeast to west-northwest and dip west-northwest to south-southwest. Most of the high-angle water-yielding fractures strike either north-northeast or east-west and dip east-southeast or south. The spacing between water-yielding fractures varies but the probable average spacing is estimated to be 30 feet for low-angle fractures; 27 feet for the east-southeast dipping, high-angle fractures; and 43 feet for the south-southeast dipping, high-angle fractures. The median estimated apparent transmissivity of individual water-yielding fractures or fracture zones was 0.3 feet squared per day and ranged from 0.01 to 382 feet squared per day. Ninety-five percent of the water-yielding fractures or fracture zones had an estimated apparent transmissivity of 19.5 feet squared per day or less. The orientation, spacing, and hydraulic properties of water-yielding fractures identified during this study can be used to help estimate recharge, flow, and discharge of ground water contaminants. High-angle fractures provide vertical pathways for ground water to enter the bedrock, interconnections between low-angle fractures, and, subsequently, pathways for water flow within the bedrock along fracture planes. Low-angle fractures may allow horizontal ground-water flow in all directions. The orientation of fracturing and the hydraulic properties of each fracture set strongly affect changes in ground-water flow under stress (pumping) conditions.

The Mw 5.9 February 2014 Cephalonia earthquake (Greece): 3D deformation field and source modeling from multiple SAR techniques

NASA Astrophysics Data System (ADS)

Merryman Boncori, John Peter; Papoutsis, Ioannis; Pezzo, Giuseppe; Tolomei, Cristiano; Atzori, Simone; Ganas, Athanassios; Karastathis, Vassilios; Salvi, Stefano; Kontoes, Charalampos; Antonioli, Andrea

2015-04-01

On Jan. 26, 2014 at 13:55 UTC an Mw 6.0 earthquake struck the island of Cephalonia, Greece, followed five hours later by an Mw 5.3 aftershock, and by an Mw 5.9 event on Feb. 3, 2014 (National Observatory of Athens, Institute of Geodynamics), causing extensive structural damages and inducing widespread environmental effects. We measured the 3D coseismic deformation field of the Feb. 3, 2014 event, by applying Differential Synthetic Aperture Radar Interferometry (DInSAR), Intensity cross-correlation and Spectral Diversity (also known as Multi Aperture Interferometry) to descending passes of the Italian Space Agency (ASI) COSMO-SkyMed satellites and ascending passes of the German Space Agency (DLR) TanDEM-X satellite. These techniques allowed the observation of four independent displacement components (descending and ascending radar line-of-sight and azimuth), each of which was measured with two different techniques, resulting in an increased spatial coverage, robustness and sensitivity to all Cartesian displacement components. Our SAR measurements were found to be in very good agreement with those from available continuous Global Positioning System (cGPS) stations. We modeled the seismic source of the Feb. 3, 2014 earthquake with a joint inversion of the eight SAR displacement maps, using the analytical solutions for dislocation in an elastic half-space. Firstly, we considered a model based on a single-fault plane and carried out a non-linear inversion to estimate its geometric and kinematic source parameters, assuming a uniform slip. Subsequently, we performed a linear inversion to retrieve the slip distribution, adopting a damped and Non-Negative Least Squares approach. Slip values were computed on a variable-size mesh, which maximizes the model resolution matrix. We find the majority of the observed surface deformation to be explained by a 20 km long ~N-S oriented and west-dipping fault running parallel to the east coast of the Paliki peninsula, with a main right-lateral strike-slip mechanism and a lesser reverse component (rake=147°). The slip on this structure is mostly confined to depths shallower than 5 km. However a comparison of observed and modelled displacements, suggests a non-negligible slip to occur also along a second structure, ~10 km in length, located in the south of Paliki and striking NE-SW. We therefore performed a second inversion of the SAR displacement maps, finding a dominant right-lateral strike-slip mechanism (rake=164°) and a high dip angle (76°) for the NE-SW striking fault. Most of the slip on this latter structure is found to occur at depths between 2 km and 5 km, although our model is poorly constrained at greater depths. Inclusion of the NE-SW fault in the source model is found to significantly improve the fit to all observed displacements in the south-east of the Paliki peninsula. Finally, we compare the full moment-tensor derived from our models to those obtained by several global and regional seismic networks. We also compare the slip distributions resulting from our inversions to hypocenter relocations based on a 2D velocity model, which accounts for a non-horizontal Moho structure. A remarkable agreement is found, which also allows several considerations to be made on the rupture mechanism.

Bermuda earthquake of March 24, 1978: A significant oceanic intraplate event

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stewart, G.S.; Helmberger, D.V.

1981-08-10

The Bremuda earthquake (Mapprox.6) occured near the westerly extension of the Kane Fracture Zone roughly 370 km southwest of the island of Bermuda. It is one of the largest oceanic intraplate earthquakes to occur off the eastern coast of North America. Because of its size and location, it has provided an excellent set of WWSSN body waves. They can be used to infer its depth and faulting parameters by waveform modeling techniques. The results indicate a north-northwest striking thrust mechanism (strike = N20 /sup 0/W, dip = 42 /sup 0/NE, rake = 90/sup 0/) with the hypocenter located at amore » depth of 11 km, which for an oceanic crust places it predominantly in the mantle. The event had a seismic moment of 3.4 x 10/sup 25/ dyne cm, and its time history was modeled with a symmetric trapezoidal time function 3 s in duration. The north-northwest strike of the event is in good agreement with the bathymetry of the area, the epicenter being close to the southwestern edge of the Bermuda Rise. The strike of the event is also close to that of the inferred extensions of the present ridge fracture zones in the region. The strike of the event is also close to that of the inferred extensions of the present ridge fracture zones in the region. The presence of fracture zones is indicative of local weak zones in the lithosphere. The Bermuda earthquake most likely is associated with one of these zones of weakness and is the result of the application of present day stress imposed on the region by the North American plate in the direction of its absolute motion. This is an important event in terms of understanding and estimating seismic hazard on the eastern seaboard of North America.« less

Methods to enhance seismic faults and construct fault surfaces

NASA Astrophysics Data System (ADS)

Wu, Xinming; Zhu, Zhihui

2017-10-01

Faults are often apparent as reflector discontinuities in a seismic volume. Numerous types of fault attributes have been proposed to highlight fault positions from a seismic volume by measuring reflection discontinuities. These attribute volumes, however, can be sensitive to noise and stratigraphic features that are also apparent as discontinuities in a seismic volume. We propose a matched filtering method to enhance a precomputed fault attribute volume, and simultaneously estimate fault strikes and dips. In this method, a set of efficient 2D exponential filters, oriented by all possible combinations of strike and dip angles, are applied to the input attribute volume to find the maximum filtering responses at all samples in the volume. These maximum filtering responses are recorded to obtain the enhanced fault attribute volume while the corresponding strike and dip angles, that yield the maximum filtering responses, are recoded to obtain volumes of fault strikes and dips. By doing this, we assume that a fault surface is locally planar, and a 2D smoothing filter will yield a maximum response if the smoothing plane coincides with a local fault plane. With the enhanced fault attribute volume and the estimated fault strike and dip volumes, we then compute oriented fault samples on the ridges of the enhanced fault attribute volume, and each sample is oriented by the estimated fault strike and dip. Fault surfaces can be constructed by directly linking the oriented fault samples with consistent fault strikes and dips. For complicated cases with missing fault samples and noisy samples, we further propose to use a perceptual grouping method to infer fault surfaces that reasonably fit the positions and orientations of the fault samples. We apply these methods to 3D synthetic and real examples and successfully extract multiple intersecting fault surfaces and complete fault surfaces without holes.

Structural control on the CO2 release west of Mt. Epomeo resurgent block (Ischia, Italy)

NASA Astrophysics Data System (ADS)

de Vita, S.; Marotta, E.; Ventura, G.; Chiodini, G.

2003-04-01

Volcanism at Ischia started more than 150 ka B.P. and continued until the last eruption occurred in 1302 A.D. Ischia is dominated by the caldera forming eruption of Mt. Epomeo Green Tuff (55 ka), which was followed by block resurgence inside the caldera from 33 ka B.P. Resurgence influenced the volcanic activity determining the conditions for magma ascent mainly along the eastern edge of the resurgent block. The resurgent area has a poligonal shape resulting from reactivation of regional faults and by activation of faults related to volcanotectonism. The western sector is bordered by inward dipping, high angle strike-slip/reverse faults testifying a compressional stress regime in this area. These features are cut by late outward dipping normal faults due to gravitational stress. The activity of the volcanic system is testified by seismicity and thermal manifestations. Fumarolic activity concentrates along the faults that borders westward the Mt. Epomeo resurgent block, where the Green Tuff overlies fractured lavas. The structural data show that, outside the most active degassing zone, fractures show a NNW-SSE strike and dip toward Mt. Epomeo. These fractures delimit the northern sector of Mt. Epomeo and show strike and dip consistent with the inward dipping reverse faults. Inside the degassing area fractures show a NW-SE strike and dip outward Mt. Epomeo. These gravity-related faults cut the lavas where the hydrothermal circulation is active. The dip direction of the NW-SE striking fractures within the degassing zone is not consistent with that of the strike-slip/reverse faults (i.e. towards NE) but agrees well with that of the gravity-induced faults (dip direction towards SW). Inside the degassing zone, NW-SE striking faults with lengths not exceeding the hydrothermalized extension occur. This arrangement indicate that the syn-resurgence faults act as permeability barriers, whereas the youngest faults act as the main fluid pathway.

Biomechanics of a convergently derived prey-processing mechanism in fishes: evidence from comparative tongue bite apparatus morphology and raking kinematics.

PubMed

Konow, Nicolai; Sanford, Christopher P J

2008-11-01

A tongue-bite apparatus (TBA) governs raking behaviors in two major and unrelated teleost lineages, the osteoglossomorph and salmoniform fishes. We present data on comparative morphology and kinematics from two representative species, the rainbow trout (Oncorhynchus mykiss) and the Australian arowana (Scleropages jardinii), which suggest that both the TBA and raking are convergently derived in these lineages. Similar TBA morphologies were present, except for differences in TBA dentition and shape of the novel cleithrobranchial ligament (CBL), which is arc-shaped in O. mykiss and straight in S. jardinii. Eight kinematic variables were used to quantify motion magnitude and maximum-timing in the kinematic input mechanisms of the TBA. Five variables differed inter-specifically (pectoral girdle retraction magnitude and timing, cranial and hyoid elevation and gape-distance timing), yet an incomplete taxon separation across multivariate kinematic space demonstrated an overall similarity in raking behavior. An outgroup analysis using bowfin (Amia calva) and pickerel (Esox americanus) to compare kinematics of raking with chewing and prey-capture provided robust quantitative evidence of raking being a convergently derived behavior. Support was also found for the notion that raking more likely evolved from the strike, a functionally distinct behavior, than from chewing, an alternative prey-processing behavior. Based on raking kinematic and muscle-activity data, we propose biomechanical models of the three input mechanisms that govern kinematics of the basihyal output mechanism during the raking power stroke: (1) cranial elevation protracts the upper TBA jaw from the lower (basihyal) TBA jaw; (2) basihyal retraction is caused directly by contraction of the sternohyoideus (SH); (3) hypaxial shortening, relayed via the pectoral girdle and SH-CBL complex, is an indirect basihyal retraction mechanism modeled as a four-bar linkage. These models will aid future analyses mapping structural and functional traits to the evolution of behaviors.

The 2016 Kaikōura earthquake: Simultaneous rupture of the subduction interface and overlying faults

NASA Astrophysics Data System (ADS)

Wang, Teng; Wei, Shengji; Shi, Xuhua; Qiu, Qiang; Li, Linlin; Peng, Dongju; Weldon, Ray J.; Barbot, Sylvain

2018-01-01

The distribution of slip during an earthquake and how it propagates among faults in the subduction system play a major role in seismic and tsunami hazards, yet they are poorly understood because offshore observations are often lacking. Here we derive the slip distribution and rupture evolution during the 2016 Mw 7.9 Kaikōura (New Zealand) earthquake that reconcile the surface rupture, space geodetic measurements, seismological and tsunami waveform records. We use twelve fault segments, with eleven in the crust and one on the megathrust interface, to model the geodetic data and match the major features of the complex surface ruptures. Our modeling result indicates that a large portion of the moment is distributed on the subduction interface, making a significant contribution to the far field surface deformation and teleseismic body waves. The inclusion of local strong motion and teleseismic waveform data in the joint inversion reveals a unilateral rupture towards northeast with a relatively low averaged rupture speed of ∼1.5 km/s. The first 30 s of the rupture took place on the crustal faults with oblique slip motion and jumped between fault segments that have large differences in strike and dip. The peak moment release occurred at ∼65 s, corresponding to simultaneous rupture of both plate interface and the overlying splay faults with rake angle changes progressively from thrust to strike-slip. The slip on the Papatea fault produced more than 2 m of offshore uplift, making a major contribution to the tsunami at the Kaikōura station, while the northeastern end of the rupture can explain the main features at the Wellington station. Our inversions and simulations illuminate complex up-dip rupture behavior that should be taken into consideration in both seismic and tsunami hazard assessment. The extreme complex rupture behavior also brings new challenges to the earthquake dynamic simulations and understanding the physics of earthquakes.

The Origin of High-angle Dip-slip Earthquakes at Geothermal Fields in California

NASA Astrophysics Data System (ADS)

Barbour, A. J.; Schoenball, M.; Martínez-Garzón, P.; Kwiatek, G.

2016-12-01

We examine the source mechanisms of earthquakes occurring in three California geothermal fields: The Geysers, Salton Sea, and Coso. We find source mechanisms ranging from strike slip faulting, consistent with the tectonic settings, to dip slip with unusually steep dip angles which are inconsistent with local structures. For example, we identify a fault zone in the Salton Sea Geothermal Field imaged using precisely-relocated hypocenters with a dip angle of 60° yet double-couple focal mechanisms indicate higher-angle dip-slip on ≥75° dipping planes. We observe considerable temporal variability in the distribution of source mechanisms. For example, at the Salton Sea we find that the number of high angle dip-slip events increased after 1989, when net-extraction rates were highest. There is a concurrent decline in strike-slip and strike-slip-normal faulting, the mechanisms expected from regional tectonics. These unusual focal mechanisms and their spatio-temporal patterns are enigmatic in terms of our understanding of faulting in geothermal regions. While near-vertical fault planes are expected to slip in a strike-slip sense, and dip slip is expected to occur on moderately dipping faults, we observe dip slip on near-vertical fault planes. However, for plausible stress states and accounting for geothermal production, the resolved fault planes should be stable. We systematically analyze the source mechanisms of these earthquakes using full moment tensor inversion to understand the constraints imposed by assuming a double-couple source. Applied to The Geysers field, we find a significant reduction in the number of high-angle dip-slip mechanisms using the full moment tensor. The remaining mechanisms displaying high-angle dip-slip could be consistent with faults accommodating subsidence and compaction associated with volumetric strain changes in the geothermal reservoir.

Fault Slip Distribution and Optimum Sea Surface Displacement of the 2017 Tehuantepec Earthquake in Mexico (Mw 8.2) Estimated from Tsunami Waveforms

NASA Astrophysics Data System (ADS)

Gusman, A. R.; Satake, K.; Mulia, I. E.

2017-12-01

An intraplate normal fault earthquake (Mw 8.2) occurred on 8 September 2017 in the Tehuantepec seismic gap of the Middle America Trench. The submarine earthquake generated a tsunami which was recorded by coastal tide gauges and offshore DART buoys. We used the tsunami waveforms recorded at 16 stations to estimate the fault slip distribution and an optimum sea surface displacement of the earthquake. A steep fault dipping to the northeast with strike of 315°, dip of 73°and rake of -96° based on the USGS W-phase moment tensor solution was assumed for the slip inversion. To independently estimate the sea surface displacement without assuming earthquake fault parameters, we used the B-spline function for the unit sources. The distribution of the unit sources was optimized by a Genetic Algorithm - Pattern Search (GA-PS) method. Tsunami waveform inversion resolves a spatially compact region of large slip (4-10 m) with a dimension of 100 km along the strike and 80 km along the dip in the depth range between 40 km and 110 km. The seismic moment calculated from the fault slip distribution with assumed rigidity of 6 × 1010 Nm-2 is 2.46 × 1021 Nm (Mw 8.2). The optimum displacement model suggests that the sea surface was uplifted up to 0.5 m and subsided down to -0.8 m. The deep location of large fault slip may be the cause of such small sea surface displacements. The simulated tsunami waveforms from the optimum sea surface displacement can reproduce the observations better than those from fault slip distribution; the normalized root mean square misfit for the sea surface displacement is 0.89, while that for the fault slip distribution is 1.04. We simulated the tsunami propagation using the optimum sea surface displacement model. Large tsunami amplitudes up to 2.5 m were predicted to occur inside and around a lagoon located between Salina Cruz and Puerto Chiapas. Figure 1. a) Sea surface displacement for the 2017 Tehuantepec earthquake estimated by tsunami waveforms. b) Map of simulated maximum tsunami amplitude and comparison between observed (blue circles) and simulated (red circles) tsunami maximum amplitude along the coast.

Near-source high-rate GPS, strong motion and InSAR observations to image the 2015 Lefkada (Greece) Earthquake rupture history.

PubMed

Avallone, Antonio; Cirella, Antonella; Cheloni, Daniele; Tolomei, Cristiano; Theodoulidis, Nikos; Piatanesi, Alessio; Briole, Pierre; Ganas, Athanassios

2017-09-04

The 2015/11/17 Lefkada (Greece) earthquake ruptured a segment of the Cephalonia Transform Fault (CTF) where probably the penultimate major event was in 1948. Using near-source strong motion and high sampling rate GPS data and Sentinel-1A SAR images on two tracks, we performed the inversion for the geometry, slip distribution and rupture history of the causative fault with a three-step self-consistent procedure, in which every step provided input parameters for the next one. Our preferred model results in a ~70° ESE-dipping and ~13° N-striking fault plane, with a strike-slip mechanism (rake ~169°) in agreement with the CTF tectonic regime. This model shows a bilateral propagation spanning ~9 s with the activation of three main slip patches, characterized by rise time and peak slip velocity in the ranges 2.5-3.5 s and 1.4-2.4 m/s, respectively, corresponding to 1.2-1.8 m of slip which is mainly concentrated in the shallower (<10 km) southern half of the causative fault. The inferred slip distribution and the resulting seismic moment (M 0  = 1.05 × 10 19 N m) suggest a magnitude of M w 6.6. Our best solution suggests that the occurrence of large (M w  > 6) earthquakes to the northern and to the southern boundaries of the 2015 causative fault cannot be excluded.

3D Visualization of Earthquake Focal Mechanisms Using ArcScene

USGS Publications Warehouse

Labay, Keith A.; Haeussler, Peter J.

2007-01-01

In addition to the default settings, there are several other options in 3DFM that can be adjusted. The appearance of the symbols can be changed by (1) creating rings around the fault planes that are colored based on magnitude, (2) showing only the fault planes instead of a sphere, (3) drawing a flat disc that identifies the primary nodal plane, (4) or by displaying the null, pressure, and tension axes. The size of the symbols can be changed by adjusting their diameter, scaling them based on the magnitude of the earthquake, or scaling them by the estimated size of the rupture patch based on earthquake magnitude. It is also possible to filter the data using any combination of the strike, dip, rake, magnitude, depth, null axis plunge, pressure axis plunge, tension axis plunge, or fault type values of the points. For a large dataset, these filters can be used to create different subsets of symbols. Symbols created by 3DFM are stored in graphics layers that appear in the ArcScene® table of contents. Multiple graphics layers can be created and saved to preserve the output from different symbol options.

Tsunami Source Inversion Using Tide Gauge and DART Tsunami Waveforms of the 2017 Mw8.2 Mexico Earthquake

NASA Astrophysics Data System (ADS)

Adriano, Bruno; Fujii, Yushiro; Koshimura, Shunichi; Mas, Erick; Ruiz-Angulo, Angel; Estrada, Miguel

2018-01-01

On September 8, 2017 (UTC), a normal-fault earthquake occurred 87 km off the southeast coast of Mexico. This earthquake generated a tsunami that was recorded at coastal tide gauge and offshore buoy stations. First, we conducted a numerical tsunami simulation using a single-fault model to understand the tsunami characteristics near the rupture area, focusing on the nearby tide gauge stations. Second, the tsunami source of this event was estimated from inversion of tsunami waveforms recorded at six coastal stations and three buoys located in the deep ocean. Using the aftershock distribution within 1 day following the main shock, the fault plane orientation had a northeast dip direction (strike = 320°, dip = 77°, and rake =-92°). The results of the tsunami waveform inversion revealed that the fault area was 240 km × 90 km in size with most of the largest slip occurring on the middle and deepest segments of the fault. The maximum slip was 6.03 m from a 30 × 30 km2 segment that was 64.82 km deep at the center of the fault area. The estimated slip distribution showed that the main asperity was at the center of the fault area. The second asperity with an average slip of 5.5 m was found on the northwest-most segments. The estimated slip distribution yielded a seismic moment of 2.9 × 10^{21} Nm (Mw = 8.24), which was calculated assuming an average rigidity of 7× 10^{10} N/m2.

Proximity of the Seismogenic Dog Valley Fault to Stampede and Prosser Creek Dams Near Truckee, California

NASA Astrophysics Data System (ADS)

Cronin, V. S.; Strasser, M. P.

2017-12-01

The M 6.0 Truckee earthquake of 12 September 1966 caused a variety of surface effects observed over a large area, but the rupture plane of the causative fault did not displace the ground surface. The fault that generated the earthquake was named the Dog Valley fault [DVF], and its ground trace was assumed to be within a zone of subparallel drainage lineaments. The plunge and trend of the dip vector for the best fault-plane solution is 80° 134° with 0° rake, corresponding to a steep NE striking left-lateral strike-slip fault (Tsai and Aki, 1970). The Stampede Dam was completed along the trend of the Dog Valley fault in 1970, just four years after the Truckee earthquake, and impounds almost a quarter-million acre-feet of water. Failure of Stampede Dam would compromise Boca Dam downstream and pose a catastrophic threat to people along the Truckee River floodplain to Reno and beyond. Two 30 m long trenches excavated across a suspected DVF trend by the US Bureau of Reclamation in the 1980s did not find evidence of faulting (Hawkins et al., 1986). The surface trace of the DVF has remained unknown. We used the Seismo-Lineament Analysis Method [SLAM] augmented with a total least squares analysis of the focal locations of known or suspected aftershocks, along with focal mechanism data from well located events since 1966, to constrain the search for the DVF ground trace. Geomorphic analysis of recently collected aerial lidar data along this composite seismo-lineament has lead to a preliminary interpretation that the DVF might extend from the Prosser Creek Reservoir near 39.396°N 120.168°W through or immediately adjacent to the Stampede Dam structure. A second compound geomorphic lineament is sub-parallel to this line 1.6 km to the northwest, and might represent another strand of the DVF. As noted by Hawkins et al. (1986), human modification of the land surface complicates structural-geomorphic analysis. Fieldwork in 2016 took advantage of drought conditions to examine the exposed shoreface of Stampede Reservoir near the dam, and exposures of steeply dipping strike-slip faults were found.

Interpretation of Microseismicity Observed From Surface and Borehole Seismic Arrays During Hydraulic Fracturing in Shale - Bedding Plane Slip Model

NASA Astrophysics Data System (ADS)

Stanek, F.; Jechumtalova, Z.; Eisner, L.

2017-12-01

We present a geomechanical model explaining microseismicity induced by hydraulic fracturing in shales developed from many datasets acquired with two most common types of seismic monitoring arrays, surface and dual-borehole arrays. The geomechanical model explains the observed source mechanisms and locations of induced events from two stimulated shale reservoirs. We observe shear dip-slip source mechanisms with nodal planes aligned with location trends. We show that such seismicity can be explained as a shearing along bedding planes caused by aseismic opening of vertical hydraulic fractures. The source mechanism inversion was applied only to selected high-quality events with sufficient signal-to-noise ratio. We inverted P- and P- and S-wave arrival amplitudes to full-moment tensor and decomposed it to shear, volumetric and compensated linear vector dipole components. We also tested an effect of noise presented in the data to evaluate reliability of non-shear components. The observed seismicity from both surface and downhole monitoring of shale stimulations is very similar. The locations of induced microseismic events are limited to narrow depth intervals and propagate along distinct trend(s) showing fracture propagation in direction of maximum horizontal stress from injection well(s). The source mechanisms have a small non-shear component which can be partly explained as an effect of noise in the data, i.e. events represent shearing on faults. We observe predominantly dip-slip events with a strike of the steeper (almost vertical) nodal plane parallel to the fracture propagation. Therefore the other possible nodal plane is almost horizontal. The rake angles of the observed mechanisms divide these dip-slips into two groups with opposite polarities. It means that we observe opposite movements on the nearly identically oriented faults. Realizing a typical structural weakness of shale in horizontal planes, we interpret observed microseismicity as a result of shearing along bedding planes caused by seismically silent (aseismic) vertical fracture opening.

Widespread ground motion distribution caused by rupture directivity during the 2015 Gorkha, Nepal earthquake

NASA Astrophysics Data System (ADS)

Koketsu, Kazuki; Miyake, Hiroe; Guo, Yujia; Kobayashi, Hiroaki; Masuda, Tetsu; Davuluri, Srinagesh; Bhattarai, Mukunda; Adhikari, Lok Bijaya; Sapkota, Soma Nath

2016-06-01

The ground motion and damage caused by the 2015 Gorkha, Nepal earthquake can be characterized by their widespread distributions to the east. Evidence from strong ground motions, regional acceleration duration, and teleseismic waveforms indicate that rupture directivity contributed significantly to these distributions. This phenomenon has been thought to occur only if a strike-slip or dip-slip rupture propagates to a site in the along-strike or updip direction, respectively. However, even though the earthquake was a dip-slip faulting event and its source fault strike was nearly eastward, evidence for rupture directivity is found in the eastward direction. Here, we explore the reasons for this apparent inconsistency by performing a joint source inversion of seismic and geodetic datasets, and conducting ground motion simulations. The results indicate that the earthquake occurred on the underthrusting Indian lithosphere, with a low dip angle, and that the fault rupture propagated in the along-strike direction at a velocity just slightly below the S-wave velocity. This low dip angle and fast rupture velocity produced rupture directivity in the along-strike direction, which caused widespread ground motion distribution and significant damage extending far eastwards, from central Nepal to Mount Everest.

Rocks in a Box: A Three-Point Problem.

ERIC Educational Resources Information Center

Leyden, Michael B.

1981-01-01

Describes a simulation drilling core activity involving the use of a physical model from which students gather data and solve a three-point problem to determine the strike and dip of a buried stratum. Includes descriptions of model making, data plots, and additional problems involving strike and dip. (DS)

InSAR constraints on the kinematics and magnitude of the 2001 Bhuj earthquake

NASA Astrophysics Data System (ADS)

Schmidt, D.; Bürgmann, R.

2005-12-01

The Mw 7.6 Bhuj intraplate event occurred along a blind thrust within the Kutch Rift basin of western India in January of 2001. The lack of any surface rupture and limited geodetic data have made it difficult to place the event on a known fault and constrain its source parameters. Moment tensor solutions and aftershock relocations indicate that the earthquake was a reverse event along an east-west striking, south dipping fault. In an effort to image the surface deformation, we have processed a total of 9 interferograms that span the coseismic event. Interferometry has proven difficult for the region because of technical difficulties experienced by the ERS Satellite around the time of the earthquake and because of low coherence. The stabilization of the orbital control by the European Space Agency beginning in 2002 has allowed us to interfere more recent SAR data with pre-earthquake data. Therefore, all available interferograms of the event include the first year of any postseismic deformation. The source region is characterized by broad floodplains interrupted by isolated highlands. Coherence is limited to the surrounding highlands and no data is available directly over the epicenter. Using the InSAR data along two descending and one ascending tracks, we perform a gridded search for the optimal source parameters of the earthquake. The deformation pattern is modeled assuming uniform slip on an elastic dislocation. Since the highland regions are discontinuous, the coherent InSAR phase is isolated to several individual patches. For each iteration of the gridded search algorithm, we optimize the fit to the data by solving for number of 2π phase cycles between coherent patches and the orbital gradient across each interferogram. Since the look angle varies across a SAR scene, a variable unit vector is calculated for each track. Inversion results place the center of the fault plane at 70.33° E/23.42° N at a depth of 21 km, and are consistent with the strike and dip suggested by the relocated aftershocks. The data also constrain the magnitude, rake, and finiteness of the event.

Source process and tectonic implication of the January 20, 2007 Odaesan earthquake, South Korea

NASA Astrophysics Data System (ADS)

Abdel-Fattah, Ali K.; Kim, K. Y.; Fnais, M. S.; Al-Amri, A. M.

2014-04-01

The source process for the 20th of January 2007, Mw 4.5 Odaesan earthquake in South Korea is investigated in the low- and high-frequency bands, using velocity and acceleration waveform data recorded by the Korea Meteorological Administration Seismographic Network at distances less than 70 km from the epicenter. Synthetic Green functions are adopted for the low-frequency band of 0.1-0.3 Hz by using the wave-number integration technique and the one dimensional velocity model beneath the epicentral area. An iterative technique was performed by a grid search across the strike, dip, rake, and focal depth of rupture nucleation parameters to find the best-fit double-couple mechanism. To resolve the nodal plane ambiguity, the spatiotemporal slip distribution on the fault surface was recovered using a non-negative least-square algorithm for each set of the grid-searched parameters. The focal depth of 10 km was determined through the grid search for depths in the range of 6-14 km. The best-fit double-couple mechanism obtained from the finite-source model indicates a vertical strike-slip faulting mechanism. The NW faulting plane gives comparatively smaller root-mean-squares (RMS) error than its auxiliary plane. Slip pattern event provides simple source process due to the effect of Low-frequency that acted as a point source model. Three empirical Green functions are adopted to investigate the source process in the high-frequency band. A set of slip models was recovered on both nodal planes of the focal mechanism with various rupture velocities in the range of 2.0-4.0 km/s. Although there is a small difference between the RMS errors produced by the two orthogonal nodal planes, the SW dipping plane gives a smaller RMS error than its auxiliary plane. The slip distribution is relatively assessable by the oblique pattern recovered around the hypocenter in the high-frequency analysis; indicating a complex rupture scenario for such moderate-sized earthquake, similar to those reported for large earthquakes.

A formulation of directivity for earthquake sources using isochrone theory

USGS Publications Warehouse

Spudich, Paul; Chiou, Brian S.J.; Graves, Robert; Collins, Nancy; Somerville, Paul

2004-01-01

A functional form for directivity effects can be derived from isochrone theory, in which the measure of the directivity-induced amplification of an S body wave is c, the isochrone velocity. Ground displacement of the near-, intermediate-, and far-field terms of P and S waves is linear in isochrone velocity for a finite source in a whole space. We have developed an approximation c-tilde-prime of isochrone velocity that can easily be implemented as a predictor of directivity effects in empirical ground motion prediction relations. Typically, for a given fault surface, hypocenter, and site geometry, c-tilde-prime is a simple function of the hypocentral distance, the rupture distance, the crustal shear wave speed in the seismogenic zone, and the rupture velocity. c-tilde-prime typically ranges in the interval 0.44, for rupture away from the station, to about 4, for rupture toward the station. In this version of the theory directivity is independent of period. Additionally, we have created another functional form which is c-tilde-prime modified to include the approximate radiation pattern of a finite fault having a given rake. This functional form can be used to model the spatial variations of fault-parallel and fault-normal horizontal ground motions. The strengths of this formulation are 1) the proposed functional form is based on theory, 2) the predictor is unambiguously defined for all possible site locations and source rakes, and 3) it can easily be implemented for well-studied important previous earthquakes. We compare predictions of our functional form with synthetic ground motions calculated for finite strike-slip and dip-slip faults in the magnitude range 6.5 - 7.5. In general our functional form correlates best with computed fault-normal and fault-parallel motions in the synthetic motions calculated for events with M6.5. Correlation degrades but is still useful for larger events and for the geometric average horizontal motions. We have had limited success applying it to geometrically complicated faults.

Spatial Foundations of Science Education: The Illustrative Case of Instruction on Introductory Geological Concepts

ERIC Educational Resources Information Center

Liben, Lynn S.; Kastens, Kim A.; Christensen, Adam E.

2011-01-01

To study the role of spatial concepts in science learning, 125 college students with high, medium, or low scores on a horizontality (water-level) spatial task were given information about geological strike and dip using existing educational materials. Participants mapped an outcrop's strike and dip, a rod's orientation, pointed to a distant…

Geodetic constraints on the 2014 M 6.0 South Napa earthquake

USGS Publications Warehouse

Barnhart, William D.; Murray, Jessica R.; Yun, S H; Svarc, Jerry L.; Samsonov, SV; Fielding, EJ; Brooks, Benjamin A.; Milillo, Pietro

2014-01-01

On 24 August 2014, the M 6.0 South Napa earthquake shook much of the San Francisco Bay area, leading to significant damage in the Napa Valley. The earthquake occurred in the vicinity of the West Napa fault (122.313° W, 38.22° N, 11.3 km), a mapped structure located between the Rodger’s Creek and Green Valley faults, with nearly pure right‐lateral strike‐slip motion (strike 157°, dip 77°, rake –169°; http://comcat.cr.usgs.gov/earthquakes/eventpage/nc72282711#summary, last accessed December 2014) (Fig. 1). The West Napa fault previously experienced an M 5 strike‐slip event in 2000 but otherwise exhibited no previous definitive evidence of historic earthquake rupture (Rodgers et al., 2008; Wesling and Hanson, 2008). Evans et al. (2012) found slip rates of ∼9.5  mm/yr along the West Napa fault, with most slip rate models for the Bay area placing higher slip rates and greater earthquake potential on the Rodger’s Creek and Green Valley faults, respectively (e.g., Savage et al., 1999; d’Alessio et al., 2005; Funning et al., 2007).

Source inversion of the 1570 Ferrara earthquake and definitive diversion of the Po River (Italy)

NASA Astrophysics Data System (ADS)

Sirovich, L.; Pettenati, F.

2015-08-01

An 11-parameter, kinematic-function (KF) model was used to retrieve the approximate geometrical and kinematic characteristics of the fault source of the 1570 Mw 5.8 Ferrara earthquake in the Po Plain, including the double-couple orientation (strike angle 127 ± 16°, dip 28 ± 7°, and rake 77 ± 16°). These results are compatible with either the outermost thrust fronts of the northern Apennines, which are buried beneath the Po Plain's alluvial deposits, or the blind crustal-scale thrust. The 1570 event developed to the ENE of the two main shocks on 20 May 2012 (M 6.1) and 29 May 2012 (M 5.9). The three earthquakes had similar kinematics and are found 20-30 km from each other en echelon in the buried chain. Geomorphological and historical evidence exist which suggest the following: (i) the long-lasting uplift of the buried Apenninic front shifted the central part of the course of the Po River approximately 20 km northward in historical times and (ii) the 1570 earthquake marked the definitive diversion of the final part of the Po River away from Ferrara and the closure of the Po delta 40 km south of its present position.

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helmberger, Donald V.; Tromp, Jeroen; Rodgers, Arthur J.

Earthquake source parameters underpin several aspects of nuclear explosion monitoring. Such aspects are: calibration of moment magnitudes (including coda magnitudes) and magnitude and distance amplitude corrections (MDAC); source depths; discrimination by isotropic moment tensor components; and waveform modeling for structure (including waveform tomography). This project seeks to improve methods for and broaden the applicability of estimating source parameters from broadband waveforms using the Cut-and-Paste (CAP) methodology. The CAP method uses a library of Green’s functions for a one-dimensional (1D, depth-varying) seismic velocity model. The method separates the main arrivals of the regional waveform into 5 windows: Pnl (vertical and radialmore » components), Rayleigh (vertical and radial components) and Love (transverse component). Source parameters are estimated by grid search over strike, dip, rake and depth and seismic moment or equivalently moment magnitude, MW, are adjusted to fit the amplitudes. Key to the CAP method is allowing the synthetic seismograms to shift in time relative to the data in order to account for path-propagation errors (delays) in the 1D seismic velocity model used to compute the Green’s functions. The CAP method has been shown to improve estimates of source parameters, especially when delay and amplitude biases are calibrated using high signal-to-noise data from moderate earthquakes, CAP+.« less

Rupture distribution of the 1977 western Argentina earthquake

USGS Publications Warehouse

Langer, C.J.; Hartzell, S.

1996-01-01

Teleseismic P and SH body waves are used in a finite-fault, waveform inversion for the rupture history of the 23 November 1977 western Argentina earthquake. This double event consists of a smaller foreshock (M0 = 5.3 ?? 1026 dyn-cm) followed about 20 s later by a larger main shock (M0 = 1.5 ?? 1027 dyn-cm). Our analysis indicates that these two events occurred on different fault segments: with the foreshock having a strike, dip, and average rake of 345??, 45??E, and 50??, and the main shock 10??, 45??E, and 80??, respectively. The foreshock initiated at a depth of 17 km and propagated updip and to the north. The main shock initiated at the southern end of the foreshock zone at a depth of 25 to 30 km, and propagated updip and unilaterally to the south. The north-south separation of the centroids of the moment release for the foreshock and main shock is about 60 km. The apparent triggering of the main shock by the foreshock is similar to other earthquakes that have involved the failure of multiple fault segments, such as the 1992 Landers, California, earthquake. Such occurrences argue against the use of individual, mapped, surface fault or fault-segment lengths in the determination of the size and frequency of future earthquakes.

Seismic source characteristics of the intraslab 2017 Chiapas-Mexico earthquake (Mw8.2)

NASA Astrophysics Data System (ADS)

Jiménez, César

2018-07-01

Inversion of the parameters characterising the seismic source of the instraslab 2017 Chiapas Mexico earthquake (Mw 8.2) shows a simple rupture process with a unidirectional propagation and directivity towards the North-West and a duration of the rupture process around 75 s. The initial point source values of strike, dip and rake are 316°, 80° and -91° respectively. The focal mechanism indicates a normal fault type within the oceanic Cocos plate, with an almost vertical fault plane for a focal depth of 59 km. The seismic data was obtained from 51 seismic stations of the global seismic network IRIS for the epicentral distances between 30° and 90°. In the finite-fault inversion, 75 seismic signals between P and SH waves were used. The epicenter is on the southeast margin of the large slip zone which extends 75 km to the northwest, this large slip zone is located to the south of the city of Arriaga. The scalar seismic moment was estimated at 2.55 ×1021Nm , equivalent to a moment magnitude of Mw 8.2. The maximum dislocation or slip is 14.5 m. As a coseismic effect, a local tsunami was generated, recorded by several tidal gauges and offshore buoys. The deformation pattern shows a coastal uplift and subsidence.

Structural controls of the Tuscarora geothermal field, Elko County, Nevada

NASA Astrophysics Data System (ADS)

Dering, G.; Faulds, J. E.

2012-12-01

Tuscarora is an amagmatic geothermal system located ~90 km northwest of Elko, Nevada, in the northern part of the Basin and Range province ~15 km southeast of the Snake River Plain. Detailed geologic mapping, structural analysis, and well data have been integrated to identify the structural controls of the Tuscarora geothermal system. The structural framework of the geothermal field is defined by NNW- to NNE-striking normal faults that are approximately orthogonal to the present extension direction. Boiling springs, fumaroles, and siliceous sinter emanate from a single NNE-striking, west-dipping normal fault. Normal faults west of these hydrothermal features mostly dip steeply east, whereas normal faults east of the springs primarily dip west. Thus, the springs, fumaroles, and sinter straddle a zone of interaction between fault sets that dip toward each other, classified as a strike-parallel anticlinal accommodation zone. Faults within the geothermal area are mostly discontinuous along strike with offsets of tens to hundreds of meters, whereas the adjacent range-bounding fault systems of the Bull Run and Independence Mountains accommodate several kilometers of displacement. The geothermal field lies within a broad step over between the southward terminating west-dipping Bull Run fault zone and the northward terminating west-dipping Independence Mountains fault zone. Neither of these major fault zones is known to host high temperature geothermal systems. The accommodation zone lies within the broad step over and contains both east-dipping antithetic and west-dipping synthetic faults. Accommodation zones are relatively common structural components of extended terranes that transfer strain between oppositely dipping fault sets via a network of subsidiary normal faults. This study has identified the hinge zone of an anticlinal accommodation zone as the site most conducive to fluid up-flow. The recognition of this specific portion of an accommodation zone as a favorable structural setting for geothermal activity may be a useful exploration tool for development of drilling targets in extensional terranes, as well as for developing geologic models of known geothermal fields. This type of information may ultimately help to reduce the risks of targeting successful geothermal wells in such settings.

Static stress changes associated with normal faulting earthquakes in South Balkan area

NASA Astrophysics Data System (ADS)

Papadimitriou, E.; Karakostas, V.; Tranos, M.; Ranguelov, B.; Gospodinov, D.

2007-10-01

Activation of major faults in Bulgaria and northern Greece presents significant seismic hazard because of their proximity to populated centers. The long recurrence intervals, of the order of several hundred years as suggested by previous investigations, imply that the twentieth century activation along the southern boundary of the sub-Balkan graben system, is probably associated with stress transfer among neighbouring faults or fault segments. Fault interaction is investigated through elastic stress transfer among strong main shocks ( M ≥ 6.0), and in three cases their foreshocks, which ruptured distinct or adjacent normal fault segments. We compute stress perturbations caused by earthquake dislocations in a homogeneous half-space. The stress change calculations were performed for faults of strike, dip, and rake appropriate to the strong events. We explore the interaction between normal faults in the study area by resolving changes of Coulomb failure function ( ΔCFF) since 1904 and hence the evolution of the stress field in the area during the last 100 years. Coulomb stress changes were calculated assuming that earthquakes can be modeled as static dislocations in an elastic half-space, and taking into account both the coseismic slip in strong earthquakes and the slow tectonic stress buildup associated with major fault segments. We evaluate if these stress changes brought a given strong earthquake closer to, or sent it farther from, failure. Our modeling results show that the generation of each strong event enhanced the Coulomb stress on along-strike neighbors and reduced the stress on parallel normal faults. We extend the stress calculations up to present and provide an assessment for future seismic hazard by identifying possible sites of impending strong earthquakes.

Strike action electromagnetic machine for immersion of rod elements into ground

NASA Astrophysics Data System (ADS)

Usanov, K. M.; Volgin, A. V.; Chetverikov, E. A.; Kargin, V. A.; Moiseev, A. P.; Ivanova, Z. I.

2017-10-01

During construction, survey work, and drilling shallow wells by striking, operations associated with dipping and removing the rod elements are the most common. At the same time relatively long, with small diameter, elements, in which the ratio of length to diameter l/d is 100 or more, constitute a significant proportion. At present, the application of power pulse linear electromagnetic motors to drive drum machines is recognized to be highly effective. However, the mechanical method of transmission of shocks does not allow dipping long longitudinally unstable core elements. In this case, mechanical energy must be transferred from the motor to the rod through its side surface. The design of the strike action electromagnetic machine with a through axial channel for non-mechanical end striking of the pile of long, longitudinally unstable metal rods is proposed. Electromagnetic striking machine for non-mechanical end striking rod elements provides operations characterized by ecological compatibility, safety and high quality.

Sub-volcanic slope influencing the development of major structures at volcanoes during strike-slip faulting

NASA Astrophysics Data System (ADS)

Andrade, Daniel; van Wyk de Vries, Benjamin; Robin, Claude

2014-05-01

Volcano-basement interactions can deeply determine the structural development of volcanoes basically by the propagation of stress and strain fields from the basement into the volcanic edifice, and vice versa. An extensively studied case of such interactions is the propagation of a strike-slip fault through a volcanic edifice, which gives place to a strong tendency of major volcanic construction and destruction events to occur in a sub-parallel trend with respect to the strike of the fault. During precedent studies, however, both scaled and natural prototypes have always considered that the surfaces on which volcanoes stand (i.e. the sub-volcanic slope) are horizontal. The scaled experiments presented here show that the dip-angle and dip-direction of the subvolcanic slopes can systematically and significantly change the deformation patterns developed by the volcanic edifice during strike-slip faulting. When the dip-direction of the sub-volcanic slope and the strike of the fault are nearly parallel, an increased development and concentration of the deformation on the down-slope side of the volcanic cone occurs. In medium to long-term, this would imply again a tendency of major volcanic structures growing in a sub-parallel trend with respect to the strike of the fault, but with one preferred direction: that of the dip-direction. In the experiments, the dip-direction of the sub-volcanic slope was set progressively oblique, up to perpendicular, with respect to the strike of the fault by: 1) rotating in the same sense as the strike-slip fault, or 2) rotating in the opposite sense as the fault. In both cases, the downslope side of the volcanic cone still concentrates the deformation, but the deformed sectors progressively rotate which results in a structural development (construction and destruction) of the edifice occurring clearly oblique with respect to the strike of the fault. Imbabura volcano (Ecuador) is traversed by the strike-slip El Angel-Río Ambi fault, whose sense of movement (left- or right-lateral) has not been clearly established yet. Aditionally, Imbabura has been constructed on the NW, medium to lower flank of the neighbor Cubilche volcano. The application of the experimental results presented above to the case of Imbabura volcano helps to understand the particular structure of this volcano which displays a complex history of construction and destruction events. Additionally, the experiments strongly suggests that the El Angel-Río Ambi fault is left-lateral.

The regional structural setting of the 2008 Wells earthquake and Town Creek Flat Basin: implications for the Wells earthquake fault and adjacent structures

USGS Publications Warehouse

Henry, Christopher S.; Colgan, Joseph P.

2011-01-01

The 2008 Wells earthquake occurred on a northeast-striking, southeast-dipping fault that is clearly delineated by the aftershock swarm to a depth of 10-12 km below sea level. However, Cenozoic rocks and structures around Wells primarily record east-west extension along north- to north-northeast-striking, west-dipping normal faults that formed during the middle Miocene. These faults are responsible for the strong eastward tilt of most basins and ranges in the area, including the Town Creek Flat basin (the location of the earthquake) and the adjacent Snake Mountains and western Windermere Hills. These older west-dipping faults are locally overprinted by a younger generation of east-dipping, high-angle normal faults that formed as early as the late Miocene and have remained active into the Quaternary. The most prominent of these east-dipping faults is the set of en-échelon, north-striking faults that bounds the east sides of the Ruby Mountains, East Humboldt Range, and Clover Hill (about 5 km southwest of Wells). The northeastern-most of these faults, the Clover Hill fault, projects northward along strike toward the Snake Mountains and the approximately located surface projection of the Wells earthquake fault as defined by aftershock locations. The Clover Hill fault also projects toward a previously unrecognized, east-facing Quaternary fault scarp and line of springs that appear to mark a significant east-dipping normal fault along the western edge of Town Creek Flat. Both western and eastern projections may be northern continuations of the Clover Hill fault. The Wells earthquake occurred along this east-dipping fault system. Two possible alternatives to rupture of a northern continuation of the Clover Hill fault are that the earthquake fault (1) is antithetic to an active west-dipping fault or (2) reactivated a Mesozoic thrust fault that dips east as a result of tilting by the west-dipping faults along the west side of the Snake Mountains. Both alternatives are precluded by the depths of the earthquake and aftershocks, about 8 km and as deep as 12 km, respectively. These depths are below where an antithetic fault would intersect any main fault, and a tilted, formerly shallow and sub-horizontal thrust fault would not extend to depths of more than about 5–6 km. The east-dipping, high-angle, earthquake fault cuts older west-dipping faults rather than reactivating them, highlighting a change in the structural style of Basin and Range extension in this region from closely-spaced, west-dipping faults that rotated significantly during slip and accommodated large-magnitude extension, to widely-spaced, high-angle faults that accommodate much less total strain over a long time span.

Simulation of Ground-Water Flow in the Shenandoah Valley, Virginia and West Virginia, Using Variable-Direction Anisotropy in Hydraulic Conductivity to Represent Bedrock Structure

USGS Publications Warehouse

Yager, Richard M.; Southworth, Scott C.; Voss, Clifford I.

2008-01-01

Ground-water flow was simulated using variable-direction anisotropy in hydraulic conductivity to represent the folded, fractured sedimentary rocks that underlie the Shenandoah Valley in Virginia and West Virginia. The anisotropy is a consequence of the orientations of fractures that provide preferential flow paths through the rock, such that the direction of maximum hydraulic conductivity is oriented within bedding planes, which generally strike N30 deg E; the direction of minimum hydraulic conductivity is perpendicular to the bedding. The finite-element model SUTRA was used to specify variable directions of the hydraulic-conductivity tensor in order to represent changes in the strike and dip of the bedding throughout the valley. The folded rocks in the valley are collectively referred to as the Massanutten synclinorium, which contains about a 5-km thick section of clastic and carbonate rocks. For the model, the bedrock was divided into four units: a 300-m thick top unit with 10 equally spaced layers through which most ground water is assumed to flow, and three lower units each containing 5 layers of increasing thickness that correspond to the three major rock units in the valley: clastic, carbonate and metamorphic rocks. A separate zone in the carbonate rocks that is overlain by colluvial gravel - called the western-toe carbonate unit - was also distinguished. Hydraulic-conductivity values were estimated through model calibration for each of the four rock units, using data from 354 wells and 23 streamflow-gaging stations. Conductivity tensors for metamorphic and western-toe carbonate rocks were assumed to be isotropic, while conductivity tensors for carbonate and clastic rocks were assumed to be anisotropic. The directions of the conductivity tensor for carbonate and clastic rocks were interpolated for each mesh element from a stack of 'form surfaces' that provided a three-dimensional representation of bedrock structure. Model simulations were run with (1) variable strike and dip, in which conductivity tensors were aligned with the strike and dip of the bedding, and (2) uniform strike in which conductivity tensors were assumed to be horizontally isotropic with the maximum conductivity direction parallel to the N30 deg E axis of the valley and the minimum conductivity direction perpendicular to the horizontal plane. Simulated flow penetrated deeper into the aquifer system with the uniform-strike tensor than with the variable-strike-and-dip tensor. Sensitivity analyses suggest that additional information on recharge rates would increase confidence in the estimated parameter values. Two applications of the model were conducted - the first, to determine depth of recent ground-water flow by simulating the distribution of ground-water ages, showed that most shallow ground water is less than 10 years old. Ground-water age distributions computed by variable-strike-and-dip and uniform-strike models were similar, but differed beneath Massanutten Mountain in the center of the valley. The variable-strike-and-dip model simulated flow from west to east parallel to the bedding of the carbonate rocks beneath Massanutten Mountain, while the uniform-strike model, in which flow was largely controlled by topography, simulated this same area as an east-west ground-water divide. The second application, which delineated capture zones for selected well fields in the valley, showed that capture zones delineated with both models were similar in plan view, but differed in vertical extent. Capture zones simulated by the variable-strike-and-dip model extended downdip with the bedding of carbonate rock and were relatively shallow, while those simulated by the uniform-strike model extended to the bottom of the flow system, which is unrealistic. These results suggest that simulations of ground-water flow through folded fractured rock can be constructed using SUTRA to represent variable orientations of the hydraulic-conductivity tensor and produce a

The 1999 Hector Mine Earthquake, Southern California: Vector Near-Field Displacements from ERS InSAR

NASA Technical Reports Server (NTRS)

Sandwell, David T.; Sichoix, Lydie; Smith, Bridget

2002-01-01

Two components of fault slip are uniquely determined from two line-of-sight (LOS) radar interferograms by assuming that the fault-normal component of displacement is zero. We use this approach with ascending and descending interferograms from the ERS satellites to estimate surface slip along the Hector Mine earthquake rupture. The LOS displacement is determined by visually counting fringes to within 1 km of the outboard ruptures. These LOS estimates and uncertainties are then transformed into strike- and dip-slip estimates and uncertainties; the transformation is singular for a N-S oriented fault and optimal for an E-W oriented fault. In contrast to our previous strike-slip estimates, which were based only on a descending interferogram, we now find good agreement with the geological measurements, except at the ends of the rupture. The ascending interferogram reveals significant west-sidedown dip-slip (approximately 1.0 m) which reduces the strike-slip estimates by 1 to 2 m, especially along the northern half of the rupture. A spike in the strike-slip displacement of 6 m is observed in central part of the rupture. This large offset is confirmed by subpixel cross correlation of features in the before and after amplitude images. In addition to strike slip and dip slip, we identify uplift and subsidence along the fault, related to the restraining and releasing bends in the fault trace, respectively. Our main conclusion is that at least two look directions are required for accurate estimates of surface slip even along a pure strike-slip fault. Models and results based only on a single look direction could have major errors. Our new estimates of strike slip and dip slip along the rupture provide a boundary condition for dislocation modeling. A simple model, which has uniform slip to a depth of 12 km, shows good agreement with the observed ascending and descending interferograms.

Source parameters and moment tensor of the ML 4.6 earthquake of November 19, 2011, southwest Sharm El-Sheikh, Egypt

NASA Astrophysics Data System (ADS)

Mohamed, Gad-Elkareem Abdrabou; Omar, Khaled

2014-06-01

The southern part of the Gulf of Suez is one of the most seismically active areas in Egypt. On Saturday November 19, 2011 at 07:12:15 (GMT) an earthquake of ML 4.6 occurred in southwest Sharm El-Sheikh, Egypt. The quake has been felt at Sharm El-Sheikh city while no casualties were reported. The instrumental epicenter is located at 27.69°N and 34.06°E. Seismic moment is 1.47 E+22 dyne cm, corresponding to a moment magnitude Mw 4.1. Following a Brune model, the source radius is 101.36 m with an average dislocation of 0.015 cm and a 0.06 MPa stress drop. The source mechanism from a fault plane solution shows a normal fault, the actual fault plane is strike 358, dip 34 and rake -60, the computer code ISOLA is used. Twenty seven small and micro earthquakes (1.5 ⩽ ML ⩽ 4.2) were also recorded by the Egyptian National Seismological Network (ENSN) from the same region. We estimate the source parameters for these earthquakes using displacement spectra. The obtained source parameters include seismic moments of 2.77E+16-1.47E+22 dyne cm, stress drops of 0.0005-0.0617 MPa and relative displacement of 0.0001-0.0152 cm.

Determination of Love- and Rayleigh-Wave Magnitudes for Earthquakes and Explosions and Other Studies

DTIC Science & Technology

2012-12-30

the dip- slip or oblique mechanisms . Figure 30. Comparison of Mw (a) and depth (b) computed using srfgrd96 program (Herrmann, 2004...example it follows from Equations A5 and A7 that the Love wave amplitudes for the strike- slip focal mechanism are greater than those for a dip- slip ...These events ranged in size between 3.2 < Mw < 5.1 with the focal mechanisms (Herrmann, pers. comm. 2010) being predominantly strike- slip

Strike-slip linked core complexes: A new kinematic model of basement rock exhumation in a crustal-scale fault system

NASA Astrophysics Data System (ADS)

Meyer, Sven Erik; Passchier, Cees; Abu-Alam, Tamer; Stüwe, Kurt

2014-05-01

Metamorphic core complexes usually develop as extensional features during continental crustal thinning, such as the Basin and Range and the Aegean Terrane. The Najd fault system in Saudi Arabia is a 2000 km-long and 400 km-wide complex network of crustal-scale strike-slip shear zones in a Neoproterozoic collision zone. Locally, the anastomosing shear zones lead to exhumation of lower crustal segments and represent a new kinematic model for the development of core complexes. We report on two such structures: the Qazaz complex in Saudi Arabia and the Hafafit complex in Egypt. The 15 km-wide Qazaz complex is a triangular dome of gently dipping mylonitic foliations within the 140 km-long sinistral strike-slip Qazaz mylonite zone. The gneissic dome consists of high-grade rocks, surrounded by low-grade metasediments and metavolcanics. The main SE-trending strike-slip Qazaz shear zone splits southwards into two branches around the gneiss dome: the western branch is continuous with the shallow dipping mylonites of the dome core, without overprinting, and changes by more than 90 degrees from a NS-trending strike-slip zone to an EW-trending 40 degree south-dipping detachment that bounds the gneiss dome to the south. The eastern SE-trending sinistral strike-slip shear zone branch is slightly younger and transects the central dome fabrics. The gneiss dome appears to have formed along a jog in the strike-slip shear zone during 40 km of horizontal strike-slip motion, which caused local exhumation of lower crustal rocks by 25 km along the detachment. The eastern shear zone branch formed later during exhumation, transacted the gneiss dome and offset the two parts by another 70 km. The Hafafit core complex in Egypt is of similar shape and size to the Qazaz structure, but forms the northern termination of a sinistral strike-slip zone that is at least 100 km in length. This zone may continue into Saudi Arabia as the Ajjaj shear zone for another 100 km. The NW trending strike slip mylonite zone grades into a gently N-dipping detachment to the west which accommodated strike slip by exhumation of high-grade lower crustal rocks. The Qazaz and the Hafafit Domes are similar, mirror-image structures with small differences in the accommodating shear zones. It is likely that these types of strike-slip related oblique core complexes are common in the Arabian Nubian shield, and possibly elsewhere.

Evidence for slip partitioning and bimodal slip behavior on a single fault: Surface slip characteristics of the 2013 Mw7.7 Balochistan, Pakistan earthquake

USGS Publications Warehouse

Barnhart, William; Briggs, Richard; Reitman, Nadine G.; Gold, Ryan D.; Hayes, Gavin

2015-01-01

Deformation is commonly accommodated by strain partitioning on multiple, independent strike-slip and dip-slip faults in continental settings of oblique plate convergence. As a corollary, individual faults tend to exhibit one sense of slip – normal, reverse, or strike-slip – until whole-scale changes in boundary conditions reactivate preexisting faults in a new deformation regime. In this study, we show that a single continental fault may instead partition oblique strain by alternatively slipping in a strike-slip or a dip-slip sense during independent fault slip events. We use 0.5 m resolution optical imagery and sub-pixel correlation analysis of the 200+ km 200+km"> 2013 Mw7.7 Balochistan, Pakistan earthquake to document co-seismic surface slip characteristics and Quaternary tectonic geomorphology along the causative Hoshab fault. We find that the 2013 earthquake, which involved a ∼6:1 strike-slip to dip-slip ratio, ruptured a structurally segmented fault. Quaternary geomorphic indicators of gross fault-zone morphology reveal both reverse-slip and strike-slip deformation in the rupture area of the 2013 earthquake that varies systematically along fault strike despite nearly pure strike-slip motion in 2013. Observations of along-strike variations in range front relief and geomorphic offsets suggest that the Hoshab fault accommodates a substantial reverse component of fault slip in the Quaternary, especially along the southern section of the 2013 rupture. We surmise that Quaternary bimodal slip along the Hoshab fault is promoted by a combination of the arcuate geometry of the Hoshab fault, the frictional weakness of the Makran accretionary prism, and time variable loading conditions from adjacent earthquakes and plate interactions.

Evidence for slip partitioning and bimodal slip behavior on a single fault: Surface slip characteristics of the 2013 Mw7.7 Balochistan, Pakistan earthquake

NASA Astrophysics Data System (ADS)

Barnhart, W. D.; Briggs, R. W.; Reitman, N. G.; Gold, R. D.; Hayes, G. P.

2015-06-01

Deformation is commonly accommodated by strain partitioning on multiple, independent strike-slip and dip-slip faults in continental settings of oblique plate convergence. As a corollary, individual faults tend to exhibit one sense of slip - normal, reverse, or strike-slip - until whole-scale changes in boundary conditions reactivate preexisting faults in a new deformation regime. In this study, we show that a single continental fault may instead partition oblique strain by alternatively slipping in a strike-slip or a dip-slip sense during independent fault slip events. We use 0.5 m resolution optical imagery and sub-pixel correlation analysis of the 200 + km 2013 Mw7.7 Balochistan, Pakistan earthquake to document co-seismic surface slip characteristics and Quaternary tectonic geomorphology along the causative Hoshab fault. We find that the 2013 earthquake, which involved a ∼6:1 strike-slip to dip-slip ratio, ruptured a structurally segmented fault. Quaternary geomorphic indicators of gross fault-zone morphology reveal both reverse-slip and strike-slip deformation in the rupture area of the 2013 earthquake that varies systematically along fault strike despite nearly pure strike-slip motion in 2013. Observations of along-strike variations in range front relief and geomorphic offsets suggest that the Hoshab fault accommodates a substantial reverse component of fault slip in the Quaternary, especially along the southern section of the 2013 rupture. We surmise that Quaternary bimodal slip along the Hoshab fault is promoted by a combination of the arcuate geometry of the Hoshab fault, the frictional weakness of the Makran accretionary prism, and time variable loading conditions from adjacent earthquakes and plate interactions.

3D Model of the Tuscarora Geothermal Area

DOE Data Explorer

Faulds, James E.

2013-12-31

The Tuscarora geothermal system sits within a ~15 km wide left-step in a major west-dipping range-bounding normal fault system. The step over is defined by the Independence Mountains fault zone and the Bull Runs Mountains fault zone which overlap along strike. Strain is transferred between these major fault segments via and array of northerly striking normal faults with offsets of 10s to 100s of meters and strike lengths of less than 5 km. These faults within the step over are one to two orders of magnitude smaller than the range-bounding fault zones between which they reside. Faults within the broad step define an anticlinal accommodation zone wherein east-dipping faults mainly occupy western half of the accommodation zone and west-dipping faults lie in the eastern half of the accommodation zone. The 3D model of Tuscarora encompasses 70 small-offset normal faults that define the accommodation zone and a portion of the Independence Mountains fault zone, which dips beneath the geothermal field. The geothermal system resides in the axial part of the accommodation, straddling the two fault dip domains. The Tuscarora 3D geologic model consists of 10 stratigraphic units. Unconsolidated Quaternary alluvium has eroded down into bedrock units, the youngest and stratigraphically highest bedrock units are middle Miocene rhyolite and dacite flows regionally correlated with the Jarbidge Rhyolite and modeled with uniform cumulative thickness of ~350 m. Underlying these lava flows are Eocene volcanic rocks of the Big Cottonwood Canyon caldera. These units are modeled as intracaldera deposits, including domes, flows, and thick ash deposits that change in thickness and locally pinch out. The Paleozoic basement of consists metasedimenary and metavolcanic rocks, dominated by argillite, siltstone, limestone, quartzite, and metabasalt of the Schoonover and Snow Canyon Formations. Paleozoic formations are lumped in a single basement unit in the model. Fault blocks in the eastern portion of the model are tilted 5-30 degrees toward the Independence Mountains fault zone. Fault blocks in the western portion of the model are tilted toward steeply east-dipping normal faults. These opposing fault block dips define a shallow extensional anticline. Geothermal production is from 4 closely-spaced wells, that exploit a west-dipping, NNE-striking fault zone near the axial part of the accommodation zone.

Seismic moment tensor inversion using 3D velocity model and its application to the 2013 Lushan earthquake sequence

NASA Astrophysics Data System (ADS)

Zhu, Lupei; Zhou, Xiaofeng

2016-10-01

Source inversion of small-magnitude events such as aftershocks or mine collapses requires use of relatively high frequency seismic waveforms which are strongly affected by small-scale heterogeneities in the crust. In this study, we developed a new inversion method called gCAP3D for determining general moment tensor of a seismic source using Green's functions of 3D models. It inherits the advantageous features of the ;Cut-and-Paste; (CAP) method to break a full seismogram into the Pnl and surface-wave segments and to allow time shift between observed and predicted waveforms. It uses grid search for 5 source parameters (relative strengths of the isotropic and compensated-linear-vector-dipole components and the strike, dip, and rake of the double-couple component) that minimize the waveform misfit. The scalar moment is estimated using the ratio of L2 norms of the data and synthetics. Focal depth can also be determined by repeating the inversion at different depths. We applied gCAP3D to the 2013 Ms 7.0 Lushan earthquake and its aftershocks using a 3D crustal-upper mantle velocity model derived from ambient noise tomography in the region. We first relocated the events using the double-difference method. We then used the finite-differences method and reciprocity principle to calculate Green's functions of the 3D model for 20 permanent broadband seismic stations within 200 km from the source region. We obtained moment tensors of the mainshock and 74 aftershocks ranging from Mw 5.2 to 3.4. The results show that the Lushan earthquake is a reverse faulting at a depth of 13-15 km on a plane dipping 40-47° to N46° W. Most of the aftershocks occurred off the main rupture plane and have similar focal mechanisms to the mainshock's, except in the proximity of the mainshock where the aftershocks' focal mechanisms display some variations.

Broadband Rupture Process of the 2001 Kunlun Fault (Mw 7.8) Earthquake

NASA Astrophysics Data System (ADS)

Antolik, M.; Abercrombie, R.; Ekstrom, G.

2003-04-01

We model the source process of the 14 November, 2001 Kunlun fault earthquake using broadband body waves from the Global Digital Seismographic Network (P, SH) and both point-source and distributed slip techniques. The point-source mechanism technique is a non-linear iterative inversion that solves for focal mechanism, moment rate function, depth, and rupture directivity. The P waves reveal a complex rupture process for the first 30 s, with smooth unilateral rupture toward the east along the Kunlun fault accounting for the remainder of the 120 s long rupture. The obtained focal mechanism for the main portion of the rupture is (strike=96o, dip=83o, rake=-8o) which is consistent with both the Harvard CMT solution and observations of the surface rupture. The seismic moment is 5.29×1020 Nm and the average rupture velocity is ˜3.5 km/s. However, the initial portion of the P waves cannot be fit at all with this mechanism. A strong pulse visible in the first 20 s can only be matched with an oblique-slip subevent (MW ˜ 6.8-7.0) involving a substantial normal faulting component, but the nodal planes of this mechanism are not well constrained. The first-motion polarities of the P waves clearly require a strike mechanism with a similar orientation as the Kunlun fault. Field observations of the surface rupture (Xu et al., SRL, 73, No. 6) reveal a small 26 km-long strike-slip rupture at the far western end (90.5o E) with a 45-km long gap and extensional step-over between this rupture and the main Kunlun fault rupture. We hypothesize that the initial fault break occurred on this segment, with release of the normal faulting energy as a continuous rupture through the extensional step, enabling transfer of the slip to the main Kunlun fault. This process is similar to that which occurred during the 2002 Denali fault (MW 7.9) earthquake sequence except that 11 days elapsed between the October 23 (M_W 6.7) foreshock and the initial break of the Denali earthquake along a thrust fault.

Open-Water Resistance and Seakeeping Characteristics of Ships with Icebreaking Bows

DTIC Science & Technology

1991-05-13

of a Knuckled Forefoot on a Typical Icebreaker ...... ................... . 19 3-2. Lines Plan, T-AGS OCEAN (ICE) . * * .... . 23 3-3. Curve of...the ice. As the stem strikes the ice, initial failure of the ice occurs by simple crushing. Then the raked stem of the icebreaker rides up onto the ice...bossings, skegs, rudders, 18 and special stem forefoot shapes were not included in the shapes tested. To ensure that the parent and its variants

Folding associated with extensional faulting: Sheep Range detachment, southern Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guth, P.L.

1985-01-01

The Sheep Range detachment is a major Miocene extensional fault system of the Great Basin. Its major faults have a scoop shape, with straight, N-S traces extending 15-30 km and then abruptly turning to strike E-W. Tertiary deformation involved simultaneous normal faulting, sedimentation, landsliding, and strike-slip faulting. Folds occur in two settings: landslide blocks and drag along major faults. Folds occur in landslide blocks and beneath them. Most folds within landslide blocks are tight anticlines, with limbs dipping 40-60 degrees. Brecciation of the folds and landslide blocks suggests brittle deformation. Near Quijinump Canyon in the Sheep Range, at least threemore » landslide blocks (up to 500 by 1500 m) slid into a small Tertiary basin. Tertiary limestone beneath the Paleozoic blocks was isoclinally folded. Westward dips reveal drag folds along major normal faults, as regional dips are consistently to the east. The Chowderhead anticline is the largest drag fold, along an extensional fault that offsets Ordovician units 8 km. East-dipping Ordovician and Silurian rocks in the Desert Range form the hanging wall. East-dipping Cambrian and Ordovician units in the East Desert Range form the foot wall and east limb of the anticline. Caught along the fault plane, the anticline's west-dipping west limb contains mostly Cambrian units.« less

Geoelectric Characterization of Thermal Water Aquifers Using 2.5D Inversion of VES Measurements

NASA Astrophysics Data System (ADS)

Gyulai, Á.; Szűcs, P.; Turai, E.; Baracza, M. K.; Fejes, Z.

2017-03-01

This paper presents a short theoretical summary of the series expansion-based 2.5D combined geoelectric weighted inversion (CGWI) method and highlights the advantageous way with which the number of unknowns can be decreased due to the simultaneous characteristic of this inversion. 2.5D CGWI is an approximate inversion method for the determination of 3D structures, which uses the joint 2D forward modeling of dip and strike direction data. In the inversion procedure, the Steiner's most frequent value method is applied to the automatic separation of dip and strike direction data and outliers. The workflow of inversion and its practical application are presented in the study. For conventional vertical electrical sounding (VES) measurements, this method can determine the parameters of complex structures more accurately than the single inversion method. Field data show that the 2.5D CGWI which was developed can determine the optimal location for drilling an exploratory thermal water prospecting well. The novelty of this research is that the measured VES data in dip and strike direction are jointly inverted by the 2.5D CGWI method.

Modeling 3D Dynamic Rupture on Arbitrarily-Shaped faults by Boundary-Conforming Finite Difference Method

NASA Astrophysics Data System (ADS)

Zhu, D.; Zhu, H.; Luo, Y.; Chen, X.

2008-12-01

We use a new finite difference method (FDM) and the slip-weakening law to model the rupture dynamics of a non-planar fault embedded in a 3-D elastic media with free surface. The new FDM, based on boundary- conforming grid, sets up the mapping equations between the curvilinear coordinate and the Cartesian coordinate and transforms irregular physical space to regular computational space; it also employs a higher- order non-staggered DRP/opt MacCormack scheme which is of low dispersion and low dissipation so that the high accuracy and stability of our rupture modeling are guaranteed. Compared with the previous methods, not only we can compute the spontaneous rupture of an arbitrarily shaped fault, but also can model the influence of the surface topography on the rupture process of earthquake. In order to verify the feasibility of this method, we compared our results and other previous results, and found out they matched perfectly. Thanks to the boundary-conforming FDM, problems such as dynamic rupture with arbitrary dip, strike and rake over an arbitrary curved plane can be handled; and supershear or subshear rupture can be simulated with different parameters such as the initial stresses and the critical slip displacement Dc. Besides, our rupture modeling is economical to be implemented owing to its high efficiency and does not suffer from displacement leakage. With the help of inversion data of rupture by field observations, this method is convenient to model rupture processes and seismograms of natural earthquakes.

Micro-seismic waveform matching inversion based on gravitational search algorithm and parallel computation

NASA Astrophysics Data System (ADS)

Jiang, Y.; Xing, H. L.

2016-12-01

Micro-seismic events induced by water injection, mining activity or oil/gas extraction are quite informative, the interpretation of which can be applied for the reconstruction of underground stress and monitoring of hydraulic fracturing progress in oil/gas reservoirs. The source characterises and locations are crucial parameters that required for these purposes, which can be obtained through the waveform matching inversion (WMI) method. Therefore it is imperative to develop a WMI algorithm with high accuracy and convergence speed. Heuristic algorithm, as a category of nonlinear method, possesses a very high convergence speed and good capacity to overcome local minimal values, and has been well applied for many areas (e.g. image processing, artificial intelligence). However, its effectiveness for micro-seismic WMI is still poorly investigated; very few literatures exits that addressing this subject. In this research an advanced heuristic algorithm, gravitational search algorithm (GSA) , is proposed to estimate the focal mechanism (angle of strike, dip and rake) and source locations in three dimension. Unlike traditional inversion methods, the heuristic algorithm inversion does not require the approximation of green function. The method directly interacts with a CPU parallelized finite difference forward modelling engine, and updating the model parameters under GSA criterions. The effectiveness of this method is tested with synthetic data form a multi-layered elastic model; the results indicate GSA can be well applied on WMI and has its unique advantages. Keywords: Micro-seismicity, Waveform matching inversion, gravitational search algorithm, parallel computation

Tsunami simulations of the 1867 Virgin Island earthquake: Constraints on epicenter location and fault parameters

USGS Publications Warehouse

Barkan, Roy; ten Brink, Uri S.

2010-01-01

The 18 November 1867 Virgin Island earthquake and the tsunami that closely followed caused considerable loss of life and damage in several places in the northeast Caribbean region. The earthquake was likely a manifestation of the complex tectonic deformation of the Anegada Passage, which cuts across the Antilles island arc between the Virgin Islands and the Lesser Antilles. In this article, we attempt to characterize the 1867 earthquake with respect to fault orientation, rake, dip, fault dimensions, and first tsunami wave propagating phase, using tsunami simulations that employ high-resolution multibeam bathymetry. In addition, we present new geophysical and geological observations from the region of the suggested earthquake source. Results of our tsunami simulations based on relative amplitude comparison limit the earthquake source to be along the northern wall of the Virgin Islands basin, as suggested by Reid and Taber (1920), or on the carbonate platform north of the basin, and not in the Virgin Islands basin, as commonly assumed. The numerical simulations suggest the 1867 fault was striking 120°–135° and had a mixed normal and left-lateral motion. First propagating wave phase analysis suggests a fault striking 300°–315° is also possible. The best-fitting rupture length was found to be relatively small (50 km), probably indicating the earthquake had a moment magnitude of ∼7.2. Detailed multibeam echo sounder surveys of the Anegada Passage bathymetry between St. Croix and St. Thomas reveal a scarp, which cuts the northern wall of the Virgin Islands basin. High-resolution seismic profiles further indicate it to be a reasonable fault candidate. However, the fault orientation and the orientation of other subparallel faults in the area are more compatible with right-lateral motion. For the other possible source region, no clear disruption in the bathymetry or seismic profiles was found on the carbonate platform north of the basin.

Effects induced by an earthquake on its fault plane:a boundary element study

NASA Astrophysics Data System (ADS)

Bonafede, Maurizio; Neri, Andrea

2000-04-01

Mechanical effects left by a model earthquake on its fault plane, in the post-seismic phase, are investigated employing the `displacement discontinuity method'. Simple crack models, characterized by the release of a constant, unidirectional shear traction are investigated first. Both slip components-parallel and normal to the traction direction-are found to be non-vanishing and to depend on fault depth, dip, aspect ratio and fault plane geometry. The rake of the slip vector is similarly found to depend on depth and dip. The fault plane is found to suffer some small rotation and bending, which may be responsible for the indentation of a transform tectonic margin, particularly if cumulative effects are considered. Very significant normal stress components are left over the shallow portion of the fault surface after an earthquake: these are tensile for thrust faults, compressive for normal faults and are typically comparable in size to the stress drop. These normal stresses can easily be computed for more realistic seismic source models, in which a variable slip is assigned; normal stresses are induced in these cases too, and positive shear stresses may even be induced on the fault plane in regions of high slip gradient. Several observations can be explained from the present model: low-dip thrust faults and high-dip normal faults are found to be facilitated, according to the Coulomb failure criterion, in repetitive earthquake cycles; the shape of dip-slip faults near the surface is predicted to be upward-concave; and the shallower aftershock activity generally found in the hanging block of a thrust event can be explained by `unclamping' mechanisms.

Phanerozoic strike-slip faulting in the continental interior platform of the United States: Examples from the Laramide Orogen, midcontinent, and Ancestral Rocky Mountains

USGS Publications Warehouse

Marshak, S.; Nelson, W.J.; McBride, J.H.

2003-01-01

The continental interior platform of the United States is that part of the North American craton where a thin veneer of Phanerozoic strata covers Precambrian crystalline basement. N- to NE-trending and W- to NW-trending fault zones, formed initially by Proterozoic/Cambrian rifting, break the crust of the platform into rectilinear blocks. These zones were reactivated during the Phanerozoic, most notably in the late Palaeozoic Ancestral Rockies event and the Mesozoic-Cenozoic Laramide orogeny - some remain active today. Dip-slip reactivation can be readily recognized in cross section by offset stratigraphic horizons and monoclinal fault-propagation folds. Strike-slip displacement is hard to document because of poor exposure. Through offset palaeochannels, horizontal slip lineations, and strain at fault bends locally demonstrate strike-slip offset, most reports of strike-slip movements for interior-platform faults are based on occurrence of map-view belts of en echelon faults and anticlines. Each belt overlies a basement-penetrating master fault, which typically splays upwards into a flower structure. In general, both strike-slip and dip-slip components of displacement occur in the same fault zone, so some belts of en echelon structures occur on the flanks of monoclinal folds. Thus, strike-slip displacement represents the lateral components of oblique fault reactivation: dip-slip and strike-slip components are the same order of magnitude (tens of metres to tens of kilometres). Effectively, faults with strike-slip components of displacement act as transfers accommodating jostling of rectilinear crustal blocks. In this context, the sense of slip on an individual strike-slip fault depends on block geometry, not necessarily on the trajectory of regional ??1. Strike-slip faulting in the North American interior differs markedly from that of southern and central Eurasia, possibly because of a contrast in lithosphere strength. Weak Eurasia strained significantly during the Alpine-Himalayan collision, forcing crustal blocks to undergo significant lateral escape. The strong North American craton strained relatively little during collisional-convergent orogeny, so crustal blocks underwent relatively small displacements.

The geology and ore deposits of Upper Mayflower Gulch, Summit County, Colorado

USGS Publications Warehouse

Randall, John Alexander

1958-01-01

Upper Mayflower Gulch is on the highly glaciated western side of the Tenmile Range near Kokomo in central Colorado. Somewhat less than $500,000 in silver and gold has been produced from the area since the first mining in the 1880' s. In the mapped area high grade regional metamorphism has produced two varieties of gneiss and a granulite. Total thickness of the rocks is about 5,000 feet. Relict bedding is preserved in compositional banding which strikes north to N. 20 ? E. and dips 70 ? to 80 ? southeast. No significant folding was observed. Normal faulting has occurred since the Precambrian; two major sets of faults are recognizable: (1) a set striking N. 70 ? to 85 ? E. and dipping 75?-85 ? NW; and (2) a set striking N. 70?-50 ? W. and dipping 50?-60 ? SW. Tabular bodies of pegmatite and retrogressively metamorphosed schist along many faults indicate Precambrian movement. The Mayflower fault, a 90 to 300 foot wide zone of siltification and shattered rock, strikes about N. 40 ? W. It extends the entire length of the gulch and appears to form the northern terminus for the northeast trending Mosquito Fault. The Mayflower fault shows repeated movement since the Precambrian, totaling about 3,000 feet of apparent dip slip and 640 feet of apparent strike slip. Faulting during the Tertiary includes both additional movement along Precambrian faults and development of shears trending N. to N. 20 ? E. The shears served as channels for the intrusion of two varieties of quartz latite porphyry dikes. Specular hematite and base-metal sulfide mineralization followed intrusion of the porphyry dikes; the minerals were deposited in open fault zones by high temperature solutions in a low pressure environment. The principal metallic minerals in order of deposition are: hematite, pyrite, chalcopyrite, sphalerite, galena, and rarer argentite. The major mines are the Gold Crest, Payrock, Nova Scotia Boy, and Bird's Nest.

Study on stability of rake teeth inserting soil of chain rake type mulching film recovery machine based on Adams

NASA Astrophysics Data System (ADS)

Guo, Wensong; Jian, Jianming; San, Yunlong; Lui, Rui; Li, Gang; Hou, Shulin

2017-08-01

Traditional rake type mulching film recycling machine has the problem of difficulty in unloading and packing film, poor continuity of the work. In order to solve such problems, this paper designs a kind of chain rake type mulching film recycling machine which can realize continuous raking film, collecting film, transporting film, shaking off soil, unloading film. Rake teeth is the basic part of chain rake mulching recycling machine. The stability of rake teeth's inserting soil is an important factor to ensure recovery efficiency of the plastic film recovery. By virtual prototype simulation, this paper study the influence of different factors on the stability of rake teeth inserting soil. The results are as follows: The speed of chain rake has no significant effect on the stability of rake teeth inserting soil; Reducing resistance of rake teeth in the process of working, is conducive to improve the stability of rake teeth inserting soil; Appropriate increasing elastic modulus of chain rake, is helpful to enhance the stability of rake teeth inserting soil.

Ground Surface Deformation in Unconsolidated Sediments Caused by Bedrock Fault Movements: Dip-Slip and Strike-Slip Fault Model Test and Field Survey

NASA Astrophysics Data System (ADS)

Ueta, K.; Tani, K.

2001-12-01

Sandbox experiments were performed to investigate ground surface deformation in unconsolidated sediments caused by dip-slip and strike-slip motion on bedrock faults. A 332.5 cm long, 200 cm high, and 40 cm wide sandbox was used in a dip-slip fault model test. In the strike-slip fault test, a 600 cm long, 250 cm wide, and 60 cm high sandbox and a 170 cm long, 25 cm wide, 15 cm high sandbox were used. Computerized X-ray tomography applied to the sandbox experiments made it possible to analyze the kinematic evolution, as well as the three-dimensional geometry, of the faults. The fault type, fault dip, fault displacement, thickness and density of sandpack and grain size of the sand were varied for different experiments. Field survey of active faults in Japan and California were also made to investigate the deformation of unconsolidated sediments overlying bedrock faults. A comparison of the experimental results with natural cases of active faults reveals the following: (1) In the case of dip-slip faulting, the shear bands are not shown as one linear plane but as en echelon pattern. Thicker and finer unconsolidated sediments produce more shear bands and clearer en echelon shear band patterns. (2) In the case of left-lateral strike-slip faulting, the deformation of the sand pack with increasing basement displacement is observed as follows. a) In three dimensions, the right-stepping shears that have a "cirque" / "shell" / "ship body" shape develop on both sides of the basement fault. The shears on one side of the basement fault join those on the other side, resulting in helicoidal shaped shear surfaces. Shears reach the surface of the sand near or above the basement fault and en echelon Riedel shears are observed at the surface of the sand. b) Right-stepping pressure ridges develop within the zone defined by the Riedel shears. c) Lower-angle shears generally branch off from the first Riedel shears. d) Right-stepping helicoidal shaped lower-angle shears offset Riedel shears and pressure ridges, and left-stepping and right-stepping pressure ridges are observed. d) With displacement concentrated on the central throughgoing fault zone, a "Zone of shear band" (ZSB) developed directly above the basement fault. The geometry of the ZSB shows a strong resemblance to linear ridge and trough geomorphology associated with active strike-slip faulting. (3) In the case of normal faulting, the location of the surface fault rupture is just above the bedrock faults, which have no relationship with the fault dip. On the other hand, the location of the surface rupture of the reverse fault has closely relationship with the fault dip. In the case of strike-slip faulting, the width of the deformation zone in dense sand is wider than that in loose sand. (4) The horizontal distance of surface rupture from the bedrock fault normalized by the height of sand mass (W/H) does not depend on the height of sand mass and grain size of sand. The values of W/H from the test agree well with those of earthquake faults. (5) The normalized base displacement required to propagate the shear rupture zone to the ground surface (D/H), in the case of normal faulting, is lower than those for reverse faulting and strike-slip faulting.

Electrical resistivity structure of the Great Slave Lake shear zone, northwest Canada: implications for tectonic history

NASA Astrophysics Data System (ADS)

Yin, Yaotian; Unsworth, Martyn; Liddell, Mitch; Pana, Dinu; Craven, James A.

2014-10-01

Three magnetotelluric (MT) profiles in northwestern Canada cross the central and western segments of Great Slave Lake shear zone (GSLsz), a continental scale strike-slip structure active during the Slave-Rae collision in the Proterozoic. Dimensionality analysis indicates that (i) the resistivity structure is approximately 2-D with a geoelectric strike direction close to the dominant geological strike of N45°E and that (ii) electrical anisotropy may be present in the crust beneath the two southernmost profiles. Isotropic and anisotropic 2-D inversion and isotropic 3-D inversions show different resistivity structures on different segments of the shear zone. The GSLsz is imaged as a high resistivity zone (>5000 Ω m) that is at least 20 km wide and extends to a depth of at least 50 km on the northern profile. On the southern two profiles, the resistive zone is confined to the upper crust and pierces an east-dipping crustal conductor. Inversions show that this dipping conductor may be anisotropic, likely caused by conductive materials filling a network of fractures with a preferred spatial orientation. These conductive regions would have been disrupted by strike-slip, ductile deformation on the GSLsz that formed granulite to greenschist facies mylonite belts. The pre-dominantly granulite facies mylonites are resistive and explain why the GSLsz appears as a resistive structure piercing the east-dipping anisotropic layer. The absence of a dipping anisotropic/conductive layer on the northern MT profile, located on the central segment of the GSLsz, is consistent with the lack of subduction at this location as predicted by geological and tectonic models.

3D Model of the McGinness Hills Geothermal Area

DOE Data Explorer

Faulds, James E.

2013-12-31

The McGinness Hills geothermal system lies in a ~8.5 km wide, north-northeast trending accommodation zone defined by east-dipping normal faults bounding the Toiyabe Range to the west and west-dipping normal faults bounding the Simpson Park Mountains to the east. Within this broad accommodation zone lies a fault step-over defined by north-northeast striking, west-dipping normal faults which step to the left at roughly the latitude of the McGinness Hills geothermal system. The McGinness Hills 3D model consists of 9 geologic units and 41 faults. The basal geologic units are metasediments of the Ordovician Valmy and Vininni Formations (undifferentiated in the model) which are intruded by Jurassic granitic rocks. Unconformably overlying is a ~100s m-thick section of Tertiary andesitic lava flows and four Oligocene-to-Miocene ash-flow tuffs: The Rattlesnake Canyon Tuff, tuff of Sutcliffe, the Cambell Creek Tuff and the Nine Hill tuff. Overlying are sequences of pre-to-syn-extensional Quaternary alluvium and post-extensional Quaternary alluvium. 10-15º eastward dip of the Tertiary stratigraphy is controlled by the predominant west-dipping fault set. Geothermal production comes from two west dipping normal faults in the northern limb of the step over. Injection is into west dipping faults in the southern limb of the step over. Production and injection sites are in hydrologic communication, but at a deep level, as the northwest striking fault that links the southern and northern limbs of the step-over has no permeability.

RMT focal plane sensitivity to seismic network geometry and faulting style

USGS Publications Warehouse

Johnson, Kendra L.; Hayes, Gavin; Herrmann, Robert B.; Benz, Harley M.; McNamara, Daniel E.; Bergman, Eric A.

2016-01-01

Modern tectonic studies often use regional moment tensors (RMTs) to interpret the seismotectonic framework of an earthquake or earthquake sequence; however, despite extensive use, little existing work addresses RMT parameter uncertainty. Here, we quantify how network geometry and faulting style affect RMT sensitivity. We examine how data-model fits change with fault plane geometry (strike and dip) for varying station configurations. We calculate the relative data fit for incrementally varying geometries about a best-fitting solution, applying our workflow to real and synthetic seismograms for both real and hypothetical station distributions and earthquakes. Initially, we conduct purely observational tests, computing RMTs from synthetic seismograms for hypothetical earthquakes and a series of well-behaved network geometries. We then incorporate real data and station distributions from the International Maule Aftershock Deployment (IMAD), which recorded aftershocks of the 2010 MW 8.8 Maule earthquake, and a set of regional stations capturing the ongoing earthquake sequence in Oklahoma and southern Kansas. We consider RMTs computed under three scenarios: (1) real seismic records selected for high data quality; (2) synthetic seismic records with noise computed for the observed source-station pairings and (3) synthetic seismic records with noise computed for all possible station-source pairings. To assess RMT sensitivity for each test, we observe the ‘fit falloff’, which portrays how relative fit changes when strike or dip varies incrementally; we then derive the ranges of acceptable strikes and dips by identifying the span of solutions with relative fits larger than 90 per cent of the best fit. For the azimuthally incomplete IMAD network, Scenario 3 best constrains fault geometry, with average ranges of 45° and 31° for strike and dip, respectively. In Oklahoma, Scenario 3 best constrains fault dip with an average range of 46°; however, strike is best constrained by Scenario 1, with a range of 26°. We draw two main conclusions from this study. (1) Station distribution impacts our ability to constrain RMTs using waveform time-series; however, in some tectonic settings, faulting style also plays a significant role and (2) increasing station density and data quantity (both the number of stations and the number of individual channels) does not necessarily improve RMT constraint. These results may be useful when organizing future seismic deployments (e.g. by concentrating stations in alignment with anticipated nodal planes), and in computing RMTs, either by guiding a more rigorous data selection process for input data or informing variable weighting among the selected data (e.g. by eliminating the transverse component when strike-slip mechanisms are expected).

New constraints shed light on strike-slip faulting beneath the southern Apennines (Italy): The 21 August 1962 Irpinia multiple earthquake

NASA Astrophysics Data System (ADS)

Vannoli, Paola; Bernardi, Fabrizio; Palombo, Barbara; Vannucci, Gianfranco; Console, Rodolfo; Ferrari, Graziano

2016-11-01

On 21 August 1962 an earthquake sequence set off near the city of Benevento, in Italy's southern Apennines. Three earthquakes, the largest having Mw 6.1, struck virtually the same area in less than 40 min (at 18:09, 18:19 and 18:44 UTC, respectively). Several historical earthquakes hit this region, and its seismic hazard is accordingly among the highest countrywide. Although poorly understood in the past, the seismotectonics of this region can be revealed by the 1962 sequence, being the only significant earthquake in the area for which modern seismograms are available. We determine location, magnitude, and nodal planes of the first event (18:09 UTC) of the sequence. The focal mechanism exhibits dominant strike-slip rupture along a north-dipping, E-W striking plane or along a west-dipping, N-S striking plane. Either of these solutions is significantly different from the kinematics of the typical large earthquakes occurring along the crest of the Southern Apennines, such as the 23 November 1980 Irpinia earthquake (Mw 6.9), caused by predominant normal faulting along NW-SE-striking planes. The epicentre of the 21 August 1962, 18:09 event is located immediately east of the chain axis, near one of the three north-dipping, E-W striking oblique-slip sources thought to have caused one of the three main events of the December 1456 sequence (Io XI MCS), the most destructive events in the southern Apennines known to date. We maintain that the 21 August 1962, 18:09 earthquake occurred along the E-W striking fault system responsible for the southernmost event of the 1456 sequence and for two smaller but instrumentally documented events that occurred on 6 May 1971 (Mw 5.0) and 27 September 2012 (Mw 4.6), further suggesting that normal faulting is not the dominant tectonic style in this portion of the Italian peninsula.

In the shadow of 1857-the effect of the great Ft. Tejon earthquake on subsequent earthquakes in southern California

USGS Publications Warehouse

Harris, R.A.; Simpson, R.W.

1996-01-01

The great 1857 Fort Tejon earthquake is the largest earthquake to have hit southern California during the historic period. We investigated if seismicity patterns following 1857 could be due to static stress changes generated by the 1857 earthquake. When post-1857 earthquakes with unknown focal mechanisms were assigned strike-slip mechanisms with strike and rake determined by the nearest active fault, 13 of the 13 southern California M???5.5 earthquakes between 1857 and 1907 were encouraged by the 1857 rupture. When post-1857 earthquakes in the Transverse Ranges with unknown focal mechanisms were assigned reverse mechanisms and all other events were assumed strike-slip, 11 of the 13 earthquakes were encouraged by the 1857 earthquake. These results show significant correlations between static stress changes and seismicity patterns. The correlation disappears around 1907, suggesting that tectonic loading began to overwhelm the effect of the 1857 earthquake early in the 20th century.

Earthquake scaling laws for rupture geometry and slip heterogeneity

NASA Astrophysics Data System (ADS)

Thingbaijam, Kiran K. S.; Mai, P. Martin; Goda, Katsuichiro

2016-04-01

We analyze an extensive compilation of finite-fault rupture models to investigate earthquake scaling of source geometry and slip heterogeneity to derive new relationships for seismic and tsunami hazard assessment. Our dataset comprises 158 earthquakes with a total of 316 rupture models selected from the SRCMOD database (http://equake-rc.info/srcmod). We find that fault-length does not saturate with earthquake magnitude, while fault-width reveals inhibited growth due to the finite seismogenic thickness. For strike-slip earthquakes, fault-length grows more rapidly with increasing magnitude compared to events of other faulting types. Interestingly, our derived relationship falls between the L-model and W-model end-members. In contrast, both reverse and normal dip-slip events are more consistent with self-similar scaling of fault-length. However, fault-width scaling relationships for large strike-slip and normal dip-slip events, occurring on steeply dipping faults (δ~90° for strike-slip faults, and δ~60° for normal faults), deviate from self-similarity. Although reverse dip-slip events in general show self-similar scaling, the restricted growth of down-dip fault extent (with upper limit of ~200 km) can be seen for mega-thrust subduction events (M~9.0). Despite this fact, for a given earthquake magnitude, subduction reverse dip-slip events occupy relatively larger rupture area, compared to shallow crustal events. In addition, we characterize slip heterogeneity in terms of its probability distribution and spatial correlation structure to develop a complete stochastic random-field characterization of earthquake slip. We find that truncated exponential law best describes the probability distribution of slip, with observable scale parameters determined by the average and maximum slip. Applying Box-Cox transformation to slip distributions (to create quasi-normal distributed data) supports cube-root transformation, which also implies distinctive non-Gaussian slip distributions. To further characterize the spatial correlations of slip heterogeneity, we analyze the power spectral decay of slip applying the 2-D von Karman auto-correlation function (parameterized by the Hurst exponent, H, and correlation lengths along strike and down-slip). The Hurst exponent is scale invariant, H = 0.83 (± 0.12), while the correlation lengths scale with source dimensions (seismic moment), thus implying characteristic physical scales of earthquake ruptures. Our self-consistent scaling relationships allow constraining the generation of slip-heterogeneity scenarios for physics-based ground-motion and tsunami simulations.

The SCEC 3D Community Fault Model (CFM-v5): An updated and expanded fault set of oblique crustal deformation and complex fault interaction for southern California

NASA Astrophysics Data System (ADS)

Nicholson, C.; Plesch, A.; Sorlien, C. C.; Shaw, J. H.; Hauksson, E.

2014-12-01

Southern California represents an ideal natural laboratory to investigate oblique deformation in 3D owing to its comprehensive datasets, complex tectonic history, evolving components of oblique slip, and continued crustal rotations about horizontal and vertical axes. As the SCEC Community Fault Model (CFM) aims to accurately reflect this 3D deformation, we present the results of an extensive update to the model by using primarily detailed fault trace, seismic reflection, relocated hypocenter and focal mechanism nodal plane data to generate improved, more realistic digital 3D fault surfaces. The results document a wide variety of oblique strain accommodation, including various aspects of strain partitioning and fault-related folding, sets of both high-angle and low-angle faults that mutually interact, significant non-planar, multi-stranded faults with variable dip along strike and with depth, and active mid-crustal detachments. In places, closely-spaced fault strands or fault systems can remain surprisingly subparallel to seismogenic depths, while in other areas, major strike-slip to oblique-slip faults can merge, such as the S-dipping Arroyo Parida-Mission Ridge and Santa Ynez faults with the N-dipping North Channel-Pitas Point-Red Mountain fault system, or diverge with depth. Examples of the latter include the steep-to-west-dipping Laguna Salada-Indiviso faults with the steep-to-east-dipping Sierra Cucapah faults, and the steep southern San Andreas fault with the adjacent NE-dipping Mecca Hills-Hidden Springs fault system. In addition, overprinting by steep predominantly strike-slip faulting can segment which parts of intersecting inherited low-angle faults are reactivated, or result in mutual cross-cutting relationships. The updated CFM 3D fault surfaces thus help characterize a more complex pattern of fault interactions at depth between various fault sets and linked fault systems, and a more complex fault geometry than typically inferred or expected from projecting near-surface data down-dip, or modeled from surface strain and potential field data alone.

Determination of Source Parameters for Earthquakes in the Northeastern United States and Quebec, Canada by Using Regional Broadband Seismograms

NASA Astrophysics Data System (ADS)

Du, W.; Kim, W.; Sykes, L. R.

2001-05-01

We studied approximately 20 earthquakes which have occurred in the Northeastern United States and Quebec, southern Canada since 1990. These earthquakes have local magnitude (ML) ranging from 3.5 to 5.2 and are well recorded by broadband seismographic stations in the region. Focal depth and moment tensor of these earthquakes are determined by using waveform inversion technique in which the best fit double-couple mechanism is obtained through a grid search over strike, dip and rake angles. Complete synthetics for three-component displacement signals in the period range 1 to 30 seconds are calculated. In most cases, long period Pnl and surface waves are used to constrain the source parameters. Our results indicate that most of the events show the horizontal compression with near horizontal P axis striking NE-SW. However, three events along the lower St. Lawrence River shows the P axes striking ESE-SE (100-130 degrees) with plunge angles of about 20 degrees. Focal depths of these events range from 2 to 28 km. Four events along the Appalachian Mts. have occurred with 2 to 5 km depths -- Jan. 16, 1994 Reading, Pa sequence, Sep. 25, 1998 Pymatuning, Pa event, Jan. 26, 2001 Ashutabula, Oh earthquake and an event in the Charlevoix seismic zone, Canada (Oct. 28, 1997). Two events have occurred at depth greater than 20 km. These are Quebec City earthquake on Nov. 6, 1997 and Christieville, Quebec event on May 4, 1997. We also observed the apparent discrepancy between the moment magnitude (Mw) and local magnitude (ML). Preliminary results show that for the events studied, Mw tends to be about 0.3 magnitude units smaller than the corresponding ML. However, some events show comparable Mw and ML values, for instance, the 1994 Reading, Pa sequence and Oct. 28, 1997 Charlevoix earthquake. These events have occurred at shallow depths and show low stress drops (less than 100 bars). We believe that this magnitude discrepancy reflects the source characteristics of intraplate events in the region. A striking feature of the waveform inversion method in the Northeastern United States is that we can determine fairly reliable focal depth and mechanisms for earthquakes with magnitude down to 3.5 and in some cases, down to 2.5. It is mainly due to availability of high quality three-component, broadband waveform data at short epicentral distances due to increasing coverage of the broadband seismographs of the Lamont-Doherty Cooperative seismographic Network (LCSN), the National Seismographic Network (USNSN) and the Canadian National Seismographic Network (CNSN) in the region. ~

Contraintes sismiques sur les structures crustales de l'Abitibi et de l'Opatica

NASA Astrophysics Data System (ADS)

Bellefleur, Gilles

The objectives of the work presented in this thesis are two-fold. The first consists in determining the tri-dimensional orientation of reflective structures from seismic reflection data acquired along 2D crooked profiles, while the second, based on these orientations, consists in defining geometric constraints on the tectonic scenarios proposed for the Abitibi and Opatica subprovinces. To provide precise estimates of reflector orientations, we use three distinct approaches, which, however, require acquisition profiles that call locally provide 3D informations. In the first, we use crossdip analysis and interpretation of the seismic sections improved by applying the crossdip corrections to determine the orientations of the reflectors. In the second, the strikes and dips of reflectors are estimated in the crooked parts of seismic reflection profiles by estimating a measure of coherency along the traveltime trajectories defined by a particular azimuth, dip and depth, and a medium velocity. Finally, we also use the dip of reflections observed on intersecting profiles to establish the 3D orientation of reflective structures. In general, reflectors observed in the Abitibi greenstone belt and Opatica belt have strikes parallel to the deformation structures mapped at surface, suggesting that the reflectors are related to the tectonic processes which affected independently or simultaneously the two subprovinces. Most of the reflectors recovered in the Opatica belt strike ENE-WSW and dip shallowly to the north and to the south. Their attitudes coincide with the orientations of deformation fabrics associated with a N-S shortening event, which affected the belt between 2700 and 2680 Ma. Mantle reflections, previously interpreted as a relict suture of an Archean subduction zone, dip to the north at around 30°--45° and are also associated with this N-S event. Reflectors with NNE strikes and shallow dips toward the east are correlated with surface evidence for early west vergent thrusting in the Opatica crust. Mid-crustal reflectors in the Abitibi define two areas with distinctive geometry: reflectors beneath the southern Abitibi belt are oppositely-dipping, and convergent at depth, providing a V-shape aspect to the greenstone rocks, other reflectors beneath the northern Abitibi belt are, in general, similarly oriented, dipping at an average of 30° toward the north. These north-dipping reflectors are partly disrupted by a low-reflectivity zone located north of the Casa-Berardi tectonic zone at mid-crustal levels. The low reflectivity zone is attributed to rocks of the Opatica belt, located underneath the northern Abitibi greenstone belt during a late stage of the accretion of the two subprovinces. The geometry of the reflectors recovered in the Abitibi and Opatica is consistent with the different tectonic histories proposed for the two subprovinces, until common deformation during a N-S shortening event. Attitudes recovered in the northern Abitibi belt and Opatica are consistent with tectonic scenarios involving underthrusting of Abitibi middle and lower-crustal terranes beneath the Opatica belt, while the oppositely dipping reflectors recovered in the middle crust beneath the southern Abitibi belt could be representative of a rifted volcanic arc environment.

Spatial Comparisons of Tremor and Slow Slip as a Constraint on Fault Strength in the Northern Cascadia Subduction Zone

NASA Astrophysics Data System (ADS)

Hall, K.; Schmidt, D. A.; Houston, H.

2017-12-01

We measure displacement vectors from about 50 or more PANGA 3-component GPS stations to analyze six large ETS events from 2007 - 2016 in northern Cascadia, and invert for slip on a realistic plate interface. Our previous results indicated that significant slip of up to 2 cm occurs 10 to 15 km up-dip of the western edge of tremor beneath the Olympic Peninsula. This far up-dip aseismic slip persists in several of the ETS events. We also find that this offset appears to vary along-strike with a greater offset beneath the Olympic Peninsula and up into the Strait of Juan de Fuca in comparison to lower Puget Sound. To explain this, we explore how properties (temperature and permeability) of the overlying structure may influence fault strength. In our conceptual model, the observation that slip inferred from GPS can extend updip of tremor suggests that updip of the observed edge of tremor, seismogenic patches that could produce tremor and low frequency earthquakes (LFEs) are too strong to fail from the relatively minor amount of far up-dip slow slip. This is consistent with the observation that, within the ETS zone, down-dip LFEs occur frequently, whereas up-dip LFEs occur only during the largest ETS events and are unaffected by tidal stresses until the later stages of an ETS event. This suggests that the up-dip seismogenic patches have a larger discrepancy between their strength and stress states, and therefore require larger stress perturbations (such as those from a propagating ETS slip pulse) to trigger seismic failure. We consider whether lateral variations in overlying structure may explain the along-strike variations in far up-dip aseismic slip. There is an abrupt change in lithology from the meta-sediments of the Olympic accretionary complex to the mafic basalts of the Crescent terrane. The juxtaposition of these different lithologies could potentially explain the along-strike variations in far up-dip aseismic slip. We propose to explore whether relative changes in either thermal conductivity or permeability could lead to effects of a reasonable magnitude and on a comparable length scale to explain the observed offset between tremor and slow slip in northern Cascadia. By using simple first-order models, we explore whether relative changes in these diffusive properties may encourage aseismic slip, but fail to generate tremor.

Systematic detection of long-term slow slip events along Hyuga-nada to central Shikoku, Nankai subduction zone, using GNSS data

NASA Astrophysics Data System (ADS)

Takagi, R.; Obara, K.; Uchida, N.

2017-12-01

Understanding slow earthquake activity improves our knowledge of slip behavior in brittle-ductile transition zone and subduction process including megathrust earthquakes. In order to understand overall picture of slow slip activity, it is important to make a comprehensive catalog of slow slip events (SSEs). Although short-term SSEs have been detected by GNSS and tilt meter records systematically, analysis of long-term slow slip events relies on individual slip inversions. We develop an algorism to systematically detect long-term SSEs and estimate source parameters of the SSEs using GNSS data. The algorism is similar to GRiD-MT (Tsuruoka et al., 2009), which is grid-based automatic determination of moment tensor solution. Instead of moment tensor fitting to long period seismic records, we estimate parameters of a single rectangle fault to fit GNSS displacement time series. First, we make a two dimensional grid covering possible location of SSE. Second, we estimate best-fit parameters (length, width, slip, and rake) of the rectangle fault at each grid point by an iterative damped least square method. Depth, strike, and dip are fixed on the plate boundary. Ramp function with duration of 300 days is used for expressing time evolution of the fault slip. Third, a grid maximizing variance reduction is selected as a candidate of long-term SSE. We also search onset of ramp function based on the grid search. We applied the method to GNSS data in southwest Japan to detect long-term SSEs in Nankai subduction zone. With current selection criteria, we found 13 events with Mw6.2-6.9 in Hyuga-nada, Bungo channel, and central Shikoku from 1998 to 2015, which include unreported events. Key finding is along strike migrations of long-term SSEs from Hyuga-nada to Bungo channel and from Bungo channel to central Shikoku. In particular, three successive events migrating northward in Hyuga-nada preceded the 2003 Bungo channel SSE, and one event in central Shikoku followed the 2003 SSE in Bungo channel. The space-time dimensions of the possible along-strike migration are about 300km in length and 6 years in time. Systematic detection with assumptions of various durations in the time evolution of SSE may improve the picture of SSE activity and possible interaction with neighboring SSEs.

Seismotectonics of Western Turkey: A Synthesis of Source Parameters and Rupture Histories of Recent Earthquakes

NASA Astrophysics Data System (ADS)

Taymaz, T.; Tan, O.; Yolsal, S.

2004-12-01

The Aegean region, including western Turkey and Greece, is indeed one of the most seismically active and rapidly deforming continental domains in the Earth. The wide range of deformational processes occurring in this region means that the eastern Mediterranean provides a unique opportunity to improve our understanding of the complex kinematics of continental collision, including strike-slip faulting and crustal extension, as well as associated seismicity and volcanism. The tectonic evolution of the Eastern Mediterranean region is dominated by effects of subduction along the Hellenic (Aegean) arc and of continental collision in eastern Anatolia and the Caucasus. Northward subduction of the African plate beneath western Anatolia and the Aegean region is causing crustal extension in the overlying Aegean province. The interplay between dynamic effects of the relative motions of adjoining plates thus controls large-scale crustal deformation and the associated earthquake activity in Turkey. The Aegean region has been subject to extension since Miocene time, and this extension has left a pronounced expression in the present-day topography. It is further widely accepted that the rapid extension observed in western Turkey is mainly accommodated by large active normal faults that control the geomorphology which is dominated by a series of E-W trending normal-fault-bounded horst and graben structures; the N-S extension inferred from these structures is consistent with regional earthquake focal mechanisms. The E-W trending Menderes graben, the NE-SW trending Burdur, Acigol and Baklan, and NW-SE trending Dinar and Sultandag-Aksehir basins all bounded by large faults form a system of half-graben whose orientation is evident in both the topography and the tilting of Neogene sediments adjacent to them. We have studied source mechanisms and rupture histories of ˜20 earthquakes using body-waveform modelling, and have compared the shapes and amplitudes of teleseismic long-period P-, SH-, and broadband P-waveforms recorded by GDSN stations in the distance range of 30° -90° . The final solutions were also constrained by P-wave first motion polarities of near-field stations. They all exhibit the characteristics and structural complexities associated with strike-slip and normal faulting as a result of ongoing crustal deformation. We found strike, dip, rake, centroid depth, seismic moment, and source time functions and rupture history and slip distributions.

Source rupture process of the 12 January 2010 Port-au-Prince (Haiti, Mw7.0) earthquake

NASA Astrophysics Data System (ADS)

Borges, José; Caldeira, Bento; Bezzeghoud, Mourad; Santos, Rúben

2010-05-01

The Haiti earthquake occurred on tuesday, January 12, 2010 at 21:53:10 UTC. Its epicenter was at 18.46 degrees North, 72.53 degrees West, about 25 km WSW of Haiti's capital, Port-au-Prince. The earthquake was relatively shallow (H=13 km, U.S. Geological Survey) and thus had greater intensity and destructiveness. The earthquake occurred along the tectonic boundary between Caribbean and North America plate. This plate boundary is dominated by left-lateral strike slip motion and compression with 2 cm/year of slip velocity eastward with respect to the North America plate. The moment magnitude was measured to be 7.0 (U.S. Geological Survey) and 7.1 (Harvard Centroid-Moment-Tensor (CMT). More than 10 aftershocks ranging from 5.0 to 5.9 in magnitude (none of magnitude larger than 6.0) struck the area in hours following the main shock. Most of these aftershocks have occurred to the West of the mainshock in the Mirogoane Lakes region and its distribution suggests that the length of the rupture was around 70 km. The Harvard Centroid Moment Tensor (CMT) mechanism solution indicates lefth-lateral strike slip movement with a fault plane trending toward (strike = 251o ; dip = 70o; rake = 28o). In order to obtain the spatiotemporal slip distribution of a finite rupture model we have used teleseismic body wave and the Kikuchi and Kanamori's method [1]. Rupture velocity was constrained by using the directivity effect determined from a set of waveforms well recorded at regional and teleseismic distances [2]. Finally, we compared a map of aftershocks with the Coulomb stress changes caused by the event in the region [3]. [1]- Kikuchi, M., and Kanamori, H., 1982, Inversion of complex body waves: Bull. Seismol. Soc. Am., v. 72, p. 491-506. [2] Caldeira B., Bezzeghoud M, Borges JF, 2009; DIRDOP: a directivity approach to determining the seismic rupture velocity vector. J Seismology, DOI 10.1007/s10950-009-9183-x (http://www.springerlink.com/content/xp524g2225628773/) [3] -King, G. C. P., Stein, R. S. y Lin, J, 1994, Static stress changes and the triggering of earthquakes. Bull. Seismol. Soc. Am. 84,935-953.

Evolving transpressional strain fields along the San Andreas fault in southern California: implications for fault branching, fault dip segmentation and strain partitioning

NASA Astrophysics Data System (ADS)

Bergh, Steffen; Sylvester, Arthur; Damte, Alula; Indrevær, Kjetil

2014-05-01

The San Andreas fault in southern California records only few large-magnitude earthquakes in historic time, and the recent activity is confined primarily on irregular and discontinuous strike-slip and thrust fault strands at shallow depths of ~5-20 km. Despite this fact, slip along the San Andreas fault is calculated to c. 35 mm/yr based on c.160 km total right lateral displacement for the southern segment of the fault in the last c. 8 Ma. Field observations also reveal complex fault strands and multiple events of deformation. The presently diffuse high-magnitude crustal movements may be explained by the deformation being largely distributed along more gently dipping reverse faults in fold-thrust belts, in contrast to regions to the north where deformation is less partitioned and localized to narrow strike-slip fault zones. In the Mecca Hills of the Salton trough transpressional deformation of an uplifted segment of the San Andreas fault in the last ca. 4.0 My is expressed by very complex fault-oblique and fault-parallel (en echelon) folding, and zones of uplift (fold-thrust belts), basement-involved reverse and strike-slip faults and accompanying multiple and pervasive cataclasis and conjugate fracturing of Miocene to Pleistocene sedimentary strata. Our structural analysis of the Mecca Hills addresses the kinematic nature of the San Andreas fault and mechanisms of uplift and strain-stress distribution along bent fault strands. The San Andreas fault and subsidiary faults define a wide spectrum of kinematic styles, from steep localized strike-slip faults, to moderate dipping faults related to oblique en echelon folds, and gently dipping faults distributed in fold-thrust belt domains. Therefore, the San Andreas fault is not a through-going, steep strike-slip crustal structure, which is commonly the basis for crustal modeling and earthquake rupture models. The fault trace was steep initially, but was later multiphase deformed/modified by oblique en echelon folding, renewed strike-slip movements and contractile fold-thrust belt structures. Notably, the strike-slip movements on the San Andreas fault were transformed outward into the surrounding rocks as oblique-reverse faults to link up with the subsidiary Skeleton Canyon fault in the Mecca Hills. Instead of a classic flower structure model for this transpressional uplift, the San Andreas fault strands were segmented into domains that record; (i) early strike-slip motion, (ii) later oblique shortening with distributed deformation (en echelon fold domains), followed by (iii) localized fault-parallel deformation (strike-slip) and (iv) superposed out-of-sequence faulting and fault-normal, partitioned deformation (fold-thrust belt domains). These results contribute well to the question if spatial and temporal fold-fault branching and migration patterns evolving along non-vertical strike-slip fault segments can play a role in the localization of earthquakes along the San Andreas fault.

Possible Strain Partitioning Between the Kumano Forearc Basin and the Slope of the Nankai Trough Accretionary Prism

NASA Astrophysics Data System (ADS)

Martin, K. M.; Gulick, S. P.; Bangs, N. L.; Ashi, J.; Moore, G. F.; Nakamura, Y.; Tobin, H. J.

2008-12-01

A 12 km wide, 56 km long, three-dimensional (3-D) seismic volume acquired over the Nankai Trough offshore the Kii Peninsula, Japan images the Nankai accretionary prism, forearc basin and the subducting Philippine Sea Plate. We have analyzed an unusual, trench-parallel ~1200 m deep depression (a "notch") along the seaward edge of the Kumano forearc basin, just landward of the shallowest branch of the previously- mapped splay-fault system. The shape of this feature varies along strike, from a single, steep-walled, ~3.5 km wide notch in the northeast, to a broader, ~6 km wide zone with several shallower linear bathymetric lows in the southwest. We have mapped the area below the notch and found both vertical faults and faults which dip toward the central axis of the depression. Some dipping faults appear to have normal offset, consistent with the formation of a bathymetric low. Some of these dipping faults may join the central vertical fault(s) at depth, creating apparent flower structures. Offset on the vertical faults is more difficult to determine, but the dip and along-strike geometry of these faults makes predominantly normal or thrust motion unlikely. We conclude, therefore, that the notch feature is the bathymetric expression of a transtensional fault system. Possible causes for such a system in the forearc include variations in splay fault geometry and strain partitioning. By considering only the along-strike variability of the mapped splay fault, we were unable to explain a transform feature at the scale of the notch. Strike-slip faulting at the seaward edge of forearc basins is also observed in Sumatra and is there attributed to strain partitioning due to oblique convergence. The wedge and décollment strength variations which control the location of the forearc basins may therefore play a role in the position where the along-strike component of deformation is localized. While the obliquity of convergence in the Nankai trough is comparatively small (13-30 degrees), we believe it is still significant enough to account for the formation of the observed notch.

Moment tensor inversion with three-dimensional sensor configuration of mining induced seismicity (Kiruna mine, Sweden)

NASA Astrophysics Data System (ADS)

Ma, Ju; Dineva, Savka; Cesca, Simone; Heimann, Sebastian

2018-06-01

Mining induced seismicity is an undesired consequence of mining operations, which poses significant hazard to miners and infrastructures and requires an accurate analysis of the rupture process. Seismic moment tensors of mining-induced events help to understand the nature of mining-induced seismicity by providing information about the relationship between the mining, stress redistribution and instabilities in the rock mass. In this work, we adapt and test a waveform-based inversion method on high frequency data recorded by a dense underground seismic system in one of the largest underground mines in the world (Kiruna mine, Sweden). A stable algorithm for moment tensor inversion for comparatively small mining induced earthquakes, resolving both the double-couple and full moment tensor with high frequency data, is very challenging. Moreover, the application to underground mining system requires accounting for the 3-D geometry of the monitoring system. We construct a Green's function database using a homogeneous velocity model, but assuming a 3-D distribution of potential sources and receivers. We first perform a set of moment tensor inversions using synthetic data to test the effects of different factors on moment tensor inversion stability and source parameters accuracy, including the network spatial coverage, the number of sensors and the signal-to-noise ratio. The influence of the accuracy of the input source parameters on the inversion results is also tested. Those tests show that an accurate selection of the inversion parameters allows resolving the moment tensor also in the presence of realistic seismic noise conditions. Finally, the moment tensor inversion methodology is applied to eight events chosen from mining block #33/34 at Kiruna mine. Source parameters including scalar moment, magnitude, double-couple, compensated linear vector dipole and isotropic contributions as well as the strike, dip and rake configurations of the double-couple term were obtained. The orientations of the nodal planes of the double-couple component in most cases vary from NNW to NNE with a dip along the ore body or in the opposite direction.

Moment Tensor Inversion with 3D sensor configuration of Mining Induced Seismicity (Kiruna mine, Sweden)

NASA Astrophysics Data System (ADS)

Ma, Ju; Dineva, Savka; Cesca, Simone; Heimann, Sebastian

2018-03-01

Mining induced seismicity is an undesired consequence of mining operations, which poses significant hazard to miners and infrastructures and requires an accurate analysis of the rupture process. Seismic moment tensors of mining-induced events help to understand the nature of mining-induced seismicity by providing information about the relationship between the mining, stress redistribution and instabilities in the rock mass. In this work, we adapt and test a waveform-based inversion method on high frequency data recorded by a dense underground seismic system in one of the largest underground mines in the world (Kiruna mine, Sweden). Stable algorithm for moment tensor inversion for comparatively small mining induced earthquakes, resolving both the double couple and full moment tensor with high frequency data is very challenging. Moreover, the application to underground mining system requires accounting for the 3D geometry of the monitoring system. We construct a Green's function database using a homogeneous velocity model, but assuming a 3D distribution of potential sources and receivers. We first perform a set of moment tensor inversions using synthetic data to test the effects of different factors on moment tensor inversion stability and source parameters accuracy, including the network spatial coverage, the number of sensors and the signal-to-noise ratio. The influence of the accuracy of the input source parameters on the inversion results is also tested. Those tests show that an accurate selection of the inversion parameters allows resolving the moment tensor also in presence of realistic seismic noise conditions. Finally, the moment tensor inversion methodology is applied to 8 events chosen from mining block #33/34 at Kiruna mine. Source parameters including scalar moment, magnitude, double couple, compensated linear vector dipole and isotropic contributions as well as the strike, dip, rake configurations of the double couple term were obtained. The orientations of the nodal planes of the double-couple component in most cases vary from NNW to NNE with a dip along the ore body or in the opposite direction.

Insights into the Fault Geometry and Rupture History of the 2016 MW 7.8 Kaikoura, New Zealand, Earthquake

NASA Astrophysics Data System (ADS)

Adams, M.; Ji, C.

2017-12-01

The November 14th 2016 MW 7.8 Kaikoura, New Zealand earthquake occurred along the east coast of the northern part of the South Island. The local tectonic setting is complicated. The central South Island is dominated by oblique continental convergence, whereas the southern part of this island experiences eastward subduction of the Australian plate. Available information (e.g., Hamling et al., 2017; Bradley et al., 2017) indicate that this earthquake involved multiple fault segments of the Marlborough fault system (MFS) as the rupture propagated northwards for more than 150 km. Additional slip might also occur on the subduction interface of the Pacific plate under the Australian plate, beneath the MFS. However, the exact number of involved fault segments as well as the temporal co-seismic rupture sequence has not been fully determined with geodetic and geological observations. Knowledge of the kinematics of complex fault interactions has important implications for our understanding of global seismic hazards, particularly to relatively unmodeled multisegment ruptures. Understanding the Kaikoura earthquake will provide insight into how one incorporates multi-fault ruptures in seismic-hazard models. We propose to apply a multiple double-couple inversion to determine the fault geometry and spatiotemporal rupture history using teleseismic and strong motion waveforms, before constraining the detailed slip history using both seismic and geodetic data. The Kaikoura earthquake will be approximated as the summation of multiple subevents—each represented as a double-couple point source, characterized by i) fault geometry (strike, dip and rake), ii) seismic moment, iii) centroid time, iv) half-duration and v) location (latitude, longitude and depth), a total of nine variables. We progressively increase the number of point sources until the additional source cannot produce significant improvement to the observations. Our preliminary results using only teleseismic data indicate that, broadly speaking, the sequence of fault planes dips towards the northwest and the motion of slip is largely to the northeast. Sequence and timing of the rupturing faults is still to be determined.

Controls of earthquake faulting style on near field landslide triggering: The role of coseismic slip

NASA Astrophysics Data System (ADS)

Tatard, L.; Grasso, J. R.

2013-06-01

compare the spatial distributions of seven databases of landslides triggered by Mw=5.6-7.9 earthquakes, using distances normalized by the earthquake fault length. We show that the normalized landslide distance distributions collapse, i.e., the normalized distance distributions overlap whatever the size of the earthquake, separately for the events associated with dip-slip, buried-faulting earthquakes, and surface-faulting earthquakes. The dip-slip earthquakes triggered landslides at larger normalized distances than the oblique-slip event of Loma Prieta. We further identify that the surface-faulting earthquakes of Wenchuan, Chi-Chi, and Kashmir triggered landslides at normalized distances smaller than the ones expected from their Mw ≥ 7.6 magnitudes. These results support a control of the seismic slip (through amplitude, rake, and surface versus buried slip) on the distances at which landslides are triggered. In terms of coseismic landslide management in mountainous areas, our results allow us to propose distances at which 95 and 75% of landslides will be triggered as a function of the earthquake focal mechanism.

A catalog of coseismic uniform-slip models of geodetically unstudied earthquakes along the Sumatran plate boundary

NASA Astrophysics Data System (ADS)

Wong, N. Z.; Feng, L.; Hill, E.

2017-12-01

The Sumatran plate boundary has experienced five Mw > 8 great earthquakes, a handful of Mw 7-8 earthquakes and numerous small to moderate events since the 2004 Mw 9.2 Sumatra-Andaman earthquake. The geodetic studies of these moderate earthquakes have mostly been passed over in favour of larger events. We therefore in this study present a catalog of coseismic uniform-slip models of one Mw 7.2 earthquake and 17 Mw 5.9-6.9 events that have mostly gone geodetically unstudied. These events occurred close to various continuous stations within the Sumatran GPS Array (SuGAr), allowing the network to record their surface deformation. However, due to their relatively small magnitudes, most of these moderate earthquakes were recorded by only 1-4 GPS stations. With the limited observations per event, we first constrain most of the model parameters (e.g. location, slip, patch size, strike, dip, rake) using various external sources (e.g., the ANSS catalog, gCMT, Slab1.0, and empirical relationships). We then use grid-search forward models to explore a range of some of these parameters (geographic position for all events and additionally depth for some events). Our results indicate the gCMT centroid locations in the Sumatran subduction zone might be biased towards the west for smaller events, while ANSS epicentres might be biased towards the east. The more accurate locations of these events are potentially useful in understanding the nature of various structures along the megathrust, particularly the persistent rupture barriers.

Focal mechanism determination of induced micro-earthquakes in reservoir by non linear inversion of amplitudes

NASA Astrophysics Data System (ADS)

Godano, M.; Regnier, M.; Deschamps, A.; Bardainne, T.

2009-04-01

Since these last years, the feasibility of CO2 storage in geological reservoir is carefully investigated. The monitoring of the seismicity (natural or induced by the gas injection) in the reservoir area is crucial for safety concerns. The location of the seismic events provide an imaging of the active structures which can be a potential leakage paths. Besides, the focal mechanism is an other important seismic attribute providing direct informations about the rock fracturing, and indirect information about the state of stress in the reservoir. We address the problem of focal mechanism determination for the micro-earthquakes induced in reservoirs with a potential application to the sites of CO2 storage. We developed a non linear inversion method of P, SV and SH direct waves amplitudes. To solve the inverse problem, we perfected our own simulated annealing algorithm. Our method allows simply determining the fault plane solution (strike, dip and rake of the fault plane) in the case of a double-couple source assumption. More generally, our method allows also determining the full moment tensor in case of non-purely shear source assumption. We searched to quantify the uncertainty associated to the obtained focal mechanisms. We defined three uncertainty causes. The first is related to the convergence process of the inversion, the second is related the amplitude picking error caused by the noise level and the third is related to the event location uncertainty. We performed a series of tests on synthetic data generated in reservoir configuration in order to validate our inversion method.

Structure, stratigraphy, and origin of Husband Hill, Columbia Hills, Gusev Crater, Mars

USGS Publications Warehouse

McCoy, T.J.; Sims, M.; Schmidt, M.E.; Edwards, L.; Tornabene, L.L.; Crumpler, L.S.; Cohen, B. A.; Soderblom, L.A.; Blaney, D.L.; Squyres, S. W.; Arvidson, R. E.; Rica, J.W.; Treguier, E.; d'Uston, C.; Grant, J. A.; McSween, H.Y.; Golombek, M.P.; Haldemann, A.F.C.; de Souza, P.A.

2008-01-01

The strike and dip of lithologic units imaged in stereo by the Spirit rover in the Columbia Hills using three-dimensional imaging software shows that measured dips (15-32??) for bedding on the main edifice of the Columbia Hill are steeper than local topography (???8-10??). Outcrops measured on West Spur are conformable in strike with shallower dips (7-15??) than observed on Husband Hill. Dips are consistent with observed strata draping the Columbia Hills. Initial uplift was likely related either to the formation of the Gusev Crater central peak or ring or through mutual interference of overlapping crater rims. Uplift was followed by subsequent draping by a series of impact and volcaniclastic materials that experienced temporally and spatially variable aqueous infiltration, cementation, and alteration episodically during or after deposition. West Spur likely represents a spatially isolated depositional event. Erosion by a variety of processes, including mass wasting, removed tens of meters of materials and formed the Tennessee Valley primarily after deposition. This was followed by eruption of the Adirondack-class plains basalt lava flows which embayed the Columbia Hills. Minor erosion, impact, and aeolian processes have subsequently modified the Columbia Hills. Copyright 2008 by the American Geophysical Union.

2D Ball-and-Socket Tectonic Rotation in a Heterogeneous Strain Field: The 2013 Mw7.7 Balochistan, Pakistan Earthquake

NASA Astrophysics Data System (ADS)

Barnhart, W. D.; Hayes, G. P.; Briggs, R. W.; Gold, R. D.; Bilham, R. G.

2014-12-01

The September 2013 Mw7.7 Balochistan strike-slip earthquake ruptured a ~200 km long segment of the curved Hoshab fault within the Makran accretionary prism - the active zone of convergence between the northward subducting Arabia plate and overriding Eurasia. The Hoshab fault ruptured bilaterally with ~10 m of mean sinistral and ~1.7 m of dip slip along the length of the rupture, quantified jointly from geodetic and seismological observations. This rupture is unusual because the fault dips ~60o towards the focus of a small circle centered in northwest Pakistan, and, despite a 30o increase in obliquity along the curving strike of the fault with respect to Arabia:Eurasia convergence, the ratio of strike and dip slip remain relatively uniform. Static friction prior to rupture was unusually weak ( <0.05) as inferred from topographic and slab profiles, and friction may have approached zero during dynamic rupture, thus permitting in part this unusual event. In this presentation, we argue that the northward dipping Hosab fault defines the northern rim of a structural unit in southeast Makran. This unit rotates - akin to a 2-D ball-and-socket joint - counter clockwise in response to India's penetration into the Eurasia plate. According to this interpretation, the mechanically weak Makran accretionary prism is subjected to a highly heterogeneous strain and deforms in response to convergence from both the Arabia and India plates. Rotation of the southeast Makran block accounts for complexity in the Chaman fault system and, in principle, reduces the seismic potential near Karachi by accommodating some slip along the southern Ornach-Nal fault. At the same time, geological indicators and along-strike fault slip profiles indicate that the Hoshab fault may also slip as a reverse fault in response to Arabia:Eurasia convergence - indicating that a single fault may accommodate multiple components of strain partitioning in a heterogeneous strain field over several seismic cycles.

Study on conditional probability of surface rupture: effect of fault dip and width of seismogenic layer

NASA Astrophysics Data System (ADS)

Inoue, N.

2017-12-01

The conditional probability of surface ruptures is affected by various factors, such as shallow material properties, process of earthquakes, ground motions and so on. Toda (2013) pointed out difference of the conditional probability of strike and reverse fault by considering the fault dip and width of seismogenic layer. This study evaluated conditional probability of surface rupture based on following procedures. Fault geometry was determined from the randomly generated magnitude based on The Headquarters for Earthquake Research Promotion (2017) method. If the defined fault plane was not saturated in the assumed width of the seismogenic layer, the fault plane depth was randomly provided within the seismogenic layer. The logistic analysis was performed to two data sets: surface displacement calculated by dislocation methods (Wang et al., 2003) from the defined source fault, the depth of top of the defined source fault. The estimated conditional probability from surface displacement indicated higher probability of reverse faults than that of strike faults, and this result coincides to previous similar studies (i.e. Kagawa et al., 2004; Kataoka and Kusakabe, 2005). On the contrary, the probability estimated from the depth of the source fault indicated higher probability of thrust faults than that of strike and reverse faults, and this trend is similar to the conditional probability of PFDHA results (Youngs et al., 2003; Moss and Ross, 2011). The probability of combined simulated results of thrust and reverse also shows low probability. The worldwide compiled reverse fault data include low fault dip angle earthquake. On the other hand, in the case of Japanese reverse fault, there is possibility that the conditional probability of reverse faults with less low dip angle earthquake shows low probability and indicates similar probability of strike fault (i.e. Takao et al., 2013). In the future, numerical simulation by considering failure condition of surface by the source fault would be performed in order to examine the amount of the displacement and conditional probability quantitatively.

Evaluation of the Performance and Flow in an Axial Compressor.

DTIC Science & Technology

1982-10-01

A Exit Rake P 11.00-P tP noz P2noz -PA SP-1 PHub - PA Exit Rake Pt11.50-Pt p - PA SP-1 PTip - PA Exit Rake Pt2.00-PPtpipe ATp Att Pspipe - PA SP-2...PTip - PA Exit Rake Pt6.50-Pt Inlet Rake Pt14.40-PA SP-8 PTip - PA Exit Rake Pt 17.00-Pt Inlet Rake Pt 1.30-PA SP-8 PHub - PA Exit Rake Pt17.50-Pt...Determination from Probe Pressures Pt (1) =((Pt=(1) + Phub ) + (Pt(1) + Pt(2)))/3 P t(2) P t(2) Pt (3) = t(3) P t(4) = (P t(3) + P t(4))/2 P t(5) =P t(4) Pt

Application of Borehole Geophysical Methods for Assessing Agro-Chemical Flow Paths in Fractured Bedrock Underlying the Black Brook Watershed, Northwestern New Brunswick

NASA Astrophysics Data System (ADS)

Desroches, A.; Butler, K.

2009-05-01

The upper Saint John River valley represents an economically important agricultural region that suffers from high nitrate levels in the groundwater as a result of fertilizer use. This study focuses on the fractured bedrock aquifer beneath the Black Brook Watershed, near Saint-Andre (Grand Falls), New Brunswick, where prediction of nitrate migration is limited by a lack of knowledge of the bedrock fracture characteristics. Bedrock consists of a fine-grained, siliciclastic unit of the Grog Brook Group gradationally overlain by a carbonate unit assigned to the Matapédia Group. Groundwater flow through the fractured bedrock is expected to be primarily influenced by the distribution and orientation of fractures in these rock units. This study demonstrates the effectiveness of the select suite of borehole-geophysical tools used to identify and describe the fractured bedrock characteristics, and assists in understanding the migration pathways of agrochemical leachate from farm fields. Fracture datasets were acquired from five new vertical boreholes that ranged from 50 to 140 metres in depth, and from three outcrop locations along the new Trans-Canada Highway, approximately two kilometres away. The borehole-geophysical methods used included natural gamma ray (GR), single point resistance (SPR), spontaneous potential (SP), slim-hole optical borehole televiewer (OBI) and acoustic borehole televiewer (ABI). The ABI and OBI tools delivered high-resolution oriented images of the borehole walls, and enabled visualization of fractures in situ, and provided accurate information on the location, orientation, and aperture. The GR, SPR and SP logs identified changes in lithology, bed thickness and conductive fracture zones. Detailed inspection of the borehole televiewer images identified 390 fractures. Equal-area stereographic and rose diagrams of fracture planes have been used to identify three discrete fracture sets: 1) steeply dipping fractures that strike 068o/248o, with fracture subsets dipping roughly 70o to 80o towards the N-NW and S-SE; 2) steeply dipping fractures that strike towards 156o/336o, with fracture subsets dipping roughly 70o to 80o towards the NE and SW; and 3) primary set of moderately dipping fractures that strike 074o/254o and dip roughly 30o to 40o towards the SE. The strike of the steeply dipping fracture sets are oriented roughly perpendicular to each other, reflecting two distinct fracture generation events. The low-angle fractures are most common and correspond to openings along bedding planes that dip roughly 38o towards 164o. This is a result of penetrating only one limb of a fold; presumably a similar set of bedding-plane openings occur along the adjacent limb of the fold, with resultant fracture dips towards the northwest. Fractures exposed in outcrops along the Trans-Canada Highway exhibit a similar orientation distribution to that observed in the boreholes. However, as expected, these exposures show a greater proportion of fractures with dips between 80o and 90o, compared to the vertical boreholes. A Terzaghi fracture probability correction was applied to the boreholes in order to account for this bias. The combined fracture datasets provide valuable information towards understanding groundwater flow and migration pathways of fertilizer leachate into the bedrock aquifer, and will lead to the development of more complex hydrogeological models.

The Dandridge-Vonore Fault Zone in the Eastern Tennessee Seismic Zone (and Rejuvenation of the Smokies?)

NASA Astrophysics Data System (ADS)

Cox, R. T.; Hatcher, R. D., Jr.; Forman, S. L.; Gamble, E. D. S.; Warrell, K. F.

2017-12-01

The eastern Tennessee seismic zone (ETSZ) trends 045o from NE Alabama and NW Georgia through Tennessee to SE Kentucky, and seismicity is localized 5-26 km deep in the basement. The ETSZ is the second most seismically active region in North America east of the Rocky Mountains, although no historic earthquakes larger than Mw 4.8 have been recorded here. Late Quaternary paleoiseismic evidence suggests that the ETSZ is capable of M7+ earthquakes and that neotectonic faults may have significantly influenced the regional relief. We have identified an 80 km-long, 060o-trending corridor in eastern Tennessee that contains collinear northeast-striking thrust, strike-slip, and normal Quaternary faults with displacements of 1-2 m, herein termed the Dandridge-Vonore fault zone (DVFZ). French Broad River alluvium in the northeast DVFZ near Dandridge, TN, is displaced by a 050o-striking, SE-dipping thrust fault and by a set of related fissures that record at least two significant post 25 ka paleo-earthquakes. Southwest of Dandridge near Alcoa, TN, a 060o-striking, SE-dipping thrust fault cuts Little River alluvium and records two significant post-15 ka paleo-earthquakes. Farther southwest at Vonore, colluvium with alluvial cobbles is thrust >1 m by a 057o-striking, steeply SE-dipping fault that may also have a significant strike-slip component, and Little Tennessee River alluvium is dropped >2 m along a 070o- striking normal fault. The DVFZ partly overlaps and is collinear with a local trend of maximum seismicity that extends 30 km farther SW of the DVFZ (as currently mapped), for a total length of 110 km. The DVFZ is coincident with a steep gradient in S-wave velocities (from high velocity on the SE to low velocity on the NW) at mid-crustal depths of 20 to 24 km, consistent with a fault and source zone at hypocentral depths in the crystalline basement. Moreover, the DVFZ parallels the NW foot of Blue Ridge Mountains, and the sense of thrusting at all sites of Quaternary faulting in the DVFZ is consistent with uplift of the Blue Ridge.

Impact of the slab dip change onto the deformation partitioning in the northern Lesser Antilles oblique subduction zone (Antigua-Virgin Islands)

NASA Astrophysics Data System (ADS)

Laurencin, Muriel; Marcaillou, Boris; Klingelhoefer, Frauke; Graindorge, David; Lebrun, Jean-Frédéric; Laigle, Mireille; Lallemand, Serge

2017-04-01

Marine geophysical cruises Antithesis (2013-2016) investigate the impact of the variations in interplate geometry onto margin tectonic deformation along the strongly oblique Lesser Antilles subduction zone. A striking features of this margin is the drastic increase in earthquake number from the quiet Barbuda-St Martin segment to the Virgin Islands platform. Wide-angle seismic data highlight a northward shallowing of the downgoing plate: in a 150 km distance from the deformation front, the slab dipping angle in the convergence direction decreases from 12° offshore of Antigua Island to 7° offshore of Virgin Islands. North-South wide-angle seismic line substantiates a drastic slab-dip change that likely causes this northward shallowing. This dip change is located beneath the southern tip of the Virgin Islands platform where the Anegada Passage entails the upper plate. Based on deep seismic lines and bathymetric data, the Anegada Passage is a 450 km long W-E trending set of pull-apart basins and strike-slip faults that extends from the Lesser Antilles accretionary prism to Puerto Rico. The newly observed sedimentary architecture within pull-apart Sombrero and Malliwana basins indicates a polyphased tectonic history. A past prominent NW-SE extensive to transtensive phase, possibly related to the Bahamas Bank collision, opened the Anegada Passage as previously published. Transpressive tectonic evidences indicate that these structures have been recently reactivated in an en-echelon sinistral strike-slip system. The interpreted strain ellipsoid is consistent with deformation partitioning. We propose that the slab northward shallowing increases the interplate coupling and the seismic activity beneath the Virgin Islands platform comparatively to the quiet Barbuda-St Martin segment. It is noteworthy that the major tectonic partitioning structure in the Lesser Antilles forearc is located above the slab dip change where the interplate seismic coupling increases.

Design and Evaluation of a New Boundary-Layer Rake for Flight Testing

NASA Technical Reports Server (NTRS)

Bui, Trong T.; Oates, David L.; Gonsalez, Jose C.

2000-01-01

A new boundary-layer rake has been designed and built for flight testing on the NASA Dryden Flight Research Center F-15B/Flight Test Fixture. A feature unique to this rake is its curved body, which allows pitot tubes to be more densely clustered in the near-wall region than conventional rakes allow. This curved rake design has a complex three-dimensional shape that requires innovative solid-modeling and machining techniques. Finite-element stress analysis of the new design shows high factors of safety. The rake has passed a ground test in which random vibration measuring 12 g rms was applied for 20 min in each of the three normal directions. Aerodynamic evaluation of the rake has been conducted in the NASA Glenn Research Center 8 x 6 Supersonic Wind Tunnel at Mach 0-2. The pitot pressures from the new rake agree with conventional rake data over the range of Mach numbers tested. The boundary-layer profiles computed from the rake data have been shown to have the standard logarithmic-law profile. Skin friction values computed from the rake data using the Clauser plot method agree with the Preston tube results and the van Driest II compressible skin friction correlation to approximately +/-5 percent.

Structural Analyses of the Kahiltna Terrane: A Kinematic Record of the Collision of the Talkeetna Superterrane

NASA Astrophysics Data System (ADS)

Bier, S. E.; Fisher, D.

2002-12-01

Macro-, meso-, and microscale structural analyses from several localities across the ~1000 km Kahiltna Terrane provide valuable kinematic insights into the late Cretaceous collision between the Talkeetna superterrane and North America. The Kahiltna Terrane, a Jurassic-Cretaceous flysch basin inboard of the Talkeetna superterrane (Wrangellia, Peninsular, and Alexander terranes), contains incremental strain indicators that record a history of oblique collision and subsequent deformation in a strike-slip regime. A comparison of structural data from localities across the Kahiltna terrane suggests a unique history not yet described in previous work on south-central Alaskan tectonics. Data was collected from the Reindeer Hills area, the northwestern Talkeetna Mountains, Denali National Park, the Peters Hills, and the Tordrillo Mountains. In the Reindeer Hills, a melange zone occurs as a series of exposures dismembered by ongoing strike slip faulting between the flysch of the Kahiltna terrane and the precollisional edge of the North American continent. This melange is characterized by fault-bounded blocks of Paleozoic limestone and sandstone within an argillite matrix with a conspicuous scaly fabric. The blocks range in size from 10 cm to tens of meters; and melange fish indicate a south-directed shear sense. The melange is overlain by a red and green (Triassic-Jurassic?) conglomerate along an unconformity that likely marks the base of a perched slope basin near the toe of an accretionary wedge. The strike of bedding and cleavage in this area trends EW. The fold axes trend NW-SE and folds verge to the south. In the northwest corner of the Talkeetna Mountains, the structure is dominated by north vergent folds and faults. The strike of bedding trends ~025°; whereas the strike of the cleavage is ~060°. Both cleavage and bedding dip to the southeast. The fold axes trend roughly NE-SW. North of the Denali Fault System, in Denali National Park, strike of bedding is ~122° and the dip is to the southwest. Folds can be divided into two sets: 1) tight folds with axes trending E-W and 2) open folds with axes that trend N-S. Cleavage is axial planar to the first set of folds. Crenulation cleavage that trends E-W may also be associated with the first set of folds. In the Peters Hills, reversals in facing direction indicate the presence of multiple macroscale folds. The strike of bedding and cleavage trend ~240° and dip to the northwest. Outcrop observations of smaller scale north-vergent folds and larger scale south-vergent folds suggest multiple deformation events. Stretching lineations trend NE-SW, and incremental strain indicators record indicate a dextral shearing event. The Kahiltna terrane exposed in the vicinity of the Tordrillo Mountains consists of alternating volcaniclastic sandstones and turbidite sequences. The strike of bedding and cleavage is ~240°, and they dip steeply to the northwest. Small isoclinal folds and faults indicate northwestward transport and deformation overprinted by large-scale open folds that verge to the east. Observations of the melange indicate precollisional northward-dipping subduction beneath an accretionary assemblage of Triassic(?) material. Structural observations from multiple localities across the Kahiltna terrane indicate northward-directed thrusting related to dextral transpression and oblique collision of the Talkeetna superterrane, with varying amounts of obliquity along the margin.

Ball-and-socket tectonic rotation during the 2013 Mw 7.7 Balochistan earthquake

NASA Astrophysics Data System (ADS)

Barnhart, W. D.; Hayes, G. P.; Briggs, R. W.; Gold, R. D.; Bilham, R.

2014-10-01

The September 2013 Mw 7.7 Balochistan earthquake ruptured a ∼200-km-long segment of the curved Hoshab fault in southern Pakistan with 10 ± 0.2 m of peak sinistral and ∼ 1.7 ± 0.8 m of dip slip. This rupture is unusual because the fault dips 60 ± 15° towards the focus of a small circle centered in northwest Pakistan, and, despite a 30° increase in obliquity along strike, the ratios of strike and dip slip remain relatively uniform. Surface displacements and geodetic and teleseismic source inversions quantify a bilateral rupture that propagated rapidly at shallow depths from a transtensional jog near the northern end of the rupture. Static friction prior to rupture was unusually weak (μ < 0.05), and friction may have approached zero during dynamic rupture. Here we show that the inward-dipping Hoshab fault defines the northern rim of a structural unit in southeast Makran that rotates - akin to a 2-D ball-and-socket joint - counter-clockwise in response to India's penetration into the Eurasian plate. This rotation accounts for complexity in the Chaman fault system and, in principle, reduces seismic potential near Karachi; nonetheless, these findings highlight deficiencies in strong ground motion equations and tectonic models that invoke Anderson-Byerlee faulting predictions.

Application of advanced geophysical logging methods in the characterization of a fractured-sedimentary bedrock aquifer, Ventura County, California

USGS Publications Warehouse

Williams, John H.; Lane, John W.; Singha, Kamini; Haeni, F. Peter

2002-01-01

An integrated suite of advanced geophysical logging methods was used to characterize the geology and hydrology of three boreholes completed in fractured-sedimentary bedrock in Ventura County, California. The geophysical methods included caliper, gamma, electromagnetic induction, borehole deviation, optical and acoustic televiewer, borehole radar, fluid resistivity, temperature, and electromagnetic flowmeter. The geophysical logging 1) provided insights useful for the overall geohydrologic characterization of the bedrock and 2) enhanced the value of information collected by other methods from the boreholes including core-sample analysis, multiple-level monitoring, and packer testing.The logged boreholes, which have open intervals of 100 to 200 feet, penetrate a sequence of interbedded sandstone and mudstone with bedding striking 220 to 250 degrees and dipping 15 to 40 degrees to the northwest. Fractures intersected by the boreholes include fractures parallel to bedding and fractures with variable strike that dip moderately to steeply. Two to three flow zones were detected in each borehole. The flow zones consist of bedding-parallel or steeply dipping fractures or a combination of bedding-parallel fractures and moderately to steeply dipping fractures. About 75 to more than 90 percent of the measured flow under pumped conditions was produced by only one of the flow zones in each borehole.

Ball-and-socket tectonic rotation during the 2013 Mw7.7 Balochistan earthquake

USGS Publications Warehouse

Barnhart, William D.; Hayes, Gavin P.; Briggs, Richard W.; Gold, Ryan D.; Bilham, R.

2014-01-01

The September 2013 Mw7.7 Balochistan earthquake ruptured a ∼200-km-long segment of the curved Hoshab fault in southern Pakistan with 10±0.2 m of peak sinistral and ∼1.7±0.8 m of dip slip. This rupture is unusual because the fault dips 60±15° towards the focus of a small circle centered in northwest Pakistan, and, despite a 30° increase in obliquity along strike, the ratios of strike and dip slip remain relatively uniform. Surface displacements and geodetic and teleseismic source inversions quantify a bilateral rupture that propagated rapidly at shallow depths from a transtensional jog near the northern end of the rupture. Static friction prior to rupture was unusually weak (μ<0.05), and friction may have approached zero during dynamic rupture. Here we show that the inward-dipping Hoshab fault defines the northern rim of a structural unit in southeast Makran that rotates – akin to a 2-D ball-and-socket joint – counter-clockwise in response to India's penetration into the Eurasian plate. This rotation accounts for complexity in the Chaman fault system and, in principle, reduces seismic potential near Karachi; nonetheless, these findings highlight deficiencies in strong ground motion equations and tectonic models that invoke Anderson–Byerlee faulting predictions.

The 2016 central Italy earthquake sequence: surface effects, fault model and triggering scenarios

NASA Astrophysics Data System (ADS)

Chatzipetros, Alexandros; Pavlides, Spyros; Papathanassiou, George; Sboras, Sotiris; Valkaniotis, Sotiris; Georgiadis, George

2017-04-01

The results of fieldwork performed during the 2016 earthquake sequence around the karstic basins of Norcia and La Piana di Castelluccio, at an altitude of 1400 m, on the Monte Vettore (altitude 2476 m) and Vettoretto, as well as the three mapped seismogenic faults, striking NNW-SSW, are presented in this paper. Surface co-seismic ruptures were observed in the Vettore and Vettoretto segment of the fault for several kilometres ( 7 km) in the August earthquakes at high altitudes, and were re-activated and expanded northwards during the October earthquakes. Coseismic ruptures and the neotectonic Mt. Vettore fault zone were modelled in detail using images acquired from specifically planned UAV (drone) flights. Ruptures, typically with displacement of up to 20 cm, were observed after the August event both in the scree and weathered mantle (elluvium), as well as the bedrock, consisting mainly of fragmented carbonate rocks with small tectonic surfaces. These fractures expanded and new ones formed during the October events, typically of displacements of up to 50 cm, although locally higher displacements of up to almost 2 m were observed. Hundreds of rock falls and landslides were mapped through satellite imagery, using pre- and post- earthquake Sentinel 2A images. Several of them were also verified in the field. Based on field mapping results and seismological information, the causative faults were modelled. The model consists of five seismogenic sources, each one associated with a strong event in the sequence. The visualisation of the seismogenic sources follows INGV's DISS standards for the Individual Seismogenic Sources (ISS) layer, while strike, dip and rake of the seismic sources are obtained from selected focal mechanisms. Based on this model, the ground deformation pattern was inferred, using Okada's dislocation solution formulae, which shows that the maximum calculated vertical displacement is 0.53 m. This is in good agreement with the statistical analysis of the observed surface rupture displacement. Stress transfer analysis was also performed in the five modelled seismogenic sources, using seismologically defined parameters. The resulting stress transfer pattern, based on the sequence of events, shows that the causative fault of each event was influenced by loading from the previous ones.

Along-strike slab segmentation under Greece from a 500 km long teleseismic receiver-function swath profile : control on large earthquakes, upper plate motion, and surface morphology

NASA Astrophysics Data System (ADS)

Sachpazi, M.; Laigle, M.; Diaz, J.; Gesret, A.; Charalampakis, M.; Kissling, E. H.; Hirn, A.

2010-12-01

Observations from teleseismic converted waves recorded at 100 sites in Greece from Crete to North Aegean in a 500 km swath along the slab strike during the EU project “Thales was right” allow imaging its top in 3D. Multiscale analysis brings high-resolution to interface imaging at depth which resolved for the first time a thin, oceanic, crust for the slab under southern Greece. This first indication of its large negative buoyancy suggests its roll-back and is consistent with the upper plate trenchward motion with the highest velocities there, as shown by GPS. With respect to up to now subduction zone surveys with receivers deployed along the presumed dip to get a cross-section of the downgoing slab, our swath was instead perpendicular, that is along strike. This was in order to track down lateral changes in slab attitude along the subduction zone, that is a possible segmentation. The expected subduction strike at shallow depth, as approximated by a line from SW of Crete to W of the Ionian Islands is about N 135°E. Instead, the slab top is found along an almost N-S line at several places, at 60-70 km depth. However the slab depth contours deviate from it in-between. Their broad correspondance with the Aegean coastline or extensional domain suggests a possible control on surface morphology, and on upper plate deformation as mirrored in the topography of its crust-mantle boundary. Indeed, this first image recovered with such a high lateral resolution reveals that several slab segments can be defined dipping N 60°E, that is with a N 160 °E strike, and that these are juxtaposed through domains of strong localized variations along-strike that suggest warping or tearing of the slab. Apart their strong bearing on geodynamic reconstructions, and the continental/oceanic nature of the slab fragments, these 3D images reach the high-resolution for their discussion with respect to major earthquakes. The attitude of the slab, the dip of its upper part and its buoyancy force enter the balance controlling the degree of seismic coupling, of the seismogenic interplate fault, as well as its along dip extent as discussed earlier for the Ionian Islands. The segmented nature revealed at depth suggests a possible segmentation of the shallower interplate seismogenic zone. The precise location of the stronger intermediate-depth earthquakes occurred during the deployment appears also related to this deep structural and tectonic control.

Steeply-dipping extension fractures in the Newark basin, New Jersey

USGS Publications Warehouse

Herman, G.C.

2009-01-01

Late Triassic and Early Jurassic bedrock in the Newark basin is pervasively fractured as a result of Mesozoic rifting of the east-central North American continental margin. Tectonic rifting imparted systematic sets of steeply-dipping, en ??chelon, Mode I, extension fractures in basin strata including ordinary joints and veins. These fractures are arranged in transitional-tensional arrays resembling normal dip-slip shear zones. They contributed to crustal stretching, sagging, and eventual faulting of basin rift deposits. Extension fractures display progressive linkage and spatial clustering that probably controlled incipient fault growth. They cluster into three prominent strike groups correlated to early, intermediate, and late-stage tectonic events reflecting about 50- 60?? of counterclockwise rotation of incremental stretching directions. Finite strain analyses show that extension fractures allowed the stretching of basin strata by a few percent, and these fractures impart stratigraphic dips up to a few degrees in directions opposing fracture dips. Fracture groups display three-dimensional spatial variability but consistent geometric relations. Younger fractures locally cut across and terminate against older fractures having more complex vein-cement morphologies and bed-normal folds from stratigraphic compaction. A fourth, youngest group of extension fractures occur sporadically and strike about E-W in obliquely inverted crustal blocks. A geometric analysis of overlapping fracture sets shows how fracture groups result from incremental rotation of an extending tectonic plate, and that old fractures can reactivate with oblique slip components in the contemporary, compressive stress regime. ?? 2008 Elsevier Ltd. All rights reserved.

Dip and anisotropy effects on flow using a vertically skewed model grid.

PubMed

Hoaglund, John R; Pollard, David

2003-01-01

Darcy flow equations relating vertical and bedding-parallel flow to vertical and bedding-parallel gradient components are derived for a skewed Cartesian grid in a vertical plane, correcting for structural dip given the principal hydraulic conductivities in bedding-parallel and bedding-orthogonal directions. Incorrect-minus-correct flow error results are presented for ranges of structural dip (0 < or = theta < or = 90) and gradient directions (0 < or = phi < or = 360). The equations can be coded into ground water models (e.g., MODFLOW) that can use a skewed Cartesian coordinate system to simulate flow in structural terrain with deformed bedding planes. Models modified with these equations will require input arrays of strike and dip, and a solver that can handle off-diagonal hydraulic conductivity terms.

Fault orientations in extensional and conjugate strike-slip environments and their implications

USGS Publications Warehouse

Thatcher, W.; Hill, D.P.

1991-01-01

Seismically active conjugate strike-slip faults in California and Japan typically have mutually orthogonal right- and left-lateral fault planes. Normal-fault dips at earthquake nucleation depths are concentrated between 40?? and 50??. The observed orientations and their strong clustering are surprising, because conventional faulting theory suggests fault initiation with conjugate 60?? and 120?? intersecting planes and 60?? normal-fault dip or fault reactivation with a broad range of permitted orientations. The observations place new constraints on the mechanics of fault initiation, rotation, and evolutionary development. We speculate that the data could be explained by fault rotation into the observed orientations and deactivation for greater rotation or by formation of localized shear zones beneath the brittle-ductile transition in Earth's crust. Initiation as weak frictional faults seems unlikely. -Authors

Possible strain partitioning structure between the Kumano fore-arc basin and the slope of the Nankai Trough accretionary prism

NASA Astrophysics Data System (ADS)

Martin, Kylara M.; Gulick, Sean P. S.; Bangs, Nathan L. B.; Moore, Gregory F.; Ashi, Juichiro; Park, Jin-Oh; Kuramoto, Shin'ichi; Taira, Asahiko

2010-05-01

A 12 km wide, 56 km long, three-dimensional (3-D) seismic volume acquired over the Nankai Trough offshore the Kii Peninsula, Japan, images the accretionary prism, fore-arc basin, and subducting Philippine Sea Plate. We have analyzed an unusual, trench-parallel depression (a "notch") along the seaward edge of the fore-arc Kumano Basin, just landward of the megasplay fault system. This bathymetric feature varies along strike, from a single, steep-walled, ˜3.5 km wide notch in the northeast to a broader, ˜5 km wide zone with several shallower linear depressions in the southwest. Below the notch we found both vertical faults and faults which dip toward the central axis of the depression. Dipping faults appear to have normal offset, consistent with the extension required to form a bathymetric low. Some of these dipping faults may join the central vertical fault(s) at depth, creating apparent flower structures. Offset on the vertical faults is difficult to determine, but the along-strike geometry of these faults makes predominantly normal or thrust motion unlikely. We conclude, therefore, that the notch feature is the bathymetric expression of a transtensional fault system. By considering only the along-strike variability of the megasplay fault, we could not explain a transform feature at the scale of the notch. Strike-slip faulting at the seaward edge of fore-arc basins is also observed in Sumatra and is there attributed to strain partitioning due to oblique convergence. The wedge and décollement strength variations which control the location of the fore-arc basins may therefore play a role in the position where an along-strike component of strain is localized. While the obliquity of convergence in the Nankai Trough is comparatively small (˜15°), we believe it generated the Kumano Basin Edge Fault Zone, which has implications for interpreting local measured stress orientations and suggests potential locations for strain-partitioning-related deformation in other subduction zones.

High-Precision Locations and the Stress Field from Instrumental Seismicity, Moment Tensors, and Short-Period Mechanisms through the Mina Deflection, Central Walker Lane

NASA Astrophysics Data System (ADS)

Ruhl, C. J.; Smith, K. D.

2012-12-01

The Mina Deflection (MD) region of the central Walker Lane of eastern California and western Nevada, is a complex zone of northeast-trending normal, and primarily left-lateral strike-slip to oblique-slip faulting that separates the Southern Walker Lane (SWL) from a series of east-tilted normal fault blocks in the Central Walker Lane (CWL) (Faulds and Henry, 2008; Surpless, 2008). The MD accommodates the transfer of right-lateral strike-slip motion from northwest-striking faults in the SWL to a series of left-stepping northwest-striking right-lateral strike-slip faults in the CWL, east of the Wassuk Range near Hawthorne, NV. The ~50 km wide ~80 km long right-step is a distinct transition in regional physiography that has been attributed to strain accommodation through pre-Cenozoic lithospheric structures. Several slip transfer mechanisms have been proposed within the MD, from clockwise rotation of high-angle fault blocks (Wesnousky, 2005), to low-angle displacement within the Silver Peak-Lone Mountain complex (Oldow et al., 2001), and curved fault arrays associated with localized basins and tectonic depressions (Ferranti et al., 2009). The region has been a regular source of M4+ events, the most recent being an extended sequence that included twenty-seven M 3.5+ earthquakes (largest event M 4.6) south of Hawthorne in 2011. These earthquakes (< 5 km depth) define shallow W-dipping (dip ~56°) and NW-dipping (dip ~70°) normal faulting constrained by moment tensor (MT) solutions and earthquake relocations. Temporary stations deployed in the source area provide good control. A distributed sequence in 2004, between Queen Valley and Mono Lake, primarily associated with the Huntoon Valley fault, included three M 5+ left-lateral strike-slip faulting events. A 1997 sequence in northern Fish Lake Valley (east of the White Mountains), with mainshock Mw 5.3 (Ichinose et al., 2003), also showed high-angle northeast-striking left-lateral strike-slip motion. Historical events include the 1934 M 6.5 Excelsior Mountains event south of Mina, NV, and the 1932 M 7.1 Cedar Mountains earthquake east of the Pilot Mountains. Another persistent feature in the seismicity is an ~40 km long arcuate distribution of activity extending from approximately Queen Valley, north of the White Mountains, to Mono Lake that appears to reflect a southwestern boundary to northeast-striking structures in the MD. Here we develop high-precision relocations of instrumental seismicity in the MD from 1984 through 2012, including relocations of the 2004 sequence, and account for the historical seismic record. MT solutions from published reports and computed from recent M 3.5+ earthquakes as well as available and developed short-period focal mechanisms are compiled to evaluate the stress field to assess mechanisms of slip accommodation. Based on the complex distribution of fault orientations, the stress field varies locally northward from the SWL throughout the MD; however, in many cases, fault plane alignments can be isolated from high-precision locations, providing better constraints on stress and slip orientations.

Seismological constraints on the down-dip shape of normal faults

NASA Astrophysics Data System (ADS)

Reynolds, Kirsty; Copley, Alex

2018-04-01

We present a seismological technique for determining the down-dip shape of seismogenic normal faults. Synthetic models of non-planar source geometries reveal the important signals in teleseismic P and SH waveforms that are diagnostic of down-dip curvature. In particular, along-strike SH waveforms are the most sensitive to variations in source geometry, and have significantly more complex and larger-amplitude waveforms for curved source geometries than planar ones. We present the results of our forward-modelling technique for 13 earthquakes. Most continental normal-faulting earthquakes that rupture through the full seismogenic layer are planar and have dips of 30°-60°. There is evidence for faults with a listric shape from some of the earthquakes occurring in two regions; Tibet and East Africa. These ruptures occurred on antithetic faults, or minor faults within the hanging walls of the rifts affected, which may suggest a reason for the down-dip curvature. For these earthquakes, the change in dip across the seismogenic part of the fault plane is ≤30°.

SDM - A geodetic inversion code incorporating with layered crust structure and curved fault geometry

NASA Astrophysics Data System (ADS)

Wang, Rongjiang; Diao, Faqi; Hoechner, Andreas

2013-04-01

Currently, inversion of geodetic data for earthquake fault ruptures is most based on a uniform half-space earth model because of its closed-form Green's functions. However, the layered structure of the crust can significantly affect the inversion results. The other effect, which is often neglected, is related to the curved fault geometry. Especially, fault planes of most mega thrust earthquakes vary their dip angle with depth from a few to several tens of degrees. Also the strike directions of many large earthquakes are variable. For simplicity, such curved fault geometry is usually approximated to several connected rectangular segments, leading to an artificial loss of the slip resolution and data fit. In this presentation, we introduce a free FORTRAN code incorporating with the layered crust structure and curved fault geometry in a user-friendly way. The name SDM stands for Steepest Descent Method, an iterative algorithm used for the constrained least-squares optimization. The new code can be used for joint inversion of different datasets, which may include systematic offsets, as most geodetic data are obtained from relative measurements. These offsets are treated as unknowns to be determined simultaneously with the slip unknowns. In addition, a-priori and physical constraints are considered. The a-priori constraint includes the upper limit of the slip amplitude and the variation range of the slip direction (rake angle) defined by the user. The physical constraint is needed to obtain a smooth slip model, which is realized through a smoothing term to be minimized with the misfit to data. In difference to most previous inversion codes, the smoothing can be optionally applied to slip or stress-drop. The code works with an input file, a well-documented example of which is provided with the source code. Application examples are demonstrated.

Rapid Regional Centroid Solutions

NASA Astrophysics Data System (ADS)

Wei, S.; Zhan, Z.; Luo, Y.; Ni, S.; Chen, Y.; Helmberger, D. V.

2009-12-01

The 2008 Wells Nevada Earthquake was recorded by 164 broadband USArray stations within a distance of 550km (5 degrees) with all azimuths uniformly sampled. To establish the source parameters, we applied the Cut and Paste (CAP) code to all the stations to obtain a mechanism (strike/dip/rake=35/41/-85) at a depth of 9km and Mw=5.9. Surface wave shifts range from -8s to 8s which are in good agreement with ambient seismic noise (ASN) predictions. Here we use this data set to test the accuracy of the number of stations needed to obtain adequate solutions (position of the compressional and tension axis) for mechanism. The stations were chosen at random where combinations of Pnl and surface waves were used to establish mechanism and depth. If the event is bracketed by two stations, we obtain an accurate magnitude with good solutions about 80% of the trials. Complete solutions from four stations or Pnl from 10 stations prove reliable in nearly all situations. We also explore the use of this dataset in locating the event using a combination of surface wave travel times and/or the full waveform inversion (CAPloc) that uses the CAP shifts to refine locations. If the mechanism is known (fixed) only a few stations is needed to locate an event to within 5km if date is available at less than 150km. In contrast, surface wave travel times (calibrated to within one second) produce amazing accurate locations with only 6 stations reasonably distributed. It appears this approach is easily automated as suggested by Scrivner and Helmberger (1995) who discussed travel times of Pnl and surface waves and the evolving of source accuracy as the various phases arrive.

Joint Source Location and Focal Mechanism Inversion: efficiency, accuracy and applications

NASA Astrophysics Data System (ADS)

Liang, C.; Yu, Y.

2017-12-01

The analysis of induced seismicity has become a common practice to evaluate the results of hydraulic fracturing treatment. Liang et al (2016) proposed a joint Source Scanning Algorithms (jSSA for short) to obtain microseismic events and focal mechanisms simultaneously. The jSSA is superior over traditional SSA in many aspects, but the computation cost is too significant to be applied in real time monitoring. In this study, we have developed several scanning schemas to reduce computation time. A multi-stage scanning schema is proved to be able to improve the efficiency significantly while also retain its accuracy. A series of tests have been carried out by using both real field data and synthetic data to evaluate the accuracy of the method and its dependence on noise level, source depths, focal mechanisms and other factors. The surface-based arrays have better constraints on horizontal location errors (<20m) and angular errors of P axes (within 10 degree, for S/N>0.5). For sources with varying rakes, dips, strikes and depths, the errors are mostly controlled by the partition of positive and negative polarities in different quadrants. More evenly partitioned polarities in different quadrants yield better results in both locations and focal mechanisms. Nevertheless, even with bad resolutions for some FMs, the optimized jSSA method can still improve location accuracies significantly. Based on much more densely distributed events and focal mechanisms, a gridded stress inversion is conducted to get a evenly distributed stress field. The full potential of the jSSA has yet to be explored in different directions, especially in earthquake seismology as seismic array becoming incleasingly dense.

On The Computation Of The Best-fit Okada-type Tsunami Source

NASA Astrophysics Data System (ADS)

Miranda, J. M. A.; Luis, J. M. F.; Baptista, M. A.

2017-12-01

The forward simulation of earthquake-induced tsunamis usually assumes that the initial sea surface elevation mimics the co-seismic deformation of the ocean bottom described by a simple "Okada-type" source (rectangular fault with constant slip in a homogeneous elastic half space). This approach is highly effective, in particular in far-field conditions. With this assumption, and a given set of tsunami waveforms recorded by deep sea pressure sensors and (or) coastal tide stations it is possible to deduce the set of parameters of the Okada-type solution that best fits a set of sea level observations. To do this, we build a "space of possible tsunami sources-solution space". Each solution consists of a combination of parameters: earthquake magnitude, length, width, slip, depth and angles - strike, rake, and dip. To constrain the number of possible solutions we use the earthquake parameters defined by seismology and establish a range of possible values for each parameter. We select the "best Okada source" by comparison of the results of direct tsunami modeling using the solution space of tsunami sources. However, direct tsunami modeling is a time-consuming process for the whole solution space. To overcome this problem, we use a precomputed database of Empirical Green Functions to compute the tsunami waveforms resulting from unit water sources and search which one best matches the observations. In this study, we use as a test case the Solomon Islands tsunami of 6 February 2013 caused by a magnitude 8.0 earthquake. The "best Okada" source is the solution that best matches the tsunami recorded at six DART stations in the area. We discuss the differences between the initial seismic solution and the final one obtained from tsunami data This publication received funding of FCT-project UID/GEO/50019/2013-Instituto Dom Luiz.

Constraints on the long-period moment-dip tradeoff for the Tohoku earthquake

USGS Publications Warehouse

Tsai, Victor C.; Hayes, Gavin P.; Duputel, Zacharie

2011-01-01

Since the work of Kanamori and Given (1981), it has been recognized that shallow, pure dip-slip earthquakes excite long-period surface waves such that it is difficult to independently constrain the moment (M0) and the dip (δ) of the source mechanism, with only the product M0 sin(2δ) being well constrained. Because of this, it is often assumed that the primary discrepancies between the moments of shallow, thrust earthquakes are due to this moment-dip tradeoff. In this work, we quantify how severe this moment-dip tradeoff is depending on the depth of the earthquake, the station distribution, the closeness of the mechanism to pure dip-slip, and the quality of the data. We find that both long-period Rayleigh and Love wave modes have moment-dip resolving power even for shallow events, especially when stations are close to certain azimuths with respect to mechanism strike and when source depth is well determined. We apply these results to USGS W phase inversions of the recent M9.0 Tohoku, Japan earthquake and estimate the likely uncertainties in dip and moment associated with the moment- dip tradeoff. After discussing some of the important sources of moment and dip error, we suggest two methods for potentially improving this uncertainty.

Constraints on the long-period moment-dip tradeoff for the Tohoku earthquake

USGS Publications Warehouse

Tsai, V.C.; Hayes, G.P.; Duputel, Z.

2011-01-01

Since the work of Kanamori and Given (1981), it has been recognized that shallow, pure dip-slip earthquakes excite long-period surface waves such that it is difficult to independently constrain the moment (M0) and the dip (??) of the source mechanism, with only the product M0 sin(2??) being well constrained. Because of this, it is often assumed that the primary discrepancies between the moments of shallow, thrust earthquakes are due to this moment-dip tradeoff. In this work, we quantify how severe this moment-dip tradeoff is depending on the depth of the earthquake, the station distribution, the closeness of the mechanism to pure dip-slip, and the quality of the data. We find that both long-period Rayleigh and Love wave modes have moment-dip resolving power even for shallow events, especially when stations are close to certain azimuths with respect to mechanism strike and when source depth is well determined. We apply these results to USGS W phase inversions of the recent M9.0 Tohoku, Japan earthquake and estimate the likely uncertainties in dip and moment associated with the moment-dip tradeoff. After discussing some of the important sources of moment and dip error, we suggest two methods for potentially improving this uncertainty. Copyright 2011 by the American Geophysical Union.

3D Model of the Neal Hot Springs Geothermal Area

DOE Data Explorer

Faulds, James E.

2013-12-31

The Neal Hot Springs geothermal system lies in a left-step in a north-striking, west-dipping normal fault system, consisting of the Neal Fault to the south and the Sugarloaf Butte Fault to the north (Edwards, 2013). The Neal Hot Springs 3D geologic model consists of 104 faults and 13 stratigraphic units. The stratigraphy is sub-horizontal to dipping <10 degrees and there is no predominant dip-direction. Geothermal production is exclusively from the Neal Fault south of, and within the step-over, while geothermal injection is into both the Neal Fault to the south of the step-over and faults within the step-over.

An Iterative Travel Time Inversion and Waveform Modeling Method to Determine the Crust Structure and Focal Mechanism: Case Study of 2015 Alxa Left Banner Ms5.8 Earthquake

NASA Astrophysics Data System (ADS)

Song, C.; Ge, Z.

2017-12-01

The boundary region between Alxa Block and Ordos Block is an area of stress concentration with strong seismicity and frequent small earthquakes. However, the knowledge of this area is limited since only a few seismic stations were deployed in this area. The 2015 Ms5.8 Alxa Left Banner Earthquake on April 15 is the largest one occurred in the surroundings since the 1976 Ms6.2 Bayinmuren Earthquake. Abundant stations built in the northern part of Chinese North-South Seismic Belt recorded this event sequence well within short distance, which provides us a great opportunity to carry out studies. We use these data to obtain a mean 1-D layered velocity structure via iterative inversion based on both travel time and waveform misfits. Then we use the travel time difference between data and synthetic seismograms to relocate the epicenter. Finally we invert the best double-couple focal mechanism and centroid depths of the source. As the result, the source is located at (39.7027° N, 106.4207° E) with a depth of 18 km and Mw 5.28. Nodal plane Ⅰ has strike 86°, dip angle 90° and slip angle -3°, while plane Ⅱ has strike 176°, dip angle 87° and slip angle 180°. Considering the dynamic structure of regional fault zone, we believe this earthquake is caused by a nearly pure left-lateral strike-slip fault with nodal plane Ⅰ being the fault plane. The seismogenic structure is likely to be an E-W striking buried fault nearby. There develops several groups of NE, NEE and E-W striking faults in Jilantai tectonic zone, parts of which have been verified by geophysical investigations. But we still know little about the dynamic nature of them. From our study, the corresponding fault of this event may indicate all groups of faults with same E-W strike has the common character of large-dip left-lateral strike-slip. Moreover, there may be some buried faults being newly born or not found yet. These results could be an important supplement to the future research of seismicity and modern fault zone structure.

Analyzing structural variations along strike in a deep-water thrust belt

NASA Astrophysics Data System (ADS)

Totake, Yukitsugu; Butler, Robert W. H.; Bond, Clare E.; Aziz, Aznan

2018-03-01

We characterize a deep-water fold-thrust arrays imaged by a high-resolution 3D seismic dataset in the offshore NW Borneo, Malaysia, to understand the kinematics behind spatial arrangement of structural variations throughout the fold-thrust system. The seismic volume used covers two sub-parallel fold trains associated with a series of fore-thrusts and back-thrusts. We measured fault heave, shortening value, fold geometries (forelimb dip, interlimb angle and crest depth) along strike in individual fold trains. Heave plot on strike projection allows to identify individual thrust segments showing semi-elliptical to triangular to bimodal patterns, and linkages of these segments. The linkage sites are marked by local minima in cumulative heave. These local heave minima are compensated by additional structures, such as small imbricate thrusts and tight folds indicated by large forelimb dip and small interlimb angle. Complementary profiles of the shortening amount for the two fold trains result in smoother gradient of total shortening across the structures. We interpret this reflects kinematic interaction between two fold-thrust trains. This type of along-strike variation analysis provides comprehensive understanding of a fold-thrust system and may provide an interpretative strategy for inferring the presence of complex multiple faults in less well-imaged parts of seismic volumes.

Strike-slip earthquakes can also be detected in the ionosphere

NASA Astrophysics Data System (ADS)

Astafyeva, Elvira; Rolland, Lucie M.; Sladen, Anthony

2014-11-01

It is generally assumed that co-seismic ionospheric disturbances are generated by large vertical static displacements of the ground during an earthquake. Consequently, it is expected that co-seismic ionospheric disturbances are only observable after earthquakes with a significant dip-slip component. Therefore, earthquakes dominated by strike-slip motion, i.e. with very little vertical co-seismic component, are not expected to generate ionospheric perturbations. In this work, we use total electron content (TEC) measurements from ground-based GNSS-receivers to study ionospheric response to six recent largest strike-slip earthquakes: the Mw7.8 Kunlun earthquake of 14 November 2001, the Mw8.1 Macquarie earthquake of 23 December 2004, the Sumatra earthquake doublet, Mw8.6 and Mw8.2, of 11 April 2012, the Mw7.7 Balochistan earthquake of 24 September 2013 and the Mw 7.7 Scotia Sea earthquake of 17 November 2013. We show that large strike-slip earthquakes generate large ionospheric perturbations of amplitude comparable with those induced by dip-slip earthquakes of equivalent magnitude. We consider that in the absence of significant vertical static co-seismic displacements of the ground, other seismological parameters (primarily the magnitude of co-seismic horizontal displacements, seismic fault dimensions, seismic slip) may contribute in generation of large-amplitude ionospheric perturbations.

9. VIEW OF THE TRASH RAKES, TRASH RAKE GATELIFTING MECHANISM, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

9. VIEW OF THE TRASH RAKES, TRASH RAKE GATE-LIFTING MECHANISM, AND SHED ROOF (REMOVED AUTUMN OF 1996), WITH TRASH LOG LIFTING MECHANISM IN FOREGROUND, LOOKING WEST. - Washington Water Power Company Post Falls Power Plant, Middle Channel Powerhouse & Dam, West of intersection of Spokane & Fourth Streets, Post Falls, Kootenai County, ID

The evaluation of a rake method to quantify submersed vegetation in the Upper Mississippi River

USGS Publications Warehouse

Yin, Yao; Kreiling, Rebecca M.

2011-01-01

A long-handled, double-headed garden rake was used to collect submersed aquatic vegetation (SAV) and compared to in-boat visual inspection to record species presence at 67 individual sites. Six rake subsamples were taken at each site and a rake density rating was given to each species collected in the subsamples. Presence at the site, frequency of occurrence in the six rake samples, and additive density rating (the sum of the six rake density ratings) were quantified for each species at each site. The validity of the indices was tested against biomass data collected by clipping all remaining vegetation from the 67 sites. In the turbid water of the Mississippi River, visual inspection of SAV from boats was ineffective with only 27% of the species detected, while raking retrieved on average 70% of the total number of submersed species in the 67 sites. Presence of species at individual sites was correlated with biomass from Stuckenia pectinata, while frequency of occurrence and additive density rating were correlated with biomass for species with greater than 21 g of total biomass from all sites. The efficiency of the rake to collect biomass varied among species; only 18% of total biomass was captured via raking the site six times. Additive density rating as an index of abundance can be used to detect temporal changes in the same water body; however, cross-species comparison is not encouraged unless the efficiency of the rake has been determined for each species being compared.

Rupture process of the 2009 L'Aquila, central Italy, earthquake, from the separate and joint inversion of Strong Motion, GPS and DInSAR data.

NASA Astrophysics Data System (ADS)

Cirella, A.; Piatanesi, A.; Tinti, E.; Chini, M.; Cocco, M.

2012-04-01

In this study, we investigate the rupture history of the April 6th 2009 (Mw 6.1) L'Aquila normal faulting earthquake by using a nonlinear inversion of strong motion, GPS and DInSAR data. We use a two-stage non-linear inversion technique. During the first stage, an algorithm based on the heat-bath simulated annealing generates an ensemble of models that efficiently sample the good data-fitting regions of parameter space. In the second stage the algorithm performs a statistical analysis of the ensemble providing us the best-fitting model, the average model, the associated standard deviation and coefficient of variation. This technique, rather than simply looking at the best model, extracts the most stable features of the earthquake rupture that are consistent with the data and gives an estimate of the variability of each model parameter. The application to the 2009 L'Aquila main-shock shows that both the separate and joint inversion solutions reveal a complex rupture process and a heterogeneous slip distribution. Slip is concentrated in two main asperities: a smaller shallow patch of slip located up-dip from the hypocenter and a second deeper and larger asperity located southeastward along strike direction. The key feature of the source process emerging from our inverted models concerns the rupture history, which is characterized by two distinct stages. The first stage begins with rupture initiation and with a modest moment release lasting nearly 0.9 seconds, which is followed by a sharp increase in slip velocity and rupture speed located 2 km up-dip from the nucleation. During this first stage the rupture front propagated up-dip from the hypocenter at relatively high (˜ 4.0 km/s), but still sub-shear, rupture velocity. The second stage starts nearly 2 seconds after nucleation and it is characterized by the along strike rupture propagation. The largest and deeper asperity fails during this stage of the rupture process. The rupture velocity is larger in the up-dip than in the along-strike direction. The up-dip and along-strike rupture propagation are separated in time and associated with a Mode II and a Mode III crack, respectively. Our results show that the 2009 L'Aquila earthquake featured a very complex rupture, with strong spatial and temporal heterogeneities suggesting a strong frictional and/or structural control of the rupture process.

Structural Controls of Neal Hot Springs Geothermal Field, Malhuer County, Oregon

NASA Astrophysics Data System (ADS)

Edwards, J. H.; Faulds, J. E.

2012-12-01

Detailed mapping (1:24,000) of the Neal Hot Springs area (90 km2) in eastern Oregon is part of a larger study of geothermal systems in the Basin and Range, which focuses on the structural controls of geothermal activity. The study area lies within the intersection of two regional grabens, the middle-late Miocene, N-striking, Oregon-Idaho graben and younger late Miocene to Holocene, NW-striking, western Snake River Plain graben. The geothermal field is marked by Neal Hot Springs, which effuse from opaline sinter mounds just north of Bully Creek. Wells producing geothermal fluids, with temperatures at 138°C, intersect a major, W-dipping, NNW-striking, high-angle normal fault at depths of 850-915 m. Displacement along this structure dies southward, with likely horse-tailing, which commonly produces high fracture density and a zone of high permeability conducive for channeling hydrothermal fluids. Mapping reveals that the geothermal resource lies within a local, left step-over. 'Hard-linkage' between strands of the left-stepping normal fault, revealed through a study of well chips and well logs, occurs through two concealed structures. Both are W-striking faults, with one that runs parallel to Cottonwood Creek and one 0.5 km N of the creek. Injection wells intersect these two transverse structures within the step-over. Stepping and displacement continue to the NW of the known geothermal field, along W-dipping, N-striking faults that cut lower to middle Miocene Hog Creek Formation, consisting of silicic and mafic volcanic rocks. These N-striking faults were likely initiated during initial Oregon-Idaho graben subsidence (15.3-15.1 Ma), with continued development through late Miocene. Bully Creek Formation deposits, middle to upper Miocene lacustrine and pyroclastic rocks, concomitantly filled the sub half-grabens, and they dip gently to moderately eastward. Younger, western Snake River Plain deposits, upper Miocene to Pliocene fluvial, lacustrine, and pyroclastic rocks, show various dip directions and gentle tilting. Extensive alluvial fan cover hinders collection of fault kinematic data, which coupled with limited regional seismicity, precludes careful calculation of local stress field orientations. However, the proximity of Neal (4 km) to the active, N- to NW-striking, oblique-normal slip Cottonwood Mountain fault and active hot springs (~90°C), opaline sinter mounds, and geothermal fluid flow at Neal suggest that the geothermal field lies within a reactived (Quaternary), southward-terminating, left-stepping, fault zone, which probably accommodates oblique-slip with a dominant normal component. Sugarloaf Butte (completely silicified and replaced) lies within a left step of this fault zone, ~5 km of Neal Hot Springs and is possibly related to the evolution of the geothermal system. Epithermal deposits and argillic to propylitic alteration in other nearby areas (e.g., Hope Butte, ~3 Ma, 5 km N) indicate previous geothermal activity.

Geological-Seismological Evaluation of Earthquake Hazards at Franklin Falls Damsite, New Hampshire.

DTIC Science & Technology

1986-09-01

8217 the Corps records have been analyzed by Chang (1983) , Toksoz (1982) and Sauber (in press) (Table" 3, Fig. 6). The instrument at Seabrook was just...and others, 1983, Sauber , in press). A strike-slip motion was interpreted from the *. data, although two stations did not fit. The attitudes given by...the two possible solutions given by Sauber (in press) and using her dips are north 230 east, 680 southeast dip, left-lateral motion and north 700 west

Does raking basal duff affect tree growth rates or mortality?

Treesearch

Erin Noonan-Wright; Sharon M. Hood; Danny R. Cluck

2010-01-01

Mortality and reduced growth rates due to raking accumulated basal duff were evaluated for old, large-diameter ponderosa and Jeffrey pine trees on the Lassen National Forest, California. No fire treatments were included to isolate the effect of raking from fire. Trees were monitored annually for 5 years after the raking treatment for mortality and then cored to measure...

Semiempirical method of determining flow coefficients for pitot rake mass flow rate measurements

NASA Technical Reports Server (NTRS)

Trefny, C. J.

1985-01-01

Flow coefficients applicable to area-weighted pitot rake mass flow rate measurements are presented for fully developed, turbulent flow in an annulus. A turbulent velocity profile is generated semiempirically for a given annulus hub-to-tip radius ratio and integrated numerically to determine the ideal mass flow rate. The calculated velocities at each probe location are then summed, and the flow rate as indicated by the rake is obtained. The flow coefficient to be used with the particular rake geometry is subsequently obtained by dividing the ideal flow rate by the rake-indicated flow rate. Flow coefficients ranged from 0.903 for one probe placed at a radius dividing two equal areas to 0.984 for a 10-probe area-weighted rake. Flow coefficients were not a strong function of annulus hub-to-tip radius ratio for rakes with three or more probes. The semiempirical method used to generate the turbulent velocity profiles is described in detail.

Raking it in: the impact of enculturation on chimpanzee tool use.

PubMed

Furlong, E E; Boose, K J; Boysen, S T

2008-01-01

Recent evidence for different tool kits, proposed to be based upon culture-like transmission, have been observed across different chimpanzee communities across Western Africa. In light of these findings, the reported failures by seven captive juvenile chimpanzees tested with 27 tool use tasks (Povinelli 2000) seem enigmatic. Here we report successful performance by a group of nine captive, enculturated chimpanzees, and limited success by a group of six semi-enculturated chimpanzees, on two of the Povinelli tasks, the Flimsy Tool task, and the Hybrid Tool task. All chimpanzees were presented with a rake with a flimsy head and a second rake with a rigid head, either of which could be used to attempt to retrieve a food reward that was out of reach. The rigid rake was constructed such that it had the necessary functional features to permit successful retrieval, while the flimsy rake did not. Both chimpanzee groups in the present experiment selected the functional rigid tool correctly to use during the Flimsy Tool task. All animals were then presented with two "hybrid rakes" A and B, with one half of each rake head constructed from flimsy, non-functional fabric, and the other half of the head was made of wood. Food rewards were placed in front of the rigid side of Rake A and the flimsy side of Rake B. To be successful, the chimps needed to choose the rake that had the reward in front of the rigid side of the rake head. The fully enculturated animals were successful in selecting the functional rake, while the semi-enculturated subjects chose randomly between the two hybrid tools. Compared with findings from Povinelli, whose non-enculturated animals failed both tasks, our results demonstrate that chimpanzees reared under conditions of semi-enculturation could learn to discriminate correctly the necessary tool through trial-and-error during the Flimsy Tool task, but were unable to recognize the functional relationship necessary for retrieving the reward with the "hybrid" rake. In contrast, the enculturated chimpanzees were correct in their choices during both the Flimsy Tool and the Hybrid Tool tasks. These results provide the first empirical evidence for the differential effects of enculturation on subsequent tool use capacities in captive chimpanzees.

Delineation of areas having elevated electrical conductivity, orientation and characterization of bedrock fractures, and occurrence of groundwater discharge to surface water at the U.S. Environmental Protection Agency Barite Hill/Nevada Goldfields Superfund site near McCormick, South Carolina

USGS Publications Warehouse

Chapman, Melinda J.; Huffman, Brad A.; McSwain, Kristen Bukowski

2015-07-16

Bedrock properties were characterized from borehole geophysical logs collected from three open-borehole bedrock wells. The mean strike azimuth of the borehole foliation data measured in bedrock well IR-1 was 221° (N. 41° E.), and the mean dip angle was 78° to the northwest. Dominant strike azimuth orientations of primary fractures measured in three boreholes were from 210° to 250° (N. 30° E. to N. 70° E.) with a mean dip of 68° northwest. Transmissivity estimates interpreted from the heat-pulse flowmeter data from bedrock well IR-1 were about 69 feet squared per day, and the radius of influence was estimated at about 640 feet.

Dynamic rupture modeling of the transition from thrust to strike-slip motion in the 2002 Denali fault earthquake, Alaska

USGS Publications Warehouse

Aagaard, Brad T.; Anderson, G.; Hudnut, K.W.

2004-01-01

We use three-dimensional dynamic (spontaneous) rupture models to investigate the nearly simultaneous ruptures of the Susitna Glacier thrust fault and the Denali strike-slip fault. With the 1957 Mw 8.3 Gobi-Altay, Mongolia, earthquake as the only other well-documented case of significant, nearly simultaneous rupture of both thrust and strike-slip faults, this feature of the 2002 Denali fault earthquake provides a unique opportunity to investigate the mechanisms responsible for development of these large, complex events. We find that the geometry of the faults and the orientation of the regional stress field caused slip on the Susitna Glacier fault to load the Denali fault. Several different stress orientations with oblique right-lateral motion on the Susitna Glacier fault replicate the triggering of rupture on the Denali fault about 10 sec after the rupture nucleates on the Susitna Glacier fault. However, generating slip directions compatible with measured surface offsets and kinematic source inversions requires perturbing the stress orientation from that determined with focal mechanisms of regional events. Adjusting the vertical component of the principal stress tensor for the regional stress field so that it is more consistent with a mixture of strike-slip and reverse faulting significantly improves the fit of the slip-rake angles to the data. Rotating the maximum horizontal compressive stress direction westward appears to improve the fit even further.

Bayesian inference and interpretation of centroid moment tensors of the 2016 Kumamoto earthquake sequence, Kyushu, Japan

NASA Astrophysics Data System (ADS)

Hallo, Miroslav; Asano, Kimiyuki; Gallovič, František

2017-09-01

On April 16, 2016, Kumamoto prefecture in Kyushu region, Japan, was devastated by a shallow M JMA7.3 earthquake. The series of foreshocks started by M JMA6.5 foreshock 28 h before the mainshock. They have originated in Hinagu fault zone intersecting the mainshock Futagawa fault zone; hence, the tectonic background for this earthquake sequence is rather complex. Here we infer centroid moment tensors (CMTs) for 11 events with M JMA between 4.8 and 6.5, using strong motion records of the K-NET, KiK-net and F-net networks. We use upgraded Bayesian full-waveform inversion code ISOLA-ObsPy, which takes into account uncertainty of the velocity model. Such an approach allows us to reliably assess uncertainty of the CMT parameters including the centroid position. The solutions show significant systematic spatial and temporal variations throughout the sequence. Foreshocks are right-lateral steeply dipping strike-slip events connected to the NE-SW shear zone. Those located close to the intersection of the Hinagu and Futagawa fault zones are dipping slightly to ESE, while those in the southern area are dipping to WNW. Contrarily, aftershocks are mostly normal dip-slip events, being related to the N-S extensional tectonic regime. Most of the deviatoric moment tensors contain only minor CLVD component, which can be attributed to the velocity model uncertainty. Nevertheless, two of the CMTs involve a significant CLVD component, which may reflect complex rupture process. Decomposition of those moment tensors into two pure shear moment tensors suggests combined right-lateral strike-slip and normal dip-slip mechanisms, consistent with the tectonic settings of the intersection of the Hinagu and Futagawa fault zones.[Figure not available: see fulltext.

Impact of raking and bioturbation-mediated ecological manipulation on sediment-water phosphorus diagenesis: a mesocosm study supported with radioactive signature.

PubMed

Biswas, Jayanta K; Hazra, Saumen; Majumdar, Jayjit; Mandal, Sushil K; Shaheen, Sabry M; Sarkar, Santosh K; Meissner, Ralph; Meers, Erik; Rinklebe, Jörg

2017-12-01

The study examined the impact of raking and fish bioturbation on modulating phosphorus (P) concentrations in the water and sediment under different trophic conditions. An outdoor experiment was set to monitor physicochemical and microbiological parameters of water and sediment influencing P diagenesis. A pilot study with radioactive 32 P was also performed under the agency of raking and bacteria (Bacillus sp.). Raking was more effective in release of P under unfertilized conditions by significantly enhancing orthophosphate (35%) and soluble reactive phosphate (31.8%) over respective controls. Bioturbation increased total and available P in sediments significantly as compared to control. The rates of increase were higher in the unfertilized conditions (17.6-28.4% for total P and 12.2 to 23.2% for available P) than the fertilized ones (6.5-12.4% for total P and 9.1 to 15% for available P). The combined effects of raking and bioturbation on orthophosphate and soluble reactive phosphate were also stronger under unfertilized state (54.5 and 81.8%) than fertilized ones (50 and 70%). The tracer signature showed that coupled action of introduced bacteria and repeated raking resulted in 59.2, 23 and 16% higher counts of radioactive P than the treatments receiving raking once, repeated raking and bacteria inoculation, respectively. Raking alone or in sync with bioturbation exerted pronounced impact on P diagenesis through induction of coupled mineralization and nutrient release. It has significant implication for performing regular raking of fish-farm sediments and manipulation of bottom-grazing fish to regulate mineralization of organic matter and release of obnoxious gases from the system. Further, they synergistically can enhance the buffering capacity against organic overload and help to maintain aquatic ecosystem health.

Crustal deformation associated with east Mediterranean strike-slip earthquakes: The 8 June 2008 Movri (NW Peloponnese), Greece, earthquake (M w6.4)

NASA Astrophysics Data System (ADS)

Papadopoulos, Gerassimos A.; Karastathis, Vassilis; Kontoes, Charalambos; Charalampakis, Marinos; Fokaefs, Anna; Papoutsis, Ioannis

2010-09-01

The 2008 mainshock ( Mw = 6.4) was the first modern, strong strike-slip earthquake in the Greek mainland. The fault strikes NE-SW, dips ˜ 85°NW while the motion was right-lateral with small reverse component. Historical seismicity showed no evidence that the fault ruptured in the last 300 years. For rectangular planar fault we estimated fault dimensions from aftershock locations. Dimensions are consistent with that a buried fault was activated, lateral expansion occurred only along length and the rupture stopped at depth ˜ 20 km implying that more rupture along length was favoured. We concluded that no major asperities remained unbroken and that the aftershock activity was dominated rather by creeping mechanism than by the presence of locked patches. For Mo = 4.56 × 10 25 dyn cm we calculated average slip of 76 cm and stress drop Δσ ˜ 13 bars. This Δσ is high for Greek strike-slip earthquakes, due rather to increased rigidity because of the relatively long recurrence ( Τ > 300 years) of strong earthquakes in the fault, than to high slip. Values of Δσ and Τ indicated that the fault is neither a typical strong nor a typical weak fault. Dislocation modeling of a buried fault showed uplift of ˜ 8.0 cm in Kato Achaia ( Δ ˜ 20 km) at the hanging wall of the reverse fault component. DInSAR analysis detected co-seismic motion only in Kato Achaia where interferogram fringes pattern showed vertical displacement from 3.0 to 6.0 cm. From field-surveys we estimated maximum intensity of VIII in Kato Achaia. The most important liquefaction spots were also observed there. These observations are attributable neither to surface fault-breaks nor to site effects but possibly to high ground acceleration due to the co-seismic uplift. The causal association between displacement and earthquake damage in the hanging wall described for dip-slip faults in Taiwan, Greece and elsewhere, becomes possible also for strike-slip faults with dip-slip component, as the 2008 earthquake.

Orientations of Pre-existing Structures along the Scarp of the Bilila-Mtakataka Fault in the Central Malawi Rift.

NASA Astrophysics Data System (ADS)

Elifritz, E. A.; Johnson, S.; Beresh, S. C. M.; Mendez, K.; Mynatt, W. G.; Mayle, M.; Laó-Dávila, D. A.; Atekwana, E. A.; Chindandali, P. R. N.; Chisenga, C.; Gondwe, S.; Mkumbwa, M.; Kalindekafe, L.; Kalaguluka, D.; Salima, J.

2017-12-01

The NW-SE Bilila-Mtakataka Fault is suggested to be 100 km in length and is located in the Malawi Rift, a portion of the magma-poor Western Branch of the East African Rift System. This fault is exposed south of Lake Malawi and occurs close to the epicenter of the 1989 6.2 magnitude Salima Earthquake. Moreover, it traverses rocks with inherited Precambrian fabrics that may control the modern rifting process. The effect of the orientation of the pre-existing fabric on the formation of this potentially seismogenic fault has not been well studied. In this project, we measured the older foliations, dikes, and joints in addition to younger faults and striations to understand how the active faulting of the Bilila-Mtakataka Fault is affected by the older fabric. The Fault is divided into 5 segments and 4 linkage zones. All four linkage zones were studied in detail and a Brunton compass was used to determine orientations of structures. The linkage zone between segments 1 and 2 occurs between a regional WNW-ESE joint and the border fault, which is identified by a zig-zag pattern in SRTM data. Precambrian gneiss is cut by oblique steeply-dipping faults in this area. Striations and layer offsets suggest both right-lateral and normal components. This segment strikes NE-SW, in contrast with the NW-SE average strike of the entire fault. The foliations, faults, dikes, and joints collected in this area strike NE-SW, therefore running parallel to the segment. The last 3 southern linkage zones all strike NW-SE and the linkage zone between segment 3 and 4 has a steep dip angle. Dip angles of structures vary from segment to segment, having a wide range of results. Nonetheless, all four linkage zones show structures striking parallel to its segment direction. The results show that pre-existing meso-scale and regional structures and faults strike parallel to the fault scarp. The parallelism of the structures suggest that they serve as planes of weakness, controlling the localization of extension expressed as the border fault. Thus, further studies of the Precambrian foliation in the subsurface are necessary to understand the characterization of the fault where it is unexposed at depth.

Pinestraw raking, fertilization and poultry litter amendment effects on soil physical properties for a mid-rotation loblolly pine plantation

Treesearch

William B. Patterson; Michael A. Blazier; Steven L. Holtard

2010-01-01

Frequent pinestraw raking and removal in pine plantations has led to concerns about nutrient removal from the stand. While soil chemistry of raked stands has been studied, little attention has been placed on potential compaction from raking operations. Four treatments were applied to a 16-year-old loblolly pine plantation at the Louisiana State University AgCenter...

3D Numerical Modeling of the Propagation of Hydraulic Fracture at Its Intersection with Natural (Pre-existing) Fracture

NASA Astrophysics Data System (ADS)

Dehghan, Ali Naghi; Goshtasbi, Kamran; Ahangari, Kaveh; Jin, Yan; Bahmani, Aram

2017-02-01

A variety of 3D numerical models were developed based on hydraulic fracture experiments to simulate the propagation of hydraulic fracture at its intersection with natural (pre-existing) fracture. Since the interaction between hydraulic and pre-existing fractures is a key condition that causes complex fracture patterns, the extended finite element method was employed in ABAQUS software to simulate the problem. The propagation of hydraulic fracture in a fractured medium was modeled in two horizontal differential stresses (Δ σ) of 5e6 and 10e6 Pa considering different strike and dip angles of pre-existing fracture. The rate of energy release was calculated in the directions of hydraulic and pre-existing fractures (G_{{frac}} /G_{{rock}}) at their intersection point to determine the fracture behavior. Opening and crossing were two dominant fracture behaviors during the hydraulic and pre-existing fracture interaction at low and high differential stress conditions, respectively. The results of numerical studies were compared with those of experimental models, showing a good agreement between the two to validate the accuracy of the models. Besides the horizontal differential stress, strike and dip angles of the natural (pre-existing) fracture, the key finding of this research was the significant effect of the energy release rate on the propagation behavior of the hydraulic fracture. This effect was more prominent under the influence of strike and dip angles, as well as differential stress. The obtained results can be used to predict and interpret the generation of complex hydraulic fracture patterns in field conditions.

Design and flight testing of a nullable compressor face rake

NASA Technical Reports Server (NTRS)

Holzman, J. K.; Payne, G. A.

1973-01-01

A compressor face rake with an internal valve arrangement to permit nulling was designed, constructed, and tested in the laboratory and in flight at the NASA Flight Research Center. When actuated by the pilot in flight, the nullable rake allowed the transducer zero shifts to be determined and then subsequently removed during data reduction. Design details, the fabrication technique, the principle of operation, brief descriptions of associated digital zero-correction programs and the qualification tests, and test results are included. Sample flight data show that the zero shifts were large and unpredictable but could be measured in flight with the rake. The rake functioned reliably and as expected during 25 hours of operation under flight environmental conditions and temperatures from 230 K (-46 F) to greater than 430 K (314 F). The rake was nulled approximately 1000 times. The in-flight zero-shift measurement technique, as well as the rake design, was successful and should be useful in future applications, particularly where accurate measurements of both steady-state and dynamic pressures are required under adverse environmental conditions.

Simulated Three-Point Problems.

ERIC Educational Resources Information Center

Leyden, Michael B.

1979-01-01

The concept of sloping bedrock strata is portrayed by simple construction of a cardboard model. By use of wires and graph paper, students simulate the drilling of wells and use standard mathematical operations to determine strike and dip of the model stratum. (RE)

Geochemistry, mineralization, structure, and permeability of a normal-fault zone, Casino mine, Alligator Ridge district, north central Nevada

NASA Astrophysics Data System (ADS)

Hammond, K. Jill; Evans, James P.

2003-05-01

We examine the geochemical signature and structure of the Keno fault zone to test its impact on the flow of ore-mineralizing fluids, and use the mined exposures to evaluate structures and processes associated with normal fault development. The fault is a moderately dipping normal-fault zone in siltstone and silty limestone with 55-100 m of dip-slip displacement in north-central Nevada. Across-strike exposures up to 180 m long, 65 m of down-dip exposure and 350 m of along-strike exposure allow us to determine how faults, fractures, and fluids interact within mixed-lithology carbonate-dominated sedimentary rocks. The fault changes character along strike from a single clay-rich slip plane 10-20 mm thick at the northern exposure to numerous hydrocarbon-bearing, calcite-filled, nearly vertical slip planes in a zone 15 m wide at the southern exposure. The hanging wall and footwall are intensely fractured but fracture densities do not vary markedly with distance from the fault. Fault slip varies from pure dip-slip to nearly pure strike-slip, which suggests that either slip orientations may vary on faults in single slip events, or stress variations over the history of the fault caused slip vector variations. Whole-rock major, minor, and trace element analyses indicate that Au, Sb, and As are in general associated with the fault zone, suggesting that Au- and silica-bearing fluids migrated along the fault to replace carbonate in the footwall and adjacent hanging wall rocks. Subsequent fault slip was associated with barite and calcite and hydrocarbon-bearing fluids deposited at the southern end of the fault. No correlation exists at the meter or tens of meter scale between mineralization patterns and fracture density. We suggest that the fault was a combined conduit-barrier system in which the fault provides a critical connection between the fluid sources and fractures that formed before and during faulting. During the waning stages of deposit formation, the fault behaved as a localized conduit to hydrocarbon-bearing calcite veins. The results of this study show that fault-zone character may change dramatically over short, deposit- or reservoir-scale distances. The presence of damage zones may not be well correlated at the fine scale with geochemically defined regions of the fault, even though a gross spatial correlation may exist.

Earthquake geology of Kashmir Basin and its implications for future large earthquakes

NASA Astrophysics Data System (ADS)

Shah, A. A.

2013-09-01

Two major traces of active thrust faults were identified in the Kashmir Basin (KB) using satellite images and by mapping active geomorphic features. The ~N130°E strike of the mapped thrust faults is consistent with the regional ~NE-SW convergence along the Indian-Eurasian collision zone. The ~NE dipping thrust faults have uplifted the young alluvial fan surfaces at the SW side of the KB. This created a major tectono-geomorphic boundary along the entire strike length of the KB that is characterised by (1) a low relief with sediment-filled sluggish streams to the SE and (2) an uplifted region, with actively flowing streams to the SW. The overall tectono-geomorphic expression suggests that recent activity along these faults has tilted the entire Kashmir valley towards NE. Further, the Mw 7.6 earthquake, which struck Northern Pakistan and Kashmir on 8 October 2005, also suggests a similar strike and NE dipping fault plane, which could indicate that the KB fault is continuous over a distance of ~210 km and connects on the west with the Balakot Bagh fault. However, the geomorphic and the structural evidences of such a structure are not very apparent on the north-west, which thus suggest that it is not a contiguous structure with the Balakot Bagh fault. Therefore, it is more likely that the KB fault is an independent thrust, a possible ramp on the Main Himalayan Thrust, which has uplifting the SW portion of the KB and drowning everything to the NE (e.g. Madden et al. 2011). Furthermore, it seems very likely that the KB fault could be a right stepping segment of the Balakot Bagh fault, similar to Riasi Thrust, as proposed by Thakur et al. (2010). The earthquake magnitude is measured by estimating the fault rupture parameters (e.g. Wells and Coppersmith in Bull Seismol Soc Am 84:974-1002, 1994). Therefore, the total strike length of the mapped KB fault is ~120 km and by assuming a dip of 29° (Avouac et al. in Earth Planet Sci Lett 249:514-528, 2006) and a down-dip limit of 20 km, a Mw of 7.6 is possible on this fault.

Fault and joint geometry at Raft River Geothermal Area, Idaho

NASA Astrophysics Data System (ADS)

Guth, L. R.; Bruhn, R. L.; Beck, S. L.

1981-07-01

Raft River geothermal reservoir is formed by fractures in sedimentary strata of the Miocene and Pliocene salt lake formation. The fracturing is most intense at the base of the salt lake formation, along a decollement that dips eastward at less than 50 on top of metamorphosed precambrian and lower paleozoic rocks. Core taken from less than 200 m above the decollement contains two sets of normal faults. The major set of faults dips between 500 and 700. These faults occur as conjugate pairs that are bisected by vertical extension fractures. The second set of faults dips 100 to 200 and may parallel part of the basal decollement or reflect the presence of listric normal faults in the upper plate. Surface joints form two suborthogonal sets that dip vertically. East-northeast-striking joints are most frequent on the limbs of the Jim Sage anticline, a large fold that is associated with the geothermal field.

The offshore Palos Verdes fault zone near San Pedro, Southern California

USGS Publications Warehouse

Fisher, M.A.; Normark, W.R.; Langenheim, V.E.; Calvert, A.J.; Sliter, R.

2004-01-01

High-resolution seismic-reflection data are combined with a variety of other geophysical and geological data to interpret the offshore structure and earthquake hazards of the San Pedro shelf, near Los Angeles, California. Prominent structures investigated include the Wilmington graben, the Palos Verdes fault zone, various faults below the west part of the San Pedro shelf and slope, and the deep-water San Pedro basin. The structure of the Palos Verdes fault zone changes markedly along strike southeastward across the San Pedro shelf and slope. Under the north part of the shelf, this fault zone includes several strands, with the main strand dipping west. Under the slope, the main fault strands exhibit normal separation and mostly dip east. To the southeast near Lasuen Knoll, the Palos Verdes fault zone locally is low angle, but elsewhere near this knoll, the fault dips steeply. Fresh seafloor scarps near Lasuen Knoll indicate recent fault movement. We explain the observed structural variation along the Palos Verdes fault zone as the result of changes in strike and fault geometry along a master right-lateral strike-slip fault at depth. Complicated movement along this deep fault zone is suggested by the possible wave-cut terraces on Lasuen Knoll, which indicate subaerial exposure during the last sea level lowstand and subsequent subsidence of the knoll. Modeling of aeromagnetic data indicates a large magnetic body under the west part of the San Pedro shelf and upper slope. We interpret this body to be thick basalt of probable Miocene age. This basalt mass appears to have affected the pattern of rock deformation, perhaps because the basalt was more competent during deformation than the sedimentary rocks that encased the basalt. West of the Palos Verdes fault zone, other northwest-striking faults deform the outer shelf and slope. Evidence for recent movement along these faults is equivocal, because we lack age dates on deformed or offset sediment.

Dual Rotating Rake Measurements of Higher-Order Duct Modes: Validation Using Experimental and Numerical Data

NASA Technical Reports Server (NTRS)

Dahl, Milo D.; Hixon, Duane R.; Sutliff, Daniel L.

2018-01-01

A rotating rake mode measurement system was designed to measure acoustic duct modes generated by a fan stage. After analysis of the measured data, the mode coefficient amplitudes and phases were quantified. Early studies using this system found that mode power levels computed from rotating rake measured data would agree with the far-field power levels. However, this agreement required that the sound from the noise sources within the duct propagated outward from the duct exit without reflection and previous studies suggested conditions could exist where significant reflections could occur. This paper shows that mounting a second rake to the rotating system, with an offset in both the axial and the azimuthal directions, measures the data necessary to determine the modes propagating in both directions within a duct. The rotating rake data analysis technique was extended to include the data measured by the second rake. The analysis resulted in a set of circumferential mode coefficients at each of the two rake microphone locations. Radial basis functions were then least-squares fit to this data to obtain the radial mode coefficients for the modes propagating in both directions within the duct while accounting for the presence of evanescent modes. The validation of the dual-rotating-rake measurements was conducted using data from a combination of experiments and numerical calculations to compute reflection coefficients and other mode coefficient ratios. Compared to results from analytical and numerical computations, the results from dual-rotating-rake measured data followed the expected trends when frequency, mode number, and duct termination geometry were changed.

The effects of raking on sugar pine mortality following prescribed fire in Sequoia and Kings Canyon National Parks, California, USA

USGS Publications Warehouse

Nesmith, Jonathan C. B.; O'Hara, Kevin L.; van Mantgem, Phillip J.; de Valpine, Perry

2010-01-01

Prescribed fire is an important tool for fuel reduction, the control of competing vegetation, and forest restoration. The accumulated fuels associated with historical fire exclusion can cause undesirably high tree mortality rates following prescribed fires and wildfires. This is especially true for sugar pine (Pinus lambertiana Douglas), which is already negatively affected by the introduced pathogen white pine blister rust (Cronartium ribicola J.C. Fisch. ex Rabenh). We tested the efficacy of raking away fuels around the base of sugar pine to reduce mortality following prescribed fire in Sequoia and Kings Canyon national parks, California, USA. This study was conducted in three prescribed fires and included 457 trees, half of which had the fuels around their bases raked away to mineral soil to 0.5 m away from the stem. Fire effects were assessed and tree mortality was recorded for three years after prescribed fires. Overall, raking had no detectable effect on mortality: raked trees averaged 30% mortality compared to 36% for unraked trees. There was a significant effect, however, between the interaction of raking and average pre-treatment forest floor fuel depth: the predicted probability of survival of a 50 cm dbh tree was 0.94 vs. 0.96 when average pre-treatment fuel depth was 0 cm for a raked and unraked tree, respectively. When average pre-treatment forest floor fuel depth was 30 cm, the predicted probability of survival for a raked 50 cm dbh tree was 0.60 compared to only 0.07 for an unraked tree. Raking did not affect mortality when fire intensity, measured as percent crown volume scorched, was very low (0% scorch) or very high (>80% scorch), but the raking treatment significantly increased the proportion of trees that survived by 9.6% for trees that burned under moderate fire intensity (1% to 80% scorch). Raking significantly reduced the likelihood of bole charring and bark beetle activity three years post fire. Fuel depth and anticipated fire intensity need to be accounted for to maximize the effectiveness of the treatments. Raking is an important management option to reduce tree mortality from prescribed fire, but is most effective under specific fuel and burning conditions.

Flow Visualization on a Small Scale.

DTIC Science & Technology

1988-03-01

1150 22.43 26 A good tunnel must have very uniform flow across the test section. The uniformity was checked using a seven tube pitot static rake ...calibration. il Figure 7. The Pitot Static Rake 27 To map the entire 15 x 24 inch cross section 84 individual readings and 12 rake locations were required... rake readings was taken, the micromanometer was reattached to the permanent pitot static probe to ensure calibration of the tunnel to .02 inches of

Further Development of Rotating Rake Mode Measurement Data Analysis

NASA Technical Reports Server (NTRS)

Dahl, Milo D.; Hixon, Ray; Sutliff, Daniel L.

2013-01-01

The Rotating Rake mode measurement system was designed to measure acoustic duct modes generated by a fan stage. After analysis of the measured data, the mode amplitudes and phases were quantified. For low-speed fans within axisymmetric ducts, mode power levels computed from rotating rake measured data would agree with the far-field power levels on a tone by tone basis. However, this agreement required that the sound from the noise sources within the duct propagated outward from the duct exit without reflection at the exit and previous studies suggested conditions could exist where significant reflections could occur. To directly measure the modes propagating in both directions within a duct, a second rake was mounted to the rotating system with an offset in both the axial and the azimuthal directions. The rotating rake data analysis technique was extended to include the data measured by the second rake. The analysis resulted in a set of circumferential mode levels at each of the two rake microphone locations. Radial basis functions were then least-squares fit to this data to obtain the radial mode amplitudes for the modes propagating in both directions within the duct. The fit equations were also modified to allow evanescent mode amplitudes to be computed. This extension of the rotating rake data analysis technique was tested using simulated data, numerical code produced data, and preliminary in-duct measured data.

Field Investigation of Surface Deformation Induced by the 2016 Meinong Earthquake and its Implications to Regional Geological Structures

NASA Astrophysics Data System (ADS)

Yi, De-Cheng; Chuang, Ray Y.; Lin, Ching-Weei

2017-04-01

We demonstrate mapping results of a newly-identified active folding-associated fault in southwestern Taiwan, which was triggered by the distant ML 6.6 Meinong earthquake in 2016. The 14.6-km-deep main shock occurred in Meinong at 3:57 (GMT +08) on February 6th while a series of 21-27 km deep aftershocks were induced after 160 seconds in Guanmiao, where is 25km NW away from the epicenter of the main shock. The focal mechanism of the Meinong main shock shows a westward oblique thrust with the fault plane of 275°/42°/17° (strike/dip/rake) but Guanmiao aftershocks show the N-S striking eastward normal movement. The study area locates at an on-going fold-and-thrust belt close to the deformation front of Taiwan orogeny with high rates of convergence, uplift and erosion. The geology of SW Taiwan is characterized by the 3-km-thick mudstones with high fluid pressure underlying the loose sedimentary rocks forming mud diapirs or mud-core anticlines. The significance of the Meinong earthquake is (1) aftershocks are far away from the main shock, and (2) the surface cracks partially distributed systematically along lineaments observed from InSAR, which has never been recognized as geological structures before. This study aims to establish possible kinematic processes of shallow deformation induced by the Meinong earthquake. We mapped surface cracks around the lineaments by using hand-held GPS and measured surface cracks by the compass and vernier. Among 249 kinematic data measured from 244 observed surface cracks and ruptures, the type of deformation was mostly identified as dilation or lateral translation and only 4 data were compressional deformation. The overall surface displacement moved to the northwest and west, consistent with the regional coseismic movement. The opening of the surface cracks range from 0.5 to 105 mm and 85% of them are less than 10 mm. Preseismic deformed features such as failure of the retaining wall were also observed along the western and eastern boundary of the coseismic deformation area, indicating accumulated deformation and repeated structural activity in this area. In addition, we found a series of centimeters to meters long, N-S to N-W striking and eastern-side-down surface ruptures with the 4-19 cm heave distributed along the 4-km-long, nearly N-S striking and range-facing scarp with the 4-12 m height at the west of Guanmiao, where locate between the Chungchou anticline and Guanmiao syncline. We interpret these surface ruptures as a sign of the bending-moment fault associated with folding amplified by seismic energy through fluid-rich mud diapirs. Thus, seismic potential in this region needs to be re-evaluated, and the mechanism of seismic-induced amplification through high fluid pressure medium may play a critical role in assessing earthquake hazards in regions with similar geology to SW Taiwan.

Analysis of Dual Rotating Rake Data from the NASA Glenn Advanced Noise Control Fan Duct with Artificial Sources

NASA Technical Reports Server (NTRS)

Dahl, Milo D.; Sutliff, Daniel L.

2014-01-01

The Rotating Rake mode measurement system was designed to measure acoustic duct modes generated by a fan stage. Initially, the mode amplitudes and phases were quantified from a single rake measurement at one axial location. To directly measure the modes propagating in both directions within a duct, a second rake was mounted to the rotating system with an offset in both the axial and the azimuthal directions. The rotating rake data analysis technique was then extended to include the data measured by the second rake. The analysis resulted in a set of circumferential mode levels at each of the two rake microphone locations. Radial basis functions were then least-squares fit to this data to obtain the radial mode amplitudes for the modes propagating in both directions within the duct. Validation experiments have been conducted using artificial acoustic sources. Results are shown for the measurement of the standing waves in the duct from sound generated by one and two acoustic sources that are separated into the component modes propagating in both directions within the duct. Measured reflection coefficients from the open end of the duct are compared to analytical predictions.

Source parameters of the 2014 Ms6.5 Ludian earthquake sequence and their implications on the seismogenic structure

NASA Astrophysics Data System (ADS)

Zheng, Y.

2015-12-01

On August 3, 2014, an Ms6.5 earthquake struck Ludian county, Zhaotong city in Yunnan province, China. Although this earthquake is not very big, it caused abnormal severe damages. Thus, study on the causes of the serious damages of this moderate strong earthquake may help us to evaluate seismic hazards for similar earthquakes. Besides the factors which directly relate to the damages, such as site effects, quality of buildings, seismogenic structures and the characteristics of the mainshock and the aftershocks may also responsible for the seismic hazards. Since focal mechanism solution and centroid depth provide key information of earthquake source properties and tectonic stress field, and the focal depth is one of the most important parameters which control the damages of earthquakes, obtaining precise FMSs and focal depths of the Ludian earthquake sequence may help us to determine the detailed geometric features of the rupture fault and the seismogenic environment. In this work we obtained the FMSs and centroid depths of the Ludian earthquake and its Ms>3.0 aftershocks by the revised CAP method, and further verified some focal depths using the depth phase method. Combining the FMSs of the mainshock and the strong aftershocks, as well as their spatial distributions, and the seismogenic environment of the source region, we can make the following characteristics of the Ludian earthquake sequence and its seismogenic structure: (1) The Ludian earthquake is a left-lateral strike slip earthquake, with magnitude of about Mw6.1. The FMS of nodal plane I is 75o/56o/180o for strike, dip and rake angles, and 165o/90o/34ofor the other nodal plane. (2) The Ludian earthquake is very shallow with the optimum centroid depth of ~3 km, which is consistent with the strong ground shaking and the surface rupture observed by field survey and strengthens the damages of the Ludian earthquake. (3) The Ludian Earthquake should occur on the NNW trend BXF. Because two later aftershocks occurred close to the fault zone of the ZLF, and their FMSs are similar with the characteristics of the ZLF, the shallower part of the ZLF may also rupture during the aftershock duration of the Ludian earthquake. Since the ZLF is much longer than the BXF, the seismic risk of the ZLF may be high and should be required more attention.

Application example: Preliminary Results of ISOLA use to find moment tensor solutions and centroid depth applied to aftershocks of Mw=8.8 February 27 2010, Maule Earthquake

NASA Astrophysics Data System (ADS)

Nacif, S. V.; Sanchez, M. A.

2013-05-01

We selected seven aftershocks from Maule earthquake between 33.5°S to 35°S from May to September to find single source inversion. The data were provided by XY Chile Ramp Experiment* which was deployed after great Maule earthquake. Waveform data are from 13 broad band stations chosen from the 58 broad band stations deployed by IRIS-PASCAL from April to September 2010. Stations are placed above the normal subduction section south of ~33.5°S. Events were located with an iterative software called Hypocenter using one dimensional local model, obtained above for the forearc region between 33°S to 35°S. We used ISOLA which is a fortran code with a Matlab interface to obtain moment tensors solutions, optimum position and time of the subevents. Values depth obtained by a grid search of centroid position show range values which are compatibles with the interplate seismogenic zone. Double-Couple focal mechanism solutions (Figure 1) show 4 thrust events which can be associated with that zone. However, only one of them has strike, dip and rake of 358°, 27° and 101 respectively, appropriate to be expected for interplate seismogenic zone. On the other hand, the other 3 events show strike and normal double-couple focal mechanism solutions (Figure 1). This last topic makes association to those events to the contact of the Nazca and South American plate difficult. Nevertheless, in a first stage, their depths may allow possibility of an origin there. * The facilities of the IRIS Data Management System, and specifically the IRIS Data Management Center, were used for access to waveform, metadata or products required in this study. The IRIS DMS is funded through the National Science Foundation and specifically the GEO Directorate through the Instrumentation and Facilities Program of the National Science Foundation under Cooperative Agreement EAR-0552316. Some activities of are supported by the National Science Foundation EarthScope Program under Cooperative Agreement EAR-0733069. Figure 1. Doble-Couple focal mechanisms solutions from Moment Tensor Inversion using ISOLA. Triangles show broad band stations used in this work from IRIS-PASSCAL.

Ground Impingement of a Fan Jet Exhaust Plume

DTIC Science & Technology

1978-05-01

ground plane to avoid a possible interaction between the ground-deflected exhaust and the fan j .t engine inlet. Two pitot pressure rakes , shown on the...Pressure signals from the two rakes (total of 18 pitot tubes) were read sequentially with a Scannivalve system, time-averaged, and displayed on a pen...taken from the inner anid outer rakes with the ground plane normal to the flow at h/d f 2. Pitot pressures from each rake were normalized by the

Multipurpose Rotating Rake Arrays for Integrated Inlet and Fan Stage Performance Measurement

NASA Technical Reports Server (NTRS)

Wolter, John D.

2017-01-01

Low-pressure-ratio fan stage performance measurement requires precise measurement of conditions upstream and downstream of the fan stage. This presentation will discuss the rotating rake arrays used for the recent Boundary Layer Ingesting Inlet-Distortion-Tolerant Fan experiment in the NASA Glenn 8 by 6 foot wind tunnel. To achieve precise measurements, simulations of the rake sampling from pre-test CFD (Computerized Fluid Dynamics) solutions were used to optimize the number and locations of rake instruments.

Fault geometries in basement-induced wrench faulting under different initial stress states

NASA Astrophysics Data System (ADS)

Naylor, M. A.; Mandl, G.; Supesteijn, C. H. K.

Scaled sandbox experiments were used to generate models for relative ages, dip, strike and three-dimensional shape of faults in basement-controlled wrench faulting. The basic fault sequence runs from early en échelon Riedel shears and splay faults through 'lower-angle' shears to P shears. The Riedel shears are concave upwards and define a tulip structure in cross-section. In three dimensions, each Riedel shear has a helicoidal form. The sequence of faults and three-dimensional geometry are rationalized in terms of the prevailing stress field and Coulomb-Mohr theory of shear failure. The stress state in the sedimentary overburden before wrenching begins has a substantial influence on the fault geometries and on the final complexity of the fault zone. With the maximum compressive stress (∂ 1) initially parallel to the basement fault (transtension), Riedel shears are only slightly en échelon, sub-parallel to the basement fault, steeply dipping with a reduced helicoidal aspect. Conversely, with ∂ 1 initially perpendicular to the basement fault (transpression), Riedel shears are strongly oblique to the basement fault strike, have lower dips and an exaggerated helicoidal form; the final fault zone is both wide and complex. We find good agreement between the models and both mechanical theory and natural examples of wrench faulting.

Investigation of the M6.6 Niigata-Chuetsu Oki, Japan, earthquake of July 16, 2007

USGS Publications Warehouse

Kayen, Robert; Collins, Brian D.; Abrahamson, Norm; Ashford, Scott; Brandenberg, Scott J.; Cluff, Lloyd; Dickenson, Stephen; Johnson, Laurie; Tanaka, Yasuo; Tokimatsu, Kohji; Kabeyasawa, Toshimi; Kawamata, Yohsuke; Koumoto, Hidetaka; Marubashi, Nanako; Pujol, Santiago; Steele, Clint; Sun, Joseph I.; Tsai, Ben; Yanev, Peter; Yashinsky, Mark; Yousok, Kim

2007-01-01

The M6.6 mainshock of the Niigata Chuetsu Oki (offshore) earthquake occurred at 10:13 a.m. local time on July 16, 2007, and was followed by a sequence of aftershocks that were felt during the entire time of the reconnaissance effort. The mainshock had an estimated focal depth of 10 km and struck in the Japan Sea offshore Kariwa. Analysis of waveforms from source inversion studies indicates that the event occurred along a thrust fault with a NE trend. The fault plane is either a strike of 34 degrees with a dip of 51 degrees or a strike of 238 degrees with a dip of 41 degrees. Which of these two planes is associated with the mainshock rupture is unresolved, although attenuation relationship analysis indicates that the northwest-dipping fault is favored. The quake affected an approximately 100-km-wide area along the coastal areas of southwestern Niigata prefecture. The event triggered ground failures as far as the Unouma Hills, located in central Niigata approximately 50 km from the shore and the source area of the 2004 Niigata Chuetsu earthquake. The primary event produced tsunami run-ups that reached maximum runup heights of about 20 centimeters along the shoreline of southern Niigata Prrefecture.

Rotating Rake Turbofan Duct Mode Measurement System

NASA Technical Reports Server (NTRS)

Sutliff, Daniel L.

2005-01-01

An experimental measurement system was developed and implemented by the NASA Glenn Research Center in the 1990s to measure turbofan duct acoustic modes. The system is a continuously rotating radial microphone rake that is inserted into the duct. This Rotating Rake provides a complete map of the acoustic duct modes present in a ducted fan and has been used on a variety of test articles: from a low-speed, concept test rig, to a full-scale production turbofan engine. The Rotating Rake has been critical in developing and evaluating a number of noise reduction concepts as well as providing experimental databases for verification of several aero-acoustic codes. More detailed derivation of the unique Rotating Rake equations are presented in the appendix.

Design and development of an F/A-18 inlet distortion rake: A cost and time saving solution

NASA Technical Reports Server (NTRS)

Yuhas, Andrew J.; Ray, Ronald J.; Burley, Richard R.; Steenken, William G.; Lechtenberg, Leon; Thornton, Don

1995-01-01

An innovative inlet total pressure distortion measurement rake has been designed and developed for the F/A-18 A/B/C/D aircraft inlet. The design was conceived by NASA and General Electric Aircraft Engines personnel. This rake has been flight qualified and flown in the F/A-18 High Alpha Research Vehicle at NASA Dryden Flight Research Center, Edwards, California. The eight-legged, one-piece, wagon wheel design of the rake was developed at a reduced cost and offered reduced installation time compared to traditional designs. The rake features 40 dual-measurement ports for low- and high-frequency pressure measurements with the high-frequency transducer mounted at the port. This high-frequency transducer offers direct absolute pressure measurements from low to high frequencies of interest, thereby allowing the rake to be used during highly dynamic aircraft maneuvers. Outstanding structural characteristics are inherent to the design through its construction and use of lightweight materials.

A link between deformation history and the orientation of reflective structures in the 2.68-2.83 Ga Opatica belt of the Canadian Superior Province

NASA Astrophysics Data System (ADS)

Bellefleur, G.; Calvert, A. J.; Chouteau, M. C.

1997-07-01

True three-dimensional reflector orientations can be derived from prestack seismic reflection data where a seismic profile is particularly crooked. This is accomplished by estimating a measure of coherency along travel time trajectories defined by the azimuth, dip, and depth of a reflector and the medium velocity. Results from Lithoprobe line 48, located in the Opatica belt of the Archean Superior Province, differentiate reflectors with two distinct orientations, which coincide with the attitudes of two deformational fabrics mapped at surface. Assuming a connection between reflectivity and strain induced by tectonic processes, the reflectors with NNE strikes and shallow dips toward the east are correlated with surface evidence for early west vergent thrusting in the Opatica belt. Other reflectors, which strike ENE-WSW and dip shallowly to the north and to the south, indicate that most of the reflectors in the southern Opatica and beneath the Abitibi greenstone belt at middle and lower crustal levels formed during a later, approximately N-S shortening event. Mantle reflections previously interpreted as a relict suture of an Archean subduction zone dip to the north at around 30°-45° and are also associated with this N-S event. The distribution of reflector orientations estimated at the crooked parts of line 48 indicates that much of the Opatica crust was reworked during the N-S shortening event, although a region of the middle and lower crust, characterized by the earlier D1 reflectors, is preserved in the central part of the belt.

On the use of imaginary faults in palaeostress analysis

NASA Astrophysics Data System (ADS)

Shan, Yehua; Liang, Xinquan

2017-11-01

The imaginary fault refers to the counterpart of a certain given fault that has a similar expression about the Wallace-Bott hypothesis. It is included to further reduce the feasible fields for the principal stress directions using the right dihedra method. The given fault and its imaginary fault have a similar dip-slip sense under the extensional or compressional regime but, as proved in this paper, a different dip-slip sense under the strike-slip regime. Their relation in dip-slip sense does no change with the rotation of the coordinate system, thus making possible the general use in the reduction of the imaginary faults under any tectonic regime. A procedure for this use is proposed and applied to a real example to demonstrate the feasibility of this method.

Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

NASA Astrophysics Data System (ADS)

Ruch, J.; Vezzoli, L.; De Rosa, R.; Di Lorenzo, R.; Acocella, V.

2016-02-01

The regional stress field in volcanic areas may be overprinted by that produced by magmatic activity, promoting volcanism and faulting. In particular, in strike-slip settings, the definition of the relationships between the regional stress field and magmatic activity remains elusive. To better understand these relationships, we collected stratigraphic, volcanic, and structural field data along the strike-slip central Aeolian arc (Italy): here the islands of Lipari and Vulcano separate the extensional portion of the arc (to the east) from the contractional one (to the west). We collected >500 measurements of faults, extension fractures, and dikes at 40 sites. Most structures are NNE-SSW to NNW-SSE oriented, eastward dipping, and show almost pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral shear. Our data highlight six eruptive periods during the last 55 ka, which allow considering both islands as a single magmatic system, in which tectonic and magmatic activities steadily migrated eastward and currently focus on a 10 km long × 2 km wide active segment. Faulting appears to mostly occur in temporal and spatial relation with magmatic events, supporting that most of the observable deformation derives from transient magmatic activity (shorter term, days to months), rather than from steady longer-term regional tectonics (102-104 years). More in general, the central Aeolian case shows how magmatic activity may affect the structure and evolution of volcanic arcs, overprinting any strike-slip motion with magma-induced extension at the surface.

Thrust Vectoring for Advanced Fighter Aircraft - High Angle of Attack Intake Investigations -

DTIC Science & Technology

2001-06-01

these losses. plane) a rake for the measurement of swirl and pressure recovery has been used. The five-hole probes and the pitot Whereas the total...true for the two be recognized in fig. 4,3.1. There exist 8 rake arms with 7 pitot intake parameters mean swirl and dynamic distortion. In order probes...recognized that at the low intake mass this rake is measured with the help of 16 rake arms with 5 pitot flowT the pressure recovery up to an angle of

Marine geology and earthquake hazards of the San Pedro Shelf region, southern California

USGS Publications Warehouse

Fisher, Michael A.; Normark, William R.; Langenheim, V.E.; Calvert, Andrew J.; Sliter, Ray

2004-01-01

High-resolution seismic-reflection data have been com- bined with a variety of other geophysical and geological data to interpret the offshore structure and earthquake hazards of the San Pedro Shelf, near Los Angeles, California. Prominent structures investigated include the Wilmington Graben, the Palos Verdes Fault Zone, various faults below the western part of the shelf and slope, and the deep-water San Pedro Basin. The structure of the Palos Verdes Fault Zone changes mark- edly southeastward across the San Pedro Shelf and slope. Under the northern part of the shelf, this fault zone includes several strands, but the main strand dips west and is probably an oblique-slip fault. Under the slope, this fault zone con- sists of several fault strands having normal separation, most of which dip moderately east. To the southeast near Lasuen Knoll, the Palos Verdes Fault Zone locally is a low-angle fault that dips east, but elsewhere near this knoll the fault appears to dip steeply. Fresh sea-floor scarps near Lasuen Knoll indi- cate recent fault movement. The observed regional structural variation along the Palos Verdes Fault Zone is explained as the result of changes in strike and fault geometry along a master strike-slip fault at depth. The shallow summit and possible wavecut terraces on Lasuen knoll indicate subaerial exposure during the last sea-level lowstand. Modeling of aeromagnetic data indicates the presence of a large magnetic body under the western part of the San Pedro Shelf and upper slope. This is interpreted to be a thick body of basalt of Miocene(?) age. Reflective sedimentary rocks overlying the basalt are tightly folded, whereas folds in sedimentary rocks east of the basalt have longer wavelengths. This difference might mean that the basalt was more competent during folding than the encasing sedimentary rocks. West of the Palos Verdes Fault Zone, other northwest-striking faults deform the outer shelf and slope. Evidence for recent movement along these faults is equivocal, because age dates on deformed or offset sediment are lacking.

Analysis of the tsunami generated by the MW 7.8 1906 San Francisco earthquake

USGS Publications Warehouse

Geist, E.L.; Zoback, M.L.

1999-01-01

We examine possible sources of a small tsunami produced by the 1906 San Francisco earthquake, recorded at a single tide gauge station situated at the opening to San Francisco Bay. Coseismic vertical displacement fields were calculated using elastic dislocation theory for geodetically constrained horizontal slip along a variety of offshore fault geometries. Propagation of the ensuing tsunami was calculated using a shallow-water hydrodynamic model that takes into account the effects of bottom friction. The observed amplitude and negative pulse of the first arrival are shown to be inconsistent with small vertical displacements (~4-6 cm) arising from pure horizontal slip along a continuous right bend in the San Andreas fault offshore. The primary source region of the tsunami was most likely a recently recognized 3 km right step in the San Andreas fault that is also the probable epicentral region for the 1906 earthquake. Tsunami models that include the 3 km right step with pure horizontal slip match the arrival time of the tsunami, but underestimate the amplitude of the negative first-arrival pulse. Both the amplitude and time of the first arrival are adequately matched by using a rupture geometry similar to that defined for the 1995 MW (moment magnitude) 6.9 Kobe earthquake: i.e., fault segments dipping toward each other within the stepover region (83??dip, intersecting at 10 km depth) and a small component of slip in the dip direction (rake=-172??). Analysis of the tsunami provides confirming evidence that the 1906 San Francisco earthquake initiated at a right step in a right-lateral fault and propagated bilaterally, suggesting a rupture initiation mechanism similar to that for the 1995 Kobe earthquake.

Detailed Surface Rupture Geometry from the 2016 Amatrice Earthquake

NASA Astrophysics Data System (ADS)

Mildon, Z. K.; Iezzi, F.; Wedmore, L. N. J.; Gregory, L. C.; McCaffrey, K. J. W.; Wilkinson, M. W.; Faure Walker, J.; Roberts, G.; Livio, F.; Vittori, E.; Michetti, A.; Frigerio, C.; Ferrario, F.; Blumetti, A. M.; Guerrieri, L.; Di Manna, P.; Comerci, V.

2016-12-01

The Amatrice earthquake was generated by co-rupture of the Mt. Vettore and Laga faults at depth. Surface ruptures were observed for 5km along the Mt. Vettore fault, with no clear observations on the Laga fault reported to date. The surface rupture on Mt. Vettore manifests as a 15-20cm pale stripe at the base of a 60-80o dipping bedrock fault scarp and similar magnitude vertical offsets of colluvial deposits. We have measured the strike and dip of the fault alongside the coseismic throw, heave, and slip azimuth along the length of the rupture with high spatial resolution (c.2-6m, >2000 measurements). The slip azimuth is relatively constant between 210-270° even where the rupture faces uphill at its SE termination which is consistent with the regional NW-SE extension direction, defined by focal mechanisms and borehole break-out data. The simplest coseismic throw profile that would be expected is quasi-symmetric. However we found the highest values of throw (Inter Quartile Range 15-19.5cm) are skewed towards the NW end on a 1.7 km section of the fault that is oblique relative to the overall fault strike. In the centre of the rupture, orientated close to the overall fault strike, the throw is lower (IQR 7.5-13cm) and discontinuous along strike. We suggest that the skewed throw profile occurs because the strike, dip and throw must vary systematically in order to preserve the principal strain rate across a fault, in agreement with previous publications. The density of our measurements, crucially including the slip azimuth, allows us to resolve the regional debate over whether normal fault ruptures are primary tectonic features or landslides of hangingwall sediments. If the surface offsets are due to landslides, then the slip azimuth should correlate with the downslope direction of the hangingwall. We show using an available 10m DEM that this is not the case and hence the surface offsets described herein are a primary tectonic feature. This presentation offers new insights into rupture processes because of the high resolution of the dataset collected rapidly after the earthquake, but crucially because it includes the slip vector azimuth, allowing a full description of the kinematics of the faulting relative to the regional stress field and local topographic variations.

Seismic investigation of the Kunlun Fault: Analysis of the INDEPTH IV 2-D active-source seismic dataset

NASA Astrophysics Data System (ADS)

Seelig, William George

The Tibetan Plateau has experienced significant crustal thickening and deformation since the continental subduction and collision of the Asian and Indian plates in the Eocene. Deformation of the northern Tibetan Plateau is largely accommodated by strike-slip faulting. The Kunlun Fault is a 1000-km long strike-slip fault near the northern boundary of the Plateau that has experienced five magnitude 7.0 or greater earthquakes in the past 100 years and represents a major rheological boundary. Active-source, 2-D seismic reflection/refraction data, collected as part of project INDEPTH IV (International Deep Profiling of Tibet and the Himalaya, phase IV) in 2007, was used to examine the structure and the dip of the Kunlun fault. The INDEPTH IV data was acquired to better understand the tectonic evolution of the northeastern Tibetan Plateau, such as the far-field deformation associated with the continent-continent collision and the potential subduction of the Asian continent beneath northern Tibet. Seismic reflection common depth point (CDP) stacks were examined to look for reflectivity patterns that may be associated with faulting. A possible reflection from the buried North Kunlun Thrust (NKT) is identified at 18-21 km underneath the East Kunlun Mountains, with an estimated apparent dip of 15°S and thrusting to the north. Minimally-processed shot gathers were also inspected for reflections off near-vertical structures such as faults and information on first-order velocity structure. Shot offset and nearest receiver number to reflection was catalogued to increase confidence of picks. Reflections off the North Kunlun (NKF) and South Kunlun Faults (SKF) were identified and analyzed for apparent dip and subsurface geometry. Fault reflection analysis found that the North Kunlun Fault had an apparent dip of approximately 68ºS to an estimated depth of 5 km, while the South Kunlun Fault dipped at approximately 78ºN to an estimated 3.5 km depth. Constraints on apparent dip and geometry of the NKF/SKF and NKT provide information valuable for seismic hazard analysis.

Geometry and active tectonics of the Los Osos-Hosgri Fault Intersection in Estero Bay, CA: Reconciling seismicity patterns with near-surface geology

NASA Astrophysics Data System (ADS)

Watt, J. T.; Hardebeck, J.; Johnson, S. Y.; Kluesner, J.

2016-12-01

Characterizing active structures within structurally complex fault intersections is essential for unraveling the deformational history and for assessing the importance of fault intersections in regional earthquake hazard assessments. We employ an integrative, multi-scale geophysical approach to describe the 3D geometry and active tectonics of the offshore Los Osos fault (LOF) in Estero Bay, California. The shallow structure of the LOF, as imaged with multibeam and high-resolution seismic-reflection data, reveals a complex west-diverging zone of active faulting that bends into and joins the Hosgri fault. The down-dip geometry of the LOF as revealed by gravity, magnetic, and industry multi-channel seismic data, is vertical to steeply-dipping and varies along strike. As the LOF extends offshore, it is characterized by SW-side-up motion on a series of W-NW trending, steeply SW-dipping reverse faults. The LOF bends to the north ( 23°) as it approaches the Hosgri fault and dips steeply to the NE along a magnetic basement block. Inversion of earthquake focal mechanisms within Estero Bay yields maximum compressive stress axes that are near-horizontal and trend approximately N15E. This trend is consistent with dextral strike-slip faulting along NW-SE trending structures such as the Hosgri fault and northern LOF, and oblique dip-slip motion along the W-NW trending section of the LOF. Notably, NW-SE trending structures illuminated by seismicity in Estero Bay coincide with, but also appear to cross-cut, LOF structures imaged in the near-surface. We suggest this apparent disconnect reflects ongoing fault reorganization at a dynamic and inherently unstable fault intersection, in which the seismicity reflects active deformation at depth that is not clearly expressed in the near-surface geology. Direct connectivity between the Hosgri and Los Osos faults suggests a combined earthquake rupture is possible; however, the geometrical complexity along the offshore LOF may limit the extent of rupture.

The July 12, 1993, Hokkaido-Nansei-Oki, Japan, earthquake: Coseismic slip pattern from strong-motion and teleseismic recordings

USGS Publications Warehouse

Mendoza, C.; Fukuyama, E.

1996-01-01

We employ a finite fault inversion scheme to infer the distribution of coseismic slip for the July 12, 1993, Hokkaido-Nansei-Oki earthquake using strong ground motions recorded by the Japan Meteorological Agency within 400 km of the epicenter and vertical P waveforms recorded by the Global Digital Seismograph Network at teleseismic distances. The assumed fault geometry is based on the location of the aftershock zone and comprises two fault segments with different orientations: a northern segment striking at N20??E with a 30?? dip to the west and a southern segment with a N20??W strike. For the southern segment we use both westerly and easterly dip directions to test thrust orientations previously proposed for this portion of the fault. The variance reduction is greater using a shallow west dipping segment, suggesting that the direction of dip did not change as the rupture propagated south from the hypocenter. This indicates that the earthquake resulted from the shallow underthrusting of Hokkaido beneath the Sea of Japan. Static vertical movements predicted by the corresponding distribution of fault slip are consistent with the general pattern of surface deformation observed following the earthquake. Fault rupture in the northern segment accounts for about 60% of the total P wave seismic moment of 3.4 ?? 1020 N m and includes a large circular slip zone (4-m peak) near the earthquake hypocenter at depths between 10 and 25 km. Slip in the southern segment is also predominantly shallower than 25 km, but the maximum coseismic displacements (2.0-2.5 m) are observed at a depth of about 5 km. This significant shallow slip in the southern portion of the rupture zone may have been responsible for the large tsunami that devastated the small offshore island of Okushiri. Localized shallow faulting near the island, however, may require a steep westerly dip to reconcile the measured values of ground subsidence.

Source Process of the 2007 Niigata-ken Chuetsu-oki Earthquake Derived from Near-fault Strong Motion Data

NASA Astrophysics Data System (ADS)

Aoi, S.; Sekiguchi, H.; Morikawa, N.; Ozawa, T.; Kunugi, T.; Shirasaka, M.

2007-12-01

The 2007 Niigata-ken Chuetsu-oki earthquake occurred on July 16th, 2007, 10:13 JST. We performed a multi- time window linear waveform inversion analysis (Hartzell and Heaton, 1983) to estimate the rupture process from the near fault strong motion data of 14 stations from K-NET, KiK-net, F-net, JMA, and Niigata prefecture. The fault plane for the mainshock has not been clearly determined yet from the aftershock distribution, so that we performed two waveform inversions for north-west dipping fault (Model A) and south-east dipping fault (Model B). Their strike, dip, and rake are set to those of the moment tensor solutions by F-net. Fault plane model of 30 km length by 24 km width is set to cover aftershock distribution within 24 hours after the mainshock. Theoretical Green's functions were calculated by the discrete wavenumber method (Bouchon, 1981) and the R/T matrix method (Kennett, 1983) with the different stratified medium for each station based on the velocity structure including the information form the reflection survey and borehole logging data. Convolution of moving dislocation was introduced to represent the rupture propagation in an each subfault (Sekiguchi et al., 2002). The observed acceleration records were integrated into velocity except of F-net velocity data, and bandpass filtered between 0.1 and 1.0 Hz. We solved least-squared equation to obtain slip amount of each time window on each subfault to minimize squared residual of the waveform fitting between observed and synthetic waveforms. Both models provide moment magnitudes of 6.7. Regarding Model A, we obtained large slip in the south-west deeper part of the rupture starting point, which is close to Kashiwazaki-city. The second or third velocity pulses of observed velocity waveforms seem to be composed of slip from the asperity. Regarding Model B, we obtained large slip in the southwest shallower part of the rupture starting point, which is also close to Kashiwazaki-city. In both models, we found small slip near the rupture starting point, and largest slip at about ten kilometer in the south-west of the rupture starting point with the maximum slip of 2.3 and 2.5 m for Models A and B, respectively. The difference of the residual between observed and synthetic waveforms for both models is not significant, therefore it is difficult to conclude which fault plane is appropriate to explain. The estimated large-slip regions in the inverted source models with the Models A and B are located near the cross point of the two fault plane models, which should have similar radiation pattern. This situation may be one of the reasons why judgment of the fault plane orientation is such difficult. We need careful examinations not only strong motion data but also geodetic data to further explore the fault orientation and the source process of this earthquake.

High resolution t-LiDAR scanning of an active bedrock fault scarp for palaeostress analysis

NASA Astrophysics Data System (ADS)

Reicherter, Klaus; Wiatr, Thomas; Papanikolaou, Ioannis; Fernández-Steeger, Tomas

2013-04-01

Palaeostress analysis of an active bedrock normal fault scarp based on kinematic indicators is carried applying terrestrial laser scanning (t-LiDAR or TLS). For this purpose three key elements are necessary for a defined region on the fault plane: (i) the orientation of the fault plane, (ii) the orientation of the slickenside lineation or other kinematic indicators and (iii) the sense of motion of the hanging wall. We present a workflow to obtain palaeostress data from point cloud data using terrestrial laser scanning. The entire case-study was performed on a continuous limestone bedrock normal fault scarp on the island of Crete, Greece, at four different locations along the WNW-ESE striking Spili fault. At each location we collected data with a mobile terrestrial light detection and ranging system and validated the calculated three-dimensional palaeostress results by comparison with the conventional palaeostress method with compass at three of the locations. Numerous kinematics indicators for normal faulting were discovered on the fault plane surface using t-LiDAR data and traditional methods, like Riedel shears, extensional break-outs, polished corrugations and many more. However, the kinematic indicators are more or less unidirectional and almost pure dip-slip. No oblique reactivations have been observed. But, towards the tips of the fault, inclination of the striation tends to point towards the centre of the fault. When comparing all reconstructed palaeostress data obtained from t-LiDAR to that obtained through manual compass measurements, the degree of fault plane orientation divergence is around ±005/03 for dip direction and dip. The degree of slickenside lineation variation is around ±003/03 for dip direction and dip. Therefore, the percentage threshold error of the individual vector angle at the different investigation site is lower than 3 % for the dip direction and dip for planes, and lower than 6 % for strike. The maximum mean variation of the complete calculated palaeostress tensors is ±005/03. So, technically t-LiDAR measurements are in the error range of conventional compass measurements. The advantages is that remote palaeostress analysis is possible. Further steps in our research will be studying reactivated faults planes with multiple kinematic indicators or striations with t-LiDAR.

Rupture process and strong ground motions of the 2007 Niigataken Chuetsu-Oki earthquake -Directivity pulses striking the Kashiwazaki-Kariwa Nuclear Power Plant-

NASA Astrophysics Data System (ADS)

Irikura, K.; Kagawa, T.; Miyakoshi, K.; Kurahashi, S.

2007-12-01

The Niigataken Chuetsu-Oki earthquake occurred on July 16, 2007, northwest-off Kashiwazaki in Niigata Prefecture, Japan, causing severe damages of ten people dead, about 1300 injured, about 1000 collapsed houses and major lifelines suspended. In particular, strong ground motions from the earthquake struck the Kashiwazaki-Kariwa nuclear power plant (hereafter KKNPP), triggering a fire at an electric transformer and other problems such as leakage of water containing radioactive materials into air and the sea, although the radioactivity levels of the releases are as low as those of the radiation which normal citizens would receive from the natural environment in a year. The source mechanism of this earthquake is a reverse fault, but whether it is the NE-SW strike and NW dip or the SW-NE strike and SE dip are still controversial from the aftershock distribution and geological surveys near the source. Results of the rupture processes inverted by using the GPS and SAR data, tsunami data and teleseismic data so far did not succeed in determining which fault planes moved. Strong ground motions were recorded at about 390 stations by the K-NET of NIED including the stations very close to the source area. There was the KKNPP which is probably one of buildings and facilities closest to the source area. They have their own strong motion network with 22 three-components' accelerographs locating at ground-surface, underground, buildings and basements of reactors. The PGA attenuation-distance relationships made setting the fault plane estimated from the GPS data generally follow the empirical relations in Japan, for example, Fukushima and Tanaka (1990) and Si and Midorikawa (1999), even if either fault plane, SE dip or NW dip, is assumed. However, the strong ground motions in the site of the KKNPP had very large accelerations and velocities more than those expected from the empirical relations. The surface motions there had the PGA of more than 1200 gals and even underground motions at the basements of the reactors locating five stories below the ground had the PGA of 680 gals. We simulated ground motions using the characterized source model (Kamae and Irikura, 1998) with three asperities and the empirical Green's function method (Irikura, 1986). Then, we found that the source model should be a reverse fault with the NE-SW strike and NW dip to explain the strong motion records obtained near the source area. In particular, strong ground motions in the site of the KKNPP had three significant pulses which are generated as directivity pulses in forward direction of rupture propagation. This is the reason why the strong ground motions in the site of the KKNPP had very large accelerations and velocities. The source model is also verified comparing the observed records at the KKNPP with the numerical simulations by the discrete wavenumber method (Bouchon, 1981).

Longleaf pine site response to repeated fertilization and forest floor removal by raking and prescribed burning

Treesearch

Kim Ludovici; Robert Eaton; Stanley Zarnoch

2018-01-01

Removal of forest floor litter by pine needle raking and prescribed burning is a common practice in longleaf pine (Pinus palustris Mill.) stands on Coastal Plain sites in the Southeastern United States. Repeated removal of litter by raking and the loss of surface organic matter from controlled burns can affect the...

Skin-Friction Measurements at Subsonic and Transonic Mach Numbers with Embedded-Wire Gages

DTIC Science & Technology

1981-01-01

Model ................................... 17 9. Boundary-Layer Rake Installation on EBOR Model...boundary-layer total pressure rake eliminates this bulky mechanism and the long data acquisition time, but it introduces interferences which affect the...its construction. Further, boundary-layer rakes are restricted to measurements in thick boundary layers. Surface pressure probes such as Stanton tubes

Marine forearc extension in the Hikurangi Margin: New insights from high-resolution 3D seismic data

NASA Astrophysics Data System (ADS)

Böttner, Christoph; Gross, Felix; Geersen, Jacob; Mountjoy, Joshu; Crutchley, Gareth; Krastel, Sebastian

2017-04-01

In subduction zones upper-plate normal faults have long been considered a tectonic feature primarily associated with erosive margins. However, increasing data coverage has proven that similar features also occur in accretionary margins, such as Cascadia, Makran, Nankai or Central Chile, where kinematics are dominated by compression. Considering their wide distribution there is, without doubt, a significant lack of qualitative and quantitative knowledge regarding the role and importance of normal faults and zones of extension for the seismotectonic evolution of accretionary margins. We use a high-resolution 3D P-Cable seismic volume from the Hikurangi Margin acquired in 2014 to analyze the spatial distribution and mechanisms of upper-plate normal faulting. The study area is located at the upper continental slope in the area of the Tuaheni landslide complex. In detail we aim to (1) map the spatial distribution of normal faults and characterize their vertical throws, strike directions, and dip angles; (2) investigate their possible influence on fluid migration in an area, where gas hydrates are present; (3) discuss the mechanisms that may cause extension of the upper-slope in the study area. Beneath the Tuaheni Landslide Complex we mapped about 200 normal faults. All faults have low displacements (<15 m) and dip at high (> 65°) angles. About 71% of the faults dip landward. We found two main strike directions, with the majority of faults striking 350-10°, parallel to the deformation front. A second group of faults strikes 40-60°. The faults crosscut the BSR, which indicates the base of the gas hydrate zone. In combination with seismically imaged bright-spots and pull-up structures, this indicates that the normal faults effectively transport fluids vertically across the base of the gas hydrate zone. Localized uplift, as indicated by the presence of the Tuaheni Ridge, might support normal faulting in the study area. In addition, different subduction rates across the margin may also favor extension between the segments. Future work will help to further untangle the mechanisms that cause extension of the upper continental slope.

Uncertainties for seismic moment tensors and applications to nuclear explosions, volcanic events, and earthquakes

NASA Astrophysics Data System (ADS)

Tape, C.; Alvizuri, C. R.; Silwal, V.; Tape, W.

2017-12-01

When considered as a point source, a seismic source can be characterized in terms of its origin time, hypocenter, moment tensor, and source time function. The seismologist's task is to estimate these parameters--and their uncertainties--from three-component ground motion recorded at irregularly spaced stations. We will focus on one portion of this problem: the estimation of the moment tensor and its uncertainties. With magnitude estimated separately, we are left with five parameters describing the normalized moment tensor. A lune of normalized eigenvalue triples can be used to visualize the two parameters (lune longitude and lune latitude) describing the source type, while the conventional strike, dip, and rake angles can be used to characterize the orientation. Slight modifications of these five parameters lead to a uniform parameterization of moment tensors--uniform in the sense that equal volumes in the coordinate domain of the parameterization correspond to equal volumes of moment tensors. For a moment tensor m that we have inferred from seismic data for an earthquake, we define P(V) to be the probability that the true moment tensor for the earthquake lies in the neighborhood of m that has fractional volume V. The average value of P(V) is then a measure of our confidence in our inference of m. The calculation of P(V) requires knowing both the probability P(w) and the fractional volume V(w) of the set of moment tensors within a given angular radius w of m. We apply this approach to several different data sets, including nuclear explosions from the Nevada Test Site, volcanic events from Uturuncu (Bolivia), and earthquakes. Several challenges remain: choosing an appropriate misfit function, handling time shifts between data and synthetic waveforms, and extending the uncertainty estimation to include more source parameters (e.g., hypocenter and source time function).

Effects of crustal layering on source parameter inversion from coseismic geodetic data

NASA Astrophysics Data System (ADS)

Amoruso, A.; Crescentini, L.; Fidani, C.

2004-10-01

We study the effect of a superficial layer overlying a half-space on the surface displacements caused by uniform slipping of a dip-slip normal rectangular fault. We compute static coseismic displacements using a 3-D analytical code for different characteristics of the layered medium, different fault geometries and different configurations of bench marks to simulate different kinds of geodetic data (GPS, Synthetic Aperture Radar, and levellings). We perform both joint and separate inversions of the three components of synthetic displacement without constraining fault parameters, apart from strike and rake, and using a non-linear global inversion technique under the assumption of homogeneous half-space. Differences between synthetic displacements computed in the presence of the superficial soft layer and in a homogeneous half-space do not show a simple regular behaviour, even if a few features can be identified. Consequently, also retrieved parameters of the homogeneous equivalent fault obtained by unconstrained inversion of surface displacements do not show a simple regular behaviour. We point out that the presence of a superficial layer may lead to misestimating several fault parameters both using joint and separate inversions of the three components of synthetic displacement and that the effects of the presence of the superficial layer can change whether all fault parameters are left free in the inversions or not. In the inversion of any kind of coseismic geodetic data, fault size and slip can be largely misestimated, but the product (fault length) × (fault width) × slip, which is proportional to the seismic moment for a given rigidity modulus, is often well determined (within a few per cent). Because inversion of coseismic geodetic data assuming a layered medium is impracticable, we suggest that only a case-to-case study involving some kind of recursive determination of fault parameters through data correction seems to give the proper approach when layering is important.

Tsunami waveform inversion of the 2007 Bengkulu, southern Sumatra earthquake

NASA Astrophysics Data System (ADS)

Fujii, Y.; Satake, K.

2007-12-01

We have performed tsunami waveform inversion for the 2007 Bengkulu, southern Sumatra earthquake on September 12, 2007 (4.520°S, 101.374°E, Mw=8.4 at 11:10:26 UTC according to USGS), and found that the large slips were located on deeper part (> 20 km) of the fault plane, more than 100 km from the trench axis. The deep slip might have contributed the relatively small tsunami for its earthquake size. The largest slips more than 6 m were located beneath Pagais Islands, about 100-200 km northwest of the epicenter. The obtained slip distribution yields a total seismic moment of 3.6 × 1021 Nm (Mw = 8.3). The tsunami generated by this earthquake was recorded at many tide gauge stations located in and around the Indian Ocean. The DART system installed in deep ocean and maintained by Thai Meteorological Department (TMD) also captured this tsunami. We have downloaded the tsunami waveforms at 16 stations from University of Hawaii Sea Level Center's (UHSLC) and National Oceanic & Atmospheric Administration's (NOAA) web sites. The observed tsunami records indicate that the tsunami amplitudes were less than several tens of cm at most stations, around 1 m at Padang, nearest station to the source, and a few cm at DART station. For the tsunami waveforms inversion, we divided the source area (length: 250 km, width: 200 km) into 20 subfaults. Tsunami waveforms from each subfault (50 km × 50 km) or Greens functions were calculated by numerically solving the linear shallow-water long-wave equations. We adopted the focal mechanism of Global CMT solution (strike: 327°, dip: 12°, rake: 114°) for each subfault, and assumed a rise time of 1 min. The computed tsunami waveforms from the estimated slip distribution explain the observed waveforms at most of tide gauges and DART station.

ADVANCED WAVEFORM SIMULATION FOR SEISMIC MONITORING EVENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helmberger, Donald V.; Tromp, Jeroen; Rodgers, Arthur J.

The recent Nevada Earthquake (M=6) produced an extraordinary set of crustal guided waves. In this study, we examine the three-component data at all the USArray stations in terms of how well existing models perform in predicting the various phases, Rayleigh waves, Love waves, and Pnl waves. To establish the source parameters, we applied the Cut and Paste Code up to distance of 5° for an average local crustal model which produced a normal mechanism (strike=35°,dip=41°,rake=-85°) at a depth of 9 km and Mw=5.9. Assuming this mechanism, we generated synthetics at all distances for a number of 1D and 3D models.more » The Pnl observations fit the synthetics for the simple models well both in timing (VPn=7.9km/s) and waveform fits out to a distance of about 5°. Beyond this distance a great deal of complexity can be seen to the northwest apparently caused by shallow subducted slab material. These paths require considerable crustal thinning and higher P-velocities. Small delays and advances outline the various tectonic province to the south, Colorado Plateau, etc. with velocities compatible with that reported on by Song et al.(1996). Five-second Rayleigh waves (Airy Phase) can be observed throughout the whole array and show a great deal of variation ( up to 30s). In general, the Love waves are better behaved than the Rayleigh waves. We are presently adding higher frequency to the source description by including source complexity. Preliminary inversions suggest rupture to northeast with a shallow asperity. We are, also, inverting the aftershocks to extend the frequencies to 2 Hz and beyond following the calibration method outlined in Tan and Helmberger (2007). This will allow accurate directivity measurements for events with magnitude larger than 3.5. Thus, we will address the energy decay with distance as s function of frequency band for the various source types.« less

Source Parameters of the 8 October, 2005 Mw7.6 Kashmir Earthquake

NASA Astrophysics Data System (ADS)

Mandal, Prantik; Chadha, R. K.; Kumar, N.; Raju, I. P.; Satyamurty, C.

2007-12-01

During the last six years, the National Geophysical Research Institute, Hyderabad has established a semi-permanent seismological network of 5 broadband seismographs and 10 accelerographs in the Kachchh seismic zone, Gujarat, with the prime objective to monitor the continued aftershock activity of the 2001 Mw7.7 Bhuj mainshock. The reliable and accurate broadband data for the Mw 7.6 (8 Oct., 2005) Kashmir earthquake and its aftershocks from this network, as well as from the Hyderabad Geoscope station, enabled us to estimate the group velocity dispersion characteristics and the one-dimensional regional shear-velocity structure of peninsular India. Firstly, we measure Rayleigh- and Love-wave group velocity dispersion curves in the range of 8 to 35 sec and invert these curves to estimate the crustal and upper mantle structure below the western part of peninsular India. Our best model suggests a two-layered crust: The upper crust is 13.8-km thick with a shear velocity (Vs) of 3.2 km/s; the corresponding values for the lower crust are 24.9 km and 3.7 km/sec. The shear velocity for the upper mantle is found to be 4.65 km/sec. Based on this structure, we perform a moment tensor (MT) inversion of the bandpass (0.05 0.02 Hz) filtered seismograms of the Kashmir earthquake. The best fit is obtained for a source located at a depth of 30 km, with a seismic moment, Mo, of 1.6 × 1027 dyne-cm, and a focal mechanism with strike 19.5°, dip 42°, and rake 167°. The long-period magnitude (MA ~ Mw) of this earthquake is estimated to be 7.31. An analysis of well-developed sPn and sSn regional crustal phases from the bandpassed (0.02 0.25 Hz) seismograms of this earthquake at four stations in Kachchh suggests a focal depth of 30.8 km.

Tunnel Design by Rock Mass Classifications

DTIC Science & Technology

1990-01-01

exhibited a slaking-like action when submerged . This is attributed to stress re- lief by coring. Bedding strikes roughly north-south and generally dips...dure ic diagrammatically depicted in Figure D5. This system, knorn as the Modified Basic RMR system or MBR in short, is based on experience gained in an

Geology of the region of Guadalajara, Mexico, and its relationships with processes of subsidence

NASA Astrophysics Data System (ADS)

Suarez-Plascencia, C.; Delgado-Argote, L. A.; Nuñez-Cornu, F. J.; Sanchez, J. J.

2008-12-01

The city of Guadalajara, Mexico, began an accelerated urban growth in early 1950. During a span of 25 years a large number of gullies were artificially filled, with the aim of incorporating new areas for urbanization, particularly in the areas north and west of the city. These gullies originally formed a complex dendritic-type system, whose evolution may be associated with faults or fracture zones whose current identification are only possible based on escarpments along the Canyon of the Rio Grande de Santiago (CRGS), north of Guadalajara. Reports of affectations documented in the 80's described subsidence in buildings and infrastructure, a process that has been continued during 2008. We present the results of work done in the CRGS, which is a tectonic erosive-depression with an average depth of 500 m and exhibits a sequence of volcanic and sedimentary deposits with rapid lateral facies changes. The stratigraphic column spans a 15 km-long section along the Matatlán-Arcediano road, and, from top to bottom contains: 1) Unconsolidated pumice and tuffs with an average thickness of 12 m; 2) basaltic lavas with average thickness of 60 m; 3) the San Gaspar ignimbrite; 4) fluvial- sedimentary deposits with a thickness of approximately 20 meters that include both sub-rounded and angular volcanic clasts, with sizes up to 0.15 m; 5) a thick sequence of ignimbrites and dacitic lavas. At a depth of 1200 m.a.s.l. in the town of Arcediano, the basal sequence is composed of dacites and andesites with interbedded pumice-rich ignimbrites with 10-20 m thickness. The Rio Grande de Santiago talweg to 1018 m.a.s.l. (apparently the base of the sequence) is formed by andesite lava. In the area of San Gaspar we identified oblique-normal left-lateral faults in lavas, with a strike 191° and a dip 89°. In the Colimilla dam, 1297 m.a.s.l., we observed normal faulting (strike 267° and dip 81°), with 20-30 m jumps with reference to a unit of tephra of 3-10 m thickness. The lavas in this site present deformation, the main shear being parallel to the Rio Verde. At the site of the San Gaspar river the faults have a strike of 285° and a dip of 83v and affect ignimbrites that overlie dacitic lavas. In the area of the Arcediano bridge the normal faulting has a strike 188v and dip of 75° in andesites, and in the pumice-rich ignimbrites a shear direction with strike of 92° and dip of 84° that is parallel to the Rio Verde. During the past two years we identified approximately 1100 cases of sinking with varying magnitude in the urban area of Guadalajara. Some of these can be grouped to form alignments that are oriented with the faults identified in the CRGS region. The process of subsidence can be controlled by structures that affect the pumice sequence laying under the city of Guadalajara, facilitating the movement of groundwater through areas of weakness, removing tuffs and pumice and creating voids that later collapse, affecting buildings and infrastructure in the city.

3D Dynamic Rupture Simulations along Dipping Faults, with a focus on the Wasatch Fault Zone, Utah

NASA Astrophysics Data System (ADS)

Withers, K.; Moschetti, M. P.

2017-12-01

We study dynamic rupture and ground motion from dip-slip faults in regions that have high-seismic hazard, such as the Wasatch fault zone, Utah. Previous numerical simulations have modeled deterministic ground motion along segments of this fault in the heavily populated regions near Salt Lake City but were restricted to low frequencies ( 1 Hz). We seek to better understand the rupture process and assess broadband ground motions and variability from the Wasatch Fault Zone by extending deterministic ground motion prediction to higher frequencies (up to 5 Hz). We perform simulations along a dipping normal fault (40 x 20 km along strike and width, respectively) with characteristics derived from geologic observations to generate a suite of ruptures > Mw 6.5. This approach utilizes dynamic simulations (fully physics-based models, where the initial stress drop and friction law are imposed) using a summation by parts (SBP) method. The simulations include rough-fault topography following a self-similar fractal distribution (over length scales from 100 m to the size of the fault) in addition to off-fault plasticity. Energy losses from heat and other mechanisms, modeled as anelastic attenuation, are also included, as well as free-surface topography, which can significantly affect ground motion patterns. We compare the effect of material structure and both rate and state and slip-weakening friction laws have on rupture propagation. The simulations show reduced slip and moment release in the near surface with the inclusion of plasticity, better agreeing with observations of shallow slip deficit. Long-wavelength fault geometry imparts a non-uniform stress distribution along both dip and strike, influencing the preferred rupture direction and hypocenter location, potentially important for seismic hazard estimation.

Deep seismic reflection images of the Wharton Basin oceanic crust and uppermost mantle offshore Northern Sumatra: Relation with active and past deformation

NASA Astrophysics Data System (ADS)

Carton, Hélène; Singh, Satish C.; Hananto, Nugroho D.; Martin, James; Djajadihardja, Yusuf S.; Udrekh; Franke, Dieter; Gaedicke, Christoph

2014-01-01

present deep seismic reflection images along two profiles collected in 2006 in the Wharton Basin offshore Northern Sumatra. The main profile is located subparallel to the Sumatran trench at a distance of 32-66 km. Faulting of the entire sedimentary section (strike-slip deformation sometimes accompanied by a dip-slip component) is imaged over two fracture zones of the extinct Wharton Spreading Center that prior studies have shown to be reactivated as left-lateral faults. The western fracture zone is associated with a wide region of strong basement topography, a difference in crustal thickness of 1.5 km, and an age offset of 9 Ma. The epicenters of the 11 April 2012 Mw 8.6 great strike-slip earthquake, its Mw 7.2 foreshock, and Mw 8.2 aftershock align along this major structure > 100 km south of the profile intersection. Our high-quality long-offset seismic reflection data also reveal bright dipping reflections extending down to a maximum of 24 km into the oceanic mantle ( 37 km below sea level). Apparent dips are mostly 25-35°, corresponding to 30-55° along either N-S to NNE-SSW or E-W to WNW-ESE directions, which encompass the directions of plate fabric and nodal planes of the Mw 8.6 event. We suggest that these enigmatic reflections arise from presently inactive dip-slip fault planes reaching for the deepest ones to the base of the brittle layer. Possible origins include extension related to plate bending or an episode of now inactive thrust-type deformation reactivating paleonormal faults, similar to that taking place in the Central Indian Basin.

Calibration of a pitot-static rake

NASA Technical Reports Server (NTRS)

Stump, H. P.

1977-01-01

A five-element pitot-static rake was tested to confirm its accuracy and determine its suitability for use at Langley during low-speed tunnel calibration primarily at full-scale tunnel. The rake was tested at one airspeed of 74 miles per hour (33 meters per second) and at pitch and yaw angles of 0 to + or - 20 degrees in 4 deg increments.

The state of stress in the limb of the Split Mountain anticline, Utah: constraints placed by transected joints

NASA Astrophysics Data System (ADS)

Silliphant, Laura J.; Engelder, Terry; Gross, Michael R.

2002-01-01

Transected joints (i.e. systematic joints that strike at an angle to the present fold axis trend) occur on the flanks of Split Mountain, a Laramide anticline near the eastern end of the Uinta Mountains, Utah. The common orientation on both flanks for these WNW-striking joints is inconsistent with joints driven by a syn-folding stretch normal to the direction of highest curvature. A smaller dispersion of the poles to these transected joints occurs when they are rotated with bedding to their 'pre-fold' orientation. This dispersion of poles is inconsistent with a post-fold genesis in a regional stress field but permits the possibility that these WNW joints propagated as a systematic set prior to Laramide folding. A pre-fold interpretation is substantiated by a regional WNW-striking joint set within Cretaceous and older rocks in the surrounding Piceance, Uinta, and southeastern Sand Wash basins. During tilting accompanying the upfolding of Split Mountain, most joints of this WNW-striking regional set remain locked without slipping under a shear stress. Fracture toughness and frictional strength are two rock properties that serve to lock a joint until a critical resolved shear stress is achieved. A gravity load caused down-dip slip on some joints that were tilted to a dip of about 62°. This suggests that a local principal stress remained roughly vertical during bedding rotation. Assuming fracture strength and friction prevented slip on most joints during tilting, the ratio of least horizontal, Sh, to vertical stress, Sv, at the critical tilt angle was approximately 0.55.

Aftershocks illuminate the 2011 Mineral, Virginia, earthquake causative fault zone and nearby active faults

USGS Publications Warehouse

Horton, J. Wright; Shah, Anjana K.; McNamara, Daniel E.; Snyder, Stephen L.; Carter, Aina M

2015-01-01

Deployment of temporary seismic stations after the 2011 Mineral, Virginia (USA), earthquake produced a well-recorded aftershock sequence. The majority of aftershocks are in a tabular cluster that delineates the previously unknown Quail fault zone. Quail fault zone aftershocks range from ~3 to 8 km in depth and are in a 1-km-thick zone striking ~036° and dipping ~50°SE, consistent with a 028°, 50°SE main-shock nodal plane having mostly reverse slip. This cluster extends ~10 km along strike. The Quail fault zone projects to the surface in gneiss of the Ordovician Chopawamsic Formation just southeast of the Ordovician–Silurian Ellisville Granodiorite pluton tail. The following three clusters of shallow (<3 km) aftershocks illuminate other faults. (1) An elongate cluster of early aftershocks, ~10 km east of the Quail fault zone, extends 8 km from Fredericks Hall, strikes ~035°–039°, and appears to be roughly vertical. The Fredericks Hall fault may be a strand or splay of the older Lakeside fault zone, which to the south spans a width of several kilometers. (2) A cluster of later aftershocks ~3 km northeast of Cuckoo delineates a fault near the eastern contact of the Ordovician Quantico Formation. (3) An elongate cluster of late aftershocks ~1 km northwest of the Quail fault zone aftershock cluster delineates the northwest fault (described herein), which is temporally distinct, dips more steeply, and has a more northeastward strike. Some aftershock-illuminated faults coincide with preexisting units or structures evident from radiometric anomalies, suggesting tectonic inheritance or reactivation.

Borehole-geophysical investigation of the University of Connecticut landfill, Storrs, Connecticut

USGS Publications Warehouse

Johnson, Carole D.; Haeni, F.P.; Lane, John W.; White, Eric A.

2002-01-01

A borehole-geophysical investigation was conducted to help characterize the hydrogeology of the fractured-rock aquifer and the distribution of unconsolidated glacial deposits near the former landfill and chemical waste-disposal pits at the University of Connecticut in Storrs, Connecticut. Eight bedrock boreholes near the landfill and three abandoned domestic wells located nearby were logged using conventional and advanced borehole-geophysical methods from June to October 1999. The conventional geophysical-logging methods included caliper, gamma, fluid temperature, fluid resistivity, and electromagnetic induction. The advanced methods included deviation, optical and acoustic imaging of the borehole wall, heat-pulse flowmeter, and directional radar reflection. Twenty-one shallow piezometers (less than 50-feet deep) were logged with gamma and electromagnetic induction tools to delineate unconsolidated glacial deposits. Five additional shallow bedrock wells were logged with conventional video camera, caliper, electromagnetic induction, and fluid resistivity and temperature tools. The rock type, foliation, and fracturing of the site were characterized from high-resolution optical-televiewer (OTV) images of rocks penetrated by the boreholes. The rocks are interpreted as fine- to medium-grained quartz-feldspar-biotite-garnet gneiss and schist with local intrusions of quartz diorite and pegmatite and minor concentrations of sulfide mineralization similar to rocks described as the Bigelow Brook Formation on regional geologic maps. Layers containing high concentrations of sulfide minerals appear as high electrical conductivity zones on electromagnetic-induction and borehole-radar logs. Foliation in the rocks generally strikes to the northeast-southwest and dips to the west, consistent with local outcrop observations. The orientation of foliation and small-scale gneissic layering in the rocks, however, varies locally and with depth in some of the boreholes. In two of the boreholes, the foliation strikes predominantly to the northwest and dips to the northeast. Although small-scale faults and lithologic discontinuities were observed in the OTV data, no large-scale faults were observed that appear on regional geologic maps. Fractures were located and characterized through the use of conventional geophysical, OTV, acoustic-televiewer (ATV), and borehole-radar logs. The orientation of fractures varies considerably across the site; some fractures are parallel to the foliation, whereas others cross-cut the foliation. Many of the transmissive fractures in the bedrock boreholes strike about N170?E and N320?E with dips of less than 45?. Other transmissive fractures strike about N60?E with dips of more than 60?. Most of the transmissive fractures in the domestic wells strike about N60?E and N22?E with dips of more than 45?. The strike of N60?E is parallel to the trend of a thrust fault that appears on regional geologic maps. Vertical flow in the boreholes was measured with the heat-pulse flowmeter under ambient and (or) pumping conditions. Results of ATV, OTV, and conventional logs were used to locate specific zones for flowmeter testing. Ambient downflow was measured in three boreholes, ambient upflow was measured in two other boreholes, and both ambient downflow and upflow were measured in a sixth borehole. The other five bedrock boreholes and domestic wells did not have measurable vertical flow. The highest rate of ambient flow was measured in the background borehole in which upflow and downflow converged and exited the borehole at a fracture zone near a depth of 62 feet. Ambient flow of about 340 gallons per day was measured. In the other five wells, ambient flow of about 20 to 35 gallons per day was measured. Under low-rate pumping (0.25 to 1 gallon per minute), one to six inflow zones were identified in each well. Usually the fractures that are active under ambient conditions contribute to the well under pumping conditions. To prevent

Effect of Geometric Parameters on the Performance of Second Throat Annular Steam Ejectors

DTIC Science & Technology

1991-07-01

Cell Pressure versus Rake Average Exit Pitot Pressure . . . . . . . . . . . 42 15. Baseline Wall Pressure Profiles...diffuser exit plane pitot pressure rake . 2.5.2 Alternate Configurations Six alternate ejector diffuser configurations were tested. A summary of...along the walls of the diffusers to help characterize the flow. The ejector diffuser exit pitot pressure was measured with a 6-probe pitot pressure rake

KIC 8462852: Potential Repeat of the Kepler Day 1540 Dip in 2017 August

NASA Astrophysics Data System (ADS)

Bourne, Rafik; Gary, Bruce

2017-12-01

We report 33 V-band observations by the Hereford Arizona Observatory (HAO) of the enigmatic star KIC 8462852 during the two week period 3-17 August 2017. We find a striking resemblance of these observations to the Kepler day 1540 dip with HAO observations tracking the Kepler light curve (adjusted for egress symmetry). A possible explanation of this potential repeat transit is a brown dwarf and extensive ring system in a 1601-day eccentric orbit. We suggest this object may be detectable through radial velocity observations in October and November 2017, with an amplitude of ~ 1-2 kms-1.

Pluton emplacement within an extensional transfer zone during dextral strike-slip faulting: an example from the late Archaean Abitibi Greenstone Belt

NASA Astrophysics Data System (ADS)

Lacroix, S.; Sawyer, E. W.; Chown, E. H.

1998-01-01

The Lake Abitibi area within the late Archaean Abitibi Greenstone Belt exhibits an interlinked plutonic, structural and metamorphic evolution that may characterize segmented strike-slip faults at upper-to-mid-crustal levels. Along the major, southeastward propagating Macamic D2 dextral strike-slip fault, Theological and preexisting D1 structural heterogeneities induced the development of NNW-trending dextral-oblique splays which evolved into an extensional trailing fan and created an extensional, NNW-dipping stepover. Magma flowing upwards from deeper parts of the Macamic Fault spread towards the southeast at upper crustal levels along both the oblique-slip and extensional D2 splays, and built several plutons in a pull-apart domain between 2696 and 2690 Ma. Different emplacement and material transfer mechanisms operated simultaneously in different parts of the system, including fault dilation and wedging, lateral expansion, wall-rock ductile flow and stoping. Transfer of movement between D2 splays occurred under ductile conditions during syn-emplacement, amphibolite-grade metamorphism (500-700 °C). During cooling (< 2690 Ma), narrower brittle-ductile zones of greenschist-grade shearing were concentrated along the pluton-wall rock contacts, but the extensional stepover locked since both normal and reverse movements occurred along NNW-dipping faults. Pluton emplacement, contact metamorphism and propagation of D2 faults appear to have been closely linked during the Superior Province-wide late transpressional event.

Structural Controls of the Emerson Pass Geothermal System, Washoe County, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Ryan B; Faulds, James E

We have conducted a detailed geologic study to better characterize a blind geothermal system in Emerson Pass on the Pyramid Lake Paiute Tribe Reservation, western Nevada. A thermal anomaly was discovered in Emerson Pass by use of 2 m temperature surveys deployed within a structurally favorable setting and proximal to surface features indicative of geothermal activity. The anomaly lies at the western edge of a broad left step at the northeast end of Pyramid Lake between the north- to north-northeast-striking, west-dipping, Fox and Lake Range normal faults. The 2-m temperature surveys have defined a N-S elongate thermal anomaly that hasmore » a maximum recorded temperature of ~60°C and resides on a north- to north-northeaststriking fault. Travertine mounds, chalcedonic silica veins, and silica cemented Pleistocene lacustrine gravels in Emerson Pass indicate a robust geothermal system active at the surface in the recent past. Structural complexity and spatial heterogeneities of the strain and stress field have developed in the step-over region, but kinematic data suggest a WNW-trending (~280° azimuth) extension direction. The geothermal system is likely hosted in Emerson Pass as a result of enhanced permeability generated by the intersection of two oppositely dipping, southward terminating north- to north-northwest-striking (Fox Range fault) and northnortheast- striking faults.« less

Near Field Small Earthquake Long Period Spectrum

DTIC Science & Technology

1976-04-01

L. Fredrickson, personal communication). The main shock occurred eight seconds after a magnitude 4.5 foreshock , and according to T. V. McEvilly...the strike (but rat the dip) of this plar^e is in good agreenant with that (IT C90 W) obtained from a faultplane solution for a large foreshock 0

Analysis of fractures from borehole televiewer logs in a 500m deep hole at Xiaguan, Yunnan province, Southwest China

USGS Publications Warehouse

Zhai, Qingshan; Springer, J.E.; Zoback, M.D.

1990-01-01

Fractures from a 500 m deep hole in the Red River fault zone were analyzed using an ultrasonic borehole televiewer. Four hundred and eighty individual fractures were identified between 19 m and 465 m depth. Fracture frequency had no apparent relation to the major stratigraphic units and did not change systematically with depth. Fracture orientation, however, did change with stratigraphic position. The borehole intersected 14 m of Cenozoic deposits, 363 m of lower Ordovician clastic sediments, and 106 m of older ultramafic intrusions. The clastic sequence was encountered again at a depth of 484 m, suggesting a large fault displacement. Fractures in the top 162 m of the sedimentary section appear randomly distributed. Below that depth, they are steeply dipping with northerly and north-westerly strikes, parallel to the major active faults in the region. Fractures in the ultramafic section strike roughly eastwest and are steeply dipping. These orientations are confined to the ultramafic section and are parallel to an older, inactive regional fault set. ?? 1990.

Continentward-Dipping Normal Faults, Boudinage and Ductile Shear at Rifted Passive Margins

NASA Astrophysics Data System (ADS)

Clerc, C. N.; Ringenbach, J. C.; Jolivet, L.; Ballard, J. F.

2017-12-01

Deep structures resulting from the rifting of the continental crust are now well imaged by seismic profiles. We present a series of recent industrial profiles that allow the identification of various rift-related geological processes such as crustal boudinage, ductile shear of the base of the crust and low-angle detachment faulting. Along both magma-rich and magma-poor rifted margins, we observe clear indications of ductile deformation of the deep continental crust. Large-scale shallow dipping shear zones are identified with a top-to-the-continent sense of shear. This sense of shear is consistent with the activity of the Continentward-Dipping Normal Faults (CDNF) that accommodate the extension in the upper crust. This pattern is responsible for an oceanward migration of the deformation and of the associated syn-tectonic deposits (sediments and/or volcanics). We discuss the origin of the Continentward-Dipping Normal Faults (CDNF) and investigate their implications and the effect of sediment thermal blanketing on crustal rheology. In some cases, low-angle shear zones define an anastomosed pattern that delineates boudin-like structures that seem to control the position and dip of upper crustal normal faults. We present some of the most striking examples from several locations (Uruguay, West Africa, South China Sea…), and discuss their rifting histories that differ from the classical models of oceanward-dipping normal faults.

A Bayesian inversion for slip distribution of 1 Apr 2007 Mw8.1 Solomon Islands Earthquake

NASA Astrophysics Data System (ADS)

Chen, T.; Luo, H.

2013-12-01

On 1 Apr 2007 the megathrust Mw8.1 Solomon Islands earthquake occurred in the southeast pacific along the New Britain subduction zone. 102 vertical displacement measurements over the southeastern end of the rupture zone from two field surveys after this event provide a unique constraint for slip distribution inversion. In conventional inversion method (such as bounded variable least squares) the smoothing parameter that determines the relative weight placed on fitting the data versus smoothing the slip distribution is often subjectively selected at the bend of the trade-off curve. Here a fully probabilistic inversion method[Fukuda,2008] is applied to estimate distributed slip and smoothing parameter objectively. The joint posterior probability density function of distributed slip and the smoothing parameter is formulated under a Bayesian framework and sampled with Markov chain Monte Carlo method. We estimate the spatial distribution of dip slip associated with the 1 Apr 2007 Solomon Islands earthquake with this method. Early results show a shallower dip angle than previous study and highly variable dip slip both along-strike and down-dip.

Congruence between muscle activity and kinematics in a convergently derived prey-processing behavior.

PubMed

Konow, Nicolai; Camp, Ariel L; Sanford, Christopher P J

2008-08-01

Quantification of anatomical and physiological characteristics of the function of a musculoskeletal system may yield a detailed understanding of how the organizational levels of morphology, biomechanics, kinematics, and muscle activity patterns (MAPs) influence behavioral diversity. Using separate analyses of these organizational levels in representative study taxa, we sought patterns of congruence in how organizational levels drive behavioral modulation in a novel raking prey-processing behavior found in teleosts belonging to two evolutionarily distinct lineages. Biomechanically divergent prey (elusive, robust goldfish and sedentary, malleable earthworms) were fed to knifefish, Chitala ornata (Osteoglossomorpha) and brook trout, Salvelinus fontinalis (Salmoniformes). Electromyography recorded MAPs from the hyoid protractor, jaw adductor, sternohyoideus, epaxialis, and hypaxialis musculature, while sonomicrometry sampled deep basihyal kinesis and contractile length dynamics in the basihyal protractor and retractor muscles. Syntheses of our results with recent analyses of cranial morphology and raking kinematics showed that raking in Salvelinus relies on an elongated cranial out lever, extensive cranial elevation and a curved cleithrobranchial ligament (CBL), and that both raking MAPs and kinematics remain entirely unmodulated-a highly unusual trait, particularly among feeding generalists. Chitala had a shorter CBL and a raking power stroke involving increased retraction of the elongated pectoral girdle during raking on goldfish. The raking MAP was also modulated in Chitala, involving an extensive overlap between muscle activity of the preparatory and power stroke phases, driven by shifts in hypaxial timing and recruitment of the hyoid protractor muscle. Sonomicrometry revealed that the protractor hyoideus muscle stored energy from retraction of the pectoral girdle for ca. 5-20 ms after onset of the power stroke and then hyper-extended. This mechanism of elastic recoil in Chitala, which amplifies retraction of the basihyal during raking on goldfish without a significant increase in recruitment of the hypaxialis, suggests a unique mechanism of modulation based on performance-enhancing changes in the design and function of the musculoskeletal system.

INL Seismic Monitoring Annual Report: January 1, 2006 - December 31, 2006

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. J. Payne; N. S. Carpenter; J. M. Hodges

During 2006, the Idaho National Laboratory (INL) recorded 1998 independent triggers from earthquakes both within the region and from around the world. Fifteen small to moderate size earthquakes ranging in magnitude from 3.0 to 4.5 occurred within and outside the 161-km (100-mile) radius of INL. There were 357 earthquakes with magnitudes up to 4.5 that occurred within the 161-km radius of the INL. The majority of earthquakes occurred in the Basin and Range Province surrounding the eastern Snake River Plain (ESRP). The largest of these earthquakes had a body-wave magnitude (mb) 4.5 and occurred on February 5, 2006. It wasmore » located northeast of Spencer, Idaho near the east-west trending Centennial fault along the Idaho-Montana border. The earthquake did not trigger SMAs located within INL buildings. Three earthquakes occurred within the ESRP, two of which occurred within the INL boundaries. One earthquake of coda magnitude (Mc) 1.7 occurred on October 18, 2006 and was located southeast of Pocatello, Idaho. The two earthquakes within the INL boundaries included the local magnitude (ML) 2.0 on July 31, 2006 located near the southern termination of the Lemhi fault and the Mc 0.4 on August 6, 2006 located near the center of INL. The ML 2.0 earthquake was well recorded by most of the INL seismic stations and had a focal depth of 8.98 km. First motions were used to compute a focal mechanism, which indicated normal faulting along one of two possible fault planes that may strike N76ºW and dip 70±3ºSW or strike N55ºW and dip 20±13ºNE. Slip along a normal fault that strikes N76ºW and dips 70±3ºSW is consistent with slip along a possible segment of the NW-trending Lemhi normal fault.« less

High-resolution seismic profiling reveals faulting associated with the 1934 Ms 6.6 Hansel Valley earthquake (Utah, USA)

USGS Publications Warehouse

Bruno, Pier Paolo G.; Duross, Christopher; Kokkalas, Sotirios

2017-01-01

The 1934 Ms 6.6 Hansel Valley, Utah, earthquake produced an 8-km-long by 3-km-wide zone of north-south−trending surface deformation in an extensional basin within the easternmost Basin and Range Province. Less than 0.5 m of purely vertical displacement was measured at the surface, although seismologic data suggest mostly strike-slip faulting at depth. Characterization of the origin and kinematics of faulting in the Hansel Valley earthquake is important to understand how complex fault ruptures accommodate regions of continental extension and transtension. Here, we address three questions: (1) How does the 1934 surface rupture compare with faults in the subsurface? (2) Are the 1934 fault scarps tectonic or secondary features? (3) Did the 1934 earthquake have components of both strike-slip and dip-slip motion? To address these questions, we acquired a 6.6-km-long, high-resolution seismic profile across Hansel Valley, including the 1934 ruptures. We observed numerous east- and west-dipping normal faults that dip 40°−70° and offset late Quaternary strata from within a few tens of meters of the surface down to a depth of ∼1 km. Spatial correspondence between the 1934 surface ruptures and subsurface faults suggests that ruptures associated with the earthquake are of tectonic origin. Our data clearly show complex basin faulting that is most consistent with transtensional tectonics. Although the kinematics of the 1934 earthquake remain underconstrained, we interpret the disagreement between surface (normal) and subsurface (strike-slip) kinematics as due to slip partitioning during fault propagation and to the effect of preexisting structural complexities. We infer that the 1934 earthquake occurred along an ∼3-km wide, off-fault damage zone characterized by distributed deformation along small-displacement faults that may be alternatively activated during different earthquake episodes.

3D geodynamic models for the development of opposing continental subduction zones: The Hindu Kush-Pamir example

NASA Astrophysics Data System (ADS)

Liao, Jie; Gerya, Taras; Thielmann, Marcel; Webb, A. Alexander G.; Kufner, Sofia-Katerina; Yin, An

2017-12-01

The development of opposing continental subduction zones remains scantly explored in three dimensions. The Hindu Kush-Pamir orogenic system at the western end of the Himalayan orogen provides a rare example of continental collision linked to two opposing intra-continental subduction zones. The subducted plates feature a peculiar 3D geometry consisting of two distinct lithospheric fragments with different polarities, subduction angles and slab-curvatures beneath the Hindu Kush and Pamir, respectively. Using 3D geodynamic modeling, we simulate possible development of two opposing continental subduction zones to understand the dynamic evolution of the Hindu Kush-Pamir orogenic system. Our geodynamic model reproduces the major tectonic elements observed: (1) the deeper subduction depth, the steeper dip angle and the southward offset of the Hindu Kush subduction zone relative to the Pamir naturally occur if convergence direction of the subducting Indian plate and dip-direction of the Hindu Kush subduction zone match. (2) The formation of the highly asymmetrically curved Pamir region and the south-dipping subduction is promoted by the initial geometry of the indenting Indian lithosphere together with the existence of a major strike-slip fault on the eastern margin of the Pamir region. (3) Subduction of only the lower continental crust during continental collision can occur if the coupling between upper and lower crusts is weak enough to allow a separation of these two components, and that (4) the subduction of mainly lower crust then facilitates that conditions for intermediate-depth seismicity can be reached. (5) The secondary tectonic features modeled here such as strike-slip-fault growth, north-northwest striking extension zone, and lateral flow of the thickened ductile upper crust are comparable to the current tectonics of the region. (6) Model results are further compared to the potentially similar orogenic system, i.e., the Alpine orogen, in terms of the curved Western Alpine arc and the two opposing subducted slabs beneath the Alps and the Dinarides.

Role of strike-slip faulting in the evolution of allochthonous terranes in the Philippines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karig, D.E.; Sarewitz, D.R.; Haeck, G.D.

1986-10-01

Concepts of allochthonous terrane transport and emplacement are dominated by the assumption that most terranes originate on the subducting plate, collide with the upper plate, and are emplaced there. Movement of terranes along the convergent margin is recognized but is generally attributed to postcollision slip. In the northern Philippines, allochthonous terranes originate primarily within the arc system, have been translated along it by strike-slip faults, and were emplaced by cessation of that slip. The authors suggest that in the Philippines some originally vertical strike-slip boundaries may have evolved into shallow-dipping sutures marked by fold and thrust systems. This mode ofmore » terrane evolution may be more common than generally appreciated, particularly in orogenic belts developed in response to oblique convergence.« less

Focal mechanisms and the stress regime in NE and SW Tanzania, East Africa

NASA Astrophysics Data System (ADS)

Brazier, Richard A.; Nyblade, Andrew A.; Florentin, Juliette

2005-07-01

We report 12 new focal mechanisms from earthquakes in NE and SW Tanzania where the stress regime within the East African rift system is not well constrained. Focal mechanisms for events at the intersection of the Lake Tanganyika and Rukwa rifts in SW Tanzania indicate a complicated stress pattern with possible dextral strike-slip motion on some faults but oblique motion on others (either sinistral on NW striking faults or dextral on NE striking faults). Within the Rukwa rift, focal mechanisms indicate normal dip-slip motion with NE-SW opening. In NE Tanzania where the Eastern rift impinges on the margin of the Tanzania Craton, fault motions are consistent with a zone of distributed block faults and sub E-W extension. All twelve earthquakes likely nucleated within the crust.

Miocene extension and extensional folding in an anticlinal segment of the Black Mountains accommodation zone, Colorado River extensional corridor, southwestern United States

USGS Publications Warehouse

Varga, R.J.; Faulds, J.E.; Snee, L.W.; Harlan, S.S.; Bettison-Varga, L.

2004-01-01

Recent studies demonstrate that rifts are characterized by linked tilt domains, each containing a consistent polarity of normal faults and stratal tilt directions, and that the transition between domains is typically through formation of accommodation zones and generally not through production of throughgoing transfer faults. The mid-Miocene Black Mountains accommodation zone of southern Nevada and western Arizona is a well-exposed example of an accommodation zone linking two regionally extensive and opposing tilt domains. In the southeastern part of this zone near Kingman, Arizona, east dipping normal faults of the Whipple tilt domain and west dipping normal faults of the Lake Mead domain coalesce across a relatively narrow region characterized by a series of linked, extensional folds. The geometry of these folds in this strike-parallel portion of the accommodation zone is dictated by the geometry of the interdigitating normal faults of opposed polarity. Synclines formed where normal faults of opposite polarity face away from each other whereas anticlines formed where the opposed normal faults face each other. Opposed normal faults with small overlaps produced short folds with axial trends at significant angles to regional strike directions, whereas large fault overlaps produce elongate folds parallel to faults. Analysis of faults shows that the folds are purely extensional and result from east/northeast stretching and fault-related tilting. The structural geometry of this portion of the accommodation zone mirrors that of the Black Mountains accommodation zone more regionally, with both transverse and strike-parallel antithetic segments. Normal faults of both tilt domains lose displacement and terminate within the accommodation zone northwest of Kingman, Arizona. However, isotopic dating of growth sequences and crosscutting relationships show that the initiation of the two fault systems in this area was not entirely synchronous and that west dipping faults of the Lake Mead domain began to form between 1 m.y. to 0.2 m.y. prior to east dipping faults of the Whipple domain. The accommodation zone formed above an active and evolving magmatic center that, prior to rifting, produced intermediate-composition volcanic rocks and that, during rifting, produced voluminous rhyolite and basalt magmas. Copyright 2004 by the American Geophysical Union.

Effect of a Material Contrast on a Dynamic Rupture: 3-D

NASA Astrophysics Data System (ADS)

Harris, R. A.; Day, S. M.

2003-12-01

We use numerical simulations of spontaneously propagating ruptures to examine the effect of a material contrast on earthquake dynamics. We specifically study the case of a lateral contrast whereby the fault is the boundary between two different rock-types. This scenario was previously studied in two-dimensions by Harris and Day [BSSA, 1997], and Andrews and Ben-Zion [JGR, 1997], in addition to subsequent 2-D studies, but it has not been known if the two-dimensional results are applicable to the real three-dimensional world. The addition of the third dimension implies a transition from pure mode II (i.e., plane-strain) to mixed-mode crack dynamics, which is more complicated since in mode II the shear and normal stresses are coupled whereas in mode III (i.e., anti-plane strain) they are not coupled. We use a slip-weakening fracture criterion and examine the effect on an earthquake rupture of material contrasts of up to 50 percent across the fault zone. We find a surprisingly good agreement between our earlier 2-D results, and our 3-D results for along-strike propagation. We find that the analytical solution presented in Harris and Day [BSSA, 1997] does an excellent job at predicting the bilateral, along-strike rupture velocities for the three-dimensional situation. In contrast, the along-dip propagation behaves much as expected for a purely mode-III rupture, with the rupture velocities up-dip and down-dip showing the expected symmetries.

Design and Calibration of a Flowfield Survey Rake for Inlet Flight Research

NASA Technical Reports Server (NTRS)

Flynn, Darin C.; Ratnayake, Nalin A.; Frederick, Michael

2009-01-01

Flowfield rake was designed to quantify the flowfield for inlet research underneath NASA DFRC s F-15B airplane. Detailed loads and stress analysis performed using CFD and empirical methods to assure structural integrity. Calibration data were generated through wind tunnel testing of the rake. Calibration algorithm was developed to determine the local Mach and flow angularity at each probe. RAGE was flown November, 2008. Data is currently being analyzed.

Heat Transfer Due to Shock Wave Turbulent Boundary Layer Interactions on High Speed Weapon Systems

DTIC Science & Technology

1974-04-01

Thermocouple Location. ............ 20 8 Pressure Tap LoceL.lons ............ 23 9 Pitot Pressurp Rake Detail and Profile Measurement Stations... Pitot Pressure Profile Measurements - Pitot pressure measure- ments were made with a NASA Langley five-probe pitot pressure rake at the axial location...defined in Figure 6. Figure 9 is a schematic illustration providing the dimensions of the rake and the pitot pressure profile measure- ment stations. The

Geomorphic and Structural Evidence for Rolling Hinge Style Deformation in the Footwall of an Active Low Angle Normal Fault, Mai'iu Fault, Woodlark Rift, SE Papua New Guinea

NASA Astrophysics Data System (ADS)

Mizera, M.; Little, T.; Norton, K. P.; Webber, S.; Ellis, S. M.; Oesterle, J.

2016-12-01

While shown to operate in oceanic crust, rolling hinge style deformation remains a debated process in metamorpic core complexes (MCCs) in the continents. The model predicts that unloading and isostatic uplift during slip causes a progressive back-tilting in the upper crust of a normal fault that is more steeply dipping at depth. The Mai'iu Fault in the Woodlark Rift, SE Papua New Guinea, is one of the best-exposed and fastest slipping (probably >7 mm/yr) active low-angle normal faults (LANFs) on Earth. We analysed structural field data from this fault's exhumed slip surface and footwall, together with geomorphic data interpreted from aerial photographs and GeoSAR-derived digital elevation models (gridded at 5-30 m spacing), to evaluate deformational processes affecting the rapidly exhuming, domal-shaped detachment fault. The exhumed fault surface emerges from the ground at the rangefront near sea level with a northward dip of 21°. Up-dip, it is well-preserved, smooth and corrugated, with some fault remnants extending at least 29 km in the slip direction. The surface flattens over the crest of the dome, beyond where it dips S at up to 15°. Windgaps perched on the crestal main divide of the dome, indicate both up-dip tectonic advection and progressive back-tilting of the exhuming fault surface. We infer that slip on a serial array of m-to-km scale up-to-the-north, steeply S-dipping ( 75°) antithetic-sense normal faults accommodated some of the exhumation-related, inelastic bending of the footwall. These geomorphically well expressed faults strike parallel to the main Mai'iu fault at 110.9±5°, have a mean cross-strike spacing of 1520 m, and slip with a consistent up-to-the-north sense of throw ranging from <5 m to 120 m. Apparently the Mai'iu Fault was able to continue slipping despite having to negotiate this added fault-roughness. We interpret the antithetic faulting to result from bending stresses, and to provide the first clear examples of rolling hinge-style accommodation structures on a continental MCC.

The 12 June 2017 Mw 6.3 Lesvos Island (Aegean Sea) earthquake: Slip model and directivity estimated with finite-fault inversion

NASA Astrophysics Data System (ADS)

Kiratzi, Anastasia

2018-01-01

On 12 June 2017 (UTC 12:28:38.26) a magnitude Mw 6.3 earthquake occurred offshore Lesvos Island in SE Aegean Sea, which was widely felt, caused 1 fatality, and partially ruined the village of Vrisa on the south-eastern coast of the island. I invert broad band and strong motion waveforms from regional stations to obtain the source model and the distribution of slip onto the fault plane. The hypocentre is located at a depth of 7 km in the upper crust. The mainshock ruptured a WNW-ESE striking, SW dipping, normal fault, projecting offshore and bounding the Lesvos Basin. The strongest and most aftershocks clustered away from the hypocentre, at the eastern edge of the activated area. This cluster indicates the activation of a different fault segment, exhibiting sinistral strike-slip motions, along a plane striking WNW-ESE. The slip of the mainshock is confined in a single large asperity, WNW from the hypocentre, with dimensions 20 km × 10 km along fault strike and dip, respectively. The average slip of the asperity is 50 cm and the peak slip is 1 m. The rupture propagated unilaterally towards WNW to the coastline of Lesvos island at a relatively high speed ( 3.1 km/s). The imaged slip model and forward modelling was used to calculate peak ground velocities (PGVs) in the near-field. The damage pattern produced by this earthquake, especially in the village of Vrisa is compatible with the combined effect of rupture directivity, proximity to the slip patch and the fault edge, spectral content of motions, and local site conditions.

Progressive deformation of the Chugach accretionary complex, Alaska, during a paleogene ridge-trench encounter

USGS Publications Warehouse

Kusky, Timothy M.

1997-01-01

The Mesozoic accretionary wedge of south-central Alaska is cut by an array of faults including dextral and sinistral strike-slip faults, synthetic and antithetic thrust faults, and synthetic and antithetic normal faults. The three fault sets are characterized by quartz ± calcite ± chlorite ± prehnite slickensides, and are all relatively late, i.e. all truncate ductile fabrics of the host rocks. Cross-cutting relationships suggest that the thrust fault sets predate the late normal and strike-slip fault sets. Together, the normal and strike-slip fault system exhibits orthorhombic symmetry. Thrust faulting shortened the wedge subhorizontally perpendicular to strike, and then normal and strike-slip faulting extended the wedge oblique to orogenic strike. Strongly curved slickenlines on some faults of each set reveal that displacement directions changed over time. On dip-slip faults (thrust and normal), slickenlines tend to become steeper with younger increments of slip, whereas on strike-slip faults, slickenlines become shallower with younger strain increments. These patterns may result from progressive exhumation of the accretionary wedge while the faults were active, with the curvature of the slickenlines tracking the change from a non-Andersonian stress field at depth to a more Andersonian system (σ1 or σ2 nearly vertical) at shallower crustal levels.We interpret this complex fault array as a progressive deformation that is one response to Paleocene-Eocene subduction of the Kula-Farallon spreading center beneath the accretionary complex because: (1) on the Kenai Peninsula, ENE-striking dextral faults of this array exhibit mutually cross-cutting relationships with Paleocene-Eocene dikes related to ridge subduction; and (2) mineralized strike-slip and normal faults of the orthorhombic system have yielded 40Ar/39Ar ages identical to near-trench intrusives related to ridge subduction. Both features are diachronous along-strike, having formed at circa 65 Ma in the west and 50 Ma in the east. Exhumation of deeper levels of the southern Alaska accretionary wedge and formation of this late fault array is interpreted as a critical taper adjustment to subduction of progressively younger oceanic lithosphere yielding a shallower basal de´collement dip as the Kula-Farallon ridge approached the accretionary prism. The late structures also record different kinematic regimes associated with subduction of different oceanic plates, before and after ridge subduction. Prior to triple junction passage, subduction of the Farallon plate occurred at nearly right angles to the trench axis, whereas after triple junction migration, subduction of the Kula plate involved a significant component of dextral transpression and northward translation of the Chugach terrane. The changes in kinematics are apparent in the sequence of late structures from: (1) thrusting; (2) near-trench plutonism associated with normal + strike-slip faulting; (3) very late gouge-filled dextral faults.

Geology and preliminary hydrogeologic characterization of the cell-house site, Berlin, New Hampshire, 2003-04

USGS Publications Warehouse

Degnan, James R.; Clark, Stewart F.; Harte, Philip T.; Mack, Thomas J.

2005-01-01

At the cell-house site, thin, generally less than 20-foot thick overburden, consisting of till and demolition materials, overlies fractured crystalline bedrock. Bedrock at the site consists of gneiss with thin discontinuous lenses of chlorite schist and discontinuous tabular pegmatite. Two distinct fracture domains, with principal trends to the west and northwest, and to the north, overlap near the site. The cell-house site shows principal trends common to both domains. Gneiss is the most abundant rock at the site. Steeply dipping fractures within the gneiss terminate on subhorizontal contacts with pegmatite and on moderately dipping contacts with chlorite schist. Steeply northwest-dipping en Echelon fracture zones, parallel joint zones, and silicified brittle faults show consistent strikes to the northeast. Gently east-dipping to subhorizontal fractures, sub-parallel to gneissosity, strike northeast. The impermeable cap, barrier wall, and bedrock surface topography affect ground-water flow in the overburden. There is relatively little ground-water flow in the overburden in the capped area and a poor hydraulic connection between the overburden and the underlying bedrock over most of the site. The overburden beneath the cap may receive inflow through or beneath the barrier wall, or by flow through vertical fractures in the underlying bedrock beneath the barrier wall. The bedrock aquifer near the river is well connected to the river and head difference in the bedrock across the site are large (greater than 13 ft). Horizontal hydraulic conductivities of 0.2 to 20 ft/d were estimated for the bedrock. Individual fractures or fracture zones likely have hydraulic conductivities greater than the bulk rock. Subhorizontal fractures occur at pegmatite contacts or along chlorite schist lenses and may serve as ground-water conduits to the steeply dipping fractures in gneiss. The effective hydraulic conductivity across the site is likely to be in the low range of the estimated values (0.2 ft/d). Ground water discharges to the river from the bedrock aquifer and is greatest during periods of large river stage fluctuations.

The numerical study of the rake angle of impeller blade in centrifugal compressor

NASA Astrophysics Data System (ADS)

Drozdov, A.; Galerkin, Y.

2017-08-01

Investigated impellers have blade surfaces formed by straight generatrix. Blade profiles on shroud and disc surfaces are optimized by velocity diagram control (inviscid, quasi-three dimensional calculations). The blade profiles at hub and shroud blade-to-blade surfaces must be coordinated. A designer can choose the generatrix position at a trailing edge for it. The position is defined by the rake angle that is the angle between a trailing edge generatrix and a meridional plane. Two stages with 3D impellers, vaneless diffusers and return channels were investigated. Seven candidates of impellers of these stages with rake angles in range plus-minus 30 degrees were designed and investigated by quasi-three-dimensional inviscid calculation. CFD-calculations were made for the stages with these impellers. The optimal rake angle is minus 20 degrees for the high flow rate impeller due to lesser blade surface area and favorable meridian velocity field. Zero rake angle is optimal for the medium flow rate impeller where blade surface area is not so important. The combination of inviscid and viscid calculations is the informative instrument for further studies.

34. HILLMAN BARGE AND CONSTRUCTION COMPANY EMPLOYEES EXAMINING BARGE RAKE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

34. HILLMAN BARGE AND CONSTRUCTION COMPANY EMPLOYEES EXAMINING BARGE RAKE PART PATTERN, NORTHWEST MOLD LOFT - Hillman Barge & Construction Company, Paul Thomas Boulevard, Brownsville, Fayette County, PA

Postseismic deformation associated with the 2008 Mw 7.9 Wenchuan earthquake, China: Constraining fault geometry and investigating a detailed spatial distribution of afterslip

NASA Astrophysics Data System (ADS)

Jiang, Zhongshan; Yuan, Linguo; Huang, Dingfa; Yang, Zhongrong; Chen, Weifeng

2017-12-01

We reconstruct two types of fault models associated with the 2008 Mw 7.9 Wenchuan earthquake, one is a listric fault connecting a shallowing sub-horizontal detachment below ∼20 km depth (fault model one, FM1) and the other is a group of more steeply dipping planes further extended to the Moho at ∼60 km depth (fault model two, FM2). Through comparative analysis of the coseismic inversion results, we confirm that the coseismic models are insensitive to the above two type fault geometries. We therefore turn our attention to the postseismic deformation obtained from GPS observations, which can not only impose effective constraints on the fault geometry but also, more importantly, provide valuable insights into the postseismic afterslip. Consequently, FM1 performs outstandingly in the near-, mid-, and far-field, whether considering the viscoelastic influence or not. FM2 performs more poorly, especially in the data-model consistency in the near field, which mainly results from the trade-off of the sharp contrast of the postseismic deformation on both sides of the Longmen Shan fault zone. Accordingly, we propose a listric fault connecting a shallowing sub-horizontal detachment as the optimal fault geometry for the Wenchuan earthquake. Based on the inferred optimal fault geometry, we analyse two characterized postseismic deformation phenomena that differ from the coseismic patterns: (1) the postseismic opposite deformation between the Beichuan fault (BCF) and Pengguan fault (PGF) and (2) the slightly left-lateral strike-slip motions in the southwestern Longmen Shan range. The former is attributed to the local left-lateral strike-slip and normal dip-slip components on the shallow BCF. The latter places constraints on the afterslip on the southwestern BCF and reproduces three afterslip concentration areas with slightly left-lateral strike-slip motions. The decreased Coulomb Failure Stress (CFS) change ∼0.322 KPa, derived from the afterslip with viscoelastic influence removed at the hypocentre of the Lushan earthquake, indicates that the postseismic left-lateral strike-slip and normal dip-slip motions may have a mitigative effect on the fault loading in the southwestern Longmen Shan range. Nevertheless, it is much smaller than the total increased CFS changes (∼8.368 KPa) derived from the coseismic and viscoelastic deformations.

Evolution of the stress fields in the Zagros Foreland Folded Belt using focal mechanisms and kinematic analyses: the case of the Fars salient, Iran

NASA Astrophysics Data System (ADS)

Sarkarinejad, Khalil; Zafarmand, Bahareh; Oveisi, Behnam

2018-03-01

The NW-SE trending Zagros orogenic belt was initiated during the convergence of the Afro-Arabian continent and the Iranian microcontinent in the Late Cretaceous. Ongoing convergence is confirmed by intense seismicity related to compressional stresses collision-related in the Zagros orogenic belt by reactivation of an early extensional faulting to latter compressional segmented strike-slip and dip-slip faulting. These activities are strongly related either to the deep-seated basement fault activities (deep-seated earthquakes) underlies the sedimentary cover or gently dipping shallow-seated décollement horizon of the rheological weak rocks of the infra-Cambrian Hormuz salt. The compressional stress regimes in the different units play an important role in controlling the stress conditions between the different units within the sedimentary cover and basement. A significant set of nearly N-S trending right-lateral strike-slip faults exists throughout the study area in the Fars area in the Zagros Foreland Folded Belt. Fault-slip and focal mechanism data were analyzed using the stress inversion method to reconstruct the paleo and recent stress conditions. The results suggest that the current direction of maximum principal stress averages N19°E, with N38°E that for the past from Cretaceous to Tertiary (although a few sites on the Kar-e-Bass fault yield a different direction). The results are consistent with the collision of the Afro-Arabian continent and the Iranian microcontinent. The difference between the current and paleo-stress directions indicates an anticlockwise rotation in the maximum principle stress direction over time. This difference resulted from changes in the continental convergence path, but was also influenced by the local structural evolution, including the lateral propagation of folds and the presence of several local décollement horizons that facilitated decoupling of the deformation between the basement and the sedimentary cover. The obliquity of the maximum compressional stress into the fault trends reveals a typical stress partitioning of thrust and strike-slip motion in the Kazerun, Kar-e-Bass, Sabz-Pushan, and Sarvestan fault zones that caused these fault zones behave as segmented strike-slip and dip-slip faults.

Scissoring Fault Rupture Properties along the Median Tectonic Line Fault Zone, Southwest Japan

NASA Astrophysics Data System (ADS)

Ikeda, M.; Nishizaka, N.; Onishi, K.; Sakamoto, J.; Takahashi, K.

2017-12-01

The Median Tectonic Line fault zone (hereinafter MTLFZ) is the longest and most active fault zone in Japan. The MTLFZ is a 400-km-long trench parallel right-lateral strike-slip fault accommodating lateral slip components of the Philippine Sea plate oblique subduction beneath the Eurasian plate [Fitch, 1972; Yeats, 1996]. Complex fault geometry evolves along the MTLFZ. The geomorphic and geological characteristics show a remarkable change through the MTLFZ. Extensional step-overs and pull-apart basins and a pop-up structure develop in western and eastern parts of the MTLFZ, respectively. It is like a "scissoring fault properties". We can point out two main factors to form scissoring fault properties along the MTLFZ. One is a regional stress condition, and another is a preexisting fault. The direction of σ1 anticlockwise rotate from N170°E [Famin et al., 2014] in the eastern Shikoku to Kinki areas and N100°E [Research Group for Crustral Stress in Western Japan, 1980] in central Shikoku to N85°E [Onishi et al., 2016] in western Shikoku. According to the rotation of principal stress directions, the western and eastern parts of the MTLFZ are to be a transtension and compression regime, respectively. The MTLFZ formed as a terrain boundary at Cretaceous, and has evolved with a long active history. The fault style has changed variously, such as left-lateral, thrust, normal and right-lateral. Under the structural condition of a preexisting fault being, the rupture does not completely conform to Anderson's theory for a newly formed fault, as the theory would require either purely dip-slip motion on the 45° dipping fault or strike-slip motion on a vertical fault. The fault rupture of the 2013 Barochistan earthquake in Pakistan is a rare example of large strike-slip reactivation on a relatively low angle dipping fault (thrust fault), though many strike-slip faults have vertical plane generally [Avouac et al., 2014]. In this presentation, we, firstly, show deep subsurface structures of the MTLFZ based on newly obtained data and previous research results. And then, we discuss how the relationship between the surface fault geometry and the deep subsurface structures changes through the MTLFZ which is under the heterogeneous regional stress condition.

Investigations on the Effect of Steady and Pulsed Surface. Thermal Perturbations on the Hypersonic Flow-Field Over a Flat Plate and a Sharp Cone

DTIC Science & Technology

2010-03-10

achieved by setting proper driver and driven pressures. A calibration of the tunnel was done for the decided freestream conditions with a pitot rake ...measurement. A rake of 12 pitot probes spanning the diameter of the nozzle (300 mm) was placed facing the freestream. The pitot pressures were... pitot rake and shock tube measurements, the freestream conditions for each of the observed rupture pressure are estimated. It was observed that of

Investigation of Differences Between Measured and Predicted Pressures in AEDC/VKF Hypersonic Tunnel B

DTIC Science & Technology

1997-01-01

coordinates are presented in Fig. 4b. The primary calibration data used in this paper is derived from the rake . The 42 pitot probes cov- ered a range...the lateral (YT) direction. Figures 5 and 6 show examples of the pitot pressure and total temperature rake data from a lateral survey and American...Figure 5. Rake pitot measurements, XT = 16 in. 0 10 YT, in. b. Local Mach number 20 Total Temperature Contours, R Static Temperature Contours, R

Characteristics of Perforated Diffusers at Free-Stream Mach Number 1.90

DTIC Science & Technology

1950-05-08

deg) Subscripts: 0 free stream 1 inlet entrance 2 Inlet throat 3 pitot -static rake in simulated combustion chamber 4 outlet of simulated...consisted of a 40-tube pitot -static survey rake located 0.55 combust Ion-chamber diameter downstream of the outlet of the subsonic diffuser (fig. 8(b...The rake was so designed that eaoh pitot -static tube was located at the oentroid of one of the forty equal area segments Into which the combustion

Astronaut Harrison Schmitt collects lunar rake samples during EVA

NASA Image and Video Library

1972-12-11

AS17-134-20425 (11 Dec. 1972) --- Scientist-astronaut Harrison H. Schmitt, lunar module pilot, collects lunar rake samples at Station 1 during the first Apollo 17 extravehicular activity (EVA) at the Taurus-Littrow landing site. This picture was taken by astronaut Eugene Cernan, commander. The lunar rake, an Apollo lunar geology hand tool, is used to collect discrete samples of rocks and rock chips ranging in size from one-half inch (1.3 centimeter) to one inch (2.5 centimeter).

Kinematic development of the Tibetan Plateau's northern margin: A traverse across the Qilian Shan-Nan Shan thrust belt

NASA Astrophysics Data System (ADS)

Zuza, A. V.; Levy, D. A.; Wang, Z.; Xiong, X.; Chen, X.

2017-12-01

The active Cenozoic Qilian Shan-Nan Shan thrust belt defines the northern margin of the Tibetan Plateau. The kinematic development of this thrust belt has implications models of plateau growth and Himalayan-Tibetan orogen strain accommodation. We present new field observations and analytical data from a traverse across the 350-km-wide doubly vergent Qilian Shan, which is bound by the south-dipping North Qilian thrust system in the north and the north-dipping range-bounding Qinghai Nanshan-Dulan Shan thrust system in the south. These faults, and several other major thrusts within the thrust-belt interior, disrupt relatively thick Oligocene-Miocene basin deposits. Of note, many of the thrust faults across the width of the Qilian Shan have Quaternary fault scarps, indicating that active deformation is distributed and not only concentrated along the northern frontal faults. By integrating our detailed structural traverse with new geophysical observations and thermochronology data across the northern plateau margin, we construct a kinematic model for the development of the Tibetan Plateau's northern margin. Deformation initiated in the Eocene-Oligocene along the north-dipping Qinghai Nanshan-Dulan Shan and south-dipping Tuolai Nan Shan thrusts, the latter of which then defined the northern boundary of the Tibetan Plateau. This early deformation was focused along preexisting early Paleozoic structures. A 200-km-wide basin formed between these ranges, and from the Miocene to present, new thrust- and strike-slip-fault-bounded ranges developed, including the north-directed North Qilian and the south-directed Tuolai Nan thrusts. Thus, our observations do not support northward propagating thrust-belt expansion. Instead, we envision that the initial thrust-belt development generated a wide Oligocene-Miocene north-plateau basin that was subsequently disintegrated by later Miocene to present thrusting and strike-slip faulting. Ultimately, the Qilian Shan-Nan Shan thrust belt differs from a typical orogenic thrust wedge, and active deformation is distributed across the range.

Geometry of the southern San Andreas fault and its implications for seismic hazard

NASA Astrophysics Data System (ADS)

Langenheim, V. E.; Dorsey, R. J.; Fuis, G. S.; Cooke, M. L.; Fattaruso, L.; Barak, S.

2015-12-01

The southern San Andreas fault (SSAF) provides rich opportunities for studying the geometry and connectivity of fault stepovers and intersections, including recently recognized NE tilting of the Salton block between the SSAF and San Jacinto fault (SJF) that likely results from slight obliquity of relative plate motion to the strike of the SSAF. Fault geometry and predictions of whether the SSAF will rupture through the restraining bend in San Gorgonio Pass (SGP) are controversial, with significant implications for seismic hazard. The evolution of faulting in SGP has led to various models of strain accommodation, including clockwise rotation of fault-bounded blocks east of the restraining bend, and generation of faults that siphon strike slip away from the restraining bend onto the SJF (also parallel to the SSAF). Complex deformation is not restricted to the upper crust but extends to mid- and lower-crustal depths according to magnetic data and ambient-noise surface-wave tomography. Initiation of the SJF ~1.2 Ma led to formation of the relatively intact Salton block, and end of extension on the West Salton detachment fault on the west side of Coachella Valley. Geologic and geomorphic data show asymmetry of the southern Santa Rosa Mountains, with a steep fault-bounded SW flank produced by active uplift, and gentler topographic gradients on the NE flank with tilted, inactive late Pleistocene fans that are incised by modern upper fan channels. Gravity data indicate the basin floor beneath Coachella Valley is also asymmetric, with a gently NE-dipping basin floor bound by a steep SSAF; seismic-reflection data suggest that NE tilting took place during Quaternary time. 3D numerical modeling predicts gentle NE dips in the Salton block that result from the slight clockwise orientation of relative motion across a NE-dipping SSAF. A NE dip of the SSAF, supported by various geophysical datasets, would reduce shaking in Coachella Valley compared to a vertical fault.

Comparison of conditional sampling and averaging techniques in a turbulent boundary layer

NASA Astrophysics Data System (ADS)

Subramanian, C. S.; Rajagopalan, S.; Antonia, R. A.; Chambers, A. J.

1982-10-01

A rake of cold wires was used in a slightly heated boundary layer to identify coherent temperature fronts. An X-wire/cold-wire arrangement was used simultaneously with the rake to provide measurements of the longitudinal and normal velocity fluctuations and temperature fluctuations. Conditional averages of these parameters and their products were obtained by application of conditional techniques (VITA, HOLE, BT, RA1, and RA3) based on the detection of temperature fronts using information obtained at only one point in space. It is found that none of the one-point detection techniques is in good quantitative agreement with the rake detection technique, the largest correspondence being 51%. Despite the relatively poor correspondence between the conditional techniques, these techniques, with the exception of HOLE, produce conditional averages that are in reasonable qualitative agreement with those deduced using the rake.

Development of a Rotating Rake Array for Boundary-Layer-Ingesting Fan-Stage Measurements

NASA Technical Reports Server (NTRS)

Wolter, John D.; Arend, David J.; Hirt, Stefanie M.; Gazzaniga, John A.

2017-01-01

The recent Boundary-Layer-Ingesting Inlet/Distortion Tolerant Fan wind tunnel experiment at NASA Glenn Research Center's 8- by 6-foot Supersonic Wind Tunnel (SWT) examined the performance of a novel inlet and fan stage that was designed to ingest the vehicle boundary layer in order to take advantage of a predicted overall propulsive efficiency benefit. A key piece of the experiment's instrumentation was a pair of rotating rake arrays located upstream and downstream of the fan stage. This paper examines the development of these rake arrays. Pre-test numerical solutions were sampled to determine placement and spacing for rake pressure and temperature probes. The effects of probe spacing and survey density on the repeatability of survey measurements was examined. These data were then used to estimate measurement uncertainty for the adiabatic efficiency.

Development of a Rotating Rake Array for Boundary-Layer-Ingesting Fan-Stage Measurements

NASA Technical Reports Server (NTRS)

Wolter, John D.; Arend, David J.; Hirt, Stefanie M.; Gazzaniga, John A.

2017-01-01

The recent Boundary-Layer-Ingesting Inlet/Distortion Tolerant Fan wind tunnel experiment at NASA Glenn Research Center's 8-foot by 6-foot supersonic wind tunnel examined the performance of a novel inlet and fan stage that was designed to ingest the vehicle boundary layer in order to take advantage of a predicted overall propulsive efficiency benefit. A key piece of the experiment's instrumentation was a pair of rotating rake arrays located upstream and downstream of the fan stage. This paper examines the development of these rake arrays. Pre-test numerical solutions were sampled to determine placement and spacing for rake pressure and temperature probes. The effects of probe spacing and survey density on the repeatability of survey measurements was examined. These data were then used to estimate measurement uncertainty for the adiabatic efficiency.

Source complexity of the 1987 Whittier Narrows, California, earthquake from the inversion of strong motion records

USGS Publications Warehouse

Hartzell, S.; Iida, M.

1990-01-01

Strong motion records for the Whittier Narrows earthquake are inverted to obtain the history of slip. Both constant rupture velocity models and variable rupture velocity models are considered. The results show a complex rupture process within a relatively small source volume, with at least four separate concentrations of slip. Two sources are associated with the hypocenter, the larger having a slip of 55-90 cm, depending on the rupture model. These sources have a radius of approximately 2-3 km and are ringed by a region of reduced slip. The aftershocks fall within this low slip annulus. Other sources with slips from 40 to 70 cm each ring the central source region and the aftershock pattern. All the sources are predominantly thrust, although some minor right-lateral strike-slip motion is seen. The overall dimensions of the Whittier earthquake from the strong motion inversions is 10 km long (along the strike) and 6 km wide (down the dip). The preferred dip is 30?? and the preferred average rupture velocity is 2.5 km/s. Moment estimates range from 7.4 to 10.0 ?? 1024 dyn cm, depending on the rupture model. -Authors

A Viscoelastic earthquake simulator with application to the San Francisco Bay region

USGS Publications Warehouse

Pollitz, Fred F.

2009-01-01

Earthquake simulation on synthetic fault networks carries great potential for characterizing the statistical patterns of earthquake occurrence. I present an earthquake simulator based on elastic dislocation theory. It accounts for the effects of interseismic tectonic loading, static stress steps at the time of earthquakes, and postearthquake stress readjustment through viscoelastic relaxation of the lower crust and mantle. Earthquake rupture initiation and termination are determined with a Coulomb failure stress criterion and the static cascade model. The simulator is applied to interacting multifault systems: one, a synthetic two-fault network, and the other, a fault network representative of the San Francisco Bay region. The faults are discretized both along strike and along dip and can accommodate both strike slip and dip slip. Stress and seismicity functions are evaluated over 30,000 yr trial time periods, resulting in a detailed statistical characterization of the fault systems. Seismicity functions such as the coefficient of variation and a- and b-values exhibit systematic patterns with respect to simple model parameters. This suggests that reliable estimation of the controlling parameters of an earthquake simulator is a prerequisite to the interpretation of its output in terms of seismic hazard.

Fault-based PSHA of an active tectonic region characterized by low deformation rates: the case of the Lower Rhine Graben

NASA Astrophysics Data System (ADS)

Vanneste, Kris; Vleminckx, Bart; Camelbeeck, Thierry

2016-04-01

The Lower Rhine Graben (LRG) is one of the few regions in intraplate NW Europe where seismic activity can be linked to active faults, yet probabilistic seismic hazard assessments of this region have hitherto been based on area-source models, in which the LRG is modeled as a single or a small number of seismotectonic zones with uniform seismicity. While fault-based PSHA has become common practice in more active regions of the world (e.g., California, Japan, New Zealand, Italy), knowledge of active faults has been lagging behind in other regions, due to incomplete tectonic inventory, low level of seismicity, lack of systematic fault parameterization, or a combination thereof. The past few years, efforts are increasingly being directed to the inclusion of fault sources in PSHA in these regions as well, in order to predict hazard on a more physically sound basis. In Europe, the EC project SHARE ("Seismic Hazard Harmonization in Europe", http://www.share-eu.org/) represented an important step forward in this regard. In the frame of this project, we previously compiled the first parameterized fault model for the LRG that can be applied in PSHA. We defined 15 fault sources based on major stepovers, bifurcations, gaps, and important changes in strike, dip direction or slip rate. Based on the available data, we were able to place reasonable bounds on the parameters required for time-independent PSHA: length, width, strike, dip, rake, slip rate, and maximum magnitude. With long-term slip rates remaining below 0.1 mm/yr, the LRG can be classified as a low-deformation-rate structure. Information on recurrence interval and elapsed time since the last major earthquake is lacking for most faults, impeding time-dependent PSHA. We consider different models to construct the magnitude-frequency distribution (MFD) of each fault: a slip-rate constrained form of the classical truncated Gutenberg-Richter MFD (Anderson & Luco, 1983) versus a characteristic MFD following Youngs & Coppersmith (1985). The summed Anderson & Luco fault MFDs show a remarkably good agreement with the MFD obtained from the historical and instrumental catalog for the entire LRG, whereas the summed Youngs & Coppersmith MFD clearly underpredicts low to moderate magnitudes, but yields higher occurrence rates for M > 6.3 than would be obtained by simple extrapolation of the catalog MFD. The moment rate implied by the Youngs & Coppersmith MFDs is about three times higher, but is still within the range allowed by current GPS uncertainties. Using the open-source hazard engine OpenQuake (http://openquake.org/), we compute hazard maps for return periods of 475, 2475, and 10,000 yr, and for spectral periods of 0 s (PGA) and 1 s. We explore the impact of various parameter choices, such as MFD model, GMPE distance metric, and inclusion of a background zone to account for lower magnitudes, and we also compare the results with hazard maps based on area-source models. References: Anderson, J. G., and J. E. Luco (1983), Consequences of slip rate constraints on earthquake occurrence relations, Bull. Seismol. Soc. Am., 73(2), 471-496. Youngs, R. R., and K. J. Coppersmith (1985), Implications of fault slip rates and earthquake recurrence models to probabilistic seismic hazard estimates, Bull. Seismol. Soc. Am., 75(4), 939-964.

Anomalous Electron Spectrum and Its Relation to Peak Structure of Electron Scattering Rate in Cuprate Superconductors

NASA Astrophysics Data System (ADS)

Gao, Deheng; Mou, Yingping; Feng, Shiping

2018-02-01

The recent discovery of a direct link between the sharp peak in the electron quasiparticle scattering rate of cuprate superconductors and the well-known peak-dip-hump structure in the electron quasiparticle excitation spectrum is calling for an explanation. Within the framework of the kinetic-energy-driven superconducting mechanism, the complicated line-shape in the electron quasiparticle excitation spectrum of cuprate superconductors is investigated. It is shown that the interaction between electrons by the exchange of spin excitations generates a notable peak structure in the electron quasiparticle scattering rate around the antinodal and nodal regions. However, this peak structure disappears at the hot spots, which leads to that the striking peak-dip-hump structure is developed around the antinodal and nodal regions, and vanishes at the hot spots. The theory also confirms that the sharp peak observed in the electron quasiparticle scattering rate is directly responsible for the remarkable peak-dip-hump structure in the electron quasiparticle excitation spectrum of cuprate superconductors.

Cornice Detail of Rake, Cornice Detail of Eave, Wood DoubleHung ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Cornice Detail of Rake, Cornice Detail of Eave, Wood Double-Hung Window Details, Wood Door Details - Boxley Grist Mill, Boxley vicinity on State Route 43, Buffalo National River, Ponca, Newton County, AR

Shock Boundary Layer Interaction Flow Control with Micro Vortex Generators

DTIC Science & Technology

2011-05-01

Pitot rake ( p̄02p01 ) u = time-averaged streamwise velocity ufs = time-averaged freestream streamwise velocity u∗ = √ τw ρw = wall-shear velocity w...upstream of the normal shock-wave 2 = station 2, at the Pitot rake location I. Introduction With the exception of the scramjet, all current air-breathing...to this.7 1 shock holder near-normal shock μVGs 123 143 14 hole Pitot rake 6o x vg variable φ cylinder mounted on the centre-line 380 M ∞ =1.4

Satellite diversity and its implications on the RAKE receiver architecture for CDMA-based S-PCN's

NASA Technical Reports Server (NTRS)

Taaghol, P.; Sammut, A.; Tafazolli, R.; Evans, B. G.

1995-01-01

In this paper we examine the applicability of RAKE receivers in a mobile LEO satellite channel and identify the potential problem areas. We then proceed to investigate the possibility of a coherent combining architecture (downlink) in the presence of satellite diversity. We closely examine the path delay difference statistics of a diversity channel and propose a delay compensation scheme for the downlink in order to reduce the complexity of the user terminal. Finally, the required modifications to the conventional RAKE receiver are proposed and discussed.

Astronaut Harrison Schmitt collects lunar rake samples during EVA

NASA Image and Video Library

1972-12-11

AS17-134-20426 (11 Dec. 1972) --- Scientist-astronaut Harrison H. Schmitt collects lunar rake samples at Station 1 during the first Apollo 17 extravehicular activity (EVA) at the Taurus-Littrow landing site. This picture was taken by astronaut Eugene A. Cernan, Apollo 17 commander. Schmitt is the lunar module pilot. The Lunar Rake, an Apollo Lunar Geology Hand Tool, is used to collect discrete samples of rocks and rock chips ranging in size from one-half inch (1.3 cm) to one inch (2.5 cm).

Dipping San Andreas and Hayward faults revealed beneath San Francisco Bay, California

USGS Publications Warehouse

Parsons, T.; Hart, P.E.

1999-01-01

The San Francisco Bay area is crossed by several right-lateral strike-slip faults of the San Andreas fault zone. Fault-plane reflections reveal that two of these faults, the San Andreas and Hayward, dip toward each other below seismogenic depths at 60?? and 70??, respectively, and persist to the base of the crust. Previously, a horizontal detachment linking the two faults in the lower crust beneath San Francisco Bay was proposed. The only near-vertical-incidence reflection data available prior to the most recent experiment in 1997 were recorded parallel to the major fault structures. When the new reflection data recorded orthogonal to the faults are compared with the older data, the highest, amplitude reflections show clear variations in moveout with recording azimuth. In addition, reflection times consistently increase with distance from the faults. If the reflectors were horizontal, reflection moveout would be independent of azimuth, and reflection times would be independent of distance from the faults. The best-fit solution from three-dimensional traveltime modeling is a pair of high-angle dipping surfaces. The close correspondence of these dipping structures with the San Andreas and Hayward faults leads us to conclude that they are the faults beneath seismogenic depths. If the faults retain their observed dips, they would converge into a single zone in the upper mantle -45 km beneath the surface, although we can only observe them in the crust.

Influence of fracture anisotropy on ground water ages and chemistry, Valley and Ridge province, Pennsylvania

USGS Publications Warehouse

Burton, W.C.; Plummer, Niel; Busenberg, E.; Lindsey, B.D.; Gburek, W.J.

2002-01-01

Model ground water ages based on chlorofluorocarbons (CFCs) and tritium/helium-3 (3H/3He) data were obtained from two arrays of nested piezometers located on the north limb of an anticline in fractured sedimentary rocks in the Valley and Ridge geologic province of Pennsylvania. The fracture geometry of the gently east plunging fold is very regular and consists predominately of south dipping to subhorizontal to north dipping bedding-plane parting and east striking, steeply dipping axial-plane spaced cleavage. In the area of the piezometer arrays, which trend north-south on the north limb of the fold, north dipping bedding-plane parting is a more dominant fracture set than is steeply south dipping axial-plane cleavage. The dating of ground water from the piezometer arrays reveals that ground water traveling along paths parallel to the dip direction of bedding-plane parting has younger 3H/3He and CFC model ages, or a greater component of young water, than does ground water traveling along paths opposite to the dip direction. In predominantly unmixed samples there is a strong positive correlation between age of the young fraction of water and dissolved sodium concentration. The travel times inferred from the model ages are significantly longer than those previously calculated by a ground water flow model, which assumed isotropically fractured layers parallel to topography. A revised model factors in the directional anisotropy to produce longer travel times. Ground water travel times in the watershed therefore appear to be more influenced by anisotropic fracture geometry than previously realized. This could have significant implications for ground water models in other areas underlain by similarly tilted or folded sedimentary rock, such as elsewhere in the Valley and Ridge or the early Mesozoic basins.

F-16XL ship #1 - CAWAP outboard rakes #7 and inboard rack #3

NASA Technical Reports Server (NTRS)

1996-01-01

This photo shows the #7 outboard rake and the #3 inboard rake on the left wing of NASA's single-seat F-16XL (ship #1) used for the Cranked-Arrow Wing Aerodynamic Project (CAWAP) at Dryden Flight Research Center, Edwards, California. The modified airplane features a delta 'cranked-arrow' wing with strips of tubing along the leading edge to the trailing edge to sense static on the wing and obtain pressure distribution data. The right wing receives data on pressure distribution and the left wing has three types of instrumentation - preston tubes to measure local skin friction, boundary layer rakes to measure boundary layer profiles (the layer where the air interacts with the surfaces of a moving aircraft), and hot films to determine boundary layer transition locations. The first flight of CAWAP occurred on November 21, 1995, and the test program ended in April 1996.

Hydrogeology and simulation of groundwater flow in fractured rock in the Newark basin, Rockland County, New York

USGS Publications Warehouse

Yager, Richard M.; Ratcliffe, Nicholas M.

2011-01-01

Groundwater in the Newark basin aquifer flows primarily through discrete water-bearing zones parallel to the strike and dip of bedding, whereas flow perpendicular to the strike is restricted, thereby imparting anisotropy to the groundwater flow field. The finite-element model SUTRA was used to represent bedrock structure in the aquifer by spatially varying the orientation of the hydraulic conductivity tensor to reflect variations in the strike and dip of the bedding. Directions of maximum and medium hydraulic conductivity were oriented parallel to the bedding, and the direction of minimum hydraulic conductivity was oriented perpendicular to the bedding. Groundwater flow models were prepared to simulate local flow in the vicinity of the Spring Valley well field and regional flow through the Newark basin aquifer. The Newark basin contains sedimentary rocks deposited as alluvium during the Late Triassic and is one of a series of basins that developed when Mesozoic rifting of the super continent Pangea created the Atlantic Ocean. The westward-dipping basin is filled with interbedded facies of coarse-grained to fine-grained rocks that were intruded by diabase associated with Jurassic volcanism. The Newark basin aquifer is bounded to the north and east by the Palisades sill and to the west by the Ramapo Fault. Although the general dip of bedding is toward the fault, mapping of conglomerate beds indicates the rocks are folded into broad anticlines and synclines. An alternative, more uniform pattern of regional structure, based on interpolated strike and dip measurements from a number of sources, has also been proposed. Two groundwater flow models (A for the former type of bedrock structure and B for the latter type) were developed to represent these alternative depictions of bedrock structure. Transient simulations were calibrated to reproduce measured water-level recoveries in a 9.3 mi² area surrounding the Spring Valley well field during a 5-day aquifer test in 1992. The models represented a 330-ft thick rock mass divided vertically into 10 equally spaced layers and were calibrated through nonlinear regression. Results of model B best matched the observed water-level recoveries with an estimated hydraulic conductivity of 9.5 ft/day, specific storage of 7.6 x 10 -6 ft -1, and Kmax: Kmin anisotropy ratio (hydraulic conductivity parallel to bedding: perpendicular to bedding) of 72:1. Model error was 50 percent greater in model A because the assumed structure did not match the actual strike of bedding in this area. Steady-state simulations of regional flow through the 85.4-mi2 modeled extent of the Newark basin aquifer represented both the alluvial aquifer beneath the Mawah River and the fractured bedrock. The rock mass was divided into two aquifer units: an upper 500-ft thick unit divided into 10 equally spaced layers through which most groundwater is assumed to flow and a lower unit divided into 7 layers with increasing thickness. Models were calibrated through nonlinear regression to average water levels measured in 140 wells from August 2005 through April 2007. Water levels simulated using the two models were similar and generally matched those observed, and the average recharge rate estimated using both models was 19 inches/year for the simulated period. Estimated transmissivity parallel to the strike of bedding (1,100 ft²/d) was uniform in two transmissivity (T) zones in model A, but in model B the transmissivity of a high T zone (1,600 ft²/d), delineated on the basis of aquifer test data, was slightly greater than in a low T zone (1,300 ft²/d). The Kmax: Kmin anisotropy was estimated to be 58:1 in model A and 410:1 in model B, so the proportion of flow perpendicular to bedding is less in model B than in model A. Distributions of groundwater age simulated with models A and B are similar and indicate that most shallow ground-water (225 ft below the bedrock surface) is 5 t

Postmylonitic deformation in the Raft River metamorphic core complex, northwestern Utah: Evidence of a rolling hinge

NASA Astrophysics Data System (ADS)

Manning, Andrew H.; Bartley, John M.

1994-06-01

Much of the recent debate over low-angle normal faults exposed in metamorphic core complexes has centered on the rolling hinge model. The model predicts tilting of seismogenic high-angle normal faults to lower dips by footwall deformation in response to isostatic forces caused by footwall exhumation. This shallow brittle deformation should visibly overprint the mylonitic fabric in the footwall of a metamorphic core complex. The predicted style and magnitude of rolling hinge strain depends upon the macroscopic mechanism by which the footwall deforms. Two end-members have been proposed: subvertical simple shear and flexural failure. Each mechanism should generate a distinctive pattern of structures that strike perpendicular to the regional extension direction. Subvertical simple shear (SVSS) should generate subvertical faults and kink bands with a shear sense antithetic to the detachment. For an SVSS hinge, the hinge-related strain magnitude should depend only on initial fault dip; rolling hinge structures should shorten the mylonitic foliation by >13% for an initial fault dip of >30°. In flexural failure the footwall behaves as a flexed elastic beam that partially fails in response to bending stresses. Resulting structures include conjugate faults and kink bands that both extend and contract the mylonitic foliation. Extensional sets could predominate as a result of superposition of far-field and flexural stresses. Strain magnitudes do not depend on fault dip but depend on the thickness and radius of curvature of the flexed footwall beam and vary with location within that beam. Postmylonitic structures were examined in the footwall of the Raft River metamorphic core complex in northwestern Utah to test these predictions. Observed structures strike perpendicular to the regional extension direction and include joints, normal faults, tension-gash arrays, and both extensional and contractional kink bands. Aside from the subvertical joints, the extensional structures dip moderately to steeply and are mainly either synthetic to the detachment or form conjugate sets. Range-wide, the extensional structures accomplish about 4% elongation of the mylonitic foliation. Contractional structures dip steeply, mainly record shear antithetic to the detachment, and accomplish <1% contraction of the foliation. These observations are consistent with the presence of a rolling hinge in the Raft River Mountains, but a rolling hinge that reoriented a high-angle normal fault by SVSS is excluded. The pattern and magnitudes of strain favor hinge-related deformation mainly by flexural failure with a subordinate component of SVSS.

Post-magmatic tectonic deformation of the outer Izu-Bonin-Mariana forearc system: initial results of IODP Expedition 352

NASA Astrophysics Data System (ADS)

Kurz, Walter; Ferré, Eric C.; Robertson, Alastair; Avery, Aaron; Christeson, Gail L.; Morgan, Sally; Kutterorf, Steffen; Sager, William W.; Carvallo, Claire; Shervais, John; Party IODP Expedition 352, Scientific

2015-04-01

IODP Expedition 352 was designed to drill through the entire volcanic sequence of the Bonin forearc. Four sites were drilled, two on the outer fore arc and two on the upper trench slope. Site survey seismic data, combined with borehole data, indicate that tectonic deformation in the outer IBM fore arc is mainly post-magmatic. Post-magmatic extension resulted in the formation of asymmetric sedimentary basins such as, for example, the half-grabens at sites 352-U1439 and 352-U1442 located on the upper trench slope. Along their eastern margins these basins are bounded by west-dipping normal faults. Sedimentation was mainly syn-tectonic. The lowermost sequence of the sedimentary units was tilted eastward by ~20°. These tilted bedding planes were subsequently covered by sub-horizontally deposited sedimentary beds. Based on biostratigraphic constraints, the minimum age of the oldest sediments is ~ 35 Ma; the timing of the sedimentary unconformities lies between ~ 27 and 32 Ma. At sites 352-U1440 and 352-U1441, located on the outer forearc, post-magmatic deformation resulted mainly in strike-slip faults possibly bounding the sedimentary basins. The sedimentary units within these basins were not significantly affected by post-sedimentary tectonic tilting. Biostratigraphic ages indicate that the minimum age of the basement-cover contact lies between ~29.5 and 32 Ma. Overall, the post-magmatic tectonic structures observed during Expedition 352 reveal a multiphase tectonic evolution of the outer IBM fore arc. At sites 352-U1439 and 352-U1442, shear with dominant reverse to oblique reverse displacement was localized along distinct subhorizontal cataclastic shear zones as well as steeply dipping slickensides and shear fractures. These structures, forming within a contractional tectonic regime, were either re-activated as or cross-cut by normal-faults as well as strike-slip faults. Extension was also accommodated by steeply dipping to subvertical mineralized veins and extensional fractures. Faults observed at sites 352-U1440 and 352-U1441 show mainly strike-slip. The sediments overlying the igneous basement, of maximum Late Eocene to Recent age, document ash and aeolian input, together with mass wasting of the fault-bounded sediment ponds.

Relocation of the 2010-2013 near the north coast of Papua earthquake sequence using Modified Joint Hypocenter Determination (MJHD) method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salomo, Dimas, E-mail: dimas.salomo@gmail.com; Daryono,; Subakti, Hendri

The accuracy of earthquake hypocenter position is necessary to analyze the tectonic conditions. This study aims to: (1) relocate the mainshock and aftershocks of the large earthquakes in Papua region i.e. June 16, 2010, April 21, 2012 and April 06, 2013 earthquake (2) determine the true fault plane, (3) estimate the area of the fracture, and (4) analyze the advantages and disadvantages of relocation with MJHD method in benefits for tectonic studies. This study used Modified Joint Hypocenter Determination (MJHD) method. Using P arrival phase data reported by the BMKG and openly available from website repogempa.bmkg.go.id, we relocated the mainshockmore » of this large significant earthquake and its aftershocks. Then we identified the prefered fault planes from the candidate fault planes provided by the global CMT catalogue. The position of earthquakes was successfully relocated. The earthquakes mostly were clustered around the mainshock. Earthquakes that not clustered around mainshock are considered to be different mechanism from the mainshock. Relocation results indicate that the mainshock fault plane of June 16, 2010 earthquake is a field with strike 332o, dip 80o and −172o slip, the mainshock fault plane of April 21, 2012 earthquake is a field with strike 82o, dip 84o and 2o slip, the mainshock fault plane of April 06, 2013 earthquake is a field with strike 339o, dip 56o and −137o slip. Fault plane area estimated by cross section graphical method is an area of 2816.0 km2 (June 16, 2010), 906.2 km2 (April 21, 2012) and 1984.3 km2 (April 06, 2013). MJHD method has the advantage that it can calculate a lot of earthquakes simultaneously and has a station correction to account for lateral heterogeneity of the earth. This method successfully provides significant changes to improve the position of the depth of earthquakes that most of the hypocenter depth manually specified as a fixed depth (± 10 km). But this method cannot be sure that the hypocenters derived from the same earthquake mechanism.« less

Indicators of recent geodynamic activity in the Książ Castle area (Świebodzice Unit, Sudetes) in the light of structural analysis and geodetic measurements

NASA Astrophysics Data System (ADS)

Kasza, Damian; Kowalski, Aleksander; Wojewoda, Jurand; Kaczorowski, Marek

2018-01-01

Abstract. Indicators of recent geodynamic activity in the Książ Castle area are registered by the measuring instruments of the SRC PAS (Space Research Centre of Polish Academy of Sciences) Geodynamic Laboratory at Książ. Over 40 years of continuous observations from quartz horizontal pendulums (since 1974) and over 10 years of observations from water-tube tiltmeters (since 2002) have documented irregularly repeatable strong signals related to the relative displacement of blocks in the rock substrate, on which Książ Castle is located. These signals have dip (rotational) and vertical strike-slip components. Also, the presence of a horizontal strike-slip component is evidenced by geometric anomalies (deformations) of the shape of the Pelcznica river valley, which directly correspond to the orientation of the main faults in the area. Recent geodynamic activity is documented by destruction of (the construction elements in the castle complex. Instrumental indicators of movement, geodetic measurements and structural analysis of the rock massif have allowed for constructing a model showing the main unconformity surfaces in the analysed rock massif. Sinistral, NE-SW and ENE-WSW-oriented strike-slip faults prevail in the laboratory corridors, along with perpendicular WNW-ESE and NW-SSE-oriented clextral and normal faults. Most dislocations are accompanied by zones of intense cataclasys, secondary silification, and Fe and Mn mineralization. Generally, the faults were formed due to reactivation of joint fractures cutting the steeply N-and S-dipping (at 75-90°) deposits of the Książ Conglomerate Formation.

Heterogeneous Earth Structure, Deformation, and Slip During the 2010 Mw 7.2 El Mayor-Cucapah Earthquake from Geodetic Data

NASA Astrophysics Data System (ADS)

Huang, M. H.; Dickinson, H.; Fielding, E. J.; Sun, J.; Freed, A. M.; Burgmann, R.

2015-12-01

The 4th of April 2010 Mw 7.2 El Mayor-Cucapah (EMC) earthquake in Baja California and Sonora, Mexico has primarily right-lateral strike-slip motion and a minor normal slip component. The surface rupture extends about 120 km west of the boundary between the Pacific and the North American plates. The EMC event initiated near the center and ruptured bilaterally into an east-dipping strike-slip fault zone to the north and a west-dipping strike-slip zone to the south. Here we use geodetic measurements including GPS, InSAR (SAR interferometry), and sub-pixel offset measurements to characterize the fault slip during the EMC event. We use dislocation inversion methods to determine fault geometry as well as sub-fault slip distribution based on geodetic measurements. We find that assuming layered earth elastic structure increased the inferred deep slip (10-15 km depth) by up to 1.6 m (60%) compared to assuming a homogeneous elastic structure. Inferred slip was also strongly (up to 2 m) influenced by the choice of observational constraints used in the inversion. The choice of constraints also influenced the inverted seismic moment from Mw 7.20 to 7.26, and the difference is equivalent to a Mw 6.5 event. Our results show that the outcomes of coseismic inversions can vary greatly depending on the methodology, something that needs to be considered both for characterizing an earthquake and when using such results in subsequent studies of postseismic deformation.

STRUCTURAL CONTROLS OF THE EMERSON PASS GEOTHERMAL SYSTEM, NORTHWESTERN NEVADA: CHARACTERIZATION OF A "BLIND" SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Ryan B; Faulds, James E

Detailed geologic analyses have elucidated the kinematics, stress state, structural controls, and past surface activity of a blind geothermal system in Emerson Pass on the Pyramid Lake Paiute Reservation, western Nevada. The Emerson Pass area resides near the boundary of the Basin and Range and Walker Lane provinces and at the western edge of a broad left step or relay ramp between the north- to north-northeast-striking, west-dipping, Fox and Lake Range normal faults. The step-over provides a structurally favorable setting for deep circulation of meteoric fluids. Strata in the area are comprised of late Miocene to Pliocene sedimentary rocks andmore » the middle Miocene Pyramid sequence mafic to intermediate volcanic rocks, all overlying Mesozoic metasedimentary and intrusive rocks. A thermal anomaly was discovered in Emerson Pass by use of 2-m temperature surveys deployed within a structurally favorable setting and proximal to surface features indicative of geothermal activity. The 2-m temperature surveys define a north-south elongate thermal anomaly that has a maximum recorded temperature of ~60°C and resides on a north- to north-northeast-striking normal fault. Although the active geothermal system is expressed solely as a soil heat anomaly, late Pleistocene travertine and tufa mounds, chalcedonic silica/calcite veins, and silica cemented Pleistocene lacustrine gravels indicate a robust geothermal system was active at the surface in the recent past. The geothermal system is controlled primarily by the broad step-over between two major range-bounding normal faults. In detail, the system likely results from enhanced permeability generated by the intersection of two oppositely dipping, southward terminating north- to north-northwest-striking (Fox Range fault) and north-northeast-striking normal faults. Structural complexity and spatial heterogeneities of the strain and stress field have developed in the step-over region, but kinematic data suggest a west-northwest-trending (~280° azimuth) extension direction. Therefore, geothermal activity in the Emerson Pass area is probably hosted on north-to north-northeast striking normal faults.« less

Analysis of geodetic interseismic coupling models to estimate tsunami inundation and runup: a study case of Maule seismic gap, Chile

NASA Astrophysics Data System (ADS)

González-Carrasco, J. F.; Gonzalez, G.; Aránguiz, R.; Catalan, P. A.; Cienfuegos, R.; Urrutia, A.; Shrivastava, M. N.; Yagi, Y.; Moreno, M.

2015-12-01

Tsunami inundation maps are a powerful tool to design evacuation plans of coastal communities, additionally can be used as a guide to territorial planning and assessment of structural damages in port facilities and critical infrastructure (Borrero et al., 2003; Barberopoulou et al., 2011; Power et al., 2012; Mueller et al., 2015). The accuracy of inundation estimation is highly correlated with tsunami initial conditions, e.g. seafloor vertical deformation, displaced water volume and potential energy (Bolshakova et al., 2011). Usually, the initial conditions are estimated using homogeneous rupture models based in historical worst-case scenario. However tsunamigenic events occurred in central Chilean continental margin showed a heterogeneous slip distribution of source with patches of high slip, correlated with fully-coupled interseismic zones (Moreno et al., 2012). The main objective of this work is to evaluate the predictive capacity of interseismic coupling models based on geodetic data comparing them with homogeneous fault slip model constructed using scaling laws (Blaser et al., 2010) to estimate inundation and runup in coastal areas. To test our hypothesis we select a seismic gap of Maule, where occurred the last large tsunamigenic earthquake in the chilean subduction zone, using the interseismic coupling models (ISC) proposed by Moreno et al., 2011 and Métois et al., 2013. We generate a slip deficit distribution to build a tsunami source supported by geological information such as slab depth (Hayes et al., 2012), strike, rake and dip (Dziewonski et al., 1981; Ekström et al., 2012) to model tsunami generation, propagation and shoreline impact using Neowave 2D (Yamazaki et al., 2009). We compare the tsunami scenario of Mw 8.8, Maule based in coseismic slip distribution proposed by Moreno et al., 2012 with homogeneous and heterogeneous models to identify the accuracy of our results with sea level time series and regional runup data (Figure 1). The estimation of tsunami source using ISC model can be useful to improve the analysis of tsunami threat, based in more realistic slip distribution.

Seismic Scenario in the Acambay Graben and Possible Affectations in the Miguel Hidalgo Refinery

NASA Astrophysics Data System (ADS)

Valderrama Membrillo, S.; Aguirre, J.

2015-12-01

In this paper we presented synthetic acceleration records in the Miguel Hidalgo refinery, Hidalgo due to a seismic scenario originated in the graben Acambay, such as occurred in 1912 (70 km distance to it). This earthquake had a magnitude of 6.9 and caused extensive damage, according to reports caused 164 deaths and numerous houses collapsing. To simulate the event of M = 6.9 we used the empirical Greeńs function method proposed by Irikura (1986). Due to the low seismic activity we have not any small earthquake record or an "element earthquake" so that we generated a synthetic seismogram of M = 4.1 to be used as empirical Greeńs function. The seismogram was constructed in two parts. For low frequencies we constructed from cross-correlations of seismic noise, while for high frequencies we made a stochastic simulation. Subsequently, we applied a "matched filter" to join the two frequency bands of synthetic earthquake. For the construction of seismic scenario the method of Irikura (1986) was used. We consider a square fault of 47.75 km long, a radial rupture propagation, rupture velocity of 3.06 m/s, and with the following focal mechanism: strike of 280°, dip of 66 ° and rake of -138 °. With these parameters we obtained the synthetic seismograms. Since there was not any observed earthquake to validate the model, the 1912 event was simulated and then from relationships of intensity (obtained Wald et al.,2005; Sandoval et al., 2013; and Arias, 1969), we estimated the Modified Mercalli Intensity (MMI) for the refinery. We compare our result with isoseismal map obtained by Suter et al. (1996) for the earthquake of 1912. In agreement with Suter, our results shown a MMI V-VI for the Miguel Hidalgo refinery. With this qualitative validation we search the seismic scenario with the higher accelerations and from this synthetic seismogram, we obtained parameters that are of interest in engineering to estimate the possible affectations to the Miguel Hidalgo refinery, such as: PGA, PGV, response spectra, dominant period of significant duration event, and estimated MMI.

Waveform inversion in the frequency domain for the simultaneous determination of earthquake source mechanism and moment function

NASA Astrophysics Data System (ADS)

Nakano, M.; Kumagai, H.; Inoue, H.

2008-06-01

We propose a method of waveform inversion to rapidly and routinely estimate both the moment function and the centroid moment tensor (CMT) of an earthquake. In this method, waveform inversion is carried out in the frequency domain to obtain the moment function more rapidly than when solved in the time domain. We assume a pure double-couple source mechanism in order to stabilize the solution when using data from a small number of seismic stations. The fault and slip orientations are estimated by a grid search with respect to the strike, dip and rake angles. The moment function in the time domain is obtained from the inverse Fourier transform of the frequency components determined by the inversion. Since observed waveforms used for the inversion are limited in a particular frequency band, the estimated moment function is a bandpassed form. We develop a practical approach to estimate the deconvolved form of the moment function, from which we can reconstruct detailed rupture history and the seismic moment. The source location is determined by a spatial grid search using adaptive grid spacings, which are gradually decreased in each step of the search. We apply this method to two events that occurred in Indonesia by using data from a broad-band seismic network in Indonesia (JISNET): one northeast of Sulawesi (Mw = 7.5) on 2007 January 21, and the other south of Java (Mw = 7.5) on 2006 July 17. The source centroid locations and mechanisms we estimated for both events are consistent with those determined by the Global CMT Project and the National Earthquake Information Center of the U.S. Geological Survey. The estimated rupture duration of the Sulawesi event is 16 s, which is comparable to a typical duration for earthquakes of this magnitude, while that of the Java event is anomalously long (176 s), suggesting that this event was a tsunami earthquake. Our application demonstrates that this inversion method has great potential for rapid and routine estimations of both the CMT and the moment function, and may be useful for identification of tsunami earthquakes.

A trial of reliable estimation of non-double-couple component of microearthquakes

NASA Astrophysics Data System (ADS)

Imanishi, K.; Uchide, T.

2017-12-01

Although most tectonic earthquakes are caused by shear failure, it has been reported that injection-induced seismicity and earthquakes occurring in volcanoes and geothermal areas contain non double couple (non-DC) components (e.g, Dreger et al., 2000). Also in the tectonic earthquakes, small non-DC components are beginning to be detected (e.g, Ross et al., 2015). However, it is generally limited to relatively large earthquakes that the non-DC component can be estimated with sufficient accuracy. In order to gain further understanding of fluid-driven earthquakes and fault zone properties, it is important to estimate full moment tensor of many microearthquakes with high precision. In the last AGU meeting, we proposed a method that iteratively applies the relative moment tensor inversion (RMTI) (Dahm, 1996) to source clusters improving each moment tensor as well as their relative accuracy. This new method overcomes the problem of RMTI that errors in the mechanism of reference events lead to biased solutions for other events, while taking advantage of RMTI that the source mechanisms can be determined without a computation of Green's function. The procedure is briefly summarized as follows: (1) Sample co-located multiple earthquakes with focal mechanisms, as initial solutions, determined by an ordinary method. (2) Apply the RMTI to estimate the source mechanism of each event relative to those of the other events. (3) Repeat the step 2 for the modified source mechanisms until the reduction of total residual converges. In order to confirm whether the method can resolve non-DC components, we conducted numerical tests on synthetic data. Amplitudes were computed assuming non-DC sources, amplifying by factor between 0.2 and 4 as site effects, and adding 10% random noise. As initial solutions in the step 1, we gave DC sources with arbitrary strike, dip and rake angle. In a test with eight sources at 12 stations, for example, all solutions were successively improved by iteration. Non-DC components were successfully resolved in spite of the fact that we gave DC sources as initial solutions. The application of the method to microearthquakes in geothermal area in Japan will be presented.

Evaluation of beach grooming techniques on Escherichia coli density in foreshore sand at North Beach, Racine, WI

USGS Publications Warehouse

Kinzelman, Julie L.; Whitman, Richard L.; Byappanahalli, Muruleedhara N.; Jackson, Emma; Bagley, Robert C.

2003-01-01

Elevated levels of Escherichia coli(E. coli) in bathing waters at North Beach, a popular recreational site in Racine, Wisconsin, have been a persistent problem often resulting in the issuance of poor water quality advisories. Moreover, waterfowl (mostly Larus delawarensis and L. argentatus) in nearshore and offshore areas are common and may serve as non-point sources for bacterial contamination of recreational waters. Current beach management practice involves daily mechanical grooming of the nearshore sand for aesthetics and removal of hazardous debris. However, this practice has not been evaluated in terms of its effects on E. coli loading to beach sand and potential introduction to contiguous swimming water. In this study, we tested E. coli responses to three treatments: mechanical groomer, daily and twice weekly hand raking, and a control (no raking/grooming). A randomized block design consisted of replicated treatments and one control (10 each), for a total of 40 blocks sampled daily for 10 days. Foreshore sand samples were collected by hand coring to an average depth of 10 cm. Median E. colirecovered were 73 (mechanically groomed), 27 (hand-raked daily), 32 (hand-raked twice weekly), and 22 (control) colony-forming units (CFU) per gram dry weight sand. E. colicounts in sand that was groomed were significantly higher than hand rakings and control (p <0.0001), and there was no significant difference between control and raking treatments (p<0.01). This study demonstrates the beach management implications related to grooming efficacy and the importance of understanding non-point sources of bacterial contamination.

The brittle stage of the exhumation of a metamorphic core complex: Naxos, Cyclades, Greece and some general rules

NASA Astrophysics Data System (ADS)

Neubauer, F.; Cao, S.

2012-04-01

Structures of hangingwall units of major detachment systems in extensional settings leading to metamorphic core complexes are equally important to the generally well-studied footwall rocks. Here, we describe hanging-wall structures of the North-Cycladic Detachment System on Naxos Island of the Aegean Sea and found that they well monitor the structural evolution of hanging blocks complementary to the footwall structures, vertical fluid flow as well as late-stage inversion of the whole extensional system. On Naxos, Upper Oligocene-Miocene and Pliocene sedimentary successions are deposited on the hangingwall unit, which is largely an ophiolite. The Upper Oligocene-Miocene and Pliocene sedimentary successions are separated by a hiatus arguing for a two-step evolution. Whereas the first step, Miocene, indicate moderate subsidence and relief, and only denudation of the hangingwall unit, the Pliocene conglomerates indicate a sharply increasing relief and an over-steepened topography. Hydrothermal systems developed in hangingwall rock succession (e.g. Miocene at Steladia) play an important role and resulted in large-scale silica precipitation and associated alteration similar as these found in subvolcanic epithermal systems. This constrains a close link between footwall granodiorite intrusion and near-surface processes. The Pliocene coarse boulder conglomerate with its abundant first appearance of granite/granodiorite, and subsequent marble-rich debris on distant places like Palatia indicate a sudden erosion and high-gradient relief leading to erosion of the mantle of the migmatite dome during Pliocene. On Naxos, we recognize, therefore, a three-stage tectonic evolution in the hangingwall unit: (i) moderate subsidence of an Upper Oligocene-Miocene basin, in part below sea level; (2) a second stage with deposition of Pliocene coarse conglomerates, and (iii) post-Pliocene faulting affecting the conglomerates. During the second stage, surface exposure of the metamorphic core complex was reached resulting in catastrophic alluvial fans. Structural data from the Upper Oligocene-Miocene rocks indicate that NNE-SSW extension still prevailed up to the Miocene/Pliocene boundary. Together with structural data from Pliocene conglomerates, we can distinguish between three major events: The first stage is characterized by mostly NNE-dipping and subordinate SSW-dipping normal faults indicating together ca. NNE-SSW extension. A second palaeostress tensor group (B) mainly comprises ca. NW-trending dextral and WSW-trending sinistral strike-slip faults indicating together ca. E-W strike-slip compression and monitor, therefore, inversion and compression perpendicular to the previous extension direction. The third palaeostress tensor group (C) is characterized by dominating mostly NE-trending subvertical sinistral strike-slip faults and steep NNW-trending dextral strike-slip faults constituting together ca. N-S strike-slip compression. In a few cases, S- to SW-dipping reverse faults also occur. On a general level, our study allows for the following major conclusions: (1) Structures of hangingwall units of major detachments above metamorphic core complexes are equally important compared to the generally well-studied footwall rocks. They allow date several tectonic events not necessarily found in footwall rocks. (2) On Naxos, we can distinguish between three major tectonic events, which are in accordance with large-scale tectonic processes in the Aegean Sea: (a) ca. NNE-SSW extension; (b) ca. E-W strike-slip compression and monitor therefore inversion and compression perpendicular to the previous extension direction, and (c) N-S strike-slip compression.

Fractured-aquifer hydrogeology from geophysical logs; the passaic formation, New Jersey

USGS Publications Warehouse

Morin, R.H.; Carleton, G.B.; Poirier, S.

1997-01-01

The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding-plane partings and (2) high-angle fractures. Bedding-plane partings are the most numerous and have an average strike of N84??W and dip of 20??N. The high-angle fractures are oriented subparallel to these features, with an average strike of N79??E and dip of 71??S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east-west strike. Inspection of fluid temperature and conductance logs in conjunction with flowmeter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities of the logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding-plane partings exhibit transmissivities that average roughly 5 m2/day and that generally diminish in magnitude and frequency with depth. The high-angle fractures have average transmissivities that are about half those of the bedding-plane partings and show no apparent dependence upon depth. The geophysical logging results allow us to infer a distinct hydrogeologic structure within this aquifer that is defined by fracture type and orientation. Fluid flow near the surface is controlled primarily by the highly transmissive, subhorizontal bedding-plane partings. As depth increases, the high-angle fractures apparently become more dominant hydrologically.The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km2 area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was statistically reduced to two principal subsets corresponding to two distinct fracture types: (1) bedding-plane partings and (2) high-angle fractures. Bedding-plane partings are the most numerous and have an average strike of N84?? W and dip of 20?? N. The high-angle fractures are oriented subparallel to these features, with an average strike of N79?? E and dip of 71?? S, making the two fracture types roughly orthogonal. Their intersections form linear features that also retain this approximately east-west strike. Inspection of fluid temperature and conductance logs in conjunction with flowmeter measurements obtained during pumping allows the transmissive fractures to be distinguished from the general fracture population. These results show that, within the resolution capabilities of the logging tools, approximately 51 (or 18 percent) of the 280 total fractures are water producing. The bedding-plane partings exhibit transmissivities that average roughly 5 m2/day and that generally dimi

Decomposing the electromagnetic response of magnetic dipoles to determine the geometric parameters of a dipole conductor

NASA Astrophysics Data System (ADS)

Desmarais, Jacques K.; Smith, Richard S.

2016-03-01

A novel automatic data interpretation algorithm is presented for modelling airborne electromagnetic (AEM) data acquired over resistive environments, using a single-component (vertical) transmitter, where the position and orientation of a dipole conductor is allowed to vary in three dimensions. The algorithm assumes that the magnetic fields produced from compact vortex currents are expressed as a linear combinations of the fields arising from dipoles in the subsurface oriented parallel to the [1, 0, 0], [0, 1, 0], and [0, 0, 1], unit vectors. In this manner, AEM responses can be represented as 12 terms. The relative size of each term in the decomposition can be used to determine geometrical information about the orientation of the subsurface conductivity structure. The geometrical parameters of the dipole (location, depth, dip, strike) are estimated using a combination of a look-up table and a matrix inverted in a least-squares sense. Tests on 703 synthetic models show that the algorithm is capable of extracting most of the correct geometrical parameters of a dipole conductor when three-component receiver data is included in the interpretation procedure. The algorithm is unstable when the target is perfectly horizontal, as the strike is undefined. Ambiguities may occur in predicting the orientation of the dipole conductor if y-component data is excluded from the analysis. Application of our approach to an anomaly on line 15 of the Reid Mahaffy test site yields geometrical parameters in reasonable agreement with previous authors. However, our algorithm provides additional information on the strike and offset from the traverse line of the conductor. Disparities in the values of predicted dip and depth are within the range of numerical precision. The index of fit was better when strike and offset were included in the interpretation procedure. Tests on the data from line 15701 of the Chibougamau MEGATEM survey shows that the algorithm is applicable to situations where three-component AEM data is available.

CLMSZ, Garnet Mountain area, southern California: A collisionally generated contractional shear zone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bracchi, K.A.; Girty, G.H.; Girty, M.S.

1993-04-01

The Harper Creek gneiss (HCg) and Oriflamme Canyon unit (OCu) underlie the central portion of the Cuyamaca Laguna Mountains shear zone (CLMSZ) in and around Garnet Mountain, Peninsular Ranges, California, and may have been deformed during Cretaceous arc-continent collision. U-Pb zircon work and petrological and geochemical analyses suggest that in the Garnet Mountain area, the 140 Ma HCg is derived from granite and granodiorite, whereas the 122 [+-] 1 Ma OCu is a protomylonite derived from a granite. Both units appear to be per aluminous calc-alkaline magmatic arc granitoids. Mineral assemblages suggest uppermost greenschist to lower amphibolite grade conditions duringmore » deformation. In the HCg, S-1hc is a mylonitic gneissosity with a mean attitude of N11W, 60 NE. A mineral streaking lineation lies within the plane of S-1hc and has a mean attitude of 61[degree] N76E. In the OCu, S-1oc strikes about N13W and dips 52 NE and contains a mineral streaking lineation with an attitude of 49 N52E. Dextral and sinistral shear bands, S-2d and S-2s (looking NW), transect S-1hc and S-1oc. S-2d and S-2s strike subparallel to S-1. In the HCg S-2s is weakly developed and dips about 32 NE, whereas S-2d is more dominant and dips about 76 NE. On the OCu these relationships are reversed. S-2d does not cross cut S-2s: hence, the two sets of shear bands are interpreted to be conjugates reflecting NE-SW contraction and subvertical extension during collisional development of the CLMSZ.« less

Characterization of hydrocarbon gas within the stratigraphic interval of gas-hydrate stability on the North Slope of Alaska, U.S.A.

USGS Publications Warehouse

Collett, T.S.; Kvenvolden, K.A.; Magoon, L.B.

1990-01-01

In the Kuparuk River Unit 2D-15 well, on the North Slope of Alaska, a 60 m-thick stratigraphic interval that lies within the theoretical pressure-temperature field of gas-hydrate stability is inferred to contain methane hydrates. This inference is based on interpretations from well logs: (1) release of methane during drilling, as indicated by the mud log, (2) an increase in acoustic velocity on the sonic log, and (3) an increase of electrical resistivity on the electric logs. Our objective was to determine the composition and source of the gas within the shallow gas-hydrate-bearing interval based on analyses of cutting gas. Headspace gas from canned drill cuttings collected from within the gas-hydrate-bearing interval of this well has an average methane to ethane plus propane [C1/(C2 + C3)] ratio of about 7000 and an average methane ??13C value of -46% (relative to the PDB standard). These compositions are compared with those obtained at one well located to the north of 2D-15 along depositional strike and one down-dip well to the northeast. In the well located on depositional strike (Kuparuk River Unit 3K-9), gas compositions are similar to those found at 2D-15. At the down-dip well (Prudhoe Bay Unit R-1), the C1/(C2 + C3) ratios are lower (700) and the methane ??13C is heavier (-33%). We conclude that the methane within the stratigraphic interval of gas hydrate stability comes from two sources-in situ microbial gas and migrated thermogenic gas. The thermal component is greatest at Prudhoe Bay. Up-dip to the west, the thermogenic component decreases, and microbial gas assumes more importance. ?? 1990.

3-D simulation of hanging wall effect at dam site

NASA Astrophysics Data System (ADS)

Zhang, L.; Xu, Y.

2017-12-01

Hanging wall effect is one of the near fault effects. This paper focuses on the difference of the ground motions on the hanging wall side between the footwall side of the fault at dam site considering the key factors, such as actual topography, the rupture process. For this purpose, 3-D ground motions are numerically simulated by the spectrum element method (SEM), which takes into account the physical mechanism of generation and propagation of seismic waves. With the SEM model of 548 million DOFs, excitation and propagation of seismic waves are simulated to compare the difference between the ground motion on the hanging wall side and that on the footwall side. Take Dagangshan region located in China as an example, several seismogenic finite faults with different dip angle are simulated to investigate the hanging wall effect. Furthermore, by comparing the ground motions of the receiving points, the influence of several factors on hanging wall effect is investigated, such as the dip of the fault and the fault type (strike slip fault or dip-slip fault). The peak acceleration on the hanging wall side is obviously larger than those on the footwall side, which numerically evidences the hanging wall effect. Besides, the simulation shows that only when the dip is less than 70° does the hanging wall effect deserve attention.

Rotating rake design for unique measurement of fan-generated spinning acoustic modes

NASA Technical Reports Server (NTRS)

Konno, Kevin E.; Hausmann, Clifford R.

1993-01-01

In light of the current emphasis on noise reduction in subsonic aircraft design, NASA has been actively studying the source of and propagation of noise generated by subsonic fan engines. NASA/LeRC has developed and tested a unique method of accurately measuring these spinning acoustic modes generated by an experimental fan. This mode measuring method is based on the use of a rotating microphone rake. Testing was conducted in the 9 x 15 Low-speed Wind Tunnel. The rotating rake was tested with the Advanced Ducted Propeller (ADP) model. This memorandum discusses the design and performance of the motor/drive system for the fan-synchronized rotating acoustic rake. This novel motor/drive design approach is now being adapted for additional acoustic mode studies in new test rigs as baseline data for the future design of active noise control for subsonic fan engines. Included in this memorandum are the research requirements, motor/drive specifications, test performance results, and a description of the controls and software involved.

Spectral stratigraphy

NASA Technical Reports Server (NTRS)

Lang, Harold R.

1991-01-01

A new approach to stratigraphic analysis is described which uses photogeologic and spectral interpretation of multispectral remote sensing data combined with topographic information to determine the attitude, thickness, and lithology of strata exposed at the surface. The new stratigraphic procedure is illustrated by examples in the literature. The published results demonstrate the potential of spectral stratigraphy for mapping strata, determining dip and strike, measuring and correlating stratigraphic sequences, defining lithofacies, mapping biofacies, and interpreting geological structures.

Fault zones ruptured during the early 2014 Cephalonia Island (Ionian Sea, Western Greece) earthquakes (January 26 and February 3, Mw 6.0) based on the associated co-seismic surface ruptures

NASA Astrophysics Data System (ADS)

Lekkas, Efthymios L.; Mavroulis, Spyridon D.

2016-01-01

The early 2014 Cephalonia Island (Ionian Sea, Western Greece) earthquake sequence comprised two main shocks with almost the same magnitude (moment magnitude (Mw) 6.0) occurring successively within a short time (January 26 and February 3) and space (Paliki peninsula in Western Cephalonia) interval. Εach earthquake was induced by the rupture of a different pre-existing onshore active fault zone and produced different co-seismic surface rupture zones. Co-seismic surface rupture structures were predominantly strike-slip-related structures including V-shaped conjugate surface ruptures, dextral and sinistral strike-slip surface ruptures, restraining and releasing bends, Riedel structures ( R, R', P, T), small-scale bookshelf faulting, and flower structures. An extensional component was present across surface rupture zones resulting in ground openings (sinkholes), small-scale grabens, and co-seismic dip-slip (normal) displacements. A compressional component was also present across surface rupture zones resulting in co-seismic dip-slip (reverse) displacements. From the comparison of our field geological observations with already published surface deformation measurements by DInSAR Interferometry, it is concluded that there is a strong correlation among the surface rupture zones, the ruptured active fault zones, and the detected displacement discontinuities in Paliki peninsula.

Kinematic stratification in the hinterland of the central Scandinavian Caledonides

USGS Publications Warehouse

Gilotti, J.A.; Hull, J.M.

1993-01-01

A transect through west-central Norway illustrates the changing geometry and kinematics of collision in the hinterland of the central Scandinavian Caledonides. A depth section through the crust is exposed on Fosen Peninsula, comprising three tectonic units separated by two shear zones. The lowest unit, exposed in the Roan window, is a modestly deformed, Caledonian granulite complex framed by a subhorizontal de??collement, with NW-SE oriented lineations and kinematic indicators showing top-to-the-northwest transport. The middle unit, the Vestranden gneiss complex, contains relict granulites, but was penetratively deformed at amphibolite facies to produce an orogen-parallel family of structures during translation on the de??collement. Shallow plunging lineations on steep schistosities are subparallel to fold axes of the dominant, upright, non-cylindrical folds. A small component of sinistral strike slip is also recorded. In contrast, southernmost Fosen Peninsula contains an abundance of cover rocks infolded with Proterozoic basement in a fold nappe, with shallow, E-dipping schistosities, down-dip lineations, and orogen-oblique, top-to-the-west shear sense indicators. A NE-striking, sinistral shear zone separates the gneisses from southern Fosen. Deformation in the Scandian hinterland was partitioned both in space and time, with orogen-parallel extension and shear at middle structural levels and orogen-oblique transport at shallower levels. ?? 1993.

5. UPSTREAM VIEW OF THE TRASH RAKES, GATES AND GATELIFTING ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. UPSTREAM VIEW OF THE TRASH RAKES, GATES AND GATE-LIFTING MECHANISMS FOR THE POST FALLS DAM AND POWERHOUSE, LOOKING NORTHWEST. - Washington Water Power Company Post Falls Power Plant, Middle Channel Powerhouse & Dam, West of intersection of Spokane & Fourth Streets, Post Falls, Kootenai County, ID

Effect of Cutting Angle and Depth of Cut on the Occurrence of Chipped Grain on Sycamore

Treesearch

Harold A. Stewart

1970-01-01

Sycamore specimens were planned with various combinations of depths of cut and rake angles. Depths of cut up to 1/16 inch had no significant effect on the occurrence of chipped grain in sycamore but rake angle did.

1. EXISTING TRASH RAKE STRUCTURE AND STEEL IBEAM TRACK, LOOKING ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. EXISTING TRASH RAKE STRUCTURE AND STEEL I-BEAM TRACK, LOOKING EAST/NORTHEAST. - Washington Water Power Spokane River Upper Falls Hydroelectric Development, Gates & Gate-Lifting Mechanisms, Spokane River, approximately 0.5 mile northeast of intersection of Spokane Falls Boulevard & Post Street, Spokane, Spokane County, WA

An Analysis of Thrust Normalization of Ground Flowfield Pressures, Temperatures, and Velocities, for an AV-8B -408 Harrier During Hover

NASA Technical Reports Server (NTRS)

Naumowicz, Tim; Hange, Craig; Olson, Lawrence E. (Technical Monitor)

1998-01-01

An external environment test for an AV-8B Harrier during hover and vertical operations was conducted at NAWCAD at Patuxent River, Maryland in July 1997. Four boundary layer rakes were instrumented with static and total pressures, and thermocouples for measuring temperatures. These rakes were installed at 30, 50, 75, and 100 foot from the hover center. The 50 ft and 100 ft rakes were offset 20 deg from the other two to minimize interference effects. In order to measure a complete flowfield footprint, it was necessary to have the Harrier change its heading relative to the rakes from 0 to 180 deg. A 20 deg increment in azimuth was used. This permitted the four rakes to measure the flowfield at 72 locations relative to the aircraft. However, as the Harrier burns fuel, the hover thrust must be reduced by the pilot in order to maintain a constant height above ground. The typical test procedure employed was: (1) vertical takeoff at an initial heading; (2) 20 second hover dwell at that heading; (3) pedal turn to a second heading, followed by a 20 second dwell hover; (4) pedal turn to a third heading, followed by a 20 second dwell hover; and (5) vertical landing at the third heading. Additional information is contained in the original extended abstract.

Mapping Shear Zones, Faults, and Crustal Deformation Fabric With Receiver Functions

NASA Astrophysics Data System (ADS)

Schulte-Pelkum, V.; Mahan, K. H.

2014-12-01

Dipping faults, shear zones, and pervasive anisotropic crustal fabric due to deformation are all capable of generating strong near-station mode conversions of teleseismic body waves, even for weak (a few percent) velocity anisotropy. These conversions can be found using the receiver function technique. Dipping foliation and dipping isotropic velocity contrasts can occur in isolation or together in deformed crust. Both generate receiver function arrivals that have a characteristic periodicity with azimuth. Different fixed azimuthal phase shifts between radial and tangential component receiver functions distinguish dipping or tilted structure and fabric from horizontal axis anisotropy. We demonstrate a method that uses these characteristics to map geologically relevant information such as strike and depth of foliation of dipping isotropic velocity contrasts and of horizontal symmetry axis anisotropy contrasts. The method uses waveforms without matching them via forward modeling, which makes choices such as slow versus fast axis symmetry and isotropic dip versus anisotropic axis tilt unnecessary. It also does not use shear wave splitting of the converted waves, which is more difficult to isolate. We show results from the continental U.S. and Canada and from the collision zones in the Himalaya and Tibetan Plateau and Taiwan. We discuss interpretation of our results in the light of recent laboratory measurements of deformed crustal rocks and contributions to the seismic signal from individual minerals such as micas, amphiboles, and quartz. Our observations are connected to geological ground truth by using structural maps and sample anisotropy determined using electron backscatter diffraction from exhumed deep crust in the Athabasca granulite province to predict the seismic signal from present-day deep crust. We also discuss the reconciliation of measurements from anisotropic receiver functions, surface waves, and split shear waves.

9 CFR 3.75 - Housing facilities, general.

Code of Federal Regulations, 2011 CFR

2011-01-01

.... Hard surfaces with which nonhuman primates come in contact must be spot-cleaned daily and sanitized in... must be raked or spot-cleaned with sufficient frequency to ensure all animals the freedom to avoid contact with excreta. Contaminated material must be removed or replaced whenever raking and spot cleaning...

9 CFR 3.75 - Housing facilities, general.

Code of Federal Regulations, 2014 CFR

2014-01-01

.... Hard surfaces with which nonhuman primates come in contact must be spot-cleaned daily and sanitized in... must be raked or spot-cleaned with sufficient frequency to ensure all animals the freedom to avoid contact with excreta. Contaminated material must be removed or replaced whenever raking and spot cleaning...

9 CFR 3.75 - Housing facilities, general.

Code of Federal Regulations, 2012 CFR

2012-01-01

... nonhuman primates come in contact must be spot-cleaned daily and sanitized in accordance with § 3.84 of... bedding, sand, gravel, grass, or other similar material, and planted enclosures must be raked or spot.... Contaminated material must be removed or replaced whenever raking and spot cleaning does not eliminate odors...

9 CFR 3.75 - Housing facilities, general.

Code of Federal Regulations, 2013 CFR

2013-01-01

.... Hard surfaces with which nonhuman primates come in contact must be spot-cleaned daily and sanitized in... must be raked or spot-cleaned with sufficient frequency to ensure all animals the freedom to avoid contact with excreta. Contaminated material must be removed or replaced whenever raking and spot cleaning...

Asphalt Raking. Instructor Manual. Trainee Manual.

ERIC Educational Resources Information Center

Laborers-AGC Education and Training Fund, Pomfret Center, CT.

This packet consists of the instructor and trainee manuals for an asphalt raking course. The instructor manual contains a course schedule for 4 days of instruction, content outline, and instructor outline. The trainee manual is divided into five sections: safety, asphalt basics, placing methods, repair and patching, and clean-up and maintenance.…

An integrated geophysical and hydraulic investigation to characterize a fractured-rock aquifer, Norwalk, Connecticut

USGS Publications Warehouse

Lane, J.W.; Williams, J.H.; Johnson, C.D.; Savino, D.M.; Haeni, F.P.

2002-01-01

The U.S. Geological Survey conducted an integrated geophysical and hydraulic investigation at the Norden Systems, Inc. site in Norwalk, Connecticut, where chlorinated solvents have contaminated a fractured-rock aquifer. Borehole, borehole-to-borehole, surface-geophysical, and hydraulic methods were used to characterize the site bedrock lithology and structure, fractures, and transmissive zone hydraulic properties. The geophysical and hydraulic methods included conventional logs, borehole imagery, borehole radar, flowmeter under ambient and stressed hydraulic conditions, and azimuthal square-array direct-current resistivity soundings. Integrated interpretation of geophysical logs at borehole and borehole-to-borehole scales indicates that the bedrock foliation strikes northwest and dips northeast, and strikes north-northeast to northeast and dips both southeast and northwest. Although steeply dipping fractures that cross-cut foliation are observed, most fractures are parallel or sub-parallel to foliation. Steeply dipping reflectors observed in the radar reflection data from three boreholes near the main building delineate a north-northeast trending feature interpreted as a fracture zone. Results of radar tomography conducted close to a suspected contaminant source area indicate that a zone of low electromagnetic (EM) velocity and high EM attenuation is present above 50 ft in depth - the region containing the highest density of fractures. Flowmeter logging was used to estimate hydraulic properties in the boreholes. Thirty-three transmissive fracture zones were identified in 11 of the boreholes. The vertical separation between transmissive zones typically is 10 to 20 ft. Open-hole and discrete-zone transmissivity was estimated from heat-pulse flowmeter data acquired under ambient and stressed conditions. The open-hole transmissivity ranges from 2 to 86 ft2/d. The estimated transmissivity of individual transmissive zones ranges from 0.4 to 68 ft2/d. Drawdown monitoring in nearby boreholes under pumping conditions identified hydraulic connections along a northeast-southwest trend between boreholes as far as 560 ft apart. The vertical distribution of fractures can be described by power law functions, which suggest that the fracture network contains transmissive zones consisting of closely spaced fractures surrounded by a less fractured and much less permeable rock mass.

Strike-slip Fault Structure in the Salton Trough and Deformation During and After the 2010 M7.2 El Mayor-Cucapah Earthquake from Geodetic and Seismic Data

NASA Astrophysics Data System (ADS)

Fielding, E. J.; Sun, J.; Gonzalez-Ortega, A.; González-Escobar, M.; Freed, A. M.; Burgmann, R.; Samsonov, S. V.; Gonzalez-Garcia, J.; Fletcher, J. M.; Hinojosa, A.

2013-12-01

The Pacific-North America plate boundary character changes southward from the strike-slip and transpressional configuration along most of California to oblique rifting in the Gulf of California, with a transitional zone of transtension beneath the Salton Trough in southernmost California and northern Mexico. The Salton Trough is characterized by extremely high heat flow and thin lithosphere with a thick fill of sedimentary material delivered by the Colorado River during the past 5-6 million years. Because of the rapid sedimentation, most of the faults in Salton Trough are buried and reveal themselves when they slip either seismically or aseismically. They can also be located by refraction and reflection of seismic waves. The 4 April 2010 El Mayor-Cucapah earthquake (Mw 7.2) in Baja California and Sonora, Mexico is probably the largest earthquake in the Salton Trough for at least 120 years, and had primarily right-lateral strike-slip motion. The earthquake ruptured a complex set of faults that lie to the west of the main plate boundary fault, the Cerro Prieto Fault, and shows that the strike-slip fault system in the southern Salton Trough has multiple sub-parallel active faults, similar to southern California. The Cerro Prieto Fault is still likely absorbing the majority of strain in the plate boundary. We study the coseismic and postseismic deformation of the 2010 earthquake with interferometric analysis of synthetic aperture radar (SAR) images (InSAR) and pixel tracking by subpixel correlation of SAR and optical images. We combine sampled InSAR and subpixel correlation results with GPS (Global Positioning System) offsets at PBO (Plate Boundary Observatory) stations to estimate the likely subsurface geometry of the major faults that slipped during the earthquake and to derive a static coseismic slip model. We constrained the surface locations of the fault segments to mapped locations in the Sierra Cucapah to the northwest of the epicenter. SAR along-track offsets, especially on ALOS images, show that there is a large amount of right-lateral slip (1-3 m) on a previously unmapped system of faults extending about 60 km to the southeast of the epicenter beneath the Colorado River Delta named the Indiviso Fault system. The finite fault slip modeling shows a bilateral rupture with coseismic fault slip shallower than 10 km on the faults to the NW (dipping NE) and SE (dipping SW) of the epicenter. The southeastern end of the coseismic ruptures has complex fault geometry, including both east- and west-dipping faults revealed by recently reprocessed seismic reflection profiles. This new coseismic fault geometry will be the basis for a new finite element model of the crust and mantle for modeling of the coseismic slip with realistic 3D elastic structure and the viscoelastic postseismic relaxation. Postseismic InSAR, including new Uninhabited Aerial Vehicle SAR (UAVSAR) data, and GPS show rapid shallow afterslip on faults at the north and south ends of the main coseismic rupture and down-dip from the area of largest coseismic slip. Longer wavelength postseismic relaxation will be best measured by GPS.

Seismological analyses of the 2010 March 11, Pichilemu, Chile Mw 7.0 and Mw 6.9 coastal intraplate earthquakes

USGS Publications Warehouse

Ruiz, Javier A.; Hayes, Gavin P.; Carrizo, Daniel; Kanamori, Hiroo; Socquet, Anne; Comte, Diana

2014-01-01

On 2010 March 11, a sequence of large, shallow continental crust earthquakes shook central Chile. Two normal faulting events with magnitudes around Mw 7.0 and Mw 6.9 occurred just 15 min apart, located near the town of Pichilemu. These kinds of large intraplate, inland crustal earthquakes are rare above the Chilean subduction zone, and it is important to better understand their relationship with the 2010 February 27, Mw 8.8, Maule earthquake, which ruptured the adjacent megathrust plate boundary. We present a broad seismological analysis of these earthquakes by using both teleseismic and regional data. We compute seismic moment tensors for both events via a W-phase inversion, and test sensitivities to various inversion parameters in order to assess the stability of the solutions. The first event, at 14 hr 39 min GMT, is well constrained, displaying a fault plane with strike of N145°E, and a preferred dip angle of 55°SW, consistent with the trend of aftershock locations and other published results. Teleseismic finite-fault inversions for this event show a large slip zone along the southern part of the fault, correlating well with the reported spatial density of aftershocks. The second earthquake (14 hr 55 min GMT) appears to have ruptured a fault branching southward from the previous ruptured fault, within the hanging wall of the first event. Modelling seismograms at regional to teleseismic distances (Δ > 10°) is quite challenging because the observed seismic wave fields of both events overlap, increasing apparent complexity for the second earthquake. We perform both point- and extended-source inversions at regional and teleseismic distances, assessing model sensitivities resulting from variations in fault orientation, dimension, and hypocentre location. Results show that the focal mechanism for the second event features a steeper dip angle and a strike rotated slightly clockwise with respect to the previous event. This kind of geological fault configuration, with secondary rupture in the hanging wall of a large normal fault, is commonly observed in extensional geological regimes. We propose that both earthquakes form part of a typical normal fault diverging splay, where the secondary fault connects to the main fault at depth. To ascertain more information on the spatial and temporal details of slip for both events, we gathered near-fault seismological and geodetic data. Through forward modelling of near-fault synthetic seismograms we build a kinematic k−2 earthquake source model with spatially distributed slip on the fault that, to first-order, explains both coseismic static displacement GPS vectors and short-period seismometer observations at the closest sites. As expected, the results for the first event agree with the focal mechanism derived from teleseismic modelling, with a magnitude Mw 6.97. Similarly, near-fault modelling for the second event suggests rupture along a normal fault, Mw 6.90, characterized by a steeper dip angle (dip = 74°) and a strike clockwise rotated (strike = 155°) with respect to the previous event.

Map of normal faults and extensional folds in the Tendoy Mountains and Beaverhead Range, Southwest Montana and eastern Idaho

USGS Publications Warehouse

Janecke, S.U.; Blankenau, J.J.; VanDenburg, C.J.; VanGosen, B.S.

2001-01-01

Compilation of a 1:100,000-scale map of normal faults and extensional folds in southwest Montana and adjacent Idaho reveals a complex history of normal faulting that spanned at least the last 50 m.y. and involved six or more generations of normal faults. The map is based on both published and unpublished mapping and shows normal faults and extensional folds between the valley of the Red Rock River of southwest Montana and the Lemhi and Birch Creek valleys of eastern Idaho between latitudes 45°05' N. and 44°15' N. in the Tendoy and Beaverhead Mountains. Some of the unpublished mapping has been compiled in Lonn and others (2000). Many traces of the normal faults parallel the generally northwest to north-northwest structural grain of the preexisting Sevier fold and thrust belt and dip west-southwest, but northeastand east-striking normal faults are also prominent. Northeaststriking normal faults are subparallel to the traces of southeast-directed thrusts that shortened the foreland during the Laramide orogeny. It is unlikely that the northeast-striking normal faults reactivated fabrics in the underlying Precambrian basement, as has been documented elsewhere in southwestern Montana (Schmidt and others, 1984), because exposures of basement rocks in the map area exhibit north-northwest- to northwest-striking deformational fabrics (Lowell, 1965; M’Gonigle, 1993, 1994; M’Gonigle and Hait, 1997; M’Gonigle and others, 1991). The largest normal faults in the area are southwest-dipping normal faults that locally reactivate thrust faults (fig. 1). Normal faulting began before middle Eocene Challis volcanism and continues today. The extension direction flipped by about 90° four times.

A transitional volume beneath the Sannio-Irpinia border region (southern Apennines): Different tectonic styles at different depths

NASA Astrophysics Data System (ADS)

De Matteo, Ada; Massa, Bruno; Milano, Girolamo; D'Auria, Luca

2018-01-01

In this paper we investigate the border between the Sannio and Irpinia seismogenic regions, a sector of the southern Apennine chain considered among the most active seismic areas of the Italian peninsula, to shed further light on its complex seismotectonic setting. We integrated recent seismicity with literature data. A detailed analysis of the seismicity that occurred in the 2013-2016 time interval was performed. The events were relocated, after manual re-picking, using different approaches. To retrieve information about the stress field active in the area, inversion of Fault Plane Solutions was also carried out. Hypocentral distribution of the relocated events (ML ≤ 3.5), whose depth is included between 5 and 25 km with the deepest ones located in the NW sector of the study area, shows a different pattern between the northern sector and the southern one. The computed Fault Plane Solutions can be grouped in three depth ranges: < 12 km, dominated by normal dip-slip kinematics; 12-18 km, characterized by normal dip-slip and strike-slip kinematics; > 18 km, dominated by strike-slip kinematics. Stress field inversion across the whole area shows that we are dealing with an heterogeneous set of data, apparently governed by distinct stress fields. We built an upper crustal model profile through integration of geological data, well logs and seismic tomographic profiles. Our results suggest the co-existence of different tectonic styles at distinct crustal depths: the upper crust seems to be affected mostly by normal faulting, whereas strike-slip faulting prevails in the intermediate and lower crust. We infer about the existence of a transitional volume, located between 12 and 18 km depth, between the Sannio and Irpinia regions, acting as a vertical transfer zone.

Implementing a C++ Version of the Joint Seismic-Geodetic Algorithm for Finite-Fault Detection and Slip Inversion for Earthquake Early Warning

NASA Astrophysics Data System (ADS)

Smith, D. E.; Felizardo, C.; Minson, S. E.; Boese, M.; Langbein, J. O.; Guillemot, C.; Murray, J. R.

2015-12-01

The earthquake early warning (EEW) systems in California and elsewhere can greatly benefit from algorithms that generate estimates of finite-fault parameters. These estimates could significantly improve real-time shaking calculations and yield important information for immediate disaster response. Minson et al. (2015) determined that combining FinDer's seismic-based algorithm (Böse et al., 2012) with BEFORES' geodetic-based algorithm (Minson et al., 2014) yields a more robust and informative joint solution than using either algorithm alone. FinDer examines the distribution of peak ground accelerations from seismic stations and determines the best finite-fault extent and strike from template matching. BEFORES employs a Bayesian framework to search for the best slip inversion over all possible fault geometries in terms of strike and dip. Using FinDer and BEFORES together generates estimates of finite-fault extent, strike, dip, preferred slip, and magnitude. To yield the quickest, most flexible, and open-source version of the joint algorithm, we translated BEFORES and FinDer from Matlab into C++. We are now developing a C++ Application Protocol Interface for these two algorithms to be connected to the seismic and geodetic data flowing from the EEW system. The interface that is being developed will also enable communication between the two algorithms to generate the joint solution of finite-fault parameters. Once this interface is developed and implemented, the next step will be to run test seismic and geodetic data through the system via the Earthworm module, Tank Player. This will allow us to examine algorithm performance on simulated data and past real events.

Visualization of Green's Function Anomalies for Megathrust Source in Nankai Trough by Reciprocity Method

NASA Astrophysics Data System (ADS)

Petukhin, A.; Miyakoshi, K.; Tsurugi, M.; Kawase, H.; Kamae, K.

2014-12-01

Effect of various areas (asperities or SMGA) in the source of a megathrust subduction zone earthquake on the simulated long-period ground motions is studied. For this case study we employed a source fault model proposed by HERP (2012) for future M9-class event in the Nankai trough. Velocity structure is 3-D JIVSM model developed for long-period ground motion simulations. The target site OSKH02 "Konohana" is located in center of the Osaka basin. Green's functions for large number of sub-sources (>1000) were calculated by FDM using the reciprocity approach. Depths, strike and dip angles of sub-sources are adjusted to the shape of upper boundary of the Philippine Sea plate. The target period range is 4-20sec. Strongly nonuniform distribution of peak amplitudes of Green's functions is observed (see Figure), and two areas have anomalously large amplitudes: (1) a large along-strike elongated area just south of Kii peninsula and (2) a similar area south of Kii peninsula but shifted toward the Nankai trough. Elongation of the first anomaly fits well 10-15km isolines of the depth distribution of the Philippine Sea plate, while target site is located in the direction perpendicular to these isolines. For this reason, preliminarily we suppose that plate shape may have critical effect on the simulated ground motions, via a cumulative effect of sub-source radiation patterns and specific strike and dip angle distributions. Analysis of the time delay of the peak arrivals at OKSH02 demonstrates that Green's functions from the second anomaly, located in shallow part of plate boundary, are mostly composed of surface waves.

Bedrock geologic map of the Hartland and North Hartland quadrangles, Windsor County, Vermont, and Sullivan and Grafton Counties, New Hampshire

USGS Publications Warehouse

Walsh, Gregory J.

2016-08-16

This report consists of sheets 1 and 2 as well as an online geographic information systems database that includes contacts of bedrock geologic units, faults, outcrops, structural geologic information, and photographs. Sheet 2 of this report shows three cross sections, a tectonic map, and two brittle features maps that show measured outcrop-scale strike and dip results with summary stereonets and rose diagrams.

Repair, Evaluation, Maintenance, and Rehabilitation Research Program: Geotechnical Aspects of Rock Erosion in Emergency Spillway Channels. Report 3. Remediation

DTIC Science & Technology

1988-09-01

identified early and treated promptly. The same authors proposed that the rock-mass parameters that govern rippability , when combined with...lithostratigraphic continuity factors, may provide predictive erosion indices from a geotechnical point of view. 16. Rippability is a form of rock-mass...The rock-mass parameters from which a rippability rating (RR) is derived include rock type, hardness, weathering, structure (strike and dip orientation

Structural evidence for slip partitioning and inclined dextral transpression along the SE Sanandaj-Sirjan zone, Iran

NASA Astrophysics Data System (ADS)

Shafiei Bafti, Shahram; Mohajjel, Mohammad

2015-04-01

The structural evolution of the Sanandaj-Sirjan zone is the result of the convergence of the Iranian microcontinent and the Afro-Arabian continent. The study area at Khabr in the SE Sanandaj-Sirjan zone, in the hinterland of the Zagros orogen, consists of Paleozoic, Mesozoic and Cenozoic rocks. In this area, deformation phases were distinguished in different rock units based on structural and stratigraphical evidence, and the deformational events are divided into two stages: (1) a Late Triassic event and (2) a Late Cretaceous to Miocene event. The Late Triassic deformation event caused regional metamorphism in the Paleozoic units. These units are overlain by unmetamorphosed Jurassic clastic sequences. Fabrics and structural evidence confirm that the F1 folding recumbent and refolded folds were synchronous with the metamorphism of the Paleozoic units and terminated in the Early Jurassic. The time table of the orogenic phases shows that this deformation event is related to the Cimmerian orogenic phase. From a geodynamic point of view, the early Cimmerian deformation in the southeastern Iranian margin suggests that the SE Sanandaj-Sirjan zone was an active margin at that time. The early Cimmerian discordance recorded the onset of a contractional component related to the oblique subduction of Neo-Tethys beneath the central Iranian microcontinent. Structures related to the Late Cretaceous to Miocene deformation phase are observed in Jurassic to Oligocene units, which contain moderately inclined and plunging folds. Comparing these folds with domains of deformation generated in models of transpression shows that the folding was caused by a combination of contractional and dip-slip components of movement, eventually resulting in the formation of a thrust system. The Khabr thrust systems consist of five sheets of oblique thrusts, duplex structures and shear zones. The shear zones generally strike E-W and dip moderately N (30°-40°). The occurrence of asymmetric folds with hinges that are either parallel to strike or plunge down dip demonstrates an oblique-slip component in these thrust shear zones. The stretching lineation in the mylonites within the shear zones is defined by the long axes of ellipsoidal grains of quartz, calcite, plagioclase and garnet. In general, stretching lineations trend from N40°W to N80°W with an intermediate (35°) plunge. The geometry of foliation and lineation within these shear zones shows the effect of dip- and oblique-slip shearing. Deformation continued with strike-slip faulting becoming important during the last stages of deformation from the Miocene to the present day. The results of this study demonstrate that the evolution of the SE Sanandaj-Sirjan zone, from Late Triassic to Miocene, is compatible with an inclined dextral transpression along this zone.

Human See, Human Do.

ERIC Educational Resources Information Center

Tomasello, Michael

1997-01-01

A human demonstrator showed human children and captive chimpanzees how to drag food or toys closer using a rakelike tool. One side of the rake was less efficient than the other for dragging. Chimps tried to reproduce results rather than methods while children imitated and used the more efficient rake side. Concludes that imitation leads to…

An application of wake survey rakes to the experimental determination of thrust for a propeller driven aircraft

NASA Technical Reports Server (NTRS)

Hall, K. R.; Miley, S. J.; Tsai, H. J.

1981-01-01

The lack of slipstream static pressure distribution seriously affected the results but recommendations for removing the deficiency are discussed. The wake survey rake is shown to be a valuable tool in aircraft flight testing. Flow characteristics in the wake of the propeller were examined.

2D simulations of orthogonal cutting of CFRP: Effect of tool angles on parameters of cut and chip morphology

NASA Astrophysics Data System (ADS)

Benhassine, Mehdi; Rivière-Lorphèvre, Edouard; Arrazola, Pedro-Jose; Gobin, Pierre; Dumas, David; Madhavan, Vinay; Aizpuru, Ohian; Ducobu, François

2018-05-01

Carbon-fiber reinforced composites (CFRP) are attractive materials for lightweight designs in applications needing good mechanical properties. Machining of such materials can be harder than metals due to their anisotropic behavior. In addition, the combination of the fibers and resin mechanical properties must also include the fiber orientation. In the case of orthogonal cutting, the tool inclination, rake angle or cutting angle usually influence the cutting process but such a detailed investigation is currently lacking in a 2D configuration. To address this issue, a model has been developed with Abaqus Explicit including Hashin damage. This model has been validated with experimental results from the literature. The effects of the tool parameters (rake angle, clearance angle) on the tool cutting forces, CFRP chip morphology and surface damage are herewith studied. It is shown that 90° orientation for the CFRP increases the surface damage. The rake angle has a minimal effect on the cutting forces but modifies the chip formation times. The feed forces are increased with increasing rake angle.

An analytical method on the surface residual stress for the cutting tool orientation

NASA Astrophysics Data System (ADS)

Li, Yueen; Zhao, Jun; Wang, Wei

2010-03-01

The residual stress is measured by choosing 8 kinds orientations on cutting the H13 dies steel on the HSM in the experiment of this paper. The measured data shows on that the residual stress exists periodicity for the different rake angle (β) and side rake angle (θ) parameters, further study find that the cutting tool orientations have closed relationship with the residual stresses, and for the original of the machined residual stress on the surface from the cutting force and the axial force, it can be gained the simply model of tool-workpiece force, using the model it can be deduced the residual stress model, which is feasible to calculate the size of residual stress. And for almost all the measured residual stresses are compressed stress, the compressed stress size and the direction could be confirmed by the input data for the H13 on HSM. As the result, the residual stress model is the key for optimization of rake angle (β) and side rake angle (θ) in theory, using the theory the more cutting mechanism can be expressed.

Basement and cover-rock deformation during Laramide contraction in the northern Madison Range (Montana) and its influence on Cenozoic basin formation

USGS Publications Warehouse

Kellogg, K.S.; Schmidt, C.J.; Young, S.W.

1995-01-01

Two major Laramide fault systems converge in the northwestern Madison Range: the northwest-striking, southwest-vergent Spanish Peaks reverse fault and the north-striking, east-vergent Hilgard thrust system. Analysis of foliation attitudes in basement gneiss north and south of the Spanish Peaks fault indicates that the basement in thrusted blocks of the Hilgard thrust system have been rotated by an amount similar to that of the basement-cover contact. Steeply dipping, north-striking breccia zones enclosing domains of relatively undeformed basement may have permitted domino-style rotation of basement blocks during simple shear between pairs of thrusts. No hydrocarbon discoveries have been made in this unique structural province. However, petroleum exploration here has focused on basement-cored anticlines, both surface and subthrust, related to the two major Laramide fault systems and on the fault-bounded blocks of Tertiary rocks within the post-Laramide extensional basins. -from Authors

Orthogonal cutting of cancellous bone with application to the harvesting of bone autograft.

PubMed

Malak, Sharif F F; Anderson, Iain A

2008-07-01

Autogenous bone graft harvesting results in cell death within the graft and trauma at the donor site. The latter can be mitigated by using minimally invasive tools and techniques, while cell morbidity may be reduced by improving cutter design and cutting parameters. We have performed orthogonal cutting experiments on bovine cancellous bone samples, to gain a basic understanding of the cutting mechanism and to determine design guidelines for tooling. Measurements were performed at cutting speeds from 11.2 to 5000 mm/min, with tool rake angles of 23 degrees, 45 degrees and 60 degrees, and depths of cut in the range of 0.1-3.0 mm. Horizontal and vertical cutting forces were measured, and the chip formation process video recorded. Continuous chip formation was observed for rake angles of 45 degrees and 60 degrees , and depths of cut greater than 0.8 mm. Chip formation for depths of cut greater than 1.0 mm was accompanied by bone marrow extruding out of the free surfaces and away from the rake face. Specific cutting energies decreased with increasing rake angle, increasing depth of cut and increasing cutting speed. Our orthogonal cutting experiments showed that a rake angle of 60 degrees and a depth of cut of 1mm, will avoid excessive fragmentation, keep specific cutting energy low and promote bone marrow extrusion, which may be beneficial for cell survival. We demonstrate how drill bit clearance angle and feed rate can be calculated facilitating a 1mm depth of cut.

Reproductive ecology of American Oystercatchers nesting on shell rakes

USGS Publications Warehouse

Jodice, Patrick G.R.; Thibault, Janet M.; Collins, S.A.; Spinks, Mark D.; Sanders, Felicia J.

2014-01-01

Degradation of nesting habitat for coastal birds has led to the use of nontraditional nesting habitat. The American Oystercatcher (Haematopus palliatus) is listed as a "Species of High Concern'' by the U. S. Shorebird Conservation Plan and is declining in the southern portion of its U. S. breeding range, where ~ 50% of breeding oystercatchers nest on shell substrate instead of beachfront habitat. We measured daily survival rates during incubation and chick rearing in shell rake habitats over five breeding seasons in the Cape Romain region of South Carolina, USA. Of 354 nesting attempts monitored, 16.1% hatched at least one egg. During incubation, daily survival rate was 0.938, corresponding to 22.8% success to hatching (nest success). For broods, daily survival was 0.991, or 74.0% success from hatching to fledging. Productivity in the Cape Romain region is primarily being lost during the incubation phase, when nests are exposed to overwash and predation. Mobile chicks may, however, be able to avoid flood events or predators by relocating to higher or more protected portions of a shell rake. Based on comparative data for American Oystercatchers from elsewhere in their range, it does not appear that shell rakes in the Cape Romain region are inferior breeding habitat. Our data suggest that conservation actions targeting nest and chick loss from flooding and predation have the greatest opportunity to enhance reproductive success in this core breeding area, and that an assessment of the availability, structure, avian use, and protection status of shell rakes is warranted.

Flight Test Results from the Rake Airflow Gage Experiment on the F-15B Airplane

NASA Technical Reports Server (NTRS)

Frederick, Michael A.; Ratnayake, Nalin A.

2010-01-01

The Rake Airflow Gage Experiment involves a flow-field survey rake that was flown on the Propulsion Flight Test Fixture at the NASA Dryden Flight Research Center using the Dryden F-15B research test bed airplane. The objective of this flight test was to ascertain the flow-field angularity, local Mach number profile, total pressure distortion, and dynamic pressure at the aerodynamic interface plane of the Channeled Centerbody Inlet Experiment. This new mixed-compression, supersonic inlet is planned for flight test in the near term. Knowledge of the flow-field characteristics at this location underneath the airplane is essential to flight test planning and computational modeling of the new inlet, and it is also applicable for future propulsion systems research that may use the Propulsion Flight Test Fixture. This report describes the flight test preparation and execution, and the local flowfield properties calculated from pressure measurements of the rake. Data from the two Rake Airflow Gage Experiment research flights demonstrate that the F-15B airplane, flying at a free-stream Mach number of 1.65 and a pressure altitude of 40,000 ft, would achieve the desired local Mach number for the future inlet flight test. Interface plane distortion levels of 2 percent and a local angle of attack of 2 were observed at this condition. Alternative flight conditions for future testing and an exploration of certain anomalous data also are provided.

Flight Test Results from the Rake Airflow Gage Experiment on the F-15B Airplane

NASA Technical Reports Server (NTRS)

Frederick, Michael A.; Ratnayake, Nalin A.

2011-01-01

The Rake Airflow Gage Experiment involves a flow-field survey rake that was flown on the Propulsion Flight Test Fixture at the NASA Dryden Flight Research Center using the Dryden F-15B research test bed airplane. The objective of this flight test was to ascertain the flow-field angularity, local Mach number profile, total pressure distortion, and dynamic pressure at the aerodynamic interface plane of the Channeled Centerbody Inlet Experiment. This new mixed-compression, supersonic inlet is planned for flight test in the near term. Knowledge of the flow-field characteristics at this location underneath the airplane is essential to flight test planning and computational modeling of the new inlet, an< it is also applicable for future propulsion systems research that may use the Propulsion Flight Test Fixture. This report describes the flight test preparation and execution, and the local flow-field properties calculated from pressure measurements of the rake. Data from the two Rake Airflow Gage Experiment research flights demonstrate that the F-15B airplane, flying at a free-stream Mach number of 1.65 and a pressure altitude of 40,000 ft, would achieve the desired local Mach number for the future inlet flight test. Interface plane distortion levels of 2 percent and a local angle of attack of -2 deg were observed at this condition. Alternative flight conditions for future testing and an exploration of certain anomalous data also are provided.

Thermocouple Rakes for Measuring Boundary Layer Flows Extremely Close to Surface

NASA Technical Reports Server (NTRS)

Hwang, Danny P.; Fralick, Gustave C.; Martin, Lisa C.; Blaha, Charles A.

2001-01-01

Of vital interest to aerodynamic researchers is precise knowledge of the flow velocity profile next to the surface. This information is needed for turbulence model development and the calculation of viscous shear force. Though many instruments can determine the flow velocity profile near the surface, none of them can make measurements closer than approximately 0.01 in. from the surface. The thermocouple boundary-layer rake can measure much closer to the surface than conventional instruments can, such as a total pressure boundary layer rake, hot wire, or hot film. By embedding the sensors (thermocouples) in the region where the velocity is equivalent to the velocity ahead of a constant thickness strut, the boundary-layer flow profile can be obtained. The present device fabricated at the NASA Glenn Research Center microsystem clean room has a heater made of platinum and thermocouples made of platinum and gold. Equal numbers of thermocouples are placed both upstream and downstream of the heater, so that the voltage generated by each pair at the same distance from the surface is indicative of the difference in temperature between the upstream and downstream thermocouple locations. This voltage differential is a function of the flow velocity, and like the conventional total pressure rake, it can provide the velocity profile. In order to measure flow extremely close to the surface, the strut is made of fused quartz with extremely low heat conductivity. A large size thermocouple boundary layer rake is shown in the following photo. The latest medium size sensors already provide smooth velocity profiles well into the boundary layer, as close as 0.0025 in. from the surface. This is about 4 times closer to the surface than the previously used total pressure rakes. This device also has the advantage of providing the flow profile of separated flow and also it is possible to measure simultaneous turbulence levels within the boundary layer.

Experimental and numerical study of hydraulic fracture geometry in shale formations with complex geologic conditions

NASA Astrophysics Data System (ADS)

Ma, Xinfang; Zhou, Tong; Zou, Yushi

2017-05-01

Strike-slip fault geostress and dipping laminated structures in Lujiaping shale formation typically result in difficultly predicting hydraulic fracture (HF) geometries. In this study, a novel 3D fracture propagation model based on discrete element method (DEM) is established. A series of simulations is performed to illustrate the influence of vertical stress difference (△σv = σv-σh), fluid viscosity, and injection rate, on HF growth geometry in the dipping layered formation. Results reveal that the fracturing fluid can easily infiltrate the dipping bedding plane (BP) interfaces with low net pressure for △σv = 1 MPa. HF height growth is also restricted. With increased △σv, fracture propagation in the vertical direction is enhanced, and a fracture network is formed by VF and partially opened dipping BPs. However, it is likely to create simple VF for △σv = 20 MPa. Appropriately increasing fracturing fluid viscosity and injection rate is conductive to weakening the containment effect of BPs on HF growth by increasing the fluid net pressure. However, no indication is found on whether a higher fracturing fluid viscosity is better. Higher viscosity can reduce the activation of BPs, so a stimulated reservoir volume is not necessarily increased. All these results can serve as theoretical guidance for the optimization of fracturing treatments in Lujiaping shale formation.

Neotectonic Geomorphology of the Owen Stanley Oblique-slip Fault System, Eastern Papua New Guinea

NASA Astrophysics Data System (ADS)

Watson, L.; Mann, P.; Taylor, F.

2003-12-01

Previous GPS studies have shown that the Australia-Woodlark plate boundary bisects the Papuan Peninsula of Papua New Guinea and that interplate motion along the boundary varies from about 19 mm/yr of orthogonal opening in the area of the western Woodlark spreading center and D'Entrecasteaux Islands, to about 12 mm/yr of highly oblique opening in the central part of the peninsula, to about 10 mm/yr of transpressional motion on the western part of the peninsula. We have compiled a GIS database for the peninsula that includes a digital elevation model, geologic map, LANDSAT and radar imagery, and earthquake focal mechanisms. This combined data set demonstrates the regional importance of the 600-km-long Owen Stanley fault system (OSFS) in accommodating interplate motion and controlling the geomorphology and geologic exposures of the peninsula. The OSFS originated as a NE-dipping, reactivated Oligocene-Early Miocene age ophiolitic suture zone between an Australian continental margin and the Melanesian arc system. Pliocene to recent motion on the plate boundary has reactivated motion on the former NE-dipping thrust fault either as a NE-dipping normal fault in the eastern area or as a more vertical strike-slip fault in the western area. The broadly arcuate shape of the OSFS is probably an inherited feature from the original thrust fault. Faults in the eastern area (east of 148° E) exhibit characteristics expected for normal and oblique slip faults including: discontinuous fault traces bounding an upthrown highland block and a downthrown coastal plain or submarine block, transfer faults parallel to the opening direction, scarps facing to both the northeast and southwest, and spatial association with recent volcanism. Faults in the western area (west of 148° E) exibit characteristics expected for left-lateral strike-slip faults including: linear and continuous fault trace commonly confined to a deep, intermontane valley and sinistral offsets and deflections of rivers and streams by 0.5 to 1.2 km. The northern edge of the OSFS merges with the Ramu-Markham strike-slip fault near Lae. SW tilting of the footwall block (Papuan Peninsula) is responsible for the asymmetrical topographic profile of the peninsula and drowned topography along the southern coast of the peninsula.

10. CLOSEUP VIEW OF THE TRASH RAKES, THEIR LIFTING MECHANISM ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

10. CLOSE-UP VIEW OF THE TRASH RAKES, THEIR LIFTING MECHANISM (RIGHT FOREGROUND), AND CLUTCHES THAT OPEN AND CLOSE THE SIX INTAKE GATES ON THE POST FALLS POWERHOUSE, LOOKING WEST. - Washington Water Power Company Post Falls Power Plant, Middle Channel Powerhouse & Dam, West of intersection of Spokane & Fourth Streets, Post Falls, Kootenai County, ID

A survey of aerobraking orbital transfer vehicle design concepts

NASA Technical Reports Server (NTRS)

Park, Chul

1987-01-01

The five existing design concepts of the aerobraking orbital transfer vehicle (namely, the raked sphere-cone designs, conical lifting-brake, raked elliptic-cone, lifting-body, and ballute) are reviewed and critiqued. Historical backgrounds, and the geometrical, aerothermal, and operational features of these designs are reviewed first. Then, the technological requirements for the vehicle (namely, navigation, aerodynamic stability and control, afterbody flow impingement, nonequilibrium radiation, convective heat-transfer rates, mission abort and multiple atmospheric passes, transportation and construction, and the payload-to-vehicle weight requirements) are delineated by summarizing the recent advancements made on these issues. Each of the five designs are critiqued and rated on these issues. The highest and the lowest ratings are given to the raked sphere-cone and the ballute design, respectively.

Comparison of Engine/Inlet Distortion Measurements with MEMS and ESP Pressure Sensors

NASA Technical Reports Server (NTRS)

Soto, Hector L.; Hernandez, Corey D.

2004-01-01

A study of active-flow control in a small-scale boundary layer ingestion inlet was conducted at the NASA Langley Basic Aerodynamic Research Tunnel (BART). Forty MEMS pressure sensors, in a rake style configuration, were used to examine both the mean (DC) and high frequency (AC) components of the total pressure across the inlet/engine interface plane. The mean component was acquired and used to calculate pressure distortion. The AC component was acquired separately, at a high sampling rate, and is used to study the unsteady effects of the active-flow control. An identical total pressure rake, utilizing an Electronically Scanned Pressure (ESP) system, was also used to calculate distortion; a comparison of the results obtained using the two rakes is presented.

Slip and Dilation Tendency Analysis of the Tuscarora Geothermal Area

DOE Data Explorer

Faulds, James E.

2013-12-31

Critically stressed fault segments have a relatively high likelihood of acting as fluid flow conduits (Sibson, 1994). As such, the tendency of a fault segment to slip (slip tendency; Ts; Morris et al., 1996) or to dilate (dilation tendency; Td; Ferrill et al., 1999) provides an indication of which faults or fault segments within a geothermal system are critically stressed and therefore likely to transmit geothermal fluids. The slip tendency of a surface is defined by the ratio of shear stress to normal stress on that surface: Ts = τ / σn (Morris et al., 1996). Dilation tendency is defined by the stress acting normal to a given surface: Td = (σ1-σn) / (σ1-σ3) (Ferrill et al., 1999). Slip and dilation were calculated using 3DStress (Southwest Research Institute). Slip and dilation tendency are both unitless ratios of the resolved stresses applied to the fault plane by ambient stress conditions. Values range from a maximum of 1, a fault plane ideally oriented to slip or dilate under ambient stress conditions to zero, a fault plane with no potential to slip or dilate. Slip and dilation tendency values were calculated for each fault in the focus study areas at, McGinness Hills, Neal Hot Springs, Patua, Salt Wells, San Emidio, and Tuscarora on fault traces. As dip is not well constrained or unknown for many faults mapped in within these we made these calculations using the dip for each fault that would yield the maximum slip tendency or dilation tendency. As such, these results should be viewed as maximum tendency of each fault to slip or dilate. The resulting along-fault and fault-to-fault variation in slip or dilation potential is a proxy for along fault and fault-to-fault variation in fluid flow conduit potential. Stress Magnitudes and directions Stress field variation within each focus area was approximated based on regional published data and the world stress database (Hickman et al., 2000; Hickman et al., 1998 Robertson-Tait et al., 2004; Hickman and Davatzes, 2010; Davatzes and Hickman, 2006; Blake and Davatzes 2011; Blake and Davatzes, 2012; Moeck et al., 2010; Moos and Ronne, 2010 and Reinecker et al., 2005) as well as local stress information if applicable. For faults within these focus systems we applied either a normal faulting stress regime where the vertical stress (sv) is larger than the maximum horizontal stress (shmax) which is larger than the minimum horizontal stress (sv>shmax>shmin) or strike-slip faulting stress regime where the maximum horizontal stress (shmax) is larger than the vertical stress (sv) which is larger than the minimum horizontal stress (shmax >sv>shmin) depending on the general tectonic province of the system. Based on visual inspection of the limited stress magnitude data in the Great Basin we used magnitudes such that shmin/shmax = .527 and shmin/sv= .46, which are consistent with complete and partial stress field determinations from Desert Peak, Coso, the Fallon area and Dixie valley (Hickman et al., 2000; Hickman et al., 1998 Robertson-Tait et al., 2004; Hickman and Davatzes, 2011; Davatzes and Hickman, 2006; Blake and Davatzes 2011; Blake and Davatzes, 2012). Slip and dilation tendency for the Tuscarora geothermal field was calculated based on the faults mapped Tuscarora area (Dering, 2013). The Tuscarora area lies in the Basin and Range Province, as such we applied a normal faulting stress regime to the Tuscarora area faults, with a minimum horizontal stress direction oriented 115, based on inspection of local and regional stress determinations, as explained above. Under these stress conditions north-northeast striking, steeply dipping fault segments have the highest dilation tendency, while north-northeast striking 60° dipping fault segments have the highest tendency to slip. Tuscarora is defined by a left-step in a major north- to-north northeast striking, west-dipping range-bounding normal fault system. Faults within the broad step define an anticlinal accommodation zone...

Using Deep Slow Slip in New Zealand to Constrain Slip Partitioning

NASA Astrophysics Data System (ADS)

Bartlow, N. M.; Wallace, L. M.

2016-12-01

Underneath New Zealand's North Island, the Pacific plate subducts obliquely beneath the Australian plate. Just to the south, subduction ceases and the plate boundary transitions to the mainly strike-slip, steeply dipping Alpine fault that runs along the South Island. In the region of the southern North Island, the relative plate motion has significant components of both convergence and along strike motion, and slip is partitioned between the main Hikurangi subduction interface and a series of shallower strike-slip faults running thurough the North Island (Wallace and Beavan, GRL, 2010). This region also hosts deep ( 50 km), long duration ( 1 year) slow slip events (SSEs). From early 2013 to early 2016, continuous GPS stations maintained by GeoNet in this region recorded two such deep SSEs on the Hikurangi megathrust. The first SSE occurred on the Kapiti patch, just southwest of the North Island coast. SSEs previous occurred here in 2003 and 2008 (Wallace and Beavan, JGR, 2010). The 2014 Kapiti SSE is unique because it was rapidly decelerated following increased normal stress (clamping) caused by a nearby M 6.3 earthquake (Wallace et al., GRL, 2014). However, GPS data indicates that slip did not stop entirely, and soon after the Manawatu slow slip patch just to the northeast ruptured in another SSE. This patch previously had large SSEs in 2004/2005 and 2010/2011. Given the previous repeat interval of 5.5 years, the 2014/2015 Manawatu SSE is early; however, the record is very short. Here we show Network Inversion Filter derived models of slow slip for the various phases of the Kapiti and Manawatu SSEs, which indicate a possible continuous migration of slip from the Kapiti SSE patch to the Manawatu SSE patch, and we quantify the shear stress increase on the Manawatu patch after the Kapiti SSE. Additionally, we explore allowing the Network Inversion Filter to vary the direction of slip on the plate interface to better fit the data. We estimate how much of the strike-slip and dip-slip components of the relative plate motion are being accommodated by the main thrust interface, and infer how much slip is being accommodated by the strike-slip faults and forearc rotation. We compare our results to those from prior block models of inter-SSE data (Wallace et al., G3, 2009) and explore the implications for seismic hazard assessment in this region.

Structural Evolution of Martin Crater Thaumasia Planum, Mars

NASA Astrophysics Data System (ADS)

Dolan, Daniel J.

A detailed structural map of the central uplift of Martin Crater in western Thaumasia Planum, Mars, reveals highly folded and fractured geology throughout the 15-km diameter uplift. The stratigraphy in the central uplift of the crater has been rotated to near vertical dip and imaged by high-definition cameras aboard the Mars Reconnaissance Orbiter (MRO). These unique factors allow individual geologic beds in Martin Crater to be studied and located across the length of the uplift. Bedding in Martin Crater primarily strikes SSE-NNW and dips near vertically. Many units are separated by a highly complex series of linear faults, creating megablocks of uplifted material. Faulting is dominantly left-slip in surface expression and strikes SW-NE, roughly perpendicular to bedding, and major fold axes plunge toward the SW. Coupled with infrared imagery of the ejecta blanket, which shows an "exclusion zone" northeast of the crater, these structural indicators provide strong support for a low-angle impactor (approximately 10-20°) originating from the northeast. Acoustic fluidization is the prevailing theoretical model put forth to explain complex crater uplift. The theory predicts that uplifted megablocks in craters are small, discrete, separated and highly randomized in orientation. However, megablocks in Martin Crater are tightly interlocked and often continuous in lithology across several kilometers. Thus, the model of acoustic fluidization, as it is currently formulated, does not appear to be supported by the structural evidence found in Martin Crater.

Distribution of resistive and conductive structures in Nankai accretionary wedge reveals contrasting stress paths

NASA Astrophysics Data System (ADS)

Conin, Marianne; Bourlange, Sylvain; Henry, Pierre; Boiselet, Aurelien; Gaillot, Philippe

2014-01-01

In this article, we study the characteristics and spatial distribution of the deformation structures along the Kumano transect of the Nankai accretionary wedge, and use this information to interpret the stress path followed by the sediments. Deformation structures are identified from logging while drilling (LWD) resistivity images of the materials surrounding the drill hole and from 3-dimensional X-ray CT-images of cores acquired during the IODP NanTroSEIZE project. The relative resistivity of the structures identified on logs and the strike, dip, and density of structures identified on CT scan images are measured. The analysis of dip and strike of structures indicates that most of the resistive structures identified on logging data correspond to compactive shear bands. Results also indicate that conductive structures predominate at the toe of the prism and above the main out of sequence thrust, in locations where past and recent erosion occurred. We propose several mechanisms that could explain the relation between erosion and the absence of compactive shear bands. We conclude that sediments followed different stress paths depending on their location within the wedge, and that those differences explain the distribution of deformation structures within the wedge. We also show the coexistence of dilatant and compactant structures in fault zones including the frontal thrust and mega splay fault, and we interpret the coexistence of these structures as a possible consequence of a transient fluid pressure.

Source parameters for the 1952 Kern County earthquake, California: A joint inversion of leveling and triangulation observations

USGS Publications Warehouse

Bawden, G.W.

2001-01-01

Coseismic leveling and triangulation observations are used to determine the faulting geometry and slip distribution of the July 21, 1952, Mw 7.3 Kem County earthquake on the White Wolf fault. A singular value decomposition inversion is used to assess the ability of the geodetic network to resolve slip along a multisegment fault and shows that the network is sufficient to resolve slip along the surface rupture to a depth of 10 km. Below 10 km, the network can only resolve dip slip near the fault ends. The preferred source model is a two-segment right-stepping fault with a strike of 51?? and a dip of 75?? SW. The epicentral patch has deep (6-27 km) leftlateral oblique slip, while the northeastern patch has shallow (1-12.5 km) reverse slip. There is nearly uniform reverse slip (epicentral, 1.6 m; northeast, 1.9 m), with 3.6 m of left-lateral strike slip limited to the epicentral patch. The seismic moment is M0= 9.2 ?? 0.5 ?? 1019 N m (Mw= 7.2). The signal-to-noise ratio of the leveling and triangulation data is reduced by 96% and 49%, respectively. The slip distribution from the preferred model matches regional geomorphic features and may provide a driving mechanism for regional shortening across the Comanche thrust and structural continuity with the Scodie seismic lineament to the northeast.

Strain accumulation and rotation in the Eastern California Shear Zone

USGS Publications Warehouse

Savage, J.C.; Gan, Weijun; Svarc, J.L.

2001-01-01

Although the Eastern California Shear Zone (ECSZ) (strike ???N25??W) does not quite coincide with a small circle drawn about the Pacific-North America pole of rotation, trilateration and GPS measurements demonstrate that the motion within the zone corresponds to right-lateral simple shear across a vertical plane (strike N33??W??5??) roughly parallel to the tangent to that local small circle (strike ???N40??W). If the simple shear is released by slip on faults subparallel to the shear zone, the accumulated rotation is also released, leaving no secular rotation. South of the Garlock fault the principal faults (e.g., Calico-Blackwater fault) strike ???N40??W, close enough to the strike of the vertical plane across which maximum right-lateral shear accumulates to almost wholly accommodate that accumulation of both strain and rotation by right-lateral slip. North of the Garlock fault dip slip as well as strike slip on the principal faults (strike ???N20??W) is required to accommodate the simple shear accumulation. In both cases the accumulated rotation is released with the shear strain. The Garlock fault, which transects the ECSZ, is not offset by north-northwest striking faults nor, despite geological evidence for long-term left-lateral slip, does it appear at the present time to be accumulating left-lateral simple shear strain across the fault due to slip at depth. Rather the motion is explained by right-lateral simple shear across the orthogonal ECSZ. Left-lateral slip on the Garlock fault will release the shear strain accumulating there but would augment the accumulating rotation, resulting in a secular clockwise rotation rate ???80 nrad yr-1 (4.6?? Myr-1).

Paleomagnetic and structural evidence for oblique slip in a fault-related fold, Grayback monocline, Colorado

USGS Publications Warehouse

Tetreault, J.; Jones, C.H.; Erslev, E.; Larson, S.; Hudson, M.; Holdaway, S.

2008-01-01

Significant fold-axis-parallel slip is accommodated in the folded strata of the Grayback monocline, northeastern Front Range, Colorado, without visible large strike-slip displacement on the fold surface. In many cases, oblique-slip deformation is partitioned; fold-axis-normal slip is accommodated within folds, and fold-axis-parallel slip is resolved onto adjacent strike-slip faults. Unlike partitioning strike-parallel slip onto adjacent strike-slip faults, fold-axis-parallel slip has deformed the forelimb of the Grayback monocline. Mean compressive paleostress orientations in the forelimb are deflected 15??-37?? clockwise from the regional paleostress orientation of the northeastern Front Range. Paleomagnetic directions from the Permian Ingleside Formation in the forelimb are rotated 16??-42?? clockwise about a bedding-normal axis relative to the North American Permian reference direction. The paleostress and paleomagnetic rotations increase with the bedding dip angle and decrease along strike toward the fold tip. These measurements allow for 50-120 m of fold-axis-parallel slip within the forelimb, depending on the kinematics of strike-slip shear. This resolved horizontal slip is nearly equal in magnitude to the ???180 m vertical throw across the fold. For 200 m of oblique-slip displacement (120 m of strike slip and 180 m of reverse slip), the true shortening direction across the fold is N90??E, indistinguishable from the regionally inferred direction of N90??E and quite different from the S53??E fold-normal direction. Recognition of this deformational style means that significant amounts of strike slip can be accommodated within folds without axis-parallel surficial faulting. ?? 2008 Geological Society of America.

Intensive straw harvesting, fertilization, and fertilizer source affect nitrogen mineralization and soil labile carbon of a loblolly pine plantation

Treesearch

K. Ellum; H.O. Liechty; M.A. Blazier

2013-01-01

Straw harvesting can supplement traditional revenues generated by loblolly pine (Pinus taeda L.) plantation management. However, repeated raking may alter soil properties and nutrition. In northcentral Louisiana, a study was conducted to evaluate the long-term effects of intensive straw raking and fertilizer source (inorganic or organic) on nitrogen...

Evaluation of Federal Aviation Administration Engine Exhaust Sampling Rake.

DTIC Science & Technology

1977-06-01

Engine exit total pressure - Pt7 " High turbine discharge temperature - Tt65,6 . Engine exit total temperature - Tt7 - Burner pressure - Ps4 0 Total...illustrated by Figure 22, a plot of Ps4 /Pt7 (expansion thru the turbine) vs. EPR (Pt7/Pt2). This plot indicates that the ECCP rake has no measurable effect on

67. September 1913 "No. 103. Oil being applied and raked ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

67. September 1913 "No. 103. Oil being applied and raked in, oil treated earth surface, experimental section. The frame in foreground was 1 x 5 yards, each square yard being indicated thereon, by which it was possible to determine the amount of oil placed in each square yard." - Crater Lake National Park Roads, Klamath Falls, Klamath County, OR

Design and Calibration of a Flowfield Survey Rake for Inlet Flight Research

NASA Technical Reports Server (NTRS)

Flynn, Darin C.; Ratnayake, Nalin A.; Frederick, Michael

2009-01-01

The Propulsion Flight Test Fixture at the NASA Dryden Flight Research Center is a unique test platform available for use on NASA's F-15B aircraft, tail number 836, as a modular host for a variety of aerodynamics and propulsion research. For future flight data from this platform to be valid, more information must be gathered concerning the quality of the airflow underneath the body of the F-15B at various flight conditions, especially supersonic conditions. The flow angularity and Mach number must be known at multiple locations on any test article interface plane for measurement data at these locations to be valid. To determine this prerequisite information, flight data will be gathered in the Rake Airflow Gauge Experiment using a custom-designed flowfield rake to probe the airflow underneath the F-15B at the desired flight conditions. This paper addresses the design considerations of the rake and probe assembly, including the loads and stress analysis using analytical methods, computational fluid dynamics, and finite element analysis. It also details the flow calibration procedure, including the completed wind-tunnel test and posttest data reduction, calibration verification, and preparation for flight-testing.

Cone-Probe Rake Design and Calibration for Supersonic Wind Tunnel Models

NASA Technical Reports Server (NTRS)

Won, Mark J.

1999-01-01

A series of experimental investigations were conducted at the NASA Langley Unitary Plan Wind Tunnel (UPWT) to calibrate cone-probe rakes designed to measure the flow field on 1-2% scale, high-speed wind tunnel models from Mach 2.15 to 2.4. The rakes were developed from a previous design that exhibited unfavorable measurement characteristics caused by a high probe spatial density and flow blockage from the rake body. Calibration parameters included Mach number, total pressure recovery, and flow angularity. Reference conditions were determined from a localized UPWT test section flow survey using a 10deg supersonic wedge probe. Test section Mach number and total pressure were determined using a novel iterative technique that accounted for boundary layer effects on the wedge surface. Cone-probe measurements were correlated to the surveyed flow conditions using analytical functions and recursive algorithms that resolved Mach number, pressure recovery, and flow angle to within +/-0.01, +/-1% and +/-0.1deg , respectively, for angles of attack and sideslip between +/-8deg. Uncertainty estimates indicated the overall cone-probe calibration accuracy was strongly influenced by the propagation of measurement error into the calculated results.

Multiple Access Interference Reduction Using Received Response Code Sequence for DS-CDMA UWB System

NASA Astrophysics Data System (ADS)

Toh, Keat Beng; Tachikawa, Shin'ichi

This paper proposes a combination of novel Received Response (RR) sequence at the transmitter and a Matched Filter-RAKE (MF-RAKE) combining scheme receiver system for the Direct Sequence-Code Division Multiple Access Ultra Wideband (DS-CDMA UWB) multipath channel model. This paper also demonstrates the effectiveness of the RR sequence in Multiple Access Interference (MAI) reduction for the DS-CDMA UWB system. It suggests that by using conventional binary code sequence such as the M sequence or the Gold sequence, there is a possibility of generating extra MAI in the UWB system. Therefore, it is quite difficult to collect the energy efficiently although the RAKE reception method is applied at the receiver. The main purpose of the proposed system is to overcome the performance degradation for UWB transmission due to the occurrence of MAI during multiple accessing in the DS-CDMA UWB system. The proposed system improves the system performance by improving the RAKE reception performance using the RR sequence which can reduce the MAI effect significantly. Simulation results verify that significant improvement can be obtained by the proposed system in the UWB multipath channel models.

South Virgin-White Hills detachment fault system of SE Nevada and NW Arizona: Applying apatite fission track thermochronology to constrain the tectonic evolution of a major continental detachment fault

NASA Astrophysics Data System (ADS)

Fitzgerald, Paul G.; Duebendorfer, Ernest M.; Faulds, James E.; O'Sullivan, Paul

2009-04-01

The South Virgin-White Hills detachment (SVWHD) in the central Basin and Range province with an along-strike extent of ˜60 km is a major continental detachment fault system. Displacement on the SVWHD decreases north to south from ˜17 to <6 km. This is accompanied by a change in fault and footwall rock type from mylonite overprinted by cataclasite to chlorite cataclasite and then fault breccia reflecting decreasing fault displacement and footwall exhumation. Apatite fission track (AFT) thermochronology was applied both along-strike and across-strike to assess this displacement gradient. The overall thermal history reflects Laramide cooling (˜75 Ma) and then rapid cooling beginning in the late early Miocene. Age patterns reflect some complexity but extension along the SVWHD appears synchronous with rapid cooling initiated at ˜17 Ma due to tectonic exhumation. Slip rate is more rapid (˜8.6 km/Ma) in the north compared to ˜1 km/Ma in the south. The displacement gradient results from penecontemporaneous along-strike motion and formation of the SVWHD by linkage of originally separate fault segments that have differential displacements and hence differential slip rates. East-west transverse structures likely play a role in linkage of different fault segments. The preextension paleogeothermal gradient is well constrained in the Gold Butte block as 18-20°C/km. We present a new thermochronologic approach to constrain fault dip during slip, treating the vertical exhumation rate and the slip as vectors, with the angle between them used to constrain fault dip during slip through the closure temperature of a particular thermochronometer. AFT data from the western rim of the Colorado Plateau constrain the initiation of timing of cooling associated with the Laramide Orogeny at ˜75 Ma, and a reheating event in the late Eocene/early Oligocene associated with burial by sediments ("rim gravels") most likely shed from the Kingman High to the west of the plateau.

Estimating the Reactivation Potential of Pre-Existing Fractures in Subsurface Granitoids from Outcrop Analogues and in-Situ Stress Modeling: Implications for EGS Reservoir Stimulation with an Example from Thuringia (Central Germany)

NASA Astrophysics Data System (ADS)

Kasch, N.; Ustaszewski, K. M.; Siegburg, M.; Navabpour, P.; Hesse, G.

2014-12-01

The Mid-German Crystalline Rise (MGCR) in Thuringia (central Germany) is part of the European Variscan orogen and hosts large extents of Visean granites (c. 350 Ma), locally overlain by up to 3 km of Early Permian to Mid-Triassic volcanic and sedimentary rocks. A geothermal gradient of 36°C km-1 suggests that such subsurface granites form an economically viable hot dry rock reservoir at > 4 km depth. In order to assess the likelihood of reactivating any pre-existing fractures during hydraulic reservoir stimulation, slip and dilation tendency analyses (Morris et al. 1996) were carried out. For this purpose, we determined orientations of pre-existing fractures in 14 granite exposures along the southern border fault of an MGCR basement high. Additionally, the strike of 192 Permian magmatic dikes affecting the granite was considered. This analysis revealed a prevalence of NW-SE-striking fractures (mainly joints, extension veins, dikes and subordinately brittle faults) with a maximum at 030/70 (dip azimuth/dip). Borehole data and earthquake focal mechanisms reveal a maximum horizontal stress SHmax trending N150°E and a strike-slip regime. Effective in-situ stress magnitudes at 4.5 km depth, assuming hydrostatic conditions and frictional equilibrium along pre-existing fractures with a friction coefficient of 0.85 yielded 230 and 110 MPa for SHmax and Shmin, respectively. In this stress field, fractures with the prevailing orientations show a high tendency of becoming reactivated as dextral strike-slip faults if stimulated hydraulically. To ensure that a stimulation well creates fluid connectivity on a reservoir volume as large as possible rather than dissipating fluids along existing fractures, it should follow a trajectory at the highest possible angle to the orientation of prevailing fractures, i.e. subhorizontal and NE-SW-oriented. References: Morris, A., D. A. Ferrill, and D. B. Henderson (1996), Slip-tendency analysis and fault reactivation, Geology, 24, 275-278.

Variable deep structure of a midcontinent fault and fold zone from seismic reflection: La Salle deformation belt, Illinois basin

USGS Publications Warehouse

McBride, J.H.

1997-01-01

Deformation within the United States mid-continent is frequently expressed as quasilinear zones of faulting and folding, such as the La Salle deformation belt, a northwest-trending series of folds cutting through the center of the Illinois basin. Seismic reflection profiles over the southern La Salle deformation belt reveal the three-dimensional structural style of deformation in the lower Paleozoic section and uppermost Precambrian(?) basement. Individual profiles and structural contour maps show for the first time that the folds of the La Salle deformation belt are underlain at depth by reverse faults that disrupt and offset intrabasement structure, offset the top of interpreted Precambrian basement, and accommodate folding of overlying Paleozoic strata. The folds do not represent development of initial dips by strata deposited over a preexisting basement high. Rather, the structures resemble subdued "Laramide-style" forced folds, in that Paleozoic stratal reflectors appear to be flexed over a fault-bounded basement uplift with the basement-cover contact folded concordantly with overlying strata. For about 40 km along strike, the dominant faults reverse their dip direction, alternating between east and west. Less well expressed antithetic or back thrusts appear to be associated with the dominant faults and could together describe a positive flower structure. The overall trend of this part of the La Salle deformation belt is disrupted by along-strike discontinuities that separate distinct fold culminations. Observations of dual vergence and along-strike discontinuities suggest an original deformation regime possibly involving limited transpression associated with distant late Paleozoic Appalachian-Ouachita mountain building. Moderate-magnitude earthquakes located west of the western flank of the La Salle deformation belt have reverse and strike-slip mechanisms at upper trustai depths, which might be reactivating deep basement faults such as observed in this study. The La Salle deformation belt is not necessarily typical of other well-known major midcontinent fault and fold zones, such as the Nemaha ridge, over which Paleozoic and younger sediments appear to simply be draped.

Deformation sequences of the Day Nui Con Voi metamorphic belt, northern Vietnam

NASA Astrophysics Data System (ADS)

Yeh, M. W.; Lee, T. Y.; Lo, C. H.; Chung, S. L.; Lan, C. Y.; Lee, J. C.; Lin, T. S.; Lin, Y. J.

2003-04-01

The correlation of structure, microstructure and metamorphic assemblages is of fundamental importance to the understanding of the complex tectonic history and kinematics of the Day Nui Con Voi (DNCV) metamorphic belt in Vietnam along the Ailao Shan-Red River (ASRR) shear zone as it provides constraints on the relative timing of the deformation, kinematics and metamorphism. High-grade metamorphic rocks of amphibolite faces showed consistent deformation sequences of three folding events followed by one brittle deformation through all four cross sections from Lao Cai to Viet Tri indicated the DNCV belt experienced similar deformation condition throughout its length. The first deformation event, D1, produced up-right folds (locally preserved) with sub-vertical, NE-SW striking axial planes with dextral sense of shear probably formed during the early phase of the lowermost Triassic Indosinian orogeny. Followed by this compressional event is a gravitational collapsing event, D2, which is the major deformation and metamorphic event characterized by kyanite grade metamorphism and large scale horizontal folds with NW-SE (320) striking sub-horizontal axial pane showing sinsistral sense of shear most likely formed during the Oligocene-Miocene SE extrusion of Indochina peninsula. The 3rd folding event, D3, is a post-metamorphism doming event with NW-SE (310) striking sub-vertical axial plane that folded/tilted the once sub-horizontal D2 axial planes into shallowly (<30 degrees) NE dipping on the NE limb, and SW dipping on the SW limb possibly due to left-lateral movement of the N-S trending Xian Shui He fault system in Mid-Miocene. The outward decreasing of the metamorphic grade from kyanite to garnet then biotite indicated the D3 occurred post metamorphism. Reactivation of the sub-horizontal D2 fold axial planes showed dextral sense of shear possibly due to Late Miocene-Pliocene right-lateral movement of the ASRR shear zone. This right lateral movement continuously deformed the DNCV with brittle fractures such as joints and normal faults (D4) striking NE-SW to E-W and NW-SE.

Surface faults on Montague Island associated with the 1964 Alaska earthquake: Chapter G in The Alaska earthquake, March 27, 1964: regional effects

USGS Publications Warehouse

Plafter, George

1967-01-01

Two reverse faults on southwestern Montague Island in Prince William Sound were reactivated during the earthquake of March 27, 1964. New fault scarps, fissures, cracks, and flexures appeared in bedrock and unconsolidated surficial deposits along or near the fault traces. Average strike of the faults is between N. 37° E. and N. 47° E.; they dip northwest at angles ranging from 50° to 85°. The dominant motion was dip slip; the blocks northwest of the reactivated faults were relatively upthrown, and both blocks were upthrown relative to sea level. No other earthquake faults have been found on land. The Patton Bay fault on land is a complex system of en echelon strands marked by a series of spectacular landslides along the scarp and (or) by a zone of fissures and flexures on the upthrown block that locally is as much as 3,000 feet wide. The fault can be traced on land for 22 miles, and it has been mapped on the sea floor to the southwest of Montague Island an additional 17 miles. The maximum measured vertical component of slip is 20 to 23 feet and the maximum indicated dip slip is about 26 feet. A left-lateral strike-slip component of less than 2 feet occurs near the southern end of the fault on land where its strike changes from northeast to north. Indirect evidence from the seismic sea waves and aftershocks associated with the earthquake, and from the distribution of submarine scarps, suggests that the faulting on and near Montague Island occurred at the northeastern end of a reactivated submarine fault system that may extend discontinuously for more than 300 miles from Montague Island to the area offshore of the southeast coast of Kodiak Island. The Hanning Bay fault is a minor rupture only 4 miles long that is marked by an exceptionally well defined almost continuous scarp. The maximum measured vertical component of slip is 16⅓ feet near the midpoint, and the indicated dip slip is about 20 feet. There is a maximum left-lateral strike-slip component of one-half foot near the southern end of the scarp. Warping and extension cracking occurred in bedrock near the midpoint on the upthrown block within about 1,000 feet of the fault scarp. The reverse faults on Montague Island and their postulated submarine extensions lie within a tectonically important narrow zone of crustal attenuation and maximum uplift associated with the earthquake. However, there are no significant lithologic differences in the rock sequences across these faults to suggest that they form major tectonic boundaries. Their spatial distribution relative to the regional uplift associated with the earthquake, the earthquake focal region, and the epicenter of the main shock suggest that they are probably subsidiary features rather than the causative faults along which the earthquake originated. Approximately 70 percent of the new breakage along the Patton Bay and the Hanning Bay faults on Montague Island was along obvious preexisting active fault traces. The estimated ages of undisturbed trees on and near the fault trace indicate that no major disc placement had occurred on these faults for at least 150 to 300 years before the 1964 earthquake.

Low gravity liquid level sensor rake

NASA Technical Reports Server (NTRS)

Grayson, Gary D. (Inventor); Craddock, Jeffrey C. (Inventor)

2003-01-01

The low gravity liquid level sensor rake measures the liquid surface height of propellant in a propellant tank used in launch and spacecraft vehicles. The device reduces the tendency of the liquid propellant to adhere to the sensor elements after the bulk liquid level has dropped below a given sensor element thereby reducing the probability of a false liquid level measurement. The liquid level sensor rake has a mast attached internal to a propellant tank with an end attached adjacent the tank outlet. Multiple sensor elements that have an arm and a sensor attached at a free end thereof are attached to the mast at locations selected for sensing the presence or absence of the liquid. The sensor elements when attached to the mast have a generally horizontal arm and a generally vertical sensor.

A Future Moon Mission: Curatorial Statistics on Regolith Fragments Applicable to Sample Collection by Raking

NASA Technical Reports Server (NTRS)

Allton, J. H.; Bevill, T. J.

2003-01-01

The strategy of raking rock fragments from the lunar regolith as a means of acquiring representative samples has wide support due to science return, spacecraft simplicity (reliability) and economy [3, 4, 5]. While there exists widespread agreement that raking or sieving the bulk regolith is good strategy, there is lively discussion about the minimum sample size. Advocates of consor-tium studies desire fragments large enough to support petrologic and isotopic studies. Fragments from 5 to 10 mm are thought adequate [4, 5]. Yet, Jolliff et al. [6] demonstrated use of 2-4 mm fragments as repre-sentative of larger rocks. Here we make use of cura-torial records and sample catalogs to give a different perspective on minimum sample size for a robotic sample collector.

Geologic map of the Bodie Hills, California and Nevada

USGS Publications Warehouse

John, David A.; du Bray, Edward A.; Box, Stephen E.; Vikre, Peter G.; Rytuba, James J.; Fleck, Robert J.; Moring, Barry C.

2015-01-01

The Bodie Hills covers about 1,200 km2 straddling the California-Nevada state boundary just north of Mono Lake in the western part of the Basin and Range Province, about 20 km east of the central Sierra Nevada. The area is mostly underlain by the partly overlapping, middle to late Miocene Bodie Hills volcanic field and Pliocene to late Pleistocene Aurora volcanic field (John and others, 2012). Upper Miocene to Pliocene sedimentary deposits, mostly basin-filling sediments, gravel deposits, and fanglomerates, lap onto the west, north, and east sides of the Bodie Hills, where they cover older Miocene volcanic rocks. Quaternary surficial deposits, including extensive colluvial, fluvial, glacial, and lacustrine deposits, locally cover all older rocks. Miocene and younger rocks are tilted ≤30° in variable directions. These rocks are cut by several sets of high-angle faults that exhibit a temporal change from conjugate northeast-striking left-lateral and north-striking right-lateral oblique-slip faults in rocks older than about 9 Ma to north- and northwest-striking dip-slip faults in late Miocene rocks. The youngest faults are north-striking normal and northeast-striking left-lateral oblique-slip faults that cut Pliocene-Pleistocene rocks. Numerous hydrothermal systems were active during Miocene magmatism and formed extensive zones of hydrothermally altered rocks and several large mineral deposits, including gold- and silver-rich veins in the Bodie and Aurora mining districts (Vikre and others, in press).

Effect of spatially and temporally variable recharge on subsurface reactive transport of contaminants at Oak Ridge Integrated Field Research Challenge site

NASA Astrophysics Data System (ADS)

Kumar, J.; Lichtner, P. C.; Mills, R. T.; Hammond, G. E.; Svyatskiy, D.; Tang, G.; Brooks, S. C.; Watson, D. B.; Parker, J.

2011-12-01

Recharge is one of the most fundamental components of groundwater systems which drives both flow and transport in the subsurface and plays an important role in the migration of contaminants at the Oak Ridge Integrated Field Research Challenge (ORIFRC) site. The area receives an average of 137 cm of precipitation per year, most of it during winter. About 50% of the precipitation is lost to evapotranspiration, 40% runs off directly to surface water, and less than 10% recharges to ground water. The migration of the reactive contaminant plume at the site is modeled using the massively parallel flow and reactive transport model PFLOTRAN. The geology at the site consists of dipping beds of limestone, shale and sandstone with strike N 55° E and dip 45° SE, over which is superimposed a highly porous, horizontally oriented, saprolite weathering profile. To model this system in 3-D a grid was constructed with x-axis aligned with the strike of the geologic formation and z-axis vertical. This formulation requires a full permeability tensor with off-diagonal components obtained by rotation of the principal axes tensor through the formation dip angle. A full tensor capability was implemented in PFLOTRAN using the mimetic finite difference (MFD) method, a mass conserving, second-order accurate scheme with auxiliary pressure degrees of freedom at grid cell faces. A complex geochemical fluid with 17 primary reactive species and a number of minerals was implemented to model the contaminant discharged from the S-3 ponds at the ORIFRC site. A 50-year history of observed rainfall at the site was used as input to the model to estimate transient recharge conditions and to study the effect of spatially and temporally varied recharge. Results from the investigations of impact of spatio-temporal variation in recharge on the migration of contaminant plume will be presented.

High-resolution seismic reflection imaging of growth folding and shallow faults beneath the Southern Puget Lowland, Washington State

USGS Publications Warehouse

Clement, C.R.; Pratt, T.L.; Holmes, M.L.; Sherrod, B.L.

2010-01-01

Marine seismic reflection data from southern Puget Sound, Washington, were collected to investigate the nature of shallow structures associated with the Tacoma fault zone and the Olympia structure. Growth folding and probable Holocene surface deformation were imaged within the Tacoma fault zone beneath Case and Carr Inlets. Shallow faults near potential field anomalies associated with the Olympia structure were imaged beneath Budd and Eld Inlets. Beneath Case Inlet, the Tacoma fault zone includes an ???350-m wide section of south-dipping strata forming the upper part of a fold (kink band) coincident with the southern edge of an uplifted shoreline terrace. An ???2 m change in the depth of the water bottom, onlapping postglacial sediments, and increasing stratal dips with increasing depth are consistent with late Pleistocene to Holocene postglacial growth folding above a blind fault. Geologic data across a topographic lineament on nearby land indicate recent uplift of late Holocene age. Profiles acquired in Carr Inlet 10 km to the east of Case Inlet showed late Pleistocene or Holocene faulting at one location with ???3 to 4 m of vertical displacement, south side up. North of this fault the data show several other disruptions and reflector terminations that could mark faults within the broad Tacoma fault zone. Seismic reflection profiles across part of the Olympia structure beneath southern Puget Sound show two apparent faults about 160 m apart having 1 to 2 m of displacement of subhorizontal bedding. Directly beneath one of these faults, a dipping reflector that may mark the base of a glacial channel shows the opposite sense of throw, suggesting strike-slip motion. Deeper seismic reflection profiles show disrupted strata beneath these faults but little apparent vertical offset, consistent with strike-slip faulting. These faults and folds indicate that the Tacoma fault and Olympia structure include active structures with probable postglacial motion.

High-resolution seismic reflection imaging of growth folding and shallow faults beneath the Southern Puget Lowland, Washington State

USGS Publications Warehouse

Odum, Jackson K.; Stephenson, William J.; Pratt, Thomas L.; Blakely, Richard J.

2016-01-01

Marine seismic reflection data from southern Puget Sound, Washington, were collected to investigate the nature of shallow structures associated with the Tacoma fault zone and the Olympia structure. Growth folding and probable Holocene surface deformation were imaged within the Tacoma fault zone beneath Case and Carr Inlets. Shallow faults near potential field anomalies associated with the Olympia structure were imaged beneath Budd and Eld Inlets. Beneath Case Inlet, the Tacoma fault zone includes an ∼350-m wide section of south-dipping strata forming the upper part of a fold (kink band) coincident with the southern edge of an uplifted shoreline terrace. An ∼2 m change in the depth of the water bottom, onlapping postglacial sediments, and increasing stratal dips with increasing depth are consistent with late Pleistocene to Holocene postglacial growth folding above a blind fault. Geologic data across a topographic lineament on nearby land indicate recent uplift of late Holocene age. Profiles acquired in Carr Inlet 10 km to the east of Case Inlet showed late Pleistocene or Holocene faulting at one location with ∼3 to 4 m of vertical displacement, south side up. North of this fault the data show several other disruptions and reflector terminations that could mark faults within the broad Tacoma fault zone. Seismic reflection profiles across part of the Olympia structure beneath southern Puget Sound show two apparent faults about 160 m apart having 1 to 2 m of displacement of subhorizontal bedding. Directly beneath one of these faults, a dipping reflector that may mark the base of a glacial channel shows the opposite sense of throw, suggesting strike-slip motion. Deeper seismic reflection profiles show disrupted strata beneath these faults but little apparent vertical offset, consistent with strike-slip faulting. These faults and folds indicate that the Tacoma fault and Olympia structure include active structures with probable postglacial motion.

Broadening the interpretive framework of deepwater deposits: 3D characterization of outcrop scale bedforms within supercritical dominated slope deposits of the Fish Creek-Vallecito Basin, Late-Miocene Gulf of California

NASA Astrophysics Data System (ADS)

West, L. M.; Steel, R.; Olariu, C.

2017-12-01

Study of seafloor bathymetry, numerical and physical modeling, and direct observation of turbidity currents increasingly suggests that sediment gravity flows over moderately steep basin slopes commonly reach Froude supercritical states. However, interpretation of supercritical features in deepwater outcrops remains limited in both quantity and scope, leaving stratigraphic qualities of supercritical deposits poorly understood. Slope turbidites on along steep margins of the early Gulf of California are exposed in seismic scale outcrops of the Late Miocene Lycium Member in the Fish Creek-Vallecito Basin of south-central California where they build 100s m-thick slopes. Measured sections, bedding orientation, and facies descriptions collected both for strike- and dip-oriented sections are combined with photogrammetric to characterize selected bedforms in three-dimensions. Analysis shows upflow accreting stacks of 10s of beds into a variety of bedforms with wavelengths and widths tens to hundreds of meters in scale and heights of 5-15 m. Beds have low-angle sinusoidal to sigmoidal down dip geometries and lens or lobate strike geometries. Bedding facies are dominated by 5-50 cm thick, normally graded, laminated sandstones capped by 1-3 cm bioturbated muds. Sandstones transition into interbedded sandstones and silty mudstones or 1-2 m thick silty mudstones. In places, Present also are incisional, steeply dipping backsets of 0.5-3 m-thick boulder-rich, amalgamated, structureless sandtones with abundant soft sediment deformation. that can transition downflow into arching, thinning, normally-graded sandstones. These bedforms are interpreted here as large-scale, long-lived supercritical deposits that represent preserved antidune and possibly cyclic steps bedforms or as-yet undefined bedforms incorporating by not bound by hydraulic jumps. This characterization provides new understanding of the nature of supercritical deposits and an important framework criteria for recognizing similar deposits elsewhere.

Relocation of recent seismicity and seismotectonic properties in the Gulf of Corinth (Greece)

NASA Astrophysics Data System (ADS)

Mesimeri, Maria; Karakostas, Vassilios; Papadimitriou, Eleftheria; Tsaklidis, George; Jacobs, Katrina

2018-02-01

Recent seismicity (2008-2014) taking place in the Gulf of Corinth and recorded, since the establishment of the Hellenic Unified Seismological Network is relocated in this study. All the available P and S manually picked phases along with the waveforms of 55 broad-band, three-component seismological stations were used. The relocation is performed using the double difference method with differential times derived from phase-picked data and waveform cross-correlation. The accuracy of the relocated catalogue, estimated using a bootstrap approach, is of the order of few hundred metres. In an attempt to define the stress regime in the area, we compute moment tensors of 72 earthquakes with ML ≥ 3.0 and use them to calculate the total seismic moment tensor. A dominant strike of 270° that found in the westernmost part, was changed to 270°-290° at the centre of the gulf, perpendicular to the almost N-S extension of the rift. Further to the east, a gradual change in fault orientation is observed. In the easternmost part, the strike becomes 240°, in agreement with the geometry of the rift. The highly accurate earthquake catalogue, consisting of ˜26 000 events, reveals two patterns of activity in the western Corinth Gulf, namely, strongly clustered seismicity in both space and time in shallow depths and below that activity a very narrow shallow north-dipping seismic zone. Earthquake clusters, mainly located in the western study area, are identified using CURATE algorithm and associated with different north or south-dipping fault segments. The seismicity in the shallow north-dipping seismic zone, defined in detail in this study, is continuous and free of earthquake clusters. This continuous activity most probably defines the boundaries between brittle and ductile layers. The central and eastern parts of the study area mainly accommodate spatiotemporal clusters.

Evidence for large-magnitude, post-Eocene extension in the northern Shoshone Range, Nevada, and its implications for Carlin-type gold deposits in the lower plate of the Roberts Mountains allochthon

USGS Publications Warehouse

Colgan, Joseph P.; Henry, Christopher D.; John, David A.

2014-01-01

The northern Shoshone and Toiyabe Ranges in north-central Nevada expose numerous areas of mineralized Paleozoic rock, including major Carlin-type gold deposits at Pipeline and Cortez. Paleozoic rocks in these areas were previously interpreted to have undergone negligible postmineralization extension and tilting, but here we present new data that suggest major post-Eocene extension along west-dipping normal faults. Tertiary rocks in the northern Shoshone Range crop out in two W-NW–trending belts that locally overlie and intrude highly deformed Lower Paleozoic rocks of the Roberts Mountains allochthon. Tertiary exposures in the more extensive, northern belt were interpreted as subvertical breccia pipes (intrusions), but new field data indicate that these “pipes” consist of a 35.8 Ma densely welded dacitic ash flow tuff (informally named the tuff of Mount Lewis) interbedded with sandstones and coarse volcaniclastic deposits. Both tuff and sedimentary rocks strike N-S and dip 30° to 70° E; the steeply dipping compaction foliation in the tuffs was interpreted as subvertical flow foliation in breccia pipes. The southern belt along Mill Creek, previously mapped as undivided welded tuff, includes the tuff of Cove mine (34.4 Ma) and unit B of the Bates Mountain Tuff (30.6 Ma). These tuffs dip 30° to 50° east, suggesting that their west-dipping contacts with underlying Paleozoic rocks (previously mapped as depositional) are normal faults. Tertiary rocks in both belts were deposited on Paleozoic basement and none appear to be breccia pipes. We infer that their present east tilt is due to extension on west-dipping normal faults. Some of these faults may be the northern strands of middle Miocene (ca. 16 Ma) faults that cut and tilted the 34.0 Ma Caetano caldera ~40° east in the central Shoshone Range (

Laser goniometer

DOEpatents

Fairer, George M.; Boernge, James M.; Harris, David W.; Campbell, DeWayne A.; Tuttle, Gene E.; McKeown, Mark H.; Beason, Steven C.

1993-01-01

The laser goniometer is an apparatus which permits an operator to sight along a geologic feature and orient a collimated lamer beam to match the attitude of the feature directly. The horizontal orientation (strike) and the angle from horizontal (dip), are detected by rotary incremental encoders attached to the laser goniometer which provide a digital readout of the azimuth and tilt of the collimated laser beam. A microprocessor then translates the square wave signal encoder outputs into an ASCII signal for use by data recording equipment.

Survivorship of raked and unraked trees through prescribed fires in conifer forests in northeastern California

Treesearch

William F. Laudenslayer; George N. Steger; Jonathan Arnold

2008-01-01

Large diameter, old trees are an important component of functioning forests, as they provide habitat for many wildlife species and add value to the scenery along roads and trails that cross our National Forests and Parks. Tree mortality, from prescribed or wild fire, is of great concern to forests managers, especially mortality of those of large diameter. Raking away...

The Quaternary Silver Creek Fault Beneath the Santa Clara Valley, California

USGS Publications Warehouse

Wentworth, Carl M.; Williams, Robert A.; Jachens, Robert C.; Graymer, Russell W.; Stephenson, William J.

2010-01-01

The northwest-trending Silver Creek Fault is a 40-km-long strike-slip fault in the eastern Santa Clara Valley, California, that has exhibited different behaviors within a changing San Andreas Fault system over the past 10-15 Ma. Quaternary alluvium several hundred meters thick that buries the northern half of the Silver Creek Fault, and that has been sampled by drilling and imaged in a detailed seismic reflection profile, provides a record of the Quaternary history of the fault. We assemble evidence from areal geology, stratigraphy, paleomagnetics, ground-water hydrology, potential-field geophysics, and reflection and earthquake seismology to determine the long history of the fault in order to evaluate its current behavior. The fault formed in the Miocene more than 100 km to the southeast, as the southwestern fault in a 5-km-wide right step to the Hayward Fault, within which the 40-km-long Evergreen pull-apart basin formed. Later, this basin was obliquely cut by the newly recognized Mt. Misery Fault to form a more direct connection to the Hayward Fault, although continued growth of the basin was sufficient to accommodate at least some late Pliocene alluvium. Large offset along the San Andreas-Calaveras-Mt Misery-Hayward Faults carried the basin northwestward almost to its present position when, about 2 Ma, the fault system was reorganized. This led to near abandonment of the faults bounding the pull-apart basin in favor of right slip extending the Calaveras Fault farther north before stepping west to the Hayward Fault, as it does today. Despite these changes, the Silver Creek Fault experienced a further 200 m of dip slip in the early Quaternary, from which we infer an associated 1.6 km or so of right slip, based on the ratio of the 40-km length of the strike-slip fault to a 5-km depth of the Evergreen Basin. This dip slip ends at a mid-Quaternary unconformity, above which the upper 300 m of alluvial cover exhibits a structural sag at the fault that we interpret as a negative flower structure. This structure implies some continuing strike slip on the Silver Creek Fault in the late Quaternary as well, with a transtensional component but no dip slip. Our only basis for estimating the rate of this later Quaternary strike slip on the Silver Creek Fault is to assume continuation of the inferred early Quaternary rate of less than 2 mm/yr. Faulting evident in a detailed seismic reflection profile across the Silver Creek Fault extends up to the limit of data at a depth of 50 m and age of about 140 ka, and the course of Coyote Creek suggests Holocene capture in a structural depression along the fault. No surface trace is evident on the alluvial plain, however, and convincing evidence of Holocene offset is lacking. Few instrumentally recorded earthquakes are located near the fault, and those that are near its southern end represent cross-fault shortening, not strike slip. The fault might have been responsible, however, for two poorly located moderate earthquakes that occurred in the area in 1903. Its southeastern end does mark an abrupt change in the pattern of abundant instrumentally recorded earthquakes along the Calaveras Fault-in both its strike and in the depth distribution of hypocenters-that could indicate continuing influence by the Silver Creek Fault. In the absence of convincing evidence to the contrary, and as a conservative estimate, we presume that the Silver Creek Fault has continued its strike-slip movement through the Holocene, but at a very slow rate. Such a slow rate would, at most, yield very infrequent damaging earthquakes. If the 1903 earthquakes did, in fact, occur on the Silver Creek Fault, they would have greatly reduced the short-term future potential for large earthquakes on the fault.

Rupture behaviors of the 2010 Jiashian and 2016 Meinong Earthquakes: Implication for interaction of two asperities on the Chishan Transfer Fault Zone in SW Taiwan.

NASA Astrophysics Data System (ADS)

Jian, P. R.; Hung, S. H.; Chen, Y. L.; Meng, L.; Tseng, T. L.

2017-12-01

After about 45 years of seismic quiescence, southwest Taiwan was imperiled by two strong earthquakes, the 2010 Mw 6.2 Jiashian and deadly 2016 Mw 6.4 Meinong earthquakes in the last decade. The focal mechanisms and their aftershock distributions imply that both events occurred on NW-SE striking, shallow-dipping fault planes but at different depths of 21 and 16 km, respectively. Here we present the MUSIC back projection images using high-frequency P- and sP-waves recorded in the European and Australian seismic networks, the directivity analysis using global teleseismic P waves and relocated aftershocks to characterize the rupture behaviors of the two mainshocks and explore the potential connection between them. The results for the Meinong event indicate a unilateral, subhorizontal rupture propagating NW-ward 17 km and lasting for 6-7 s [Jian et al., 2017]. For the Jiashian event, the rupture initiated at a greater depth of 21 km and then propagated both NW-ward and up-dip ( 16o) on the fault plane, with a shorter rupture length of 10 km and duration of 4-5 s. The up-dip propagation is corroborated by the 3-D directivity analysis that leads to the widths of P-wave pulses increasing linearly with the directivity parameter. Moreover, relocation of aftershocks reveals that the Jiashian sequence is confined in a NW-SE elongated zone extending 15 km and 5 km shallower than the hypocenter. The Meinong aftershock sequence shows three clusters: one surrounding the mainshock hypocenter, another one distributed northwestern and deeper (>20 km) off the rupture plane beneath Tainan, and the other distant shallow-focus one (<10 km) beneath the southern Central Mountain Range. As evidenced by similar focal mechanism, rupture behaviors, as well as the spatial configuration of the mainshock rupture zones and aftershock distributions, we attribute the Jiashian and Meinong earthquakes to two asperities on a buried oblique fault that has been reactivated recently, the NW-SE striking Chishan Transfer Fault Zone as a likely candidate rupture plane. In 2010, the Jiasian earthquake initiated at the deeper NE asperity and propagated NW-ward and up-dip. Six years later, the stronger shallower asperity responsible for the Meinong event was statically triggered, which consequently caused the ruinous destruction in SW Taiwan.

Crustal structure and evolution of the Trans-Hudson orogen: Results from seismic reflection profiling

NASA Astrophysics Data System (ADS)

Baird, D. J.; Nelson, K. D.; Knapp, J. H.; Walters, J. J.; Brown, L. D.

1996-04-01

A 400-km-long deep seismic reflection transect across northeastern Montana and northern North Dakota reveals the crustal-scale structural fabric of the Early Proterozoic Trans-Hudson orogen beneath the Williston basin. Comparison with deep seismic reflection data across the Canadian portion of the same orogen ˜700 km to the north reveals first-order similarities in crustal architecture but documents significant along-strike variation in orogenic evolution. Both transects display a broad crustal-scale antiform axial to the orogen. In the north, geologic data suggest that this antiform is cored by an Archean microcontinent. In the south, west dipping reflections on the western flank of the antiform extend from the upper crust to the uppermost mantle and truncate prominent subhorizontal lower crustal reflections of the Archean Wyoming craton. Within the Wyoming craton, the eastern limit of east dipping midcrustal reflections coincides with the subsurface age boundary between the craton and the Early Proterozoic Trans-Hudson orogen as interpreted from potential field and drill core data. On the basis of subsurface geochronologic data from the crystalline basement and by analogy with the Glennie domain within the exposed Trans-Hudson orogen in Canada, we suggest that the southern antiform is cored by an Archean crustal fragment that was caught up in the terminal collision of the Wyoming and Superior cratons during Hudsonian orogeny. The eastern side of the Trans-Hudson orogen is characterized on both seismic transects by predominantly east dipping crustal penetrating reflections. We interpret the easterly dip of these reflections as evidence that the Superior province was thrust westward over the interludes of the orogen during terminal collision. Although juvenile Early Proterozoic terranes characterize the exposed segment of the Trans-Hudson orogen in Canada, limited drill core information within the Dakota segment of the orogen shows a predominance of granulitic Archean age crust. This difference in basement lithologies along strike within the orogen may indicate the following: either juvenile crust comparable to that exposed in the northern Trans-Hudson was never present in the south, or it was removed by progressive over thickening, erosion, and/or faulting. Postorogenic extensional collapse may be responsible for preservation of juvenile terranes in the north.

Blind information-theoretic multiuser detection algorithms for DS-CDMA and WCDMA downlink systems.

PubMed

Waheed, Khuram; Salem, Fathi M

2005-07-01

Code division multiple access (CDMA) is based on the spread-spectrum technology and is a dominant air interface for 2.5G, 3G, and future wireless networks. For the CDMA downlink, the transmitted CDMA signals from the base station (BS) propagate through a noisy multipath fading communication channel before arriving at the receiver of the user equipment/mobile station (UE/MS). Classical CDMA single-user detection (SUD) algorithms implemented in the UE/MS receiver do not provide the required performance for modern high data-rate applications. In contrast, multi-user detection (MUD) approaches require a lot of a priori information not available to the UE/MS. In this paper, three promising adaptive Riemannian contra-variant (or natural) gradient based user detection approaches, capable of handling the highly dynamic wireless environments, are proposed. The first approach, blind multiuser detection (BMUD), is the process of simultaneously estimating multiple symbol sequences associated with all the users in the downlink of a CDMA communication system using only the received wireless data and without any knowledge of the user spreading codes. This approach is applicable to CDMA systems with relatively short spreading codes but becomes impractical for systems using long spreading codes. We also propose two other adaptive approaches, namely, RAKE -blind source recovery (RAKE-BSR) and RAKE-principal component analysis (RAKE-PCA) that fuse an adaptive stage into a standard RAKE receiver. This adaptation results in robust user detection algorithms with performance exceeding the linear minimum mean squared error (LMMSE) detectors for both Direct Sequence CDMA (DS-CDMA) and wide-band CDMA (WCDMA) systems under conditions of congestion, imprecise channel estimation and unmodeled multiple access interference (MAI).

Influence of intertidal recreational fisheries and 'bouchot' mussel culture on bivalve recruitment.

PubMed

Toupoint, Nicolas; Barbier, Pierrick; Tremblay, Réjean; Archambault, Philippe; McKindsey, Christopher W; Winkler, Gesche; Meziane, Tarik; Olivier, Frédéric

2016-06-01

In coastal environments, fishing and aquaculture may be important sources of disturbance to ecosystem functioning, the quantification of which must be assessed to make them more sustainable. In the Chausey Archipelago, France, recreational fishing and commercial shellfish farming are the only two evident anthropogenic activities, dominated by bivalve hand-raking and 'bouchot' mussel culture, respectively. This study evaluates the impact of both activities on bivalve recruitment dynamics by comparing primary recruitment intensity (short-term effect) and recruitment efficiency (medium-term effect) by sampling bivalves in reference (undisturbed) and disturbed (i.e. subjected to hand-raking or in 'bouchot' mussel culture areas) parcels throughout and at the end of the recruitment season, respectively. Specific hypotheses evaluated were that (H1) bivalve hand-raking negatively affects bivalve recruitment and that (H2) 'bouchot' mussel culture promotes bivalve recruitment. Patterns in bivalve community structure in reference parcels (i.e. natural pattern) differed between initial and final recruitment, underlining the great importance of early post-settlement processes, particularly secondary dispersal. Primary recruitment intensity was inhibited in hand-raking parcels whereas it was promoted in 'bouchot' mussel culture parcels, but the effect on recruitment efficiency was muted for both activities due to post-settlement processes. Nevertheless, the importance of effects that occur during the first step of recruitment should not be ignored as they may affect bivalve communities and induce immediate consequences on the trophic web through a cascade effect. Finally, it is highlighted that hand-raking damages all life stages of the common cockle Cerastoderma edule, one of the major target species, suggesting that this activity should be managed with greater caution than is currently done. Copyright © 2016 Elsevier Ltd. All rights reserved.

F-16XL ship #1 outboard rake #7

NASA Technical Reports Server (NTRS)

1996-01-01

This photo shows the #7 outboard rake on the left wing of NASA's single-seat F-16XL (ship #1) used for the Cranked-Arrow Wing Aerodynamic Project (CAWAP) at Dryden Flight Research Center, Edwards, California. The modified airplane features a delta 'cranked-arrow' wing with strips of tubing along the leading edge to the trailing edge to sense static on the wing and obtain pressure distribution data. The right wing receives data on pressure distribution and the left wing has three types of instrumentation - preston tubes to measure local skin friction, boundary layer rakes to measure boundary layer profiles (the layer where the air interacts with the surfaces of a moving aircraft), and hot films to determine boundary layer transition locations. The first flight of CAWAP occurred on November 21, 1995, and the test program ended in April 1996.

Shallow seismicity of arc-continent collision near Lae, Papua New Guinea

NASA Astrophysics Data System (ADS)

Kulig, Christopher; McCaffrey, Robert; Abers, Geoffrey A.; Letz, Horst

1993-11-01

In northeastern New Guinea, the narrow Ramu-Markham Valley (RMV) separates island arc rocks to the north from those of continental origin to the south and appears to be the western, onland extension of the New Britain trench. To explore the tectonic processes at the leading edge of the island arc during collision, we operated a portable seismic network for six weeks near the city of Lae at the eastern end of the RMV. We observed a narrow, near-vertical belt of seismicity between 10 and 30 km depth, that we call the Lae Seismic Zone (LSZ), starting at the RMV in the southwest and trending northeasterly cutting across surface geologic structure. The truncation of the LSZ along a steep plane by the Ramu-Markham Fault Zone (RMFZ) and earthquake first motions suggest that the earthquakes occur in the hanging wall of a steep, N-dipping fault that crops out at the RMFZ. We also consider that the LSZ is within the lower plate of a gently dipping thrust. Below 20 km depth the microearthquake zone is truncated by a gently, NE-dipping plane coinciding in depth and dip with nodal planes of recent large ( mb = 5.6 and 6.0) thrust earthquakes. We suggest that the Huon Peninsula is being emplaced onto the Australian plate along a gently (~ 25°) dipping thrust fault that is 20 km deep beneath Lae. The RMFZ may be a steeply dipping thrust fault that connects with this gently, N-dipping thrust but accommodates little convergence at present. The LSZ trends nearly perpendicular to an anticlinal range which appears to be sheared in a left-lateral sense. P-wave first motions for earthquakes in the LSZ with steep (70° to 90° dip) nodal planes that strike parallel to the LSZ suggest a component of south-side-up displacement also. Hence, the crustal block south of the LSZ may be rising relative to the Huon Peninsula and the rapid Quaternary uplift rates estimated for the Lae coastal region may be higher than the uplift rate of the Huon Peninsula as a whole. We suggest that the LSZ reveals a tear of small offset in the Huon terrane but may be similar to a structure that produced a magnitude 7 earthquake near Madang in 1970.

Deformation along the leading edge of the Maiella thrust sheet in central Italy

NASA Astrophysics Data System (ADS)

Aydin, Atilla; Antonellini, Marco; Tondi, Emanuele; Agosta, Fabrizio

2010-09-01

The eastern forelimb of the Maiella anticline above the leading edge of the underlying thrust displays a complex system of fractures, faults and a series of kink bands in the Cretaceous platform carbonates. The kink bands have steep limbs, display top-to-the-east shear, parallel to the overall transport direction, and are brecciated and faulted. A system of pervasive normal faults, trending sub-parallel to the strike of the mechanical layers, accommodates local extension generated by flexural slip. Two sets of strike-slip faults exist: one is left-lateral at a high angle to the main Maiella thrust; the other is right-lateral, intersecting the first set at an acute angle. The normal and strike-slip faults were formed by shearing across bed-parallel, strike-, and dip-parallel pressure solution seams and associated splays; the thrust faults follow the tilted mechanical layers along the steeper limb of the kink bands. The three pervasive, mutually-orthogonal pressure solution seams are pre-tilting. One set of low-angle normal faults, the oldest set in the area, is also pre-tilting. All other fault/fold structures appear to show signs of overlapping periods of activity accounting for the complex tri-shear-like deformation that developed as the front evolved during the Oligocene-Pliocene Apennine orogeny.

Design of a constant tension thermocouple rake suitable for flame studies

NASA Technical Reports Server (NTRS)

Ahuja, Sandeep; Miller, David L.

1993-01-01

An improved, spring-loaded thermocouple rake, suitable for studying flame structure, has been designed. This design keeps the thermocouple under tension thereby ensuring that the thermocouple does not droop due to the thermal expansion of the sensing wire when inserted in the flame. The present design allows the usage of thermocouple wire as small as 0.0508 mm and relative ease in changing thermocouple wire.

Noise Identification in a Hot Transonic Jet Using Low-Dimensional Methods

DTIC Science & Technology

2008-03-01

calibration between the nozzle static pressure (transducer) and total pressure ( pitot probe) reveals a nearly linear relationship between the two, exhibiting... rakes of hot-wires. Multi-point correlations of velocity components coupled with assumptions of homogeneity and periodicity in the jet flow flied...axisymmetric incompressible jet at one downstream position using an in-house designed rake of 138 hot-wires. The experiment was then carried out at multiple

Calibration of averaging total pressure flight wake rake and natural-laminar-flow airfoil drag certification

NASA Technical Reports Server (NTRS)

Irani, E.; Snyder, M. H.

1988-01-01

An averaging total pressure wake rake used by the Cessna Aircraft Company in flight tests of a modified 210 airplane with a laminar flow wing was calibrated in wind tunnel tests against a five-tube pressure probe. The model generating the wake was a full-scale model of the Cessna airplane wing. Indications of drag trends were the same for both instruments.

A sex difference in effect of prior experience on object-mediated problem-solving in gibbons.

PubMed

Cunningham, Clare; Anderson, James; Mootnick, Alan

2011-07-01

Understanding the functionally relevant properties of objects is likely facilitated by learning with a critical role for past experience. However, current evidence is conflicting regarding the effect of prior object exposure on acquisition of object manipulation skills. This may be due to the influence of life history variables on the capacity to benefit from such experience. This study assessed effect of task-relevant object exposure on object-mediated problem-solving in 22 gibbons using a raking-in task. Despite not using tools habitually, 14 gibbons spontaneously used a rake to obtain a reward. Having prior experience with the rake in an unrewarded context did not improve learning efficiency in males. However, females benefitted significantly from the opportunity to interact with the rake before testing, with reduced latencies to solution compared to those with no previous exposure. These results reflect potential sex differences in approach to novelty that moderate the possible benefits of prior experience. Due to their relatively high energetic requirements, reproductively active females may be highly motivated to explore potential resources; however, increased investment in developing offspring could make them more guarded in their investigations. Previous exposure that allows females to learn of an object's neutrality can offset this cautious exploration.

Coseismic and Postseismic Deformation Due to the 2010 El Mayor-Cucapah Earthquake Detected by ALOS/PALSAR Data

NASA Astrophysics Data System (ADS)

Okamoto, J.; Hashimoto, M.; Fukushima, Y.

2011-12-01

On April 4th, 2010, the Mw 7.2 El Mayor-Cucapah earthquake occurred in northeast Baja California, near the US-Mexico border. Since then, ALOS/PALSAR observed this region twenty times, which provides a rich data set to study the co- and post-seismic deformation. We first estimated the slip distribution and dip angle of the fault plane by inverting InSAR data with the method developed by Fukahata and Wright (2008). With this method, we can obtain the slip distribution on a plane fault and its dip angle simultaneously by minimizing the ABIC (Akaike's Bayesian Information Criterion). In southeastern area near the Gulf of California, we could recognize effects of liquefaction, so we did not use the data in such areas in the inversion. We assumed one sufficiently large rectangular plane fault and the strike is assumed to be 313 degrees from the north. After trials and errors, we restricted the search of the dip angle in a range of 30-90 degrees, dipping northeastward. The optimal dip angle was estimated 68 degrees, which is smaller than 82 degrees of the CMT solution (USGS). Right lateral strike slips with slight normal component were estimated, and the maximum slip of about 3m was obtained in the northwestern vicinity of the hypocenter. The total geodetic moment of our best-fitting model was in a good agreement with the seismic moment. In the postseismic period, we detected signals at two locations that can be attributed to postseismic deformation. First, we recognize some signals near the northwestern edge of the source fault in all the early postseismic interferograms (46 days after the earthquake) of both ascending and descending directions. In this area, the coseismic slip was estimated to be about 2m. We performed some forward calculations to confirm that this signal is not likely to be due to aftershocks. We computed the poroelastic deformation based on our coseismic slip model and found that the observed signal has the opposite sense. Moreover, a 2.5 dimensional analysis showed several centimeters of westward displacements, but almost none vertical component. These results suggest that this signal is due to an afterslip and/or visco-elastic response. The second postseismic signal is observed along Laguna Salada fault by a relatively long (half a year) descending interferogram. This signal is not well correlated with topography, which reduces the possibility of atmospheric noise. On the other hand, it can be reasonably explained by an afterslip above a large coseismic slip patch, although there still remains the possibility of atmospheric noise as only one interferogram captures this signal.

Movement sense determination in sheared rocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simpson, C.

1985-01-01

Deformation within fault zones produces sheared rocks that range from cataclasites at high structural level, to mylonites and mylonitic gneiss at deeper levels. These rocks are easily recognized and mapped in the field and the strike and dip of the fault zone established. However, present-day geometry of the fault zone does not necessarily indicate relative motion - a zone dipping at 15/sup 0/ could represent a listric normal, thrust, oblique-slip or tilted strike-slip fault. Where offset stratigraphic or lithological markers are absent, the movement sense may be determined from meso- and micro-structural features within the sheared rocks. Of prime importancemore » is the orientation of mineral elongation or stretching lineations which record the finite X direction of strain in the rock; this direction approaches the bulk movement direction with increase in strain. At mesoscopic scale the most reliable shear sense indicators are shear bands and associated features. Use of fold vergence requires caution. On a micro-structural scale, shear bands, mica fish, microfolds, rotated grains, asymmetrical augen structure and fiber growth patterns all give reliable results. Thin sections should be cut parallel to lineation and perpendicular to foliation in order to view maximum rotational component. Asymmetry of crystallographic fabric patterns gives consistent results in zones of relatively simple movement history. For high confidence shear sense determination, all structural elements should be internally consistent. If inconsistency occurs this may indicate a complex, multidirectional movement history for the fault zone.« less

Ground-penetrating radar investigation of active faults along the Dead Sea Transform and implications for seismic hazards within the city of Aqaba, Jordan

NASA Astrophysics Data System (ADS)

Slater, Lee; Niemi, Tina M.

2003-06-01

Ground-penetrating radar (GPR) was used in an effort to locate a major active fault that traverses Aqaba City, Jordan. Measurements over an exposed (trenched) cross fault outside of the city identify a radar signature consisting of linear events and horizontal offset/flexured reflectors both showing a geometric correlation with two known faults at a control site. The asymmetric linear events are consistent with dipping planar reflectors matching the known direction of dip of the faults. However, other observations regarding this radar signature render the mechanism generating these events more complex and uncertain. GPR measurements in Aqaba City were limited to vacant lots. Seven GPR profiles were conducted approximately perpendicular to the assumed strike of the fault zone, based on regional geological evidence. A radar response very similar to that obtained over the cross fault was observed on five of the profiles in Aqaba City, although the response is weaker than that obtained at the control site. The positions of the identified responses form a near straight line with a strike of 45°. Although subsurface verification of the fault by trenching within the city is needed, the geophysical evidence for fault zone location is strong. The location of the interpreted fault zone relative to emergency services, military bases, commercial properties, and residential areas is defined to within a few meters. This study has significant implications for seismic hazard analysis in this tectonically active and heavily populated region.

Normal Fault Type Earthquakes Off Fukushima Region - Comparison of the 1938 Events and Recent Earthquakes -

NASA Astrophysics Data System (ADS)

Murotani, S.; Satake, K.

2017-12-01

Off Fukushima region, Mjma 7.4 (event A) and 6.9 (event B) events occurred on November 6, 1938, following the thrust fault type earthquakes of Mjma 7.5 and 7.3 on the previous day. These earthquakes were estimated as normal fault earthquakes by Abe (1977, Tectonophysics). An Mjma 7.0 earthquake occurred on July 12, 2014 near event B and an Mjma 7.4 earthquake occurred on November 22, 2016 near event A. These recent events are the only M 7 class earthquakes occurred off Fukushima since 1938. Except for the two 1938 events, normal fault earthquakes have not occurred until many aftershocks of the 2011 Tohoku earthquake. We compared the observed tsunami and seismic waveforms of the 1938, 2014, and 2016 earthquakes to examine the normal fault earthquakes occurred off Fukushima region. It is difficult to compare the tsunami waveforms of the 1938, 2014 and 2016 events because there were only a few observations at the same station. The teleseismic body wave inversion of the 2016 earthquake yielded with the focal mechanism of strike 42°, dip 35°, and rake -94°. Other source parameters were as follows: source area 70 km x 40 km, average slip 0.2 m, maximum slip 1.2 m, seismic moment 2.2 x 1019 Nm, and Mw 6.8. A large slip area is located near the hypocenter, and it is compatible with the tsunami source area estimated from tsunami travel times. The 2016 tsunami source area is smaller than that of the 1938 event, consistent with the difference in Mw: 7.7 for event A estimated by Abe (1977) and 6.8 for the 2016 event. Although the 2014 epicenter is very close to that of event B, the teleseismic waveforms of the 2014 event are similar to those of event A and the 2016 event. While Abe (1977) assumed that the mechanism of event B was the same as event A, the initial motions at some stations are opposite, indicating that the focal mechanisms of events A and B are different and more detailed examination is needed. The normal fault type earthquake seems to occur following the occurrence of M7 9 class thrust type earthquake at the plate boundary off Fukushima region.

Paleomagnetic and Seismologic Evidence for Oblique-Slip Partitioning to the Coalinga Anticline From the San Andreas Fault

NASA Astrophysics Data System (ADS)

Tetreault, J. L.; Jones, C. H.

2007-12-01

The Coalinga Anticline is a one of a series of fault-related folds in the central Coast Ranges, California, oriented subparallel to the San Andreas Fault (SAF). The development of the Central Coast Range anticlines can be related to the relative strength of the SAF. If positing a weak SAF, fault-normal slip is partitioned to these subparallel compressional folds. If the SAF is strong, these folds rotated to their current orientation during wrenching. Another possibility is that the Coast Range anticlines are accommodating oblique-slip partitioned from the SAF. The 1983 Coalinga earthquake does not have a purely thrusting focal mechanism (rake =100°), reflecting the likelihood that oblique slip is being partitioned to this anticline, even though surface expression of fold-axis-parallel slip has not been identified. Paleomagnetic vertical-axis rotations and focal mechanism strain inversions were used to quantify oblique-slip deformation within the Coalinga Anticline. Clockwise rotations of 10° to 16° are inferred from paleomagnetic sites located in late Miocene to Pliocene beds on the steeply dipping forelimb and backlimb of the fold. Significant vertical-axis rotations are not identified in the paleomagnetic sites within the nose of the anticline. The varying vertical axis rotations conflict with wrench tectonics (strong SAF) as the mechanism of fold development. We use focal mechanisms inversions of earthquakes that occurred between 1983 to 2006 to constrain the seismogenic strain within the fold that presumably help to build it over time. In the upper 7 km, the principal shortening axis is oriented N37E to N40E, statistically indistinguishable from normal to the fold (N45E). The right-lateral shear in the folded strata above the fault tip, evident from the paleomagnetically determined clockwise vertical-axis rotations, is being accommodated aseismically or interseismically. In the region between 7 and 11 km, where the mainshock occurred, the shortening direction ranges from oblique to normal to the fold trend. Our results show that right-lateral slip is resolved along the main fault plane and not distributed to the smaller aftershocks at depths of 7-11 km. The principal strain axes and clockwise paleomagnetic rotations indicate that the Coalinga Anticline is accommodating minor right-lateral shearing and thus shares some of the strike-slip motion of the San Andreas system.

Deterministic Tectonic Origin Tsunami Hazard Analysis for the Eastern Mediterranean and its Connected Seas

NASA Astrophysics Data System (ADS)

Necmioglu, O.; Meral Ozel, N.

2014-12-01

Accurate earthquake source parameters are essential for any tsunami hazard assessment and mitigation, including early warning systems. Complex tectonic setting makes the a priori accurate assumptions of earthquake source parameters difficult and characterization of the faulting type is a challenge. Information on tsunamigenic sources is of crucial importance in the Eastern Mediterranean and its Connected Seas, especially considering the short arrival times and lack of offshore sea-level measurements. In addition, the scientific community have had to abandon the paradigm of a ''maximum earthquake'' predictable from simple tectonic parameters (Ruff and Kanamori, 1980) in the wake of the 2004 Sumatra event (Okal, 2010) and one of the lessons learnt from the 2011 Tohoku event was that tsunami hazard maps may need to be prepared for infrequent gigantic earthquakes as well as more frequent smaller-sized earthquakes (Satake, 2011). We have initiated an extensive modeling study to perform a deterministic Tsunami Hazard Analysis for the Eastern Mediterranean and its Connected Seas. Characteristic earthquake source parameters (strike, dip, rake, depth, Mwmax) at each 0.5° x 0.5° size bin for 0-40 km depth (total of 310 bins) and for 40-100 km depth (total of 92 bins) in the Eastern Mediterranean, Aegean and Black Sea region (30°N-48°N and 22°E-44°E) have been assigned from the harmonization of the available databases and previous studies. These parameters have been used as input parameters for the deterministic tsunami hazard modeling. Nested Tsunami simulations of 6h duration with a coarse (2 arc-min) and medium (1 arc-min) grid resolution have been simulated at EC-JRC premises for Black Sea and Eastern and Central Mediterranean (30°N-41.5°N and 8°E-37°E) for each source defined using shallow water finite-difference SWAN code (Mader, 2004) for the magnitude range of 6.5 - Mwmax defined for that bin with a Mw increment of 0.1. Results show that not only the earthquakes resembling the well-known historical earthquakes such as AD 365 or AD 1303 in the Hellenic Arc, but also earthquakes with lower magnitudes do constitute to the tsunami hazard in the study area.

Neogene-Recent Reactivation of Cretaceous-age Faults in Southern Vietnam, with Implications for the Himalayan-Tibetan Orogen

NASA Astrophysics Data System (ADS)

Burberry, C. M.; Elkins, L. J.; Hoang, N.; Anh, L. D.; Dinh, S. Q.

2017-12-01

The tectonic activity and ongoing diffuse volcanic activity of the Central Highlands of Vietnam have, to date, been challenging to explain using accepted plate tectonics principles. The various hypotheses invoked to explain the voluminous magmatism include extrusion related to the Himalayan-Tibetan orogen, extension related to the South China Sea, and plume activity beneath Hainan. We present a combined remote sensing and field study, focused on fault orientation and age relative to lava flows in order to discriminate between these models. Landsat ETM+ and SPOT data were processed to highlight variations in lithology and to remove vegetation, and lineaments were interpreted from these images. The lineament data were compared to existing geologic maps, and to regions of known flow age. Key locations were visited in the field, where fault orientations and relative age were recorded. At many locations, the slip direction could be measured using trend and plunge of mineral lineations. The remote data reveal a complex pattern of lineaments, with prominent N-S, NE-SW and NW-SE directions. Lineaments are observed to cut lava flows with ages of 2.2+/- 0.1 Ma and younger. In the field, NE-SW oriented faults were identified in Jurassic-Cretaceous sedimentary rocks with two phases of movement; a dip-slip phase and a younger, dominantly strike-slip phase. Strike-slip faults were identified in lava flows of approx. 3.2 Ma, also oriented NE-SW. These results indicate that there has been fault activity since the Pliocene, and that this fault activity includes reactivation of dip-slip faults as strike-slip. This is consistent with the movement vector of the southern Indochina Block SE with respect to the Sunda block, and with microplate rotation due to asthenospheric extrusion. These results therefore suggest that ongoing Himalayan-Tibetan collision is still being accommodated, in part, by active lithospheric extrusion of the Indo-China block.

Surface Rupture Characteristics and Rupture Mechanics of the Yushu Earthquake (Ms7.1), 14/04/2010

NASA Astrophysics Data System (ADS)

Pan, J.; Li, H.; Xu, Z.; Li, N.; Wu, F.; Guo, R.; Zhang, W.

2010-12-01

On April 14th 2010, a disastrous earthquake (Ms 7.1) struck Yushu County, Qinghai Province, China, killing thousands of people. This earthquake occurred as a result of sinistral strike-slip faulting on the western segment of the Xianshuihe Fault zone in eastern Tibetan Plateau. Our group conducted scientific investigation in the field on co-seismic surface rupture and active tectonics in the epicenter area immediately after the earthquake. Here, we introduce our preliminary results on the surface ruptures and rupture mechanics of the Yushu Earthquake. The surface rupture zone of Yushu earthquake, which is about 49 km-long, consists of 3 discontinuous left stepping rupture segments, which are 19 km, 22 km, and about 8 km, respectively, from west to east. Each segment consists of a series of right stepping en-echelon branch ruptures. The branch ruptures consist of interphase push-up and tension fissures or simply en-echelon tension fissures. The co-seismic displacements had been surveyed with a total station in detail on landmarks such as rivers, gullies, roads, farmlands, wire poles, and fences. The maximum offset measured is 2.3m, located near the Guoyangyansongduo Village. There are 3 offset peaks along the rupture zone corresponding to the 3 segments of the surface rupture zone. The maximum offsets in the west, central, and east segment rupture zones are 1.4m, 2.3m, and 1.6m respectively. The surface rupture zone of Yushu earthquake strikes in a 310°NW direction. The fault plane dips to the northeast and the dip angle is about 81°. The rupture zone is developed in transtension setting. Tension normal fault developed during the sinistral strike-slip process of the fault. The valley west of Yushu City and the Longbao Lake are both pull-apart basins formed during the transtension activity of the fault.

Source model and Coulomb stress change of 2017 Mw 6.5 Philippine (Ormoc) Earthquake revealed by SAR interferometry

NASA Astrophysics Data System (ADS)

Tsai, M. C.; Hu, J. C.; Yang, Y. H.; Hashimoto, M.; Aurelio, M.; Su, Z.; Escudero, J. A.

2017-12-01

Multi-sight and high spatial resolution interferometric SAR data enhances our ability for mapping detailed coseismic deformation to estimate fault rupture model and to infer the Coulomb stress change associated with a big earthquake. Here, we use multi-sight coseismic interferograms acquired by ALOS-2 and Sentinel-1A satellites to estimate the fault geometry and slip distribution on the fault plane of the 2017 Mw 6.5 Ormoc Earthquake in Leyte island of Philippine. The best fitting model predicts that the coseismic rupture occurs along a fault plane with strike of 325.8º and dip of 78.5ºE. This model infers that the rupture of 2017 Ormoc earthquake is dominated by left-lateral slip with minor dip-slip motion, consistent with the left-lateral strike-slip Philippine fault system. The fault tip has propagated to the ground surface, and the predicted coseismic slip on the surface is about 1 m located at 6.5 km Northeast of Kananga city. Significant slip is concentrated on the fault patches at depth of 0-8 km and an along-strike distance of 20 km with varying slip magnitude from 0.3 m to 2.3 m along the southwest segment of this seismogenic fault. Two minor coseismic fault patches are predicted underneath of the Tononan geothermal field and the creeping segment of the northwest portion of this seismogenic fault. This implies that the high geothermal gradient underneath of the Tongonan geothermal filed could prevent heated rock mass from the coseismic failure. The seismic moment release of our preferred fault model is 7.78×1018 Nm, equivalent to Mw 6.6 event. The Coulomb failure stress (CFS) calculated by the preferred fault model predicts significant positive CFS change on the northwest segment of the Philippine fault in Leyte Island which has coseismic slip deficit and is absent from aftershocks. Consequently, this segment should be considered to have increasing of risk for future seismic hazard.

Episodic Rifting Events Within the Tjörnes Fracture Zone, an Onshore-Offshore Ridge-Transform in N-Iceland

NASA Astrophysics Data System (ADS)

Brandsdottir, B.; Magnusdottir, S.; Karson, J. A.; Detrick, R. S.; Driscoll, N. W.

2015-12-01

The multi-branched plate boundary across Iceland is made up of divergent and oblique rifts, and transform zones, characterized by entwined extensional and transform tectonics. The Tjörnes Fracture Zone (TFZ), located on the coast and offshore Northern Iceland, is a complex transform linking the northern rift zone (NVZ) on land with the Kolbeinsey Ridge offshore. Extension across TFZ is partitioned across three N-S trending rift basins; Eyjafjarðaráll, Skjálfandadjúp (SB) and Öxarfjörður and three WNW-NW oriented seismic lineaments; the Grímsey Oblique Rift, Húsavík-Flatey Faults (HFFs) and Dalvík Lineament. We compile the tectonic framework of the TFZ ridge-transform from aerial photos, satellite images, multibeam bathymetry and high-resolution seismic reflection data (Chirp). The rift basins are made up of normal faults with vertical displacements of up to 50-60 m, and post-glacial sediments of variable thickness. The SB comprises N5°W obliquely trending, eastward dipping normal faults as well as N10°E striking, westward dipping faults oriented roughly perpendicular to the N104°E spreading direction, indicative of early stages of rifting. Correlation of Chirp reflection data and tephrachronology from a sediment core within SB reveal major rifting episodes between 10-12.1 kyrs BP activating the whole basin, followed by smaller-scale fault movements throughout Holocene. Onshore faults have the same orientations as those mapped offshore and provide a basis for the interpretation of the kinematics of the faults throughout the region. These include transform parallel right-lateral, strike-slip faults separating domains dominated by spreading parallel left-lateral bookshelf faults. Shearing is most prominent along the HFFs, a system of right-lateral strike-slip faults with vertical displacement up to 15 m. Vertical fault movements reflect increased tectonic activity during early postglacial time coinciding with isostatic rebound enhancing volcanism within Iceland.

Determination of source process and the tsunami simulation of the 2013 Santa Cruz earthquake

NASA Astrophysics Data System (ADS)

Park, S. C.; Lee, J. W.; Park, E.; Kim, S.

2014-12-01

In order to understand the characteristics of large tsunamigenic earthquakes, we analyzed the earthquake source process of the 2013 Santa Cruz earthquake and simulated the following tsunami. We first estimated the fault length of about 200 km using 3-day aftershock distribution and the source duration of about 110 seconds using the duration of high-frequency energy radiation (Hara, 2007). Moment magnitude was estimated to be 8.0 using the formula of Hara (2007). From the results of 200 km of fault length and 110 seconds of source duration, we used the initial value of rupture velocity as 1.8 km/s for teleseismic waveform inversions. Teleseismic body wave inversion was carried out using the inversion package by Kikuchi and Kanamori (1991). Teleseismic P waveform data from 14 stations were used and band-pass filter of 0.005 ~ 1 Hz was applied. Our best-fit solution indicated that the earthquake occurred on the northwesterly striking (strike = 305) and shallowly dipping (dip = 13) fault plane. Focal depth was determined to be 23 km indicating shallow event. Moment magnitude of 7.8 was obtained showing somewhat smaller than the result obtained above and that of previous study (Lay et al., 2013). Large slip area was seen around the hypocenter. Using the slip distribution obtained by teleseismic waveform inversion, we calculated the surface deformations using formulas of Okada (1985) assuming as the initial change of sea water by tsunami. Then tsunami simulation was carred out using Conell Multi-grid Coupled Tsunami Model (COMCOT) code and 1 min-grid topographic data for water depth from the General Bathymetric Chart of the Ocenas (GEBCO). According to the tsunami simulation, most of tsunami waves propagated to the directions of southwest and northeast which are perpendicular to the fault strike. DART buoy data were used to verify our simulation. In the presentation, we will discuss more details on the results of source process and tsunami simulation and compare them with the previous study.

Pre-Flight Ground Testing of the Full-Scale HIFiRE-1 at Fully Duplicated Flight Conditions

DTIC Science & Technology

2008-05-14

survey rake installed in the test section to measure X ... -------- pitot pressure, static pressure and stagnation point heat transfer in . the...equilibrium at Figure 17. Photograph of Pitot Rake Assembly all points. This is a safe assumption, as the pressures and Mounted Inside Test Section of...measurement technique in supersonic and hypersonic test facilities, and the small size of the sensing element coupled with the insulating substrate

The AFFDL-Nielsen Flow-Field Study

DTIC Science & Technology

1976-04-01

76-18 1.0 INTRODUCTION This investigation was conducted in the von K ~ n Gas Dynamics Facility (VKF) Supersonic Wind Tunnel (A) for Nielsen...flow field-surveys, using a cone probe rake to determine the local velocity field; (2) pressure distributions on a store model; and (3) force and...moment data on a store model. In addition, free-stream (interference-free) data were obtained with the probe rake and on the force and pressure store

A flammability study of thin plastic film materials

NASA Technical Reports Server (NTRS)

Skinner, S. Ballou

1990-01-01

The Materials Science Laboratory at the Kennedy Space Center presently conducts flammability tests on thin plastic film materials by using a small needle rake method. Flammability data from twenty-two thin plastic film materials were obtained and cross-checked by using three different testing methods: (1) the presently used small needle rake; (2) the newly developed large needle rake; and (3) the previously used frame. In order to better discern the melting-burning phenomenon of thin plastic film material, five additional specific experiments were performed. These experiments determined the following: (1) the heat sink effect of each testing method; (2) the effect of the burn angle on the burn length or melting/shrinkage length; (3) the temperature profile above the ignition source; (4) the melting point and the fire point of each material; and (5) the melting/burning profile of each material via infrared (IR) imaging. The results of these experimentations are presented.

F-16XL ship #1 - CAWAP boundary layer rakes and hot film on left wing

NASA Technical Reports Server (NTRS)

1996-01-01

This photo shows the boundary layer hot film and the boundary layer rakes on the left wing of NASA's single-seat F-16XL (ship #1) used for the Cranked-Arrow Wing Aerodynamic Project (CAWAP) at Dryden Flight Research Center, Edwards, California. The modified airplane features a delta 'cranked-arrow' wing with strips of tubing along the leading edge to the trailing edge to sense static on the wing and obtain pressure distribution data. The right wing receives data on pressure distribution and the left wing has three types of instrumentation - preston tubes to measure local skin friction, boundary layer rakes to measure boundary layer profiles (the layer where the air interacts with the surfaces of a moving aircraft), and hot films to determine boundary layer transition locations. The first flight of CAWAP occurred on November 21, 1995, and the test program ended in April 1996.

F-16XL ship #1 - CAWAP outboard rake #7

NASA Technical Reports Server (NTRS)

1996-01-01

This photo shows the #7 outboard rake on the left wing of NASA's single-seat F-16XL (ship #1) used for the Cranked-Arrow Wing Aerodynamic Project (CAWAP) at Dryden Flight Research Center, Edwards, California. The modified airplane features a delta 'cranked-arrow' wing with strips of tubing along the leading edge to the trailing edge to sense static on the wing and obtain pressure distribution data. The right wing receives data on pressure distribution and the left wing has three types of instrumentation - preston tubes to measure local skin friction, boundary layer rakes to measure boundary layer profiles (the layer where the air interacts with the surfaces of a moving aircraft), and hot films to determine boundary layer transition locations. The program also gathered aero data on two wing planforms for NASA's High Speed Research Program. The first flight of CAWAP occurred on November 21, 1995, and the test program ended in April 1996.

Effect of number of probes and their orientation on the calculation of several compressor face distortion descriptors

NASA Technical Reports Server (NTRS)

Stoll, F.; Tremback, J. W.; Arnaiz, H. H.

1979-01-01

A study was performed to determine the effects of the number and position of total pressure probes on the calculation of five compressor face distortion descriptors. This study used three sets of 320 steady state total pressure measurements that were obtained with a special rotating rake apparatus in wind tunnel tests of a mixed-compression inlet. The inlet was a one third scale model of the inlet on a YF-12 airplane, and it was tested in the wind tunnel at representative flight conditions at Mach numbers above 2.0. The study shows that large errors resulted in the calculation of the distortion descriptors even with a number of probes that were considered adequate in the past. There were errors as large as 30 and -50 percent in several distortion descriptors for a configuration consisting of eight rakes with five equal-area-weighted probes on each rake.

Character and Implications of a Newly Identified Creeping Strand of the San Andreas fault NE of Salton Sea, Southern California

NASA Astrophysics Data System (ADS)

Janecke, S. U.; Markowski, D.

2015-12-01

The overdue earthquake on the Coachella section, San Andreas fault (SAF), the model ShakeOut earthquake, and the conflict between cross-fault models involving the Extra fault array and mapped shortening in the Durmid Hill area motivate new analyses at the southern SAF tip. Geologic mapping, LiDAR, seismic reflection, magnetic and gravity datasets, and aerial photography confirm the existence of the East Shoreline strand (ESS) of the SAF southwest of the main trace of the SAF. We mapped the 15 km long ESS, in a band northeast side of the Salton Sea. Other data suggest that the ESS continues N to the latitude of the Mecca Hills, and is >35 km long. The ESS cuts and folds upper Holocene beds and appears to creep, based on discovery of large NW-striking cracks in modern beach deposits. The two traces of the SAF are parallel and ~0.5 to ~2.5 km apart. Groups of east, SE, and ENE-striking strike-slip cross-faults connect the master dextral faults of the SAF. There are few sinistral-normal faults that could be part of the Extra fault array. The 1-km wide ESS contains short, discontinuous traces of NW-striking dextral-oblique faults. These en-echelon faults bound steeply dipping Pleistocene beds, cut out section, parallel tight NW-trending folds, and produced growth folds. Beds commonly dip toward the ESS on both sides, in accord with persistent NE-SW shortening across the ESS. The dispersed fault-fold structural style of the ESS is due to decollements in faulted mud-rich Pliocene to Holocene sediment and ramps and flats along the strike-slip faults. A sheared ladder-like geometric model of the two master dextral strands of the SAF and their intervening cross-faults, best explains the field relationships and geophysical datasets. Contraction across >40 km2 of the southernmost SAF zone in the Durmid Hills suggest that interaction of active structures in the SAF zone may inhibit the nucleation of large earthquakes in this region. The ESS may cross the northern Coachella Valley to join the blind Palm Spring dextral fault- a source of microearthquakes and differential subsidence. The ESS may also continue north parallel to the margin of the Salton Trough or have both a NW and NE branch. The risk of a future large earthquake directly beneath the greater Palm Springs metropolitan area may be larger if the first or last options are correct.

The role of major rift faults in the evolution of deformation bands in the Rio do Peixe Basin, Brazil

NASA Astrophysics Data System (ADS)

Hilario Bezerra, Francisco; Araujo, Renata; Maciel, Ingrid; Cezar Nogueira, Francisco; Balsamo, Fabrizio; Storti, Fabrizio; Souza, Jorge Andre; Carvalho, Bruno

2017-04-01

Many studies have investigated on the evolution and properties of deformation bands, but their occurrence and relationships with basin-boundary faults remain elusive when the latter form by brittle reactivation of structural inheritance in crystalline basements. The main objective of our study was to systematically record the location, kinematics, geometry, and density of deformation bands in the early Cretaceous Rio do Peixe basin, NE Brazil, and analyze their relationship with major syn-rift fault zones. Reactivation in early Cretaceous times of continental-scale ductile shear zones led to the development of rift basins in NE Brazil. These shear zones form a network of NE- and E-W-trending structures hundreds of kilometers long and 3-10 km wide. They were active in the Brasiliano orogeny at 540-740 Ma. Brittle reactivation of these structures occurred in Neocomian times ( 140-120 Ma) prior the breakup between the South American and African plates in the late Cretaceous. The Rio do Peixe basin formed at the intersection between the NE-SW-striking Portalegre shear zone and the E-W-striking Patos shear zone. The brittle fault systems developed by the shear zone reactivation are the Portalegre Fault and the Malta Fault, respectively. In this research we used field structural investigations and drone imagery with centimetric resolution. Our results indicate that deformation bands occur in poorly sorted, medium to coarse grain size sandstones and localize in 3-4 km wide belts in the hanging wall of the two main syn-rifts fault systems. Deformation bands formed when sandstones were not completely lithified. They strike NE along the Portalegre Fault and E-W along the Malta Fault and have slip lineations with rake values ranging from 40 to 90. The kinematics recorded in deformation bands is consistent with that characterizing major rift fault systems, i.e. major extension with a strike-slip component. Since deformations bands are typical sub-seismic features, our findings can have implications for the prediction of deformation band occurrence in sedimentary basins and their geometric and kinematic relations with major basin-boundary fault systems.

Extensional tectonics and collapse structures in the Suez Rift (Egypt)

NASA Technical Reports Server (NTRS)

Chenet, P. Y.; Colletta, B.; Desforges, G.; Ousset, E.; Zaghloul, E. A.

1985-01-01

The Suez Rift is a 300 km long and 50 to 80 km wide basin which cuts a granitic and metamorphic shield of Precambrian age, covered by sediments of Paleozoic to Paleogene age. The rift structure is dominated by tilted blocks bounded by NW-SE normal faults. The reconstruction of the paleostresses indicates a N 050 extension during the whole stage of rifting. Rifting began 24 My ago with dikes intrusions; main faulting and subsidence occurred during Early Miocene producing a 80 km wide basin (Clysmic Gulf). During Pliocene and Quaternary times, faulting is still active but subsidence is restricted to a narrower area (Present Gulf). On the Eastern margin of the gulf, two sets of fault trends are predominant: (1) N 140 to 150 E faults parallel to the gulf trend with pure dip-slip displacement; and (2) cross faults, oriented NOO to N 30 E that have a strike-slip component consistent with the N 050 E distensive stress regime. The mean dip cross fault is steeper (70 to 80 deg) than the dip of the faults parallel to the Gulf (30 to 70 deg). These two sets of fault define diamond shaped tilted block. The difference of mechanical behavior between the basement rocks and the overlying sedimentary cover caused structural disharmony and distinct fault geometries.

Geologic map of the Paintbrush Canyon Area, Yucca Mountain, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dickerson, R.P.; Drake, R.M. II

This geologic map is produced to support site characterization studies of Yucca Mountain, Nevada, site of a potential nuclear waste storage facility. The area encompassed by this map lies between Yucca Wash and Fortymile Canyon, northeast of Yucca Mountain. It is on the southern flank of the Timber Mountain caldera complex within the southwest Nevada volcanic field. Miocene tuffs and lavas of the Calico Hills Formation, the Paintbrush Group, and the Timber Mountain Group crop out in the area of this map. The source vents of the tuff cones and lava domes commonly are located beneath the thickest deposits ofmore » pyroclastic ejecta and lava flows. The rocks within the mapped area have been deformed by north- and northwest-striking, dominantly west-dipping normal faults and a few east-dipping normal faults. Faults commonly are characterized by well developed fault scarps, thick breccia zones, and hanging-wall grabens. Latest movement as preserved by slickensides on west-dipping fault scarps is oblique down towards the southwest. Two of these faults, the Paintbrush Canyon fault and the Bow Ridge fault, are major block-bounding faults here and to the south at Yucca Mountain. Offset of stratigraphic units across faults indicates that faulting occurred throughout the time these volcanic units were deposited.« less

Investigation of Shock Diffusers at Mach Number 1.85. 2 - Projecting Double-Shock Cones

DTIC Science & Technology

1947-06-17

pitot - static rake located as shown in figure 1(a). Total-pressure recoveries were measured for a series of tip projections varied in minimum steps...is shown. The position of the pitot -static rake with which these distributions were .measured is shown in figure 1(a). The data points correspond...Schroeder SUMMARY An Investigation has "been undertaken in the Cleveland 18- by 18-Inch, supersonic tunnel to determine the total-pressure

Investigation of Shock Diffusers at Mach Number 1.85. 1 - Projecting Single Shock Cones

DTIC Science & Technology

1947-06-17

cylindrical simulated combustion chamber was used to vary the outlet area of the flow through the diffuser. The pitot -static rake , located as shown in the...Simulated combustion u chamber A 90° W •—Conical damper S Static-pressure orifice ps pitot -static "" rake ’ NATIONAL ADVISORY...recoveries were obtained with subsonic entrance flow. INTRODCJCTION For efficient conversion of the kinetic energy of a supersonic air stream into ram

Comparison of wind tunnel and flight test afterbody and nozzle pressures for a twin-jet fighter aircraft at transonic speeds

NASA Technical Reports Server (NTRS)

Nugent, Jack; Pendergraft, Odis C., Jr.

1987-01-01

Afterbody and nozzle pressures measured on a 1/12-scale model and in flight on a twin-jet fighter aircraft were compared as Mach number varied from 0.6 to 1.2, Reynolds number from 17.5 million to 302.5 million, and angle of attack from 1 to 7 deg. At Mach 0.6 and 0.8, nozzle pressure coefficient distributions and nozzle axial force coefficients agreed and showed good recompression. At Mach 0.9 and 1.2, flow complexity caused a loss in recompression for both flight and wind tunnel nozzle data. The flight data exhibited less negative values of pressure coefficient and lower axial force coefficients than did the wind tunnel data. Reynolds number effects were noted only at these Mach numbers. Jet temperature and mass flux ratio did not affect the comparisons of nozzle axial flow coefficient. At subsonic speeds, the levels of pressure coefficient distributions on the upper fuselage and lower nacelle surfaces for flight were less negative than those for the model. The model boundary layer thickness at the aft rake station exceeded that for the forward rake station and increased with increasing angle of attack. The flight boundary layer thickness at the aft rake station was less than that for the forward rake station and decreased with increasing angle of attack.

Geochronology and Structural Studies in the Northern Ritter Range: Implications for the Tectonic History of Mesozoic Sierra Nevada Arc

NASA Astrophysics Data System (ADS)

Black, C. J.; Whitesides, A. S.; Anderson, J. L.; Culbert, K. N.; Vandeveer, M.; Cox, I. V.; Cardamone, J.; Torrez, G.; Quirk, M.; Memeti, V.; Cao, W.; Paterson, S. R.

2010-12-01

Field mapping in the Northern Ritter Range pendant, central Sierra Nevada reveals four different lithotectonic units. Unit 1, east of Gem Lake, consists of Paleozoic passive margin metasedimentary rocks. Unit 2 lies unconformably above and west and is composed of Late Triassic to Middle Jurassic rhyolitic to andesitic, clast-rich, metavolcanic rocks that are typically massive, thick bedded, relatively homogeneous. Breccias and millimeter sized plagioclase phenocrysts are common in these beds. Unit 3 west of and structurally higher than unit 2 and is composed of thinly bedded metavolcanic and metasedimentary rocks of same age. Unit 2 and Unit 3 both steeply dipping and NW striking bedding and bedding parallel foliations. Unit 4 is composed of less deformed, Cretaceous, rhyolitic to andesitic breccias and rare volcaniclastic units that are west of and unconformably above unit 3. All units are now separated by faults. The Cretaceous dextral, oblique Gem Lake shear zone reactivated the uncomformity between units 1 and 2. West of the shear zone, both the shearing and strain intensity gradually decrease, the later from >60% to 40% shortening. Unit 2 and 3 are separated by a thrust fault, with local pseudotachelite now overprinted by ductile deformation. Unit 3 and 4 are now juxtaposed along a deformed unconformity west of which strain decreases to shortening values > 30%. These host rocks are intruded by granitic to dioritic plutons preserving a wide range of internal characteristics and emplacement styles. The oldest pluton is the 100 Ma Rush Creek Granodiorite, which intruded into unit 2. The Kuna Crest (KC, 94.6 Ma), the Waugh Lake (WL, 93.6 Ma), and the Thousand Island Lake leucogranodiorites (TIL) (~94 Ma) all intrude into the unit 3. The TIL cut the unconformity between units 3 and 4. The WL pluton is possibly cut by movement between units 2 and 3. The typically NW striking steeply dipping bedding in host rock units is dramatically deflected to EW orientations along the SW margin of the KC lobe. Within the nearby WL Granodiorite, hundreds of andesitic host rock blocks, some up to hundred meter lengths suggest that stoping was an important emplacement process. Migmatitic zones occur along several pluton margins. Our observations are consistent with aspects of the Tobisch et al. (2000) paper suggesting early brittle thrusting led to rotation of beds to steep dips. However our results indicate that beds were already at near vertical dips prior to ductile shortening and well before pluton emplacement. And although regional downward flow of extrusive volcanics has certainly occurred we see evidence against previous suggestions that this downward flow was localized in pluton aureoles as plutons typically cut discordantly across already steeply dipping beds and in turn are deformed by the younger ductile deformation. Although ductile shortening may play a minor role in rotation of beds, much of the ductile deformation had to occur after beds were steeply dipping as the 100-93.5 m.y. plutons have fabrics that are continuous with ductile deformation in the host rocks.

Pedagogy of stereographic projection

NASA Astrophysics Data System (ADS)

Blenkinsop, Tom

1999-05-01

Three sorts of problem are encountered by students learning stereographic projection. Lack of familiarity with compass directions and with the specification of planar and linear orientations is the most fundamental problem. The second problem is one of poor visualisation which prohibits the correct understanding of the principles and practice of projection, although students can sometimes perform remarkably well on certain exercises without this understanding. A third problem is a lack of interest or appreciation of the usefulness of the technique. A solution to the first problem is to provide a thorough grounding in compass directions, and concepts of strike, dip, dip direction, plunge and plunge bearing immediately before teaching stereographic projection. Visual aids, such as a transparent hemisphere to represent half of the projection sphere, and a large stereonet, are helpful for visualisation. Estimation and sketching exercises help to develop an understanding of the geometry of projection. Computer-aided teaching and plotting is recommended after an introduction to manual techniques. Interest can be stimulated through the use of exercises based on real geological maps.

Continuous track paths reveal additive evidence integration in multistep decision making.

PubMed

Buc Calderon, Cristian; Dewulf, Myrtille; Gevers, Wim; Verguts, Tom

2017-10-03

Multistep decision making pervades daily life, but its underlying mechanisms remain obscure. We distinguish four prominent models of multistep decision making, namely serial stage, hierarchical evidence integration, hierarchical leaky competing accumulation (HLCA), and probabilistic evidence integration (PEI). To empirically disentangle these models, we design a two-step reward-based decision paradigm and implement it in a reaching task experiment. In a first step, participants choose between two potential upcoming choices, each associated with two rewards. In a second step, participants choose between the two rewards selected in the first step. Strikingly, as predicted by the HLCA and PEI models, the first-step decision dynamics were initially biased toward the choice representing the highest sum/mean before being redirected toward the choice representing the maximal reward (i.e., initial dip). Only HLCA and PEI predicted this initial dip, suggesting that first-step decision dynamics depend on additive integration of competing second-step choices. Our data suggest that potential future outcomes are progressively unraveled during multistep decision making.

Constraining central Neo-Tethys Ocean reconstructions with mantle convection models

NASA Astrophysics Data System (ADS)

Nerlich, Rainer; Colli, Lorenzo; Ghelichkhan, Siavash; Schuberth, Bernhard; Bunge, Hans-Peter

2017-04-01

A striking feature of the Indian Ocean is a distinct geoid low south of India, pointing to a regionally anomalous mantle density structure. Equally prominent are rapid plate convergence rate variations between India and SE Asia, particularly in Late Cretaceous/Paleocene times. Both observations are linked to the central Neo-Tethys Ocean subduction history, for which competing scenarios have been proposed. Here we evaluate three alternative reconstructions by assimilating their associated time-dependent velocity fields in global high-resolution geodynamic Earth models, allowing us to predict the resulting seismic mantle heterogeneity and geoid signal. Our analysis reveals that a geoid low similar to the one observed develops naturally when a long-lived back-arc basin south of Eurasia's paleomargin is assumed. A quantitative comparison to seismic tomography further supports this model. In contrast, reconstructions assuming a single northward dipping subduction zone along Eurasia's margin or models incorporating a temporary southward dipping intraoceanic subduction zone cannot sufficiently reproduce geoid and seismic observations.

Constraining central Neo-Tethys Ocean reconstructions with mantle convection models

NASA Astrophysics Data System (ADS)

Nerlich, Rainer; Colli, Lorenzo; Ghelichkhan, Siavash; Schuberth, Bernhard; Bunge, Hans-Peter

2016-09-01

A striking feature of the Indian Ocean is a distinct geoid low south of India, pointing to a regionally anomalous mantle density structure. Equally prominent are rapid plate convergence rate variations between India and SE Asia, particularly in Late Cretaceous/Paleocene times. Both observations are linked to the central Neo-Tethys Ocean subduction history, for which competing scenarios have been proposed. Here we evaluate three alternative reconstructions by assimilating their associated time-dependent velocity fields in global high-resolution geodynamic Earth models, allowing us to predict the resulting seismic mantle heterogeneity and geoid signal. Our analysis reveals that a geoid low similar to the one observed develops naturally when a long-lived back-arc basin south of Eurasia's paleomargin is assumed. A quantitative comparison to seismic tomography further supports this model. In contrast, reconstructions assuming a single northward dipping subduction zone along Eurasia's margin or models incorporating a temporary southward dipping intraoceanic subduction zone cannot sufficiently reproduce geoid and seismic observations.

Collapse and Earthquake Swarm After North Korea's 3 September 2017 Nuclear Test

NASA Astrophysics Data System (ADS)

Tian, Dongdong; Yao, Jiayuan; Wen, Lianxing

2018-05-01

North Korea's 3 September 2017 nuclear test was followed by several small seismic events, with one eight-and-a-half minutes after the test and three on and after 23 September 2017. Seismic analysis reveals that the first event is a near vertical on-site collapse toward the nuclear test center from 440 ± 260 m northwest of the test site, with its seismic source best represented by a single force with a dip angle of 70°-75° and an azimuth of 150°, and the later events are an earthquake swarm located 8.4 ± 1.7 km north of the test site within a region of 520 m, with a focal depth of at least 2.4 km and a focal mechanism of nearly pure strike slip along the north-south direction with a high dip angle of 50°-90°. The occurrence of the on-site collapse calls for continued monitoring of any leaks of radioactive materials from the test site.

Transpressional Tectonics across the N. American-Caribbean Plate Boundary: Preliminary Results of a Multichannel Seismic Survey of Lake Azuei, Haiti.

NASA Astrophysics Data System (ADS)

Hearn, C. K.; Cormier, M. H.; Sloan, H.; Wattrus, N. J.; Boisson, D.; Brown, B.; Guerrier, K.; King, J. W.; Knotts, P.; Momplaisir, R.; Sorlien, C. C.; Stempel, R.; Symithe, S. J.; Ulysse, S. M. J.

2017-12-01

On January 12, 2010, a Mw 7.0 earthquake struck Haiti, killing over 200,000 people and devastating the Capital city of Port-au-Prince and the surrounding regions. It ruptured a previously unknown blind-thrust fault that abuts the Enriquillo Plantain Garden Fault (EPGF), one of two transform faults that define the North American-Caribbean plate boundary. That earthquake highlighted how transpression across this complex boundary is accommodated by slip partitioning into strike-slip and compressional structures. Because the seismic hazard is higher for a rupture on a reverse or oblique-slip fault than on a vertical strike-slip fault, the need to characterize the geometry of that fault system is clear. Lake Azuei overlies this plate boundary 60 km east of the 2010 epicenter. The lake's 23 km long axis trends NW-SE, parallel to the Haitian fold-and-thrust belt and oblique to the EPGF. This tectonic context makes it an ideal target for investigating the partitioning of plate motion between strike-slip and compressional structures. In January 2017, we acquired 222 km of multichannel seismic (MCS) profiles in the lake, largely concurrent with subbottom seismic (CHIRP) profiles. The MCS data were acquired using a high-frequency BubbleGun source and a 75 m-long, 24-channel streamer, achieving a 24 seismic fold with a penetration of 200 m below lakebed. With the goal of resolving tectonic structures in 3-D, survey lines were laid out in a grid with profiles spaced 1.2 km apart. Additional profiles were acquired at the SE end of the lake where most of the tectonic activity is presumably occurring. The co-located CHIRP and MCS profiles document the continuity of tectonic deformation between the surficial sediments and the deeper strata. Preliminary processing suggests that a SW-dipping blind thrust fault, expressed updip as a large monocline fold, may control the western edge of the lake. Gentle, young folds that protrude from the flat lakebed are also imaged with the CHIRP data. No obvious strike-slip faults are revealed in the MCS or CHIRP imagery. This result is consistent with a published analysis of GPS measurements that suggests oblique convergence on a south-dipping reverse fault along the southern shore of the lake.

Active arc-continent collision: Earthquakes, gravity anomalies, and fault kinematics in the Huon-Finisterre collision zone, Papua New Guinea

NASA Astrophysics Data System (ADS)

Abers, Geoffrey A.; McCaffrey, Robert

1994-04-01

The Huon-Finisterre island arc terrane is actively colliding with the north edge of the Australian continent. The collision provides a rare opportunity to study continental accretion while it occurs. We examine the geometry and kinematics of the collision by comparing earthquake source parameters to surface fault geometries and plate motions, and we constrain the forces active in the collision by comparing topographic loads to gravity anomalies. Waveform inversion is used to constrain focal mechanisms for 21 shallow earthquakes that occurred between 1966 and 1992 (seismic moment 1017 to 3 × 1020 N m). Twelve earthquakes show thrust faulting at 22-37 km depth. The largest thrust events are on the north side of the Huon Peninsula and are consistent with slip on the Ramu-Markham thrust fault zone, the northeast dipping thrust fault system that bounds the Huon-Finisterre terrane. Thus much of the terrane's crust but little of its mantle is presently being added to the Australian continent. The large thrust earthquakes also reveal a plausible mechanism for the uplift of Pleistocene coral terraces on the north side of the Huon Peninsula. Bouguer gravity anomalies are too negative to allow simple regional compensation of topography and require large additional downward forces to depress the lower plate beneath the Huon Peninsula. With such forces, plate configurations are found that are consistent with observed gravity and basin geometry. Other earthquakes give evidence of deformation above and below the Ramu-Markham thrust system. Four thrust events, 22-27 km depth directly below the Ramu-Markham fault outcrop, are too deep to be part of a planar Ramu-Markham thrust system and may connect to the north dipping Highlands thrust system farther south. Two large strike-slip faulting earthquakes and their aftershocks, in 1970 and 1987, show faulting within the upper plate of the thrust system. The inferred fault planes show slip vectors parallel to those on nearby thrust faults, and may represent small offsets in the overriding plate. These faults, along with small normal-faulting earthquakes beneath the Huon-Finisterre ranges and a 25° along-strike rotation of slip vectors, demonstrate the presence of along-strike extension of the accreting terrane and along-strike compression of the lower plate.

Spatial variability of shelf sediments in the STRATAFORM natural laboratory, Northern California

USGS Publications Warehouse

Goff, J.A.; Wheatcroft, R.A.; Lee, H.; Drake, D.E.; Swift, D.J.P.; Fan, S.

2002-01-01

The "Correlation Length Experiment", an intensive box coring effort on the Eel River shelf (Northern California) in the summer of 1997, endeavored to characterize the lateral variability of near-surface shelf sediments over scales of meters to kilometers. Coring focused on two sites, K60 and S60, separated by ??? 15 km along the 60 m isobath. The sites are near the sand-to-mud transition, although K60 is sandier owing to its proximity to the Eel River mouth. Nearly 140 cores were collected on dip and strike lines with core intervals from < 10m to 1 km. Measurements on each core included bulk density computed from gamma-ray attenuation, porosity converted from resistivity measurements, and surficial grain size. Grain size was also measured over the full depth range within a select subset of cores. X-radiograph images were also examined. Semi-variograms were computed for strike, dip, and down-hole directions at each site. The sand-to-mud transition exerts a strong influence on all measurements: on average, bulk density increases and porosity decreases with regional increases in mean grain size. Analysis of bulk density measurements indicates very strong contrasts in the sediment variability at K60 and S60. No coherent bedding is seen at K60; in the strike direction, horizontal variability is "white" (fully uncorrelated) from the smallest scales examined (a few meters) to the largest (8 km), with a variance equal to that seen within the cores. In contrast, coherent bedding exists at S60 related to the preservation of the 1995 flood deposit. A correlatable structure is found in the strike direction with a decorrelation distance of ??? 800 m, and can be related to long-wavelength undulations in the topography and/or thickness of the flood layer or overburden. We hypothesize that the high degree of bulk density variability at K60 is a result of more intense physical reworking of the seabed in the sandier environment. Without significant averaging, the resistivity-based porosity measurements are only marginally correlated to gamma-ray-bulk density measurements, and are largely independent of mean grain size. Furthermore, porosity displays a high degree of incoherent variability at both sites. Porosity, with a much smaller sample volume than bulk density, may therefore resolve small-scale biogenic variability which is filtered out in the bulk density measurement. ?? 2002 Elsevier Science Ltd. All rights reserved.

Slip and Dilation Tendency Anlysis of McGinness Hills Geothermal Area

DOE Data Explorer

Faulds, James E.

2013-12-31

Slip and Dilation Tendency in focus areas Critically stressed fault segments have a relatively high likelihood of acting as fluid flow conduits (Sibson, 1994). As such, the tendency of a fault segment to slip (slip tendency; Ts; Morris et al., 1996) or to dilate (dilation tendency; Td; Ferrill et al., 1999) provides an indication of which faults or fault segments within a geothermal system are critically stressed and therefore likely to transmit geothermal fluids. The slip tendency of a surface is defined by the ratio of shear stress to normal stress on that surface: Ts = τ / σn (Morris et al., 1996). Dilation tendency is defined by the stress acting normal to a given surface: Td = (σ1-σn) / (σ1-σ3) (Ferrill et al., 1999). Slip and dilation were calculated using 3DStress (Southwest Research Institute). Slip and dilation tendency are both unitless ratios of the resolved stresses applied to the fault plane by ambient stress conditions. Values range from a maximum of 1, a fault plane ideally oriented to slip or dilate under ambient stress conditions to zero, a fault plane with no potential to slip or dilate. Slip and dilation tendency values were calculated for each fault in the focus study areas at, McGinness Hills, Neal Hot Springs, Patua, Salt Wells, San Emidio, and Tuscarora on fault traces. As dip is not well constrained or unknown for many faults mapped in within these we made these calculations using the dip for each fault that would yield the maximum slip tendency or dilation tendency. As such, these results should be viewed as maximum tendency of each fault to slip or dilate. The resulting along-fault and fault-to-fault variation in slip or dilation potential is a proxy for along fault and fault-to-fault variation in fluid flow conduit potential. Stress Magnitudes and directions Stress field variation within each focus area was approximated based on regional published data and the world stress database (Hickman et al., 2000; Hickman et al., 1998 Robertson-Tait et al., 2004; Hickman and Davatzes, 2010; Davatzes and Hickman, 2006; Blake and Davatzes 2011; Blake and Davatzes, 2012; Moeck et al., 2010; Moos and Ronne, 2010 and Reinecker et al., 2005) as well as local stress information if applicable. For faults within these focus systems we applied either a normal faulting stress regime where the vertical stress (sv) is larger than the maximum horizontal stress (shmax) which is larger than the minimum horizontal stress (sv>shmax>shmin) or strike-slip faulting stress regime where the maximum horizontal stress (shmax) is larger than the vertical stress (sv) which is larger than the minimum horizontal stress (shmax >sv>shmin) depending on the general tectonic province of the system. Based on visual inspection of the limited stress magnitude data in the Great Basin we used magnitudes such that shmin/shmax = .527 and shmin/sv= .46, which are consistent with complete and partial stress field determinations from Desert Peak, Coso, the Fallon area and Dixie valley (Hickman et al., 2000; Hickman et al., 1998 Robertson-Tait et al., 2004; Hickman and Davatzes, 2011; Davatzes and Hickman, 2006; Blake and Davatzes 2011; Blake and Davatzes, 2012). Slip and dilation tendency for the McGinness Hills geothermal field was calculated based on the faults mapped McGinness Hills area (Siler 2012, unpublished). The McGinness Hills area lies in the Basin and Range Province, as such we applied a normal faulting stress regime to the McGinness area faults, with a minimum horizontal stress direction oriented 115, based on inspection of local and regional stress determinations, as explained above. Under these stress conditions north-northeast striking, steeply dipping fault segments have the highest dilation tendency, while north-northeast striking 60° dipping fault segments have the highest tendency to slip. The McGinness Hills geothermal system is characterized by a left-step in a north-northeast striking west-dipping fault system wit...

Constraints on the exploitation of the functional properties of objects in expert tool-using chimpanzees (Pan troglodytes).

PubMed

Povinelli, Daniel J; Frey, Scott H

2016-09-01

Many species exploit immediately apparent dimensions of objects during tool use and manufacture and operate over internal perceptual representations of objects (they move and reorient objects in space, have rules of operation to deform or modify objects, etc). Humans, however, actively test for functionally relevant object properties before such operations begin, even when no previous percepts of a particular object's qualities in the domain have been established. We hypothesize that such prospective diagnostic interventions are a human specialization of cognitive function that has been entirely overlooked in the neuropsychological literature. We presented chimpanzees with visually identical rakes: one was functional for retrieving a food reward; the other was non-functional (its base was spring-loaded). Initially, they learned that only the functional tool could retrieve a distant reward. In test 1, we explored if they would manually test for the rakes' rigidity during tool selection, but before using it. We found no evidence of such behavior. In test 2, we obliged the apes to deform the non-functional tool's base before using it, in order to evaluate whether this would cause them to switch rakes. It did not. Tests 3-6 attempted to focus the apes' attention on the functionally relevant property (rigidity). Although one ape eventually learned to abandon the non-functional rake before using it, she still did not attempt to test the rakes for rigidity prior to use. While these results underscore the ability of chimpanzees to use novel tools, at the same time they point toward a fundamental (and heretofore unexplored) difference in causal reasoning between humans and apes. We propose that this behavioral difference reflects a human specialization in how object properties are represented, which could have contributed significantly to the evolution of our technological culture. We discuss developing a new line of evolutionarily motivated neuropsychological research on action disorders. Copyright © 2016 Elsevier Ltd. All rights reserved.

Modular Rake of Pitot Probes

NASA Technical Reports Server (NTRS)

Dunlap, Timothy A.; Henry, Michael W.; Homyk, Raymond P.

2004-01-01

The figure presents selected views of a modular rake of 17 pitot probes for measuring both transient and steady-state pressures in a supersonic wind tunnel. In addition to pitot tubes visible in the figure, the probe modules contain (1) high-frequency dynamic-pressure transducers connected through wires to remote monitoring circuitry and (2) flow passages that lead to tubes that, in turn, lead to remote steady-state pressure transducers. Prior pitot-probe rakes were fabricated as unitary structures, into which the individual pitot probes were brazed. Repair or replacement of individual probes was difficult, costly, and time-consuming because (1) it was necessary to remove entire rakes in order to unbraze individual malfunctioning probes and (2) the heat of unbrazing a failed probe and of brazing a new probe in place could damage adjacent probes. In contrast, the modules in the present probe are designed to be relatively quickly and easily replaceable with no heating and, in many cases, without need for removal of the entire rake from the wind tunnel. To remove a malfunctioning probe, one first removes a screw-mounted V-cross-section cover that holds the probe and adjacent probes in place. Then one removes a screw-mounted cover plate to gain access to the steady-state pressure tubes and dynamicpressure wires. Next, one disconnects the tube and wires of the affected probe. Finally, one installs a new probe in the reverse of the aforementioned sequence. The wire connections can be made by soldering, but to facilitate removal and installation, they can be made via miniature plugs and sockets. The connections between the probe flow passages and the tubes leading to the remote pressure sensors can be made by use of any of a variety of readily available flexible tubes that can be easily pulled off and slid back on for removal and installation, respectively.

Fault structure and kinematics of the Long Valley Caldera region, California, revealed by high-accuracy earthquake hypocenters and focal mechanism stress inversions

NASA Astrophysics Data System (ADS)

Prejean, Stephanie; Ellsworth, William; Zoback, Mark; Waldhauser, Felix

2002-12-01

We have determined high-resolution hypocenters for 45,000+ earthquakes that occurred between 1980 and 2000 in the Long Valley caldera area using a double-difference earthquake location algorithm and routinely determined arrival times. The locations reveal numerous discrete fault planes in the southern caldera and adjacent Sierra Nevada block (SNB). Intracaldera faults include a series of east/west-striking right-lateral strike-slip faults beneath the caldera's south moat and a series of more northerly striking strike-slip/normal faults beneath the caldera's resurgent dome. Seismicity in the SNB south of the caldera is confined to a crustal block bounded on the west by an east-dipping oblique normal fault and on the east by the Hilton Creek fault. Two NE-striking left-lateral strike-slip faults are responsible for most seismicity within this block. To understand better the stresses driving seismicity, we performed stress inversions using focal mechanisms with 50 or more first motions. This analysis reveals that the least principal stress direction systematically rotates across the studied region, from NE to SW in the caldera's south moat to WNW-ESE in Round Valley, 25 km to the SE. Because WNW-ESE extension is characteristic of the western boundary of the Basin and Range province, caldera area stresses appear to be locally perturbed. This stress perturbation does not seem to result from magma chamber inflation but may be related to the significant (˜20 km) left step in the locus of extension along the Sierra Nevada/Basin and Range province boundary. This implies that regional-scale tectonic processes are driving seismic deformation in the Long Valley caldera.

Fault structure and kinematics of the Long Valley Caldera region, California, revealed by high-accuracy earthquake hypocenters and focal mechanism stress inversions

USGS Publications Warehouse

Prejean, Stephanie; Ellsworth, William L.; Zoback, Mark; Waldhauser, Felix

2002-01-01

We have determined high-resolution hypocenters for 45,000+ earthquakes that occurred between 1980 and 2000 in the Long Valley caldera area using a double-difference earthquake location algorithm and routinely determined arrival times. The locations reveal numerous discrete fault planes in the southern caldera and adjacent Sierra Nevada block (SNB). Intracaldera faults include a series of east/west-striking right-lateral strike-slip faults beneath the caldera's south moat and a series of more northerly striking strike-slip/normal faults beneath the caldera's resurgent dome. Seismicity in the SNB south of the caldera is confined to a crustal block bounded on the west by an east-dipping oblique normal fault and on the east by the Hilton Creek fault. Two NE-striking left-lateral strike-slip faults are responsible for most seismicity within this block. To understand better the stresses driving seismicity, we performed stress inversions using focal mechanisms with 50 or more first motions. This analysis reveals that the least principal stress direction systematically rotates across the studied region, from NE to SW in the caldera's south moat to WNW-ESE in Round Valley, 25 km to the SE. Because WNW-ESE extension is characteristic of the western boundary of the Basin and Range province, caldera area stresses appear to be locally perturbed. This stress perturbation does not seem to result from magma chamber inflation but may be related to the significant (???20 km) left step in the locus of extension along the Sierra Nevada/Basin and Range province boundary. This implies that regional-scale tectonic processes are driving seismic deformation in the Long Valley caldera.

The 2013, Mw 7.7 Balochistan earthquake, energetic strike-slip reactivation of a thrust fault

NASA Astrophysics Data System (ADS)

Avouac, Jean-Philippe; Ayoub, Francois; Wei, Shengji; Ampuero, Jean-Paul; Meng, Lingsen; Leprince, Sebastien; Jolivet, Romain; Duputel, Zacharie; Helmberger, Don

2014-04-01

We analyse the Mw 7.7 Balochistan earthquake of 09/24/2013 based on ground surface deformation measured from sub-pixel correlation of Landsat-8 images, combined with back-projection and finite source modeling of teleseismic waveforms. The earthquake nucleated south of the Chaman strike-slip fault and propagated southwestward along the Hoshab fault at the front of the Kech Band. The rupture was mostly unilateral, propagated at 3 km/s on average and produced a 200 km surface fault trace with purely strike-slip displacement peaking to 10 m and averaging around 6 m. The finite source model shows that slip was maximum near the surface. Although the Hoshab fault is dipping by 45° to the North, in accordance with its origin as a thrust fault within the Makran accretionary prism, slip was nearly purely strike-slip during that earthquake. Large seismic slip on such a non-optimally oriented fault was enhanced possibly due to the influence of the free surface on dynamic stresses or to particular properties of the fault zone allowing for strong dynamic weakening. Strike-slip faulting on thrust fault within the eastern Makran is interpreted as due to eastward extrusion of the accretionary prism as it bulges out over the Indian plate. Portions of the Makran megathrust, some thrust faults in the Kirthar range and strike-slip faults within the Chaman fault system have been brought closer to failure by this earthquake. Aftershocks cluster within the Chaman fault system north of the epicenter, opposite to the direction of rupture propagation. By contrast, few aftershocks were detected in the area of maximum moment release. In this example, aftershocks cannot be used to infer earthquake characteristics.

Complex permeability structure of a fault zone crosscutting a sequence of sandstones and shales and its influence on hydraulic head distribution

NASA Astrophysics Data System (ADS)

Cilona, A.; Aydin, A.; Hazelton, G.

2013-12-01

Characterization of the structural architecture of a 5 km-long, N40°E-striking fault zone provides new insights for the interpretation of hydraulic heads measured across and along the fault. Of interest is the contaminant transport across a portion of the Upper Cretaceous Chatsworth Formation, a 1400 m-thick turbidite sequence of sandstones and shales exposed in the Simi Hills, south California. Local bedding consistently dips about 20° to 30° to NW. Participating hydrogeologists monitor the local groundwater system by means of numerous boreholes used to define the 3D distribution of the groundwater table around the fault. Sixty hydraulic head measurements consistently show differences of 10s of meters, except for a small area. In this presentation, we propose a link between this distribution and the fault zone architecture. Despite an apparent linear morphological trend, the fault is made up of at least three distinct segments named here as northern, central and southern segments. Key aspects of the fault zone architecture have been delineated at two sites. The first is an outcrop of the central segment and the second is a borehole intersecting the northern segment at depth. The first site shows the fault zone juxtaposing sandstones against shales. Here the fault zone consists of a 13 meter-wide fault rock including a highly deformed sliver of sandstone on the northwestern side. In the sandstone, shear offset was resolved along N42°E striking and SE dipping fracture surfaces localized within a 40 cm thick strand. Here the central core of the fault zone is 8 m-wide and contains mostly shale characterized by highly diffuse deformation. It shows a complex texture overprinted by N30°E-striking carbonate veins. At the southeastern edge of the fault zone exposure, a shale unit dipping 50° NW towards the fault zone provides the key information that the shale unit was incorporated into the fault zone in a manner consistent with shale smearing. At the second site, a borehole more than 194 meter-long intersects the fault zone at its bottom. Based on an optical televiewer image supplemented by limited recovered rock cores, a juxtaposition plane (dipping 75° SE) between a fractured sandstone and a highly-deformed shale fault rock has been interpreted as the southeastern boundary of the fault zone. The shale fault rock estimated to be thicker than 4 meters is highly folded and brecciated with locally complex cataclastic texture. The observations and interpretations of the fault architecture presented above suggest that the drop of hydraulic head detected across the fault segments is due primarily to the low-permeability shaly fault rock incorporated into the fault zone by a shale smearing mechanism. Interestingly, at around the step between the northern and the central fault segments, where the fault offset is expected to diminish (no hard link and no significant shaly fault rock), the groundwater levels measured on either sides of the fault zone are more-or-less equal.

Reflection coefficient of qP, qS and SH at a plane boundary between viscoelastic TTI media

NASA Astrophysics Data System (ADS)

Wang, Hongwei; Peng, Suping

2016-01-01

This paper introduces a calculation method for the effective elastic stiffness tensor matrix of the viscous-elastic TTI medium based on the Chapman theory. We then obtain the phase velocity formula and seismic wave polarization formula of the viscous-elastic TTI medium, by solving the Christoffel equation; solve the phase angle of reflection and transmission wave through the numerical method in accordance with the wave slowness ellipsoid; on the basis of this assumption, and assuming that qP, qS and SH waves occurred simultaneously at the viscous-elastic anisotropic interface, establish the sixth-order Zoeppritz equation in accordance with the boundary conditions; establish the models for the upper and lower media which are viscous-elastic HTI, TTI, etc., on the basis of the sixth-order Zoeppritz equation; and study the impact of fracture dip angle, azimuth angle and frequency on the reflection coefficient. From this we obtain the following conclusions: the reflection coefficient can identify the fracture strike and dip when any information pertaining to the media is unknown; dispersion phenomenon is obvious on the axial plane of symmetry and weakened in the plane vertical to the axial plane of symmetry; the vertical-incidence longitudinal wave can stimulate the qS wave when the dip angle is not 0° or 90° under the condition of coincidence between the symmetry planes of the upper and lower media; when the symmetry planes of the upper and lower media do not coincide and the dip angle is not 0° or 90°, then the vertical-incidence qP will stimulate the qS and SH waves at the same time; the dip angle can cause the reflection coefficient curve to have a more obvious dispersion phenomenon, while the included angle between the symmetry planes of the upper and lower media will weaken the dispersion except SH; and the intercept of reflection coefficient is affected by the fracture dip and included angle between the symmetry planes of the upper and lower media.

Laminar Boundary Layer Stability Measurements at Mach 7 Including Wall Temperature Effects

DTIC Science & Technology

1977-11-01

Diagnostics were done by a four-probe rake bearing a pitot tube, a To probe and two hot films - a boundary layer hot film probe (BLHF) and a freestream hot...tunnel. Inset shows hot film probe close to the surface with second probe positioned higher to sample simultaneously the frcestream turbulence ( pitot ... rake away from the surface by small increments and taking readings at each stop. The readings were simultaneously recorded and reduced by the Tunnel B

Cross-Grain Knife Planing Improves Surface Quality and Utilization of Aspen

Treesearch

Harold A. Stewart

1971-01-01

Aspen at 6 percent moisture content was planed parallel to the grain and across the grain on a cabinet planer with a 25? rake angle, 1/16- and 1/32-inch depth of cut, and 20 knife marks per inch. Aspen was also cross-grain knife planed with a 45? rake angle, 1/32-, 1/16-, and 1/8-inch depths of cut, and 20, 10, 5, and 2.5 knife marks per inch. Cross-grain knife...

Nucleation and growth of strike slip faults in granite.

USGS Publications Warehouse

Segall, P.; Pollard, D.P.

1983-01-01

Fractures within granodiorite of the central Sierra Nevada, California, were studied to elucidate the mechanics of faulting in crystalline rocks, with emphasis on the nucleation of new fault surfaces and their subsequent propagation and growth. Within the study area the fractures form a single, subparallel array which strikes N50o-70oE and dips steeply to the S. Some of these fractures are identified as joints because displacements across the fracture surfaces exhibit dilation but no slip. The joints are filled with undeformed minerals, including epidote and chlorite. Other fractures are identified as small faults because they display left-lateral strike slip separations of up to 2m. Slickensides, developed on fault surfaces, plunge 0o-20o to the E. The faults occur parallel to, and in the same outcrop with, the joints. The faults are filled with epidote, chlorite, and quartz, which exhibit textural evidence of shear deformation. These observations indicate that the strike slip faults nucleated on earlier formed, mineral filled joints. Secondary, dilational fractures propagated from near the ends of some small faults contemporaneously with the left-lateral slip on the faults. These fractures trend 25o+ or -10o from the fault planes, parallel to the direction of inferred local maximum compressive stress. The faults did not propagate into intact rock in their own planes as shear fractures. -from Authors

Chapter B. The Loma Prieta, California, Earthquake of October 17, 1989 - Forecasts

USGS Publications Warehouse

Harris, Ruth A.

1998-01-01

The magnitude (Mw) 6.9 Loma Prieta earthquake struck the San Francisco Bay region of central California at 5:04 p.m. P.d.t. on October 17, 1989, killing 62 people and generating billions of dollars in property damage. Scientists were not surprised by the occurrence of a destructive earthquake in this region and had, in fact, been attempting to forecast the location of the next large earthquake in the San Francisco Bay region for decades. This paper summarizes more than 20 scientifically based forecasts made before the 1989 Loma Prieta earthquake for a large earthquake that might occur in the Loma Prieta area. The forecasts geographically closest to the actual earthquake primarily consisted of right-lateral strike-slip motion on the San Andreas Fault northwest of San Juan Bautista. Several of the forecasts did encompass the magnitude of the actual earthquake, and at least one approximately encompassed the along-strike rupture length. The 1989 Loma Prieta earthquake differed from most of the forecasted events in two ways: (1) it occurred with considerable dip-slip in addition to strike-slip motion, and (2) it was much deeper than expected.

Bend Faulting at the Edge of a Flat Slab: The 2017 Mw7.1 Puebla-Morelos, Mexico Earthquake

NASA Astrophysics Data System (ADS)

Melgar, Diego; Pérez-Campos, Xyoli; Ramirez-Guzman, Leonardo; Spica, Zack; Espíndola, Victor Hugo; Hammond, William C.; Cabral-Cano, Enrique

2018-03-01

We present results of a slip model from joint inversion of strong motion and static Global Positioning System data for the Mw7.1 Puebla-Morelos earthquake. We find that the earthquake nucleates at the bottom of the oceanic crust or within the oceanic mantle with most of the moment release occurring within the oceanic mantle. Given its location at the edge of the flat slab, the earthquake is likely the result of bending stresses occurring at the transition from flat slab subduction to steeply dipping subduction. The event strikes obliquely to the slab, we find a good agreement between the seafloor fabric offshore the source region and the strike of the earthquake. We argue that the event likely reactivated a fault first created during seafloor formation. We hypothesize that large bending-related events at the edge of the flat slab are more likely in areas of low misalignment between the seafloor fabric and the slab strike where reactivation of preexisting structures is favored. This hypothesis predicts decreased likelihood of bending-related events northwest of the 2017 source region but also suggests that they should be more likely southeast of the 2017 source region.

Simulation of aquifer tests and ground-water flowpaths at the local scale in fractured shales and sandstones of the Brunswick Group and Lockatong Formation, Lansdale, Montgomery County, Pennsylvania

USGS Publications Warehouse

Goode, Daniel J.; Senior, Lisa A.

2000-01-01

The U.S. Geological Survey, as part of technical assistance to the U.S. Environmental Protection Agency, has constructed and calibrated models of local-scale ground-water flow in and near Lansdale, Pa., where numerous sources of industrial contamination have been consolidated into the North Penn Area 6 Superfund Site. The local-scale models incorporate hydrogeologic structure of northwest-dipping beds with uniform hydraulic properties identified in previous studies. Computations associated with mapping the dipping-bed structure into the three-dimensional model grid are handled by a preprocessor using a programmed geographic information system (GIS). Hydraulic properties are identified by calibration of the models using measured water levels during pumping and recovery from aquifer tests at three sites. Reduced flow across low-permeability beds is explicitly simulated. The dipping high-permeability beds are extensive in the strike direction but are of limited extent in the dip direction. This model structure yields ground-water-flow patterns characteristic of anisotropic aquifers; preferred flow is in the strike direction. The transmissivities of high-permeability beds in the local-scale models range from 142 to 1,900 ft2/d (feet squared per day) (13 to 177 m2/d). The hydraulic conductivities of low-permeability parts of the aquifer range from 9.6 x 10-4 to 0.26 ft/d (feet per day) (2.9 x 10-4 to 0.079 m/d). Storage coefficients and specific storage are very low, indicating the confined nature of the aquifer system. The calibrated models are used to simulate contributing areas of wells under alternative, hypothetical ground-water-management practices. Predictive contributing areas indicate the general characteristics of ground-water flow towards wells in the Lansdale area. Recharge to wells in Lansdale generally comes from infiltration near the well and over an area that extends upgradient from the well. The contributing areas for two wells pumping at 10 gal/min (gallons per minute) extend about 1,500 ft (feet) upgradient from the wells. The contributing area is more complex at ground-water divides and can extend in more than one direction to capture recharge from more than 3,300 ft away, for pumping at a rate of 30 gal/min. Locally, all recharge in the area of the pumping well is not captured; recharge in the downgradient direction about 150 ft from the pumping well will flow to other discharge locations.

Viscoelastic Earthquake Cycle Simulation with Memory Variable Method

NASA Astrophysics Data System (ADS)

Hirahara, K.; Ohtani, M.

2017-12-01

There have so far been no EQ (earthquake) cycle simulations, based on RSF (rate and state friction) laws, in viscoelastic media, except for Kato (2002), who simulated cycles on a 2-D vertical strike-slip fault, and showed nearly the same cycles as those in elastic cases. The viscoelasticity could, however, give more effects on large dip-slip EQ cycles. In a boundary element approach, stress is calculated using a hereditary integral of stress relaxation function and slip deficit rate, where we need the past slip rates, leading to huge computational costs. This is a cause for almost no simulations in viscoelastic media. We have investigated the memory variable method utilized in numerical computation of wave propagation in dissipative media (e.g., Moczo and Kristek, 2005). In this method, introducing memory variables satisfying 1st order differential equations, we need no hereditary integrals in stress calculation and the computational costs are the same order of those in elastic cases. Further, Hirahara et al. (2012) developed the iterative memory variable method, referring to Taylor et al. (1970), in EQ cycle simulations in linear viscoelastic media. In this presentation, first, we introduce our method in EQ cycle simulations and show the effect of the linear viscoelasticity on stick-slip cycles in a 1-DOF block-SLS (standard linear solid) model, where the elastic spring of the traditional block-spring model is replaced by SLS element and we pull, in a constant rate, the block obeying RSF law. In this model, the memory variable stands for the displacement of the dash-pot in SLS element. The use of smaller viscosity reduces the recurrence time to a minimum value. The smaller viscosity means the smaller relaxation time, which makes the stress recovery quicker, leading to the smaller recurrence time. Second, we show EQ cycles on a 2-D dip-slip fault with the dip angel of 20 degrees in an elastic layer with thickness of 40 km overriding a Maxwell viscoelastic half layer with the relaxation time of 5 yrs. In a test model where we set the fault at 30-40 km depths, the recurrence time of the EQ cycle is reduced by 1 yr from 27.92 in elastic case to 26.85 yrs. This smaller recurrence time is the same as in Kato (2002), but the effect of the viscoelasticity on the cycles would be larger in the dip-slip fault case than that in the strike-slip one.

Aftershocks of the june 20, 1978, Greece earthquake: A multimode faulting sequence

USGS Publications Warehouse

Carver, D.; Bollinger, G.A.

1981-01-01

A 10-station portable seismograph network was deployed in northern Greece to study aftershocks of the magnitude (mb) 6.4 earthquake of June 20, 1978. The main shock occurred (in a graben) about 25 km northeast of the city of Thessaloniki and caused an east-west zone of surface rupturing 14 km long that splayed to 7 km wide at the west end. The hypocenters for 116 aftershocks in the magnitude range from 2.5 to 4.5 were determined. The epicenters for these events cover an area 30 km (east-west) by 18 km (north-south), and focal depths ranges from 4 to 12 km. Most of the aftershocks in the east half of the aftershock zone are north of the surface rupture and north of the graben. Those in the west half are located within the boundaries of the graben. Composite focalmechanism solutions for selected aftershocks indicate reactivation of geologically mapped normal faults in the area. Also, strike-slip and dip-slip faults that splay off the western end of the zone of surface ruptures may have been activated. The epicenters for four large (M ??? 4.8) foreshocks and the main shock were relocated using the method of joint epicenter determination. Collectively, those five epicenters form an arcuate pattern convex southward, that is north of and 5 km distant from the surface rupturing. The 5-km separation, along with a focal depth of 8 km (average aftershock depth) or 16 km (NEIS main-shock depth), implies that the fault plane dips northward 58?? or 73??, respectively. A preferred nodal-plane dip of 36?? was determined by B.C. Papazachos and his colleagues in 1979 from a focal-mechanism solution for the main shock. If this dip is valid for the causal fault and that fault projects to the zone of surface rupturing, a decrease of dip with depth is required. ?? 1981.

Depth varying rupture properties during the 2015 Mw 7.8 Gorkha (Nepal) earthquake

NASA Astrophysics Data System (ADS)

Yue, Han; Simons, Mark; Duputel, Zacharie; Jiang, Junle; Fielding, Eric; Liang, Cunren; Owen, Susan; Moore, Angelyn; Riel, Bryan; Ampuero, Jean Paul; Samsonov, Sergey V.

2017-09-01

On April 25th 2015, the Mw 7.8 Gorkha (Nepal) earthquake ruptured a portion of the Main Himalayan Thrust underlying Kathmandu and surrounding regions. We develop kinematic slip models of the Gorkha earthquake using both a regularized multi-time-window (MTW) approach and an unsmoothed Bayesian formulation, constrained by static and high rate GPS observations, synthetic aperture radar (SAR) offset images, interferometric SAR (InSAR), and teleseismic body wave records. These models indicate that Kathmandu is located near the updip limit of fault slip and approximately 20 km south of the centroid of fault slip. Fault slip propagated unilaterally along-strike in an ESE direction for approximately 140 km with a 60 km cross-strike extent. The deeper portions of the fault are characterized by a larger ratio of high frequency (0.03-0.2 Hz) to low frequency slip than the shallower portions. From both the MTW and Bayesian results, we can resolve depth variations in slip characteristics, with higher slip roughness, higher rupture velocity, longer rise time and higher complexity of subfault source time functions in the deeper extents of the rupture. The depth varying nature of rupture characteristics suggests that the up-dip portions are characterized by relatively continuous rupture, while the down-dip portions may be better characterized by a cascaded rupture. The rupture behavior and the tectonic setting indicate that the earthquake may have ruptured both fully seismically locked and a deeper transitional portions of the collision interface, analogous to what has been seen in major subduction zone earthquakes.

Viscoelastic-cycle model of interseismic deformation in the northwestern United States

USGS Publications Warehouse

Pollitz, F.F.; McCrory, Patricia; Wilson, Doug; Svarc, Jerry; Puskas, Christine; Smith, Robert B.

2010-01-01

We apply a viscoelastic cycle model to a compilation of GPS velocity fields in order to address the kinematics of deformation in the northwestern United States. A viscoelastic cycle model accounts for time-dependent deformation following large crustal earthquakes and is an alternative to block models for explaining the interseismic crustal velocity field. Building on the approach taken in Pollitz et al., we construct a deformation model for the entire western United States-based on combined fault slip and distributed deformation-and focus on the implications for the Mendocino triple junction (MTJ), Cascadia megathrust, and western Washington. We find significant partitioning between strike-slip and dip-slip motion near the MTJ as the tectonic environment shifts from northwest-directed shear along the San Andreas fault system to east-west convergence along the Juan de Fuca Plate. By better accounting for the budget of aseismic and seismic slip along the Cascadia subduction interface in conjunction with an assumed rheology, we revise a previous model of slip for the M~ 9 1700 Cascadia earthquake. In western Washington, we infer slip rates on a number of strike-slip and dip-slip faults that accommodate northward convergence of the Oregon Coast block and northwestward convergence of the Juan de Fuca Plate. Lateral variations in first order mechanical properties (e.g. mantle viscosity, vertically averaged rigidity) explain, to a large extent, crustal strain that cannot be rationalized with cyclic deformation on a laterally homogeneous viscoelastic structure. Our analysis also shows that present crustal deformation measurements, particularly with the addition of the Plate Boundary Observatory, can constrain such lateral variations.

Evaluation of borehole geophysical logging, aquifer-isolation tests, distribution of contaminants, and water-level measurements at the North Penn Area 5 Superfund Site, Bucks and Montgomery counties, Pennsylvania

USGS Publications Warehouse

Bird, Philip H.; Conger, Randall W.

2002-01-01

Borehole geophysical logging and aquifer-isolation (packer) tests were conducted at the North Penn Area 5 Superfund site in Bucks and Montgomery Counties, Pa. Caliper, naturalgamma, single-point-resistance, fluid-temperature, fluid-resistivity, heatpulse-flowmeter, and digital acoustic-televiewer logs and borehole television surveys were collected in 32 new and previously drilled wells that ranged in depth from 68 to 302 feet. Vertical borehole-fluid movement direction and rate were measured with a high-resolution heatpulse flowmeter under nonpumping conditions. The suite of logs was used to locate water-bearing fractures, determine zones of vertical borehole-fluid movement, select depths to set packers, and locate appropriate screen intervals for reconstructing new wells as monitoring wells. Aquifer-isolation tests were conducted in four wells to sample discrete intervals and to determine specific capacities of discrete water-bearing zones. Specific capacities of isolated zones during packer testing ranged from 0.12 to 15.30 gallons per minute per foot. Most fractures identified by borehole geophysical methods as water-producing or water-receiving zones produced water when isolated and pumped. The acoustic-televiewer logs define two basic fracture sets, bedding-plane partings with a mean strike of N. 62° E. and a mean dip of 27° NW., and high-angle fractures with a mean strike of N. 58° E. and a mean dip of 72° SE. Correlation of heatpulse-flowmeter data and acoustic-televiewer logs showed 83 percent of identified water-bearing fractures were high-angle fractures.

F-16XL ship #1 - CAWAP boundary layer rakes and hot film on left wing

NASA Technical Reports Server (NTRS)

1996-01-01

This photo shows the boundary layer hot film and the boundary layer rakes on the left wing of NASA's single-seat F-16XL (ship #1) used for the Cranked-Arrow Wing Aerodynamic Project (CAWAP) at Dryden Flight Research Center, Edwards, California. The modified airplane features a delta 'cranked-arrow' wing with strips of tubing along the leading edge to the trailing edge to sense static on the wing and obtain pressure distribution data. The right wing receives data on pressure distribution and the left wing has three types of instrumentation - preston tubes to measure local skin friction, boundary layer rakes to measure boundary layer profiles (the layer where the air interacts with the surfaces of a moving aircraft), and hot films to determine boundary layer transition locations. The program also gathered aero data on two wing planforms for NASA's High Speed Research Program. The first flight of CAWAP occurred on November 21, 1995, and the test program ended in April 1996.

Wall Boundary Layer Measurements for the NASA Langley Transonic Dynamics Tunnel

NASA Technical Reports Server (NTRS)

Wieseman, Carol D.; Bennett, Robert M.

2007-01-01

Measurements of the boundary layer parameters in the NASA Langley Transonic Dynamics tunnel were conducted during extensive calibration activities following the facility conversion from a Freon-12 heavy-gas test medium to R-134a. Boundary-layer rakes were mounted on the wind-tunnel walls, ceiling, and floor. Measurements were made over the range of tunnel operation envelope in both heavy gas and air and without a model in the test section at three tunnel stations. Configuration variables included open and closed east sidewall wall slots, for air and R134a test media, reentry flap settings, and stagnation pressures over the full range of tunnel operation. The boundary layer thickness varied considerably for the six rakes. The thickness for the east wall was considerably larger that the other rakes and was also larger than previously reported. There generally was some reduction in thickness at supersonic Mach numbers, but the effect of stagnation pressure, and test medium were not extensive.

Ductile and Brittle Neogene Deformation of Late Permian Orthogneiss in the Northern Ailao Shan-Red River Shear Zone: View from the Xuelong Shan Block

NASA Astrophysics Data System (ADS)

Wintsch, R. P.; Yi, D.; Yi, K.; Wang, Q. F.; Wang, G. H.

2014-12-01

The orthogneisses in the core of the Xuelong Shan block are surrounded by ductile and then brittle fault rocks. This lens-shape block is in fault contact with Triassic marbles on the eastern margin and Jurassic-Cretaceous mudstones on the western margin. The rocks in the core of the Xuelong Shan block contain multiply foliated feldspathic orthogneisses with local amphibolites, largely overprinted by protomylonitic deformation. Foliation strengthens to the east to become mylonites and ultramylonites, with a 30 m wide zone of loosely cemented fault breccia adjacent to brittlely faulted Triassic marbles. In contrast, the rocks to the west are dominated by brittle deformation, with mylonites becoming cataclasites and then breccias facing the mudstones to the east. Well-foliated phyllonites are locally present within the cataclasites. Early S1 gneissosity striking ENE are recognized only in the interior protomylonite. In the east, the dominate mylonitic S2 foliation strikes 340° with a moderate dip to the east, and an L2 mineral stretching lineation plunges gently north. However, in the west S2 cleavage is transposed into a NNW trending schistosity that dips steeply to the ENE, with down-dip mineral stretching lineations. Whole rock chemistry indicates a granitic to granodioritic protolith for all the rocks including the ultramylonites, but also suggests the progressive loss of alkalis with increasing deformation. Trace element compositions show these rocks lie in the volcanic arc/syn-collisional granite field. U-Pb SHRIMP ages show an Early Triassic age for these granite, with possible Middle Permian inheritance in some cores. These ages are consistent with the period of the closure of the northern Paleo-Tethys ocean. Metamorphic rim ages of ~ 30 Ma record a small amount of zircon dissolution/precipitation probably associated with the Oligocene ductile deformation that produced the upper greenschist facies mylonites. These results support the geologic history of the ASRRSZ based on data obtained in the southern Diancang Shan block. Permian granitoids were intruded and ductily deformed in the Early Triassic. The left lateral shearing that brought these blocks to the surface was delayed until the Neogene extrusion of the Indochina block.

Active shortening of the Cascadia forearc and implications for seismic hazards of the Puget Lowland

USGS Publications Warehouse

Johnson, S.Y.; Blakely, R.J.; Stephenson, W.J.; Dadisman, S.V.; Fisher, M.A.

2004-01-01

Margin-parallel shortening of the Cascadia forearc is a consequence of oblique subduction of the Juan de Fuca plate beneath North America. Strike-slip, thrust, and oblique crustal faults beneath the densely populated Puget Lowland accommodate much of this north-south compression, resulting in large crustal earthquakes. To better understand this forearc deformation and improve earthquake hazard, assessment, we here use seismic reflection surveys, coastal exposures of Pleistocene strata, potential-field data, and airborne laser swath mapping to document and interpret a significant structural boundary near the City of Tacoma. This boundary is a complex structural zone characterized by two distinct segments. The northwest trending, eastern segment, extending from Tacoma to Carr Inlet, is formed by the broad (??? 11.5 km), southwest dipping (??? 11??-2??) Rosedale monocline. This monocline raises Crescent Formation basement about 2.5 km, resulting in a moderate gravity gradient. We interpret the Rosedale monocline as a fault-bend fold, forming above a deep thrust fault. Within the Rosedale monocline, inferred Quaternary strata thin northward and form a growth triangle that is 4.1 to 6.6 km wide at its base, suggesting ??? 2-3 mm/yr of slip on the underlying thrust. The western section of the >40-km-long, north dipping Tacoma fault, extending from Hood Canal to Carr Inlet, forms the western segment of the Tacoma basin margin. Structural relief on this portion of the basin margin may be several kilometers, resulting in steep gravity and aeromagnetic anomalies. Quaternary structural relief along the Tacoma fault is as much as 350-400 m, indicating a minimum slip rate of about 0.2 mm/yr. The inferred eastern section of the Tacoma fault (east of Carr Inlet) crosses the southern part of the Seattle uplift, has variable geometry along strike, and diminished structural relief. The Tacoma fault is regarded as a north dipping backthrust to the Seattle fault, so that slip on a master thrust fault at depth could result in movement on the Seattle fault, the Tacoma fault, or both.

Evaluating Failure Mechanics of the Malpais Landslide, Eureka County, Nevada

NASA Astrophysics Data System (ADS)

Wilhite, C. P.; Carr, J. R.; Wallace, A. R.; Watters, R. J.

2008-12-01

The Malpais Landslide is located on the northeast end of the Shoshone Mountains in north-central Nevada. The 2.3 square kilometer slide originated near the crest of the Malpais Rim and flowed north into Whirlwind Valley. Given the proximity to Holocene faulting and active geothermal conditions, destabilizing forces include seismic activity, hydrothermal alteration, and changes in groundwater conditions. Approximately 3 km west of the slide is the Beowawe Geothermal Field, which is partially recharged along local faults and has altered geologic units throughout the slide area. The area contains two major normal faults (the approximately east striking Malpais Fault and the approximately north striking Dunphy Pass Fault) and numerous smaller faults. The most recent offset along the Malpais fault was approximately 7450 years B.P. (Wesnousky et al., 2005). The resulting scarp cannot be traced through the slide, therefore sliding occurred after that time (though previous sliding has not been ruled out). The stratigraphy in the slide area consists of a basal Paleozoic quartzite, unconformably overlain by Oligocene to Miocene conglomeratic to tuffaceous sediments with interbedded volcanic flows, capped by a sequence of mafic flow units. Except for the lowest sedimentary unit, Tts, all units dip approximately 25 degrees southeast. Tts was measured in outcrops east of the site and dips approximately 20 degrees north; since these outcrops could not be traced into the slide area, the dip of Tts at the slide is unknown. Point-load testing showed Tts to have a tensile strength of 3.12 MPa which is 55% weaker than the next weakest unit in the area. These factors, as well as Tts" semiconsolidated nature, suggest that Tts was the unit of failure. Further testing of the Malpais Landslide, as well as computer simulation, will be used to determine the cause of failure. This information and the examination of other nearby landslides may be helpful in assessing landslide risk in north-central Nevada and regions with similar characteristics. Reference: Wesnousky, S., Barron, A., Briggs, R., Caskey, S., Kumar, S., and Owen, L., 2005, Paleoseismic Transect Across the Northern Great Basin, Journal of Geophysical Research, v. 110.

The Pliocene-Quaternary tectonic evolution of the Cilicia and Adana basins, eastern Mediterranean: Special reference to the development of the Kozan Fault zone

NASA Astrophysics Data System (ADS)

Aksu, A. E.; Walsh-Kennedy, S.; Hall, J.; Hiscott, R. N.; Yaltırak, C.; Akhun, S. D.; Çifçi, G.

2014-05-01

A grid of high-resolution multi-channel seismic reflection profiles allows the detailed mapping of the Kozan Fault zone in the Cilicia and Adana basins. The zone is delineated by an arcuate zone consisting of several ENE-WSW and NNE-SSW striking, closely-spaced high-angle extensional faults which define an ~ 300 km long and 15-20 km-wide “lazy-S” shaped structure along the southeastern fringes of the Taurus Mountain and along the northwestern margins of the Cilicia and Adana basins. In the Cilicia Basin the zone consists of several high-angle faults which exhibit small dip separations on the M-reflector and have tip points situated mainly in the lower and middle portion of the Pliocene-Quaternary succession. In the Adana Basin a family of northeast-striking and southeast dipping extensional faults occurs along the western and northwestern margin of the basin. The faults cut down with relatively steep dip into the ~ 700 ms thick Tortonian and older Miocene successions. Multi-channel seismic reflection profiles show that three prominent seismic markers divide the uppermost Messinian-Recent successions in the Cilicia and Adana basins into three subunits: the uppermost Messinian-Lower Pliocene subunit 1C between the M- and A-reflectors, the Upper Pliocene subunit 1B between the A- and P-reflectors and the Quaternary subunit 1A between the P-reflector and the seafloor. Prominent delta lobes are identified in the seismic profiles that are correlated with the ancestral Göksu River. Isopach maps constructed using depth-converted seismic reflection profiles show clear temporal and spatial variations of the delta lobes of the Göksu River during the latest Messinian-Recent. The uppermost Messinian-Lower Pliocene delta lobe is situated furthest to the northeast whereas the youngest Quaternary lobe is situated furthest to the southwest, with 20-35 km displacement along a northeast-southwest line, which suggests a conservative estimate of 0.43-0.75 cm/yr sinistral slip for the Kozan Fault zone.

Thermochronologic constraints on the Miocene slip history of the South Tibetan detachment system in the Everest region, central Himalaya

NASA Astrophysics Data System (ADS)

Schultz, M.; Hodges, K. V.; Van Soest, M. C.; Wartho, J. A.

2014-12-01

North-dipping, low-angle normal faults of the South Tibetan detachment system (STDS) can be traced for a distance of more than 2000 km along strike and represent an important tectonic characteristic of the Miocene Himalayan-Tibetan orogenic system. Nowhere is the STDS better exposed than the N-S-trending Rongbuk Valley in southern Tibet, where it can be traced down dip from the summit of Everest for a distance of over 30 km before disappearing beneath the valley floor. This places a minimum constraint on Miocene displacement on the feature in this area, but some research groups have suggested ~200 km of displacement based on the difference in metamorphic pressures across the STDS and the very low (< 15˚) primary dip of the structure. We are exploring this issue further using developing (U-Th)/He and 40Ar/39Ar datasets from deformed footwall sillimanite gneisses and leucogranites. Data obtained thus far indicate relatively rapid cooling of the footwall after the intrusion of deformed leucogranites at ca. 16.7 Ma to muscovite 40Ar/39Ar closure temperatures (ca. 15.5-14.2 Ma) and zircon (U-Th)/He closure temperatures (ca. 14.5-11 Ma). We attribute this cooling to tectonic denudation related to ca. 16 Ma STDS slip. Although the (U-Th)/He systematics of apatites from these rocks is complex, our current interpretation of available data places cooling through the ca. 75˚C closure isotherm at ca. 8-9 Ma, which would suggest a significant reduction in cooling rate that is observed in our inverse model runs of the 1D program, HeFTy. Ongoing analyses of footwall samples from ~8 km to the north of our Rongbuk sample localities in the Ra Chu river valley will greatly strengthen our datasets. With the Ra Chu analyses, our datasets will constrain the cooling history of the footwall for more than 20 km perpendicular to the strike of the detachment. Our presentation will also incorporate results from the program Pecube that will contribute to our calculation of the slip rate by specifying the appropriate exhumation rate.

Evidence of extensional and strike-slip deformation in the offshore Gökova-Kos area affected by the July 2017 Mw6.6 Bodrum-Kos earthquake, eastern Aegean Sea

NASA Astrophysics Data System (ADS)

Ocakoğlu, Neslihan; Nomikou, Paraskevi; İşcan, Yeliz; Loreto, Maria Filomena; Lampridou, Danai

2018-06-01

The interpretation of new multichannel seismic profiles and previously published high-resolution swath and seismic reflection data from the Gökova Gulf and southeast of Kos Island in the eastern Aegean Sea revealed new morphotectonic features related to the July 20, 2017 Mw6.6 Bodrum-Kos earthquake offshore between Kos Island and the Bodrum Peninsula. The seafloor morphology in the northern part of the gulf is characterized by south-dipping E-W-oriented listric normal faults. These faults bend to a ENE-WSW direction towards Kos Island, and then extend parallel to the southern coastline. A left-lateral SW-NE strike-slip fault zone is mapped with segments crossing the Gökova Gulf from its northern part to south of Kos Island. This fault zone intersects and displaces the deep basins in the gulf. The basins are thus interpreted as the youngest deformed features in the study area. The strike-slip faults also produce E-W-oriented ridges between the basin segments, and the ridge-related vertical faults are interpreted as reverse faults. This offshore study reveals that the normal and strike-slip faults are well correlated with the focal mechanism solutions of the recent earthquake and general seismicity of the Gökova Gulf. Although the complex morphotectonic features could suggest that the area is under a transtensional regime, kinematic elements normally associated with a transtensional system are missing. At present, the Gökova Gulf is experiencing strike-slip motion with dominant extensional deformation, rather than transtensional deformation.

Volcanic facies architecture of an intra-arc strike-slip basin, Santa Rita Mountains, Southern Arizona

NASA Astrophysics Data System (ADS)

Busby, Cathy J.; Bassett, Kari N.

2007-09-01

The three-dimensional arrangement of volcanic deposits in strike-slip basins is not only the product of volcanic processes, but also of tectonic processes. We use a strike-slip basin within the Jurassic arc of southern Arizona (Santa Rita Glance Conglomerate) to construct a facies model for a strike-slip basin dominated by volcanism. This model is applicable to releasing-bend strike-slip basins, bounded on one side by a curved and dipping strike-slip fault, and on the other by curved normal faults. Numerous, very deep unconformities are formed during localized uplift in the basin as it passes through smaller restraining bends along the strike-slip fault. In our facies model, the basin fill thins and volcanism decreases markedly away from the master strike-slip fault (“deep” end), where subsidence is greatest, toward the basin-bounding normal faults (“shallow” end). Talus cone-alluvial fan deposits are largely restricted to the master fault-proximal (deep) end of the basin. Volcanic centers are sited along the master fault and along splays of it within the master fault-proximal (deep) end of the basin. To a lesser degree, volcanic centers also form along the curved faults that form structural highs between sub-basins and those that bound the distal ends of the basin. Abundant volcanism along the master fault and its splays kept the deep (master fault-proximal) end of the basin overfilled, so that it could not provide accommodation for reworked tuffs and extrabasinally-sourced ignimbrites that dominate the shallow (underfilled) end of the basin. This pattern of basin fill contrasts markedly with that of nonvolcanic strike-slip basins on transform margins, where clastic sedimentation commonly cannot keep pace with subsidence in the master fault-proximal end. Volcanic and subvolcanic rocks in the strike-slip basin largely record polygenetic (explosive and effusive) small-volume eruptions from many vents in the complexly faulted basin, referred to here as multi-vent complexes. Multi-vent complexes like these reflect proximity to a continuously active fault zone, where numerous strands of the fault frequently plumb small batches of magma to the surface. Releasing-bend extension promotes small, multivent styles of volcanism in preference to caldera collapse, which is more likely to form at releasing step-overs along a strike-slip fault.

Hydrogeologic setting, ground-water flow, and ground-water quality at the Lake Wheeler Road research station, 2001-03 : North Carolina Piedmont and Mountains Resource Evaluation Program

USGS Publications Warehouse

Chapman, Melinda J.; Bolich, Richard E.; Huffman, Brad A.

2005-01-01

Results of a 2-year field study of the regolith-fractured bedrock ground-water system at the Lake Wheeler Road research station in Wake County, North Carolina, indicate both disconnection and interaction among components of the ground-water system. The three components of the ground-water system include (1) shallow, porous regolith; (2) a transition zone, including partially weathered rock, having both secondary (fractures) and primary porosity; and (3) deeper, fractured bedrock that has little, if any, primary porosity and is dominated by secondary fractures. The research station includes 15 wells (including a well transect from topographic high to low settings) completed in the three major components of the ground-water-flow system and a surface-water gaging station on an unnamed tributary. The Lake Wheeler Road research station is considered representative of a felsic gneiss hydrogeologic unit having steeply dipping foliation and a relatively thick overlying regolith. Bedrock foliation generally strikes N. 10? E. to N. 30? E. and N. 20? W. to N. 40? W. to a depth of about 400 feet and dips between 70? and 80? SE. and NE., respectively. From 400 to 600 feet, the foliation generally strikes N. 70? E. to N. 80? E., dipping 70? to 80? SE. Depth to bedrock locally ranges from about 67 to 77 feet below land surface. Fractures in the bedrock generally occur in two primary sets: low dip angle, stress relief fractures that cross cut foliation, and steeply dipping fractures parallel to foliation. Findings of this study generally support the conceptual models of ground-water flow from high to low topographic settings developed for the Piedmont and Blue Ridge Provinces in previous investigations, but are considered a refinement of the generalized conceptual model based on a detailed local-scale investigation. Ground water flows toward a surface-water boundary, and hydraulic gradients generally are downward in recharge areas and upward in discharge areas; however, local variations in vertical gradients are apparent. Water-quality sampling and monitoring efforts were conducted to characterize the interaction of components of the ground-water system. Elevated nitrate concentrations as high as 22 milligrams per liter were detected in shallow ground water from the regolith at the study site. These elevated nitrate concentrations likely are related to land use, which includes agricultural practices that involve animal feeding operations and crop fertilization. Continuous ground-water-quality data indicate seasonal fluctuations in field water-quality properties, differences with respect to depth, and fluctuations during recharge events. Water-quality properties recorded in the regolith well following rainfall indicate the upwelling of deeper ground water in the discharge area, likely from ground water in the transition-zone fractures. Additionally, interaction with a surface-water boundary appears likely in the ground-water discharge area, as water levels in all three ground-water zones, including the deep bedrock, mimic the surface-water rise during rainfall.

A comparison study of 2006 Java earthquake and other Tsunami earthquakes

NASA Astrophysics Data System (ADS)

Ji, C.; Shao, G.

2006-12-01

We revise the slip processes of July 17 2006 Java earthquakes by combined inverting teleseismic body wave, long period surface waves, as well as the broadband records at Christmas island (XMIS), which is 220 km away from the hypocenter and so far the closest observation for a Tsunami earthquake. Comparing with the previous studies, our approach considers the amplitude variations of surface waves with source depths as well as the contribution of ScS phase, which usually has amplitudes compatible with that of direct S phase for such low angle thrust earthquakes. The fault dip angles are also refined using the Love waves observed along fault strike direction. Our results indicate that the 2006 event initiated at a depth around 12 km and unilaterally rupture southeast for 150 sec with a speed of 1.0 km/sec. The revised fault dip is only about 6 degrees, smaller than the Harvard CMT (10.5 degrees) but consistent with that of 1994 Java earthquake. The smaller fault dip results in a larger moment magnitude (Mw=7.9) for a PREM earth, though it is dependent on the velocity structure used. After verified with 3D SEM forward simulation, we compare the inverted result with the revised slip models of 1994 Java and 1992 Nicaragua earthquakes derived using the same wavelet based finite fault inversion methodology.

Magnetite deposits near Klukwan and Haines, southeastern Alaska

USGS Publications Warehouse

Robertson, Eugene C.

1956-01-01

Low-grade iron ore is found in magnetite-bearing pyroxenite bodies near Klukwan and Haines in Southeastern Alaska. An alluvial fan at Haines also contains magnetite-bearing rock of possible economic significance. The Haines-Klukwan area is underlain by rocks of Mesozoic Including epidote diorite, quartz diorite, and alaskite of the Coast Range batholith, metabasalt (recrystallized lava flows and pyroclastic rocks), and, in the southern part, interbedded slate and limestone. Layering and foliation, where perceptible, generally strike northwest and dip steeply northeast. The iron deposits are found at or near the contact between the metabasalt and epidote diorite; they appear to represent highly-altered lava flows that were metamorphosed during the emplacement of the batholith. Several billion tens of rock containing about 13 percent magnetic iron are included in the pyroxenite body at Klukwan. Sampling and dip-needle data suggest the presence there of two or three tabular aches in which the rock has an average magnetic iron content of 20 percent or more. Pyroxenite bodies outcropping in three areas near Haines apparently are lower in grade than the Klukwan deposit; lack of exposures prevented thorough sampling but reconnaissance traverses with a dip needle failed to reveal important zones of high-grade iron ore. An alluvial fan adjoining the pyroxenite body at Klukwan contains several hundred million tons of broken rock having a magneticiron content of about 10 percent.

Crustal Gravitational Potential Energy Change and Subduction Earthquakes

NASA Astrophysics Data System (ADS)

Zhu, P. P.

2017-05-01

Crustal gravitational potential energy (GPE) change induced by earthquakes is an important subject in geophysics and seismology. For the past forty years the research on this subject stayed in the stage of qualitative estimate. In recent few years the 3D dynamic faulting theory provided a quantitative solution of this subject. The theory deduced a quantitative calculating formula for the crustal GPE change using the mathematic method of tensor analysis under the principal stresses system. This formula contains only the vertical principal stress, rupture area, slip, dip, and rake; it does not include the horizontal principal stresses. It is just involved in simple mathematical operations and does not hold complicated surface or volume integrals. Moreover, the hanging wall vertical moving (up or down) height has a very simple expression containing only slip, dip, and rake. The above results are significant to investigate crustal GPE change. Commonly, the vertical principal stress is related to the gravitational field, substituting the relationship between the vertical principal stress and gravitational force into the above formula yields an alternative formula of crustal GPE change. The alternative formula indicates that even with lack of in situ borehole measured stress data, scientists can still quantitatively calculate crustal GPE change. The 3D dynamic faulting theory can be used for research on continental fault earthquakes; it also can be applied to investigate subduction earthquakes between oceanic and continental plates. Subduction earthquakes hold three types: (a) crust only on the vertical up side of the rupture area; (b) crust and seawater both on the vertical up side of the rupture area; (c) crust only on the vertical up side of the partial rupture area, and crust and seawater both on the vertical up side of the remaining rupture area. For each type we provide its quantitative formula of the crustal GPE change. We also establish a simplified model (called CRW Model) as follows: for Type B and Type C subduction earthquakes, if the seawater average depth on the vertical up side of the rupture area is less than a tenth of the hypocenter depth, then take the approximation that the seawater above the continental plate is replaced by the upper crustal material of the continental plate. The formula of quantitative calculating the crustal GPE change is also provided for this model. Finally, for 16 September 2015 Mw 8.3 Illapel Chile earthquake, we apply CRW Model and obtain the following results: the crustal GPE change is equal to 1.8 × 1019 J, and the hanging wall vertical moving-up height is 1.9 m with respect to the footwall. We believe this paper might be the first report on the quantitative solution of the crustal GPE change for this subduction earthquake; our results and related method will be helpful in research into the earthquakes in Peru-Chile subduction zone and the Andean orogeny. In short, this study expounds a new method for quantitative determining the crustal GPE change caused by subduction earthquakes, which is different from other existing methods.

Crustal structure and fault geometry of the 2010 Haiti earthquake from temporary seismometer deployments

USGS Publications Warehouse

Douilly, Roby; Haase, Jennifer S.; Ellsworth, William L.; Bouin, Marie‐Paule; Calais, Eric; Symithe, Steeve J.; Armbruster, John G.; Mercier de Lépinay, Bernard; Deschamps, Anne; Mildor, Saint‐Louis; Meremonte, Mark E.; Hough, Susan E.

2013-01-01

Haiti has been the locus of a number of large and damaging historical earthquakes. The recent 12 January 2010 Mw 7.0 earthquake affected cities that were largely unprepared, which resulted in tremendous losses. It was initially assumed that the earthquake ruptured the Enriquillo Plantain Garden fault (EPGF), a major active structure in southern Haiti, known from geodetic measurements and its geomorphic expression to be capable of producing M 7 or larger earthquakes. Global Positioning Systems (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data, however, showed that the event ruptured a previously unmapped fault, the Léogâne fault, a north‐dipping oblique transpressional fault located immediately north of the EPGF. Following the earthquake, several groups installed temporary seismic stations to record aftershocks, including ocean‐bottom seismometers on either side of the EPGF. We use data from the complete set of stations deployed after the event, on land and offshore, to relocate all aftershocks from 10 February to 24 June 2010, determine a 1D regional crustal velocity model, and calculate focal mechanisms. The aftershock locations from the combined dataset clearly delineate the Léogâne fault, with a geometry close to that inferred from geodetic data. Its strike and dip closely agree with the global centroid moment tensor solution of the mainshock but with a steeper dip than inferred from previous finite fault inversions. The aftershocks also delineate a structure with shallower southward dip offshore and to the west of the rupture zone, which could indicate triggered seismicity on the offshore Trois Baies reverse fault. We use first‐motion focal mechanisms to clarify the relationship of the fault geometry to the triggered aftershocks.

Integration of COCORP deep reflection and magnetic anomaly analysis in the southeastern United States: Implications for origin of the Brunswick and East Coast magnetic anomalies: Alternative interpretation and reply

USGS Publications Warehouse

Hutchinson, Deborah R.; Klitgord, Kim D.; Tréhu, Anne M.; McBride, John H.; Nelson, K. D.

1990-01-01

Integration of magnetic anomaly analysis with COCORP deep reflection data from the southeastern United States provides three new constraints on the interpretation of the Brunswick and East Coast magnetic anomalies, as well as on the reflection data. These are as follows. (1) The source of the Brunswick anomaly lies within the deep crust. This anomaly is not caused by a Mesozoic rift basin, as proposed by some workers. (2) A simple, seaward-dipping, high- susceptibility slab model can explain both the Brunswick and East Coast magnetic anomalies. The along-strike change in character of the two anomalies results largely from a change in azimuth of the source body. (3) Beneath the southeastern United States, this source body dips south, lies immediately on the south flank of the prominent southward-dipping reflective zone revealed on COCORP surveys, and was previously associated with the Alleghanian suture between North America and Africa. These results imply that a dipping, highly magnetized zone in the upper plate of the Alleghanian suture is responsible for both the Brunswick and East Coast magnetic anomalies. The high- susceptibility material responsible for these anomalies might be mafic lower continental or oceanic crust thrust upward during Alleghanian continental collision, or mafic igneous material intruded into the upper plate of the suture zone during subsequent Mesozoic rifting, or both. The latter hypothesis implies that the Alleghanian suture acted, as a zone of weakness (a repository ?) which was reactivated to control the site of ultimate Atlantic rifting and possibly initial sea-floor spreading.

Crustal anisotropy across eastern Tibet and surroundings modeled as a depth-dependent tilted hexagonally symmetric medium

NASA Astrophysics Data System (ADS)

Xie, Jiayi; Ritzwoller, Michael H.; Shen, Weisen; Wang, Weitao

2017-04-01

Two types of surface wave anisotropy are observed regularly by seismologists but are only rarely interpreted jointly: apparent radial anisotropy, which is the difference in propagation speed between horizontally and vertically polarized waves inferred from Love and Rayleigh waves, and apparent azimuthal anisotropy, which is the directional dependence of surface wave speeds (usually Rayleigh waves). We show that a new data set of Love and Rayleigh wave isotropic phase speeds and Rayleigh wave azimuthal anisotropy observed within and surrounding eastern Tibet can be explained simultaneously by modeling the crust as a depth-dependent tilted hexagonally symmetric (THS) medium. We specify the THS medium with depth-dependent hexagonally symmetric elastic tensors tilted and rotated through dip and strike angles and estimate these quantities using a Bayesian Monte Carlo inversion to produce a 3-D model of the crust and uppermost mantle on a 0.5° × 0.5° spatial grid. In the interior of eastern Tibet and in the Yunnan-Guizhou plateau, we infer a steeply dipping THS upper crustal medium overlying a shallowly dipping THS medium in the middle-to-lower crust. Such vertical stratification of anisotropy may reflect a brittle to ductile transition in which shallow fractures and faults control upper crustal anisotropy and the crystal-preferred orientation of anisotropic (perhaps micaceous) minerals governs the anisotropy of the deeper crust. In contrast, near the periphery of the Tibetan Plateau the anisotropic medium is steeply dipping throughout the entire crust, which may be caused by the reorientation of the symmetry axes of deeper crustal anisotropic minerals as crustal flows are rotated near the borders of Tibet.

Research Results Of Stress-Strain State Of Cutting Tool When Aviation Materials Turning

NASA Astrophysics Data System (ADS)

Serebrennikova, A. G.; Nikolaeva, E. P.; Savilov, A. V.; Timofeev, S. A.; Pyatykh, A. S.

2018-01-01

Titanium alloys and stainless steels are hard-to-machine of all the machining types. Cutting edge state of turning tool after machining titanium and high-strength aluminium alloys and corrosion-resistant high-alloy steel has been studied. Cutting forces and chip contact arears with the rake surface of cutter has been measured. The relationship of cutting forces and residual stresses are shown. Cutting forces and residual stresses vs value of cutting tool rake angle relation were obtained. Measurements of residual stresses were performed by x-ray diffraction.

High-Subsonic Performance Characteristics and Boundary-Layer Investigations of a 12 deg 10-Inch-Inlet-Diameter Conical Diffuser

DTIC Science & Technology

1950-05-11

available condition supersonic flow was obtained as far as K.5 inches downstream from the diffueer inlet with a maximum Mach number of M % 1.5...Boundary—layer total-pressure measurements were made with the rake shown in figure k. The tubes varied in size from 0.030-Inch outside diameter...at the wall to 0.050—inch outside diameter farther out. A static-pressure tube was mounted on the rake to measure static pressures at the same

Experiments in Numerical Studies of Low Density and Real Gas Effects on Regions of Shock Wave/Boundary Layer Interaction in Hypervelocity Flows

DTIC Science & Technology

2006-06-01

Figure 13 Survey Rake containing Instrumentation to Measure Pitot and Static Pressure, Heating Distributions on Cylinders and Spheres, and Cone...35a and is in close agreement with the inviscid flow prediction in Figure 35b. Measurements made with a pitot pressure rake positioned at the end of...Velocity 15,00o 7 ’ DISOl• AglOrf (feet per sec) 10 N•’’ 10,000 47_T"___ ____ VIBATIONA Hypersonic 5,000 EXCITATION REGION Supersonic IDEAL GAS -Transonic 0

Fluid Dynamic and Acoustic Experiments on Turbomachine Rotors Subject to Variable Flow Conditions

DTIC Science & Technology

1990-03-31

conjunction with a standard pitot tube that is mounted in the wind tunnel test section upstream of the dynamometer system. The 4 manometer has a...generator." The smoke is then pumped into a "smoke rake ," in which it cools to ambient temperature and is directed the smoke into the inlet of the wind...34 and "smoke rake " are shown in Figures 5 and 6. A more complete explanation of the smoke generation process and apparatus is provided by Mueller (1983

An Innovative Flow-Measuring Device: Thermocouple Boundary Layer Rake

NASA Technical Reports Server (NTRS)

Hwang, Danny P.; Fralick, Gustave C.; Martin, Lisa C.; Wrbanek, John D.; Blaha, Charles A.

2001-01-01

An innovative flow-measuring device, a thermocouple boundary layer rake, was developed. The sensor detects the flow by using a thin-film thermocouple (TC) array to measure the temperature difference across a heater strip. The heater and TC arrays are microfabricated on a constant-thickness quartz strut with low heat conductivity. The device can measure the velocity profile well into the boundary layer, about 65 gm from the surface, which is almost four times closer to the surface than has been possible with the previously used total pressure tube.

Origin of the Uinta recess, Sevier fold thrust belt, Utah: influence of basin architecture on fold thrust belt geometry

NASA Astrophysics Data System (ADS)

Paulsen, Timothy; Marshak, Stephen

1999-11-01

Structural trends in the Sevier fold-thrust belt define a pronounced concave-to-the-foreland map-view curve, the Uinta recess, in north-central Utah. This recess separates two convex-to-the-foreland curves, the Provo salient on the south and the Wyoming salient on the north. The two limbs of the recess comprise transverse zones (fault zones at a high-angle to the regional trend of the orogen) that border the flanks of the east-west-trending Uinta/Cottonwood arch. Our structural analysis indicates that the transverse zones formed during the Sevier orogeny, and that they differ markedly from each other in structural style. The Charleston transverse zone (CTZ), on the south side of the arch, initiated as a complex sinistral strike-slip fault system that defines the abrupt northern boundary of the Provo salient. The Mount Raymond transverse zone (MRTZ), on the north side of the arch, represents the region in which the southeast-verging southern limb of the gently curving Wyoming salient was tilted northwards during the Laramide phase of uplift of the Uinta/Cottonwood arch. In effect, the MRTZ represents an oblique cross section through a thrust belt. The contrasting architecture of these transverse zones demonstrates how pre-deformation basin geometry influences the geometry of a fold-thrust belt. Analysis of isopach maps indicates that, at the time the Sevier fold-thrust belt formed, the area just north of the present site of the Uinta/Cottonwood arch was a basement high, with a gently dipping north flank, and a steeply dipping south flank. Thus, predeformational sediment thickened abruptly to the south of the high and thickened gradually to the north of the high. As illustrated by sandbox models, the distance that a fold-thrust belt propagates into the foreland depends on the thickness of the sedimentary layer being deformed, so the shape of the salient mimics the longitudinal cross-sectional shape of the sedimentary basin. Where basins taper gradually along strike, the thrust belt curves gently, but where basins taper abruptly along strike, the thrust belt curves so tightly that it disarticulates and becomes bounded laterally by a strike-slip accommodation zone. The geometry of the Uinta recess provides a field example of this concept. Differential movement of Sevier thrusts led to formation of gradually curving thrusts on the north side of the high, because of the gradual slope of the high's north flank, but led to the along-strike disarticulation of thrusts on the south side of the high, because of the steep slope of the high's south flank. In effect, therefore, thrust belt map-view geometry provides insight into predeformational basin geometry.

3-D structure of the crust and uppermost mantle at the junction between the Southeastern Alps and External Dinarides from ambient noise tomography

NASA Astrophysics Data System (ADS)

Guidarelli, Mariangela; Aoudia, Abdelkrim; Costa, Giovanni

2017-12-01

We use ambient noise tomography to investigate the crust and the uppermost mantle structure beneath the junction between the Southern Alps, the Dinarides and the Po Plain. We obtained Rayleigh wave empirical Green's functions from cross-correlation of vertical component seismic recordings for three years (2010-2012) using stations from networks in Italy, Slovenia, Austria, Croatia, Serbia and Switzerland. We measure group and phase velocity dispersion curves from the reconstructed Rayleigh waves in the period range 5-30 and 8-37 s, respectively, and we invert the surface wave velocities for tomographic images on a grid of 0.1° × 0.1°. After the tomography, the group velocities are then inverted to compute the 3-D shear wave velocity model of the crust and the upper mantle beneath the region. Our shear wave velocity model provides the 3-D image of the structure in the region between Northeastern Italy, Slovenia and Austria. The velocity variations at shallow depths correlate with known geological and tectonic domains. We find low velocities below the Po Plain, the northern tip of the Adriatic and the Pannonian Basin, whereas higher velocities characterize the Alpine chain. The vertical cross-sections reveal a clear northward increase of the crustal thickness with a sharp northward dipping of the Moho that coincides at the surface with the leading edge of the Alpine thrust front adjacent to the Friuli Plain in Northeastern Italy. This geometry of the Moho mimics fairly well the shallow north dipping geometry of the decollement inferred from permanent GPS velocity field where high interseismic coupling is reported. From the northern Adriatic domain up to the Idrija right lateral strike-slip fault system beneath Western Slovenia, the crustal thickness is more uniform. Right across Idrija fault, to the northeast, and along its strike, we report a clear change of the physical properties of the crust up to the uppermost mantle as reflected by the lateral distribution of both group and phase velocity anomalies at relevant periods. Idrija fault is therefore interpreted as a subvertical fault sampling the whole crust. Our 3-D velocity model favours crustal thickening with Adria underthrusting the Alps at a shallow angle north of the Friuli Plain where much of the convergence is absorbed and where the destructive 1976 Ms 6.5 thrust Friuli earthquake sequence took place. In Western Slovenia, the deformation is accommodated by strike-slip motion along the Idrija strike-slip fault system where the destructive 1511 Mw 6.9 right lateral strike-slip event occurred.

Tank 12H Acidic Chemical Cleaning Sample Analysis And Material Balance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martino, C. J.; Reboul, S. H.; Wiersma, B. J.

2013-11-08

A process of Bulk Oxalic Acid (BOA) chemical cleaning was performed for Tank 12H during June and July of 2013 to remove all or a portion of the approximately 4400 gallon sludge heel. Three strikes of oxalic acid (nominally 4 wt% or 2 wt%) were used at 55°C and tank volumes of 96- to 140-thousand gallons. This report details the sample analysis of a scrape sample taken prior to BOA cleaning and dip samples taken during BOA cleaning. It also documents a rudimentary material balance for the Tank 12H cleaning results.

Along-Strike Differences of the Main Himalayan Thrust and Deformation within the Indian Crust: Insights from Seismicity and Seismic Velocities in Bhutan and its Foreland

NASA Astrophysics Data System (ADS)

Diehl, T.; Singer, J.; Hetényi, G.; Kissling, E. H.; Clinton, J. F.

2015-12-01

The seismicity of Bhutan is characterized by the apparent lack of great earthquakes and a significantly lower activity compared to most other parts of the Himalayan arc. To better understand the underlying mechanisms of this anomalously low activity and to relate it with possible along-strike differences in the structure of the orogenic belt, a temporary network with up to 38 broadband seismometers was installed in Bhutan between January 2013 and November 2014. In this work we present a catalog of local and regional earthquakes detected and located with the GANSSER network complemented by regional stations in India, Bangladesh, and China. State-of-the-art data analysis and earthquake location procedures were applied to derive a high-precision earthquake catalog of Bhutan and surrounding regions. Focal mechanisms from regional moment tensor inversions and first-motion polarities complement the earthquake catalog. In the vicinity of the Shumar-Kuru Chu Spur in East Bhutan, seismicity forms a moderately dipping structure at about 12 km depth, which we associate with the Main Himalayan Thrust (MHT). North of 27.6°N the dip of the structure steepens, which can be interpreted as a ramp along the MHT. In West Bhutan seismicity occurs at depths of 20 to 40 km and receiver function images indicate that seismicity occurs in the underthrusting Indian crust rather than on the MHT. The highest seismic activity is clustered along the Goalpara Lineament, a dextral NE-SW striking shear zone in southwest Bhutan, which appears to connect to the western edge of the Shillong Plateau in the foreland. Focal depths indicate that this shear zone is located at depths of 20-30 km and therefore in the underthrusting Indian crust. Preliminary results of a 3D local earthquake tomography show substantial differences in the uppermost crust between east and west Bhutan. Consistent with our receiver function images, the results also indicate a thinning of the crustal root towards eastern Bhutan.

Balancing cross-sections combining field work and remote sensing data using LithoTect software in the Zagros fold-and-thrust belt, N Iraq.

NASA Astrophysics Data System (ADS)

Reif, Daniel; Grasemann, Bernhard; Lockhart, Duncan

2010-05-01

The Zagros fold-and-thrust belt has formed in detached Phanerozoic sedimentary cover rocks above a shortened crystalline Precambrian basement and evolved through the Late Cretaceous to Miocene collision between the Arabian and Eurasian plate, during which the Neotethys oceanic basin was closed. Deformation is partitioned in SW directed folding and thrusting of the sediments and NW-SE to N-S trending dextral strike slip faults. The sub-cylindrical doubly-plunging fold trains with wavelengths of 5 - 10 km host more than half of the world's hydrocarbon reserves in mostly anticlinal traps. Generally the Zagros is divided into three NW-SE striking tectonic units: the Zagros Imbricate Zone, the Zagros Simply Folded Belt and the Zagros Foredeep. This work presents a balanced cross-section through the Simply Folded Belt, NE of the city of Erbil (Kurdistan, Iraq). The regional stratigraphy comprises mainly Cretaceous to Cenozoic folded sediments consisting of massive, carbonate rocks (limestones, dolomites), reacting as competent layers during folding compared to the incompetent behavior of interlayered siltstones, claystones and marls. Although the overall security situation in Kurdistan is much better than in the rest of Iraq, structural field mapping was restricted to asphalt streets, mainly because of the contamination of the area with landmines and unexploded ordnance. In order to extend the structural measurements statistically over the investigated area, we used a newly developed software tool (www.terramath.com) for interactive structural mapping of spatial orientations (i.e. dip direction and dip angles) of the sedimentary beddings from digital elevation models. Structural field data and computed measurements where integrated and projected in NE-SW striking balanced cross-sections perpendicular to the regional trend of the fold axes. We used the software LithoTect (www.geologicsystems.com) for the restoration of the cross-sections. Depending on the interpretation of the shape of the synclines, which are not exposed and covered by Neogene sediments, the shortening is in the order of 10-20%. The restoration confirms that large scale faulting is only of minor importance in the Simply Folded Belt.

Kinematics and timing of three superposed extensional systems, east central Idaho: Evidence for an Eocene tectonic transition

NASA Astrophysics Data System (ADS)

Janecke, Susanne U.

1992-12-01

Cenozoic crustal extension in east central Idaho began about 50 Ma and continues at present. Three distinct episodes characterize one of the longest intervals of Cenozoic extension yet documented in the North America Cordillera. Crosscutting relationships between NE striking normal faults and volcanic rocks, regional dike trends, and slickenline data indicate NW-SE extension during peak Eocene volcanism about 49-48 Ma (episode 1). NE striking normal faults, with at most a few kilometers of offset, formed in an intraarc setting during rapid NE subduction of oceanic plates under the Pacific Northwest. North to NNW striking and west dipping normal faults, with offsets up to 10-15 km, formed during a younger middle Eocene to Oligocene basin-forming event (episode 2). This newly documented episode was the most important extensional event in east central Idaho and began during the waning phases of Challis volcanism. WSW-ENE to SW-NE extension during episode 2 was nearly perpendicular to the extension direction during episode 1 and perpendicular to the grain of the Idaho-Montana fold and thrust belt. The flip in extension direction between episode 1 and episode 2 is tightly constrained by 40Ar/39Ar age determinations to have taken place at the end of Eocene Challis magmatism about 46-48 Ma. I infer that plate boundary forces controlled the geometry of normal faults and dikes during episode 1, whereas internal stresses within previously thickened crust drove major SW to WSW directed extension during episode 2. A drop in convergence rates between the North American and Farallon plates between 59 Ma and 42 Ma (Stock and Molnar, 1988) may coincide with the onset of gravitational spreading during episode 2 and may also explain the abrupt end of Eocene magmatism in the Pacific Northwest. Miocene and younger SW dipping Basin and Range faults (episode 3) extended the region in a NE-SW direction. Although faults formed during episode 2 and episode 3 are not parallel, slickenlines indicate only small changes in slip vector trends, suggesting little rotation of the extension direction in east central Idaho since 46 Ma.

Seismotectonics of the Eastern Himalayan System and Indo-Burman Convergence Zone Using Seismic Waveform Inversion

NASA Astrophysics Data System (ADS)

Kumar, A.; Mitra, S.; Suresh, G.

2014-12-01

The Eastern Himalayan System (east of 88°E) is distinct from the rest of the India-Eurasia continental collision, due to a wider zone of distributed deformation, oblique convergence across two orthogonal plate boundaries and near absence of foreland basin sedimentary strata. To understand the seismotectonics of this region we study the spatial distribution and source mechanism of earthquakes originating within Eastern Himalaya, northeast India and Indo-Burman Convergence Zone (IBCZ). We compute focal mechanism of 32 moderate-to-large earthquakes (mb >=5.4) by modeling teleseismic P- and SH-waveforms, from GDSN stations, using least-squares inversion algorithm; and 7 small-to-moderate earthquakes (3.5<= mb <5.4) by modeling local P- and S-waveforms, from the NorthEast India Telemetered Network, using non-linear grid search algorithm. We also include source mechanisms from previous studies, either computed by waveform inversion or by first motion polarity from analog data. Depth distribution of modeled earthquakes reveal that the seismogenic layer beneath northeast India is ~45km thick. From source mechanisms we observe that moderate earthquakes in northeast India are spatially clustered in five zones with distinct mechanisms: (a) thrust earthquakes within the Eastern Himalayan wedge, on north dipping low angle faults; (b) thrust earthquakes along the northern edge of Shillong Plateau, on high angle south dipping fault; (c) dextral strike-slip earthquakes along Kopili fault zone, between Shillong Plateau and Mikir Hills, extending southeast beneath Naga Fold belts; (d) dextral strike-slip earthquakes within Bengal Basin, immediately south of Shillong Plateau; and (e) deep focus (>50 km) thrust earthquakes within IBCZ. Combining with GPS geodetic observations, it is evident that the N20E convergence between India and Tibet is accommodated as elastic strain both within eastern Himalaya and regions surrounding the Shillong Plateau. We hypothesize that the strike-slip earthquakes south of the Plateau occur on re-activated continental rifts paralleling the Eocene hinge zone. Distribution of earthquake hypocenters across the IBCZ reveal active subduction of the Indian plate beneath Burma micro-plate.

Joint inversion of teleseismic body-waves and geodetic data for the Mw6.8 aftershock of the Balochistan earthquake with refined epicenter location

NASA Astrophysics Data System (ADS)

Wei, S.; Wang, T.; Jonsson, S.; Avouac, J. P.; Helmberger, D. V.

2014-12-01

Aftershocks of the 2013 Balochistan earthquake are mainly concentrated along the northeastern end of the mainshock rupture despite of much larger coseismic slip to the southwest. The largest event among them is an Mw6.8 earthquake which occurred three days after the mainshock. A kinematic slip model of the mainshock was obtained by joint inversion of the teleseismic body-waves and horizontal static deformation field derived from remote sensing optical and SAR data, which is composed of seven fault segments with gradually changing strikes and dips [Avouac et al., 2014]. The remote sensing data provide well constraints on the fault geometry and spatial distribution of slip but no timing information. Meanwhile, the initiation of the teleseismic waveform is very sensitive to fault geometry of the epicenter segment (strike and dip) and spatial slip distribution but much less sensitive to the absolute location of the epicenter. The combination of the two data sets allows a much better determination of the absolute epicenter location, which is about 25km to the southwest of the NEIC epicenter location. The well located mainshock epicenter is used to establish path calibrations for teleseismic P-waves, which are essential for relocating the Mw6.8 aftershock. Our grid search shows that the refined epicenter is located right at the northeastern end of the mainshock rupture. This is confirmed by the SAR offsets calculated from images acquired after the mainshock. The azimuth and range offsets display a discontinuity across the rupture trace of the mainshock. Teleseismic only and static only, as well as joint inversions all indicate that the aftershock ruptured an asperity with 25km along strike and range from 8km to 20km in depth. The earthquake was originated in a positive Coulomb stress change regime due to the mainshock and has complementary slip distribution to the mainshock rupture at the northeastern end, suggesting that the entire seismic generic zone in the crust was ruptured during the earthquake sequence.

Coseismic temporal changes of slip direction: the effect of absolute stress on dynamic rupture

USGS Publications Warehouse

Guatteri, Mariagiovanna; Spudich, P.

1998-01-01

We investigate the dynamics of rupture at low-stress level. We show that one main difference between the dynamics of high- and low-stress events is the amount of coseismic temporal rake rotation occurring at given points on the fault. Curved striations on exposed fault surfaces and earthquake dislocation models derived from ground-motion inversion indicate that the slip direction may change with time at a point on the fault during dynamic rupture. We use a 3D boundary integral method to model temporal rake variations during dynamic rupture propagation assuming a slip-weakening friction law and isotropic friction. The points at which the slip rotates most are characterized by an initial shear stress direction substantially different from the average stress direction over the fault plane. We show that for a given value of stress drop, the level of initial shear stress (i.e., the fractional stress drop) determines the amount of rotation in slip direction. We infer that seismic events that show evidence of temporal rake rotations are characterized by a low initial shear-stress level with spatially variable direction on the fault (possibly due to changes in fault surface geometry) and an almost complete stress drop.Our models motivate a new interpretation of curved and cross-cutting striations and put new constraints on their analysis. The initial rake is in general collinear with the initial stress at the hypocentral zone, supporting the assumptions made in stress-tensor inversion from first-motion analysis. At other points on the fault, especially away from the hypocenter, the initial slip rake may not be collinear with the initial shear stress, contradicting a common assumption of structural geology. On the other hand, the later part of slip in our models is systematically more aligned with the average stress direction than the early slip. Our modeling suggests that the length of the straight part of curved striations is usually an upper bound of the slip-weakening distance if this parameter is uniform over the fault plane, and the direction of the late part of slip of curved striations should have more weight in the estimate of initial stress direction.

Integrated characterization of the geologic framework of a contaminated site in West Trenton, New Jersey

USGS Publications Warehouse

Ellefsen, Karl J.; Burton, William C.; Lacombe, Pierre J.

2012-01-01

Fractured sedimentary bedrock and groundwater at the former Naval Air Warfare Center in West Trenton, New Jersey (United States of America) are contaminated with chlorinated solvents. Predicting contaminant migration or removing the contaminants requires an understanding of the geology. Consequently, the geologic framework near the site was characterized with four different methods having different spatial scales: geologic field mapping, analyses of bedrock drill core, analyses of soil and regolith, and S-wave refraction surveys. A fault zone is in the southeast corner of the site and separates two distinct sedimentary formations; the fault zone dips (steeply) southeasterly, strikes northeasterly, and extends at least 550 m along its strike direction. Drill core from the fault zone is extensively brecciated and includes evidence of tectonic contraction. Approximately 300 m east of this fault zone is another fault zone, which offsets the contact between the two sedimentary formations. The S-wave refraction surveys identified both fault zones beneath soil and regolith and thereby provided constraints on their lateral extent and location.

The 2014 update to the National Seismic Hazard Model in California

USGS Publications Warehouse

Powers, Peter; Field, Edward H.

2015-01-01

The 2014 update to the U. S. Geological Survey National Seismic Hazard Model in California introduces a new earthquake rate model and new ground motion models (GMMs) that give rise to numerous changes to seismic hazard throughout the state. The updated earthquake rate model is the third version of the Uniform California Earthquake Rupture Forecast (UCERF3), wherein the rates of all ruptures are determined via a self-consistent inverse methodology. This approach accommodates multifault ruptures and reduces the overprediction of moderate earthquake rates exhibited by the previous model (UCERF2). UCERF3 introduces new faults, changes to slip or moment rates on existing faults, and adaptively smoothed gridded seismicity source models, all of which contribute to significant changes in hazard. New GMMs increase ground motion near large strike-slip faults and reduce hazard over dip-slip faults. The addition of very large strike-slip ruptures and decreased reverse fault rupture rates in UCERF3 further enhances these effects.

Superficial simplicity of the 2010 El Mayorg-Cucapah earthquake of Baja California in Mexico

USGS Publications Warehouse

Wei, S.; Fielding, E.; Leprince, S.; Sladen, A.; Avouac, J.-P.; Helmberger, D.; Hauksson, E.; Chu, R.; Simons, M.; Hudnut, K.; Herring, T.; Briggs, R.

2011-01-01

The geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation, propagation and arrest of seismic ruptures1-6. The fault system that runs from southern California into Mexico is a simple strike-slip boundary: the west side of California and Mexico moves northwards with respect to the east. However, the Mw 7.2 2010 El Mayorg-Cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike-slip fault. Here we use geodetic, remote-sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake. We find that the earthquake produced a straight 120-km-long fault trace that cut through the Cucapah mountain range and across the Colorado River delta. However, at depth, the fault is made up of two different segments connected by a small extensional fault. Both segments strike N130 ??E, but dip in opposite directions. The earthquake was initiated on the connecting extensional fault and 15s later ruptured the two main segments with dominantly strike-slip motion. We show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves. We conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone. ?? 2011 Macmillan Publishers Limited. All rights reserved.

Energy Analysis of Decoders for Rakeness-Based Compressed Sensing of ECG Signals.

PubMed

Pareschi, Fabio; Mangia, Mauro; Bortolotti, Daniele; Bartolini, Andrea; Benini, Luca; Rovatti, Riccardo; Setti, Gianluca

2017-12-01

In recent years, compressed sensing (CS) has proved to be effective in lowering the power consumption of sensing nodes in biomedical signal processing devices. This is due to the fact the CS is capable of reducing the amount of data to be transmitted to ensure correct reconstruction of the acquired waveforms. Rakeness-based CS has been introduced to further reduce the amount of transmitted data by exploiting the uneven distribution to the sensed signal energy. Yet, so far no thorough analysis exists on the impact of its adoption on CS decoder performance. The latter point is of great importance, since body-area sensor network architectures may include intermediate gateway nodes that receive and reconstruct signals to provide local services before relaying data to a remote server. In this paper, we fill this gap by showing that rakeness-based design also improves reconstruction performance. We quantify these findings in the case of ECG signals and when a variety of reconstruction algorithms are used either in a low-power microcontroller or a heterogeneous mobile computing platform.

New Sections and Fossils From the Southern Bighorn Basin, Wyoming Document Faunal Turnover During the PETM

NASA Astrophysics Data System (ADS)

Bloch, J. I.; Boyer, D. M.; Strait, S. G.; Wing, S. L.

2004-12-01

Though earliest Eocene (Wa-0) mammals are known from the southern Bighorn Basin, late Paleocene mammals are not. Recent discovery of latest Paleocene mammals in section with new Wa-0 faunas and floras at Cabin Fork allows for the first studies of terrestrial biotic change across the Paleocene-Eocene boundary interval outside of the northern Bighorn Basin. A differential GPS was used to map the area and provide a framework for high-resolution biostratigraphy. Least squares interpolation of bedding planes from points marking outcrop of beds reveals high r2 coefficients (0.97-0.98). This indicates that small scale folding is minimal and bed traces are smoothly planar. Beds in the study area strike N-NW (355° ) and dip shallowly W-SW (<1.0° ). Smaller scale undulations are present: to the NE beds strike NW and dip to the SW (342° /1.0° ) whereas those to the SW strike NE and dip NW (5° /1.0° ). Shallow dips allow us to approximate stratigraphic thickness with elevation. Paleocene mammals, including diagnostic Clarkforkian land-mammal age indicators, Aletodon gunnelli, Apheliscus nitidus, and Haplomylus simpsoni, were found in a ferruginous, grit-pebble conglomerate at the base of a channel sand at the top of the Fort Union Fm. The fossiliferous horizon is extensive and has produced over 200 specimens from more than 60 sites for which positions have been determined with sub-meter accuracy. Absence of Plesiadapis cookei and Hyracotherium spp., together with high relative abundance of Phenacodus and Ectocion, indicate this fauna is latest Clarkforkian (Phenacodus-Ectocion Range Zone, Cf-3). Earliest Eocene mammals, including diagnostic Wa-0 taxa Arfia junnei, Copecion davisi, Hyracotherium sandrae, and Diacodexis ilicis, are represented by more than 233 specimens from 70 sites at three levels in the lowest Willwood Formation. The lowest fossils come from paleosols and claygall accumulations in stringer sands approximately 3 meters above the top of the channel sand that is the top of the Fort Union Formation, and 8 meters above the Clarkforkian localities. The second level is a fossiliferous paleosol 6-8 meters above the top of the channel sand. The third level is a paleosol fossil accumulation approximately 22 meters above the top of the channel sand and 15 meters below a large and persistent red paleosol informally called ?Big Red.? In the Cabin Fork area, Big Red produces mammal fossils, including Cardiolophus, that have been used to define the succeeding Wa-1 faunal zone (although some Wa-0 taxa have been recovered from Big Red approximately 6 km to the east). The Wa-0 interval in the Cabin Fork area is 38-40 meters thick and bounded by distinct Cf-3 and Wa-1 faunas. Preliminary analyses of fossils from the Cabin Fork section show that the faunal shift marking the PETM was very similar to that seen in the northern Bighorn Basin. This suggests that previously documented differences between Wa-0 mammalian faunas in the southern and northern Bighorn Basin, including the absence of certain diagnostic Wa-0 taxa in the south, may reflect local sampling variation or artifacts rather than regional variation in faunal composition.

The structures, stratigraphy and evolution of the Gulf of Corinth rift, Greece

NASA Astrophysics Data System (ADS)

Taylor, Brian; Weiss, Jonathan R.; Goodliffe, Andrew M.; Sachpazi, Maria; Laigle, Mireille; Hirn, Alfred

2011-06-01

A multichannel seismic and bathymetry survey of the central and eastern Gulf of Corinth (GoC), Greece, reveals the offshore fault geometry, seismic stratigraphy and basin evolution of one of Earths most active continental rift systems. Active, right-stepping, en-echelon, north-dipping border faults trend ESE along the southern Gulf margin, significantly overlapping along strike. The basement offsets of three (Akrata-Derveni, Sithas and Xylocastro) are linked. The faults are biplanar to listric: typically intermediate angle (˜35° in the centre and 45-48° in the east) near the surface but decreasing in dip and/or intersecting a low- or shallow-angle (15-20° in the centre and 19-30° in the east) curvi-planar reflector in the basement. Major S-dipping border faults were active along the northern margin of the central Gulf early in the rift history, and remain active in the western Gulf and in the subsidiary Gulf of Lechaio, but unlike the southern border faults, are without major footwall uplift. Much of the eastern rift has a classic half-graben architecture whereas the central rift has a more symmetric w- or u-shape. The narrower and shallower western Gulf that transects the >40-km-thick crust of the Hellenides is associated with a wider distribution of overlapping high-angle normal faults that were formerly active on the Peloponnesus Peninsula. The easternmost sector includes the subsidiary Gulfs of Lechaio and Alkyonides, with major faults and basement structures trending NE, E-W and NW. The basement faults that control the rift architecture formed early in the rift history, with little evidence (other than the Vrachonisida fault along the northern margin) in the marine data for plan view evolution by subsequent fault linkage. Several have maximum offsets near one end. Crestal collapse graben formed where the hanging wall has pulled off the steeper onto the shallower downdip segment of the Derveni Fault. The dominant strikes of the Corinth rift faults gradually rotate from 090-120° in the basement and early rift to 090-100° in the latest rift, reflecting a ˜10° rotation of the opening direction to the 005° presently measured by GPS. The sediments include a (locally >1.5-km-) thick, early-rift section, and a late-rift section (also locally >1.5-km-thick) that we subdivide into three sequences and correlate with seven 100-ka glacio-eustatic cycles. The Gulf depocentre has deepened through time (currently >700 mbsl) as subsidence has outpaced sedimentation. We measure the minimum total horizontal extension across the central and eastern Gulf as varying along strike between 4 and 10 km, and estimate full values of 6-11 km. The rift evolution is strongly influenced by the inherited basement fabric. The regional NNW structural fabric of the Hellenic nappes changes orientation to ESE in the Parnassos terrane, facilitating the focused north-south extension observed offshore there. The basement-penetrating faults lose seismic reflectivity above the 4-14-km-deep seismogenic zone. Multiple generations and dips of normal faults, some cross-cutting, accommodate extension beneath the GoC, including low-angle (15-20°) interfaces in the basement nappes. The thermally cool forearc setting and cross-orogen structures unaccompanied by magmatism make this rift a poor analogue and unlikely precursor for metamorphic core complex formation.

P wave anisotropic tomography of the Alps

NASA Astrophysics Data System (ADS)

Hua, Yuanyuan; Zhao, Dapeng; Xu, Yixian

2017-06-01

The first tomographic images of P wave azimuthal and radial anisotropies in the crust and upper mantle beneath the Alps are determined by joint inversions of arrival time data of local earthquakes and teleseismic events. Our results show the south dipping European plate with a high-velocity (high-V) anomaly beneath the western central Alps and the north dipping Adriatic plate with a high-V anomaly beneath the Eastern Alps, indicating that the subduction polarity changes along the strike of the Alps. The P wave azimuthal anisotropy is characterized by mountain chain-parallel fast-velocity directions (FVDs) in the western central Alps and NE-SW FVDs in the Eastern Alps, which may be caused by mantle flow induced by the slab subductions. Our results reveal a negative radial anisotropy (i.e., Vph < Vpv) within the subducting slabs and a positive radial anisotropy (i.e., Vph > Vpv) in the low-velocity mantle wedge, which may reflect the subvertical plate subduction and its induced mantle flow. The results of anisotropic tomography provide important new information on the complex mantle structure and dynamics of the Alps and adjacent regions.

Geological and vegetational applications of Shuttle Imaging Radar-B, Mineral County, Nevada

NASA Technical Reports Server (NTRS)

Borengasser, M. X.; Kleiner, E. F.; Peterson, F. F.; Klieforth, H.; Vreeland, P.

1988-01-01

Multiple-incidence angle and multi-azimuth radar data were acquired from a Shuttle platform over test sites in Nevada in October 1984. An attempt was made to correlate these data with ground features for the purpose of evaluating the use of such data for geological and vegetational assessment. Standard ecological parameters with respect to the flora (community composition, dominance, and relative cover) were recorded in the field at the time of overflight. Although a total of 33 species representing 11 plant families were recognized, and plant cover ranged from 13 to 26 percent, radar data could not be used to separate plant communities. The signal return is more a function of abiotic conditions than vegetative characteristics. Illumination geometry plays an important role in the ability to detect strike-slip and dip-slip faults. Local incidence angle is the most important parameter, and SIR-B data takes with small incidence angles are superior for identifying certain styles of faulting. Look direction is critical for detecting faults with a dip-slip component. New structural features were not observed. Problems with radar antenna power and recording significantly affected data quality.

A teleseismic analysis of the New Brunswick earthquake of January 9, 1982.

USGS Publications Warehouse

Choy, G.L.; Boatwright, J.; Dewey, J.W.; Sipkin, S.A.

1983-01-01

The analysis of the New Brunswick earthquake of January 9, 1982, has important implications for the evaluation of seismic hazards in eastern North America. Although moderate in size (mb, 5.7), it was well-recorded teleseismically. Source characteristics of this earthquake have been determined from analysis of data that were digitally recorded by the Global Digital Seismography Network. From broadband displacement and velocity records of P waves, we have obtained a dynamic description of the rupture process as well as conventional static properties of the source. The depth of the hypocenter is estimated to be 9km from depth phases. The focal mechanism determined from the broadband data corresponds to predominantly thrust faulting. From the variation in the waveforms the direction of slip is inferred to be updip on a west dipping NNE striking fault plane. The steep dip of the inferred fault plane suggests that the earthquake occurred on a preexisting fault that was at one time a normal fault. From an inversion of body wave pulse durations, the estimated rupture length is 5.5km.-from Authors

Relationships among in-situ stress, fractures and faults, and fluid flow: Monterey formation, Santa Maria Basin, California

USGS Publications Warehouse

Finkbeiner, T.; Barton, C.A.; Zoback, M.D.

1997-01-01

We used borehole televiewer (BHTV) data from four wells within the onshore and offshore Santa Maria basin, California, to investigate the relationships among fracture distribution, orientation, and variation with depth and in-situ stress. Our analysis of stress-induced well-bore breakouts shows a uniform northeast maximum horizontal stress (SH max) orientation in each well. This direction is consistent with the SH max direction determined from well-bore breakouts in other wells in this region, the northwest trend of active fold axes, and kinematic inversion of nearby earthquake focal plane mechanisms. In contrast to the uniformity of the stress field, fracture orientation, dip, and frequency vary considerably from well to well and within each well. With depth, fractures can be divided into distinct subsets on the basis of fracture frequency and orientation, which correlate with changes of lithology and physical properties. Although factors such as tectonic history, diagenesis, and structural variations obviously have influenced fracture distribution, integration of the in-situ stress and fracture data sets indicates that many of the fractures, faults, and bedding planes are active, small-scale strike-slip and reverse faults in the current northeast-trending transpressive stress field. In fact, we observed local breakout rotations in the wells, providing kinematic evidence for recent shear motion along fracture and bedding-parallel planes. Only in the onshore well do steeply dipping fractures strike parallel to SHmax. Drill-stem tests from two of the offshore wells indicate that formation permeability is greatly enhanced in sections of the wells where fractures are favorably oriented for shear failure in the modern stress field. Thus, relatively small-scale active faults provide important conduits along which fluids migrate.

Estimation of groundwater flow directions and the tensor of hydraulic conductivity in crystalline massif rocks using information from surface structural geology and mining exploration boreholes

NASA Astrophysics Data System (ADS)

Florez, C.; Romero, M. A.; Ramirez, M. I.; Monsalve, G.

2013-05-01

In the elaboration of a hydrogeological conceptual model in regions of mining exploration where there is significant presence of crystalline massif rocks., the influence of physical and geometrical properties of rock discontinuities must be evaluated. We present the results of a structural analysis of rock discontinuities in a region of the Central Cordillera of Colombia (The upper and middle Bermellon Basin) in order to establish its hydrogeological characteristics for the improvement of the conceptual hydrogeological model for the region. The geology of the study area consists of schists with quartz and mica and porphyritic rocks, in a region of high slopes with a nearly 10 m thick weathered layer. The main objective of this research is to infer the preferential flow directions of groundwater and to estimate the tensor of potential hydraulic conductivity by using surface information and avoiding the use of wells and packer tests. The first step of our methodology is an analysis of drainage directions to detect patterns of structural controls in the run-off; after a field campaign of structural data recollection, where we compile information of strike, dip, continuity, spacing, roughness, aperture and frequency, we built equal area hydro-structural polar diagrams that indicate the potential directions for groundwater flow. These results are confronted with records of Rock Quality Designation (RQD) that have been systematically taken from several mining exploration boreholes in the area of study. By using all this information we estimate the potential tensor of hydraulic conductivity from a cubic law, obtaining the three principal directions with conductivities of the order of 10-5 and 10-6 m/s; the more conductive joint family has a NE strike with a nearly vertical dip.

Three-Dimensional Variation of the Slab Geometry Along Strike and Along Dip in the Cascadia Subduction

NASA Astrophysics Data System (ADS)

Gao, H.

2017-12-01

The crust and upper mantle seismic structure, spanning from the Juan de Fuca and Gorda spreading centers to the Cascade arc, is imaged with full-wave propagation simulation and ambient noise tomography. To retrieve Rayleigh-wave Empirical Green's Functions between station pairs, we process the vertical component of continuous seismic data recorded between 2004 and 2015 by about 800 stations, including three offshore seismic networks (the Cascadia Initiative Amphibious Array, the Blanco Transform OBS experiment, and the Gorda Deformation Zone OBS experiment) and all available broadband inland stations. The spreading centers have anomalously low shear-wave velocity beneath the oceanic lithosphere. Around the Cobb axial seamount, we observe a low velocity anomaly underlying a relatively thin oceanic lithosphere, indicating its influence on the Juan de Fuca ridge. The tomographic imaging reveals great details of the seismic feature of the oceanic lithosphere prior to and after subduction, which varies significantly along strike and along dip. On average, the thickness of the oceanic lithosphere is about 30-45 km. The Juan de Fuca lithosphere appears to be relatively thin around the ridge, especially beneath the Cobb axial seamount, and then gradually thickens with increasing distance from the ridge. The thickness of the Gorda plate appears to be constant, which is probably due to the small size of the subduction system from formation to subduction. It is noteworthy that the oceanic plate is imaged relatively weaker beneath the trench compared to other parts of the plate. We suggest that in addition to the possible hydration of the oceanic mantle lithosphere, other mechanisms must be considered to explain the observed seismic feature around the trench. Further landward, very low velocity anomalies are observed above the plate interface along the Cascade forearc, indicative of subducted sediments.

Analysis of fractures intersecting Kahi Puka Well 1 and its relation to the growth of the island of Hawaii

USGS Publications Warehouse

Morin, R.H.; Paillet, Frederick L.

1996-01-01

As part of the Hawaii Scientific Drilling Project, Kahi Puka Well 1 penetrated about 275 m of Mauna Loa basalts overlying a sequence of Mauna Kea flow units as it was drilled and cored to a total depth of 1053 m below land surface. A borehole televiewer (BHTV) was run in most of the well in successive stages prior to casing in order to obtain magnetically oriented acoustic images of the borehole wall. A total of 283 individual fractures were identified from this log and characterized in terms of strike and dip. These data are divided into three vertical sections based upon age and volcanic source, and lower hemisphere stereographic plots identify two predominant, subparallel fracture subsets common to each section. Assuming that most of the steeply dipping fractures observed in the BHTV log are tensile features generated within basalt flows during deposition and cooling, this fracture information can be combined with models of the evolution of the island of Hawaii to investigate the depositional history of these Mauna Loa and Mauna Kea basalts over the past 400 kyr. The directions of high-angle fractures appear to be generally parallel to topography or to the coastline at the time of deposition, as is supported by surface mapping of modern flows. Consequently, an overall counterclockwise rotation of about 75?? in the strike of these fractures from the bottom to the top of the well represents a systematic change in depositional slope direction over time. We attribute the observed rotation in the orientations of the two predominant fracture subsets over the past 400 kyr to changes in the configurations of volcanic sources during shield building and to the structural interference of adjacent volcanoes that produces shifts in topographic patterns.

Analysis of fractures intersecting Kahi Puka Well 1 and its relation to the growth of the island of Hawaii

NASA Astrophysics Data System (ADS)

Morin, Roger H.; Paillet, Frederick L.

1996-05-01

As part of the Hawaii Scientific Drilling Project, Kahi Puka Well 1 penetrated about 275 m of Mauna Loa basalts overlying a sequence of Mauna Kea flow units as it was drilled and cored to a total depth of 1053 m below land surface. A borehole televiewer (BHTV) was run in most of the well in successive stages prior to casing in order to obtain magnetically oriented acoustic images of the borehole wall. A total of 283 individual fractures were identified from this log and characterized in terms of strike and dip. These data are divided into three vertical sections based upon age and volcanic source, and lower hemisphere stereographic plots identify two predominant, subparallel fracture subsets common to each section. Assuming that most of the steeply dipping fractures observed in the BHTV log are tensile features generated within basalt flows during deposition and cooling, this fracture information can be combined with models of the evolution of the island of Hawaii to investigate the depositional history of these Mauna Loa and Mauna Kea basalts over the past 400 kyr. The directions of high-angle fractures appear to be generally parallel to topography or to the coastline at the time of deposition, as is supported by surface mapping of modern flows. Consequently, an overall counterclockwise rotation of about 75° in the strike of these fractures from the bottom to the top of the well represents a systematic change in depositional slope direction over time. We attribute the observed rotation in the orientations of the two predominant fracture subsets over the past 400 kyr to changes in the configurations of volcanic sources during shield building and to the structural interference of adjacent volcanoes that produces shifts in topographic patterns.

San Antonio relay ramp: Area of stratal continuity between large-displacement barrier faults of the Edwards aquifer and Balcones fault zone, central Texas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, E.W.

1996-09-01

The San Antonio relay ramp, a gentle southwest-dipping monocline, formed between the tips of two en echelon master faults having maximum throws of >240 in. Structural analysis of this relay ramp is important to studies of Edwards aquifer recharge and ground-water flow because the ramp is an area of relatively good stratal continuity linking the outcrop belt recharge zone and unconfined aquifer with the downdip confined aquifer. Part of the relay ramp lies within the aquifer recharge zone and is crossed by several southeast-draining creeks, including Salado, Cibolo, and Comal Creeks, that supply water to the ramp recharge area. Thismore » feature is an analog for similar structures within the aquifer and for potential targets for hydrocarbons in other Gulf Coast areas. Defining the ramp is an {approximately}13-km-wide right step of the Edwards Group outcrop belt and the en echelon master faults that bound the ramp. The master faults strike N55-75{degrees}E, and maximum displacement exceeds the {approximately}165-m thickness of the Edwards Group strata. The faults therefore probably serve as barriers to Edwards ground-water flow. Within the ramp, tilted strata gently dip southwestward at {approximately}5 m/km, and the total structural relief along the ramp`s southwest-trending axis is <240 in. The ramp`s internal framework is defined by three fault blocks that are {approximately}4 to {approximately}6 km wide and are bound by northeast-striking faults having maximum throws between 30 and 150 m. Within the fault blocks, local areas of high fracture permeability may exist where smaller faults and joints are well connected.« less

Stress tensor and focal mechanisms in the Dead Sea basin

NASA Astrophysics Data System (ADS)

Hofstetter, A.; Dorbath, C.; Dorbath, L.; Braeuer, B.; Weber, M. H.

2015-12-01

We use the recorded seismicity, confined to the Dead Sea basin and its boundaries, by the Dead Sea Integrated Research (DESIRE) portable seismic network and the Israel and Jordan permanent seismic networks for studying the mechanisms of earthquakes that occurred in the Dead Sea basin. The observed seismicity in the Dead Sea basin was divided into 9 regions according to the spatial distribution of the earthquakes and the known tectonic features. The large number of recording stations and the good station distribution allowed the reliable determinations of 494 earthquake focal mechanisms. For each region, based on the inversion of the observed polarities of the earthquakes, we determine the focal mechanisms and the associated stress tensor. For 159 earthquakes out of the 494 mechanisms we could determine compatible fault planes. On the eastern side, the focal mechanisms are mainly strike-slip mechanism with nodal planes in the N-S and E-W directions. The azimuths of the stress axes are well constrained presenting minimal variability in the inversion of the data, which is in good agreement with the Arava fault on the eastern side of the Dead Sea basin and what we had expected from the regional geodynamics. However, larger variabilities of the azimuthal and dip angles are observed on the western side of the basin. Due to the wider range of azimuths of the fault planes, we observe the switching of sigma1 and sigma2 or the switching of sigma2 and sigma3as major horizontal stress directions. This observed switching of stress axes allows having dip-slip and normal mechanisms in a region that is dominated by strike-slip motion.

Potential for a large earthquake near Los Angeles inferred from the 2014 La Habra earthquake.

PubMed

Donnellan, Andrea; Grant Ludwig, Lisa; Parker, Jay W; Rundle, John B; Wang, Jun; Pierce, Marlon; Blewitt, Geoffrey; Hensley, Scott

2015-09-01

Tectonic motion across the Los Angeles region is distributed across an intricate network of strike-slip and thrust faults that will be released in destructive earthquakes similar to or larger than the 1933  M 6.4 Long Beach and 1994  M 6.7 Northridge events. Here we show that Los Angeles regional thrust, strike-slip, and oblique faults are connected and move concurrently with measurable surface deformation, even in moderate magnitude earthquakes, as part of a fault system that accommodates north-south shortening and westerly tectonic escape of northern Los Angeles. The 28 March 2014 M 5.1 La Habra earthquake occurred on a northeast striking, northwest dipping left-lateral oblique thrust fault northeast of Los Angeles. We present crustal deformation observation spanning the earthquake showing that concurrent deformation occurred on several structures in the shallow crust. The seismic moment of the earthquake is 82% of the total geodetic moment released. Slip within the unconsolidated upper sedimentary layer may reflect shallow release of accumulated strain on still-locked deeper structures. A future M 6.1-6.3 earthquake would account for the accumulated strain. Such an event could occur on any one or several of these faults, which may not have been identified by geologic surface mapping.

Rapid Estimates of Rupture Extent for Large Earthquakes Using Aftershocks

NASA Astrophysics Data System (ADS)

Polet, J.; Thio, H. K.; Kremer, M.

2009-12-01

The spatial distribution of aftershocks is closely linked to the rupture extent of the mainshock that preceded them and a rapid analysis of aftershock patterns therefore has potential for use in near real-time estimates of earthquake impact. The correlation between aftershocks and slip distribution has frequently been used to estimate the fault dimensions of large historic earthquakes for which no, or insufficient, waveform data is available. With the advent of earthquake inversions that use seismic waveforms and geodetic data to constrain the slip distribution, the study of aftershocks has recently been largely focused on enhancing our understanding of the underlying mechanisms in a broader earthquake mechanics/dynamics framework. However, in a near real-time earthquake monitoring environment, in which aftershocks of large earthquakes are routinely detected and located, these data may also be effective in determining a fast estimate of the mainshock rupture area, which would aid in the rapid assessment of the impact of the earthquake. We have analyzed a considerable number of large recent earthquakes and their aftershock sequences and have developed an effective algorithm that determines the rupture extent of a mainshock from its aftershock distribution, in a fully automatic manner. The algorithm automatically removes outliers by spatial binning, and subsequently determines the best fitting “strike” of the rupture and its length by projecting the aftershock epicenters onto a set of lines that cross the mainshock epicenter with incremental azimuths. For strike-slip or large dip-slip events, for which the surface projection of the rupture is recti-linear, the calculated strike correlates well with the strike of the fault and the corresponding length, determined from the distribution of aftershocks projected onto the line, agrees well with the rupture length. In the case of a smaller dip-slip rupture with an aspect ratio closer to 1, the procedure gives a measure of the rupture extent and dimensions, but not necessarily the strike. We found that using standard earthquake catalogs, such as the National Earthquake Information Center catalog, we can constrain the rupture extent, rupture direction, and in many cases the type of faulting, of the mainshock with the aftershocks that occur within the first hour after the mainshock. However, this data may not be currently available in near real-time. Since our results show that these early aftershock locations may be used to estimate first order rupture parameters for large global earthquakes, the near real-time availability of these data would be useful for fast earthquake damage assessment.

The Mw 5.8 Mineral, Virginia, earthquake of August 2011 and aftershock sequence: constraints on earthquake source parameters and fault geometry

USGS Publications Warehouse

McNamara, Daniel E.; Benz, H.M.; Herrmann, Robert B.; Bergman, Eric A.; Earle, Paul; Meltzer, Anne; Withers, Mitch; Chapman, Martin

2014-01-01

The Mw 5.8 earthquake of 23 August 2011 (17:51:04 UTC) (moment, M0 5.7×1017  N·m) occurred near Mineral, Virginia, within the central Virginia seismic zone and was felt by more people than any other earthquake in United States history. The U.S. Geological Survey (USGS) received 148,638 felt reports from 31 states and 4 Canadian provinces. The USGS PAGER system estimates as many as 120,000 people were exposed to shaking intensity levels of IV and greater, with approximately 10,000 exposed to shaking as high as intensity VIII. Both regional and teleseismic moment tensor solutions characterize the earthquake as a northeast‐striking reverse fault that nucleated at a depth of approximately 7±2  km. The distribution of reported macroseismic intensities is roughly ten times the area of a similarly sized earthquake in the western United States (Horton and Williams, 2012). Near‐source and far‐field damage reports, which extend as far away as Washington, D.C., (135 km away) and Baltimore, Maryland, (200 km away) are consistent with an earthquake of this size and depth in the eastern United States (EUS). Within the first few days following the earthquake, several government and academic institutions installed 36 portable seismograph stations in the epicentral region, making this among the best‐recorded aftershock sequences in the EUS. Based on modeling of these data, we provide a detailed description of the source parameters of the mainshock and analysis of the subsequent aftershock sequence for defining the fault geometry, area of rupture, and observations of the aftershock sequence magnitude–frequency and temporal distribution. The observed slope of the magnitude–frequency curve or b‐value for the aftershock sequence is consistent with previous EUS studies (b=0.75), suggesting that most of the accumulated strain was released by the mainshock. The aftershocks define a rupture that extends between approximately 2–8 km in depth and 8–10 km along the strike of the fault plane. Best‐fit modeling of the geometry of the aftershock sequence defines a rupture plane that strikes N36°E and dips to the east‐southeast at 49.5°. Moment tensor solutions of the mainshock and larger aftershocks are consistent with the distribution of aftershock locations, both indicating reverse slip along a northeast–southwest striking southeast‐dipping fault plane.

Growth and linkage of the quaternary Ubrique Normal Fault Zone, Western Gibraltar Arc: role on the along-strike relief segmentation

NASA Astrophysics Data System (ADS)

Jiménez-Bonilla, Alejandro; Balanya, Juan Carlos; Exposito, Inmaculada; Diaz-Azpiroz, Manuel; Barcos, Leticia

2015-04-01

Strain partitioning modes within migrating orogenic arcs may result in arc-parallel stretching that produces along-strike structural and topographic discontinuities. In the Western Gibraltar Arc, arc-parallel stretching has operated from the Lower Miocene up to recent times. In this study, we have reviewed the Colmenar Fault, located at the SW end of the Subbetic ranges, previously interpreted as a Middle Miocene low-angle normal fault. Our results allow to identify younger normal fault segments, to analyse their kinematics, growth and segment linkage, and to discuss its role on the structural and relief drop at regional scale. The Colmenar Fault is folded by post-Serravallian NE-SW buckle folds. Both the SW-dipping fault surfaces and the SW-plunging fold axes contribute to the structural relief drop toward the SW. Nevertheless, at the NW tip of the Colmenar Fault, we have identified unfolded normal faults cutting quaternary soils. They are grouped into a N110˚E striking brittle deformation band 15km long and until 3km wide (hereafter Ubrique Normal Fault Zone; UNFZ). The UNFZ is divided into three sectors: (a) The western tip zone is formed by normal faults which usually dip to the SW and whose slip directions vary between N205˚E and N225˚E. These segments are linked to each other by left-lateral oblique faults interpreted as transfer faults. (b) The central part of the UNFZ is composed of a single N115˚E striking fault segment 2,4km long. Slip directions are around N190˚E and the estimated throw is 1,25km. The fault scarp is well-conserved reaching up to 400m in its central part and diminishing to 200m at both segment terminations. This fault segment is linked to the western tip by an overlap zone characterized by tilted blocks limited by high-angle NNE-SSW and WNW-ESE striking faults interpreted as "box faults" [1]. (c) The eastern tip zone is formed by fault segments with oblique slip which also contribute to the downthrown of the SW block. This kinematic pattern seems to be related to other strike-slip fault systems developed to the E of the UNFZ. The structural revision together with updated kinematic data suggest that the Colmenar Fault is cut and downthrown by a younger normal fault zone, the UNFZ, which would have contributed to accommodate arc-parallel stretching until the Quaternary. This stretching provokes along-strike relief segmentation, being the UNFZ the main fault zone causing the final drop of the Subbetic ranges towards the SW within the Western Gibraltar Arc. Our results show displacement variations in each fault segment of the UNFZ, diminishing to their tips. This suggests fault segment linkage finally evolved to build the nearly continuous current fault zone. The development of current large through-going faults linked inside the UNFZ is similar to those ones simulated in some numerical modelling of rift systems [2]. Acknowledgements: RNM-415 and CGL-2013-46368-P [1]Peacock, D.C.P., Knipe, R.J., Sanderson, D.J., 2000. Glossary of normal faults. Journal Structural Geology, 22, 291-305. [2]Cowie, P.A., Gupta, S., Dawers, N.H., 2000. Implications of fault array evolution for synrift depocentre development: insights from a numerical fault growth model. Basin Research, 12, 241-261.

The role of rock anisotropy in developing non-Andersonian faults: staircase trajectories for strike-slip faults

NASA Astrophysics Data System (ADS)

Barchi, M. R.; Collettini, C.; Lena, G.

2012-04-01

Thrust and normal faults affecting mechanically heterogeneous multilayers often show staircase trajectories, where flat segments follow less competent units. Within flat segments the initiation/reactivation angle, θ, which is the angle that the fault makes with the σ1 direction, is different from that predicted by the Andersonian theory. This suggests that fault trajectory is mainly controlled by rock anisotropy instead of frictional properties of the material. Our study areas are located in the Umbria-Marche fold-thrust belt, within the Northern Apennines of Italy. The area is characterized by a lithologically complex multilayer, about 2000 m thick, consisting of alternated competent (mainly calcareous) and less competent (marls or evaporites) units. At the outcrop scale, some units show a significant mechanical layering, consisting of alternated limestones and shales. Due to the complex tectonic evolution of the Apennines, well developed sets of conjugate normal, thrust and strike-slip faults are exposed in the region. The study outcrop, Candigliano Gourge, is characterized by steep (dip > 60°) NE dipping beds, affected by conjugate sets of strike-slip faults, exposed in the eastern limb of a NE verging anticline. The faults develop within the Marne a Fucoidi Fm., a Cretaceous sedimentary unit, about 70 m thick, made of competent calcareous beds (about 20 cm thick), separated by marly beds (1-20 cm thick). The conjugate strike-slip faults are formed after the major folding phase: in fact the strike-slip faults cut both minor folds and striated bedding surfaces, related to syn-folding flexural slip. Faults show marked staircase trajectories, with straight segments almost parallel to the marly horizons and ramps cutting through the calcareous layers. Slip along these faults induces local block rotation of the competent strata, dilational jogs (pull-aparts), extensional duplexes and boudinage of the competent layers, while marly levels are strongly laminated. In order to reconstruct the σ1 direction, calcite veins syntectonic to strike-slip faulting, have been used to constrain the σ1-σ2 plane: fixing the σ2 direction at the conjugate fault intersection, the σ1 is oriented N15°, forming an angle of about 70° with the bedding direction. Once constrained the σ1 direction, we have calculated the θ angle that is comprised between 40° and 55°, resulting therefore larger than expected from Andersonian theory, i.e. 22°-32° for friction coefficient in the range of 0.5-1.0. Initiation/reactivation angles, θ, as a function of the different lithologies, are less than 35° for calcareous beds, 50°-70° for the marly and clayey layers, and around 60° for the black shales. Our studies, focused on strike-slip small displacement faults, show that: 1) irrespective of the σ1 orientation, ramp and flat form along competent and less competent material respectively and 2) the overall fault orientation/initiation is at high-angle to the σ1 direction. Our results suggest that rock anisotropy and layering are one of the possible causes for faulting at high angle to the σ1 direction, i.e. fault weakness. Further studies are required to up-scale the results of our outcrop-based study to crustal scale structures.

Temporal evolution of surface rupture deduced from coseismic multi-mode secondary fractures: Insights from the October 8, 2005 (Mw 7.6) Kashmir earthquake, NW Himalaya

NASA Astrophysics Data System (ADS)

Sayab, Mohammad; Khan, Muhammad Asif

2010-10-01

Detailed rupture-fracture analyses of some of the well-studied earthquakes have revealed that the geometrical arrangement of secondary faults and fractures can be used as a geological tool to understand the temporal evolution of slip produced during the mainshock. The October 8, 2005 Mw 7.6 Kashmir earthquake, NW Himalaya, surface rupture provides an opportunity to study a complex network of secondary fractures developed on the hanging wall of the fault scarp. The main fault scarp is clearly thrust-type, rupture length is ~ 75 ± 5 km and the overall trend of the rupture is NW-SE. We present the results of our detailed structural mapping of secondary faults and fractures at 1:100 scale, on the hanging wall of the southern end of the rupture in the vicinity of the Sar Pain. Secondary ruptures can be broadly classified as two main types, 1) normal faults and, (2) right-lateral strike-slip 'Riedel' fractures. The secondary normal faults are NW-SE striking, with a maximum 3.3 meter vertical displacement and 2.5 meter horizontal displacement. Estimated total horizontal extension across the secondary normal faults is 3.1-3.5%. We propose that the bending-moment and coseismic stress relaxation can explain the formation of secondary normal faults on the hanging wall of the thrust fault. The strike-slip 'Riedel' fractures form distinct sets of tension (T) and shear fractures (R', R, Y) with right-lateral displacement. Field observations revealed that the 'Riedel' fractures (T) cut the secondary normal faults. In addition, there is kinematic incompatibility and magnitude mismatch between the secondary normal faults and strike-slip 'Riedel' fractures. The cross-cutting relationship, geometric and magnitude incoherence implies a temporal evolution of slip from dip- to strike-slip during the mainshock faulting. The interpretation is consistent with the thrust fault plane solution with minor right-lateral strike-slip component.

Strike-Slip Fault Deformation and Its Control in Hydrocarbon Trapping in Ketaling Area, Jambi Subbasin, Indonesia

NASA Astrophysics Data System (ADS)

Ramadhan, Aldis; Badai Samudra, Alexis; Jaenudin; Puji Lestari, Enik; Saputro, Julian; Sugiono; Hirosiadi, Yosi; Amrullah, Indi

2018-03-01

Geologically, Ketaling area consists of a local high considered as flexure margin of Tempino-Kenali Asam Deep in west part and graben in east part also known as East Ketaling Deep. Numerous proven plays were established in Ketaling area with reservoir in early Miocene carbonate and middle Miocene sand. This area underwent several major deformations. Faults are developed widely, yet their geometrical features and mechanisms of formation remained so far indistinct, which limited exploration activities. With new three-dimensional seismic data acquired in 2014, this area evidently interpreted as having strike-slip mechanism. The objective of this study is to examine characteristic of strike slip fault and its affect to hydrocarbon trapping in Ketaling Area. Structural pattern and characteristic of strike slip fault deformation was examined with integration of normal seismic with variance seismic attribute analysis and the mapping of Syn-rift to Post-rift horizon. Seismic flattening on 2D seismic cross section with NW-SE direction is done to see the structural pattern related to horst (paleohigh) and graben. Typical flower structure, branching strike-slip fault system and normal fault in synrift sediment clearly showed in section. An echelon pattern identified from map view as the result of strike slip mechanism. Detail structural geology analysis show the normal fault development which has main border fault in the southern of Ketaling area dipping to the Southeast-East with NE-SW lineament. These faults related to rift system in Ketaling area. NW-SE folds with reactive NE-SW fault which act as hydrocarbon trapping in the shallow zone. This polyphase tectonic formed local graben, horst and inverted structure developed a good kitchen area (graben) and traps (horst, inverted structure). Subsequently, hydrocarbon accumulation potentials such as basement fractures, inverted syn-rift deposit and shallow zone are very interesting to explore in this area.

A fast and robust method for moment tensor and depth determination of shallow seismic events in CTBT related studies.

NASA Astrophysics Data System (ADS)

Baker, Ben; Stachnik, Joshua; Rozhkov, Mikhail

2017-04-01

International Data Center is required to conduct expert technical analysis and special studies to improve event parameters and assist State Parties in identifying the source of specific event according to the protocol to the Protocol to the Comprehensive Nuclear Test Ban Treaty. Determination of seismic event source mechanism and its depth is closely related to these tasks. It is typically done through a strategic linearized inversion of the waveforms for a complete or subset of source parameters, or similarly defined grid search through precomputed Greens Functions created for particular source models. In this presentation we demonstrate preliminary results obtained with the latter approach from an improved software design. In this development we tried to be compliant with different modes of CTBT monitoring regime and cover wide range of source-receiver distances (regional to teleseismic), resolve shallow source depths, provide full moment tensor solution based on body and surface waves recordings, be fast to satisfy both on-demand studies and automatic processing and properly incorporate observed waveforms and any uncertainties a priori as well as accurately estimate posteriori uncertainties. Posterior distributions of moment tensor parameters show narrow peaks where a significant number of reliable surface wave observations are available. For earthquake examples, fault orientation (strike, dip, and rake) posterior distributions also provide results consistent with published catalogues. Inclusion of observations on horizontal components will provide further constraints. In addition, the calculation of teleseismic P wave Green's Functions are improved through prior analysis to determine an appropriate attenuation parameter for each source-receiver path. Implemented HDF5 based Green's Functions pre-packaging allows much greater flexibility in utilizing different software packages and methods for computation. Further additions will have the rapid use of Instaseis/AXISEM full waveform synthetics added to a pre-computed GF archive. Along with traditional post processing analysis of waveform misfits through several objective functions and variance reduction, we follow a probabilistic approach to assess the robustness of moment tensor solution. In a course of this project full moment tensor and depth estimates are determined for DPRK events and shallow earthquakes using a new implementation of teleseismic P waves waveform fitting. A full grid search over the entire moment tensor space is used to appropriately sample all possible solutions. A recent method by Tape & Tape (2012) to discretize the complete moment tensor space from a geometric perspective is used. Probabilistic uncertainty estimates on the moment tensor parameters provide robustness to solution.

Finite Element Modelling of the Indo-Gangetic Basin to Study Site Amplification

NASA Astrophysics Data System (ADS)

Sivasubramonian, J.; Jaya, D.; Raghukanth, S. T. G.; Mai, P. M.

2017-12-01

We have developed a finite-element model of the 3D velocity structure of the Indo-Gangetic basin (IG basin) to quantify site amplifications due to seismic waves emanated from regional earthquakes. Estimating seismic wave amplifications is difficult in case of limited instrumentation, thus motivating us to propose a new simulation-based approach. The input required for the finite-element model include the spatial coordinates and the material properties (density, P-wave and S-wave velocities, Q factor) of the basin. Recent studies in the basin demarcate sediment layers of varying thickness, reaching down to a depth of 6 km and S-wave velocities ranging from 0.4-2.4 km/s (Srinivas et al., 2013). In the present study, our regional model has dimensions 900 x 900 x 80 km in x, y and z directions, discretized into 320 x 320 x 53 hexahedral elements. The top 6 km of the IG basin is divided into 8 different sediment layers with varying material properties. We use kinematic rupture models for the earthquake sources to simulate past as well as hypothetical future events. Two past earthquakes (Mw4.9, Delhi; Mw5.2, Chamoli) and two hypothetical earthquakes (Mw7.1; Mw8.5) are considered in our study. The rupture plane dimensions (L and W) and the slip distribution are estimated using the method of Mai and Beroza (2002). Based on focal-mechanism solutions and the depths of seismicity, we define the strike (580, 3090), the dip (650, 210), the rake (160, 770), and the depth of top edge of fault (5 km, 19 km) for the two large hypothetical earthquakes. Based on these parameters, the Centroid Moment Tensor (CMT) solution of the source is obtained. Ground motions are then simulated by solving the three-dimensional wave equation using the spectral element method (Komatitsch and Tromp, 1999). The key observations from our results are: 1) basin amplification factors for Peak Ground Velocity (PGV) are twice as high as Peak Ground Displacement (PGD) 2) PGV amplifications are as high as a factor of 6 for earthquakes occurring inside the basin, and a factor of 4 for Himalayan earthquakes (to the north of the study region) 3) The simulated shake maps of PGV and PGD show directivity. Based on the above observations, we conclude that it is important to include our model into low-frequency ground-motion estimation for seismic hazard analysis.

Investigating the Seismicity and Stress Field of the Truckee -- Lake Tahoe Region, California -- Nevada

NASA Astrophysics Data System (ADS)

Seaman, Tyler

The Lake Tahoe basin is located in a transtensional environment defined by east-dipping range--bounding normal faults, northeast--trending sinistral, and northwest-trending dextral strike-slip faults in the northern Walker Lane deformation belt. This region accommodates as much as 10 mm/yr of dextral shear between the Sierra Nevada and Basin and Range proper, or about 20% of Pacific-North American plate motion. There is abundant seismicity north of Lake Tahoe through the Truckee, California region as opposed to a lack of seismicity associated with the primary normal faults in the Tahoe basin (i.e., West Tahoe fault). This seismicity study is focused on the structural transition zone from north-striking east-dipping Sierran Range bounding normal faults into the northern Walker Lane right-lateral strike-slip domain. Relocations of earthquakes between 2000-2013 are performed by initially applying HYPOINVERSE mean sea level datum and station corrections to produce higher confidence absolute locations as input to HYPODD. HYPODD applies both phase and cross-correlation times for a final set of 'best' event relocations. Relocations of events in the upper brittle crust clearly align along well-imaged, often intersecting, high-angle structures of limited lateral extent. In addition, the local stress field is modeled from 679 manually determined short-period focal mechanism solutions, between 2000 and 2013, located within a fairly dense local seismic network. Short-period focal mechanisms were developed with the HASH algorithm and moment tensor solutions using long-period surface waves and the MTINV code. Resulting solutions show a 9:1 ratio of strike-slip to normal mechanisms in the transition zone study area. Stress inversions using the application SATSI (USGS Spatial And Temporal Stress Inversion) generally show a T-axis oriented primarily E-W that also rotates about 30 degrees counterclockwise, from a WNW-ESE trend to ENE-WSW, moving west to east across the California--Nevada border just north of Lake Tahoe. Focal mechanism and stress inversion results, based on the variance of the P-axis orientation, reveal a strike-slip dominated region directly north of Lake Tahoe that abruptly transitions northeastward to a transtentional regime along the Sierra front (i.e., in the hanging wall regime of the Sierran block). The majority of earthquakes used in the relocation and stress analysis occurs within a time period that includes unusual upper mantle/lower-crustal (˜30 km depth) dike injection events: 1) 2003 North Lake Tahoe and 2) 2011-2012 Sierra Valley, CA, that we interpret to be rift-related processes along the eastern Sierra Nevada microplate. Earthquake relocations for events shallower than about 18 km depth (the seismogenic depth determined in this study in the north Lake Tahoe area) cluster along high-angle fault structures, primarily in the footwall of the Sierra Nevada block. This new analysis isolates areas of distinctly strike-slip versus transtensional stress regimes, based on the variability of the P-axis plunge, that straddle the Sierra Nevada--Great Basin transition zone at the latitude of Lake Tahoe.

Along-strike variations of the External Betics basal detachment: Implications on the evolution of a curved FTB

NASA Astrophysics Data System (ADS)

Jiménez-Bonilla, Alejandro; Torvela, Taija; Balanyá, Juan Carlos; Expósito, Inmaculada; Díaz-Azpiroz, Manuel

2017-04-01

Analogue models have successfully tested the role of different parameters on the orogenic curvature. Among them: (1) along-strike variations of the frictional properties of the detachment layer, (2) the topography of the basement, (3) the syn-tectonic sedimentation and/or erosion and (4) the indenter shape. Previous works have pointed out that, across-strike the central Betic fold-and-thrust belt (FTB), northern branch of the Gibraltar Arc, a change on the structural style and on the topographic envelope (α) coincide with the pinch-out of Triassic evaporites and with a change in the basement dip (β) that induced changes on the wedge geometry and the basal friction (Jiménez-Bonilla et al., 2016). In this work, we tried to constrain the external orogenic wedge geometry to study the evolution of the western Betics FTB and, comparing it with the central Betics FTB, to delve into the structural variations along-strike the Betic chain. In the present work, field data together with reflection seismic interpretations permit us to constrain the across-strike variations on the structural style of the western Betics FTB. The internal FTB is deformed by SW-NE, kilometric-scale, and non-cylindrical folds detached within Triassic evaporites. The middle FTB is characterized by the profusion of allochtonous Triassic mudstones and evaporites and it is deformed into a dextral transpressive band. In the frontal FTB, a Middle Miocene package, the Olistostromic Unit, is deformed by foreland-verging thrusts overlying paleomargin-derived units. Accordingly, these differences on the structural style across the western Betics FTB could be attributable to the variations on the frictional properties of the detachment level. Regarding the wedge geometry, the topographic relief envelope (α) of the western Betics FTB is similar to that one of the central Betics. However, β is significantly lower than in the central Betics (ca. 2° vs >4°). Moreover, neither Triassic pinch-out nor basement threshold is observed in the western Betics FTB. Thus, while the deformation front stagnated during Langhian in the central Betics because of the change of the basal friction, it would have experienced slight or no stagnation in the western Betics. Finally, the along-strike differences on the basal detachment of the Betics FTB could have contributed to the quick protrusion of western Gibraltar Arc during the Upper Miocene that has been evidenced by previous works (Crespo-Blanc et al., 2016). Crespo-Blanc A., Comas, M., Balanyá J.C. (2016): Clues for a Tortonian reconstruction of the Gibraltar Arc: Structural pattern, deformation diachronism and block rotations. Tectonophysics, 2016, 683, 308-324. doi:10.1016/j.tecto.2016.05.045 Jiménez-Bonilla, A., Torvela, T., Balanyá, J.C., Expósito, I., Díaz-Azpiroz, M. (2016): Changes in dip and frictional properties of the basal detachment controlling orogenic wedge propagation and frontal collapse: the External central Betics case. Tectonics, in press. DOI: 10.1002/2016TC004196 Acknowledgements: RNM-415 and CGL-2013-46368-P

Fault geometry and cumulative offsets in the central Coast Ranges, California: Evidence for northward increasing slip along the San Gregorio-San Simeon-Hosgri fault

USGS Publications Warehouse

Langenheim, V.E.; Jachens, R.C.; Graymer, R.W.; Colgan, J.P.; Wentworth, C.M.; Stanley, R.G.

2012-01-01

Estimates of the dip, depth extent, and amount of cumulative displacement along the major faults in the central California Coast Ranges are controversial. We use detailed aeromagnetic data to estimate these parameters for the San Gregorio–San Simeon–Hosgri and other faults. The recently acquired aeromagnetic data provide an areally consistent data set that crosses the onshore-offshore transition without disruption, which is particularly important for the mostly offshore San Gregorio–San Simeon–Hosgri fault. Our modeling, constrained by exposed geology and in some cases, drill-hole and seismic-reflection data, indicates that the San Gregorio–San Simeon–Hosgri and Reliz-Rinconada faults dip steeply throughout the seismogenic crust. Deviations from steep dips may result from local fault interactions, transfer of slip between faults, or overprinting by transpression since the late Miocene. Given that such faults are consistent with predominantly strike-slip displacement, we correlate geophysical anomalies offset by these faults to estimate cumulative displacements. We find a northward increase in right-lateral displacement along the San Gregorio–San Simeon–Hosgri fault that is mimicked by Quaternary slip rates. Although overall slip rates have decreased over the lifetime of the fault, the pattern of slip has not changed. Northward increase in right-lateral displacement is balanced in part by slip added by faults, such as the Reliz-Rinconada, Oceanic–West Huasna, and (speculatively) Santa Ynez River faults to the east.

Pseudotachylyte: Reading the Record of Paleoseismicity in Low-Angle Normal Faults

NASA Astrophysics Data System (ADS)

Smith, D. M.; Goodwin, L. B.; Feinberg, J. M.; Ellis, A. P.

2012-12-01

Whether or not low-angle normal faults (LANFs, dipping <30°) can produce earthquakes is hotly debated. Pseudotachylyte - rapidly quenched frictional melt generated during seismic failure - has been noted in several LANF sites but not extensively studied. We recently documented significant pseudotachylyte exposures in both the South Mountains and Catalina-Rincon metamorphic core complexes of Arizona. In both field areas, pseudotachylyte is located below detachment faults, where it is best exposed in fractured areas beneath chlorite breccia zones. Generation veins dip 7-24°, are locally parallel to host rock foliations, and range from 1 mm to 3 cm thick. Where subvertical exposures are available, generation and injection veins either form networks up to 1 m thick or are stacked, such that multiple veins spaced < 1m apart are exposed in zones 2 to 3 m thick. Outcrops do not permit mapping of pseudotachylytes' full lateral extent, but do allow a minimum length of 50 m oblique to strike to be estimated. The magnitude of pseudotachylyte exposure in these core complexes implies significant seismicity. A key question is whether the generation surfaces were in their present orientations when they failed seismically. To answer this, we are applying a fault paleogeometry test. The cornerstone of this test is a comparison of two paleomagnetic vectors. The first will be determined through standard paleomagnetic analyses of oriented pseudotachylyte samples. The second will represent the vector expected if no LANF rotation has occurred and will be determined through correlation of a sample's 40Ar/39Ar age with its coeval magnetic pole location. Any discrepancy between the vectors will be interpreted to represent rotation of the fault since seismicity. Anderson-Byerlee compatible slip will be supported by discrepancies requiring a seismically active dip >30°. An active dip of <30° suggests that additional factors have reduced effective stress and/or frictional resistance to allow seismicity. A third, similarly extensive zone of pseudotachylyte veins in Central Otago, New Zealand will be included with our Arizona sites in this analysis. Previous work in this location shows more than 100 veins dipping 10-30°, from 1- 3 cm thick, extending up to 200 m along strike (Barker, 2005). The Otago site emphasizes seismicity as a component of LANF development in different tectonic regions, and will allow comparison of LANF pseudotachylytes of disparate host rock and ages (Miocene in U.S. sites, Cretaceous in NZ). Preliminary data demonstrate a range in magnetic characteristics of the samples we have collected. Veins within felsic granodiorite and alaskite in the South Mountains show susceptibilities ranging from 0.48 -1.06 x 10-3 SI. These values are indistinguishable from host rock susceptibilities (0.48 - 1.32 x 10-3 SI). In contrast, Rincon pseudotachylyte has magnetic susceptibilities ranging from 29.3 to >80.0 x 10-3 SI and porphyroclastic gneiss host rock values are a considerably lower 7.44 - 8.64 x 10-3 SI. We therefore anticipate this test will only be successfully applied toward some of our samples. Our presentation will include both descriptions of pseudotachlylyte zones and networks and preliminary paleomagnetic data.

Seismic source study of the Racha-Dzhava (Georgia) earthquake from aftershocks and broad-band teleseismic body-wave records: An example of active nappe tectonics

USGS Publications Warehouse

Fuenzalida, H.; Rivera, L.; Haessler, H.; Legrand, D.; Philip, H.; Dorbath, L.; McCormack, D.; Arefiev, S.; Langer, C.; Cisternas, A.

1997-01-01

The Racha-Dzhava earthquake (Ms = 7.0) that occurred on 1991 April 29 at 09:12:48.1 GMT in the southern border of the Great Caucasus is the biggest event ever recorded in the region, stronger than the Spitak earthquake (Ms = 6.9) of 1988. A field expedition to the epicentral area was organised and a temporary seismic network of 37 stations was deployed to record the aftershock activity. A very precise image of the aftershock distribution is obtained, showing an elongated cloud oriented N105??, with one branch trending N310?? in the western part. The southernmost part extends over 80 km, with the depth ranging from 0 to 15 km, and dips north. The northern branch, which is about 30 km long, shows activity that ranges in depth from 5 to 15 km. The complex thrust dips northwards. A stress-tensor inversion from P-wave first-motion polarities shows a state of triaxial compression, with the major principal axis oriented roughly N-S, the minor principal axis being vertical. Body-waveform inversion of teleseismic seismograms was performed for the main shock, which can be divided into four subevents with a total rupture-time duration of 22 s. The most important part of the seismic moment was released by a gentle northerly dipping thrust. The model is consistent with the compressive tectonics of the region and is in agreement with the aftershock distribution and the stress tensor deduced from the aftershocks. The focal mechanisms of the three largest aftershocks were also inverted from body-wave records. The April 29th (Ms = 6.1) and May 5th (Ms = 5.4) aftershocks have thrust mechanisms on roughly E-W-oriented planes, similar to the main shock. Surprisingly, the June 15th (Ms = 6.2) aftershock shows a thrust fault striking N-S. This mechanism is explained by the structural control of the rupture along the east-dipping geometry of the Dzirula Massif close to the Borzhomi-Kazbeg strike-slip fault. In fact, the orientation and shape of the stress tensor produce a thrust on a N-S oriented plane. Nappe tectonics has been identified as an important feature in the Caucasus, and the source mechanism is consistent with this observation. A hidden fault is present below the nappe, and no large surface breaks were observed due to the main shock. The epicentral region is characterized by sediments that are trapped between two crystalline basements: the Dzirula Massif, which crops out south of Chiatoura, and the Caucasus Main Range north of Oni. Most, if not all, of the rupture is controlled by the thrusting of overlapping, deformed and folded sediments over the Dzirula Massif. This event is another example of blind active faults, with the distinctive feature that the fault plane dips at a gentle angle. The Racha Range is one of the surface expressions of this blind thrust, and its growth is the consequence and evidence of similar earthquakes in the past.

A Moho ramp imaged beneath the High Himalaya in Garhwal, India

NASA Astrophysics Data System (ADS)

Caldwell, W. B.; Klemperer, S. L.; Lawrence, J.; Rai, S. S.; Ashish, A.

2011-12-01

In this study we image the Moho beneath the Himalaya of Garhwal, India (at approximately 79°E) using common conversion point (CCP) stacking of receiver functions (RFs). We calculate RFs using iterative time-domain deconvolution on a catalog of 450 events recorded on a linear array of 21 broadband seismometers operated for 21 months in 2005-2006 by India's National Geophysical Research Institute (NGRI). Our images show a horizontal Moho beneath the Lesser Himalaya and an abrupt increase of ≥ 5 km in Moho depth beneath the High Himalaya, implying a local dip of 20±5°. A steeply-dipping Moho beneath the High Himalaya has been proposed by some workers on the basis of gravity modeling, and is observed in some seismic images elsewhere in the range, but is not a widely-recognized feature of the Himalaya. Geophysical profiles across the Himalaya are not numerous enough to say whether the steep Moho is a local feature only, or is widespread but has not yet been consistently observed. A steeply-dipping Moho implies a flexure in the downgoing India plate, which we propose may play a role in the formation of the topographic front of the Himalaya. Recent studies have proposed that a ramp in the Main Himalayan Thrust-the basal décollement into which the Himalayan thrust faults root-may focus rock uplift, leading to an abrupt steepening of topography and the observed physiographic transition between the Lesser and Higher Himalaya. The mechanism of rock uplift may be out-of-sequence thrusting on the MCT-I, or stacking of imbricate thrust sheets which form as a result of underplating at the ramp. A flexure of the India plate, implied by the steep Moho dip that we observe, is a likely mechanism for controlling the formation and location of this décollement ramp, and thereby the initiation of high topography. Geophysical profiles across the Himalaya are not yet numerous enough to constrain along-strike variations in this steeply-dipping Moho, so its relationship to the formation of the topographic front of the Himalaya throughout the rest of the range remains a topic for further study.

3-D simulations of M9 earthquakes on the Cascadia Megathrust: Key parameters and uncertainty

USGS Publications Warehouse

Wirth, Erin; Frankel, Arthur; Vidale, John; Marafi, Nasser A.; Stephenson, William J.

2017-01-01

Geologic and historical records indicate that the Cascadia subduction zone is capable of generating large, megathrust earthquakes up to magnitude 9. The last great Cascadia earthquake occurred in 1700, and thus there is no direct measure on the intensity of ground shaking or specific rupture parameters from seismic recordings. We use 3-D numerical simulations to generate broadband (0-10 Hz) synthetic seismograms for 50 M9 rupture scenarios on the Cascadia megathrust. Slip consists of multiple high-stress drop subevents (~M8) with short rise times on the deeper portion of the fault, superimposed on a background slip distribution with longer rise times. We find a >4x variation in the intensity of ground shaking depending upon several key parameters, including the down-dip limit of rupture, the slip distribution and location of strong-motion-generating subevents, and the hypocenter location. We find that extending the down-dip limit of rupture to the top of the non-volcanic tremor zone results in a ~2-3x increase in peak ground acceleration for the inland city of Seattle, Washington, compared to a completely offshore rupture. However, our simulations show that allowing the rupture to extend to the up-dip limit of tremor (i.e., the deepest rupture extent in the National Seismic Hazard Maps), even when tapering the slip to zero at the down-dip edge, results in multiple areas of coseismic coastal uplift. This is inconsistent with coastal geologic evidence (e.g., buried soils, submerged forests), which suggests predominantly coastal subsidence for the 1700 earthquake and previous events. Defining the down-dip limit of rupture as the 1 cm/yr locking contour (i.e., mostly offshore) results in primarily coseismic subsidence at coastal sites. We also find that the presence of deep subevents can produce along-strike variations in subsidence and ground shaking along the coast. Our results demonstrate the wide range of possible ground motions from an M9 megathrust earthquake in Cascadia, and the potential to further constrain key rupture parameters using geologic and geophysical observations, ultimately improving our estimation of seismic hazard associated with the Cascadia megathrust.

Streaks of Aftershocks Following the 2004 Sumatra-Andaman Earthquake

NASA Astrophysics Data System (ADS)

Waldhauser, F.; Schaff, D. P.; Engdahl, E. R.; Diehl, T.

2009-12-01

Five years after the devastating 26 December, 2004 M 9.3 Sumatra-Andaman earthquake, regional and global seismic networks have recorded tens of thousands of aftershocks. We use bulletin data from the International Seismological Centre (ISC) and the National Earthquake Information Center (NEIC), and waveforms from IRIS, to relocate more than 20,000 hypocenters between 1964 and 2008 using teleseimic cross-correlation and double-difference methods. Relative location uncertainties of a few km or less allow for detailed analysis of the seismogenic faults activated as a result of the massive stress changes associated with the mega-thrust event. We focus our interest on an area of intense aftershock activity off-shore Banda Aceh in northern Sumatra, where the relocated epicenters reveal a pattern of northeast oriented streaks. The two most prominent streaks are ~70 km long with widths of only a few km. Some sections of the streaks are formed by what appear to be small, NNE striking sub-streaks. Hypocenter depths indicate that the events locate both on the plate interface and in the overriding Sunda plate, within a ~20 km wide band overlying the plate interface. Events on the plate interface indicate that the slab dip changes from ~20° to ~30° at around 50 km depth. Locations of the larger events in the overriding plate indicate an extension of the steeper dipping mega thrust fault to the surface, imaging what appears to be a major splay fault that reaches the surface somewhere near the western edge of the Aceh basin. Additional secondary splay faults, which branch off the plate interface at shallower depths, may explain the diffuse distribution of smaller events in the overriding plate, although their relative locations are less well constrained. Focal mechanisms support the relocation results. They show a narrowing range of fault dips with increasing distance from the trench. Specifically, they show reverse faulting on ~30° dipping faults above the shallow (20°) dipping plate interface. The observation of active splay faults associated with the mega thrust event is consistent with co- and post-seismic motion data, and may have significant implications on the generation and size of the tsunami that caused 300,000 deaths.

A Non-linear Geodetic Data Inversion Using ABIC for Slip Distribution on a Fault With an Unknown dip Angle

NASA Astrophysics Data System (ADS)

Fukahata, Y.; Wright, T. J.

2006-12-01

We developed a method of geodetic data inversion for slip distribution on a fault with an unknown dip angle. When fault geometry is unknown, the problem of geodetic data inversion is non-linear. A common strategy for obtaining slip distribution is to first determine the fault geometry by minimizing the square misfit under the assumption of a uniform slip on a rectangular fault, and then apply the usual linear inversion technique to estimate a slip distribution on the determined fault. It is not guaranteed, however, that the fault determined under the assumption of a uniform slip gives the best fault geometry for a spatially variable slip distribution. In addition, in obtaining a uniform slip fault model, we have to simultaneously determine the values of the nine mutually dependent parameters, which is a highly non-linear, complicated process. Although the inverse problem is non-linear for cases with unknown fault geometries, the non-linearity of the problems is actually weak, when we can assume the fault surface to be flat. In particular, when a clear fault trace is observed on the EarthOs surface after an earthquake, we can precisely estimate the strike and the location of the fault. In this case only the dip angle has large ambiguity. In geodetic data inversion we usually need to introduce smoothness constraints in order to compromise reciprocal requirements for model resolution and estimation errors in a natural way. Strictly speaking, the inverse problem with smoothness constraints is also non-linear, even if the fault geometry is known. The non-linearity has been dissolved by introducing AkaikeOs Bayesian Information Criterion (ABIC), with which the optimal value of the relative weight of observed data to smoothness constraints is objectively determined. In this study, using ABIC in determining the optimal dip angle, we dissolved the non-linearity of the inverse problem. We applied the method to the InSAR data of the 1995 Dinar, Turkey earthquake and obtained a much shallower dip angle than before.

What Controls Subduction Earthquake Size and Occurrence?

NASA Astrophysics Data System (ADS)

Ruff, L. J.

2008-12-01

There is a long history of observational studies on the size and recurrence intervals of the large underthrusting earthquakes in subduction zones. In parallel with this documentation of the variability in both recurrence times and earthquake sizes -- both within and amongst subduction zones -- there have been numerous suggestions for what controls size and occurrence. In addition to the intrinsic scientific interest in these issues, there are direct applications to hazards mitigation. In this overview presentation, I review past progress, consider current paradigms, and look toward future studies that offer some resolution of long- standing questions. Given the definition of seismic moment, earthquake size is the product of overall static stress drop, down-dip fault width, and along-strike fault length. The long-standing consensus viewpoint is that for the largest earthquakes in a subduction zone: stress-drop is constant, fault width is the down-dip extent of the seismogenic portion of the plate boundary, but that along-strike fault length can vary from one large earthquake to the next. While there may be semi-permanent segments along a subduction zone, successive large earthquakes can rupture different combinations of segments. Many investigations emphasize the role of asperities within the segments, rather than segment edges. Thus, the question of earthquake size is translated into: "What controls the along-strike segmentation, and what determines which segments will rupture in a particular earthquake cycle?" There is no consensus response to these questions. Over the years, the suggestions for segmentation control include physical features in the subducted plate, physical features in the over-lying plate, and more obscure -- and possibly ever-changing -- properties of the plate interface such as the hydrologic conditions. It seems that the full global answer requires either some unforeseen breakthrough, or the long-term hard work of falsifying all candidate hypotheses except one. This falsification process requires both concentrated multidisciplinary efforts and patience. Large earthquake recurrence intervals in the same subduction zone segment display a significant, and therefore unfortunate, variability. Over the years, many of us have devised simple models to explain this variability. Of course, there are also more complicated explanations with many additional model parameters. While there has been important observational progress as both historical and paleo-seismological studies continue to add more data pairs of fault length and recurrence intervals, there has been a frustrating lack of progress in elimination of candidate models or processes that explain recurrence time variability. Some of the simple models for recurrence times offer a probabilistic or even deterministic prediction of future recurrence times - and have been used for hazards evaluation. It is important to know if these models are correct. Since we do not have the patience to wait for a strict statistical test, we must find other ways to test these ideas. For example, some of the simple deterministic models for along-strike segment interaction make predictions for variation in tectonic stress state that can be tested during the inter-seismic period. We have seen how some observational discoveries in the past decade (e.g., the episodic creep events down-dip of the seismogenic zone) give us additional insight into the physical processes in subduction zones; perhaps multi-disciplinary studies of subduction zones will discover a new way to reliably infer large-scale shear stresses on the plate interface?

Geohydrology and water quality of the Durham Center Area, Durham, Connecticut

USGS Publications Warehouse

Melvin, R.L.; Stone, J.R.; Craft, P.A.; Lane, J.W.; Davies, B. S.

1995-01-01

Contaminated ground water is widespread and persistent beneath the Durham Center area in the town of Durham, Conn. Most of the contaminants are organic halides, usually trichloroethene, 1,1,1-trichloroethane, and tetrachloroethene. Less extensive chemical contamination of surface water, soil, and glacial sediments also has been detected. Two manufacturing companies, located at the northern and southern ends of this largely residential area, are believed to be the principal sources of the organic compounds detected in ground water. The contamination of water in the bedrock, the primary source of drinking water throughout the area, is the major environmental concern. Maximum concentrations of trichloroethene in three bed- rock wells range from 4,500 to about 5,500 mg/L (micrograms per liter). Concentrations of trichloroethene greater than 5 mg/L, the maximum contaminant level established for drinking water by the U.S Environmental Protection Agency, have regularly been detected in water samples from many other bedrock wells for at least 9 years. The geohydrology of the area is highly complex. Compact lodgment till that is up to 30 feet thick and probably fractured, overlies the bedrock. The bedrock is lithologically heterogeneous, and con- sists mostly of red fluvial sandstone, siltstone, and conglomerate; it is locally interbedded with black lacustrine shales and gray sandstones. Lithology and stratigraphy interpreted from borehole-geophysical logs at Durham Center are consistent with the Portland Formation subfacies described in earlier geologic studies. Beds strike nearly north-south and dip gently eastward. At least one high-angle normal fault transects the bedrock; it strikes northeast and dips northwest. Acoustic televiewer logs, measurements at out-crops, and azimuthal, square-array, resistivity data indicate a dominance of northeast-striking fractures that dip steeply northwest and southeast. Less prevalent strike directions are north to east-north-east. The till and sedimentary bedrock are dual-porosity, dual-permeability media. The hydraulic conductivity of the bulk mass of till is believed to be on the order of tenths of a foot per day to about 2.5 feet per day, with a total porosity of about 25 percent and an estimated average fracture porosity of less than 1 percent. The reported transmissivities of the bedrock range from less than 1 to about 17,000 feet squared per day and storativity is generally about 10-4, but the accuracy of these values is uncertain. The intergranular porosity of the sandstone units is estimated to average 5 percent, and estimates of fracture porosity from square-array, resistivity soundings at two sites were 1.1 and 2.7 percent. The bedrock has characteristics of both a single aquifer and a multi-unit, artesian or leaky aquifer system. A local ground-water-flow system that includes the upper part of the bedrock is unconfined. A large- scale flow system in deeper parts of the bedrock has transported organic compounds across topographic drainage divides. Borehole-geophysical logs and head measurements indicate that the natural ground- water-flow system in the bedrock has been altered by drilled wells that connect fractures and by with- drawals from wells. A conceptual model of the movement and fate of organic contaminants suggests that (1) nonaqueous phase organic halides are retained near their source; (2) flow is primarily through fractures in the till and through fractures and bedding-plane openings in the sedimentary rocks; (3) retardation of contaminants occurs primarily by diffusion from fractures into the aquifer matrix; and (4) transport directions of dissolved organic halides are controlled by a combination of natural hydraulic gradients, hydraulic gradients produced by the cyclical pumping of wells, and by the strike directions of bedrock faults, fractures, and bedding planes.

SIR-A imagery in geologic studies of the Sierra Madre Oriental, northeastern Mexico. Part 1 (Regional stratigraphy): The use of morphostratigraphic units in remote sensing mapping

NASA Technical Reports Server (NTRS)

Longoria, J. F.; Jimenez, O. H.

1985-01-01

SIR-A imaging was used in geological studies of sedimentary terrains in the Sierra Madre Oriental, northeastern Mexico. Geological features such as regional strike and dip, bedding, folding and faulting were readily detected on the image. The recognition of morphostructural units in the imagery, coupled with field verification, enabled geological mapping of the region at the scale of 1:250 000. Structural profiling lead to the elaboration of a morphostructural map allowing the recognition of an echelon folds and field trends which were used to postulate the ectonic setting of the region.

Source mechanism of very-long-period signals accompanying dome growth activity at Merapi volcano, Indonesia

USGS Publications Warehouse

Hidayat, D.; Chouet, B.; Voight, B.; Dawson, P.; Ratdomopurbo, Antonius

2002-01-01

Very-long-period (VLP) pulses with period of 6-7s, displaying similar waveforms, were identified in 1998 from broadband seismographs around the summit crater. These pulses accompanied most of multiphase (MP) earthquakes, a type of long-period event locally defined at Merapi Volcano. Source mechanisms for several VLP pulses were examined by applying moment tensor inversion to the waveform data. Solutions were consistent with a crack striking ???70?? and dipping ???50?? SW, 100m under the active dome, suggest pressurized gas transport involving accumulation and sudden release of 10-60 m3 of gas in the crack over a 6s interval.

Geologic map of the Santa Ana Pueblo quadrangle, Sandoval County, New Mexico

USGS Publications Warehouse

Personius, Stephen F.

2002-01-01

The Santa Ana Pueblo quadrangle is located in the northern part of the Albuquerque basin, which is the largest basin or graben within the Rio Grande rift. The quadrangle is underlain by poorly consolidated sedimentary rocks of the Santa Fe Group and is dominated by Santa Ana Mesa, a volcanic tableland underlain by basalt flows of the San Felipe volcanic field. The San Felipe volcanic field is the largest area of basaltic lavas exposed in the Albuquerque basin. The structural fabric of the quadrangle is dominated by dozens of generally north striking, east- and west-dipping normal faults associated with the Neogene Rio Grande rift.

The characteristics of the western extension of the Karakax fault in NW Tibet and its tectonic implications

NASA Astrophysics Data System (ADS)

Ge, C.; Liu, D.; Li, H.; Zheng, Y.; Pan, J.

2017-12-01

The Karakax strike-slip fault, located in northwest Tibet, is a mature deformation belt with a long-time evolutionary history, which is also active at present and plays an important role in the tectonic deformation of the northwestern Tibetan Plateau. Nowadays, most geologists consider that the Karakax fault is generally east-west striking along the Karakax river valley, and northwest striking until to the Tashkorgan in the Mazar area. However, an ENE-WSW fault was identified at the Mazar area, which sited at the bend of the Karakax fault, we named this fault as the Matar fault. Via the detailed geological survey, the similar geometry and kinematic characteristics were identified between the Karakax and Matar faults: (1) The similar fault zone scale(Karakax:90 300m; Matar:100 220m); (2) The similar preferred orientation (nearly EW) of the stretching lineations and foliations; (3) All the fault planes of the both faults have a high dip angle and is nearly EW striking; (4) Lots of ductile deformations, such as σ-type quartz rotational mortar, S-C fabric, symmetric drag fold and so on, indicated that the Matar fault is a right-lateral strike-slip and thrust fault during the early ductile deformation stage; (5) the deluvium, sheared by Matar fault, indicated that the Matar fault has already transformed into a left-lateral strike-slip fault during the later brittle deformation stage. All the above showed that the Matar fault has a similar geometry and kinematic characteristics with the Karakax fault, and the former is the probable the western extension of the latter. Moreover, the form of the Karakax-Matar fault may had an impact to the geomorphology of the west Kunlun-Pamir area, such as the strike of the moutains and faults. considering the age of west Kunlun mountains uplifting and Karakax fault activating, we regard that the Matar fault (the westward extension of Karakax fault) may contributes much in forming the modern geomorphology features of the west Kunlun-Pamir area.

Damage and Shaking Intensity in the M5.7 Canyondam Earthquake

NASA Astrophysics Data System (ADS)

Boatwright, J.; Chapman, K.; Gold, M. B.; Hardebeck, J. L.

2013-12-01

An M5.7 earthquake occurred southeast of Lake Almanor, CA, at 8:47 PM on May 23, 2013. Double-difference relocations of the main shock and aftershocks indicate that the earthquake nucleated at 11 km depth and ruptured up dip on a fault striking 292° and dipping 70° to the northeast. The earthquake cracked foundations, broke chimneys, and ruptured plumbing around Lake Almanor. We canvassed communities around the lake and to the south and east for earthquake damage, adding reports from our interviews to the geocoded 'Did You Feel It?' reports and to a set of damage reports collected by the Plumas County Office of Emergency Services. Three communities suffered significant damage. In Lake Almanor West, 14 km and 290° from the hypocenter, one wood-frame house was shifted on its foundation, the cripple wall of another house was racked, and water and gas pipes in five houses were ruptured. This damage indicates the shaking approached MMI 8. In Lake Almanor Country Club, 10 km and 310° from the hypocenter, more than 40 chimneys were cracked, broken, or collapsed, a coupling for the municipal water tank was ruptured, and a 200-foot long fissure opened on a slope facing the lake. This damage indicates shaking between MMI 7 and MMI 8, consistent with the accelerograph recording of PGA = 38% g and PGV = 30 cm/s at the Fire Station in Lake Almanor Country Club. This CSMIP station and a PG&E station on the crest of the Butt Valley Dam obtained the only recordings within 50 km of the epicenter. In Hamilton Branch, 10 km and 345° from the hypocenter, a foundation of a wood-frame house was damaged, and 14 chimneys and a water pipe were broken, indicative of MMI 7 shaking. All three communities are underlain by Tertiary and Quaternary basalts. The communities of Chester, Westwood, and Greenville were less damaged, suffering cracked drywall, broken windows, and objects thrown from shelves. The intensities in the three most strongly damaged communities increase as the azimuth from the source approaches the fault strike. This damage pattern could be caused by rupture directivity if the earthquake or the strongest sub-event of the earthquake ruptured up dip and to the west.

Tectonic Structure of the Middle America Pacific Margin and Incoming Cocos Plate From Costa Rica to Guatemala

NASA Astrophysics Data System (ADS)

Ranero, C. R.; Weinrebe, W.; Grevemeyer, I.; Phipps Morgan, J.; Vannucchi, P.; von Huene, R.

2003-12-01

A new multibeam bathymetry and magnetic survey with R/V SONNE in summer 2003 has mapped the continental margin and incoming plate of NW Nicaragua, El Salvador and Guatemala, extending existing coverage from offshore Costa Rica and part of Nicaragua to a full coverage map of about 1200 km long by 100 km wide area along the plate boundary. The incoming plate along Nicaragua, El Salvador and Guatemala is of similar age and was formed at superfast spreading rates; however, its morphology changes drastically along strike. The seafloor-spreading inherited morphology is very smooth along Nicaragua, but with ridges up to 800 m high in Guatemala, with a transition across El Salvador. The development and dimensions of the dominant inherited fabric seems to be related to discontinuities at the paleospreading center. A series of troughs oblique to the main fabric may indicate the location of pseudofaults and correspond to areas where the seafloor fabric is most prominent. Bending of the oceanic plate into the trench reactivates the inherited fabric forming a well pervasive faulting system along the oceanic trench slope. The continental slope displays three morphotectonic units that roughly correspond to the upper, middle and lower slope, although the across slope width of each unit is fairly variable. Small canyons and gullies that form at the sudden dip change across the shelf break carve the upper slope. The canyons coalesce and become shallower as the dip decreases downslope. Locally some large canyons continue into the slope toe. The middle slope is a rough terrain variable in width and dip sculptured by pervasive normal faulting and locally by mass wasting processes. The lower slope is formed by en echelon terraces striking similar to the rough terrain of the incoming plate and mimicking the half graben morphology of the underthusting plate. The three morphotectonic slope domains represent differences in tectonic activity, with more stable upper slope, a middle slope dominated by tectonic extension and the thin, highly fractured upper plate of the lower slope riffling over the incoming plate topography. The trench axis is largely empty, with local turbidite ponds at the mouth of a few large canyons transecting the entire slope.

Calculation of sidewall boundary-layer parameters from rake measurements for the Langley 0.3-meter transonic cryogenic tunnel

NASA Technical Reports Server (NTRS)

Murthy, A. V.

1987-01-01

Correction of airfoil data for sidewall boundary-layer effects requires a knowledge of the boundary-layer displacement thickness and the shape factor with the tunnel empty. To facilitate calculation of these quantities under various test conditions for the Langley 0.3 m Transonic Cryogenic Tunnel, a computer program was written. This program reads the various tunnel parameters and the boundary-layer rake total head pressure measurements directly from the Engineering Unit tapes to calculate the required sidewall boundary-layer parameters. Details of the method along with the results for a sample case are presented.

Experimental and predicted pressure and heating distributions for an Aeroassist Flight Experiment vehicle in air at Mach 10

NASA Technical Reports Server (NTRS)

Micol, John R.

1989-01-01

The Aeroassisted Flight Experiment vehicle for whose scale model pressure and heat-transfer rate distributions have been measured in air at Mach 10 is a 60-deg elliptic cone, raked off at a 73-percent angle, with an ellipsoid nose and a skirt added to the base of the rake plane to reduce heating. The predictions of both an inviscid flow-field code and a Navier-Stokes solver are compared with measured values. Good agreement is obtained in the case of pressure distributions; the effect of Reynolds number on heat-transfer distributions is noted to be small.

Duct Mode Measurements on the TFE731-60 Full Scale Engine

NASA Technical Reports Server (NTRS)

Sutliff, Daniel L.; Konno, Kevin E.; Heidelberg, Laurence J.

2002-01-01

A continuously rotating rake with radial microphones was developed to measure the inlet and exhaust duct modes on a TFE731-60 turbofan engine. This was the first time the rotating rake technology was used on a production engine. The modal signature for the first three fan harmonics was obtained in the inlet and exhaust. Rotor-stator and rotor-strut interaction modes were measured. Total harmonic power was calculated over a range of fan speeds. Above sonic tip speed, the rotor locked mode was not strong enough to be identified, but the 'buzz-saw' noise at fan sub-harmonics was identified.

Flowfield measurements in the NASA Lewis Research Center 9- by 15-foot low-speed wind tunnel

NASA Technical Reports Server (NTRS)

Hughes, Christopher E.

1989-01-01

An experimental investigation was conducted in the NASA Lewis 9- by 15-Foot Low-Speed Wind Tunnel to determine the flow characteristics in the test section during wind tunnel operation. In the investigation, a 20-probe horizontally-mounted Pitot-static flow survey rake was used to obtain cross-sectional total and static pressure surveys at four axial locations in the test section. At each axial location, the cross-sectional flowfield surveys were made by repositioning the Pitot-static flow survey rake vertically. In addition, a calibration of the new wind tunnel rake instrumentation, used to determine the wind tunnel operating conditions, was performed. Boundary laser surveys were made at three axial locations in the test section. The investigation was conducted at tunnel Mach numbers 0.20, 0.15, 0.10, and 0.05. The test section profile results from the investigation indicate that fairly uniform total pressure profiles (outside the test section boundary layer) and fairly uniform static pressure and Mach number profiles (away from the test section walls and downstream of the test section entrance) exist throughout in the wind tunnel test section.

Structural analysis of S-wave seismics around an urban sinkhole: evidence of enhanced dissolution in a strike-slip fault zone

NASA Astrophysics Data System (ADS)

Wadas, Sonja H.; Tanner, David C.; Polom, Ulrich; Krawczyk, Charlotte M.

2017-12-01

In November 2010, a large sinkhole opened up in the urban area of Schmalkalden, Germany. To determine the key factors which benefited the development of this collapse structure and therefore the dissolution, we carried out several shear-wave reflection-seismic profiles around the sinkhole. In the seismic sections we see evidence of the Mesozoic tectonic movement in the form of a NW-SE striking, dextral strike-slip fault, known as the Heßleser Fault, which faulted and fractured the subsurface below the town. The strike-slip faulting created a zone of small blocks ( < 100 m in size), around which steep-dipping normal faults, reverse faults and a dense fracture network serve as fluid pathways for the artesian-confined groundwater. The faults also acted as barriers for horizontal groundwater flow perpendicular to the fault planes. Instead groundwater flows along the faults which serve as conduits and forms cavities in the Permian deposits below ca. 60 m depth. Mass movements and the resulting cavities lead to the formation of sinkholes and dissolution-induced depressions. Since the processes are still ongoing, the occurrence of a new sinkhole cannot be ruled out. This case study demonstrates how S-wave seismics can characterize a sinkhole and, together with geological information, can be used to study the processes that result in sinkhole formation, such as a near-surface fault zone located in soluble rocks. The more complex the fault geometry and interaction between faults, the more prone an area is to sinkhole occurrence.

Spatial and Temporal Variations in Slip Partitioning During Oblique Convergence Experiments

NASA Astrophysics Data System (ADS)

Beyer, J. L.; Cooke, M. L.; Toeneboehn, K.

2017-12-01

Physical experiments of oblique convergence in wet kaolin demonstrate the development of slip partitioning, where two faults accommodate strain via different slip vectors. In these experiments, the second fault forms after the development of the first fault. As one strain component is relieved by one fault, the local stress field then favors the development of a second fault with different slip sense. A suite of physical experiments reveals three styles of slip partitioning development controlled by the convergence angle and presence of a pre-existing fault. In experiments with low convergence angles, strike-slip faults grow prior to reverse faults (Type 1) regardless of whether the fault is precut or not. In experiments with moderate convergence angles, slip partitioning is dominantly controlled by the presence of a pre-existing fault. In all experiments, the primarily reverse fault forms first. Slip partitioning then develops with the initiation of strike-slip along the precut fault (Type 2) or growth of a secondary reverse fault where the first fault is steepest. Subsequently, the slip on the first fault transitions to primarily strike-slip (Type 3). Slip rates and rakes along the slip partitioned faults for both precut and uncut experiments vary temporally, suggesting that faults in these slip-partitioned systems are constantly adapting to the conditions produced by slip along nearby faults in the system. While physical experiments show the evolution of slip partitioning, numerical simulations of the experiments provide information about both the stress and strain fields, which can be used to compute the full work budget, providing insight into the mechanisms that drive slip partitioning. Preliminary simulations of precut experiments show that strain energy density (internal work) can be used to predict fault growth, highlighting where fault growth can reduce off-fault deformation in the physical experiments. In numerical simulations of uncut experiments with a first non-planar oblique slip fault, strain energy density is greatest where the first fault is steepest, as less convergence is accommodated along this portion of the fault. The addition of a second slip-partitioning fault to the system decreases external work indicating that these faults increase the mechanical efficiency of the system.

Triangulation Based 3D Laser Imaging for Fracture Orientation Analysis

NASA Astrophysics Data System (ADS)

Mah, J.; Claire, S.; Steve, M.

2009-05-01

Laser imaging has recently been identified as a potential tool for rock mass characterization. This contribution focuses on the application of triangulation based, short-range laser imaging to determine fracture orientation and surface texture. This technology measures the distance to the target by triangulating the projected and reflected laser beams, and also records the reflection intensity. In this study, we acquired 3D laser images of rock faces using the Laser Camera System (LCS), a portable instrument developed by Neptec Design Group (Ottawa, Canada). The LCS uses an infrared laser beam and is immune to the lighting conditions. The maximum image resolution is 1024 x 1024 volumetric image elements. Depth resolution is 0.5 mm at 5 m. An above ground field trial was conducted at a blocky road cut with well defined joint sets (Kingston, Ontario). An underground field trial was conducted at the Inco 175 Ore body (Sudbury, Ontario) where images were acquired in the dark and the joint set features were more subtle. At each site, from a distance of 3 m away from the rock face, a grid of six images (approximately 1.6 m by 1.6 m) was acquired at maximum resolution with 20% overlap between adjacent images. This corresponds to a density of 40 image elements per square centimeter. Polyworks, a high density 3D visualization software tool, was used to align and merge the images into a single digital triangular mesh. The conventional method of determining fracture orientations is by manual measurement using a compass. In order to be accepted as a substitute for this method, the LCS should be capable of performing at least to the capabilities of manual measurements. To compare fracture orientation estimates derived from the 3D laser images to manual measurements, 160 inclinometer readings were taken at the above ground site. Three prominent joint sets (strike/dip: 236/09, 321/89, 325/01) were identified by plotting the joint poles on a stereonet. Underground, two main joint sets (strike/dip: 060/00, 114/86) were identified from 49 manual inclinometer measurements A stereonet of joint poles from the 3D laser data was generated using the commercial software Split-FX. Joint sets were identified successfully and their orientations correlated well with the hand measurements. However, Split-Fx overlays a simply 2D grid of equal-sized triangles onto the 3D surface and requires significant user input. In a more automated approach, we have developed a MATLAB script which directly imports the Polyworks 3D triangular mesh. A typical mesh is composed of over 1 million triangles of variable sizes: smooth regions are represented by large triangles, whereas rough surfaces are captured by several smaller triangles. Using the triangle vertices, the script computes the strike and dip of each triangle. This approach opens possibilities for statistical analysis of a large population of fracture orientation estimates, including surface texture. The methodology will be used to evaluate both synthetic and field data.

Kinematics of wrench and divergent-wrench deformation along a central part of the Border Ranges Fault System, Northern Chugach Mountains, Alaska

NASA Astrophysics Data System (ADS)

Little, Timothy A.

1990-08-01

The Border Ranges fault system (BRFS) bounds the inboard edge of the subduction-accretion complex of southern Alaska. In Eocene time a central segment of this fault system was reactivated as a zone of dextral wrench- and oblique-slip faulting having a cumulative strike-slip offset of at least several tens of kilometers, but probably less than 100 km. Early wrench folds are upright, trend at less than 45° to the strike of adjacent faults and developed with fold axes oriented subparallel to the axis of maximum incremental stretch λ1. These en echelon folds rotated and tightened with progressive deformation and then were overprinted by younger wrench folds that trend at about 60° to adjacent throughgoing faults. The latter folds are interpreted as forming during a late increment of distributed wrench deformation within the BRFS that included a component of extension (divergence) orthogonal to the mean strike of the fault system. A sharp releasing bend in exposures of a strike-slip fault originally at >4 km depth today coincides with a narrow pull-apart graben bounded by oblique-normal faults that dip toward the basin. Widening of this pull-apart graben by brittle faulting and dike intrusion accommodated less than 2 km of strike-slip and was a late-stage phenomenon, possibly occurring at supracrustal levels. Prior to formation of this graben during a period of predominantly ductile deformation at deeper structural levels, wrench-folded rocks on one side of the nonplanar fault were translated around the releasing bend without significant faulting or loss of coherence. Kinematically, the earlier deformation was accomplished by fault-bend folding and rotation of a relatively deformable block as it passed through a system of upright megakinks. Such a ductile mechanism of fault block translation around a strike-slip bend may be typical of intermediate levels of the crust beneath pull-apart grabens and may be transitional downward into heterogeneous laminar flow occuring along curved segments of ductile shear zones. Some degree of fault-bend folding of strike-slip fault blocks around releasing bends may be one reason why the amount of extension measured across natural pull-apart basins is commonly observed to be less than the amount of strike-slip along their master faults.

Three-dimensional fault framework of the 2014 South Napa Earthquake, San Francisco Bay region, California

NASA Astrophysics Data System (ADS)

Graymer, R. W.

2014-12-01

Assignment of the South Napa earthquake to a mapped fault is difficult, as it occurred where three large, northwest-trending faults converge and may interact in the subsurface. The surface rupture did not fall on the main trace of any of these faults, but instead between the Carneros and West Napa faults and northwest along strike from the northern mapped end of the Franklin Fault. The 2014 rupture plane appears to be nearly vertical, based on focal mechanisms of the mainshock and connection of the surface trace/rupture to the relocated hypocenter (J. Hardebeck, USGS). 3D surfaces constructed from published data show that the Carneros Fault is a steeply west-dipping fault that runs just west of the near-vertical 2014 rupture plane. The Carneros Fault does not appear to have been involved in the earthquake, although relocated aftershocks suggest possible minor triggered slip. The main West Napa Fault is also steeply west-dipping and that its projection intersects the 2014 rupture plane at around the depth of the mainshock hypocenter. UAVSAR data (A. Donnellan, JPL) and relocated aftershocks suggest that the main West Napa Fault experienced triggered slip/afterslip along a length of roughly 20 km. It is possible that the 2014 rupture took place along a largely unrecognized westerly strand of the West Napa Fault. The Franklin Fault is a steeply east-dipping fault (with a steeply west-dipping subordinate trace east of Mare Island) that has documented late Quaternary offset. Given the generally aligned orientation of the 3D fault surfaces, an alternative interpretation is that the South Napa earthquake occurred on the northernmost reach of the Franklin Fault within it's 3D junction with the West Napa Fault. This interpretation is supported, but not proven, by a short but prominent linear feature in the UAVSAR data at Slaughterhouse Point west of Vallejo, along trend south-southeast of the observed coseismic surface rupture.

Seismic Reflectivity of the Crust in the Northern Salton Trough

NASA Astrophysics Data System (ADS)

Bauer, K.; Fuis, G. S.; Goldman, M.; Persaud, P.; Ryberg, T.; Langenheim, V. E.; Scheirer, D. S.; Rymer, M. J.; Hole, J. A.; Stock, J. M.; Catchings, R.

2015-12-01

The Salton Trough in southern California is a tectonically active pull-apart basin that was formed by migrating step-overs between strike-slip faults, of which the San Andreas Fault (SAF) and the Imperial Fault are the current, northernmost examples. The Salton Seismic Imaging Project (SSIP) was undertaken to improve our knowledge of fault geometry and seismic velocities within the sedimentary basins and underlying crystalline crust around the SAF. Such data are useful as input for modeling scenarios of strong ground shaking in the surrounding high-population areas. We used pre-stack depth migration of line segments from shot gathers in several seismic profiles that were acquired in the northern part of the SSIP study area (Lines 4 - 7). Our migration approach can be considered as an infinite-frequency approximation of the Fresnel volume pre-stack depth migration method. We use line segments instead of the original waveform data. We demonstrate the method using synthetic data and analyze real data from Lines 4 - 7 to illustrate the relationship between distinct phases in the time domain and their resulting image at depth. We show both normal-moveout reflections from sub-horizontal interfaces and reverse-moveout reflections from steep interfaces, such as faults. Migrated images of dipping faults, such as the SAF and the Pinto Mountain Fault, are presented in this way. The SAF is imaged along Line 4, through the Mecca Hills, as a number of steeply dipping fault segments that collectively form a flower structure, above 5 km depth, that sole into a moderately NE-dipping fault below that depth. The individual migrated reflection packages correlate with mapped surface fault traces in the Mecca Hills. A similar geometry is seen on Line 6, from Palm Springs through Yucca Valley, where fault splays sole or project into a moderately dipping SAF below 10-km depth. We also show and discuss the reflectivity pattern of the middle and lower crust for Lines 4 - 7.

A paleoseismic transect across the northwestern Basin and Range Province, northwestern Nevada and northeastern California, USA

USGS Publications Warehouse

Personius, Stephen; Briggs, Richard; Maharrey, J. Zebulon; Angster, Stephen J.; Mahan, Shannon

2017-01-01

We use new and existing data to compile a record of ∼18 latest Quaternary large-magnitude surface-rupturing earthquakes on 7 fault zones in the northwestern Basin and Range Province of northwestern Nevada and northeastern California. The most recent earthquake on all faults postdates the ca. 18–15 ka last glacial highstand of pluvial Lake Lahontan and other pluvial lakes in the region. These lacustrine data provide a window in which we calculate latest Quaternary vertical slip rates and compare them with rates of modern deformation in a global positioning system (GPS) transect spanning the region. Average vertical slip rates on these fault zones range from 0.1 to 0.8 mm/yr and total ∼2 mm/yr across a 265-km-wide transect from near Paradise Valley, Nevada, to the Warner Mountains in California. We converted vertical slip rates to horizontal extension rates using fault dips of 30°–60°, and then compared the extension rates to GPS-derived rates of modern (last 7–9 yr) deformation. Our preferred fault dip values (45°–55°) yield estimated long-term extension rates (1.3–1.9 mm/yr) that underestimate our modern rate (2.4 mm/yr) by ∼21%–46%. The most likely sources of this underestimate are geologically unrecognizable deformation from moderate-sized earthquakes and unaccounted-for coseismic off-fault deformation from large surface-rupturing earthquakes. However, fault dip values of ≤40° yield long-term rates comparable to or greater than modern rates, so an alternative explanation is that fault dips are closer to 40° than our preferred values. We speculate that the large component of right-lateral shear apparent in the GPS signal is partitioned on faults with primary strike-slip displacement, such as the Long Valley fault zone, and as not easily detected oblique slip on favorably oriented normal faults in the region.

Structural interpretation from horizontal seismic sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, A.R.

1983-03-01

The interpreter of a 3D survey must use a data volume. Horizontal slices through a data volume, called Seiscrop sections, have unique properties and structural interpretation from them is fast, convenient, and effective. An event on a Seiscrop section displays local strike, a property which permits direct contouring of a structural surface without any timing and posting. The width of an event on a Seiscrop section is a composition of the frequency of the data and the structural dip. Event terminations indicate faults or other discontinuities when they are transverse to structural strike. Faults parallel to structural strike are muchmore » less evident on a single Seiscrop section but become apparent with the relative movement of events from section to section. In practical mapping, we normally contour one fault block before proceeding to the next with the correlation between them being established from the vertical sections. With dual polarity variable area displays, the interpreter can perceive five amplitude levels and normally picks the edge of a trough. With color amplitude Seiscrop sections, it is possible to pick on the crest of any event. With color phase sections the interpreter can pick at any arbitrary but consistent point on the seismic waveform. Subtle structural features are commonly revealed on horizontal sections which may never have been noticed if working from vertical sections alone.« less

Analysis of macroscopic fractures in granite in the HDR geothermal well EPS-1, Soultz-sous-Foreêts, France

NASA Astrophysics Data System (ADS)

Genter, Albert; Traineau, Hervé

1996-07-01

An exhaustive analysis of 3000 macroscopic fractures encountered in the geothermal Hot Dry Rock borehole, EPS-1, located inside the Rhine graben (Soultz-sous-Foreˆts, France), was done on a continuous core section over a depth interval from 1420 to 2230 m: 97% of the macroscopic structures were successfully reorientated with a good degree of confidence by comparison between core and acoustic borehole imagery. Detailed structural analysis of the fracture population indicates that fractures are grouped in two principal fractures sets striking N005 and N170 °, and dipping 70 °W and 70 °E, respectively. This average attitude is closely related to the past tectonic rifting activity of the graben during the Tertiary, and is consistent with data obtained from nearby boreholes and from neighbouring crystalline outcrops. Fractures are distributed in clusters of hydrothermally altered and fractured zones. They constitute a complex network of fault strands dominated by N-S trends, except within some of the most fractured depth intervals (1650 m, 2170 m), where an E-W-striking fracture set occurs. The geometry of the pre-existing fracture system strikes in a direction nearly parallel to the maximum horizontal stress. In this favorable situation, hydraulic injections will tend both to reactivate natural fractures at low pressures, and to create a geothermal reservoir.

Effects of anisotropy on the two-dimensional inversion procedure

NASA Astrophysics Data System (ADS)

Heise, Wiebke; Pous, Jaume

2001-12-01

In this paper we show some of the effects that appear in magnetotelluric measurements over 2-D anisotropic structures, and propose a procedure to recover the anisotropy using 2-D inversion algorithms for isotropic models. First, we see how anisotropy affects the usual interpretation steps: dimensionality analysis and 2-D inversion. Two models containing general 2-D azimuthal anisotropic features were chosen to illustrate this approach: an anisotropic block and an anisotropic layer, both forming part of general 2-D models. In addition, a third model with dipping anisotropy was studied. For each model we examined the influence of various anisotropy strikes and resistivity contrasts on the dimensionality analysis and on the behaviour of the induction arrows. We found that, when the anisotropy ratio is higher than five, even if the strike is frequency-dependent it is possible to decide on a direction close to the direction of anisotropy. Then, if the data are rotated to this angle, a 2-D inversion reproduces the anisotropy reasonably well by means of macro-anisotropy. This strategy was tested on field data where anisotropy had been previously recognized.

Active tectonics and strain partitioning along dextral fault system in Central Iran: Analysis of geomorphological observations and geophysical data in the Kashan region

NASA Astrophysics Data System (ADS)

Jamali, Farshad; Hessami, Khaled; Ghorashi, Manoochehr

2011-03-01

This paper uses high-resolution images and field investigations, in conjunction with seismic reflection data, to constrain active structural deformation in the Kashan region of Central Iran. Offset stream beds and Qanats indicate right-lateral strike slip motion at a rate of about 2 mm/yr along the NW-SE trending Qom-Zefreh fault zone which has long been recognized as one of the major faults in Central Iran. However, the pattern of drainage systems across the active growing folds including deep incision of stream beds and deflected streams indicate uplift at depth on thrust faults dipping SW beneath the anticlines. Therefore, our studies in the Kashan region indicate that deformation occurs within Central Iran which is often considered to behave as a non-deforming block within the Arabia-Eurasia collision zone. The fact that the active Qom-Zefreh strike-slip fault runs parallel to the active folds, which overlie blind thrust faults, suggests that oblique motion of Arabia with respect to Eurasia is partitioned in this part of Central Iran.

Tectonics earthquake distribution pattern analysis based focal mechanisms (Case study Sulawesi Island, 1993–2012)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ismullah M, Muh. Fawzy, E-mail: mallaniung@gmail.com; Lantu,; Aswad, Sabrianto

Indonesia is the meeting zone between three world main plates: Eurasian Plate, Pacific Plate, and Indo – Australia Plate. Therefore, Indonesia has a high seismicity degree. Sulawesi is one of whose high seismicity level. The earthquake centre lies in fault zone so the earthquake data gives tectonic visualization in a certain place. This research purpose is to identify Sulawesi tectonic model by using earthquake data from 1993 to 2012. Data used in this research is the earthquake data which consist of: the origin time, the epicenter coordinate, the depth, the magnitude and the fault parameter (strike, dip and slip). Themore » result of research shows that there are a lot of active structures as a reason of the earthquake in Sulawesi. The active structures are Walannae Fault, Lawanopo Fault, Matano Fault, Palu – Koro Fault, Batui Fault and Moluccas Sea Double Subduction. The focal mechanism also shows that Walannae Fault, Batui Fault and Moluccas Sea Double Subduction are kind of reverse fault. While Lawanopo Fault, Matano Fault and Palu – Koro Fault are kind of strike slip fault.« less

Surface Rupture Effects on Earthquake Moment-Area Scaling Relations

NASA Astrophysics Data System (ADS)

Luo, Yingdi; Ampuero, Jean-Paul; Miyakoshi, Ken; Irikura, Kojiro

2017-09-01

Empirical earthquake scaling relations play a central role in fundamental studies of earthquake physics and in current practice of earthquake hazard assessment, and are being refined by advances in earthquake source analysis. A scaling relation between seismic moment ( M 0) and rupture area ( A) currently in use for ground motion prediction in Japan features a transition regime of the form M 0- A 2, between the well-recognized small (self-similar) and very large (W-model) earthquake regimes, which has counter-intuitive attributes and uncertain theoretical underpinnings. Here, we investigate the mechanical origin of this transition regime via earthquake cycle simulations, analytical dislocation models and numerical crack models on strike-slip faults. We find that, even if stress drop is assumed constant, the properties of the transition regime are controlled by surface rupture effects, comprising an effective rupture elongation along-dip due to a mirror effect and systematic changes of the shape factor relating slip to stress drop. Based on this physical insight, we propose a simplified formula to account for these effects in M 0- A scaling relations for strike-slip earthquakes.

Slip and Dilation Tendency Analysis of the San Emidio Geothermal Area

DOE Data Explorer

Faulds, James E.

2013-12-31

Critically stressed fault segments have a relatively high likelihood of acting as fluid flow conduits (Sibson, 1994). As such, the tendency of a fault segment to slip (slip tendency; Ts; Morris et al., 1996) or to dilate (dilation tendency; Td; Ferrill et al., 1999) provides an indication of which faults or fault segments within a geothermal system are critically stressed and therefore likely to transmit geothermal fluids. The slip tendency of a surface is defined by the ratio of shear stress to normal stress on that surface: Ts = τ / σn (Morris et al., 1996). Dilation tendency is defined by the stress acting normal to a given surface: Td = (σ1-σn) / (σ1-σ3) (Ferrill et al., 1999). Slip and dilation were calculated using 3DStress (Southwest Research Institute). Slip and dilation tendency are both unitless ratios of the resolved stresses applied to the fault plane by ambient stress conditions. Values range from a maximum of 1, a fault plane ideally oriented to slip or dilate under ambient stress conditions to zero, a fault plane with no potential to slip or dilate. Slip and dilation tendency values were calculated for each fault in the focus study areas at, McGinness Hills, Neal Hot Springs, Patua, Salt Wells, San Emidio, and Tuscarora on fault traces. As dip is not well constrained or unknown for many faults mapped in within these we made these calculations using the dip for each fault that would yield the maximum slip tendency or dilation tendency. As such, these results should be viewed as maximum tendency of each fault to slip or dilate. The resulting along-fault and fault-to-fault variation in slip or dilation potential is a proxy for along fault and fault-to-fault variation in fluid flow conduit potential. Stress Magnitudes and directions Stress field variation within each focus area was approximated based on regional published data and the world stress database (Hickman et al., 2000; Hickman et al., 1998 Robertson-Tait et al., 2004; Hickman and Davatzes, 2010; Davatzes and Hickman, 2006; Blake and Davatzes 2011; Blake and Davatzes, 2012; Moeck et al., 2010; Moos and Ronne, 2010 and Reinecker et al., 2005) as well as local stress information if applicable. For faults within these focus systems we applied either a normal faulting stress regime where the vertical stress (sv) is larger than the maximum horizontal stress (shmax) which is larger than the minimum horizontal stress (sv>shmax>shmin) or strike-slip faulting stress regime where the maximum horizontal stress (shmax) is larger than the vertical stress (sv) which is larger than the minimum horizontal stress (shmax >sv>shmin) depending on the general tectonic province of the system. Based on visual inspection of the limited stress magnitude data in the Great Basin we used magnitudes such that shmin/shmax = .527 and shmin/sv= .46, which are consistent with complete and partial stress field determinations from Desert Peak, Coso, the Fallon area and Dixie valley (Hickman et al., 2000; Hickman et al., 1998 Robertson-Tait et al., 2004; Hickman and Davatzes, 2011; Davatzes and Hickman, 2006; Blake and Davatzes 2011; Blake and Davatzes, 2012). Slip and dilation tendency for the San Emidio geothermal field was calculated based on the faults mapped Tuscarora area (Rhodes, 2011). The San Emidio area lies in the Basin and Range Province, as such we applied a normal faulting stress regime to the San Emidio area faults, with a minimum horizontal stress direction oriented 115, based on inspection of local and regional stress determinations, as explained above. This is consistent with the shmin determined through inversion of fault data by Rhodes (2011). Under these stress conditions north-northeast striking, steeply dipping fault segments have the highest dilation tendency, while north-northeast striking 60° dipping fault segments have the highest tendency to slip. Interesting, the San Emidio geothermal field lies in an area of primarily north striking faults, which...

Mechanical stratigraphic controls on natural fracture spacing and penetration

NASA Astrophysics Data System (ADS)

McGinnis, Ronald N.; Ferrill, David A.; Morris, Alan P.; Smart, Kevin J.; Lehrmann, Daniel

2017-02-01

Fine-grained low permeability sedimentary rocks, such as shale and mudrock, have drawn attention as unconventional hydrocarbon reservoirs. Fracturing - both natural and induced - is extremely important for increasing permeability in otherwise low-permeability rock. We analyze natural extension fracture networks within a complete measured outcrop section of the Ernst Member of the Boquillas Formation in Big Bend National Park, west Texas. Results of bed-center, dip-parallel scanline surveys demonstrate nearly identical fracture strikes and slight variation in dip between mudrock, chalk, and limestone beds. Fracture spacing tends to increase proportional to bed thickness in limestone and chalk beds; however, dramatic differences in fracture spacing are observed in mudrock. A direct relationship is observed between fracture spacing/thickness ratio and rock competence. Vertical fracture penetrations measured from the middle of chalk and limestone beds generally extend to and often beyond bed boundaries into the vertically adjacent mudrock beds. In contrast, fractures in the mudrock beds rarely penetrate beyond the bed boundaries into the adjacent carbonate beds. Consequently, natural bed-perpendicular fracture connectivity through the mechanically layered sequence generally is poor. Fracture connectivity strongly influences permeability architecture, and fracture prediction should consider thin bed-scale control on fracture heights and the strong lithologic control on fracture spacing.

Triggered reverse fault and earthquake due to crustal unloading, northwest Transverse Ranges, California.

USGS Publications Warehouse

Yerkes, R.F.; Ellsworth, W.L.; Tinsley, J.C.

1983-01-01

A reverse-right-oblique surface rupture, associated with a ML 2.5 earthquake, formed in a diatomite quarry near Lompoc, California, in the northwesternmost Transverse Ranges on April 7, 1981. The 575-m-long narrow zone of ruptures formed in clay interbeds in diatomite and diatomaceous shale of the Neogene Monterey Formation. The ruptures parallel bedding, dip 39o-59oS, and trend about N84oE on the north limb of an open symmetrical syncline. Maximum net slip was 25 cm; maximum reverse dip slip was 23 cm, maximum right-lateral strike slip was about 9 cm, and average net slip was about 12 cm. The seismic moment of the earthquake is estimated at 1 to 2 X 1018 dyne/cm and the static stress drop at about 3 bar. The removal of an average of about 44 m of diatomite resulted in an average load reduction of about 5 bar, which decreased the normal stress by about 3.5 bar and increased the shear stress on the tilted bedding plane by about 2 bar. The April 7, 1981, event was a very shallow bedding-plane rupture, apparently triggered by crustal unloading. -Authors

Analysis of Seismotektonic Patterns in Sumatra Region Based on the Focal Mechanism of Earthquake Period 1976-2016

NASA Astrophysics Data System (ADS)

Indah, F. P.; Syafriani, S.; Andiyansyah, Z. S.

2018-04-01

Sumatra is in an active subduction zone between the indo-australian plate and the eurasian plate and is located at a fault along the sumatra fault so that sumatra is vulnerable to earthquakes. One of the ways to find out the cause of earthquake can be done by identifying the type of earthquake-causing faults based on earthquake of focal mechanism. The data used to identify the type of fault cause of earthquake is the earth tensor moment data which is sourced from global cmt period 1976-2016. The data used in this research using magnitude m ≥ 6 sr. This research uses gmt software (generic mapping tolls) to describe the form of fault. From the research result, it is found that the characteristics of fault field that formed in every region in sumatera island based on data processing and data of earthquake history of 1976-2016 period that the type of fault in sumatera fault is strike slip, fault type in mentawai fault is reverse fault (rising faults) and dip-slip, while the fault type in the subduction zone is dip-slip.

Borehole sampling of fracture populations - compensating for borehole sampling bias in crystalline bedrock aquifers, Mirror Lake, Grafton County, New Hampshire

USGS Publications Warehouse

McDonald, G.D.; Paillet, Frederick L.; Barton, C.C.; Johnson, C.D.

1997-01-01

The clustering of orientations of hydraulically conductive fractures in bedrock at the Mirror Lake, New Hampshire fractured rock study site was investigated by comparing the orientations of fracture populations in two subvertical borehole arrays with those mapped on four adjacent subvertical roadcuts. In the boreholes and the roadcuts, the orientation of fracture populations appears very similar after borehole data are compensated for undersampling of steeply dipping fractures. Compensated borehole and pavement fracture data indicate a northeast-striking population of fractures with varying dips concentrated near that of the local foliation in the adjacent rock. The data show no correlation between fracture density (fractures/linear meter) and distance from lithologic contacts in both the boreholes and the roadcuts. The population of water-producing borehole fractures is too small (28 out of 610 fractures) to yield meaningful orientation comparisons. However, the orientation of large aperture fractures (which contains all the producing fractures) contains two or three subsidiary clusters in orientation frequency that are not evident in stereographic projections of the entire population containing all aperture sizes. Further, these subsidiary orientation clusters do not coincide with the dominant (subhorizontal and subvertical) regional fracture orientations.

Up-dip partitioning of displacement components on the oblique-slip Clarence Fault, New Zealand

NASA Astrophysics Data System (ADS)

Nicol, Andrew; Van Dissen, Russell

2002-09-01

Active strike-slip faults in New Zealand occur within an obliquely-convergent plate boundary zone. Although the traces of these faults commonly delineate the base of mountain ranges, they do not always accommodate significant shortening at the free surface. Along the active trace of Clarence Fault in northeastern South Island, New Zealand, displaced landforms and slickenside striations indicate predominantly horizontal displacements at the ground surface, and a right-lateral slip rate of ca. 3.5-5 mm/year during the Holocene. The Inland Kaikoura mountain range occupies the hanging wall of the fault and rises steeply from the active trace to altitudes of ca. 3 km. The geomorphology of the range indicates active uplift and mountain building, which is interpreted to result, in part, from a vertical component of fault slip at depth. These data are consistent with the fault accommodating oblique-slip at depth aligned parallel to the plate-motion vector and compatible with regional geodetic data and earthquake focal-mechanisms. Oblique-slip on the Clarence Fault at depth is partitioned at the free surface into: (1) right-lateral displacement on the fault, and (2) hanging wall uplift produced by distributed displacement on small-scale faults parallel to the main fault. Decoupling of slip components reflects an up-dip transfer of fault throw to an off-fault zone of distributed uplift. Such zones are common in the hanging walls of thrusts and reverse faults, and support the idea that the dip of the oblique-slip Clarence Fault steepens towards the free surface.

Rapid middle Miocene extension and unroofing of the southern Ruby Mountains, Nevada

USGS Publications Warehouse

Colgan, Joseph P.; Howard, Keith A.; Fleck, Robert J.; Wooden, Joseph L.

2010-01-01

Paleozoic rocks in the northern Ruby Mountains were metamorphosed during Mesozoic crustal shortening and Cenozoic magmatism, but equivalent strata in the southern Ruby Mountains were never buried deeper than stratigraphic depths prior to exhumation in the footwall of a west dipping brittle normal fault. In the southern Ruby Mountains, Miocene sedimentary rocks in the hanging wall of this fault date from 15.2 to 11.6 Ma and contain abundant detritus from the Paleozoic section. Apatite fission track and (U-Th)/He samples of the Eocene Harrison Pass pluton record rapid cooling that peaked ca. 17–15 Ma, while apatite fission track data from Jurassic plutons east and west of the southern Ruby Mountains indicate near-surface temperatures (<60°C) since the Cretaceous. We interpret these data to record rapid unroofing of the southern Ruby Mountains during slip on the west dipping brittle detachment between 17–16 and 10–12 Ma, followed by minor high-angle faulting. We interpret published Oligocene to early Miocene K-Ar biotite and zircon fission track dates from the Harrison Pass pluton to be partially reset rather than to directly record fault slip. Our new data, together with published data on the distribution and composition of Miocene basin fill, suggest that rapid middle Miocene slip took place on the west dipping brittle detachment that bounds the Ruby Mountains and East Humboldt Range for 150 km along strike. This fault was thus active during a period of rapid extension (ca. 17–15 to 12–10 Ma) documented widely across the northern Basin and Range Province.

Supra-subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics

USGS Publications Warehouse

Kim, J.; Coish, R.; Evans, M.; Dick, G.

2003-01-01

Metadiabasic intrusions of the Mount Norris Intrusive Suite occur in fault-bounded lithotectonic packages containing Stowe, Moretown, and Cram Hill Formation lithologies in the northern Vermont Rowe-Hawley belt, a proposed Ordovician arc-trench gap above an east-dipping subduction zone. Rocks of the Mount Norris Intrusive Suite are characteristically massive and weakly foliated, have chilled margins, contain xenoliths, and have sharp contacts that both crosscut and are parallel to early structural fabrics in the host metasedimentary rocks. Although the mineral assemblage of the Mount Norris Intrusive Suite is albite + actinolite + epidote + chlorite + calcite + quartz, intergrowths of albite + actinolite are probably pseudomorphs after plagioclase + clinopyroxene. The metadiabases are subalkaline, tholeiitic, hypabyssal basalts with preserved ophitic texture. A backarc-basin tectonic setting for the intrusive suite is suggested by its LREE (light rare earth element) enrichment, negative Nb-Ta anomalies, and Ta/Yb vs. Th/Yb trends. Although no direct isotopic age data are available, the intrusions are broadly Ordovician because their contacts are clearly folded by the earliest Acadian (Silurian-Devonian) folds. Field evidence and geochemical data suggest compelling along-strike correlations with the Coburn Hill Volcanics of northern Vermont and the Bolton Igneous Group of southern Quebec. Isotopic and stratigraphic age constraints for the Bolton Igneous Group bracket these backarc magmas to the 477-458 Ma interval. A tectonic model that begins with east-dipping subduction and progresses to outboard west-dipping subduction after a syncollisional polarity reversal best explains the intrusion of deformed metamorphosed metasedimentary rocks by backarc magmas.

Sequence stratigraphic re-interpretation of [open quotes]stray[close quotes] sandstones in the Cretaceous Mancos Shale, Book Cliffs, Utah: Implications for exploration models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hampson, G.J.; Howell, J.A.; Flint, S.S.

1996-01-01

The Mancos Shale, Book Cliffs, eastern Utah, represents the open marine mudstones of the Cretaceous Western Interior Seaway and contains a number of detached sandstone bodies ([open quotes]Mancos B[close quotes]) which are located 30-150 km down depositional dip from contemporaneous highstand shoreline deposits in the Blackhawk Formation. Examination of these [open quotes]stray[close quotes] sandstones reveals that they do not represent deep water deposition, as previously supposed, but instead comprise three shallow marine facies associations; (1) tidally-influenced fluvial channel fills, (2) fluvially-dominated delta front successions and (3) low-energy shorelines. Tidally-influenced fluvial channel fills are commonly stacked into multistorey bodies at discretemore » stratigraphic levels, thereby defining incised valley fill (IVF) networks. Fluvially-dominated deltas are eroded into by, and lie at the down-dip terminations of, IVFs and are therefore interpreted as falling stage and lowstand shorelines. Low-energy shorelines are inferred to lie along strike from these deltas. The above shallow marine deposits have been mapped at five discrete stratigraphic horizons, which can be either traced or projected up-dip to previously-documented IVFs in the Blackhawk Formation. Their paleocurrents imply that falling stage and lowstand shoreline trends were sub-parallel to mapped highstand shorelines, although there is evidence for a perpendicular lowstand shoreline trend in the east of the study area. This facies and sequence stratigraphic re-interpretation enables predictive exploration modelling of subsurface [open quotes]Mancos B[close quotes] gas reservoir sandstones.« less

Sequence stratigraphic re-interpretation of {open_quotes}stray{close_quotes} sandstones in the Cretaceous Mancos Shale, Book Cliffs, Utah: Implications for exploration models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hampson, G.J.; Howell, J.A.; Flint, S.S.

1996-12-31

The Mancos Shale, Book Cliffs, eastern Utah, represents the open marine mudstones of the Cretaceous Western Interior Seaway and contains a number of detached sandstone bodies ({open_quotes}Mancos B{close_quotes}) which are located 30-150 km down depositional dip from contemporaneous highstand shoreline deposits in the Blackhawk Formation. Examination of these {open_quotes}stray{close_quotes} sandstones reveals that they do not represent deep water deposition, as previously supposed, but instead comprise three shallow marine facies associations; (1) tidally-influenced fluvial channel fills, (2) fluvially-dominated delta front successions and (3) low-energy shorelines. Tidally-influenced fluvial channel fills are commonly stacked into multistorey bodies at discrete stratigraphic levels, thereby definingmore » incised valley fill (IVF) networks. Fluvially-dominated deltas are eroded into by, and lie at the down-dip terminations of, IVFs and are therefore interpreted as falling stage and lowstand shorelines. Low-energy shorelines are inferred to lie along strike from these deltas. The above shallow marine deposits have been mapped at five discrete stratigraphic horizons, which can be either traced or projected up-dip to previously-documented IVFs in the Blackhawk Formation. Their paleocurrents imply that falling stage and lowstand shoreline trends were sub-parallel to mapped highstand shorelines, although there is evidence for a perpendicular lowstand shoreline trend in the east of the study area. This facies and sequence stratigraphic re-interpretation enables predictive exploration modelling of subsurface {open_quotes}Mancos B{close_quotes} gas reservoir sandstones.« less

The complex evolution of transient slip revealed by precise tremor locations in western Shikoku, Japan

NASA Astrophysics Data System (ADS)

Shelly, D. R.; Beroza, G. C.; Ide, S.

2007-12-01

Transient slow slip events are increasingly being recognized as important components of strain release on faults and may substantially impact the earthquake cycle. Surface-based geodetic instruments provide estimates of the overall slip distribution in larger transients but are unable to capture the detailed evolution of such slip, either in time or space. Accompanying some of these slip transients is a relatively weak, extended duration seismic signal, known as non-volcanic tremor, which has recently been shown to be generated by a sequence of shear failures occurring as part of the slip event. By precisely locating the tremor, we can track some features of slip evolution with unprecedented resolution. Here, we analyze two weeklong episodes of tremor and slow slip in western Shikoku, Japan. We find that these slip transients do not evolve in a smooth and steady fashion but contain numerous sub-events of smaller size and shorter duration. In addition to along-strike migration rates of about 10 km/day observed previously, much faster migration also occurs, usually in the slab dip direction, at rates of 25-150 km/hour over distances of up to 20 km. We observe such migration episodes in both the up-dip and down-dip directions. These episodes may be most common on certain portions of the plate boundary that generate strong tremor in intermittent bursts. The surrounding regions of the fault may slip more continuously, driving these stronger patches to repeated failures. Tremor activity has a strong tidal periodicity, possibly reflecting the modulation of slow slip velocity by tidal stresses.

Along-strike Variations in the Himalayas Illuminated by the Aftershock Sequence of the 2015 Mw 7.8 Gorkha Earthquake Using the NAMASTE Local Seismic Network

NASA Astrophysics Data System (ADS)

Mendoza, M.; Ghosh, A.; Karplus, M. S.; Nabelek, J.; Sapkota, S. N.; Adhikari, L. B.; Klemperer, S. L.; Velasco, A. A.

2016-12-01

As a result of the 2015 Mw 7.8 Gorkha earthquake, more than 8,000 people were killed from a combination of infrastructure failure and triggered landslides. This earthquake produced 4 m of peak co-seismic slip as the fault ruptured 130 km east under densely populated cities, such as Kathmandu. To understand earthquake dynamics in this part of the Himalayas and help mitigate similar future calamities by the next destructive event, it is imperative to study earthquake activities in detail and improve our understanding of the source and structural complexities. In response to the Gorkha event, multiple institutions developed and deployed a 10-month long dense seismic network called NAMASTE. It blanketed a 27,650 km2 area, mainly covering the rupture area of the Gorkha earthquake, in order to capture the dynamic sequence of aftershock behavior. The network consisted of a mix of 45 broadband, short-period, and strong motion sensors, with an average spacing of 20 km. From the first 6 months of data, starting approximately 1.5 after the mainshock, we develop a robust catalog containing over 3,000 precise earthquake locations, and local magnitudes that range between 0.3 and 4.9. The catalog has a magnitude of completeness of 1.5, and an overall low b-value of 0.78. Using the HypoDD algorithm, we relocate earthquake hypocenters with high precision, and thus illustrate the fault geometry down to depths of 25 km where we infer the location of the gently-dipping Main Frontal Thrust (MFT). Above the MFT, the aftershocks illuminate complex structure produced by relatively steeply dipping faults. Interestingly, we observe sharp along-strike change in the seismicity pattern. The eastern part of the aftershock area is significantly more active than the western part. The change in seismicity may reflect structural and/or frictional lateral heterogeneity in this part of the Himalayan fault system. Such along-strike variations play an important role in rupture complexities and arresting the mainshock from rupturing further east. This catalog serves as a starting point for not only identifying the physical processes controlling the earthquake cycles, but also areas of increased stress, in this segment of the Himalayas.

Tectonic interpretation of the Andrew Bain transform fault: Southwest Indian Ocean

NASA Astrophysics Data System (ADS)

Sclater, John G.; Grindlay, Nancy R.; Madsen, John A.; Rommevaux-Jestin, Celine

2005-09-01

Between 25°E and 35°E, a suite of four transform faults, Du Toit, Andrew Bain, Marion, and Prince Edward, offsets the Southwest Indian Ridge (SWIR) left laterally 1230 km. The Andrew Bain, the largest, has a length of 750 km and a maximum transform domain width of 120 km. We show that, currently, the Nubia/Somalia plate boundary intersects the SWIR east of the Prince Edward, placing the Andrew Bain on the Nubia/Antarctica plate boundary. However, the overall trend of its transform domain lies 10° clockwise of the predicted direction of motion for this boundary. We use four transform-parallel multibeam and magnetic anomaly profiles, together with relocated earthquakes and focal mechanism solutions, to characterize the morphology and tectonics of the Andrew Bain. Starting at the southwestern ridge-transform intersection, the relocated epicenters follow a 450-km-long, 20-km-wide, 6-km-deep western valley. They cross the transform domain within a series of deep overlapping basins bounded by steep inward dipping arcuate scarps. Eight strike-slip and three dip-slip focal mechanism solutions lie within these basins. The earthquakes can be traced to the northeastern ridge-transform intersection via a straight, 100-km-long, 10-km-wide, 4.5-km-deep eastern valley. A striking set of seismically inactive NE-SW trending en echelon ridges and valleys, lying to the south of the overlapping basins, dominates the eastern central section of the transform domain. We interpret the deep overlapping basins as two pull-apart features connected by a strike-slip basin that have created a relay zone similar to those observed on continental transforms. This transform relay zone connects three closely spaced overlapping transform faults in the southwest to a single transform fault in the northeast. The existence of the transform relay zone accounts for the difference between the observed and predicted trend of the Andrew Bain transform domain. We speculate that between 20 and 3.2 Ma, an oblique accretionary zone jumping successively northward created the en echelon ridges and valleys in the eastern central portion of the domain. The style of accretion changed to that of a transform relay zone, during a final northward jump, at 3.2 Ma.