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Sample records for active seismic methods

  1. Active seismic experiment

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.; Watkins, J. S.; Talwani, P.

    1972-01-01

    The Apollo 16 active seismic experiment (ASE) was designed to generate and monitor seismic waves for the study of the lunar near-surface structure. Several seismic energy sources are used: an astronaut-activated thumper device, a mortar package that contains rocket-launched grenades, and the impulse produced by the lunar module ascent. Analysis of some seismic signals recorded by the ASE has provided data concerning the near-surface structure at the Descartes landing site. Two compressional seismic velocities have so far been recognized in the seismic data. The deployment of the ASE is described, and the significant results obtained are discussed.

  2. A Predictive Model of Daily Seismic Activity Induced by Mining, Developed with Data Mining Methods

    NASA Astrophysics Data System (ADS)

    Jakubowski, Jacek

    2014-12-01

    The article presents the development and evaluation of a predictive classification model of daily seismic energy emissions induced by longwall mining in sector XVI of the Piast coal mine in Poland. The model uses data on tremor energy, basic characteristics of the longwall face and mined output in this sector over the period from July 1987 to March 2011. The predicted binary variable is the occurrence of a daily sum of tremor seismic energies in a longwall that is greater than or equal to the threshold value of 105 J. Three data mining analytical methods were applied: logistic regression,neural networks, and stochastic gradient boosted trees. The boosted trees model was chosen as the best for the purposes of the prediction. The validation sample results showed its good predictive capability, taking the complex nature of the phenomenon into account. This may indicate the applied model's suitability for a sequential, short-term prediction of mining induced seismic activity.

  3. Fault Activity Investigations in the Lower Tagus Valley (Portugal) With Seismic and Geoelectric Methods

    NASA Astrophysics Data System (ADS)

    Carvalho, J. G.; Gonçalves, R.; Torres, L. M.; Cabral, J.; Mendes-Victor, L. A.

    2004-05-01

    The Lower Tagus River Valley is located in Central Portugal, and includes a large portion of the densely populated area of Lisbon. It is sited in the Lower Tagus Cenozoic Basin, a tectonic depression where up to 2,000 m of Cenozoic sediments are preserved, which was developed in the Neogene as a compressive foredeep basin related to tectonic inversion of former Mesozoic extensional structures. It is only a few hundred kilometers distant from the Eurasia-Africa plate boundary, and is characterized by a moderate seismicity presenting a diffuse pattern, with historical earthquakes having caused serious damage, loss of lives and economical problems. It has therefore been the target of several seismic hazard studies in which extensive geological and geophysical research was carried out on several geological structures. This work focuses on the application of seismic and geoelectric methods to investigate an important NW-SE trending normal fault detected on deep oil-industry seismic reflection profiles in the Tagus Cenozoic Basin. In these seismic sections this fault clearly offsets horizons that are ascribed to the Upper Miocene. However, due to the poor near surface resolution of the seismic data and the fact that the fault is hidden under the recent alluvial cover of the Tagus River, it was not clear whether it displaced the upper sediments of Holocene age. In order to constrain the fault geometry and kinematics and to evaluate its recent tectonic activity, a few high-resolution seismic reflection profiles were acquired and refraction interpretation of the reflection data was performed. Some vertical electrical soundings were also carried out. A complex fault system was detected, apparently with normal and reverse faulting. The collected data strongly supports the possibility that one of the detected faults affects the uppermost Neogene sediments and very probably the Holocene alluvial sediments of the Tagus River. The evidence of recent activity on this fault, its

  4. Seismic properties of fluid bearing formations in magmatic geothermal systems: can we directly detect geothermal activity with seismic methods?

    NASA Astrophysics Data System (ADS)

    Grab, Melchior; Scott, Samuel; Quintal, Beatriz; Caspari, Eva; Maurer, Hansruedi; Greenhalgh, Stewart

    2016-04-01

    Seismic methods are amongst the most common techniques to explore the earth's subsurface. Seismic properties such as velocities, impedance contrasts and attenuation enable the characterization of the rocks in a geothermal system. The most important goal of geothermal exploration, however, is to describe the enthalpy state of the pore fluids, which act as the main transport medium for the geothermal heat, and to detect permeable structures such as fracture networks, which control the movement of these pore fluids in the subsurface. Since the quantities measured with seismic methods are only indirectly related with the fluid state and the rock permeability, the interpretation of seismic datasets is difficult and usually delivers ambiguous results. To help overcome this problem, we use a numerical modeling tool that quantifies the seismic properties of fractured rock formations that are typically found in magmatic geothermal systems. We incorporate the physics of the pore fluids, ranging from the liquid to the boiling and ultimately vapor state. Furthermore, we consider the hydromechanics of permeable structures at different scales from small cooling joints to large caldera faults as are known to be present in volcanic systems. Our modeling techniques simulate oscillatory compressibility and shear tests and yield the P- and S-wave velocities and attenuation factors of fluid saturated fractured rock volumes. To apply this modeling technique to realistic scenarios, numerous input parameters need to be indentified. The properties of the rock matrix and individual fractures were derived from extensive literature research including a large number of laboratory-based studies. The geometries of fracture networks were provided by structural geologists from their published studies of outcrops. Finally, the physical properties of the pore fluid, ranging from those at ambient pressures and temperatures up to the supercritical conditions, were taken from the fluid physics

  5. Melt-Triggered Seismic Response in Hydraulically-Active Polar Ice: Observations and Methods

    NASA Astrophysics Data System (ADS)

    Carmichael, Joshua D.

    Glacier ice responds to environmental forcing through changes in its sliding speed and mass balance. While these changes often occur on daily time scales or longer, they are initiated by brittle deformation events that establish hydrological pathways in hours or seconds and allow meltwater access to englacial or subglacial depths to facilitate ice motion. In this thesis, we (various contributing authors including myself) use seismic monitoring to detect and locate the creation and growth of some of these hydraulic pathways by monitoring their seismic emissions, or icequakes. More specifically, we address (1) what seismic observables, unavailable from other sensing methods, indicate an initial glaciogenic response to melt- water input and (2) if these comprise evidence of feedbacks that may destabilize polar ice under a warming climate. Supplemental to our scientific contributions, we advance statistical processing methods that demonstrably improve the capability of digital detectors at discriminating icequakes from astationary noise. We begin by interpreting geophysical observations collected from a dry-based, sub-freezing (--17 ° C), polar glacier environment (Taylor Glacier, ANT). By implementing a calibrated surface energy balance model, we estimate the timing and volume of surface meltwater generated during the collection of seismic data from a six-receiver geophone network. We proceed by contrasting these response characteristics with geophysical observations following an early (spring) supraglacial lake drainage within the lake-forming ablation zone of the Western Greenland Ice Sheet. Using measurements from a ˜5km-aperture geophone network, we find that the anticipated post-drainage icequakes are diurnally responsive, largely surficial in origin, and indicative of tensile fracturing from shallow cracks in the ice. The creation of the lake-drainage moulin appears to coincide with a shift in mean icequake source locations, and an increase in icequake

  6. Combined Active and Passive Seismic Methods To Characterize Strongmotion Sites in Washington and Oregon, United States

    NASA Astrophysics Data System (ADS)

    Pileggi, D.; Cakir, R.; Lunedei, E.; Albarello, D.; Walsh, T. J.

    2011-12-01

    Knowledge of the shear-wave velocity profile at strongmotion station sites is important for calibrating accelerograms in terms of local site effects. Surface-wave seismic prospecting methods (both in active and passive configurations) provide an effective tool for an inexpensive and deep penetrating seismic characterization of subsoil. We used a combination of active (Multi-channel Analysis of Surface Waves, MASW) and passive (Extended Spectral AutoCorrelation, ESAC) array techniques along with the single-station ambient vibration measurements (Horizontal-to-Vertical Spectral Ratios - HVSR) to characterize strong-motion sites in Washington and Oregon. The MASW analysis was used to better constrain the shallowest part of the Vs profile, while effective dispersion curve provided by ESAC and HVSR data allow us to extend the survey downwards (up to hundred meters of depth). The combined use of these data in the frame of global-search inversion algorithms (Genetic Algorithms) allows us to manage the extreme non-linearity of the inverse problem and mitigate problems associated with the non-uniqueness of the solution. A strict synergy between geologic surveys, boreholes (when the latter was available) and seismic surveys allows a further reduction of relevant uncertainties. Preliminary results show that; i) this combined methodology is a practical, inexpensive, and fast way to characterize multiple strong motion sites; ii) local geology and/or borehole information was combined to better constrain the inversion and to reduce the uncertainty in velocity profiles; and, iii) this combined methodology gives additional information of shear-wave velocities at greater depths.

  7. Comparison of Active and Passive Seismic Methods for Calculating Shear-wave Velocity Profiles: An Example from Hartford County, Connecticut

    NASA Astrophysics Data System (ADS)

    Morton, S.; Lane, J. W.; Liu, L.; Thomas, M. A.

    2013-12-01

    Seismic hazard classifications have been developed for Hartford County, Connecticut based primarily on mapping of surficial materials and depositional environment using criteria specified by the National Earthquake Hazard Reduction Program (NEHRP). A study using near-surface seismic techniques to measure shear-wave velocities in Connecticut was initiated in support of broader seismic hazard mapping efforts undertaken by New England State Geologists. Thirty field sites in Hartford County representative of the range of mapped seismic hazard classes were chosen based on the availability of boring logs and adequate open space for the geophysical surveys. Because it can be difficult to acquire multi-channel seismic data in urban areas due to unwanted noise and open space restrictions, we also investigated the use of passive single-station seismometer measurements as a compact supplement and potential alternative to long-offset multi-channel measurements. Here we compare the results of active-source multi-channel analysis of surface waves (MASW) and passive horizontal-to-vertical spectral ratio (HVSR) seismic methods to determine shear-wave velocity profiles and seismic hazard classification based on Vs30 in glacial sediments throughout Hartford County, Connecticut. HVSR-derived seismic resonances were used as a constraint during inversion of the MASW dispersion curve to reduce model misfit and improve model comparison to site lithology.

  8. Seismic Inversion Methods

    SciTech Connect

    Jackiewicz, Jason

    2009-09-16

    With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology.

  9. Method of migrating seismic records

    DOEpatents

    Ober, Curtis C.; Romero, Louis A.; Ghiglia, Dennis C.

    2000-01-01

    The present invention provides a method of migrating seismic records that retains the information in the seismic records and allows migration with significant reductions in computing cost. The present invention comprises phase encoding seismic records and combining the encoded seismic records before migration. Phase encoding can minimize the effect of unwanted cross terms while still allowing significant reductions in the cost to migrate a number of seismic records.

  10. Active Seismic Imaging Experiment

    NASA Astrophysics Data System (ADS)

    Berge, Patricia A.; Dawson, Phillip B.; Evans, John R.

    In September 1985 the U.S. Geological Survey (USGS) and Lawrence Livermore National Laboratory (LLNL) will conduct an active seismic experiment in the Medicine Lake area of northern California. The work is supported by the Geothermal Research Program of USGS and by the Geothermal and Hydropower Technologies Division of the U.S. Department of Energy. We invite interested organizations or individuals to record our explosions from Medicine Lake volcano and surrounding areas not covered by the USGS-LLNL array.

  11. Active and passive seismic methods for characterization and monitoring of unstable rock masses: field surveys, laboratory tests and modeling.

    NASA Astrophysics Data System (ADS)

    Colombero, Chiara; Baillet, Laurent; Comina, Cesare; Jongmans, Denis; Vinciguerra, Sergio

    2016-04-01

    Appropriate characterization and monitoring of potentially unstable rock masses may provide a better knowledge of the active processes and help to forecast the evolution to failure. Among the available geophysical methods, active seismic surveys are often suitable to infer the internal structure and the fracturing conditions of the unstable body. For monitoring purposes, although remote-sensing techniques and in-situ geotechnical measurements are successfully tested on landslides, they may not be suitable to early forecast sudden rapid rockslides. Passive seismic monitoring can help for this purpose. Detection, classification and localization of microseismic events within the prone-to-fall rock mass can provide information about the incipient failure of internal rock bridges. Acceleration to failure can be detected from an increasing microseismic event rate. The latter can be compared with meteorological data to understand the external factors controlling stability. On the other hand, seismic noise recorded on prone-to-fall rock slopes shows that the temporal variations in spectral content and correlation of ambient vibrations can be related to both reversible and irreversible changes within the rock mass. We present the results of the active and passive seismic data acquired at the potentially unstable granitic cliff of Madonna del Sasso (NW Italy). Down-hole tests, surface refraction and cross-hole tomography were carried out for the characterization of the fracturing state of the site. Field surveys were implemented with laboratory determination of physico-mechanical properties on rock samples and measurements of the ultrasonic pulse velocity. This multi-scale approach led to a lithological interpretation of the seismic velocity field obtained at the site and to a systematic correlation of the measured velocities with physical properties (density and porosity) and macroscopic features of the granitic cliff (fracturing, weathering and anisotropy). Continuous

  12. An analytical method about anomalies on the synthetical variables of the multiple seismic activity parameters-taking 2 M =7 earthquakes occurring in Qinghai as examples

    NASA Astrophysics Data System (ADS)

    Ma, Heqing; Yang, Mingzhi

    2014-05-01

    Based on the random field theory, a new method of the synthetical variables of the multiple seismic activity parameters has been proposed. This method is that the natural perpendicular function development has been used on the random field function of seismic activity first. And then the synthetical variables constituted of the linear combination of four seismic activity parameters, i.e. the seismic strain release E-, the average distance between each two earthquakes D, the average time interval between each two earthquakes T , and the earthquake occurrence rate N have been studied. Though the analysis on the synthetical variables about the field, the seismic activity anomalies before large earthquakes have been drew. As the examples, the Gonghe M=7.0 earthquake occurred in Qinghai, 1990 and the Yushu M=7.1 earthquake occurred in Qinghai, 2010 have been discussed. The results have showed that before the two M=7 earthquakes, the main synthetical variables have all showed obvious abnormal variations, displaying better corresponding relationship with these two earthquakes. The synthetical variables of seismic activity field can focus on the slight differences which are included in each original variable. And the abnormal variations showed from the synthetical variables are as obvious as possible. The authors think that the synthetical variable method is possibly an effective analytic technique. Key words: seismic activity field; natural perpendicular function development; synthetical variables; anomaly; Earthquake example

  13. An objective method for the assessment of fluid injection-induced seismicity and application to tectonically active regions in central California

    NASA Astrophysics Data System (ADS)

    Goebel, T. H. W.; Hauksson, E.; Aminzadeh, F.; Ampuero, J.-P.

    2015-10-01

    Changes in seismicity rates, whether of tectonic or of induced origin, can readily be identified in regions where background rates are low but are difficult to detect in seismically active regions. We present a novel method to identify likely induced seismicity in tectonically active regions based on short-range spatiotemporal correlations between changes in fluid injection and seismicity rates. The method searches through the entire parameter space of injection rate thresholds and determines the statistical significance of correlated changes in injection and seismicity rates. Applying our method to Kern County, central California, we find that most earthquakes within the region are tectonic; however, fluid injection contributes to seismicity in four different cases. Three of these are connected to earthquake sequences with events above M4. Each of these sequences followed an abrupt increase in monthly injection rates of at least 15,000 m3. The probability that the seismicity sequences and the abrupt changes in injection rates in Kern County coincide by chance is only 4%. The identified earthquake sequences display low Gutenberg-Richter b values of ˜0.6-0.7 and at times systematic migration patterns characteristic for a diffusive process. Our results show that injection-induced pressure perturbations can influence seismic activity at distances of 10 km or more. Triggering of earthquakes at these large distances may be facilitated by complex local geology and faults in tectonically active regions. Our study provides the first comprehensive, statistically robust assessment of likely injection-induced seismicity within a large, tectonically active region.

  14. Methods for seismic exploration

    SciTech Connect

    Savit, C. H.

    1985-10-01

    Sweeps of seismic signals consisting of pulse trains having a predetermined number of pulses in which the periods or durations of the pulses are randomized and in which the wave shape and relative time displacements of the pulses in different trains provides substantially constant spectral level over a frequency range containing several octaves even though the durations of the pulses correspond to a frequency range not exceeding an octave during the sweep are transmitted through the medium being explored such as an earth formation to receptors such as geophones or hydrophones. Groups of signals contained in less than the entire length of the sweep which are transmitted and which are received can be cross correlated to vary the effective duration of the sweep. The cross correlation output of successively occurring sweeps may be stacked to reduce the side lobe amplitude of the cross correlation outputs from each sweep, from which outputs seismograms may be constructed.

  15. New Method of active electromagnetic induction and seismic Monitoring in Oil saturated Media

    NASA Astrophysics Data System (ADS)

    Hachay, Olga, ,, Prof.; Khachay, Oleg; Khachay, Andrey

    2014-05-01

    It is provided a comparison of no equilibrium effects by independent hydro dynamical and electromagnetic induction influence on an oil layer and the medium, which it surrounds. It is known, that by drainage and steeps the hysteresis effect on curves of the relative phase permeability in dependence from porous medium water saturation by some cycles of influence: drainage-steep-drainage is observed. In earlier papers the analysis of the seism acoustic monitoring data in regimes of phone radiation, response on the first influence of given frequency and on the second influence is developed. For the analysis of seism acoustic response in time on fixed intervals along the borehole an algorithm of phase diagrams of the state of many phase medium is suggested. On the base of developed algorithm a new algorithm of analyze of space, but integral in time for equal observation periods changing by the method of phase diagram state of many phase medium in the oil layer is developed. The developed method allows on quality level to classify the state of the polyphase medium, which is the oil layer, using data of many cycles influence. In that paper we suggest the algorithm of modeling of 2-d seismic field distribution in the heterogeneous medium with hierarchic inclusions. Using the developed earlier 3-d method of induction electromagnetic frequency geometric monitoring we showed the opportunity of defining of physical and structural features of hierarchic oil layer structure and estimating of water saturating by crack inclusions. That allows managing the process of drainage and steeping by water displacement the oil out of the layer. Thus, the developed methods allow on the quality and quantity levels to make a classification of the many phase medium, which is an oil layer, using data for multiple excitation. For quantitative solution of earlier listed events of no equilibrium and hysteretic interaction of water and oil by out working of the oil layer, it is urgently to add and

  16. Permafrost Active Layer Seismic Interferometry Experiment (PALSIE).

    SciTech Connect

    Abbott, Robert; Knox, Hunter Anne; James, Stephanie; Lee, Rebekah; Cole, Chris

    2016-01-01

    We present findings from a novel field experiment conducted at Poker Flat Research Range in Fairbanks, Alaska that was designed to monitor changes in active layer thickness in real time. Results are derived primarily from seismic data streaming from seven Nanometric Trillium Posthole seismometers directly buried in the upper section of the permafrost. The data were evaluated using two analysis methods: Horizontal to Vertical Spectral Ratio (HVSR) and ambient noise seismic interferometry. Results from the HVSR conclusively illustrated the method's effectiveness at determining the active layer's thickness with a single station. Investigations with the multi-station method (ambient noise seismic interferometry) are continuing at the University of Florida and have not yet conclusively determined active layer thickness changes. Further work continues with the Bureau of Land Management (BLM) to determine if the ground based measurements can constrain satellite imagery, which provide measurements on a much larger spatial scale.

  17. Seismic Holography of Solar Activity

    NASA Technical Reports Server (NTRS)

    Lindsey, Charles

    2000-01-01

    The basic goal of the project was to extend holographic seismic imaging techniques developed under a previous NASA contract, and to incorporate phase diagnostics. Phase-sensitive imaging gives us a powerful probe of local thermal and Doppler perturbations in active region subphotospheres, allowing us to map thermal structure and flows associated with "acoustic moats" and "acoustic glories". These remarkable features were discovered during our work, by applying simple acoustic power holography to active regions. Included in the original project statement was an effort to obtain the first seismic images of active regions on the Sun's far surface.

  18. DISPLACEMENT BASED SEISMIC DESIGN METHODS.

    SciTech Connect

    HOFMAYER,C.MILLER,C.WANG,Y.COSTELLO,J.

    2003-07-15

    A research effort was undertaken to determine the need for any changes to USNRC's seismic regulatory practice to reflect the move, in the earthquake engineering community, toward using expected displacement rather than force (or stress) as the basis for assessing design adequacy. The research explored the extent to which displacement based seismic design methods, such as given in FEMA 273, could be useful for reviewing nuclear power stations. Two structures common to nuclear power plants were chosen to compare the results of the analysis models used. The first structure is a four-story frame structure with shear walls providing the primary lateral load system, referred herein as the shear wall model. The second structure is the turbine building of the Diablo Canyon nuclear power plant. The models were analyzed using both displacement based (pushover) analysis and nonlinear dynamic analysis. In addition, for the shear wall model an elastic analysis with ductility factors applied was also performed. The objectives of the work were to compare the results between the analyses, and to develop insights regarding the work that would be needed before the displacement based analysis methodology could be considered applicable to facilities licensed by the NRC. A summary of the research results, which were published in NUREGICR-6719 in July 2001, is presented in this paper.

  19. LANL seismic screening method for existing buildings

    SciTech Connect

    Dickson, S.L.; Feller, K.C.; Fritz de la Orta, G.O.

    1997-01-01

    The purpose of the Los Alamos National Laboratory (LANL) Seismic Screening Method is to provide a comprehensive, rational, and inexpensive method for evaluating the relative seismic integrity of a large building inventory using substantial life-safety as the minimum goal. The substantial life-safety goal is deemed to be satisfied if the extent of structural damage or nonstructural component damage does not pose a significant risk to human life. The screening is limited to Performance Category (PC) -0, -1, and -2 buildings and structures. Because of their higher performance objectives, PC-3 and PC-4 buildings automatically fail the LANL Seismic Screening Method and will be subject to a more detailed seismic analysis. The Laboratory has also designated that PC-0, PC-1, and PC-2 unreinforced masonry bearing wall and masonry infill shear wall buildings fail the LANL Seismic Screening Method because of their historically poor seismic performance or complex behavior. These building types are also recommended for a more detailed seismic analysis. The results of the LANL Seismic Screening Method are expressed in terms of separate scores for potential configuration or physical hazards (Phase One) and calculated capacity/demand ratios (Phase Two). This two-phase method allows the user to quickly identify buildings that have adequate seismic characteristics and structural capacity and screen them out from further evaluation. The resulting scores also provide a ranking of those buildings found to be inadequate. Thus, buildings not passing the screening can be rationally prioritized for further evaluation. For the purpose of complying with Executive Order 12941, the buildings failing the LANL Seismic Screening Method are deemed to have seismic deficiencies, and cost estimates for mitigation must be prepared. Mitigation techniques and cost-estimate guidelines are not included in the LANL Seismic Screening Method.

  20. Assessment of seismic margin calculation methods

    SciTech Connect

    Kennedy, R.P.; Murray, R.C.; Ravindra, M.K.; Reed, J.W.; Stevenson, J.D.

    1989-03-01

    Seismic margin review of nuclear power plants requires that the High Confidence of Low Probability of Failure (HCLPF) capacity be calculated for certain components. The candidate methods for calculating the HCLPF capacity as recommended by the Expert Panel on Quantification of Seismic Margins are the Conservative Deterministic Failure Margin (CDFM) method and the Fragility Analysis (FA) method. The present study evaluated these two methods using some representative components in order to provide further guidance in conducting seismic margin reviews. It is concluded that either of the two methods could be used for calculating HCLPF capacities. 21 refs., 9 figs., 6 tabs.

  1. Alternative Energy Sources in Seismic Methods

    NASA Astrophysics Data System (ADS)

    Tün, Muammer; Pekkan, Emrah; Mutlu, Sunay; Ecevitoğlu, Berkan

    2015-04-01

    When the suitability of a settlement area is investigated, soil-amplification, liquefaction and fault-related hazards should be defined, and the associated risks should be clarified. For this reason, soil engineering parameters and subsurface geological structure of a new settlement area should be investigated. Especially, faults covered with quaternary alluvium; thicknesses, shear-wave velocities and geometry of subsurface sediments could lead to a soil amplification during an earthquake. Likewise, changes in shear-wave velocities along the basin are also very important. Geophysical methods can be used to determine the local soil properties. In this study, use of alternative seismic energy sources when implementing seismic reflection, seismic refraction and MASW methods in the residential areas of Eskisehir/Turkey, were discussed. Our home developed seismic energy source, EAPSG (Electrically-Fired-PS-Gun), capable to shoot 2x24 magnum shotgun cartridges at once to generate P and S waves; and our home developed WD-500 (500 kg Weight Drop) seismic energy source, mounted on a truck, were developed under a scientific research project of Anadolu University. We were able to reach up to penetration depths of 1200 m for EAPSG, and 800 m for WD-500 in our seismic reflection surveys. WD-500 seismic energy source was also used to perform MASW surveys, using 24-channel, 10 m apart, 4.5 Hz vertical geophone configuration. We were able to reach 100 m of penetration depth in MASW surveys.

  2. Geyser's Eruptive Activity in Broadband Seismic Records

    NASA Astrophysics Data System (ADS)

    Kugaenko, Yulia; Saltykov, Vadim

    2010-05-01

    A geyser is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapor phase (steam). The formation of geysers is due to particular hydrogeological conditions, which exist in only a few places on Earth, so they are a fairly rare phenomenon. The reasons of geyser periodicity and specifics of the activity for every particular geyser are not completely clear yet. So almost for all known geysers it is necessary to develop the personal model. In given study we first use seismic method for detection of possible hidden feature of geyser's eruptive activity in Kamchatkan Valley of the Geysers. Broadband seismic records of geyser generated signals were obtained in hydrothermal field. The Valley of the Geysers belongs to Kronotskiy State Natural Biosphere Reserve and the UNESCO World Natural Heritage Site "Volcanoes of Kamchatka". Neither seismological nor geophysical investigations were carried out here earlier. In September, 2009 seismic observation was organized in geyser's field by 24-bit digital output broadband seismometers (GURALP CMG-6TD flat velocity response 0.033-50 Hz). Four geysers were surveyed: the fountain type Big and Giant geysers; the cone type Pearl geyser and the short-period Gap geyser. Seismometers were set as possible close to the geyser's surface vent (usually at the distance near 3-5 m). Main parameters of the eruptions for the investigated geysers: - The Giant geyser is the most powerful among the regular active geysers in Kamchatkan Valley of the Geysers. The height of the fountain reaches 30 meters, the mass of water erupted is about 40-60 tons. The main cycle of activity varies significantly: in 1945 the intervals between eruptions was near 3 hours, nowadays it is 5-6 hours. As a geyser of fountain type, the Giant geyser erupts from the 2*3 m2 pool of water. - The Big geyser was flooded by the lake after the natural catastrophe (giant mud-stone avalanche, formed by landslide, bed into Geiyzernaya

  3. 3D modelling of the active normal fault network in the Apulian Ridge (Eastern Mediterranean Sea): Integration of seismic and bathymetric data with implicit surface methods

    NASA Astrophysics Data System (ADS)

    Bistacchi, Andrea; Pellegrini, Caludio; Savini, Alessandra; Marchese, Fabio

    2016-04-01

    The Apulian ridge (North-eastern Ionian Sea, Mediterranean), interposed between the facing Apennines and Hellenides subduction zones (to the west and east respectively), is characterized by thick cretaceous carbonatic sequences and discontinuous tertiary deposits crosscut by a penetrative network of NNW-SSE normal faults. These are exposed onshore in Puglia, and are well represented offshore in a dataset composed of 2D seismics and wells collected by oil companies from the '60s to the '80s, more recent seismics collected during research projects in the '90s, recent very high resolution seismics (VHRS - Sparker and Chirp-sonar data), multibeam echosounder bathymetry, and sedimentological and geo-chronological analyses of sediment samples collected on the seabed. Faults are evident in 2D seismics at all scales, and their along-strike geometry and continuity can be characterized with multibeam bathymetric data, which show continuous fault scarps on the seabed (only partly reworked by currents and covered by landslides). Fault scarps also reveal the finite displacement accumulated in the Holocene-Pleistocene. We reconstructed a 3D model of the fault network and suitable geological boundaries (mainly unconformities due to the discontinuous distribution of quaternary and tertiary sediments) with implicit surface methods implemented in SKUA/GOCAD. This approach can be considered very effective and allowed reconstructing in details complex structures, like the frequent relay zones that are particularly well imaged by seafloor geomorphology. Mutual cross-cutting relationships have been recognized between fault scarps and submarine mass-wasting deposits (Holocene-Pleistocene), indicating that, at least in places, these features are coeval, hence the fault network should be considered active. At the regional scale, the 3D model allowed measuring the horizontal WSW-ENE stretching, which can be associated to the bending moment applied to the Apulian Plate by the combined effect

  4. Near-Surface Site Characterization Using a Combination of Active and Passive Seismic Arrays

    NASA Astrophysics Data System (ADS)

    Lane, J. W.; Liu, L.; Chen, Y.; White, E. A.

    2007-12-01

    Seismic surveys with an active source are commonly used to characterize the subsurface. Increasingly, passive seismic surveys utilizing ambient seismic frequencies (microtremors) are being used to support geotechnical and hazards engineering studies. In this study, we use a combination of active and passive seismic methods to characterize a watershed site at Haddam Meadows State Park, Haddam, Connecticut. At Haddam Meadows, we employed a number of seismic arrays using both active and passive approaches to estimate the depth to rock and the seismic velocity structure of the unconsolidated sediments. The active seismic surveys included seismic refraction and multi-channel analysis of surface waves (MASW) using an accelerated weight-drop seismic source. The passive seismic surveys consisted of MASW techniques using both linear and circular geophone arrays, and a survey using a 3-component seismometer. The active seismic data were processed using conventional algorithms; the passive seismic data were processed using both the spatial autocorrelation method (SPAC) and the horizontal to vertical spectral ratio (H/V) method. The interpretations of subsurface structure from the active and passive surveys are generally in good agreement and compare favorably with ground truth information provided by adjacent boreholes. Our results suggest that a combination of active and passive seismic methods can be used to rapidly characterize the subsurface at the watershed scale.

  5. Applying the seismic interferometry method to vertical seismic profile data using tunnel excavation noise as source

    NASA Astrophysics Data System (ADS)

    Jurado, Maria Jose; Teixido, Teresa; Martin, Elena; Segarra, Miguel; Segura, Carlos

    2013-04-01

    In the frame of the research conducted to develop efficient strategies for investigation of rock properties and fluids ahead of tunnel excavations the seismic interferometry method was applied to analyze the data acquired in boreholes instrumented with geophone strings. The results obtained confirmed that seismic interferometry provided an improved resolution of petrophysical properties to identify heterogeneities and geological structures ahead of the excavation. These features are beyond the resolution of other conventional geophysical methods but can be the cause severe problems in the excavation of tunnels. Geophone strings were used to record different types of seismic noise generated at the tunnel head during excavation with a tunnelling machine and also during the placement of the rings covering the tunnel excavation. In this study we show how tunnel construction activities have been characterized as source of seismic signal and used in our research as the seismic source signal for generating a 3D reflection seismic survey. The data was recorded in vertical water filled borehole with a borehole seismic string at a distance of 60 m from the tunnel trace. A reference pilot signal was obtained from seismograms acquired close the tunnel face excavation in order to obtain best signal-to-noise ratio to be used in the interferometry processing (Poletto et al., 2010). The seismic interferometry method (Claerbout 1968) was successfully applied to image the subsurface geological structure using the seismic wave field generated by tunneling (tunnelling machine and construction activities) recorded with geophone strings. This technique was applied simulating virtual shot records related to the number of receivers in the borehole with the seismic transmitted events, and processing the data as a reflection seismic survey. The pseudo reflective wave field was obtained by cross-correlation of the transmitted wave data. We applied the relationship between the transmission

  6. Patterns of seismic activity preceding large earthquakes

    NASA Technical Reports Server (NTRS)

    Shaw, Bruce E.; Carlson, J. M.; Langer, J. S.

    1992-01-01

    A mechanical model of seismic faults is employed to investigate the seismic activities that occur prior to major events. The block-and-spring model dynamically generates a statistical distribution of smaller slipping events that precede large events, and the results satisfy the Gutenberg-Richter law. The scaling behavior during a loading cycle suggests small but systematic variations in space and time with maximum activity acceleration near the future epicenter. Activity patterns inferred from data on seismicity in California demonstrate a regional aspect; increased activity in certain areas are found to precede major earthquake events. One example is given regarding the Loma Prieta earthquake of 1989 which is located near a fault section associated with increased activity levels.

  7. Seismic hazard assessment of Syria using seismicity, DEM, slope, active tectonic and GIS

    NASA Astrophysics Data System (ADS)

    Ahmad, Raed; Adris, Ahmad; Singh, Ramesh

    2016-07-01

    In the present work, we discuss the use of an integrated remote sensing and Geographical Information System (GIS) techniques for evaluation of seismic hazard areas in Syria. The present study is the first time effort to create seismic hazard map with the help of GIS. In the proposed approach, we have used Aster satellite data, digital elevation data (30 m resolution), earthquake data, and active tectonic maps. Many important factors for evaluation of seismic hazard were identified and corresponding thematic data layers (past earthquake epicenters, active faults, digital elevation model, and slope) were generated. A numerical rating scheme has been developed for spatial data analysis using GIS to identify ranking of parameters to be included in the evaluation of seismic hazard. The resulting earthquake potential map delineates the area into different relative susceptibility classes: high, moderate, low and very low. The potential earthquake map was validated by correlating the obtained different classes with the local probability that produced using conventional analysis of observed earthquakes. Using earthquake data of Syria and the peak ground acceleration (PGA) data is introduced to the model to develop final seismic hazard map based on Gutenberg-Richter (a and b values) parameters and using the concepts of local probability and recurrence time. The application of the proposed technique in Syrian region indicates that this method provides good estimate of seismic hazard map compared to those developed from traditional techniques (Deterministic (DSHA) and probabilistic seismic hazard (PSHA). For the first time we have used numerous parameters using remote sensing and GIS in preparation of seismic hazard map which is found to be very realistic.

  8. Active Seismic Monitoring for Earthquake Forecasting

    NASA Astrophysics Data System (ADS)

    Artamonova, M.; Korneev, V.

    2005-12-01

    Earthquake prediction remains high priority issue for disaster prevention. Study of the M6.0 2004 Parkfield and M7.0 1989 Loma Prieta strike-slip earthquakes on the San Andreas Fault (SAF) reveal seismicity peaks in the surrounding crust several months prior to the main events. Earthquakes directly within the SAF zone were intentionally excluded from the analysis because they manifest stress-release processes rather than stress accumulation. The observed increase in seismicity is interpreted as a signature of the increasing stress level in the surrounding crust, while the peak that occurs several months prior to the main event and the subsequent decrease in seismicity are attributed to damage-induced softening processes. Furthermore, in both cases there is a distinctive zone of low seismic activity that surrounds the epicentral region in the pre-event period. The increase of seismicity in the crust surrounding a potential future event and the development of a low-seismicity epicentral zone can be regarded as promising precursory information that could help signal the arrival of large earthquakes. We modeled the seismicity precursor phenomena using finite-element 2D model capable to replicate non-linear breaking of elastic rock. The distinctive seismicity peak was observed for a model simulating SAF properties at Park field. Such peaks are likely to be a good mid-term precursors allowing to declare alerts several months before earthquakes and pointing on their epicenter regions. The short tern alerts require use of active sources and their proper placement in order to monitor the developments of rock softening processes.

  9. Multiharmonic model of seismic activity in Kamchatka

    NASA Astrophysics Data System (ADS)

    Sobolev, G. A.; Valeev, S. G.; Faskhutdinova, V. A.

    2010-12-01

    Based on the uniform catalogue of earthquakes of the minimum energy class 8.5 for 1962-2008, multiharmonic models of seismic activity in Kamchatka are developed. The main harmonic components with periods from a few days to 12 years are identified. Both the entire catalogue and its modified versions obtained by the elimination of aftershocks and clusters, as well as nonoverlapping time series were used to study the stability of the models. The forward-prediction testing showed that in the models with weekly averaged initial data, periods of increased and reduced seismic activity lasting for several weeks are predicted with high confidence on an interval of up to 1.8% of the education period. This testifies for the presence of deterministic components in the seismic activity.

  10. Apollo 14 active seismic experiment.

    PubMed

    Watkins, J S; Kovach, R L

    1972-03-17

    Explosion seismic refraction data indicate that the lunar near-surface rocks at the Apollo 14 site consist of a regolith 8.5 meters thick and characterized by a compressional wave velocity of 104 meters per second. The regolith is underlain by a layer with a compressional wave velocity of 299 meters per second. The thickness of this layer, which we interpret to be the Fra Mauro Formation, is between 16 and 76 meters. The layer immediately beneath this has a velocity greater than 370 meters per second. We found no evidence of permafrost. PMID:17794200

  11. Apollo 14 active seismic experiment.

    NASA Technical Reports Server (NTRS)

    Watkins, J. S.; Kovach, R. L.

    1972-01-01

    Explosion seismic refraction data indicate that the lunar near-surface rocks at the Apollo 14 site consist of a regolith 8.5 meters thick and characterized by a compressional wave velocity of 104 meters per second. The regolith is underlain by a layer with a compressional wave velocity of 299 meters per second. The thickness of this layer, which we interpret to be the Fra Mauro Formation, is between 16 and 76 meters. The layer immediately beneath this has a velocity greater than 370 meters per second. We found no evidence of permafrost.

  12. Regional Observation of Seismic Activity in Baekdu Mountain

    NASA Astrophysics Data System (ADS)

    Kim, Geunyoung; Che, Il-Young; Shin, Jin-Soo; Chi, Heon-Cheol

    2015-04-01

    Seismic unrest in Baekdu Mountain area between North Korea and Northeast China region has called attention to geological research community in Northeast Asia due to her historical and cultural importance. Seismic bulletin shows level of seismic activity in the area is higher than that of Jilin Province of Northeast China. Local volcanic observation shows a symptom of magmatic unrest in period between 2002 and 2006. Regional seismic data have been used to analyze seismic activity of the area. The seismic activity could be differentiated from other seismic phenomena in the region by the analysis.

  13. Geyser's Eruptive Activity in Broadband Seismic Records

    NASA Astrophysics Data System (ADS)

    Kugaenko, Yulia; Saltykov, Vadim

    2010-05-01

    A geyser is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapor phase (steam). The formation of geysers is due to particular hydrogeological conditions, which exist in only a few places on Earth, so they are a fairly rare phenomenon. The reasons of geyser periodicity and specifics of the activity for every particular geyser are not completely clear yet. So almost for all known geysers it is necessary to develop the personal model. In given study we first use seismic method for detection of possible hidden feature of geyser's eruptive activity in Kamchatkan Valley of the Geysers. Broadband seismic records of geyser generated signals were obtained in hydrothermal field. The Valley of the Geysers belongs to Kronotskiy State Natural Biosphere Reserve and the UNESCO World Natural Heritage Site "Volcanoes of Kamchatka". Neither seismological nor geophysical investigations were carried out here earlier. In September, 2009 seismic observation was organized in geyser's field by 24-bit digital output broadband seismometers (GURALP CMG-6TD flat velocity response 0.033-50 Hz). Four geysers were surveyed: the fountain type Big and Giant geysers; the cone type Pearl geyser and the short-period Gap geyser. Seismometers were set as possible close to the geyser's surface vent (usually at the distance near 3-5 m). Main parameters of the eruptions for the investigated geysers: - The Giant geyser is the most powerful among the regular active geysers in Kamchatkan Valley of the Geysers. The height of the fountain reaches 30 meters, the mass of water erupted is about 40-60 tons. The main cycle of activity varies significantly: in 1945 the intervals between eruptions was near 3 hours, nowadays it is 5-6 hours. As a geyser of fountain type, the Giant geyser erupts from the 2*3 m2 pool of water. - The Big geyser was flooded by the lake after the natural catastrophe (giant mud-stone avalanche, formed by landslide, bed into Geiyzernaya

  14. Observations of seismic activity in Southern Lebanon

    NASA Astrophysics Data System (ADS)

    Meirova, T.; Hofstetter, R.

    2013-04-01

    Recent seismic activity in southern Lebanon is of particular interest since the tectonic framework of this region is poorly understood. In addition, seismicity in this region is very infrequent compared with the Roum fault to the east, which is seismically active. Between early 2008 and the end of 2010, intense seismic activity occurred in the area. This was manifested by several swarm-like sequences and continuous trickling seismicity over many days, amounting in total to more than 900 earthquakes in the magnitude range of 0.5 ≤ M d ≤ 5.2. The region of activity extended in a 40-km long zone mainly in a N-S direction and was located about 10 km west of the Roum fault. The largest earthquake, with a duration magnitude of M d = 5.2, occurred on February 15, 2008, and was located at 33.327° N, 35.406° E at a depth of 3 km. The mean-horizontal peak ground acceleration observed at two nearby accelerometers exceeded 0.05 g, where the strongest peak horizontal acceleration was 55 cm/s2 at about 20 km SE of the epicenter. Application of the HypoDD algorithm yielded a pronounced N-S zone, parallel to the Roum fault, which was not known to be seismically active. Focal mechanism, based on full waveform inversion and the directivity effect of the strongest earthquake, suggests left-lateral strike-slip NNW-SSE faulting that crosses the NE-SW traverse faults in southern Lebanon.

  15. 3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

    NASA Astrophysics Data System (ADS)

    Frantzeskakis, Theofanis; Konstantaras, Anthony

    2015-04-01

    During the last few years rapid steps have been taken towards drilling for oil in the western Mediterranean sea. Since most of the countries in the region benefit mainly from tourism and considering that the Mediterranean is a closed sea only replenishing its water once every ninety years careful measures are being taken to ensure safe drilling. In that concept this research work attempts to derive a three dimensional model of the seismically active parts of the underlying underground faults in areas of petroleum interest. For that purpose seismic spatio-temporal clustering has been applied to seismic data to identify potential distinct seismic regions in the area of interest. Results have been coalesced with two dimensional maps of underground faults from past surveys and seismic epicentres, having followed careful reallocation processing, have been used to provide information regarding the vertical extent of multiple underground faults in the region of interest. The end product is a three dimensional map of the possible underground location and extent of the seismically active parts of underground faults. Indexing terms: underground faults modelling, seismic data mining, 3D visualisation, active seismic source mapping, seismic hazard evaluation, dangerous phenomena modelling Acknowledgment This research work is supported by the ESPA Operational Programme, Education and Life Long Learning, Students Practical Placement Initiative. References [1] Alves, T.M., Kokinou, E. and Zodiatis, G.: 'A three-step model to assess shoreline and offshore susceptibility to oil spills: The South Aegean (Crete) as an analogue for confined marine basins', Marine Pollution Bulletin, In Press, 2014 [2] Ciappa, A., Costabile, S.: 'Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)', Marine Pollution Bulletin, vol. 84 (1-2), pp. 44-55, 2014 [3] Ganas, A., Karastathis, V., Moshou, A., Valkaniotis, S., Mouzakiotis

  16. Extracting physical parameters from marine seismic data: New methods in seismic oceanography and velocity inversion

    NASA Astrophysics Data System (ADS)

    Fortin, Will F. J.

    The utility and meaning of a geophysical dataset is dependent on good interpretation informed by high-quality data, processing, and attribute examination via technical methodologies. Active source marine seismic reflection data contains a great deal of information in the location, phase, and amplitude of both pre- and post-stack seismic reflections. Using pre- and post-stack data, this work has extracted useful information from marine reflection seismic data in novel ways in both the oceanic water column and the sub-seafloor geology. In chapter 1 we develop a new method for estimating oceanic turbulence from a seismic image. This method is tested on synthetic seismic data to show the method's ability to accurately recover both distribution and levels of turbulent diffusivity. Then we apply the method to real data offshore Costa Rica where we observe lee waves. Our results find elevated diffusivities near the seafloor as well as above the lee waves five times greater than surrounding waters and 50 times greater than open ocean diffusivities. Chapter 2 investigates subsurface geology in the Cascadia Subduction Zone and outlines a workflow for using pre-stack waveform inversion to produce highly detailed velocity models and seismic images. Using a newly developed inversion code, we achieve better imaging results as compared to the product of a standard, user-intensive method for building a velocity model. Our results image the subduction interface ~30 km farther landward than previous work and better images faults and sedimentary structures above the oceanic plate as well as in the accretionary prism. The resultant velocity model is highly detailed, inverted every 6.25 m with ~20 m vertical resolution, and will be used to examine the role of fluids in the subduction system. These results help us to better understand the natural hazards risks associated with the Cascadia Subduction Zone. Chapter 3 returns to seismic oceanography and examines the dynamics of nonlinear

  17. Lunar seismic profiling experiment natural activity study

    NASA Technical Reports Server (NTRS)

    Duennebier, F. K.

    1976-01-01

    The Lunar Seismic Experiment Natural Activity Study has provided a unique opportunity to study the high frequency (4-20 Hz) portion to the seismic spectrum on the moon. The data obtained from the LSPE was studied to evaluate the origin and importance of the process that generates thermal moonquakes and the characteristics of the seismic scattering zone at the lunar surface. The detection of thermal moonquakes by the LSPE array made it possible to locate the sources of many events and determine that they are definitely not generated by astronaut activities but are the result of a natural process on the moon. The propagation of seismic waves in the near-surface layers was studied in a qualitative manner. In the absence of an adequate theoretical model for the propagation of seismic waves in the moon, it is not possible to assign a depth for the scattering layer. The LSPE data does define several parameters which must be satisfied by any model developed in the future.

  18. Subband Coding Methods for Seismic Data Compression

    NASA Technical Reports Server (NTRS)

    Kiely, A.; Pollara, F.

    1995-01-01

    This paper presents a study of seismic data compression techniques and a compression algorithm based on subband coding. The compression technique described could be used as a progressive transmission system, where successive refinements of the data can be requested by the user. This allows seismologists to first examine a coarse version of waveforms with minimal usage of the channel and then decide where refinements are required. Rate-distortion performance results are presented and comparisons are made with two block transform methods.

  19. Supervised Classification Methods for Seismic Phase Identification

    NASA Astrophysics Data System (ADS)

    Schneider, Jeff; Given, Jeff; Le Bras, Ronan; Fisseha, Misrak

    2010-05-01

    The Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) is tasked with monitoring compliance with the CTBT. The organization is installing the International Monitoring System (IMS), a global network of seismic, hydroacoustic, infrasound, and radionuclide sensor stations. The International Data Centre (IDC) receives the data from seismic stations either in real time or on request. These data are first processed on a station per station basis. This initial step yields discrete detections which are then assembled on a network basis (with the addition of hydroacoustic and infrasound data) to produce automatic and analyst reviewed bulletins containing seismic, hydroacoustic, and infrasound detections. The initial station processing step includes the identification of seismic and acoustic phases which are given a label. Subsequent network processing relies on this preliminary labeling, and as a consequence, the accuracy and reliability of automatic and reviewed bulletins also depend on this initial step. A very large ground truth database containing massive amounts of detections with analyst-reviewed labels is available to improve on the current operational system using machine learning methods. An initial study using a limited amount of data was conducted during the ISS09 project of the CTBTO. Several classification methods were tested: decision tree with bagging; logistic regression; neural networks trained with back-propagation; Bayesian networks as generative class models; naive Bayse classification; support vector machines. The initial assessment was that the phase identification process could be improved by at least 13% over the current operational system and that the method obtaining the best results was the decision tree with bagging. We present the results of a study using a much larger learning dataset and preliminary implementation results.

  20. Detecting seismic activity with a covariance matrix analysis of data recorded on seismic arrays

    NASA Astrophysics Data System (ADS)

    Seydoux, L.; Shapiro, N. M.; de Rosny, J.; Brenguier, F.; Landès, M.

    2016-03-01

    Modern seismic networks are recording the ground motion continuously at the Earth's surface, providing dense spatial samples of the seismic wavefield. The aim of our study is to analyse these records with statistical array-based approaches to identify coherent time-series as a function of time and frequency. Using ideas mainly brought from the random matrix theory, we analyse the spatial coherence of the seismic wavefield from the width of the covariance matrix eigenvalue distribution. We propose a robust detection method that could be used for the analysis of weak and emergent signals embedded in background noise, such as the volcanic or tectonic tremors and local microseismicity, without any prior knowledge about the studied wavefields. We apply our algorithm to the records of the seismic monitoring network of the Piton de la Fournaise volcano located at La Réunion Island and composed of 21 receivers with an aperture of ˜15 km. This array recorded many teleseismic earthquakes as well as seismovolcanic events during the year 2010. We show that the analysis of the wavefield at frequencies smaller than ˜0.1 Hz results in detection of the majority of teleseismic events from the Global Centroid Moment Tensor database. The seismic activity related to the Piton de la Fournaise volcano is well detected at frequencies above 1 Hz.

  1. Method for processing seismic data to identify anomalous absorption zones

    DOEpatents

    Taner, M. Turhan

    2006-01-03

    A method is disclosed for identifying zones anomalously absorptive of seismic energy. The method includes jointly time-frequency decomposing seismic traces, low frequency bandpass filtering the decomposed traces to determine a general trend of mean frequency and bandwidth of the seismic traces, and high frequency bandpass filtering the decomposed traces to determine local variations in the mean frequency and bandwidth of the seismic traces. Anomalous zones are determined where there is difference between the general trend and the local variations.

  2. Seismic activity of Erebus volcano, antarctica

    NASA Astrophysics Data System (ADS)

    Kaminuma, Katsutada

    1987-11-01

    Mount Erebus is presently the only Antarctic volcano with sustained eruptive activity in the past few years. It is located on Ross Island and a convecting anorthoclase phonolite lava lake has occupied the summit crater of Mount Erebus from January 1973 to September 1984. A program to monitor the seismic activity of Mount Erebus named IMESS was started in December 1980 as an international cooperative program among Japan, the United States and New Zealand. A new volcanic episode began on 13 September, 1984 and continued until December. Our main observations from the seismic activity from 1982 1985 are as follows: (1) The average numbers of earthquakes which occurred around Mount Erebus in 1982, 1983 and January August 1984 were 64, 134 and 146 events per day, respectively. Several earthquake swarms occurred each year. (2) The averag number of earthquakes in 1985 is 23 events per day, with only one earthquake swarm. (3) A remarkable decrease of the background seismicity is recognized before and after the September 1984 activity. (4) Only a few earthquakes were located in the area surrounding Erebus mountain after the September 1984 activity. A magma reservoir is estimated to be located in the southwest area beneath the Erebus summit, based on the hypocenter distributions of earthquakes.

  3. Ionospheric Response Due to Seismic Activity

    NASA Astrophysics Data System (ADS)

    Sharma, Dinesh Kumar

    2016-07-01

    Signatures of the seismic activity in the ionospheric F2 region have been studied by analyzing the measurement of electron and ion temperatures during the occurrence of earthquake. The ionospheric electron and ion temperatures data recorded by the RPA payload aboard the Indian SROSS-C2 satellite during the period from January 1995 to December 2000 were used for the altitude range 430-630 km over Indian region. The normal day's electron and ion temperatures have been compared to the temperatures recorded during the seismic activity. The details of seismic events were obtained from USGS earthquake data information website. It has been found that the average electron temperature is enhanced during the occurrence of earthquakes by 1.2 to 1.5 times and this enhancement was for ion temperature ranging from 1.1to 1.3 times over the normal day's average temperatures. The above careful quantitative analysis of ionospheric electron and ion temperatures data shows the consistent enhancement in the ionospheric electron and ion temperatures. It is expected that the seismogenic vertical electrical field propagates up to the ionospheric heights and induces Joule heating that may cause the enhancement in ionospheric temperatures.

  4. Exploring the shallow structure of the San Ramón thrust fault in Santiago, Chile (~33.5° S), using active seismic and electric methods

    NASA Astrophysics Data System (ADS)

    Díaz, D.; Maksymowicz, A.; Vargas, G.; Vera, E.; Contreras-Reyes, E.; Rebolledo, S.

    2014-08-01

    The crustal-scale west-vergent San Ramón thrust fault system, which lies at the foot of the main Andean Cordillera in central Chile, is a geologically active structure with manifestations of late Quaternary complex surface rupture on fault segments along the eastern border of the city of Santiago. From the comparison of geophysical and geological observations, we assessed the subsurface structural pattern that affects the sedimentary cover and rock-substratum topography across fault scarps, which is critical for evaluating structural models and associated seismic hazard along the related faults. We performed seismic profiles with an average length of 250 m, using an array of 24 geophones (Geode), with 25 shots per profile, to produce high-resolution seismic tomography to aid in interpreting impedance changes associated with the deformed sedimentary cover. The recorded travel-time refractions and reflections were jointly inverted by using a 2-D tomographic approach, which resulted in variations across the scarp axis in both the velocities and the reflections that are interpreted as the sedimentary cover-rock substratum topography. Seismic anisotropy observed from tomographic profiles is consistent with sediment deformation triggered by west-vergent thrust tectonics along the fault. Electrical soundings crossing two fault scarps were used to construct subsurface resistivity tomographic profiles, which reveal systematic differences between lower resistivity values in the hanging wall with respect to the footwall of the geological structure, and clearly show well-defined east-dipping resistivity boundaries. These boundaries can be interpreted in terms of structurally driven fluid content change between the hanging wall and the footwall of the San Ramón fault. The overall results are consistent with a west-vergent thrust structure dipping ~55° E in the subsurface beneath the piedmont sediments, with local complexities likely associated with variations in fault

  5. Exploring the shallow structure of the San Ramón thrust fault in Santiago, Chile (∼33.5° S), using active seismic and electric methods

    NASA Astrophysics Data System (ADS)

    Díaz, D.; Maksymowicz, A.; Vargas, G.; Vera, E.; Contreras-Reyes, E.; Rebolledo, S.

    2014-01-01

    The crustal-scale west-vergent San Ramón thrust fault system at the foot of the main Andean Cordillera in central Chile is a geologically active structure with Quaternary manifestations of complex surface rupture along fault segments in the eastern border of Santiago city. From the comparison of geophysical and geological observations, we assessed the subsurface structure pattern affecting sedimentary cover and rock-substratum topography across fault scarps, which is critic for evaluating structural modeling and associated seismic hazard along this kind of faults. We performed seismic profiles with an average length of 250 m, using an array of twenty-four geophones (GEODE), and 25 shots per profile, supporting high-resolution seismic tomography for interpreting impedance changes associated to deformed sedimentary cover. The recorded traveltime refractions and reflections were jointly inverted by using a 2-D tomographic approach, which resulted in variations across the scarp axis in both velocities and reflections interpreted as the sedimentary cover-rock substratum topography. Seismic anisotropy observed from tomographic profiles is consistent with sediment deformation triggered by west-vergent thrust tectonics along the fault. Electrical soundings crossing two fault scarps supported subsurface resistivity tomographic profiles, which revealed systematic differences between lower resistivity values in the hanging wall with respect to the footwall of the geological structure, clearly limited by well-defined east-dipping resistivity boundaries. The latter can be interpreted in terms of structurally driven fluid content-change between the hanging wall and the footwall of a permeability boundary associated with the San Ramón fault. The overall results are consistent with a west-vergent thrust structure dipping ∼55° E at subsurface levels in piedmont sediments, with local complexities being probably associated to fault surface rupture propagation, fault-splay and

  6. Seismic active control by neural networks.

    SciTech Connect

    Tang, Y.

    1998-01-01

    A study on the application of artificial neural networks (ANNs) to activate structural control under seismic loads is carried out. The structure considered is a single-degree-of-freedom (SDF) system with an active bracing device. The control force is computed by a trained neural network. The feed-forward neural network architecture and an adaptive back-propagation training algorithm is used in the study. The neural net is trained to reproduce the function that represents the response-excitation relationship of the SDF system under seismic loads. The input-output training patterns are generated randomly. In the back-propagation training algorithm, the learning rate is determined by ensuring the decrease of the error function at each epoch. The computer program implemented is validated by solving the classification of the XOR problem. Then, the trained ANN is used to compute the control force according to the control strategy. If the control force exceeds the actuator's capacity limit, it is set equal to that limit. The concept of the control strategy employed herein is to apply the control force at every time step to cancel the system velocity induced at the preceding time step so that the gradual rhythmic buildup of the response is destroyed. The ground motions considered in the numerical example are the 1940 El Centro earthquake and the 1979 Imperial Valley earthquake in California. The system responses with and without the control are calculated and compared. The feasibility and potential of applying ANNs to seismic active control is asserted by the promising results obtained from the numerical examples studied.

  7. Seismic active control by neutral networks

    SciTech Connect

    Tang, Yu

    1995-12-31

    A study on the application of artificial neural networks (ANNs) to active structural control under seismic loads is carried out. The structure considered is a single-degree-of-freedom (SDF) system with an active bracing device. The control force is computed by a trained neural network. The feedforward neural network architecture and an adaptive backpropagation training algorithm is used in the study. The neural net is trained to reproduce the function that represents the response-excitation relationship of the SDF system under seismic loads. The input-output training patterns are generated randomly. In the backpropagation training algorithm, the learning rate is determined by ensuring the decrease of the error function at each epoch. The computer program implemented is validated by solving the classification of the XOR problem. Then, the trained ANN is used to compute the control force according to the control strategy. If the control force exceeds the actuator`s capacity limit, it is set equal to that limit. The concept of the control strategy employed herein is to apply the control force at every time step to cancel the system velocity induced at the preceding time step so that the gradual rhythmic buildup of the response is destroyed. The ground motions considered in the numerical example are the 1940 El Centro earthquake and the 1979 Imperial Valley earthquake in California. The system responses with and without the control are calculated and compared. The feasibility and potential of applying ANNs to seismic active control is asserted by the promising results obtained from the numerical examples studied.

  8. The seismicity of Ethiopia; active plate tectonics

    USGS Publications Warehouse

    Mohr, P.

    1981-01-01

    Ethiopia, descended from the semimythical Kingdom of Punt, lies at the strategic intersection of Schmidt's jigsaw puzzle where the Red Sea, Gulf of Aden, and the African Rift System meet. Because of geologically recent uplift combined with rapid downcutting erosion by rivers, notably the Blue Nile (Abbay), Ethiopia is the most mountainous country in Africa. It is also the most volcanically active, while its historical seismicity matches that of the midocean ridges. And, in a sense, Ethiopia is host to an evoloving ocean ridge system. 

  9. A comparison of active seismic source data to seismic excitations from the 2012 Tongariro volcanic eruptions, New Zealand

    NASA Astrophysics Data System (ADS)

    Jolly, Arthur; Kennedy, Ben; Keys, Harry; Lokmer, Ivan; Proctor, Jon; Lyons, John; Jolly, Gillian

    2014-05-01

    The 6 August 2012 eruption from Tongariro volcano's Te Maari vent comprised a complex sequence of events including at least 4 eruption jets, a large chasm collapse, and a debris avalanche (volume of ~7x105 m3) that propagated ~2 km beyond the eruptive vent. The eruption was poorly observed, being obscured by night time darkness, and the eruption chronology must be unravelled instead from a complex seismic record that includes discrete volcanic earthquakes, a sequence of low to moderate level spasmodic tremor and an intense burst of seismic and infrasound activity starting at 11:52:18 UTC that marked the eruption onset. We have discriminated the timing of the complex surface activity by comparing active seismic source data to the eruptive sequence. We dropped 11 high impact masses from helicopter to generate a range of active seismic sources in the vicinity of the eruption vent, chasm, and debris avalanche areas. We obtained 8 successful drops having an impact energy ranging from 3 to 9x106 joules producing seismic signals to a distance of 5 to 10 km and having good signal to noise characteristics in the 3-12 Hz range. For the 8 drops, we picked first-P arrival times and calculated amplitude spectra for a uniform set of four 3-component stations. From these, we obtained a distribution of amplitudes across the network for each drop position which varied systematically from the eruption vent and avalanche scar to the debris avalanche toe. We then compared these proxy source excitations to the natural eruption and pre-eruption data using a moving window cross-correlation approach. From the correlation processing, we found evidence for the debris avalanche a few minutes prior to the eruption in both the broad spectrum and narrow frequency (5-10 Hz) analysis. The total seismic energy release calculated from the new method is ~8x1011 joules, similar to an independently estimated calculation based on the radiated seismic energy. The inferred seismic energy release for the

  10. Method and apparatus for seismic exploration

    SciTech Connect

    Vogen, W.V.

    1987-06-23

    This patent describes a method for down-hole seismic exploration employing vibration emanating from a point deep in a well, comprising: attaching a spear to the lower end of the elastic steel column, the upper end of the column extending to the top of the well and above; attaching upper end of the column to a reaction mass vertically above and isolated from earth, through vertically mounted compression spring means and, in parallel with, a vertically mounted servo-controlled hydraulic cylinder-piston assembly; sensing the displacement of the spear relative to the earth in which the wall is located and developing from a displacement signal; reciprocating the piston in the hydraulic cylinder under servo control to apply vertical vibration to the upper end of the column and to the spear, while developing an electrical, pressure-differential signal corresponding to the pressure across the cylinder-piston assembly; adjusting the vertical vibration through the servo control in accordance with the displacement signal and the pressure differential signal, to seek and find an appropriate resonant frequency for the column in the range of 5 Hz to 250 Hz; maintaining the frequency at resonance generating and transmitting a down-hole signal; detecting the signal at a location at a known distance from the spear; and determining the time differential between transmission and detection of the signal.

  11. Seismic activity noted at Medicine Lake Highlands

    SciTech Connect

    Blum, D.

    1988-12-01

    The sudden rumble of earthquakes beneath Medicine Lake Highlands this fall gave geologists an early warning that one of Northern California's volcanoes may be stirring back to life. Researchers stressed that an eruption of the volcano is not expected soon. But the flurry of underground shocks in late September, combined with new evidence of a pool of molten rock beneath the big volcano, has led them to monitor Medicine Lake with new wariness. The volcano has been dormant since 1910, when it ejected a brief flurry of ash - worrying no one. A federal team plans to take measurements of Medicine Lake, testing for changes in its shape caused by underground pressures. The work is scheduled for spring because snows have made the volcano inaccessible. But the new seismic network is an effective lookout, sensitive to very small increases in activity.

  12. Erosion influences the seismicity of active thrust faults.

    PubMed

    Steer, Philippe; Simoes, Martine; Cattin, Rodolphe; Shyu, J Bruce H

    2014-01-01

    Assessing seismic hazards remains one of the most challenging scientific issues in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show via a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ~0.1-20 mm yr(-1), as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ~0.1-10 bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to trigger shallow seismicity or promote the rupture of deep continental earthquakes up to the surface. PMID:25412707

  13. Multidimensional analysis and probabilistic model of volcanic and seismic activities

    NASA Astrophysics Data System (ADS)

    Fedorov, V.

    2009-04-01

    A search for space and time regularities in volcanic and seismic events for the purpose of forecast method development seems to be of current concern, both scientifically and practically. The seismic and volcanic processes take place in the Earth's field of gravity which in turn is closely related to gravitational fields of the Moon, the Sun, and the planets of the Solar System. It is mostly gravity and tidal forces that exercise control over the Earth's configuration and relief. Dynamic gravitational interaction between the Earth and other celestial bodies makes itself evident in tidal phenomena and other effects in the geospheres (including the Earth's crust). Dynamics of the tidal and attractive forces is responsible for periodical changes in gravity force, both in value and direction [Darwin, 1965], in the rate of rotation and orbital speed; that implies related changes in the endogenic activity of the Earth. The Earth's rotation in the alternating gravitational field accounts to a considerable extent for regular pattern of crustal deformations and dislocations; it is among principal factors that control the Earth's form and structure, distribution of oceans and continents and, probably, continental drift [Peive, 1969; Khain, 1973; Kosygin, 1983]. The energy of gravitational interaction is transmitted through the tidal energy to planetary spheres and feeds various processes there, including volcanic and seismic ones. To determine degree, character and special features of tidal force contribution to the volcanic and seismic processes is of primary importance for understanding of genetic and dynamic aspects of volcanism and seismicity. Both volcanic and seismic processes are involved in evolution of celestial bodies; they are operative on the planets of the Earth group and many satellites [Essays…, 1981; Lukashov, 1996]. From this standpoint, studies of those processes are essential with a view to development of scenarios of the Earth's evolution as a celestial

  14. Multidimensional analysis and probabilistic model of volcanic and seismic activities

    NASA Astrophysics Data System (ADS)

    Fedorov, V.

    2009-04-01

    A search for space and time regularities in volcanic and seismic events for the purpose of forecast method development seems to be of current concern, both scientifically and practically. The seismic and volcanic processes take place in the Earth's field of gravity which in turn is closely related to gravitational fields of the Moon, the Sun, and the planets of the Solar System. It is mostly gravity and tidal forces that exercise control over the Earth's configuration and relief. Dynamic gravitational interaction between the Earth and other celestial bodies makes itself evident in tidal phenomena and other effects in the geospheres (including the Earth's crust). Dynamics of the tidal and attractive forces is responsible for periodical changes in gravity force, both in value and direction [Darwin, 1965], in the rate of rotation and orbital speed; that implies related changes in the endogenic activity of the Earth. The Earth's rotation in the alternating gravitational field accounts to a considerable extent for regular pattern of crustal deformations and dislocations; it is among principal factors that control the Earth's form and structure, distribution of oceans and continents and, probably, continental drift [Peive, 1969; Khain, 1973; Kosygin, 1983]. The energy of gravitational interaction is transmitted through the tidal energy to planetary spheres and feeds various processes there, including volcanic and seismic ones. To determine degree, character and special features of tidal force contribution to the volcanic and seismic processes is of primary importance for understanding of genetic and dynamic aspects of volcanism and seismicity. Both volcanic and seismic processes are involved in evolution of celestial bodies; they are operative on the planets of the Earth group and many satellites [Essays…, 1981; Lukashov, 1996]. From this standpoint, studies of those processes are essential with a view to development of scenarios of the Earth's evolution as a celestial

  15. Active seismic sources as a proxy for seismic surface processes: An example from the 2012 Tongariro volcanic eruptions, New Zealand

    NASA Astrophysics Data System (ADS)

    Jolly, A. D.; Lokmer, I.; Kennedy, B.; Keys, H. J. R.; Proctor, J.; Lyons, J. J.; Jolly, G. E.

    2014-10-01

    The 6 August 2012 eruption from Tongariro volcano's Te Maari vent comprised a complex sequence of events including at least 4 eruption pulses, a large chasm collapse, and a debris avalanche (volume of ~ 7 × 105 m3) that propagated ~ 2 km beyond the eruptive vent. The eruption was poorly observed, being obscured by night time darkness, and the eruption timing must be unravelled instead from a complex seismic record that includes discrete volcanic earthquakes, a sequence of low to moderate level spasmodic tremor and an intense burst of seismic and infrasound activity that marked the eruption onset. We have discriminated the evolution of the complex surface activity by comparing active seismic source data to the seismic sequence in a new cross correlation source location approach. We dropped 11 high impact masses from helicopter to generate a range of active seismic sources in the vicinity of the eruption vent, chasm, and debris avalanche areas. We obtained 8 successful drops having an impact energy ranging from 3 to 9 × 106 Nm producing observable seismic signals to a distance of 5 to 10 km and having good signal to noise characteristics in the 3-12 Hz range. For the 8 drops, we picked first-P arrival times and calculated amplitude spectra for a uniform set of four stations. We then compared these proxy source excitations to the natural eruption and pre-eruption data using a moving window cross correlation approach. From the correlation processing, we obtain a best matched source position in the near vent region for the eruption period and significant down channel excitations during both the pre and post eruption periods. The total seismic energy release calculated from the new method is ~ 8 × 1011 Nm, similar to an independently estimated calculation based on the radiated seismic energy. The new energy estimate may be more robust than those calculated from standard seismic radiation equations, which may include uncertainties about the path and site effects. The

  16. The Pollino Seismic Sequence: Activated Graben Structures in a Seismic Gap

    NASA Astrophysics Data System (ADS)

    Rößler, Dirk; Passarelli, Luigi; Govoni, Aladino; Bindi, Dino; Cesca, Simone; Hainzl, Sebatian; Maccaferri, Francesco; Rivalta, Eleonora; Woith, Heiko; Dahm, Torsten

    2015-04-01

    The Mercure Basin (MB) and the Castrovillari Fault (CF) in the Pollino range (Southern Apennines, Italy) represent one of the most prominent seismic gaps in the Italian seismic catalogue, with no M>5.5 earthquakes during the last centuries. In historical times several swarm-like seismic sequences occurred in the area including two intense swarms within the past two decades. The most energetic one started in 2010 and has been still active in 2014. The seismicity culminated in autumn 2012 with a M=5 event on 25 October. The range hosts a number of opposing normal faults forming a graben-like structure. Their rheology and their interactions are unclear. Current debates include the potential of the MB and the CF to host large earthquakes and the style of deformation. Understanding the seismicity and the behaviour of the faults is necessary to assess the tectonics and the seismic hazard. The GFZ German Research Centre for Geosciences and INGV, Italy, have jointly monitored the ongoing seismicity using a small-aperture seismic array, integrated in a temporary seismic network. Based on this installation, we located more than 16,000 local earthquakes that occurred between November 2012 and September 2014. Here we investigate quantitatively all the phases of the seismic sequence starting from January 2010. Event locations along with moment tensor inversion constrain spatially the structures activated by the swarm and the migration pattern of the seismicity. The seismicity forms clusters concentrated within the southern part of the MB and along the Pollino Fault linking MB and CF. Most earthquakes are confined to the upper 10 km of the crust in an area of ~15x15 km2. However, sparse seismicity at depths between 15 and 20 km and moderate seismicity further north with deepening hypocenters also exist. In contrast, the CF appears aseismic; only the northern part has experienced micro-seismicity. The spatial distribution is however more complex than the major tectonic structures

  17. Optical seismic sensor systems and methods

    DOEpatents

    Beal, A. Craig; Cummings, Malcolm E.; Zavriyev, Anton; Christensen, Caleb A.; Lee, Keun

    2015-12-08

    Disclosed is an optical seismic sensor system for measuring seismic events in a geological formation, including a surface unit for generating and processing an optical signal, and a sensor device optically connected to the surface unit for receiving the optical signal over an optical conduit. The sensor device includes at least one sensor head for sensing a seismic disturbance from at least one direction during a deployment of the sensor device within a borehole of the geological formation. The sensor head includes a frame and a reference mass attached to the frame via at least one flexure, such that movement of the reference mass relative to the frame is constrained to a single predetermined path.

  18. Seismic Hazard Assessment for a Characteristic Earthquake Scenario: Probabilistic-Deterministic Method

    NASA Astrophysics Data System (ADS)

    mouloud, Hamidatou

    2016-04-01

    The objective of this paper is to analyze the seismic activity and the statistical treatment of seismicity catalog the Constantine region between 1357 and 2014 with 7007 seismic event. Our research is a contribution to improving the seismic risk management by evaluating the seismic hazard in the North-East Algeria. In the present study, Earthquake hazard maps for the Constantine region are calculated. Probabilistic seismic hazard analysis (PSHA) is classically performed through the Cornell approach by using a uniform earthquake distribution over the source area and a given magnitude range. This study aims at extending the PSHA approach to the case of a characteristic earthquake scenario associated with an active fault. The approach integrates PSHA with a high-frequency deterministic technique for the prediction of peak and spectral ground motion parameters in a characteristic earthquake. The method is based on the site-dependent evaluation of the probability of exceedance for the chosen strong-motion parameter. We proposed five sismotectonique zones. Four steps are necessary: (i) identification of potential sources of future earthquakes, (ii) assessment of their geological, geophysical and geometric, (iii) identification of the attenuation pattern of seismic motion, (iv) calculation of the hazard at a site and finally (v) hazard mapping for a region. In this study, the procedure of the earthquake hazard evaluation recently developed by Kijko and Sellevoll (1992) is used to estimate seismic hazard parameters in the northern part of Algeria.

  19. Precursory Seismic Migration Patterns Examined by Improved Pattern Informatics Method

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Chen, C.; Rundle, J. B.; Wang, J.

    2010-12-01

    The pattern informatics (PI) method is a statistical method for forecasting earthquakes based on the concept of pattern dynamics. It could detect precursory seismic activation or quiescence. Here we apply the PI method with the frequency- magnitude distribution (FMD) of events, based on the self-organized spinodal (SOS) behavior, on the Chi-Chi and Pingtung earthquakes using the earthquake catalog provided by the Central Weather Bureau. By the FMD test, two important times before a large earthquake when the number of intermediate-sized events has significant increase are found. The PI hotspots which indicate the location with anomalous seismicity are around the epicentral area in stage 2 of the SOS behavior. When it proceeded to stage 3, the hotspots migrate to the epicenter. This migration is not only observed in the PI maps but also quantified and visualized from the calculation of the distances between the epicenter and hotspots. Investigating the evolution of the distance in time yields a slope that indicates the trend suggesting how the hotspots propagate relative to sites. After imaging all slopes on a map, we can get a donut-like pattern that illustrates the migration process. In general, migration occurs intensively in stage 2. The migration process might be introduced by the nucleation of earthquakes, and its duration and range depend on the size of the mainshock. After migration in stage 2, the number of intermediate-sized events increases during stage 3, called the precursory period, in SOS behavior. Such an increase occurs on the epicentral region and might be associated with accelerating seismicity observed in many studies. The improved PI method shows that anomalous precursor signature would be exposed by the seismicity rate not only in a static form but also in a dynamic form. The static form means that the PI hotspots point out a location with high hazard, while the dynamic form shows the preparing process (migration) before a large earthquake. Thus

  20. Method for determining formation quality factor from seismic data

    DOEpatents

    Taner, M. Turhan; Treitel, Sven

    2005-08-16

    A method is disclosed for calculating the quality factor Q from a seismic data trace. The method includes calculating a first and a second minimum phase inverse wavelet at a first and a second time interval along the seismic data trace, synthetically dividing the first wavelet by the second wavelet, Fourier transforming the result of the synthetic division, calculating the logarithm of this quotient of Fourier transforms and determining the slope of a best fit line to the logarithm of the quotient.

  1. Evidences for higher nocturnal seismic activity at the Mt. Vesuvius

    NASA Astrophysics Data System (ADS)

    Mazzarella, Adriano; Scafetta, Nicola

    2016-07-01

    We analyze hourly seismic data measured at the Osservatorio Vesuviano Ovest (OVO, 1972-2014) and at the Bunker Est (BKE, 1999-2014) stations on the Mt. Vesuvius. The OVO record is complete for seismic events with magnitude M ≥ 1.9. We demonstrate that before 1996 this record presents a daily oscillation that nearly vanishes afterwards. To determine whether a daily oscillation exists in the seismic activity of the Mt. Vesuvius, we use the higher quality BKE record that is complete for seismic events with magnitude M ≥ 0.2. We demonstrate that BKE confirms that the seismic activity at the Mt. Vesuvius is higher during nighttime than during daytime. The amplitude of the daily oscillation is enhanced during summer and damped during winter. We speculate possible links with the cooling/warming diurnal cycle of the volcanic edifice, with external geomagnetic field and with magnetostriction, which stress the rocks. We find that the amplitude of the seismic daily cycle changes in time and has been increasing since 2008. Finally, we propose a seismic activity index to monitor the 24-hour oscillation that could be used to complement other methodologies currently adopted to determine the seismic status of the volcano to prevent the relative hazard.

  2. Monitoring of stressed state in seismic-prone zones using vibroseismic interferometry method

    NASA Astrophysics Data System (ADS)

    Kovalevsky, V.

    2003-04-01

    Experiments with powerful seismic vibrators carried out in the Siberian Branch of RAS have shown the possibility to investigate the small changes of the tensely-deformed state of a seismic-prone zone of 300 - 500 km size. The method of vibroseismic interferometry was used in these experiments. It is based on the seismic sounding of the region by powerful seismic vibrators with the long-time narrow-band harmonic signal radiation. Changes of the tensely-deformed state are determined through variations of the amplitude- phase characteristics of the stationary wave fields, which are excited in a medium due to the long-time radiation of harmonic signals of constant frequency from the vibrator. The method of vibroseismic interferometry has high sensitivity to the time changes of parameters of the medium in the case of the long-distance observations. The influence of the lunar-solar tides deformations of the Earth's crust on the seismic waves velocities was investigated in the experiments with a 100-ton force seismic vibrator and recording systems of vibroseismic signals, located at distances of 356 - 430 km from a source. It was determined that the variations of the seismic waves velocities are about 10-5 - 10-6 and have 12- and 24-hour periodicity well correlated with the lunar-solar tides periodicity. This method can be efficiently used to define the first changes of the stress in the medium and location of the areas of such changes in the seismic-prone zone. Now an experimental system of active vibroseismic monitoring of the seismic-prone zones, which includes powerful 100- ton force vibrators, mobile seismic arrays for vibrosignals recording and computer systems for the vibromonitoring data processing is created.

  3. Continuous, Large-Scale Processing of Seismic Archives for High-Resolution Monitoring of Seismic Activity and Seismogenic Properties

    NASA Astrophysics Data System (ADS)

    Waldhauser, F.; Schaff, D. P.

    2012-12-01

    Archives of digital seismic data recorded by seismometer networks around the world have grown tremendously over the last several decades helped by the deployment of seismic stations and their continued operation within the framework of monitoring earthquake activity and verification of the Nuclear Test-Ban Treaty. We show results from our continuing effort in developing efficient waveform cross-correlation and double-difference analysis methods for the large-scale processing of regional and global seismic archives to improve existing earthquake parameter estimates, detect seismic events with magnitudes below current detection thresholds, and improve real-time monitoring procedures. We demonstrate the performance of these algorithms as applied to the 28-year long seismic archive of the Northern California Seismic Network. The tools enable the computation of periodic updates of a high-resolution earthquake catalog of currently over 500,000 earthquakes using simultaneous double-difference inversions, achieving up to three orders of magnitude resolution improvement over existing hypocenter locations. This catalog, together with associated metadata, form the underlying relational database for a real-time double-difference scheme, DDRT, which rapidly computes high-precision correlation times and hypocenter locations of new events with respect to the background archive (http://ddrt.ldeo.columbia.edu). The DDRT system facilitates near-real-time seismicity analysis, including the ability to search at an unprecedented resolution for spatio-temporal changes in seismogenic properties. In areas with continuously recording stations, we show that a detector built around a scaled cross-correlation function can lower the detection threshold by one magnitude unit compared to the STA/LTA based detector employed at the network. This leads to increased event density, which in turn pushes the resolution capability of our location algorithms. On a global scale, we are currently building

  4. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    SciTech Connect

    Lestari, Titik; Nugraha, Andri Dian

    2015-04-24

    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA’s) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 – April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  5. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    NASA Astrophysics Data System (ADS)

    Lestari, Titik; Nugraha, Andri Dian

    2015-04-01

    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA's) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 - April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  6. ActiveSeismoPick3D - automatic first arrival determination for large active seismic arrays

    NASA Astrophysics Data System (ADS)

    Paffrath, Marcel; Küperkoch, Ludger; Wehling-Benatelli, Sebastian; Friederich, Wolfgang

    2016-04-01

    We developed a tool for automatic determination of first arrivals in active seismic data based on an approach, that utilises higher order statistics (HOS) and the Akaike information criterion (AIC), commonly used in seismology, but not in active seismics. Automatic picking is highly desirable in active seismics as the number of data provided by large seismic arrays rapidly exceeds of what an analyst can evaluate in a reasonable amount of time. To bring the functionality of automatic phase picking into the context of active data, the software package ActiveSeismoPick3D was developed in Python. It uses a modified algorithm for the determination of first arrivals which searches for the HOS maximum in unfiltered data. Additionally, it offers tools for manual quality control and postprocessing, e.g. various visualisation and repicking functionalities. For flexibility, the tool also includes methods for the preparation of geometry information of large seismic arrays and improved interfaces to the Fast Marching Tomography Package (FMTOMO), which can be used for the prediction of travel times and inversion for subsurface properties. Output files are generated in the VTK format, allowing the 3D visualization of e.g. the inversion results. As a test case, a data set consisting of 9216 traces from 64 shots was gathered, recorded at 144 receivers deployed in a regular 2D array of a size of 100 x 100 m. ActiveSeismoPick3D automatically checks the determined first arrivals by a dynamic signal to noise ratio threshold. From the data a 3D model of the subsurface was generated using the export functionality of the package and FMTOMO.

  7. A new passive seismic method based on seismic interferometry and multichannel analysis of surface waves

    NASA Astrophysics Data System (ADS)

    Cheng, Feng; Xia, Jianghai; Xu, Yixian; Xu, Zongbo; Pan, Yudi

    2015-06-01

    We proposed a new passive seismic method (PSM) based on seismic interferometry and multichannel analysis of surface waves (MASW) to meet the demand for increasing investigation depth by acquiring surface-wave data at a low-frequency range (1 Hz ≤ f ≤ 10 Hz). We utilize seismic interferometry to sort common virtual source gathers (CVSGs) from ambient noise and analyze obtained CVSGs to construct 2D shear-wave velocity (Vs) map using the MASW. Standard ambient noise processing procedures were applied to the computation of cross-correlations. To enhance signal to noise ratio (SNR) of the empirical Green's functions, a new weighted stacking method was implemented. In addition, we proposed a bidirectional shot mode based on the virtual source method to sort CVSGs repeatedly. The PSM was applied to two field data examples. For the test along Han River levee, the results of PSM were compared with the improved roadside passive MASW and spatial autocorrelation method (SPAC). For test in the Western Junggar Basin, PSM was applied to a 70 km long linear survey array with a prominent directional urban noise source and a 60 km-long Vs profile with 1.5 km in depth was mapped. Further, a comparison about the dispersion measurements was made between PSM and frequency-time analysis (FTAN) technique to assess the accuracy of PSM. These examples and comparisons demonstrated that this new method is efficient, flexible, and capable to study near-surface velocity structures based on seismic ambient noise.

  8. Erosion influence the seismicity of active thrust faults

    NASA Astrophysics Data System (ADS)

    Steer, Philippe; Simoes, Martine; Cattin, Rodolphe; Shyu, J. Bruce H.

    2015-04-01

    Assessing seismic hazards remains one of the most challenging scientific issue in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show with a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ~0.1 to 20 mm/yr, as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ~0.1 to ~10 bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to promote the rupture of deep continental earthquakes up to the surface or to trigger shallow seismicity. We illustrate this last point by identifying seismic events in Taiwan, by the mean of a coupled statistical and mechanical approach, that were induced by intense erosional events.

  9. Erosion influence the seismicity of active thrust faults

    NASA Astrophysics Data System (ADS)

    Steer, Philippe; Simoes, Martine; Cattin, Rodolphe; Shyu, J. Bruce H.

    2016-04-01

    Assessing seismic hazards remains one of the most challenging scientific issue in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show with a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ˜0.1 to 20 mm/yr, as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ˜0.1 to ˜10 bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to promote the rupture of deep continental earthquakes up to the surface or to trigger shallow seismicity. We illustrate this last point by identifying seismic events in Taiwan, by the mean of a coupled statistical and mechanical approach, that were induced by intense erosional events.

  10. Application of neural networks to seismic active control

    SciTech Connect

    Tang, Yu

    1995-07-01

    An exploratory study on seismic active control using an artificial neural network (ANN) is presented in which a singledegree-of-freedom (SDF) structural system is controlled by a trained neural network. A feed-forward neural network and the backpropagation training method are used in the study. In backpropagation training, the learning rate is determined by ensuring the decrease of the error function at each training cycle. The training patterns for the neural net are generated randomly. Then, the trained ANN is used to compute the control force according to the control algorithm. The control strategy proposed herein is to apply the control force at every time step to destroy the build-up of the system response. The ground motions considered in the simulations are the N21E and N69W components of the Lake Hughes No. 12 record that occurred in the San Fernando Valley in California on February 9, 1971. Significant reduction of the structural response by one order of magnitude is observed. Also, it is shown that the proposed control strategy has the ability to reduce the peak that occurs during the first few cycles of the time history. These promising results assert the potential of applying ANNs to active structural control under seismic loads.

  11. Precursory seismic activity before the 1944 Tonankai (Japan) earthquake: focusing on the downward migration of seismic activity

    NASA Astrophysics Data System (ADS)

    Mogi, Kiyoo

    1987-08-01

    Based on the latest JMA earthquake catalog, the author investigated seismic activity around the time of the 1944 Tonankai earthquake ( M 7.9, M w 8.1 ) and the 1946 Nankaido earthquake ( M 8.1, M w 8.1 ), which were both great thrust-type earthquakes along the Nankai Trough. For about 20 years before these earthquakes their focal regions had been quiescent (appearance of a seismic gap of the second kind) and the surrounding areas had become increasingly active, forming a doughnut pattern). Several years before these earthquakes occurred seismic activity increased at shallow depths of the area to the north. This activity gradually migrated downwards, and the Tonankai earthquake occurred when it reached its limit (a depth of approximately 70 km). The author has previously reported on several cases of increased activity in the deep seismic plane at a depth of 300-500 km prior to large shallow earthquakes along the Japan Trench (Mogi, 1973). This paper will demonstrate that a similar phenomenon occurs when the depth of the deep seismic plane is only about 70 km. For several years before the Tonankai earthquake there had been a slight increase in seismicity in the area along the trough, which is where the plate subducts. Two or three days before tne earthquake marked ground tilt also proceeded at the northeastern tip of the focal region. It is evident that the Tonankai earthquake was preceded by various long-term and short-term precursory phenomena.

  12. Analysing seismic-source mechanisms by linear-programming methods.

    USGS Publications Warehouse

    Julian, B.R.

    1986-01-01

    Linear-programming methods are powerful and efficient tools for objectively analysing seismic focal mechanisms and are applicable to a wide range of problems, including tsunami warning and nuclear explosion identification. The source mechanism is represented as a point in the 6-D space of moment-tensor components. The present method can easily be extended to fit observed seismic-wave amplitudes (either signed or absolute) subject to polarity constraints, and to assess the range of mechanisms consistent with a set of measured amplitudes. -from Author

  13. Method for determining source and receiver statics in marine seismic exploration

    SciTech Connect

    Zachariadis, R.G.

    1986-04-08

    A method for seismic exploration at a marine exploration site, is described which consists of the steps of: a. fixing a seismic energy source and a seismic energy detector on the water bottom at a point offset from a marine exploration line, b. traversing the marine vessel towing a seismic energy source and a seismic marine cable employing a plurality of spaced-apart hydrophones, c. generating seismic energy from the towed seismic energy source to produce a seismic reflection signal that is detected by the plurality of hydrophones on the seismic marine cable and a first seismic refraction signal that is detected by the fixed seismic energy detector, the first seismic refraction signal including a source statics attributable to time delay in the near surface earth formation directly below the towed seismic energy source, d. generating seismic energy from the fixed seismic energy source to produce a second seismic refraction signal that is detected by each of the plurality of hydrophones on the seismic marine cable, the second seismic refraction signal including a receiver statics attributable to time delay in the near surface earth formation directly below each of the pluarlity of hydrophones.

  14. Reversible rigid coupling apparatus and method for borehole seismic transducers

    DOEpatents

    Owen, Thomas E.; Parra, Jorge O.

    1992-01-01

    An apparatus and method of high resolution reverse vertical seismic profile (VSP) measurements is shown. By encapsulating the seismic detector and heaters in a meltable substance (such as wax), the seismic detector can be removably secured in a borehole in a manner capable of measuring high resolution signals in the 100 to 1000 hertz range and higher. The meltable substance is selected to match the overall density of the detector package with the underground formation, yet still have relatively low melting point and rigid enough to transmit vibrations to accelerometers in the seismic detector. To minimize voids in the meltable substance upon solidification, the meltable substance is selected for minimum shrinkage, yet still having the other desirable characteristics. Heaters are arranged in the meltable substance in such a manner to allow the lowermost portion of the meltable substance to cool and solidify first. Solidification continues upwards from bottom-to-top until the top of the meltable substance is solidified and the seismic detector is ready for use. To remove, the heaters melt the meltable substance and the detector package is pulled from the borehole.

  15. Methods for use in detecting seismic waves in a borehole

    DOEpatents

    West, Phillip B.; Fincke, James R.; Reed, Teddy R.

    2007-02-20

    The invention provides methods and apparatus for detecting seismic waves propagating through a subterranean formation surrounding a borehole. In a first embodiment, a sensor module uses the rotation of bogey wheels to extend and retract a sensor package for selective contact and magnetic coupling to casing lining the borehole. In a second embodiment, a sensor module is magnetically coupled to the casing wall during its travel and dragged therealong while maintaining contact therewith. In a third embodiment, a sensor module is interfaced with the borehole environment to detect seismic waves using coupling through liquid in the borehole. Two or more of the above embodiments may be combined within a single sensor array to provide a resulting seismic survey combining the optimum of the outputs of each embodiment into a single data set.

  16. Seismic activity in the Sunnyside mining district, Utah, during 1967

    USGS Publications Warehouse

    Barnes, Barton K.; Dunrud, C. Richard; Hernandez, Jerome

    1969-01-01

    A seismic monitoring network near Sunnyside, Utah, consisting of a triangular array of seismometer stations that encompasses most of the mine workings in the district, recorded over 50,000 local earth tremors during 1967. About 540 of the tremors were of sufficient magnitude to be accurately located. Most of these were located within 2-3 miles of mine workings and were also near known or suspected faults. The district-wide seismic activity generally consisted of two different patterns--a periodic increase in the daily number of tremors at weekly intervals, and also a less regular and longer term increase and decrease of seismic activity that occurred over a period of weeks or even months. The shorter and more regular pattern can be correlated with the mine work week and seems to result from mining. The longer term activity, however, does not correlate with known mining causes sad therefore seems to be .caused by natural stresses.

  17. An Updated Eurasian Crustal Model Using Multiple Seismic Methods

    NASA Astrophysics Data System (ADS)

    Detweiler, S.; Mooney, W. D.; McDonald, S.

    2006-12-01

    An updated 2 by 2 degree crustal model for greater Eurasia is being completed from (1) synthesizing existing models, such as WENA 1.0, the new Barents Sea model, and WINPAK; (2) Pn/Sn tomography data; (3) our ongoing compilation of published seismic models for the crust, based on active- and passive-source seismology; and (4) observed and calculated seismic surface wave group and phase velocity maps. In particular, three controlled source studies from China and India completed by the U.S. Geological Survey and colleagues in the past year are contributing to this updated Eurasian crustal model. These include: (1) three short (20-35 km) seismic reflection profiles from the immediate region of the 2001 Mw 7.7 Bhuj (western India) earthquake that yielded a crustal thickening from 35 to 45 km over a distance of about 50 km from the northern margin of the Gulf of Kutch to the epicentral zone of the earthquake; (2) a compilation of over 90 seismic refraction/wide angle reflection profiles, with a cumulative length of more than sixty thousand kilometers, across mainland China that have shown a mid-crustal low velocity layer in unstable regions; and (3) a 1000- km-long geophysical profile from Darlag-Lanzhou-Jingbian extending from the Songpan-Ganzi terrane to the Ordos basin in the NE margin of the Tibetan plateau that yielded a 2-D seismic velocity profile from which crustal composition and continental dynamics of the Tibetan plateau are inferred. New crustal depth and velocity maps for greater Eurasia have been compiled, which incorporate the results from the above three studies and other relevant controlled source experiments. This updated compilation of Eurasian Pn and Sn data in CRUST 2.2 will yield more detailed models of the Earth's structure and subsequently more accurate seismic monitoring. Well-resolved crustal models are critical for determining event locations and size estimations.

  18. Detecting Seismic Activity with a Covariance Matrix Analysis of Data Recorded on Seismic Arrays

    NASA Astrophysics Data System (ADS)

    Seydoux, L.; Shapiro, N.; de Rosny, J.; Brenguier, F.

    2014-12-01

    Modern seismic networks are recording the ground motion continuously all around the word, with very broadband and high-sensitivity sensors. The aim of our study is to apply statistical array-based approaches to processing of these records. We use the methods mainly brought from the random matrix theory in order to give a statistical description of seismic wavefields recorded at the Earth's surface. We estimate the array covariance matrix and explore the distribution of its eigenvalues that contains information about the coherency of the sources that generated the studied wavefields. With this approach, we can make distinctions between the signals generated by isolated deterministic sources and the "random" ambient noise. We design an algorithm that uses the distribution of the array covariance matrix eigenvalues to detect signals corresponding to coherent seismic events. We investigate the detection capacity of our methods at different scales and in different frequency ranges by applying it to the records of two networks: (1) the seismic monitoring network operating on the Piton de la Fournaise volcano at La Réunion island composed of 21 receivers and with an aperture of ~15 km, and (2) the transportable component of the USArray composed of ~400 receivers with ~70 km inter-station spacing.

  19. Study of Seismic Activity at Ceboruco Volcano, Mexico

    NASA Astrophysics Data System (ADS)

    Nunez-Cornu, F. J.; Escudero, C. R.; Rodríguez Ayala, N. A.; Suarez-Plascencia, C.

    2013-12-01

    Many societies and their economies endure the disastrous consequences of destructive volcanic eruptions. The Ceboruco stratovolcano (2,280 m.a.s.l.) is located in Nayarit, Mexico, at the west of the Mexican volcanic belt and towards the Sierra de San Pedro southeast, which is a key communication point for coast of Jalisco and Nayarit and the northwest of Mexico. It last eruptive activity was in 1875, and during the following five years it presents superficial activity such as vapor emissions, ash falls and riodacitic composition lava flows along the southeast side. Although surface activity has been restricted to fumaroles near the summit, Ceboruco exhibits regular seismic unrest characterized by both low frequency seismic events and volcano-tectonic earthquakes. From March 2003 until July 2008 a three-component short-period seismograph Marslite station with a Lennartz 3D (1Hz) was deployed in the south flank (CEBN) and within 2 km from the summit to monitoring the seismic activity at the volcano. The LF seismicity recorded was classified using waveform characteristics and digital analysis. We obtained four groups: impulsive arrivals, extended coda, bobbin form, and wave package amplitude modulation earthquakes. The extended coda is the group with more earthquakes and present durations of 50 seconds. Using the moving particle technique, we read the P and S wave arrival times and estimate azimuth arrivals. A P-wave velocity of 3.0 km/s was used to locate the earthquakes, most of the hypocenters are below the volcanic edifice within a circular perimeter of 5 km of radius and its depths are calculated relative to the CEBN elevation as follows. The impulsive arrivals earthquakes present hypocenters between 0 and 1 km while the other groups between 0 and 4 km. Results suggest fluid activity inside the volcanic building that could be related to fumes on the volcano. We conclude that the Ceboruco volcano is active. Therefore, it should be continuously monitored due to the

  20. Crustal Deformation around Zhangjiakou-Bohai Seismically Active Belt

    NASA Astrophysics Data System (ADS)

    Jin, H.; Fu, G.; Kato, T.

    2011-12-01

    Zhangjiakou-Bohai belt is a seismically active belt located in Northern China around Beijing, the capital of China. Near such a belt many great earthquakes occurred in the past centuries (e.g. the 1976 Tanshan Ms7.8 earthquake, the 1998 Zhangbei Ms6.2 earthquake, etc). Chinese Government established dense permanent and regional Global Positioning System (GPS) stations in and near the area. We collected and analyzed all the GPS observation data between 1999 and 2009 around Zhangjiakou-Bohai seismic belt, and obtained velocities at 143 stations. At the same time we investigated Zhangjiakou-Bohai belt slip rate for three profiles from northwest to southeast, and constructed a regional strain field on the Zhangjiakou-Bohai seismic belt region by least-square collocation. Based on the study we found that: 1) Nowadays the Zhangjiakou-Bohai seismic belt is creeping with left-lateral slip rate of 2.0mm~2.4mm/a, with coupling depth of 35~50km; 2) In total, the slip and coupling depth of the northwestern seismic belt is less than the one of southeast side; 3) The maximum shear strain is about 3×10-8 at Beijing-Tianjin-Tangshan area.

  1. Application of Seismic Interferometry Method by Using Portable Seismometer for Delineating the Sedimentary Structure of Pohang Basin, Korea

    NASA Astrophysics Data System (ADS)

    Kim, H.; Li, X.; So, Y.

    2012-12-01

    Pohang Basin consisting of non-marine to deep-marine strata, occurs along the southeastern coast of the Korean Peninsula and the basin is believed to have the potential of carbon dioxide sequestration. We have applied the seismic interferometry method by using portable 72 channels seismometer with normal velocity geophones for delineating the sedimentary structure of the basin and for checking the preliminary feasibility of geological storage of carbon dioxide. Comparing with the surface wave, reflected and refracted waves have low energy and it is difficult to retrieve the reflected and refracted waves from the ambient seismic noise by using interferometry method. So it is more challenging to delineate the seismic reflection and refraction signals by the interferometry method for seismic section or travel time curve. The reflection and refraction signals were retrieved from 100 ambient seismic noise data by bandpass filtering, crosscorrelation and stacking. The preliminary reflection seismic sections and travel time curves were prepared by using interferometry method and the sections and curves were compared with those of obtained by active sources using sledge hammer in the same lines. The results do not show clear reflection and refraction signals but some parts give comparable signals similar with the signals obtained by active sources. This implies the possibility of seismic interferomety method to retrieve the reflection and refraction signals by portable seismometer in near surface mapping.

  2. An extended stochastic method for seismic hazard estimation

    NASA Astrophysics Data System (ADS)

    Abd el-aal, A. K.; El-Eraki, M. A.; Mostafa, S. I.

    2015-12-01

    In this contribution, we developed an extended stochastic technique for seismic hazard assessment purposes. This technique depends on the hypothesis of stochastic technique of Boore (2003) "Simulation of ground motion using the stochastic method. Appl. Geophy. 160:635-676". The essential characteristics of extended stochastic technique are to obtain and simulate ground motion in order to minimize future earthquake consequences. The first step of this technique is defining the seismic sources which mostly affect the study area. Then, the maximum expected magnitude is defined for each of these seismic sources. It is followed by estimating the ground motion using an empirical attenuation relationship. Finally, the site amplification is implemented in calculating the peak ground acceleration (PGA) at each site of interest. We tested and applied this developed technique at Cairo, Suez, Port Said, Ismailia, Zagazig and Damietta cities to predict the ground motion. Also, it is applied at Cairo, Zagazig and Damietta cities to estimate the maximum peak ground acceleration at actual soil conditions. In addition, 0.5, 1, 5, 10 and 20 % damping median response spectra are estimated using the extended stochastic simulation technique. The calculated highest acceleration values at bedrock conditions are found at Suez city with a value of 44 cm s-2. However, these acceleration values decrease towards the north of the study area to reach 14.1 cm s-2 at Damietta city. This comes in agreement with the results of previous studies of seismic hazards in northern Egypt and is found to be comparable. This work can be used for seismic risk mitigation and earthquake engineering purposes.

  3. An active seismic experiment proposal onboard the NASA 2009 MSL

    NASA Astrophysics Data System (ADS)

    Lognonné, P.; Experiment Team

    NASA will launch in 2009 a 900 kg class rover to Mars. This rover will land with a new descent system, called the ``sky-crane''. After releasing the rover on the ground, the sky-crane will have a final flight until a hard landing about 2 km away from the rover. The science objectives of the 2009 MSL mission, among others, are to characterize the geology of the landing region at all appropriate spatial scales, to interpret the processes that have formed and modified rocks and regolith and to determine present state, distribution, and cycling of water. We propose to perform with the sky-crane an active seismic experiment for subsurface characterization. This experiment will be conducted after the rover deployment. The proposed idea is to deploy a seismic receiver line by ejecting about 10 seismic nodes from the sky-crane and then to record then the reflected signals from the impact of the sky-crane. Preliminary modeling and tests indicate that a penetration depth of several hundred meters will be reached. The experiment will be used to determine a 2D geological profile of the landing site subsurface, to determine the depth and shape of the dry regolith/icy regolith discontinuity and to identify possible layering structures in the subsurface. In addition, information on the structure of the regolith (mean size of building blocs) and on the presence of liquid water will be obtained by an analysis of the seismic coda and attenuation. The seismic high frequency noise will also be monitored, especially during windy periods, and will be used to get additional information on the subsurface. The proposed experiment is based on a consortium between academics laboratories and seismic industry and will be a first example of a resource oriented experiment on another planet than Earth. The complete mass of the experiment will be 2.5 kg. Seismic nodes will have their own acquisition/power and telemetry system and will be based on high sensitive geophones developed for seismic

  4. Array analysis methods for detection, classification and location of seismic sources: a first evaluation for aftershock analysis using dense temporary post-seismic array network

    NASA Astrophysics Data System (ADS)

    Poiata, N.; Satriano, C.; Vilotte, J.; Bernard, P.

    2012-12-01

    Detection, separation, classification and location of distributed non stationary seismic sources in broadband noisy environment is an important problem in seismology, in particular for monitoring the high-level post-seismic activity following large subduction earthquakes, like the off-shore Maule (Mw 8.8, 2010) earthquake in Central Chile. Multiple seismic arrays, and local antenna, distributed over a region allow exploiting frequency selective coherence of the signals that arrive at widely-separated array stations, leading to improved detection, convolution blind source separation, and location of distributed non stationary sources. We present here first results on the investigation of time-frequency adaptive array analysis techniques for detection and location of broadband distributed seismic events recorded by the dense temporary seismic network (International Maule Aftershock Deployment, IMAD) installed for monitoring the high-level seismic activity following the 27 February 2010 Maule earthquake (Mw 8.8). This seismic network is characterized by a large aperture, with variable inter-station distances, corroborated with a high level of distributed near and far field seismic source activity and noise. For this study, we first extract from the post-seismic network a number of seismic arrays distributed over the region covered by this network. A first aspect is devoted to passive distributed seismic sources detection, classification and separation. We investigate a number of narrow and wide band signal analysis methods both in time and time-frequency domains for energy arrival detection and tracking, including time adaptive higher order statistics, e.g. like kurtosis, and multiband band-pass filtering, together with adaptive time-frequency transformation and extraction techniques. We demonstrate that these techniques provide superior resolution and robustness than classical STA/LTA techniques in particular in the case of distributed sources with potential signal

  5. 1-D seismic velocity model and hypocenter relocation using double difference method around West Papua region

    SciTech Connect

    Sabtaji, Agung E-mail: agung.sabtaji@bmkg.go.id; Nugraha, Andri Dian

    2015-04-24

    West Papua region has fairly high of seismicity activities due to tectonic setting and many inland faults. In addition, the region has a unique and complex tectonic conditions and this situation lead to high potency of seismic hazard in the region. The precise earthquake hypocenter location is very important, which could provide high quality of earthquake parameter information and the subsurface structure in this region to the society. We conducted 1-D P-wave velocity using earthquake data catalog from BMKG for April, 2009 up to March, 2014 around West Papua region. The obtained 1-D seismic velocity then was used as input for improving hypocenter location using double-difference method. The relocated hypocenter location shows fairly clearly the pattern of intraslab earthquake beneath New Guinea Trench (NGT). The relocated hypocenters related to the inland fault are also observed more focus in location around the fault.

  6. Comparison of smoothing methods for the development of a smoothed seismicity model for Alaska and the implications for seismic hazard

    USGS Publications Warehouse

    Moschetti, Morgan P.; Mueller, Charles S.; Boyd, Oliver S.; Petersen, Mark D.

    2014-01-01

    In anticipation of the update of the Alaska seismic hazard maps (ASHMs) by the U. S. Geological Survey, we report progress on the comparison of smoothed seismicity models developed using fixed and adaptive smoothing algorithms, and investigate the sensitivity of seismic hazard to the models. While fault-based sources, such as those for great earthquakes in the Alaska-Aleutian subduction zone and for the ~10 shallow crustal faults within Alaska, dominate the seismic hazard estimates for locations near to the sources, smoothed seismicity rates make important contributions to seismic hazard away from fault-based sources and where knowledge of recurrence and magnitude is not sufficient for use in hazard studies. Recent developments in adaptive smoothing methods and statistical tests for evaluating and comparing rate models prompt us to investigate the appropriateness of adaptive smoothing for the ASHMs. We develop smoothed seismicity models for Alaska using fixed and adaptive smoothing methods and compare the resulting models by calculating and evaluating the joint likelihood test. We use the earthquake catalog, and associated completeness levels, developed for the 2007 ASHM to produce fixed-bandwidth-smoothed models with smoothing distances varying from 10 to 100 km and adaptively smoothed models. Adaptive smoothing follows the method of Helmstetter et al. and defines a unique smoothing distance for each earthquake epicenter from the distance to the nth nearest neighbor. The consequence of the adaptive smoothing methods is to reduce smoothing distances, causing locally increased seismicity rates, where seismicity rates are high and to increase smoothing distances where seismicity is sparse. We follow guidance from previous studies to optimize the neighbor number (n-value) by comparing model likelihood values, which estimate the likelihood that the observed earthquake epicenters from the recent catalog are derived from the smoothed rate models. We compare likelihood

  7. Variation of the Earth tide-seismicity compliance parameter during the recent seismic activity of Fthiotida, Greece

    NASA Astrophysics Data System (ADS)

    Contadakis, Michael; Aarabelos, Dimitrios; Vergos, Georgios; Spatalas, Spyridon

    2014-05-01

    Applying the Hi(stogram)Cum(ulation) method, which was introduced recently by Cadicheanu, van Ruymbecke and Zhu (2007), we analyze the series of the earthquakes occurred in the last 50 years in seismic active areas of Greece, i.e. the areas (a) of the Mygdonian Basin(Contadakis et al. 2007), (b) of the Ionian Islands (Contadakis et al. 2012 ) and (c) of the Hellenic Arc (Vergos et al. 2012 ) . The result of the analysis for all the areas indicate that the monthly variation of the frequencies of earthquake occurrence is in accordance with the period of the tidal lunar monthly and semi-monthly (Mm and Mf) variations and the same happens with the corresponding daily variations of the frequencies of earthquake occurrence with the diurnal luni-solar (K1) and semidiurnal lunar (M2) tidal variations. In addition the confidence level for the identifiation of such period accordance between earthquakes occurrence frequency and tidal periods varies with seismic activity, i.e. the higher confidence level corresponds to periods with stronger seismic activity. These results are in favor of a tidal triggering process on earthquakes when the stress in the focal area is near the critical level. Based on these results, we consider the confidence level of earthquake occurrence - tidal period accordance, p, as an index of tectonic stress criticality for earthquake occurrence and we check on posterior if the variation of the confidence level index, p, indicate the fault matureness in the case of the recent seismic activity at Fthiotida, Greece. In this paper we present the results of this test. References Cadicheanu, N., van Ruymbeke, M andZhu P.,2007:Tidal triggering evidence of intermediate depth earthquakes in Vrancea zone(Romania), NHESS 7,733-740. Contadakis, M. E., Arabelos, D. N., Spatalas, S., 2009, Evidence for tidal triggering on the shallow earthquakes of the seismic area of Mygdonia basin, North Greece, in Terrestrial and Stellar Environment, eds.D. Arabelos, M

  8. Active Monitoring With The Use Of Seismic Vibrators: Experimental Systems And The Results Of Works

    NASA Astrophysics Data System (ADS)

    Kovalevsky, V.; Alekseev, A.; Glinsky, B.; Khairetdinov, M.; Seleznev, V.; Emanov, A.; Soloviev, V.

    2004-12-01

    Active methods of geophysical monitoring with the use of powerful seismic vibrators play an important role in the investigation of changes in the medium's stressed-deformed state in seismic prone zones for problems of seismic hazard prediction. In the last three decades, this scientific direction has been actively developed at institutes of Siberian Branch of Russian Academy of Sciences. In this period, experimental systems for the active monitoring of the medium, which include powerful vibrational sources with computer control systems, mobile specialized complexes for the precision recording of vibrational seismic signals, and data processing systems have been created. A review of various constructions of resonant vibrational seismic sources with a vibrational force of 100 tons in the frequency range from 5 to 15 Hz and the principles of creation of precision computer control systems and low-frequency three-component recording systems VIRS-M, VIRS-K, and ROSA is presented. A method for the active monitoring of the medium with the use of wideband sweep signals and narrow-band harmonic signals radiated by seismic vibrators has been developed. To determine the sensitivity of the active monitoring system, some experiments to detect the influence of the Earth's crust tidal deformations (of the order of 10-7) on seismic wave velocities have been performed. A 100-ton seismic vibrator and recording systems were located at a distance of 356 km. The radiation sessions of harmonic and sweep signals were repeated every 3 hours during 8 days. This made it possible to construct the time series of variations in the amplitudes and phases of the signals and wave arrival times. Both 12-hour and 24-hour periodicities correlated with the earth's tides were distinguished in the spectrum of variations of the recorded signals. The experiment has shown that the active monitoring system makes it possible to detect relative variations of the seismic wave velocities of the order of 10

  9. Primary component analysis method and reduction of seismicity parameters

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Ma, Qin-Zhong; Lin, Ming-Zhou; Wu, Geng-Feng; Wu, Shao-Chun

    2005-09-01

    In the paper, the primary component analysis is made using 8 seismicity parameters of earthquake frequency N (M l≥3.0), b-value, η-value, A(b)-value, Mf-value, Ac-value, C-value and D-value that reflect the characteristics of magnitude, time and space distribution of seismicity from different respects. By using the primary component analysis method, the synthesis parameter W reflecting the anomalous features of earthquake magnitude, time and space distribution can be gained. Generally, there is some relativity among the 8 parameters, but their variations are different in different periods. The earthquake prediction based on these parameters is not very well. However, the synthesis parameter W showed obvious anomalies before 13 earthquakes (M S≥5.8) occurred in North China, which indicates that the synthesis parameter W can reflect the anomalous characteristics of magnitude, time and space distribution of seismicity better. Other problems related to the conclusions drawn by the primary component analysis method are also discussed.

  10. Statistical methods for investigating quiescence and other temporal seismicity patterns

    USGS Publications Warehouse

    Matthews, M.V.; Reasenberg, P.A.

    1988-01-01

    We propose a statistical model and a technique for objective recognition of one of the most commonly cited seismicity patterns:microearthquake quiescence. We use a Poisson process model for seismicity and define a process with quiescence as one with a particular type of piece-wise constant intensity function. From this model, we derive a statistic for testing stationarity against a 'quiescence' alternative. The large-sample null distribution of this statistic is approximated from simulated distributions of appropriate functionals applied to Brownian bridge processes. We point out the restrictiveness of the particular model we propose and of the quiescence idea in general. The fact that there are many point processes which have neither constant nor quiescent rate functions underscores the need to test for and describe nonuniformity thoroughly. We advocate the use of the quiescence test in conjunction with various other tests for nonuniformity and with graphical methods such as density estimation. ideally these methods may promote accurate description of temporal seismicity distributions and useful characterizations of interesting patterns. ?? 1988 Birkha??user Verlag.

  11. Analysis of the seismic activity associated with the 2010 eruption of Merapi Volcano, Java

    NASA Astrophysics Data System (ADS)

    Budi-Santoso, Agus; Lesage, Philippe; Dwiyono, Sapari; Sumarti, Sri; Subandriyo; Surono; Jousset, Philippe; Metaxian, Jean-Philippe

    2013-07-01

    The 2010 eruption of Merapi is the first large explosive eruption of the volcano that has been instrumentally observed. The main characteristics of the seismic activity during the pre-eruptive period and the crisis are presented and interpreted in this paper. The first seismic precursors were a series of four shallow swarms during the period between 12 and 4 months before the eruption. These swarms are interpreted as the result of perturbations of the hydrothermal system by increasing heat flow. Shorter-term and more continuous precursory seismic activity started about 6 weeks before the initial explosion on 26 October 2010. During this period, the rate of seismicity increased almost constantly yielding a cumulative seismic energy release for volcano-tectonic (VT) and multiphase events (MP) of 7.5 × 1010 J. This value is 3 times the maximum energy release preceding previous effusive eruptions of Merapi. The high level reached and the accelerated behavior of both the deformation of the summit and the seismic activity are distinct features of the 2010 eruption. The hypocenters of VT events in 2010 occur in two clusters at of 2.5 to 5 km and less than 1.5 km depths below the summit. An aseismic zone was detected at 1.5-2.5 km depth, consistent with studies of previous eruptions, and indicating that this is a robust feature of Merapi's subsurface structure. Our analysis suggests that the aseismic zone is a poorly consolidated layer of altered material within the volcano. Deep VT events occurred mainly before 17 October 2010; subsequent to that time shallow activity strongly increased. The deep seismic activity is interpreted as associated with the enlargement of a narrow conduit by an unusually large volume of rapidly ascending magma. The shallow seismicity is interpreted as recording the final magma ascent and the rupture of a summit-dome plug, which triggered the eruption on 26 October 2010. Hindsight forecasting of the occurrence time of the eruption is performed

  12. Full waveform seismic tomography of the Vrancea region using the adjoint method

    NASA Astrophysics Data System (ADS)

    Baron, J.; Danecek, P.; Morelli, A.; Tondi, R.

    2013-12-01

    The Vrancea region, at the south-eastern bend of the Carpathian Mountains, Romania, represents one of the most particular seismically active zones of Europe. Beside some shallow crustal seismicity spread across the whole Romanian territory, Vrancea is the place of intense seismicity with the presence of a cluster of intermediate-depth foci placed in a narrow NE-SW trending volume below 60km depth. The occurrence of strong earthquakes in the past has raised questions about the nature of this deep intra-continental seismicity and increased the interest in the geodynamics of this earthquake-prone area. The central issue for seismic risk assessment is whether this singular seismogenic volume is geodynamically coupled to the crust. Large-scale mantle seismic tomographic studies have revealed the presence of a narrow, almost vertical, high-velocity body in the upper mantle. So far, two main different geodynamical models have been proposed for the region: (1) A subduction-related process, and (2) more recently a delamination process. High-resolution seismic tomography could help to reveal more details in the subcrustal structural models and to constrain the properties of the Vrancea Seismogenic Zone. Previous efforts have relied on classical ray-theoretical travel-time tomography to model data from local permanent or temporary instruments. Recent developments in computational seismology as well as the availability of parallel computing now allow modelling of the entire seismogram in a consistent way. This enables us to potentially retrieve more information out of seismic waveforms and to keep the modelling more uniform. In this work we want to assess the information gain that can be obtained using an adjoint-based inversion scheme combined with a full 3D waveform modelling, with respect to ray theory based tomography for the Vrancea region. The study is done with a dataset of local earthquakes from the broadband data of the CALIXTO 1999 experiment. This dataset is

  13. Evaluation of Seismic Methods for Inferring Fluid Migration in Volcanic Regions

    NASA Astrophysics Data System (ADS)

    Lucero, Jaron Joshua James

    The classic concepts of fluid transport derived for sedimentary environments are generally not applicable to the study of magmatic transport. High fluid viscosity and negligible rock permeability should preclude magma transport, yet dikes, sills, and other intrusive features are commonly observed. Relationships between intrusive units and regional paleo-stress fields are well described, but the dynamic interactions between igneous fluid and competent rock that ultimately produce magma intrusions are not. Elevated seismicity is often observed in conjunction with volcanic activity, and is generally thought to indicate magmatic intrusion. This study examined the unique information that seismic data can provide about magmatic processes as they occur. Specifically, methods for deriving transport volume from fluid induced seismicity were evaluated. An approach proposed by Herbert Shaw linked total scalar seismic moment release and source region volume distortion. This relationship was tested using data from various fluid injection experiments by comparing observed seismicity with injected fluid volume. A second method examined seismic events from an earthquake swarm near the Yellowstone caldera for evidence of tensile-crack source mechanisms, which couldindicate igneous intrusion. Similar investigations have been successfully conducted using larger magnitude events. The Yellowstone swarm events were too small for traditional approaches, but were appropriately sized to assess the suitability of a different inversion technique for characterizing smaller events. A technique for improving the quality of the seismic dataset is also discussed. After further development, the techniques described may provide additional constraints on rates of active magma transport in volcanic areas. The results obtained by this study were generally consistent with predictions of the McGarr-Shaw method, and have illuminated the additional considerations that must be addressed when testing the

  14. Seismic Evidence for an Active Southern Rio Grande Rift

    NASA Astrophysics Data System (ADS)

    Thompson, L. E.; Velasco, A. A.

    2010-12-01

    Competing models exist to explain what caused the Earth’s crust to spread apart 29 million years ago to create a region known today as the Rio Grande Rift (RGR). The RGR extends from central Colorado through New Mexico to northern Mexico, near El Paso. A growing body of evidence shows that geologic activity still occurs in the RGR, with a continuation of faulting, seismicity and a small widening rate. We map of the seismic velocity structure and crustal thickness using data from the Rio Grande Rift Seismic TRAnsect (RISTRA) experiment and the EarthScope Transportable Array (USArray) dataset. In addition to the data we collected from the RISTRA experiment and USArray dataset, we also acquired receiver functions from the EarthScope Automatic Receiver Survey (EARS) website (http://www.earthscope.org/data) and waveform data from the Incorporated Research Institutes for Seismology (IRIS) Data Management Center (DMC). In particular, we requested seismograms from the IRIS DMC database where we acquired teleseismic events from Jan 2000 to Dec 2009. This includes 7,259 seismic events with a minimum magnitude of 5.5 and 106,389 continuous waveforms. This data was preprocessed (merged, rotated) using a program called Standing Order of Data (SOD). We computed receiver functions and receiver function stacks for all data in the Southern Rio Grande Rift (SRGR). We map the crustal thickness, seismic velocity, and mantle structure to better determine the nature of tectonic activity that is presently taking place and further investigate the regional extension of the Southern Rio Grande Rift (SRGR). Here we present results of the crustal and velocity structure using the kriging interpolation scheme and interpret our results in relation to southern RGR deformation and extension.

  15. New inferences from spectral seismic energy measurement of a link between regional seismicity and volcanic activity at Mt. Etna, Italy

    NASA Astrophysics Data System (ADS)

    Ortiz, R.; Falsaperla, S.; Marrero, J. M.; Messina, A.

    2009-04-01

    The existence of a relationship between regional seismicity and changes in volcanic activity has been the subject of several studies in the last years. Generally, activity in basaltic volcanoes such as Villarica (Chile) and Tungurahua (Ecuador) shows very little changes after the occurrence of regional earthquakes. In a few cases volcanic activity has changed before the occurrence of regional earthquakes, such as observed at Teide, Tenerife, in 2004 and 2005 (Tárraga et al., 2006). In this paper we explore the possible link between regional seismicity and changes in volcanic activity at Mt. Etna in 2006 and 2007. On 24 November, 2006 at 4:37:40 GMT an earthquake of magnitude 4.7 stroke the eastern coast of Sicily. The epicenter was localized 50 km SE of the south coast of the island, and at about 160 km from the summit craters of Mt. Etna. The SSEM (Spectral Seismic Energy Measurement) of the seismic signal at stations at 1 km and 6 km from the craters highlights that four hours before this earthquake the energy associated with volcanic tremor increased, reached a maximum, and finally became steady when the earthquake occurred. Conversely, neither before nor after the earthquake, the SSEM of stations located between 80 km and 120 km from the epicentre and outside the volcano edifice showed changes. On 5 September, 2007 at 21:24:13 GMT an earthquake of magnitude 3.2 and 7.9 km depth stroke the Lipari Island, at the north of Sicily. About 38 hours before the earthquake occurrence, there was an episode of lava fountain lasting 20 hours at Etna volcano. The SSEM of the seismic signal recorded during the lava fountain at a station located at 6 km from the craters highlights changes heralding this earthquake ten hours before its occurrence using the FFM method (e.g., Voight, 1988; Ortiz et al., 2003). A change in volcanic activity - with the onset of ash emission and Strombolian explosions - was observed a couple of hours before the occurrence of the regional

  16. Structure and seismic activity of the Lesser Antilles subduction zone

    NASA Astrophysics Data System (ADS)

    Evain, M.; Galve, A.; Charvis, P.; Laigle, M.; Ruiz Fernandez, M.; Kopp, H.; Hirn, A.; Flueh, E. R.; Thales Scientific Party

    2011-12-01

    Several active and passive seismic experiments conducted in 2007 in the framework of the European program "Thales Was Right" and of the French ANR program "Subsismanti" provided a unique set of geophysical data highlighting the deep structure of the central part of the Lesser Antilles subduction zone, offshore Dominica and Martinique, and its seismic activity during a period of 8 months. The region is characterized by a relatively low rate of seismicity that is often attributed to the slow (2 cm/yr) subduction of the old, 90 My, Atlantic lithosphere beneath the Caribbean Plate. Based on tomographic inversion of wide-angle seismic data, the forearc can clearly be divided into an inner forearc, characterised by a high vertical velocity gradient in the igneous crust, and an outer forearc with lower crustal velocity gradient. The thick, high velocity, inner forearc is possibly the extension at depth of the Mesozoic Caribbean crust outcropping in La Désirade Island. The outer forearc, up to 70 km wide in the northern part of the study area, is getting narrower to the south and disappears offshore Martinique. Based on its seismic velocity structure with velocities higher than 6 km/s the backstop consists, at least partly, of magmatic rocks. The outer forearc is also highly deformed and faulted within the subducting trend of the Tiburon Ridge. With respect to the inner forearc velocity structure the outer forearc basement could either correspond to an accreted oceanic terrane or made of highly fractured rocks. The inner forearc is a dense, poorly deformable crustal block, tilted southward as a whole. It acts as a rigid buttress increasing the strain within both the overriding and subducting plates. This appears clearly in the current local seismicity affecting the subducting and the overriding plates that is located beneath the inner forearc. We detected earthquakes beneath the Caribbean forearc and in the Atlantic oceanic plate as well. The main seismic activity is

  17. A fast-convergence POCS seismic denoising and reconstruction method

    NASA Astrophysics Data System (ADS)

    Ge, Zi-Jian; Li, Jing-Ye; Pan, Shu-Lin; Chen, Xiao-Hong

    2015-06-01

    The efficiency, precision, and denoising capabilities of reconstruction algorithms are critical to seismic data processing. Based on the Fourier-domain projection onto convex sets (POCS) algorithm, we propose an inversely proportional threshold model that defines the optimum threshold, in which the descent rate is larger than in the exponential threshold in the large-coefficient section and slower than in the exponential threshold in the small-coefficient section. Thus, the computation efficiency of the POCS seismic reconstruction greatly improves without affecting the reconstructed precision of weak reflections. To improve the flexibility of the inversely proportional threshold, we obtain the optimal threshold by using an adjustable dependent variable in the denominator of the inversely proportional threshold model. For random noise attenuation by completing the missing traces in seismic data reconstruction, we present a weighted reinsertion strategy based on the data-driven model that can be obtained by using the percentage of the data-driven threshold in each iteration in the threshold section. We apply the proposed POCS reconstruction method to 3D synthetic and field data. The results suggest that the inversely proportional threshold model improves the computational efficiency and precision compared with the traditional threshold models; furthermore, the proposed reinserting weight strategy increases the SNR of the reconstructed data.

  18. Multiple Seismic Array Observations for Tracing Deep Tremor Activity in Western Shikoku, Japan

    NASA Astrophysics Data System (ADS)

    Takeda, T.; Matsuzawa, T.; Shiomi, K.; Obara, K.

    2011-12-01

    Deep non-volcanic tremors become very active during episodic slow-slip events in western Japan and Cascadia. The episodic tremor and slow-slip events in western Shikoku, Japan, occur at a typical interval of 6 months. Recently, it has been reported that tremor migration activity is complex and shows different migrating directions depending on time scales (Ghosh et al., 2010). Such characteristics of tremor are important to understand the mechanism of tremor and the relationship between tremor and SSEs. However it is difficult to determine the location of tremors with high accuracy because tremors show faint signals and make the identification of P/S-wave arrivals difficult. Seismic array analysis is useful to evaluate tremor activity, especially to estimate the arrival direction of seismic energy (e.g. Ueno et al., 2010, Ghosh et al., 2010), as it can distinguish multiple tremor sources occurring simultaneously. Here, we have conducted seismic array observation and analyzed seismic data during tremor activity by applying the MUSIC method to trace tremor location and its migration in western Shikoku. We have installed five seismic arrays in western Shikoku since January 2011. One of the arrays contains 30 stations with 3-component seismometers with a natural frequency of 2 Hz (Type-L array). The array aperture size is 2 km and the mean interval between stations is approximately 200 m. Each of the other arrays (Type-S array) contains 9 seismic stations with the same type of seismometers of the Type-L array, and is deployed surrounding the Type-L array. The small array aperture size is 800 m and its mean station interval is approximately 150 m. All array stations have recorded continuous waveform data at a sampling of 200Hz. In May 2011, an episodic tremor and a short-term slip event occurred for the first time during the observation period. We could retrieve the array seismic data during the whole tremor episode. The analysis of data from the type-L array confirms

  19. Noise-based body-wave seismic tomography in an active underground mine.

    NASA Astrophysics Data System (ADS)

    Olivier, G.; Brenguier, F.; Campillo, M.; Lynch, R.; Roux, P.

    2014-12-01

    Over the last decade, ambient noise tomography has become increasingly popular to image the earth's upper crust. The seismic noise recorded in the earth's crust is dominated by surface waves emanating from the interaction of the ocean with the solid earth. These surface waves are low frequency in nature ( < 1 Hz) and not usable for imaging smaller structures associated with mining or oil and gas applications. The seismic noise recorded at higher frequencies are typically from anthropogenic sources, which are short lived, spatially unstable and not well suited for constructing seismic Green's functions between sensors with conventional cross-correlation methods. To examine the use of ambient noise tomography for smaller scale applications, continuous data were recorded for 5 months in an active underground mine in Sweden located more than 1km below surface with 18 high frequency seismic sensors. A wide variety of broadband (10 - 3000 Hz) seismic noise sources are present in an active underground mine ranging from drilling, scraping, trucks, ore crushers and ventilation fans. Some of these sources generate favorable seismic noise, while others are peaked in frequency and not usable. In this presentation, I will show that the noise generated by mining activity can be useful if periods of seismic noise are carefully selected. Although noise sources are not temporally stable and not evenly distributed around the sensor array, good estimates of the seismic Green's functions between sensors can be retrieved for a broad frequency range (20 - 400 Hz) when a selective stacking scheme is used. For frequencies below 100 Hz, the reconstructed Green's functions show clear body-wave arrivals for almost all of the 153 sensor pairs. The arrival times of these body-waves are picked and used to image the local velocity structure. The resulting 3-dimensional image shows a high velocity structure that overlaps with a known ore-body. The material properties of the ore-body differ from

  20. Reversible rigid coupling apparatus and method for borehole seismic transducers

    SciTech Connect

    Owen, T.E.; Parra, J.O.

    1992-01-14

    This patent describes a seismic detector for high resolution reverse vertical seismic profile measurements when placed in a shallow borehole in a geological formation of interest that contains a seismic source and connected to a seismograph. It comprises a framework; accelerometer sensors for X, Y, and Z axis, means for electrically connecting the accelerometers to the seismograph to record seismic waves received by the accelerometer sensors form the seismic source; heating elements secured to, but electrically insulated from, the framework; power means for supplying power to the heating elements; and meltable substance encapsulating the seismic detector.

  1. Seismic Activity in the Gulf of Mexico: a Preliminary Analysis

    NASA Astrophysics Data System (ADS)

    Franco, S. I.; Canet, C.; Iglesias, A.; Valdes-Gonzales, C. M.

    2013-05-01

    The southwestern corner of Gulf of Mexico (around the northern Isthmus of Tehuantepec) is exposed to an intense deep (> 100 km) seismic activity caused by the subduction of the Cocos plate. Aside from this, the gulf has been considered as a zone of low or no-seismicity. However, a sparse shallow seismic activity is observed across the Gulf of Mexico; some of these earthquakes have been strongly felt (e.g. 23/05/2007 and 10/09/2006), and the Jaltipan, 1959 earthquake caused fatalities and severe destruction in central and southern Veracruz. In this work we analyze 5 relevant earthquakes that occurred since 2001. At the central Gulf of Mexico focal mechanisms show inverse faults oriented approximately NW-SE with dip near 45 degrees, suggesting a link to sediment loading and/or to salt tectonics. On the other hand, in the southwestern corner of the gulf we analyzed some clear examples of strike-slip faults and activity probably related to the Veracruz Fault. One anomalous earthquake, recorded in 2007 in the western margin of the gulf, shows a strike-slip mechanism indicating a transform regime probably related with the East Mexican Fault. The recent improvement of the Mexican Seismological broadband network have allowed to record small earthquakes distributed in and around the Gulf of Mexico. Although the intermediate and large earthquakes in the region are infrequent, the historic evidence indicates that the magnitudes could reach Mw~6.4. This fact could be taken in consideration to reassess the seismic hazard for oil and industrial infrastructure in the region.

  2. Probing the Detailed Seismic Velocity Structure of Subduction Zones Using Advanced Seismic Tomography Methods

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Thurber, C. H.

    2005-12-01

    Subduction zones are one of the most important components of the Earth's plate tectonic system. Knowing the detailed seismic velocity structure within and around subducting slabs is vital to understand the constitution of the slab, the cause of intermediate depth earthquakes inside the slab, the fluid distribution and recycling, and tremor occurrence [Hacker et al., 2001; Obara, 2002].Thanks to the ability of double-difference tomography [Zhang and Thurber, 2003] to resolve the fine-scale structure near the source region and the favorable seismicity distribution inside many subducting slabs, it is now possible to characterize the fine details of the velocity structure and earthquake locations inside the slab, as shown in the study of the Japan subduction zone [Zhang et al., 2004]. We further develop the double-difference tomography method in two aspects: the first improvement is to use an adaptive inversion mesh rather than a regular inversion grid and the second improvement is to determine a reliable Vp/Vs structure using various strategies rather than directly from Vp and Vs [see our abstract ``Strategies to solve for a better Vp/Vs model using P and S arrival time'' at Session T29]. The adaptive mesh seismic tomography method is based on tetrahedral diagrams and can automatically adjust the inversion mesh according to the ray distribution so that the inversion mesh nodes are denser where there are more rays and vice versa [Zhang and Thurber, 2005]. As a result, the number of inversion mesh nodes is greatly reduced compared to a regular inversion grid with comparable spatial resolution, and the tomographic system is more stable and better conditioned. This improvement is quite valuable for characterizing the fine structure of the subduction zone considering the highly uneven distribution of earthquakes within and around the subducting slab. The second improvement, to determine a reliable Vp/Vs model, lies in jointly inverting Vp, Vs, and Vp/Vs using P, S, and S

  3. Study of Seismic Activity Using Geophysical and Radio Physical Equipment for Observation

    NASA Astrophysics Data System (ADS)

    Kvavadze, N.; Tsereteli, N. S.

    2015-12-01

    One of the most dangerous and destructive natural hazards are earthquakes, which is confirmed by recent earthquakes such as Nepal 2015, Japan and Turkey 2011. Because of this, study of seismic activity is important. Studying any process, it is necessary to use different methods of observation, which allows us to increase accuracy of obtained data. Seismic activity is a complex problem and its study needs different types of observation methods. Two main problems of seismic activity study are: reliable instrumental observations and earthquake short-term predictions. In case of seismic risks it is necessary to have reliable accelerometer data. One of the most promising field in earthquake short-term prediction is very low frequency (VLF) electromagnetic wave propagation in ionosphere observation. To study Seismic activity of Caucasus region, was created observation complex using Accelerometer, Velocimeter and VLF electromagnetic waves received from communication stations (located in different area of the world) reflected from low ionosphere. System is created and operates at Tbilisi State University Ionosphere Observatory, near Tbilisi in Tabakhmela 42.41'70 N, 44.80'92 E, Georgia. Data obtained is sent to a local server located at M. Nodia Institute of Geophysics, TSU, for storage and processing. Diagram for complex is presented. Also data analysis methods were created and preliminary processing was done. In this paper we present some of the results: Earthquake data from ionosphere observations as well as local earthquakes recorded with accelerometer and velocimeter. Complex is first in 6 that will be placed around Georgia this year. We plan on widening network every year.

  4. Seismic image of a CO2 reservoir beneath a seismically active volcano

    USGS Publications Warehouse

    Julian, B.R.; Pitt, A.M.; Foulger, G.R.

    1998-01-01

    Mammoth Mountain is a seismically active volcano 200 000 to 50 000 years old, situated on the southwestern rim of Long Valley caldera, California. Since 1989 it has shown evidence of unrest in the form of earthquake swarms (Hill et al. 1990), volcanic 'long-period' earthquakes (Pitt and Hill 1994), increased output of magmatic 3He (Sorey et al. 1993) and the emission of about 500 tonnes day-1 of CO2 (Farrar et al. 1995; Hill 1996; M. Sorey, personal communication, 1997) which has killed trees and poses a threat to human safety. Local-earthquake tomography shows that in mid-1989 areas of subsequent tree-kill were underlain by extensive regions where the ratio of the compressional and shear elastic-wave speeds Vp/VS was about 9% lower than in the surrounding rocks. Theory (Mavko and Mukerji 1995), experiment (Ito, DeVilbiss and Nur 1979) and experience at other geothermal/volcanic areas (Julian et al. 1996) and at petroleum reservoirs (Harris et al. 1996) indicate that Vp/VS is sensitive to pore-fluid compressibility, through its effect on Vp. The observed Vp/VS anomaly is probably caused directly by CO2, and seismic Vp/VS tomography is thus a promising tool for monitoring gas concentration and movement in volcanoes, which may in turn be related to volcanic activity.

  5. Seismic image of a CO2 reservoir beneath a seismically active volcano

    NASA Astrophysics Data System (ADS)

    Julian, Bruce R; Pitt, A. M.; Foulger, G. R.

    1998-04-01

    Mammoth Mountain is a seismically active volcano 200000 to 50000 years old, situated on the southwestern rim of Long Valley caldera, California. Since 1989 it has shown evidence of unrest in the form of earthquake swarms (Hill et al. 1990), volcanic `long-period' earthquakes (Pitt & Hill 1994), increased output of magmatic 3He (Sorey et al. 1993) and the emission of about 500 tonnes day -1 of CO2 (Farrar et al. 1995; Hill 1996; M. Sorey, personal communication, 1997), which has killed trees and poses a threat to human safety. Local-earthquake tomography shows that in mid-1989 areas of subsequent tree-kill were underlain by extensive regions where the ratio of the compressional and shear elastic-wave speeds VP/VS was about 9 per cent lower than in the surrounding rocks. Theory (Mavko & Mukerji 1995), experiment (Ito, DeVilbiss & Nur 1979), and experience at other geothermal/volcanic areas (Julian et al. 1996) and at petroleum reservoirs (Harris et al. 1996) indicate that VP/VS is sensitive to pore-fluid compressibility, through its effect on VP . The observed VP/VS anomaly is probably caused directly by CO2, and seismic VP/VS tomography is thus a promising tool for monitoring gas concentration and movement in volcanoes, which may in turn be related to volcanic activity.

  6. Seismic Response Control Of Structures Using Semi-Active and Passive Variable Stiffness Devices

    NASA Astrophysics Data System (ADS)

    Salem, Mohamed M. A.

    Controllable devices such as Magneto-Rheological Fluid Dampers, Electro-Rheological Dampers, and controllable friction devices have been studied extensively with limited implementation in real structures. Such devices have shown great potential in reducing seismic demands, either as smart base isolation systems, or as smart devices for multistory structures. Although variable stiffness devices can be used for seismic control of structures, the vast majority of research effort has been given to the control of damping. The primary focus of this dissertation is to evaluate the seismic control of structures using semi-active and passive variable stiffness characteristics. Smart base isolation systems employing variable stiffness devices have been studied, and two semi-active control strategies are proposed. The control algorithms were designed to reduce the superstructure and base accelerations of seismically isolated structures subject to near-fault and far-field ground motions. Computational simulations of the proposed control algorithms on the benchmark structure have shown that excessive base displacements associated with the near-fault ground motions may be better mitigated with the use of variable stiffness devices. However, the device properties must be controllable to produce a wide range of stiffness changes for an effective control of the base displacements. The potential of controllable stiffness devices in limiting the base displacement due to near-fault excitation without compromising the performance of conventionally isolated structures, is illustrated. The application of passive variable stiffness devices for seismic response mitigation of multistory structures is also investigated. A stiffening bracing system (SBS) is proposed to replace the conventional bracing systems of braced frames. An optimization process for the SBS parameters has been developed. The main objective of the design process is to maintain a uniform inter-story drift angle over the

  7. Identifying induced seismicity in active tectonic regions: A case study of the San Joaquin Basin, California

    NASA Astrophysics Data System (ADS)

    Aminzadeh, F.; Göbel, T.

    2013-12-01

    Understanding the connection between petroleum-industry activities, and seismic event occurrences is essential to monitor, quantify, and mitigate seismic risk. While many studies identified anthropogenically-induced seismicity in intraplate regions where background seismicity rates are generally low, little is known about how to distinguish naturally occurring from induced seismicity in active tectonic regions. Further, it is not clear how different oil and gas operational parameters impact the frequency and magnitude of the induced seismic events. Here, we examine variations in frequency-size and spatial distributions of seismicity within the Southern Joaquin basin, an area of both active petroleum production and active fault systems. We analyze a newly available, high-quality, relocated earthquake catalog (Hauksson et al. 2012). This catalog includes many seismic events with magnitudes up to M = 4.5 within the study area. We start by analyzing the overall quality and consistence of the seismic catalog, focusing on temporal variations in seismicity rates and catalog completeness which could indicate variations in network sensitivity. This catalog provides relatively homogeneous earthquake recordings after 1981, enabling us to compare seismicity rates before and after the beginning of more pervasive petroleum-industry activities, for example, hydraulic-fracturing and waste-water disposals. We conduct a limited study of waste-water disposal wells to establish a correlation between seismicity statistics (i.e. rate changes, fractal dimension, b-value) within specific regions and anthropogenic influences. We then perform a regional study, to investigate spatial variations in seismicity statistics which are then correlated to oil field locations and well densities. In order to distinguish, predominantly natural seismicity from induced seismicity, we perform a spatial mapping of b-values and fractal dimensions of earthquake hypocenters. Seismic events in the proximity to

  8. Seismic activity of Tokyo area and Philippine Sea plate under Japanese Islands

    NASA Astrophysics Data System (ADS)

    Sakai, S.; Nakagawa, S.; Nanjo, K.; Kasahara, K.; Panayotopoulos, Y.; Tsuruoka, H.; Kurashimo, E.; Obara, K.; Hirata, N.; Kimura, H.; Honda, R.

    2012-12-01

    The Japanese government has estimated the probability of earthquake occurrence with magnitude 7-class during the next 30 years as 70 %. This estimation is based on five earthquakes that occurred in this area in the late 120 years. However, it has been revealed that this region is lying on more complicated tectonic condition due to the two subducted plates and the various types of earthquakes which have been caused by. Therefore, it is necessary to classify these earthquakes into inter-plate earthquakes and intra-plate ones. Then, we have been constructing a seismic observation network since 5 years ago. Tokyo Metropolitan area is a densely populated region of about 40 million people. It is the center of Japan both in politics and in economy. So that human activities have been conducting quite busily, this region is unsuitable for seismic observation. Then, we have decided to make an ultra high dense seismic observation network. We named it the Metropolitan Seismometer Observation Network; MeSO-net. MeSO-net consists of 296 seismic stations. Minimum interval is about 2km and average interval is about 5km.We picked the P- and S-wave arrival times manually. We applied double-difference tomography method to the dataset and estimated the velocity structure. We depicted the plate boundaries from the newly developed velocity model. And, we referred to the locations of the repeating earthquakes, the distributions of normal hypocenters and the focal mechanisms. Our plate model became relatively flat and a little shallower than previous one.Seismicity of Metropolitan area after the M9 event was compared to the one before M9 event. The seismic activity is about 4 times as high as before the M9 event occurred. We examined spatial distribution of the activated seismicity with respect to the newly developed plate configuration. The activated events are located on upper boundaries and they have almost thrust type mechanisms. Recently, a slow slip event has occurred on October in

  9. Seismic Methods of Identifying Explosions and Estimating Their Yield

    NASA Astrophysics Data System (ADS)

    Walter, W. R.; Ford, S. R.; Pasyanos, M.; Pyle, M. L.; Myers, S. C.; Mellors, R. J.; Pitarka, A.; Rodgers, A. J.; Hauk, T. F.

    2014-12-01

    Seismology plays a key national security role in detecting, locating, identifying and determining the yield of explosions from a variety of causes, including accidents, terrorist attacks and nuclear testing treaty violations (e.g. Koper et al., 2003, 1999; Walter et al. 1995). A collection of mainly empirical forensic techniques has been successfully developed over many years to obtain source information on explosions from their seismic signatures (e.g. Bowers and Selby, 2009). However a lesson from the three DPRK declared nuclear explosions since 2006, is that our historic collection of data may not be representative of future nuclear test signatures (e.g. Selby et al., 2012). To have confidence in identifying future explosions amongst the background of other seismic signals, and accurately estimate their yield, we need to put our empirical methods on a firmer physical footing. Goals of current research are to improve our physical understanding of the mechanisms of explosion generation of S- and surface-waves, and to advance our ability to numerically model and predict them. As part of that process we are re-examining regional seismic data from a variety of nuclear test sites including the DPRK and the former Nevada Test Site (now the Nevada National Security Site (NNSS)). Newer relative location and amplitude techniques can be employed to better quantify differences between explosions and used to understand those differences in term of depth, media and other properties. We are also making use of the Source Physics Experiments (SPE) at NNSS. The SPE chemical explosions are explicitly designed to improve our understanding of emplacement and source material effects on the generation of shear and surface waves (e.g. Snelson et al., 2013). Finally we are also exploring the value of combining seismic information with other technologies including acoustic and InSAR techniques to better understand the source characteristics. Our goal is to improve our explosion models

  10. Seismic Spatial Autocorrelation as a Technique to Track Changes in the Permafrost Active Layer

    NASA Astrophysics Data System (ADS)

    Abbott, R. E.

    2013-12-01

    We present preliminary results from an effort to continuously track freezing and thawing of the permafrost active layer using a small-aperture seismic array. The 7-element array of three-component posthole seismometers is installed on permafrost at Poker Flat Research Range, near Fairbanks, Alaska. The array is configured in two three-station circles with 75 and 25 meter radii that share a common center station. This configuration is designed to resolve omnidirectional, high-frequency seismic microtremor (i.e. ambient noise). Microtremor is continuously monitored and the data are processed using the spatial autocorrelation (SPAC) method. The resulting SPAC coefficients are then inverted for shear-wave velocity structure versus depth. Thawed active-layer soils have a much slower seismic velocity than frozen soils, allowing us to track the depth and intensity of thawing. Persistent monitoring on a permanent array would allow for a way to investigate year-to-year changes without costly site visits. Results from the seismic array will compared to, and correlated with, other measurement techniques, such as physical probing and remote sensing methods. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  11. ADVANCED SEISMIC BASE ISOLATION METHODS FOR MODULAR REACTORS

    SciTech Connect

    E. Blanford; E. Keldrauk; M. Laufer; M. Mieler; J. Wei; B. Stojadinovic; P.F. Peterson

    2010-09-20

    Advanced technologies for structural design and construction have the potential for major impact not only on nuclear power plant construction time and cost, but also on the design process and on the safety, security and reliability of next generation of nuclear power plants. In future Generation IV (Gen IV) reactors, structural and seismic design should be much more closely integrated with the design of nuclear and industrial safety systems, physical security systems, and international safeguards systems. Overall reliability will be increased, through the use of replaceable and modular equipment, and through design to facilitate on-line monitoring, in-service inspection, maintenance, replacement, and decommissioning. Economics will also receive high design priority, through integrated engineering efforts to optimize building arrangements to minimize building heights and footprints. Finally, the licensing approach will be transformed by becoming increasingly performance based and technology neutral, using best-estimate simulation methods with uncertainty and margin quantification. In this context, two structural engineering technologies, seismic base isolation and modular steel-plate/concrete composite structural walls, are investigated. These technologies have major potential to (1) enable standardized reactor designs to be deployed across a wider range of sites, (2) reduce the impact of uncertainties related to site-specific seismic conditions, and (3) alleviate reactor equipment qualification requirements. For Gen IV reactors the potential for deliberate crashes of large aircraft must also be considered in design. This report concludes that base-isolated structures should be decoupled from the reactor external event exclusion system. As an example, a scoping analysis is performed for a rectangular, decoupled external event shell designed as a grillage. This report also reviews modular construction technology, particularly steel-plate/concrete construction using

  12. Searching for Seismically Active Faults in the Gulf of Cadiz

    NASA Astrophysics Data System (ADS)

    Custodio, S.; Antunes, V.; Arroucau, P.

    2015-12-01

    The repeated occurrence of large magnitude earthquakes in southwest Iberia in historical and instrumental times suggests the presence of active fault segments in the region. However, due to an apparently diffuse seismicity pattern defining a broad region of distributed deformation west of Gibraltar Strait, the question of the location, dimension and geometry of such structures is still open to debate. We recently developed a new algorithm for earthquake location in 3D complex media with laterally varying interface depths, which allowed us to relocate 2363 events having occurred from 2007 to 2013, using P- and S-wave catalog arrival times obtained from the Portuguese Meteorological Institute (IPMA, Instituto Portugues do Mar e da Atmosfera), for a study area lying between 8.5˚W and 5˚W in longitude and 36˚ and 37.5˚ in latitude. The most remarkable change in the seismicity pattern after relocation is an apparent concentration of events, in the North of the Gulf of Cadiz, along a low angle northward-dipping plane rooted at the base of the crust, which could indicate the presence of a major fault. If confirmed, this would be the first structure clearly illuminated by seismicity in a region that has unleashed large magnitude earthquakes. Here, we present results from the joint analysis of focal mechanism solutions and waveform similarity between neighboring events from waveform cross-correlation in order to assess whether those earthquakes occur on the same fault plane.

  13. Studies of the Correlation Between Ionospheric Anomalies and Seismic Activities in the Indian Subcontinent

    SciTech Connect

    Sasmal, S.; Chakrabarti, S. K.; Chakrabarti, S.

    2010-10-20

    The VLF (Very Low Frequency) signals are long thought to give away important information about the Lithosphere-Ionosphere coupling. It is recently established that the ionosphere may be perturbed due to seismic activities. The effects of this perturbation can be detected through the VLF wave amplitude. There are several methods to find this correlations and these methods can be used for the prediction of these seismic events. In this paper, first we present a brief history of the use of VLF propagation method for the study of seismo-ionospheric correlations. Then we present different methods proposed by us to find out the seismo-ionospheric correlations. At the Indian Centre for Space Physics, Kolkata we have been monitoring the VTX station at Vijayanarayanam from 2002. In the initial stage, we received 17 kHz signal and latter we received 18.2 kHz signal. In this paper, first we present the results for the 17 kHz signal during Sumatra earthquake in 2004 obtained from the terminator time analysis method. Then we present much detailed and statistical analysis using some new methods and present the results for 18.2 kHz signal. In order to establish the correlation between the ionospheric activities and the earthquakes, we need to understand what are the reference signals throughout the year. We present the result of the sunrise and sunset terminators for the 18.2 kHz signal as a function of the day of the year for a period of four years, viz, 2005 to 2008 when the solar activity was very low. In this case, the signal would primarily be affected by the Sun due to normal sunrise and sunset effects. Any deviation from this standardized calibration curve would point to influences by terrestrial (such as earthquakes) and extra-terrestrial (such as solar activities and other high energy phenomena). We present examples of deviations which occur in a period of sixteen months and show that the correlations with seismic events is significant and typically the highest deviation

  14. Variation of the Earth tide-seismicity compliance parameter during the recent seismic activity in Fthiotida, central Greece

    NASA Astrophysics Data System (ADS)

    Arabelos, Dimitrios N.; Contadakis, Michael E.; Vergos, Georgios; Spatalas, Spyrous

    2016-01-01

    Based on the results of our previous studies concerning the tidal triggering effect on the seismicity in Greece, we consider the confidence level of earthquake occurrence - tidal period accordance as an index of tectonic stress criticality, associated with earthquake occurrence. Then, we investigate whether the recent increase in the seismic activity at Fthiotida in Greek mainland indicates faulting maturity and the possible production a stronger earthquake. In this paper we present the results of this investigation

  15. Quick seismic intensity map investigation and evaluation based on cloud monitoring method using smart mobile phone

    NASA Astrophysics Data System (ADS)

    Zhao, Xuefeng; Peng, Deli; Hu, Weitong; Guan, Quanhua; Yu, Yan; Li, Mingchu; Ou, Jinping

    2015-04-01

    Seismic intensity map which reflects the actual situation of destruction in a certain area after the earthquake, and it is of great significance in guiding relief work and assessing damage loss. Based on cloud monitoring method proposed, we developed software, which can quickly investigate the seismic intensity distribution and draw the intensity map after the earthquake using the big data collected by individual smart phone questionnaire in earthquake zone. According to seismic attenuation law, we generated some seismic intensity values to test our system and successfully drawn out of the seismic intensity map.

  16. Feasibility of Monitoring Rock Fall in Yosemite Valley using Seismic Methods

    SciTech Connect

    Myers, S; Rock, D; Mayeda, K

    2000-03-02

    Public awareness of rock-fall hazard in Yosemite Valley has heightened after events in 1996 and 1999. Reports of audible blasts prior to rock-fall events suggest that rock cracking may in some instances precede the detachment a block from the cliff face. Seismic methods may be used to detect and locate small, inaudible rock cracking events, resulting in a catalog that outlines active areas and quantifies the level of activity. In order to test the feasibility of monitoring rock-fall activity with seismic methods, the Test Yosemite Rock-Fall Network (TYRN) was operated in the late summer and fall of 1999. The TYRN included five stations in the vicinity of the 1999 rock fall events: 2 stations at the base of the cliff and 3 above. Location of events depends on an estimate of seismic-wave velocity. During the TYRN deployment, a septic tank near Glacier Point was demolished, allowing the velocity of seismic P-waves to be calibrated. P-wave velocity was found to be about 5.68 km/s. Recordings of the explosion also allow assessment of arrival time precision, which controls the precision of seismic locations. Explosion recordings suggest that P-waves can be picked with a precision of about 0.005 seconds, suggesting that a seismic monitoring system would be able to locate events on the cliff face with sufficient precision to be useful in rock-fall monitoring. We used the amplitude of seismic noise recorded on the test network to determine the smallest event likely to be detected by the TYRN . An event with equivalent earthquake magnitude of -2.6 would be detectable at a sufficient number of stations to afford a location. This magnitude is equivalent to about 1.8 centimeters of slip on a surface with area of 1 square meter. Smaller displacements would be detectable for larger slip surfaces. The vast majority of events recorded on the TYRN were from the Mammoth Lakes region. About 5 to 6 events from the Mammoth Lakes area were recorded per day, but considerably more events

  17. A probabilistic method for evaluation of seismic amplification at a regional scale - A case study in some high seismic risk areas of the Northern Apennines (Italy)

    NASA Astrophysics Data System (ADS)

    Delle Donne, Dario; Ripepe, Maurizio; Lacanna, Giorgio; Marchetti, Emanuele; Fabbroni, Pierangelo; Baglione, Massimo; D'Intinosante, Vittorio

    2014-05-01

    Seismic amplification caused by local geological conditions has an important role in seismic risk assessment. The main parameters controlling seismic amplification are the shear wave velocities of shallow sub-surface (Vs) and the thickness of soft sediments (h). However, the knowledge of shear wave velocity profile is usually sparse and can not be measured over large areas. In this study we propose a method that integrates data from surface geological maps with data from subsurface seismo-stratigraphic well-logs, and is aimed to estimate seismic amplification over large areas (~100 km2) through a probabilistic approach. The methodology we developed is characterized by the following steps: 1. Analysis of the geological framework and definition of Seismic Units; 2. 1-D seismic modeling of each Seismic Unit; 3. Probability analysis of Seismic Amplification. Probability function of seismic amplification for each Seismic Unit is calculated for all the possible combinations of the expected values of Vs and thickness (h). We apply this approach to seismic areas in the Northern Apennines (Italy). Finally, the results of this analysis have been validated by seismic amplification measurements using local and regional earthquakes and with macro-seismic data. The comparison between the predicted amplification using this probabilistic approach and the measured seismic amplification shows a general agreement. This work is not intended as an alternative to the standard methodologies to calculate site effect, but offers a new approach to identify areas potentially more vulnerable.

  18. 3-D Seismic Methods for Geothermal Reservoir Exploration and Assessment--Summary

    SciTech Connect

    Majer, E.L.

    2003-07-14

    A wide variety of seismic methods covering the spectrum from DC to kilohertz have been employed at one time or the other in geothermal environments. The reasons have varied from exploration for a heat source to attempting to find individual fractures producing hot fluids. For the purposes here we will assume that overall objective of seismic imaging is for siting wells for successful location of permeable pathways (often fracture permeability) that are controlling flow and transport in naturally fractured reservoirs. The application could be for exploration of new resources or for in-fill/step-out drilling in existing fields. In most geothermal environments the challenge has been to separate the ''background'' natural complexity and heterogeneity of the matrix from the fracture/fault heterogeneity controlling the fluid flow. Ideally one not only wants to find the fractures, but the fractures that are controlling the flow of the fluids. Evaluated in this work is current state-of-the-art surface (seismic reflection) and borehole seismic methods (Vertical Seismic Profiling (VSP), Crosswell and Single Well) to locate and quantify geothermal reservoir characteristics. The focus is on active methods; the assumption being that accuracy is needed for successful well siting. Passive methods are useful for exploration and detailed monitoring for in-fill drilling, but in general the passive methods lack the precision and accuracy for well siting in new or step out areas. In addition, MEQ activity is usually associated with production, after the field has been taken to a mature state, thus in most cases it is assumed that there is not enough MEQ activity in unproduced areas to accurately find the permeable pathways. The premise of this review is that there may new developments in theory and modeling, as well as in data acquisition and processing, which could make it possible to image the subsurface in much more detail than 15 years ago. New understanding of the effect of

  19. Deep Seismic Researches Of Seismic-Active Zones With Use Of High-Power Vibrators - Technique, Outcomes, Outlooks

    NASA Astrophysics Data System (ADS)

    Soloviev, V.; Seleznev, V.; Emanov, A.; Sal`Nikov, A.; Kashun, V.; Glinsky, B.; Kovalevsky, V.; Zhemchugova, I.; Danilov, I.; Liseikin, A.

    2004-12-01

    There are presented the materials of deep vibroseism researches, carried out in seismic active regions of Siberia with use of stationary (100-tos power) and moveable vibration sources (40-60tons power) and mobile digital recording equipment. There are given some examples of unique, have no world analogues, correlograms from high-power vibrators on distances to 400km and more. Using new vibroseismic technology of deep seismic researches, there were got detail deep sections of the Earth's crust and upper mantle, including time-sections of CDP-DSS up to depth of 80km. Materials of vibroseismic investigations on 2500km of seismic profiles in hard-to-reach regions of the Altay-Sayan region, the Baikal rift zone and Okhotsko-Chukotski regions are evidence of high cost efficiency, ecological safety, possibility to be realized in hard-to-reach region and finally of availability of deep seismic investigations with use of high-power vibration sources.

  20. Temporary seismic networks on active volcanoes of Kamchatka (Russia)

    NASA Astrophysics Data System (ADS)

    Jakovlev, Andrey; Koulakov, Ivan; Abkadyrov, Ilyas; Shapiro, Nikolay; Kuznetsov, Pavel; Deev, Evgeny; Gordeev, Evgeny; Chebrov, Viktor

    2016-04-01

    We present details of four field campaigns carried out on different volcanoes of Kamchatka in 2012-2015. Each campaign was performed in three main steps: (i) installation of the temporary network of seismic stations; (ii) autonomous continuous registration of three component seismic signal; (III) taking off the network and downloading the registered data. During the first campaign started in September 2012, 11 temporary stations were installed over the Avacha group of volcanoes located 30 km north to Petropavlovsk-Kamchatsky in addition to the seven permanent stations operated by the Kamchatkan Branch of the Geophysical Survey (KBGS). Unfortunately, with this temporary network we faced with two obstacles. The first problem was the small amount of local earthquakes, which were detected during operation time. The second problem was an unexpected stop of several stations only 40 days after deployment. Nevertheless, after taking off the network in August 2013, the collected data appeared to be suitable for analysis using ambient noise. The second campaign was conducted in period from August 2013 to August 2014. In framework of the campaign, 21 temporary stations were installed over Gorely volcano, located 70 km south to Petropavlovsk-Kamchatsky. Just in time of the network deployment, Gorely Volcano became very seismically active - every day occurred more than 100 events. Therefore, we obtain very good dataset with information about thousands of local events, which could be used for any type of seismological analysis. The third campaign started in August 2014. Within this campaign, we have installed 19 temporary seismic stations over Tolbachik volcano, located on the south side of the Klyuchevskoy volcano group. In the same time on Tolbachik volcano were installed four temporary stations and several permanent stations operated by the KBGS. All stations were taking off in July 2015. As result, we have collected a large dataset, which is now under preliminary analysis

  1. Seismicity characteristics of a potentially active Quaternary volcano: The Tatun Volcano Group, northern Taiwan

    NASA Astrophysics Data System (ADS)

    Konstantinou, Konstantinos I.; Lin, Cheng-Horng; Liang, Wen-Tzong

    2007-02-01

    The Tatun Volcano Group (TVG) is located at the northern tip of Taiwan, near the capital Taipei and close to two nuclear power plants. Because of lack of any activity in historical times it has been classified as an extinct volcano, even though more recent studies suggest that TVG might have been active during the last 20 ka. In May 2003 a seismic monitoring project at the TVG area was initiated by deploying eight three-component seismic stations some of them equipped with both short-period and broadband sensors. During the 18 months observation period local seismicity mainly consisted of high frequency earthquakes either occurring as isolated events, or as a continuous sequence in the form of spasmodic bursts. Mixed and low frequency events were also present during the same period, even though they occurred only rarely. Arrival times from events with clear P-/S-wave phases were inverted in order to obtain a minimum 1D velocity model with station corrections. Probabilistic nonlinear earthquake locations were calculated for all these events using the newly derived velocity model. Most high frequency seismicity appeared to be concentrated near the areas of hydrothermal activity, forming tight clusters at depths shallower than 4 km. Relative locations, calculated using the double-difference method and utilising catalogue and cross-correlation differential traveltimes, showed insignificant differences when compared to the nonlinear probabilistic locations. In general, seismicity in the TVG area seems to be primarily driven by circulation of hydrothermal fluids as indicated by the occurrence of spasmodic bursts, mixed/low frequency events and a b-value (1.17 ± 0.1) higher than in any other part of Taiwan. These observations, that are similar to those reported in other dormant Quaternary volcanoes, indicate that a magma chamber may still exist beneath TVG and that a future eruption or period of unrest should not be considered unlikely.

  2. Testing the recent Santorini seismic activity for possible tidal triggering effect

    NASA Astrophysics Data System (ADS)

    Contadakis, Michael E.; Arabelos, Dimitrios N.; Vergos, George

    2013-04-01

    Applying the Hi(stogram)Cum(ulation) method, which was introduced recently by Cadicheanu, van Ruymbecke and Zhu (2007), we analyze the series of the earthquakes occurred in the last 50 years in seismic active areas of Greece, i.e. the areas (a) of the Mygdonian Basin(Contadakis et al. 2007), (b) of the Ionian Islands (Contadakis et al. 2012 ) and (c) of the Hellenic Arc (Vergos et al. 2012 ). The result of the analysis for all the areas indicate that the monthly variation of the frequencies of earthquake occurrence is in accordance with the period of the tidal lunar monthly and semi-monthly (Mm and Mf) variations and the same happens with the corresponding daily variations of the frequencies of earthquake occurrence with the diurnal luni-solar (K1) and semidiurnal lunar (M2) tidal variations. In addition the confidence level for the identification of such period accordance between earthquakes occurrence frequency and tidal periods varies with seismic activity, i.e. the higher confidence level corresponds to periods with stronger seismic activity. These results are in favor of a tidal triggering process on earthquakes when the stress in the focal area is near the critical level. Based on these results, we consider the confidence level of earthquake occurrence - tidal period accordance as an index of tectonic stress criticality for earthquake occurrence and we check if the recent increase in the seismic activity at the Santorini island complex indicate that the faults Kameni and Columbo (to which the seismicity is clustered) (Chouliaras et al. 2013) are mature for a stronger earthquake. In this paper we present the results of this test. References Cadicheanu, N., van Ruymbeke, M andZhu P.,2007:Tidal triggering evidence of intermediate depth earthquakes in Vrancea zone(Romania), NHESS 7,733-740. Contadakis, M. E., Arabelos, D. N., Spatalas, S., 2009, Evidence for tidal triggering on the shallow earthquakes of the seismic area of Mygdonia basin, North Greece, in

  3. Characterising volcanic activity of Piton de la Fournaise volcano by the spatial distribution of seismic velocity changes

    NASA Astrophysics Data System (ADS)

    Sens-Schoenfelder, C.; Pomponi, E.

    2013-12-01

    We apply Passive Image Interferometry to investigate the seismic noise recorded from October 2009 until December 2011 by 21 stations of the IPGP/OVPF seismic network installed on Piton de la Fournaise volcano within the UnderVolc project. The analyzed period contains three eruptions in 2009 and January 2010, two eruptions plus one dyke intrusion in late 2010, and a seismic crises in 2011. Seismic noise of vertical and horizontal components is cross-correlated to measure velocity changes as apparent stretching of the coda. For some station pairs the apparent velocity changes exceed 1% and a decorrelation of waveforms is observed at the time of volcanic activity. This distorts monitoring results if changes are measured with respect to a global reference. To overcome this we present a method to estimate changes using multiple references that stabilizes the quality of estimated velocity changes. We observe abrupt changes that occur coincident with volcanic events as well as long term transient signals. Using a simple assumption about the spatial sensitivity of our measurements we can map the spatial distribution of velocity changes for selected periods. Comparing these signals with volcanic activity and GPS derived surface deformation we can identify patterns of the velocity changes that appear characteristic for the type of volcanic activity. We can differentiate intrusive processes associated with inflation and increased seismic activity, periods of relaxation without seismicity and eruptions solely based on the velocity signal. This information can help to assess the processes acting in the volcano.

  4. Fault Activity, Seismicity and GPS Deformation of the Seismic Gap along the Red River Fault Zone (RRFZ) in Yunnan, China

    NASA Astrophysics Data System (ADS)

    Xue-Ze, Wen; Shengli, Ma; Fang, Du; Feng, Long

    2016-04-01

    Along the middle segment of the NW-trending and dextral-slip Red River fault zone (RRFZ), also the Honghe fault zone, Yunnan, China, there has been little of modern seismicity since the 1970's. Some Chinese researchers believed that this fault segment is inactive in the late Quaternary. However, more and more evidence shows that the middle segment of RRFZ is geologically-active in the late Quaternary, even is a Holocene-active one with evidence of paleo-earthquakes occurring. Our study suggests that along the fault segment there has been no any major earthquake occurring for over 500 years at least, and a large-scale seismic gap, the Honghe seismic gap, have formed there. On the modern seismicity, the middle segment of RRFZ has presented as a fault portion without or with very few small earthquakes occurring since the 1980's, but surrounded by several areas with low b-values, suggesting relatively high stress having built-up there. Also, GPS deformation analysis suggests that this fault segment has tightly locked already. Such tight locking would be associated with the fault geometry: A large-scale restraining bend of about 30°over a distance of ~100 km exists along the main fault trace along RRFZ between Yuanjiang and Yuanyang. However, how such a restraining bend makes the middle segment of RRFZ have tightly locked? How much strain has built up there? Moreover, how about the long-term seismic potential of major earthquake on the middle segment of RRFZ, and on some secondary active faults of the two sides of the segment, especially on the parallel faults Chuxiong, Qujiang and Shiping. All these are issues we want to study further. Keywords: Red River Fault Zone, Seismic Gap, Fault Activity, Seismicity, GPS Deformation

  5. Active damping performance of the KAGRA seismic attenuation system prototype

    NASA Astrophysics Data System (ADS)

    Fujii, Yoshinori; Sekiguchi, Takanori; Takahashi, Ryutaro; Aso, Yoichi; Barton, Mark; Erasmo Peña Arellano, Fabián; Shoda, Ayaka; Akutsu, Tomotada; Miyakawa, Osamu; Kamiizumi, Masahiro; Ishizaki, Hideharu; Tatsumi, Daisuke; Hirata, Naoatsu; Hayama, Kazuhiro; Okutomi, Koki; Miyamoto, Takahiro; Ishizuka, Hideki; DeSalvo, Riccardo; Flaminio, Raffaele

    2016-05-01

    The Large-scale Cryogenic Gravitational wave Telescope (formerly LCGT now KAGRA) is presently under construction in Japan. This May we assembled a prototype of the seismic attenuation system (SAS) for the beam splitter and the signal recycling mirrors of KAGRA, which we call Type-B SAS, and evaluated its performance at NAOJ (Mitaka, Toyko). We investigated its frequency response, active damping performance, vibration isolation performance and long-term stability both in and out of vacuum. From the frequency response test and the active damping performance test, we confirmed that the SAS worked as we designed and that all mechanical resonances which could disturb lock acquisition and observation are damped within 1 minute, which is required for KAGRA, by the active controls.

  6. Seismic exploration of Fuji volcano with active sources in 2003

    NASA Astrophysics Data System (ADS)

    Oikawa, J.; Kagiyama, T.; Tanaka, S.; Miyamachi, H.; Tsutsui, T.; Ikeda, Y.; Katayama, H.; Matsuo, N.; Oshima, H.; Nishimura, Y.; Yamamoto, K.; Watanabe, T.; Yamazaki, F.

    2004-12-01

    Fuji volcano (altitude 3,776 m) is the largest basaltic stratovolcano in Japan. In late August and early September 2003, seismic exploration was conducted around Fuji volcano by the detonation of 500 kg charges of dynamite to investigate the seismic structure of that area. Seismographs with an eigenfrequency of 2 Hz were used for observation, positioned along a WSW-ENE line passing through the summit of the mountain. A total of 469 observation points were installed at intervals of 250-500 m. The data were stored in memory on-site using data loggers. The sampling interval was 4 ms. Charges were detonated at 5 points, one at each end of the observation line and 3 along its length. The first arrival times at each observation point for each detonation were recorded as data. The P-wave velocity structure directly below the observation line was determined by forward calculation using the ray tracing method [Zelt and Smith, 1992]. The P-wave velocity structure below the volcano, assuming a layered structure, was found to be as follows. (1) The first layer extends for about 40 km around the summit and to a depth of 1-2 km. The P-wave velocity is 2.5 km/s on the upper surface of the layer and 3.5 km/s on the lower interface. (2) The second layer has P-wave velocities of 4.0 km/s on the top interface and 5.5 km/s at the lower interface. The layer is 25 km thick to the west of the summit and 1-2 km thick to the east, and forms a dome shape with a peak altitude of 2000 m directly below the summit. (3) The third layer is 5-12 km thick and has P-wave velocities of 5.7 km/s at the top interface and 6.5 km/s at the lower interface. This layer reaches shallower levels to the east of the summit, corresponding to the area where the second layer is thinner. Mt. Fuji is located slightly back from where the Philippine Sea Plate subducts below the Eurasian plate in association with collision with the Izu Peninsula. Matsuda (1971) suggested that Mt. Fuji lies on the same uplifted body as

  7. Global seismic waveform tomography based on the spectral element method.

    NASA Astrophysics Data System (ADS)

    Capdeville, Y.; Romanowicz, B.; Gung, Y.

    2003-04-01

    Because seismogram waveforms contain much more information on the earth structure than body wave time arrivals or surface wave phase velocities, inversion of complete time-domain seismograms should allow much better resolution in global tomography. In order to achieve this, accurate methods for the calculation of forward propagation of waves in a 3D earth need to be utilized, which presents theoretical as well as computational challenges. In the past 8 years, we have developed several global 3D S velocity models based on long period waveform data, and a normal mode asymptotic perturbation formalism (NACT, Li and Romanowicz, 1996). While this approach is relatively accessible from the computational point of view, it relies on the assumption of smooth heterogeneity in a single scattering framework. Recently, the introduction of the spectral element method (SEM) has been a major step forward in the computation of seismic waveforms in a global 3D earth with no restrictions on the size of heterogeneities (Chaljub, 2000). While this method is computationally heavy when the goal is to compute large numbers of seismograms down to typical body wave periods (1-10 sec), it is much more accessible when restricted to low frequencies (T>150sec). When coupled with normal modes (e.g. Capdeville et al., 2000), the numerical computation can be restricted to a spherical shell within which heterogeneity is considered, further reducing the computational time. Here, we present a tomographic method based on the non linear least square inversion of time domain seismograms using the coupled method of spectral elements and modal solution. SEM/modes are used for both the forward modeling and to compute partial derivatives. The parametrisation of the model is also based on the spectral element mesh, the "cubed sphere" (Sadourny, 1972), which leads to a 3D local polynomial parametrization. This parametrization, combined with the excellent earth coverage resulting from the full 3D theory used

  8. Mini-Sosie high-resolution seismic method aids hazards studies

    USGS Publications Warehouse

    Stephenson, W.J.; Odum, J.; Shedlock, K.M.; Pratt, T.L.; Williams, R.A.

    1992-01-01

    The Mini-Sosie high-resolution seismic method has been effective in imaging shallow-structure and stratigraphic features that aid in seismic-hazard and neotectonic studies. The method is not an alternative to Vibroseis acquisition for large-scale studies. However, it has two major advantages over Vibroseis as it is being used by the USGS in its seismic-hazards program. First, the sources are extremely portable and can be used in both rural and urban environments. Second, the shifting-and-summation process during acquisition improves the signal-to-noise ratio and cancels out seismic noise sources such as cars and pedestrians. -from Authors

  9. The Effect of Recent Volcanic Activity on the Seismic Structure of Madagascar

    NASA Astrophysics Data System (ADS)

    Wysession, M. E.; Aleqabi, G. I.; Pratt, M. J.; Shore, P.; Wiens, D. A.; Nyblade, A.; Rambolamanana, G.; Andriampenomanana Ny Ony, F. S. T.; Tsiriandrimanana, R.

    2014-12-01

    The seismic structure of Madagascar is determined using ambient-noise and two-plane-wave earthquake surface waves analyses. A deep low-velocity anomaly is seen in regions of recent volcanic activity in the central and northern regions of the island. The primary data used are from the 2011-2013 MACOMO (Madagascar, the Comoros, and Mozambique) broadband seismic array from the PASSCAL program of IRIS (Incorporated Research Institutions for Seismology), funded by the NSF. Additional data came from the RHUM-RUM project (led by G. Barruol and K. Sigloch), the Madagascar Seismic Profile (led by F. Tilmann), and the GSN. For the ambient-noise study, Rayleigh wave green's functions for all interstation paths are extracted from the broadband seismic data recorded from August 2011 until October 2013. Rayleigh wave group and phase velocity dispersion curves are extracted in the 8 - 50 s period range, identifying shallow crustal structure. For deeper structure, the two-plane-wave method is used on teleseismic earthquake data to obtain surface wave phase velocities in the 20 - 182 s period range. In the inversion, a finite-frequency kernel is used for each period, and a 1-D shear velocity structure is determined at each location. A three-dimensional S-wave velocity model of the crust and upper mantle is obtained from assembling the 1-D models. Preliminary results show a good correlation between the Rayleigh wave velocities and the geology of Madagascar, which includes areas of ancient Archaean craton. The slowest seismic velocities are associated with known volcanic regions in both the central and northern regions, which have experienced volcanic activity within the past million years.

  10. First seismic shear wave velocity profile of the lunar crust as extracted from the Apollo 17 active seismic data by wavefield gradient analysis

    NASA Astrophysics Data System (ADS)

    Sollberger, David; Schmelzbach, Cedric; Robertsson, Johan O. A.; Greenhalgh, Stewart A.; Nakamura, Yosio; Khan, Amir

    2016-04-01

    We present a new seismic velocity model of the shallow lunar crust, including, for the first time, shear wave velocity information. So far, the shear wave velocity structure of the lunar near-surface was effectively unconstrained due to the complexity of lunar seismograms. Intense scattering and low attenuation in the lunar crust lead to characteristic long-duration reverberations on the seismograms. The reverberations obscure later arriving shear waves and mode conversions, rendering them impossible to identify and analyze. Additionally, only vertical component data were recorded during the Apollo active seismic experiments, which further compromises the identification of shear waves. We applied a novel processing and analysis technique to the data of the Apollo 17 lunar seismic profiling experiment (LSPE), which involved recording seismic energy generated by several explosive packages on a small areal array of four vertical component geophones. Our approach is based on the analysis of the spatial gradients of the seismic wavefield and yields key parameters such as apparent phase velocity and rotational ground motion as a function of time (depth), which cannot be obtained through conventional seismic data analysis. These new observables significantly enhance the data for interpretation of the recorded seismic wavefield and allow, for example, for the identification of S wave arrivals based on their lower apparent phase velocities and distinct higher amount of generated rotational motion relative to compressional (P-) waves. Using our methodology, we successfully identified pure-mode and mode-converted refracted shear wave arrivals in the complex LSPE data and derived a P- and S-wave velocity model of the shallow lunar crust at the Apollo 17 landing site. The extracted elastic-parameter model supports the current understanding of the lunar near-surface structure, suggesting a thin layer of low-velocity lunar regolith overlying a heavily fractured crust of basaltic

  11. A robust absorbing layer method for anisotropic seismic wave modeling

    SciTech Connect

    Métivier, L.; Brossier, R.; Labbé, S.; Operto, S.; Virieux, J.

    2014-12-15

    When applied to wave propagation modeling in anisotropic media, Perfectly Matched Layers (PML) exhibit instabilities. Incoming waves are amplified instead of being absorbed. Overcoming this difficulty is crucial as in many seismic imaging applications, accounting accurately for the subsurface anisotropy is mandatory. In this study, we present the SMART layer method as an alternative to PML approach. This method is based on the decomposition of the wavefield into components propagating inward and outward the domain of interest. Only outgoing components are damped. We show that for elastic and acoustic wave propagation in Transverse Isotropic media, the SMART layer is unconditionally dissipative: no amplification of the wavefield is possible. The SMART layers are not perfectly matched, therefore less accurate than conventional PML. However, a reasonable increase of the layer size yields an accuracy similar to PML. Finally, we illustrate that the selective damping strategy on which is based the SMART method can prevent the generation of spurious S-waves by embedding the source in a small zone where only S-waves are damped.

  12. Boundary separating the seismically active reelfoot rift from the sparsely seismic Rough Creek graben, Kentucky and Illinois

    USGS Publications Warehouse

    Wheeler, R.L.

    1997-01-01

    The Reelfoot rift is the most active of six Iapetan rifts and grabens in central and eastern North America. In contrast, the Rough Creek graben is one of the least active, being seismically indistinguishable from the central craton of North America. Yet the rift and graben adjoin. Hazard assessment in the rift and graben would be aided by identification of a boundary between them. Changes in the strikes of single large faults, the location of a Cambrian transfer zone, and the geographic extent of alkaline igneous rocks provide three independent estimates of the location of a structural boundary between the rift and the graben. The boundary trends north-northwest through the northeastern part of the Fluorspar Area Fault Complex of Kentucky and Illinois, and has no obvious surface expression. The boundary involves the largest faults, which are the most likely to penetrate to hypocentral depths, and the boundary coincides with the geographic change from abundant seismicity in the rift to sparse seismicity in the graben. Because the structural boundary was defined by geologic variables that are expected to be causally associated with seismicity, it may continue to bound the Reelfoot rift seismicity in the future.

  13. Methods of seismic zone localization in the highly stressed geological environment in mining natural-engineering system

    NASA Astrophysics Data System (ADS)

    Kozyrev, A.; Fedotova, Iu.; Zhuravleva, O.

    2012-04-01

    During developing mineral deposits in the geological environment the anomalous energy-saturated zones (parts of highly stressed rocks) are being formed. As a result in the rock mass rockbursts and mining-induced earthquakes occur. The largest mining-induced earthquakes (M 4.0 - 4.2) were registered at the mines of the Khibiny and Lovozersky massifs of the Kola Peninsula. The energy-saturated zones migrate subject to displacement of front of working faces. Location and dimensions of the zones are estimated according to data of analytical investigations and experimental determinations in the rock mass. In some cases (for example, when developing blocks-pillars and transition zones between open and underground mining operations or adjacent mines) all the mining area is a united energy-saturated zone, where the main problems occur concerning mining workings stability management, and under rockbursts hazardous conditions there occur problems concerning mining-induced seismicity manifestations. Parameters of geological environment seismic emission are objective indicators of geological environment energy-saturation. The assessment of their changing is a basis of methods of seismic zones localization and detection of their migration during mining operations development. To assess a current state and determine conditions of transition of geological environment parts into the critical state there carried out investigations concerning space-time regularities of rock mass seismicity parameters changing in the mines' geomechanical space. The following parameters are considered as characteristics of rock mass seismicity: fractal criterion, dip angle criterion for seismic events recurrence graph, concentration criterion, and criterion of fissures' average length. A complex assessment of single parameters range is applied to get the better results. The analysis also takes into account influence of deterministic factors: fracture disturbances and stope face boundaries. Analysis

  14. An active seismic experiment at Tenerife Island (Canary Island, Spain): Imaging an active volcano edifice

    NASA Astrophysics Data System (ADS)

    Garcia-Yeguas, A.; Ibañez, J. M.; Rietbrock, A.; Tom-Teidevs, G.

    2008-12-01

    An active seismic experiment to study the internal structure of Teide Volcano was carried out on Tenerife, a volcanic island in Spain's Canary Islands. The main objective of the TOM-TEIDEVS experiment is to obtain a 3-dimensional structural image of Teide Volcano using seismic tomography and seismic reflection/refraction imaging techniques. At present, knowledge of the deeper structure of Teide and Tenerife is very limited, with proposed structural models mainly based on sparse geophysical and geological data. This multinational experiment which involves institutes from Spain, Italy, the United Kingdom, Ireland, and Mexico will generate a unique high resolution structural image of the active volcano edifice and will further our understanding of volcanic processes.

  15. Stress-strain sensor for monitoring seismic precursors and fault activities in the sand

    NASA Astrophysics Data System (ADS)

    Du, Qiujiao; Sun, Wei; Zeng, Zuoxun

    2016-04-01

    In this paper, a sensor to monitor stress-strain signals in a granular medium is used to detect seismic precursory information. Compared with the widely used sensors of borehole stress in the rock, the sensor has more convenient operation, higher output sensitivity, compactness and farther propagation effect. The stress and strain changes before Pu'er Ms6.4 earthquake in China are recorded by Beijing and Xinmin stations, and its corresponding fault activities are analyzed. Study indicates anomalous amplitude of strain signal reaches 10 times higher than that of ordinary background, and compressive oscillation and extensional oscillation occurred constantly before the earthquake. The method and results presented in the paper provide a new way for investigating seismic precursors for shallow-source earthquakes.

  16. Seismic methods for resource exploration in enhanced geothermal systems

    SciTech Connect

    Gritto, Roland; Majer, Ernest L.

    2002-06-12

    A finite-difference modeling study of seismic wave propagation was conducted to determine how to best investigate subsurface faults and fracture zones in geothermal areas. The numerical model was created based on results from a previous seismic reflection experiment. A suite of fault models was investigated including blind faults and faults with surface expressions. The seismic data suggest that blind faults can be detected by a sudden attenuation of seismic wave amplitudes, as long the fault is located below the receiver array. Additionally, a conversion from P- to S-waves indicates the reflection and refraction of the P-waves while propagating across the fault. The drop in amplitudes and the excitation of S-waves can be used to estimate the location of the fault at depth. The accuracy of the numerical modeling depends on the availability of a priori in situ information (velocity and density) from borehole experiments in the geothermal area.

  17. The Lusi seismic experiment: An initial study to understand the effect of seismic activity to Lusi

    NASA Astrophysics Data System (ADS)

    Karyono, Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Masturyono, Rudiyanto, Ariska; Pranata, Bayu; Muzli, Widodo, Handi Sulistyo; Sudrajat, Ajat; Sugiharto, Anton

    2015-04-01

    The spectacular Lumpur Sidoarjo (Lusi) eruption started in northeast Java on the 29 of May 2006 following a M6.3 earthquake striking the island [1,2]. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system [3] and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. The Lusi seismic experiment is a project aims to begin a detailed study of seismicity around the Lusi area. In this initial phase we deploy 30 seismometers strategically distributed in the area around Lusi and along the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. The purpose of the initial monitoring is to conduct a preliminary seismic campaign aiming to identify the occurrence and the location of local seismic events in east Java particularly beneath Lusi.This network will locate small event that may not be captured by the existing BMKG network. It will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-AW region and spatial and temporal variations of vp/vs ratios. The goal of this study is to understand how the seismicity occurring along the Sunda subduction zone affects to the behavior of the Lusi eruption. Our study will also provide a large dataset for a qualitative analysis of earthquake triggering studies, earthquake-volcano and earthquake-earthquake interactions. In this study, we will extract Green's functions from ambient seismic noise data in order to image the shallow subsurface structure beneath LUSI area. The waveform cross-correlation technique will be apply to all of recordings of ambient seismic noise at 30 seismographic stations around the LUSI area. We use the dispersive behaviour of the retrieved Rayleigh waves to infer velocity structures in the shallow subsurface.

  18. The Lusi seismic experiment: An initial study to understand the effect of seismic activity to Lusi

    SciTech Connect

    Karyono; Mazzini, Adriano; Sugiharto, Anton; Lupi, Matteo; Syafri, Ildrem; Masturyono,; Rudiyanto, Ariska; Pranata, Bayu; Muzli,; Widodo, Handi Sulistyo; Sudrajat, Ajat

    2015-04-24

    The spectacular Lumpur Sidoarjo (Lusi) eruption started in northeast Java on the 29 of May 2006 following a M6.3 earthquake striking the island [1,2]. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system [3] and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. The Lusi seismic experiment is a project aims to begin a detailed study of seismicity around the Lusi area. In this initial phase we deploy 30 seismometers strategically distributed in the area around Lusi and along the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. The purpose of the initial monitoring is to conduct a preliminary seismic campaign aiming to identify the occurrence and the location of local seismic events in east Java particularly beneath Lusi.This network will locate small event that may not be captured by the existing BMKG network. It will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-AW region and spatial and temporal variations of vp/vs ratios. The goal of this study is to understand how the seismicity occurring along the Sunda subduction zone affects to the behavior of the Lusi eruption. Our study will also provide a large dataset for a qualitative analysis of earthquake triggering studies, earthquake-volcano and earthquake-earthquake interactions. In this study, we will extract Green’s functions from ambient seismic noise data in order to image the shallow subsurface structure beneath LUSI area. The waveform cross-correlation technique will be apply to all of recordings of ambient seismic noise at 30 seismographic stations around the LUSI area. We use the dispersive behaviour of the retrieved Rayleigh waves to infer velocity structures in the shallow subsurface.

  19. Best Estimate Method vs Evaluation Method: a comparison of two techniques in evaluating seismic analysis and design

    SciTech Connect

    Bumpus, S.E.; Johnson, J.J.; Smith, P.D.

    1980-05-01

    The concept of how two techniques, Best Estimate Method and Evaluation Method, may be applied to the traditional seismic analysis and design of a nuclear power plant is introduced. Only the four links of the seismic analysis and design methodology chain (SMC) - seismic input, soil-structure interaction, major structural response, and subsystem response - are considered. The objective is to evaluate the compounding of conservatisms in the seismic analysis and design of nuclear power plants, to provide guidance for judgments in the SMC, and to concentrate the evaluation on that part of the seismic analysis and design which is familiar to the engineering community. An example applies the effects of three-dimensional excitations on a model of a nuclear power plant structure. The example demonstrates how conservatisms accrue by coupling two links in the SMC and comparing those results to the effects of one link alone. The utility of employing the Best Estimate Method vs the Evaluation Method is also demonstrated.

  20. Applying Seismic Methods to National Security Problems: Matched Field Processing With Geological Heterogeneity

    SciTech Connect

    Myers, S; Larsen, S; Wagoner, J; Henderer, B; McCallen, D; Trebes, J; Harben, P; Harris, D

    2003-10-29

    Seismic imaging and tracking methods have intelligence and monitoring applications. Current systems, however, do not adequately calibrate or model the unknown geological heterogeneity. Current systems are also not designed for rapid data acquisition and analysis in the field. This project seeks to build the core technological capabilities coupled with innovative deployment, processing, and analysis methodologies to allow seismic methods to be effectively utilized in the applications of seismic imaging and vehicle tracking where rapid (minutes to hours) and real-time analysis is required. The goal of this project is to build capabilities in acquisition system design, utilization of full three-dimensional (3D) finite difference modeling, as well as statistical characterization of geological heterogeneity. Such capabilities coupled with a rapid field analysis methodology based on matched field processing are applied to problems associated with surveillance, battlefield management, finding hard and deeply buried targets, and portal monitoring. This project, in support of LLNL's national-security mission, benefits the U.S. military and intelligence community. Fiscal year (FY) 2003 was the final year of this project. In the 2.5 years this project has been active, numerous and varied developments and milestones have been accomplished. A wireless communication module for seismic data was developed to facilitate rapid seismic data acquisition and analysis. The E3D code was enhanced to include topographic effects. Codes were developed to implement the Karhunen-Loeve (K-L) statistical methodology for generating geological heterogeneity that can be utilized in E3D modeling. The matched field processing methodology applied to vehicle tracking and based on a field calibration to characterize geological heterogeneity was tested and successfully demonstrated in a tank tracking experiment at the Nevada Test Site. A three-seismic-array vehicle tracking testbed was installed on site

  1. Seismic energy data analysis of Merapi volcano to test the eruption time prediction using materials failure forecast method (FFM)

    NASA Astrophysics Data System (ADS)

    Anggraeni, Novia Antika

    2015-04-01

    The test of eruption time prediction is an effort to prepare volcanic disaster mitigation, especially in the volcano's inhabited slope area, such as Merapi Volcano. The test can be conducted by observing the increase of volcanic activity, such as seismicity degree, deformation and SO2 gas emission. One of methods that can be used to predict the time of eruption is Materials Failure Forecast Method (FFM). Materials Failure Forecast Method (FFM) is a predictive method to determine the time of volcanic eruption which was introduced by Voight (1988). This method requires an increase in the rate of change, or acceleration of the observed volcanic activity parameters. The parameter used in this study is the seismic energy value of Merapi Volcano from 1990 - 2012. The data was plotted in form of graphs of seismic energy rate inverse versus time with FFM graphical technique approach uses simple linear regression. The data quality control used to increase the time precision employs the data correlation coefficient value of the seismic energy rate inverse versus time. From the results of graph analysis, the precision of prediction time toward the real time of eruption vary between -2.86 up to 5.49 days.

  2. Seismic energy data analysis of Merapi volcano to test the eruption time prediction using materials failure forecast method (FFM)

    SciTech Connect

    Anggraeni, Novia Antika

    2015-04-24

    The test of eruption time prediction is an effort to prepare volcanic disaster mitigation, especially in the volcano’s inhabited slope area, such as Merapi Volcano. The test can be conducted by observing the increase of volcanic activity, such as seismicity degree, deformation and SO2 gas emission. One of methods that can be used to predict the time of eruption is Materials Failure Forecast Method (FFM). Materials Failure Forecast Method (FFM) is a predictive method to determine the time of volcanic eruption which was introduced by Voight (1988). This method requires an increase in the rate of change, or acceleration of the observed volcanic activity parameters. The parameter used in this study is the seismic energy value of Merapi Volcano from 1990 – 2012. The data was plotted in form of graphs of seismic energy rate inverse versus time with FFM graphical technique approach uses simple linear regression. The data quality control used to increase the time precision employs the data correlation coefficient value of the seismic energy rate inverse versus time. From the results of graph analysis, the precision of prediction time toward the real time of eruption vary between −2.86 up to 5.49 days.

  3. Using nonlinear kernels in seismic tomography: go beyond gradient methods

    NASA Astrophysics Data System (ADS)

    Wu, R.

    2013-05-01

    In quasi-linear inversion, a nonlinear problem is typically solved iteratively and at each step the nonlinear problem is linearized through the use of a linear functional derivative, the Fréchet derivative. Higher order terms generally are assumed to be insignificant and neglected. The linearization approach leads to the popular gradient method of seismic inversion. However, for the real Earth, the wave equation (and the real wave propagation) is strongly nonlinear with respect to the medium parameter perturbations. Therefore, the quasi-linear inversion may have a serious convergence problem for strong perturbations. In this presentation I will compare the convergence properties of the Taylor-Fréchet series and the renormalized Fréchet series, the De Wolf approximation, and illustrate the improved convergence property with numerical examples. I'll also discuss the application of nonlinear partial derivative to least-square waveform inversion. References: Bonnans, J., Gilbert, J., Lemarechal, C. and Sagastizabal, C., 2006, Numirical optmization, Springer. Wu, R.S. and Y. Zheng, 2012. Nonlinear Fréchet derivative and its De Wolf approximation, Expanded Abstracts of Society of Exploration Gephysicists, SI 8.1.

  4. Multiple attenuation to reflection seismic data using Radon filter and Wave Equation Multiple Rejection (WEMR) method

    SciTech Connect

    Erlangga, Mokhammad Puput

    2015-04-16

    Separation between signal and noise, incoherent or coherent, is important in seismic data processing. Although we have processed the seismic data, the coherent noise is still mixing with the primary signal. Multiple reflections are a kind of coherent noise. In this research, we processed seismic data to attenuate multiple reflections in the both synthetic and real seismic data of Mentawai. There are several methods to attenuate multiple reflection, one of them is Radon filter method that discriminates between primary reflection and multiple reflection in the τ-p domain based on move out difference between primary reflection and multiple reflection. However, in case where the move out difference is too small, the Radon filter method is not enough to attenuate the multiple reflections. The Radon filter also produces the artifacts on the gathers data. Except the Radon filter method, we also use the Wave Equation Multiple Elimination (WEMR) method to attenuate the long period multiple reflection. The WEMR method can attenuate the long period multiple reflection based on wave equation inversion. Refer to the inversion of wave equation and the magnitude of the seismic wave amplitude that observed on the free surface, we get the water bottom reflectivity which is used to eliminate the multiple reflections. The WEMR method does not depend on the move out difference to attenuate the long period multiple reflection. Therefore, the WEMR method can be applied to the seismic data which has small move out difference as the Mentawai seismic data. The small move out difference on the Mentawai seismic data is caused by the restrictiveness of far offset, which is only 705 meter. We compared the real free multiple stacking data after processing with Radon filter and WEMR process. The conclusion is the WEMR method can more attenuate the long period multiple reflection than the Radon filter method on the real (Mentawai) seismic data.

  5. Mapping of active faults based on the analysis of high-resolution seismic reflection profiles in offshore Montenegro

    NASA Astrophysics Data System (ADS)

    Vucic, Ljiljana; Glavatovic, Branislav

    2014-05-01

    High-resolution seismic-reflection data analysis is considered as important tool for mapping of active tectonic faults, since seismic exploration methods on varied scales can image subsurface structures of different depth ranges. Mapping of active faults for the offshore area of Montenegro is performed in Petrel software, using reflection database consist of 2D profiles in length of about 3.500 kilometers and 311 square kilometers of 3D seismics, acquired from 1979 to 2003. Montenegro offshore area is influenced by recent tectonic activity with numerous faults, folded faults and over trusts. Based on reflection profiles analysis, the trust fault system offshore Montenegro is reveled, parallel to the coast and extending up to 15 kilometers from the offshore line. Then, the system of normal top carbonate fault planes is mapped and characterized on the southern Adriatic, with NE trending. The tectonic interpretation of the seismic reflection profiles in Montenegro point toward the existence of principally reverse tectonic forms in the carbonate sediments, covered by young Quaternary sandy sediments of thickness 1-3 kilometers. Also, reflective seismic data indicate the active uplifting of evaporite dome on about 10 kilometers of coastline.

  6. Broadband seismic monitoring of active volcanoes using deterministic and stochastic approaches

    NASA Astrophysics Data System (ADS)

    Kumagai, H.; Nakano, M.; Maeda, T.; Yepes, H.; Palacios, P.; Ruiz, M. C.; Arrais, S.; Vaca, M.; Molina, I.; Yamashina, T.

    2009-12-01

    We systematically used two approaches to analyze broadband seismic signals observed at active volcanoes: one is waveform inversion of very-long-period (VLP) signals in the frequency domain assuming possible source mechanisms; the other is a source location method of long-period (LP) and tremor using their amplitudes. The deterministic approach of the waveform inversion is useful to constrain the source mechanism and location, but is basically only applicable to VLP signals with periods longer than a few seconds. The source location method uses seismic amplitudes corrected for site amplifications and assumes isotropic radiation of S waves. This assumption of isotropic radiation is apparently inconsistent with the hypothesis of crack geometry at the LP source. Using the source location method, we estimated the best-fit source location of a VLP/LP event at Cotopaxi using a frequency band of 7-12 Hz and Q = 60. This location was close to the best-fit source location determined by waveform inversion of the VLP/LP event using a VLP band of 5-12.5 s. The waveform inversion indicated that a crack mechanism better explained the VLP signals than an isotropic mechanism. These results indicated that isotropic radiation is not inherent to the source and only appears at high frequencies. We also obtained a best-fit location of an explosion event at Tungurahua when using a frequency band of 5-10 Hz and Q = 60. This frequency band and Q value also yielded reasonable locations for the sources of tremor signals associated with lahars and pyroclastic flows at Tungurahua. The isotropic radiation assumption may be valid in a high frequency range in which the path effect caused by the scattering of seismic waves results in an isotropic radiation pattern of S waves. The source location method may be categorized as a stochastic approach based on the nature of scattering waves. We further applied the waveform inversion to VLP signals observed at only two stations during a volcanic crisis

  7. Excavatability Assessment of Weathered Sedimentary Rock Mass Using Seismic Velocity Method

    SciTech Connect

    Bin Mohamad, Edy Tonnizam; Noor, Muhazian Md; Isa, Mohamed Fauzi Bin Md.; Mazlan, Ain Naadia; Saad, Rosli

    2010-12-23

    Seismic refraction method is one of the most popular methods in assessing surface excavation. The main objective of the seismic data acquisition is to delineate the subsurface into velocity profiles as different velocity can be correlated to identify different materials. The physical principal used for the determination of excavatability is that seismic waves travel faster through denser material as compared to less consolidated material. In general, a lower velocity indicates material that is soft and a higher velocity indicates more difficult to be excavated. However, a few researchers have noted that seismic velocity method alone does not correlate well with the excavatability of the material. In this study, a seismic velocity method was used in Nusajaya, Johor to assess the accuracy of this seismic velocity method with excavatability of the weathered sedimentary rock mass. A direct ripping run by monitoring the actual production of ripping has been employed at later stage and compared to the ripper manufacturer's recommendation. This paper presents the findings of the seismic velocity tests in weathered sedimentary area. The reliability of using this method with the actual rippability trials is also presented.

  8. Apollo 14 and 16 Active Seismic Experiments, and Apollo 17 Lunar Seismic Profiling

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Seismic refraction experiments were conducted on the moon by Apollo astronauts during missions 14, 16, and 17. Seismic velocities of 104, 108, 92, 114 and 100 m/sec were inferred for the lunar regolith at the Apollo 12, 14, 15, 16, and 17 landing sites, respectively. These data indicate that fragmentation and comminution caused by meteoroid impacts has produced a layer of remarkably uniform seismic properties moonwide. Brecciation and high porosity are the probable causes of the very low velocities observed in the lunar regolith. Apollo 17 seismic data revealed that the seismic velocity increases very rapidly with depth to 4.7 km/sec at a depth of 1.4 km. Such a large velocity change is suggestive of compositional and textural changes and is compatible with a model of fractured basaltic flows overlying anorthositic breccias. 'Thermal' moonquakes were also detected at the Apollo 17 site, becoming increasingly frequent after sunrise and reaching a maximum at sunset. The source of these quakes could possibly be landsliding.

  9. Evaluation of feasibility of mapping seismically active faults in Alaska

    NASA Technical Reports Server (NTRS)

    Gedney, L. D. (Principal Investigator); Vanwormer, J. D.

    1973-01-01

    The author has identified the following significant results. ERTS-1 imagery is proving to be exceptionally useful in delineating structural features in Alaska which have never been recognized on the ground. Previously unmapped features such as seismically active faults and major structural lineaments are especially evident. Among the more significant results of this investigation is the discovery of an active strand of the Denali fault. The new fault has a history of scattered activity and was the scene of a magnitude 4.8 earthquake on October 1, 1972. Of greater significance is the disclosure of a large scale conjugate fracture system north of the Alaska Range. This fracture system appears to result from compressive stress radiating outward from around Mt. McKinley. One member of the system was the scene of a magnitude 6.5 earthquake in 1968. The potential value of ERTS-1 imagery to land use planning is reflected in the fact that this earthquake occurred within 10 km of the site which was proposed for the Rampart Dam, and the fault on which it occurred passes very near the proposed site for the bridge and oil pipeline crossing of the Yukon River.

  10. Impacts of seismic activity on long-term repository performance at Yucca Mountain

    SciTech Connect

    Gauthier, J.H.; Wilson, M.L.; Borns, D.J.; Arnold, B.W.

    1995-12-31

    Several effects of seismic activity on the release of radionuclides from a potential repository at Yucca Mountain are quantified. Future seismic events are predicted using data from the seismic hazard analysis conducted for the Exploratory Studies Facility (ESF). Phenomenological models are developed, including rockfall (thermal-mechanical and seismic) in unbackfilled emplacement drifts, container damage caused by fault displacement within the repository, and flow-path chance caused by changes in strain. Using the composite-porosity flow model (relatively large-scale, regular percolation), seismic events show little effect on total-system releases; using the weeps flow model (episodic pulses of flow in locally saturated fractures), container damage and flow-path changes cause over an order of magnitude increase in releases. In separate calculations using, more realistic representations of faulting, water-table rise caused by seismically induced changes in strain are seen to be higher than previously estimated by others, but not sufficient to reach a potential repository.

  11. Seismically Articulating Kilauea Volcano's Active Conduits, Rift Zones, and Faults through HVO's Second Fifty Years

    NASA Astrophysics Data System (ADS)

    Okubo, P.; Nakata, J.; Klein, F.; Koyanagi, R.; Thelen, W.

    2011-12-01

    While seismic monitoring of active Hawaiian volcanoes began 100 years ago, the build-up of the U. S. Geological Survey's (USGS) Hawaiian Volcano Observatory (HVO) seismographic network to its current configuration began in 1955, when Jerry Eaton established remote stations that telemetered data via landline to recorders at HVO. With network expansion through the 1960's, earthquake location and cataloging capabilities have evolved to afford a computer processed seismic catalog now spanning fifty years. Location accuracy and catalog completeness to smaller magnitudes have increased. Research and insights developed using HVO's seismic record have exploited the ability to seismically monitor volcanic activity at depth, to identify active regions within the volcanoes on the basis of computed hypocentral locations, to infer regions of magma storage by recognizing different families of volcanic earthquakes, and to forecast volcanic activity in both short and longer term from seismicity patterns. HVO's seismicity catalog was central to calculations of probabilistic seismic hazards. The ability to develop and implement additional analytical and interpretive capabilities has kept pace with improvements in both field and laboratory hardware and software. While the basic capabilities continue as part of HVO's core monitoring, additional interpretive capabilities now include adding details of volcanic and earthquake source regions, and viewing seismic data in juxtaposition with other observatory data streams. As HVO looks to its next century of volcano studies, research and development continue to shape the future. Broadband seismic recording at HVO has enabled extensive study by Chouet, Dawson, and co-workers of the relationship of very-long-period seismic sources beneath Kilauea's summit caldera to magma supply and transport. Recent upgrades have improved the ability to use these data in seismic cataloging and research. Data processing upgrades have bolstered the ability to

  12. Assessing low-activity faults for the seismic safety of dams

    SciTech Connect

    Page, W.D.; Savage, W.U.; McLaren, M.K.

    1995-12-31

    Dams have been a familiar construct in the northern Sierra Nevada range in California (north of the San Joaquin River) since the forty-niners and farmers diverted water to their gold mines and farms in the mid 19th century. Today, more than 370 dams dot the region from the Central Valley to the eastern escarpment. Fifty-five more dam streams on the eastern slope. The dams are of all types: 240 earth fill; 56 concrete gravity; 45 rock and earth fills; 35 rock fill; 14 concrete arch; 9 hydraulic fill; and 29 various other types. We use the northern Sierra Nevada to illustrate the assessment of low-activity faults for the seismic safety of dams. The approach, techniques, and methods of evaluation are applicable to other regions characterized by low seismicity and low-activity faults having long recurrence intervals. Even though several moderate earthquakes had shaken the Sierra Nevada since 1849 (for example, the 1875 magnitude 5.8 Honey Lake and the 1909 magnitudes 5 and 5.5 Downieville earthquakes), seismic analyses for dams in the area generally were not performed prior to the middle of this century. Following the 1971 magnitude 6.7 San Fernando earthquake, when the hydraulic-fill Lower Van Norman Dam in southern California narrowly escaped catastrophic failure, the California Division of Safety of Dams and the Federal Energy Regulatory Commission required seismic safety to be addressed with increasing rigor. In 1975, the magnitude 5.7 Oroville earthquake on the Cleveland Hill fault near Oroville Dam in the Sierra Nevada foothills, showed convincingly that earthquakes and surface faulting could occur within the range. Following this event, faults along the ancient Foothills fault system have been extensively investigated at dam sites.

  13. Seismic activity monitoring in the Izvorul Muntelui dam region

    NASA Astrophysics Data System (ADS)

    Borleanu, Felix; Otilia Placinta, Anca; Popa, Mihaela; Adelin Moldovan, Iren; Popescu, Emilia

    2016-04-01

    Earthquakes occurrences near the artificial water reservoirs are caused by stress variation due to the weight of water, weakness of fractures or faults and increasing of pore pressure in crustal rocks. In the present study we aim to investigate how Izvorul Muntelui dam, located in the Eastern Carpathians influences local seismicity. For this purpose we selected from the seismic bulletins computed within National Data Center of National Institute for Earth Physics, Romania, crustal events occurred between 984 and 2015 in a range of 0.3 deg around the artificial lake. Subsequently to improve the seismic monitoring of the region we applied a cross-correlation detector on the continuous recordings of Bicaz (BIZ) seismic stations. Besides the tectonic events we detected sources within this region that periodically generate artificial evens. We couldn't emphasize the existence of a direct correlation between the water level variations and natural seismicity of the investigated area.

  14. Simplified method of deep-tow seismic profiling

    USGS Publications Warehouse

    Robb, James M.; Sylwester, Richard E.; Penton, Ronald

    1981-01-01

    To improve resolution of seismic-reflection profiles in continental slope water depths of 900 to 1500 m, a single hydrophone was towed about 150 m off the bottom to receive reflected signals from a surface-towed sparker sound source. That deep-towed hydrophone data show that valleys which appear V-shaped in records from a surface-towed hydrophone are flat-bottomed, and that subbottom reflections from an erosional unconformity can be much better resolved. The data produced by this technique are very hepful when used in conjunction with records from conventional surface-towed seismic-profiling equipment.

  15. Combined analysis of passive and active seismic measurements using additional geologic data for the determination of shallow subsurface structures

    NASA Astrophysics Data System (ADS)

    Horstmann, Tobias; Brüstle, Andrea; Spies, Thomas; Schlittenhardt, Jörg; Schmidt, Bernd

    2016-04-01

    A detailed knowledge of subsurface structure is essential for geotechnical projects and local seismic hazard analyses. Passive seismic methods like microtremor measurements are widely used in geotechnical practice, but limitations and developments are still in focus of scientific discussion. The presentation outlines microtremor measurements in the context of microzonation in the scale of districts or small communities. H/V measurements are used to identify zones with similar underground properties. Subsequently a shear wave velocity (Vs) depth profile for each zone is determined by array measurements at selected sites. To reduce possible uncertainties in dispersion curve analyses of passive array measurements and ambiguities within the inversion process, we conducted an additional active seismic experiment and included available geological information. The presented work is realized in the framework of the research project MAGS2 ("Microseismic Activity of Geothermal Systems") and deals with the determination of seismic hazard analysis at sites near deep geothermal power plants in Germany. The measurements were conducted in the Upper Rhine Graben (URG) and the Bavarian molasses, where geothermal power plants are in operation. The results of the H/V- and array-measurements in the region of Landau (URG) are presented and compared to known geological-tectonic structures. The H/V measurements show several zones with similar H/V-curves which indicate homogenous underground properties. Additionally to the passive seismic measurements an active refraction experiment was performed and evaluated using the MASW method („Multichannel Analysis of Surface Waves") to strengthen the determination of shear-wave-velocity depth profile. The dispersion curves for Rayleigh-waves of the active experiment support the Rayleigh-dispersion curves from passive measurements and therefore provide a valuable supplement. Furthermore, the Rayleigh-wave ellipticity was calculated to reduce

  16. 3D-seismic amplitude analysis of the sea floor: An important interpretive method for improved geohazards evaluations

    SciTech Connect

    Roberts, H.H.; Doyle, E.H.; Booth, J.R.; Clark, B.J.; Kaluza, M.J.; Hartsook, A.

    1996-12-31

    Evaluation of geohazards on the Louisiana continental slope using a combination of high-resolution acoustic data (standard geohazards survey data), 3D-seismic amplitude maps of the sea floor, and direct observation/sampling by a manned submersible reinforces the value of 3D-seismic amplitude data for feature identification. Amplitude extraction data from surface and near-surface horizons are valuable for establishing the links between high-resolution seismic signature and actual sea floor response, particularly in settings characterized by various types and rates of hydrocarbon venting/seepage. It was found that amplitude extraction data could accurately define the areas, configurations, and relative rates of hydrocarbon seepage (from anomaly strength and target size). In areas evaluated with 3D-seismic amplitude extraction data, this procedure provided a rapid method of identifying sites of hydrocarbon venting/seepage, their relative activities, and the likelihood of encountering sensitive chemosynthetic communities and other features such as mud vents, gas hydrate mounds, hardgrounds, and sizable buildups of authigenic carbonates. Results of this study support the value of using 3D-seismic amplitude extraction data for improving the understanding and predictability of the slope`s surface geology and seep-related benthic habitats.

  17. NRC-BNL BENCHMARK PROGRAM ON EVALUATION OF METHODS FOR SEISMIC ANALYSIS OF COUPLED SYSTEMS.

    SciTech Connect

    XU,J.

    1999-08-15

    A NRC-BNL benchmark program for evaluation of state-of-the-art analysis methods and computer programs for seismic analysis of coupled structures with non-classical damping is described. The program includes a series of benchmarking problems designed to investigate various aspects of complexities, applications and limitations associated with methods for analysis of non-classically damped structures. Discussions are provided on the benchmarking process, benchmark structural models, and the evaluation approach, as well as benchmarking ground rules. It is expected that the findings and insights, as well as recommendations from this program will be useful in developing new acceptance criteria and providing guidance for future regulatory activities involving licensing applications of these alternate methods to coupled systems.

  18. The performance of the stations of the Romanian seismic network in monitoring the local seismic activity

    NASA Astrophysics Data System (ADS)

    Ardeleanu, Luminita Angela; Neagoe, Cristian

    2014-05-01

    The seismic survey of the territory of Romania is mainly performed by the national seismic network operated by the National Institute for Earth Physics of Bucharest. After successive developments and upgrades, the network consists at present of 123 permanent stations equipped with high quality digital instruments (Kinemetrics K2, Quantera Q330, Quantera Q330HR, PS6-24 and Basalt digitizers) - 102 real time and 20 off-line stations - which cover the whole territory of the country. All permanent stations are supplied with 3 component accelerometers (episenzor type), while the real time stations are in addition provided with broadband (CMG3ESP, CMG40T, KS2000, KS54000, KS2000, CMG3T, STS2) or short period (SH-1, S13, Mark l4c, Ranger, GS21, L22_VEL) velocity sensors. Several communication systems are currently used for the real time data transmission: an analog line in UHF band, a line through GPRS (General Packet Radio Service), a dedicated line through satellite, and a dedicated line provided by the Romanian Special Telecommunication Service. During the period January 1, 2006 - June 30, 2013, 5936 shallow depth seismic events - earthquakes and quarry blasts - with local magnitude ML ≥ 1.2 were localized on the Romanian territory, or in its immediate vicinity, using the records of the national seismic network; 1467 subcrustal earthquakes (depth ≥ 60 km) with magnitude ML ≥ 1.9 were also localized in the Vrancea region, at the bend of the Eastern Carpathians. The goal of the present study is to evaluate the individual contribution of the real time seismic stations to the monitoring of the local seismicity. The performance of each station is estimated by taking into consideration the fraction of events that are localised using the station records, compared to the total number of events of the catalogue, occurred during the time of station operation. Taking into account the nonuniform space distribution of earthquakes, the location of the site and the recovery

  19. Seismic body wave separation in volcano-tectonic activity inferred by the Convolutive Independent Component Analysis

    NASA Astrophysics Data System (ADS)

    Capuano, Paolo; De Lauro, Enza; De Martino, Salvatore; Falanga, Mariarosaria; Petrosino, Simona

    2015-04-01

    One of the main challenge in volcano-seismological literature is to locate and characterize the source of volcano/tectonic seismic activity. This passes through the identification at least of the onset of the main phases, i.e. the body waves. Many efforts have been made to solve the problem of a clear separation of P and S phases both from a theoretical point of view and developing numerical algorithms suitable for specific cases (see, e.g., Küperkoch et al., 2012). Recently, a robust automatic procedure has been implemented for extracting the prominent seismic waveforms from continuously recorded signals and thus allowing for picking the main phases. The intuitive notion of maximum non-gaussianity is achieved adopting techniques which involve higher-order statistics in frequency domain., i.e, the Convolutive Independent Component Analysis (CICA). This technique is successful in the case of the blind source separation of convolutive mixtures. In seismological framework, indeed, seismic signals are thought as the convolution of a source function with path, site and the instrument response. In addition, time-delayed versions of the same source exist, due to multipath propagation typically caused by reverberations from some obstacle. In this work, we focus on the Volcano Tectonic (VT) activity at Campi Flegrei Caldera (Italy) during the 2006 ground uplift (Ciaramella et al., 2011). The activity was characterized approximately by 300 low-magnitude VT earthquakes (Md < 2; for the definition of duration magnitude, see Petrosino et al. 2008). Most of them were concentrated in distinct seismic sequences with hypocenters mainly clustered beneath the Solfatara-Accademia area, at depths ranging between 1 and 4 km b.s.l.. The obtained results show the clear separation of P and S phases: the technique not only allows the identification of the S-P time delay giving the timing of both phases but also provides the independent waveforms of the P and S phases. This is an enormous

  20. Effective methods for improving signal/noise ratio of seismic data collected from heavy noisy area

    SciTech Connect

    Chuankun, L. )

    1991-01-01

    This paper reports on the Jiyuan depression which is the hydrocarbon-bearing area discovered earliest in North China. Terribly complicated seismic-geological condition and very heavy multitudinous noises result in very low signal/noise ratio of seismic data in this area, which severely obstructed hydrocarbon exploration in this area. Hence, research of seismic methods for this area has been made systematically. Reasonable seismic data acquisition parameters were determined by making detailed surface-layer analysis and overall field tests, and by designing expert system with the use of spectral analysis data and field operation data. Consequently, special field method (including deep shot hole, big array length, high stacking fold and high low-cut filtering) was adopted to improve raw seismic data obviously. Furthermore, good static correction, correct stack velocity and reasonable prestack two-dimensional filtering were used to remove seismic noise in data processing. The above methods can improve signal/noise ratio and result in qualified seismic data which favor structural and lithologic interpretations.

  1. 2D Time-lapse Seismic Tomography Using An Active Time Constraint (ATC) Approach

    EPA Science Inventory

    We propose a 2D seismic time-lapse inversion approach to image the evolution of seismic velocities over time and space. The forward modeling is based on solving the eikonal equation using a second-order fast marching method. The wave-paths are represented by Fresnel volumes rathe...

  2. An evaluation of applicability of seismic refraction method in identifying shallow archaeological features A case study at archaeological site

    NASA Astrophysics Data System (ADS)

    Jahangardi, Morteza; Hafezi Moghaddas, Naser; Keivan Hosseini, Sayyed; Garazhian, Omran

    2015-04-01

    We applied the seismic refraction method at archaeological site, Tepe Damghani located in Sabzevar, NE of Iran, in order to determine the structures of archaeological interests. This pre-historical site has special conditions with respect to geographical location and geomorphological setting, so it is an urban archaeological site, and in recent years it has been used as an agricultural field. In spring and summer of 2012, the third season of archaeological excavation was carried out. Test trenches of excavations in this site revealed that cultural layers were often disturbed adversely due to human activities such as farming and road construction in recent years. Conditions of archaeological cultural layers in southern and eastern parts of Tepe are slightly better, for instance, in test trench 3×3 m²1S03, third test trench excavated in the southern part of Tepe, an adobe in situ architectural structure was discovered that likely belongs to cultural features of a complex with 5 graves. After conclusion of the third season of archaeological excavation, all of the test trenches were filled with the same soil of excavated test trenches. Seismic refraction method was applied with12 channels of P geophones in three lines with a geophone interval of 0.5 meter and a 1.5 meter distance between profiles on test trench 1S03. The goal of this operation was evaluation of applicability of seismic method in identification of archaeological features, especially adobe wall structures. Processing of seismic data was done with the seismic software, SiesImager. Results were presented in the form of seismic section for every profile, so that identification of adobe wall structures was achieved hardly. This could be due to that adobe wall had been built with the same materials of the natural surrounding earth. Thus, there is a low contrast and it has an inappropriate effect on seismic processing and identifying of archaeological features. Hence the result could be that application of

  3. On analysis-based two-step interpolation methods for randomly sampled seismic data

    NASA Astrophysics Data System (ADS)

    Yang, Pengliang; Gao, Jinghuai; Chen, Wenchao

    2013-02-01

    Interpolating the missing traces of regularly or irregularly sampled seismic record is an exceedingly important issue in the geophysical community. Many modern acquisition and reconstruction methods are designed to exploit the transform domain sparsity of the few randomly recorded but informative seismic data using thresholding techniques. In this paper, to regularize randomly sampled seismic data, we introduce two accelerated, analysis-based two-step interpolation algorithms, the analysis-based FISTA (fast iterative shrinkage-thresholding algorithm) and the FPOCS (fast projection onto convex sets) algorithm from the IST (iterative shrinkage-thresholding) algorithm and the POCS (projection onto convex sets) algorithm. A MATLAB package is developed for the implementation of these thresholding-related interpolation methods. Based on this package, we compare the reconstruction performance of these algorithms, using synthetic and real seismic data. Combined with several thresholding strategies, the accelerated convergence of the proposed methods is also highlighted.

  4. The Crustal Structure of the Eastern Tennessee Seismic Zone Imaged by means of Seismic Noise Tomography and Potential Fields Inversion Methods

    NASA Astrophysics Data System (ADS)

    Brandmayr, E.; Arroucau, P.; Kuponiyi, A.; Vlahovic, G.

    2015-12-01

    We investigate the crustal structure of the Eastern Tennessee Seismic Zone (ETSZ) by means of group velocity tomography maps from seismic noise data analysis and potential fields inversion with the located Euler deconvolution method. Preliminary tomography results show that, in the uppermost crust, the New York-Alabama (NY-AL) magnetic lineament surface projection represents the boundary between a low velocity anomaly to the NW of the lineament and a high velocity anomaly to the SE of it. The low velocity anomaly migrates towards SE with increasing depth, suggesting a possible SE dipping weak structure in which most of the seismic activity takes place. Inversion of magnetic field data shows that the top of the magnetic basement ranges between 5 and 10 km of depth in the Valley and the Ridge physiographic province while it is shallower (less than 2 km of depth) and locally outcropping in the Blue Ridge province and in the Cumberland Plateau province. The estimated depth of the top of the magnetic basement is in general agreement with existing sedimentary cover map of the broad study area, although the local features of the ETSZ presented in this work are not resolved by previous studies due to poor resolution. The correlation between the magnetic signature and the position of the seismic velocity anomalies support the interpretation of the low velocity zone as a major basement fault, trending NE-SW and juxtaposing Granite-Rhyolite basement to the NW from Grenville southern Appalachian basement to the SE, of which the NY-AL magnetic lineament is the projection on the surface. In order to better constrain our interpretation, inversion of tomography results to obtain absolute shear waves velocity models will be performed as a next step.

  5. Developing Advanced Seismic Imaging Methods For Characterizing the Fault Zone Structure

    NASA Astrophysics Data System (ADS)

    Zhang, Haijiang

    2015-04-01

    Here I present a series of recent developments on seismic imaging of fault zone structure. The goals of these advanced methods are to better determine the physical properties (including seismic velocity, attenuation, and anisotropy) around the fault zone and its boundaries. In order to accurately determine the seismic velocity structure of the fault zone, we have recently developed a wavelet-based double-difference seismic tomography method, in which the wavelet coefficients of the velocity model, rather than the model itself, are solved using both the absolute and differential arrival times. This method takes advantage of the multiscale nature of the velocity model and the multiscale wavelet representation property. Because of the velocity model is sparse in the wavelet domain, a sparsity constraint is applied to tomographic inversion. Compared to conventional tomography methods, the new method is both data- and model-adaptive, and thus can better resolve the fault zone structure. In addition to seismic velocity property of the fault zone, seismic anisotropy and attenuation properties are also important to characterize the fault zone structure. For this reason, we developed the seismic anisotropy tomography method to image the three-dimensional anisotropy strength model of the fault zone using shear wave splitting delay times between fast and slow shear waves. The applications to the San Andreas fault around Parkfield, California and north Anatolian fault in Turkey will be shown. To better constrain the seismic attenuation structure, we developed a new seismic attenuation tomography method using measured t* values for first arrival body waves, in which the structures of attenuation and velocity models are similar through the cross-gradient constraint. Seismic tomography can, however, only resolve the smooth variations in elastic properties in Earth's interior. To image structure at length scales smaller than what can be resolved tomographically, including

  6. Advancing New 3D Seismic Interpretation Methods for Exploration and Development of Fractured Tight Gas Reservoirs

    SciTech Connect

    James Reeves

    2005-01-31

    In a study funded by the U.S. Department of Energy and GeoSpectrum, Inc., new P-wave 3D seismic interpretation methods to characterize fractured gas reservoirs are developed. A data driven exploratory approach is used to determine empirical relationships for reservoir properties. Fractures are predicted using seismic lineament mapping through a series of horizon and time slices in the reservoir zone. A seismic lineament is a linear feature seen in a slice through the seismic volume that has negligible vertical offset. We interpret that in regions of high seismic lineament density there is a greater likelihood of fractured reservoir. Seismic AVO attributes are developed to map brittle reservoir rock (low clay) and gas content. Brittle rocks are interpreted to be more fractured when seismic lineaments are present. The most important attribute developed in this study is the gas sensitive phase gradient (a new AVO attribute), as reservoir fractures may provide a plumbing system for both water and gas. Success is obtained when economic gas and oil discoveries are found. In a gas field previously plagued with poor drilling results, four new wells were spotted using the new methodology and recently drilled. The wells have estimated best of 12-months production indicators of 2106, 1652, 941, and 227 MCFGPD. The latter well was drilled in a region of swarming seismic lineaments but has poor gas sensitive phase gradient (AVO) and clay volume attributes. GeoSpectrum advised the unit operators that this location did not appear to have significant Lower Dakota gas before the well was drilled. The other three wells are considered good wells in this part of the basin and among the best wells in the area. These new drilling results have nearly doubled the gas production and the value of the field. The interpretation method is ready for commercialization and gas exploration and development. The new technology is adaptable to conventional lower cost 3D seismic surveys.

  7. Site classification map for Tbilisi using seismic prospecting methods

    NASA Astrophysics Data System (ADS)

    Goguadze, Nino; Gventcadze, Aleko; Arabidze, Vakhtang; Tsereteli, Emil; Gaphrindashvili, Giorgi

    2013-04-01

    This aspect deserves major attention since it plays considerable role in the definition of the seismic impact to be considered in the design and retrofitting of structures. The most important parameter of soil maps of seismic site conditions, the shear wave velocity in the upper 30 m section of the ground (VS30) on regional scales are relatively rare since they require substantial investment in geological and geotechnical data acquisition and interpretation. Work presented here was initiated by working package wp5 of regional projects EMME (Earthquake Model for Middle East Region). In the frame of the project geophysical field work were done in some parts of Tbilisi. Seismic prospecting measurements were done along some profiles. In seismic= prospecting RAS-24 was used and obtained data is processed by Winsism V.12 (refraction analysis ). Second version of soil classification for Tbilisi city was done on the basis of new geo-engineering map of 1: 25 000 scales. For this the number of engineering-geological researches and generalization on the territory of Tbilisi were processed, All the Geological and Engineer-geological reports, that were collected and processed. Since in the geological reports less attention is paid to the genesis of the quaternary sediments and their lithological description, and in this regard the territory of Tbilisi is very difficult and multi-spectrum, it was necessary to conduct additional field surveys in 10 districts to specify information. Finely combining information that comes from seismoprospecting measurements and geo-engineering map the new site classification map expressed in Vs30 were derived for Tbilisi city.

  8. Structural design of active seismic isolation floor with a charging function

    NASA Astrophysics Data System (ADS)

    Nakakoji, Hayato; Miura, Nanako

    2016-04-01

    This study shows an optimum structure of a seismic isolation floor against horizontal ground motions. Although a seismic isolation floor is effective with vibration reduction, the response of the floor becomes larger when excited by long-period ground motions. It is shown that caster equipment move and suffer damage in a seismic isolation structure by an experiment. Moreover, the permissible displacement of the floor is limited. Therefore, the focus is on an active seismic isolation. About active control, the system cannot operate without power supply. To solve these problems an energy regeneration is considered in our previous study. These studies only analyze simple model and did not choose the suitable structure for active control and energy regeneration. This research propose a new structure which has regenerated energy exceeds the energy required for the active control by numerical simulation.

  9. A method for producing digital probabilistic seismic landslide hazard maps

    USGS Publications Warehouse

    Jibson, R.W.; Harp, E.L.; Michael, J.A.

    2000-01-01

    The 1994 Northridge, California, earthquake is the first earthquake for which we have all of the data sets needed to conduct a rigorous regional analysis of seismic slope instability. These data sets include: (1) a comprehensive inventory of triggered landslides, (2) about 200 strong-motion records of the mainshock, (3) 1:24 000-scale geologic mapping of the region, (4) extensive data on engineering properties of geologic units, and (5) high-resolution digital elevation models of the topography. All of these data sets have been digitized and rasterized at 10 m grid spacing using ARC/INFO GIS software on a UNIX computer. Combining these data sets in a dynamic model based on Newmark's permanent-deformation (sliding-block) analysis yields estimates of coseismic landslide displacement in each grid cell from the Northridge earthquake. The modeled displacements are then compared with the digital inventory of landslides triggered by the Northridge earthquake to construct a probability curve relating predicted displacement to probability of failure. This probability function can be applied to predict and map the spatial variability in failure probability in any ground-shaking conditions of interest. We anticipate that this mapping procedure will be used to construct seismic landslide hazard maps that will assist in emergency preparedness planning and in making rational decisions regarding development and construction in areas susceptible to seismic slope failure. ?? 2000 Elsevier Science B.V. All rights reserved.

  10. Phase-Shifted Based Numerical Method for Modeling Frequency-Dependent Effects on Seismic Reflections

    NASA Astrophysics Data System (ADS)

    Chen, Xuehua; Qi, Yingkai; He, Xilei; He, Zhenhua; Chen, Hui

    2016-04-01

    The significant velocity dispersion and attenuation has often been observed when seismic waves propagate in fluid-saturated porous rocks. Both the magnitude and variation features of the velocity dispersion and attenuation are frequency-dependent and related closely to the physical properties of the fluid-saturated porous rocks. To explore the effects of frequency-dependent dispersion and attenuation on the seismic responses, in this work, we present a numerical method for seismic data modeling based on the diffusive and viscous wave equation (DVWE), which introduces the poroelastic theory and takes into account diffusive and viscous attenuation in diffusive-viscous-theory. We derive a phase-shift wave extrapolation algorithm in frequencywavenumber domain for implementing the DVWE-based simulation method that can handle the simultaneous lateral variations in velocity, diffusive coefficient and viscosity. Then, we design a distributary channels model in which a hydrocarbon-saturated sand reservoir is embedded in one of the channels. Next, we calculated the synthetic seismic data to analytically and comparatively illustrate the seismic frequency-dependent behaviors related to the hydrocarbon-saturated reservoir, by employing DVWE-based and conventional acoustic wave equation (AWE) based method, respectively. The results of the synthetic seismic data delineate the intrinsic energy loss, phase delay, lower instantaneous dominant frequency and narrower bandwidth due to the frequency-dependent dispersion and attenuation when seismic wave travels through the hydrocarbon-saturated reservoir. The numerical modeling method is expected to contribute to improve the understanding of the features and mechanism of the seismic frequency-dependent effects resulted from the hydrocarbon-saturated porous rocks.

  11. Phase-Shifted Based Numerical Method for Modeling Frequency-Dependent Effects on Seismic Reflections

    NASA Astrophysics Data System (ADS)

    Chen, Xuehua; Qi, Yingkai; He, Xilei; He, Zhenhua; Chen, Hui

    2016-08-01

    The significant velocity dispersion and attenuation has often been observed when seismic waves propagate in fluid-saturated porous rocks. Both the magnitude and variation features of the velocity dispersion and attenuation are frequency-dependent and related closely to the physical properties of the fluid-saturated porous rocks. To explore the effects of frequency-dependent dispersion and attenuation on the seismic responses, in this work, we present a numerical method for seismic data modeling based on the diffusive and viscous wave equation (DVWE), which introduces the poroelastic theory and takes into account diffusive and viscous attenuation in diffusive-viscous-theory. We derive a phase-shift wave extrapolation algorithm in frequencywavenumber domain for implementing the DVWE-based simulation method that can handle the simultaneous lateral variations in velocity, diffusive coefficient and viscosity. Then, we design a distributary channels model in which a hydrocarbon-saturated sand reservoir is embedded in one of the channels. Next, we calculated the synthetic seismic data to analytically and comparatively illustrate the seismic frequency-dependent behaviors related to the hydrocarbon-saturated reservoir, by employing DVWE-based and conventional acoustic wave equation (AWE) based method, respectively. The results of the synthetic seismic data delineate the intrinsic energy loss, phase delay, lower instantaneous dominant frequency and narrower bandwidth due to the frequency-dependent dispersion and attenuation when seismic wave travels through the hydrocarbon-saturated reservoir. The numerical modeling method is expected to contribute to improve the understanding of the features and mechanism of the seismic frequency-dependent effects resulted from the hydrocarbon-saturated porous rocks.

  12. Development of a multi-scale seismic imaging method and its application to Newberry volcano

    NASA Astrophysics Data System (ADS)

    Heath, B.; Toomey, D. R.; Hooft, E. E.; Bezada, M. J.

    2013-12-01

    While some shallow magma reservoirs beneath land volcanoes have been seismically imaged, our understanding of their mid-to lower-crustal magma plumbing systems remains limited. Active source techniques allow for optimizing source geometry to image shallow crustal magmatic systems, but typically do not resolve depths greater than ~6-10 km, since the velocity gradient in the mid-to lower crust limits the energy that turns at these depths. For closely spaced seismic stations, teleseismic data provide constraints on deeper crustal heterogeneity, particularly its lateral variation. On the other hand, teleseismic studies do not resolve vertical variations in crustal structure well because their ray paths are almost vertical, which results in limited crossing rays within the crust. Furthermore, due to the generally lower frequency content of teleseismic arrivals, these data primarily image longer wavelength heterogeneity. Here we develop a multi-scale seismic imaging method that combines high-frequency active source data with lower frequency teleseismic data, and test its usefulness for imaging the crustal structure beneath Newberry Volcano in central Oregon. To constrain the P wave structure throughout the crust, we develop an iterative method that includes 3-D sensitivity kernels and 3-D raytracing. The use of sensitivity kernels provides a physically motivated method that accounts for the different resolving capability of teleseismic and active source data. Various approximations to the sensitivity kernel are explored, with the goal of maximizing both computational efficiency and inversion accuracy. 3-D raytracing determines an accurate ray path, which is important in the highly heterogeneous crust. We verify our approach with synthetic data calculated using finite difference waveform modeling. We discuss our inversion results and our ability to resolve the velocity structure throughout the crust. We will investigate the presence of high and low velocity regions that

  13. Issues Related to Seismic Activity Induced by the Injection of CO2 in Deep Saline Aquifers

    SciTech Connect

    Sminchak, Joel; Gupta, Neeraj; Byrer, Charles; Bergman, Perry

    2001-05-31

    Case studies, theory, regulation, and special considerations regarding the disposal of carbon dioxide (CO2) into deep saline aquifers were investigated to assess the potential for induced seismic activity. Formations capable of accepting large volumes of CO2 make deep well injection of CO2 an attractive option. While seismic implications must be considered for injection facilities, induced seismic activity may be prevented through proper siting, installation, operation, and monitoring. Instances of induced seismic activity have been documented at hazardous waste disposal wells, oil fields, and other sites. Induced seismic activity usually occurs along previously faulted rocks and may be investigated by analyzing the stress conditions at depth. Seismic events are unlikely to occur due to injection in porous rocks unless very high injection pressures cause hydraulic fracturing. Injection wells in the United States are regulated through the Underground Injection Control (UIC) program. UIC guidance requires an injection facility to perform extensive characterization, testing, and monitoring. Special considerations related to the properties of CO2 may have seismic ramifications to a deep well injection facility. Supercritical CO2 liquid is less dense than water and may cause density-driven stress conditions at depth or interact with formation water and rocks, causing a reduction in permeability and pressure buildup leading to seismic activity. Structural compatibility, historical seismic activity, cases of seismic activity triggered by deep well injection, and formation capacity were considered in evaluating the regional seismic suitability in the United States. Regions in the central, midwestern, and southeastern United States appear best suited for deep well injection. In Ohio, substantial deep well injection at a waste disposal facility has not caused seismic events in a seismically active area. Current

  14. Seismic Activity at Vailulu'u, Samoa's Youngest Volcano

    NASA Astrophysics Data System (ADS)

    Konter, J.; Staudigel, H.; Hart, S.

    2002-12-01

    Submarine volcanic systems, as a product of the Earth's mantle, play an essential role in the Earth's heat budget and in the interaction between the solid Earth and the hydrosphere and biosphere. Their eruptive and intrusive activity exerts an important control on these hydrothermal systems. In March 2000, we deployed an array of five ocean bottom hydrophones (OBH) on the summit region (625-995 m water depth) of Vailulu'u Volcano (14°12.9'S;169°03.5'W); this volcano represents the active end of the Samoan hotspot chain and is one of only a few well-studied intra-plate submarine volcanoes. We monitored seismic activity for up to 12 months at low sample rate (25 Hz), and for shorter times at a higher sample rate (125 Hz). We have begun to catalogue and locate a variety of acoustic events from this network. Ambient ocean noise was filtered out by a 4th-order Butterworth bandpass filter (2.3 - 10 Hz). We distinguish small local earthquakes from teleseismic activity, mostly identified by T- (acoustic) waves, by comparison with a nearby GSN station (AFI). Most of the detected events are T-phases from teleseismic earthquakes, characterized by their emergent coda and high frequency content (up to 30 Hz); the latter distinguishes them from low frequency emergent signals associated with the volcano (e.g. tremor). A second type of event is characterized by impulsive arrivals, with coda lasting a few seconds. The differences in arrival times between stations on the volcano are too small for these events to be T-waves; they are very likely to be local events, since the GSN station in Western Samoa (AFI) shows no arrivals close in time to these events. Preliminary locations show that these small events occur approximately once per day and are located within the volcano (the 95% confidence ellipse is similar to the size of the volcano, due to the small size of the OBH network). Several events are located relatively close to each other (within a km radius) just NW of the crater.

  15. Seismic hazard of American Samoa and neighboring South Pacific Islands--methods, data, parameters, and results

    USGS Publications Warehouse

    Petersen, Mark D.; Harmsen, Stephen C.; Rukstales, Kenneth S.; Mueller, Charles S.; McNamara, Daniel E.; Luco, Nicolas; Walling, Melanie

    2012-01-01

    American Samoa and the neighboring islands of the South Pacific lie near active tectonic-plate boundaries that host many large earthquakes which can result in strong earthquake shaking and tsunamis. To mitigate earthquake risks from future ground shaking, the Federal Emergency Management Agency requested that the U.S. Geological Survey prepare seismic hazard maps that can be applied in building-design criteria. This Open-File Report describes the data, methods, and parameters used to calculate the seismic shaking hazard as well as the output hazard maps, curves, and deaggregation (disaggregation) information needed for building design. Spectral acceleration hazard for 1 Hertz having a 2-percent probability of exceedance on a firm rock site condition (Vs30=760 meters per second) is 0.12 acceleration of gravity (1 second, 1 Hertz) and 0.32 acceleration of gravity (0.2 seconds, 5 Hertz) on American Samoa, 0.72 acceleration of gravity (1 Hertz) and 2.54 acceleration of gravity (5 Hertz) on Tonga, 0.15 acceleration of gravity (1 Hertz) and 0.55 acceleration of gravity (5 Hertz) on Fiji, and 0.89 acceleration of gravity (1 Hertz) and 2.77 acceleration of gravity (5 Hertz) on the Vanuatu Islands.

  16. Equivalence of the virtual-source method and wave-field deconvolution in seismic interferometry.

    PubMed

    Snieder, Roel; Sheiman, Jon; Calvert, Rodney

    2006-06-01

    Seismic interferometry and the virtual-source method are related approaches for extracting the Green's function that accounts for wave propagation between receivers by making suitable combinations of the waves recorded at these two receivers. These waves can either be excited by active, controlled, sources, or by natural incoherent sources. We compare this technique with the deconvolution of the wave field recorded at different receivers. We show that the deconvolved wave field is a solution of the same wave equation as that for the physical system, but that the deconvolved wave forms may satisfy different boundary conditions than those of the original system. We apply this deconvolution approach to the wave motion recorded at various levels in a building after an earthquake, and show how to extract the building response for different boundary conditions. Extracting the response of the system with different boundary conditions can be used to enhance, or suppress, the normal-mode response. In seismic exploration this principle can be used for the suppression of surface-related multiples. PMID:16907010

  17. Soft computing analysis of the possible correlation between temporal and energy release patterns in seismic activity

    NASA Astrophysics Data System (ADS)

    Konstantaras, Anthony; Katsifarakis, Emmanouil; Artzouxaltzis, Xristos; Makris, John; Vallianatos, Filippos; Varley, Martin

    2010-05-01

    This paper is a preliminary investigation of the possible correlation of temporal and energy release patterns of seismic activity involving the preparation processes of consecutive sizeable seismic events [1,2]. The background idea is that during periods of low-level seismic activity, stress processes in the crust accumulate energy at the seismogenic area whilst larger seismic events act as a decongesting mechanism releasing considerable energy [3,4]. A dynamic algorithm is being developed aiming to identify and cluster pre- and post- seismic events to the main earthquake following on research carried out by Zubkov [5] and Dobrovolsky [6,7]. This clustering technique along with energy release equations dependent on Richter's scale [8,9] allow for an estimate to be drawn regarding the amount of the energy being released by the seismic sequence. The above approach is being implemented as a monitoring tool to investigate the behaviour of the underlying energy management system by introducing this information to various neural [10,11] and soft computing models [1,12,13,14]. The incorporation of intelligent systems aims towards the detection and simulation of the possible relationship between energy release patterns and time-intervals among consecutive sizeable earthquakes [1,15]. Anticipated successful training of the imported intelligent systems may result in a real-time, on-line processing methodology [1,16] capable to dynamically approximate the time-interval between the latest and the next forthcoming sizeable seismic event by monitoring the energy release process in a specific seismogenic area. Indexing terms: pattern recognition, long-term earthquake precursors, neural networks, soft computing, earthquake occurrence intervals References [1] Konstantaras A., Vallianatos F., Varley M.R. and Makris J. P.: ‘Soft computing modelling of seismicity in the southern Hellenic arc', IEEE Geoscience and Remote Sensing Letters, vol. 5 (3), pp. 323-327, 2008 [2] Eneva M. and

  18. Soft computing analysis of the possible correlation between temporal and energy release patterns in seismic activity

    NASA Astrophysics Data System (ADS)

    Konstantaras, Anthony; Katsifarakis, Emmanouil; Artzouxaltzis, Xristos; Makris, John; Vallianatos, Filippos; Varley, Martin

    2010-05-01

    This paper is a preliminary investigation of the possible correlation of temporal and energy release patterns of seismic activity involving the preparation processes of consecutive sizeable seismic events [1,2]. The background idea is that during periods of low-level seismic activity, stress processes in the crust accumulate energy at the seismogenic area whilst larger seismic events act as a decongesting mechanism releasing considerable energy [3,4]. A dynamic algorithm is being developed aiming to identify and cluster pre- and post- seismic events to the main earthquake following on research carried out by Zubkov [5] and Dobrovolsky [6,7]. This clustering technique along with energy release equations dependent on Richter's scale [8,9] allow for an estimate to be drawn regarding the amount of the energy being released by the seismic sequence. The above approach is being implemented as a monitoring tool to investigate the behaviour of the underlying energy management system by introducing this information to various neural [10,11] and soft computing models [1,12,13,14]. The incorporation of intelligent systems aims towards the detection and simulation of the possible relationship between energy release patterns and time-intervals among consecutive sizeable earthquakes [1,15]. Anticipated successful training of the imported intelligent systems may result in a real-time, on-line processing methodology [1,16] capable to dynamically approximate the time-interval between the latest and the next forthcoming sizeable seismic event by monitoring the energy release process in a specific seismogenic area. Indexing terms: pattern recognition, long-term earthquake precursors, neural networks, soft computing, earthquake occurrence intervals References [1] Konstantaras A., Vallianatos F., Varley M.R. and Makris J. P.: ‘Soft computing modelling of seismicity in the southern Hellenic arc', IEEE Geoscience and Remote Sensing Letters, vol. 5 (3), pp. 323-327, 2008 [2] Eneva M. and

  19. Trace Gases - A Warning Signs of Impending Major Seismic Activity

    NASA Astrophysics Data System (ADS)

    Baijnath, J.; Freund, F.; Li, J.

    2013-12-01

    Seismological models can predict future earthquakes only with wide uncertainty windows, typically on the order of decades to centuries. To improve short-term earthquake forecasts, it is essential to understand the non-seismic processes that take place in Earth's crust during the build-up of tectonic stresses. Days prior to the January 2001 M 7.6 Gujurat earthquake in India, there was a significant increase in the regional CO concentration, reaching 240 ppbv over a 100 squared kilometers, as derived from data of the MOPITT sensor onboard the NASA Terra satellite. A possible explanation for these observations is that when stresses in Earth's crust are building, positive hole charge carriers are activated, which are highly mobile and spread from deep below the earth to the surface. Positive holes act as highly oxidizing oxygen radicals, oxidizing water to hydrogen peroxide. It is hypothesized that, as positive hole charge carriers arrive from below and traverse the soil, they are expected to oxidize soil organics, converting aliphatics to ketones, formaldehyde, CO and CO2. This is tested by using a closed chamber with a slab of gabbro rock. Ultrasound generated by a pair of 50 W, 40 kHz piezoelectric transducers, applied to one end of the gabbro slab was used to activate the positive holes. This created a high concentration of positive holes at the end of the rock that the electrical conductivity through the rock increased more than 1000-fold, while the increase in conductivity through the other end of the gabbro slab was on the order of 100-fold. On the other end of the slab, rock dust and various soils were placed. A stainless steel mesh was also placed over the soil and dust to allow a current to flow through the granular material. When the far end of the slab was subjected to the ultrasound, currents as large as 250 nA were recorded flowing through the length of the gabbro slab and through the dust/soil pile. Dry dust/soil and dust samples impregnated with

  20. Improving the Detectability of the Catalan Seismic Network for Local Seismic Activity Monitoring

    NASA Astrophysics Data System (ADS)

    Jara, Jose Antonio; Frontera, Tànit; Batlló, Josep; Goula, Xavier

    2016-04-01

    The seismic survey of the territory of Catalonia is mainly performed by the regional seismic network operated by the Cartographic and Geologic Institute of Catalonia (ICGC). After successive deployments and upgrades, the current network consists of 16 permanent stations equipped with 3 component broadband seismometers (STS2, STS2.5, CMG3ESP and CMG3T), 24 bits digitizers (Nanometrics Trident) and VSAT telemetry. Data are continuously sent in real-time via Hispasat 1D satellite to the ICGC datacenter in Barcelona. Additionally, data from other 10 stations of neighboring areas (Spain, France and Andorra) are continuously received since 2011 via Internet or VSAT, contributing both to detect and to locate events affecting the region. More than 300 local events with Ml ≥ 0.7 have been yearly detected and located in the region. Nevertheless, small magnitude earthquakes, especially those located in the south and south-west of Catalonia may still go undetected by the automatic detection system (DAS), based on Earthworm (USGS). Thus, in order to improve the detection and characterization of these missed events, one or two new stations should be installed. Before making the decision about where to install these new stations, the performance of each existing station is evaluated taking into account the fraction of detected events using the station records, compared to the total number of events in the catalogue, occurred during the station operation time from January 1, 2011 to December 31, 2014. These evaluations allow us to build an Event Detection Probability Map (EDPM), a required tool to simulate EDPMs resulting from different network topology scenarios depending on where these new stations are sited, and becoming essential for the decision-making process to increase and optimize the event detection probability of the seismic network.

  1. Technology of research of hydroturbine unit work using seismic methods

    NASA Astrophysics Data System (ADS)

    Seleznev, V. S.; Liseikin, A. V.; Gromyko, P. V.; Soloviev, V. M.

    2013-05-01

    On August, 17, 2009 one of the most significant accident in hydropower engineering was happened at Sayano-Shushenskaya Hydroelectric Power Station. Specialists of Geophysical Survey SB RAS took part in the State Committee on investigation of the accident cause at Sayano-Shushenskaya HPS. It was determined, that the cause of the accident was a break of stud-bolts on the turbine cover. Why stud-bolts did not stand a load? There were assumptions that hydraulic shock provoked the accident. But, if it is so, seismic station "Cheremushky", situated in 4 km away from the HPS, should has a record of this event. First of all, investigating the record, got at the seismic station in the moment of the accident, it was determined that strength of seismic waves, recorded at the moment of the accident, did not exceed strength of waves got at trotyl explosion of 500 g at a distance to 4 km. The version of hydraulic shock was not proved. There were distinguished low-frequency oscillations and it was determined that the hydroturbine unit (HU) had been raised up more then 10 m in height for 10 sec. Analyzing the seismic station records during the period of more than a year before the accident and records of operating modes of different HU, there was determined that oscillations radiated by second (damaged) HU were approximately 1.5 times more intense than oscillations from all other HU. After the accident at Sayano-Shushenskaya HPS hydroturbine units were started in turns: at first there were started hydroturbine units of old construction (3, 4, 5, 6), then HP of new construction (1, 7, 8, 9). We installed 10 - 15 three-component seismic stations in different points around a HU and studied field of seismic oscillations from it's work. It was determined, that HU radiates a set of monochromatic oscillations divisible by speed of rotation equal to 2.381 Hz. Change of these signals amplitude is connected with change of HU operation modes. Research of changes in oscillations spectral

  2. The 2013 earthquake swarm in Helike, Greece: seismic activity at the root of old normal faults

    NASA Astrophysics Data System (ADS)

    Kapetanidis, V.; Deschamps, A.; Papadimitriou, P.; Matrullo, E.; Karakonstantis, A.; Bozionelos, G.; Kaviris, G.; Serpetsidaki, A.; Lyon-Caen, H.; Voulgaris, N.; Bernard, P.; Sokos, E.; Makropoulos, K.

    2015-09-01

    The Corinth Rift in Central Greece has been studied extensively during the past decades, as it is one of the most seismically active regions in Europe. It is characterized by normal faulting and extension rates between 6 and 15 mm yr-1 in an approximately N10E° direction. On 2013 May 21, an earthquake swarm was initiated with a series of small events 4 km southeast of Aigion city. In the next days, the seismic activity became more intense, with outbursts of several stronger events of magnitude between 3.3 and 3.7. The seismicity migrated towards the east during June, followed by a sudden activation of the western part of the swarm on July 15th. More than 1500 events have been detected and manually analysed during the period between 2013 May 21 and August 31, using over 15 local stations in epicentral distances up to 30 km and a local velocity model determined by an error minimization method. Waveform similarity-based analysis was performed, revealing several distinct multiplets within the earthquake swarm. High-resolution relocation was applied using the double-difference algorithm HypoDD, incorporating both catalogue and cross-correlation differential traveltime data, which managed to separate the initial seismic cloud into several smaller, densely concentrated spatial clusters of strongly correlated events. Focal mechanism solutions for over 170 events were determined using P-wave first motion polarities, while regional waveform modelling was applied for the calculation of moment tensors for the 18 largest events of the sequence. Selected events belonging to common spatial groups were considered for the calculation of composite mechanisms to characterize different parts of the swarm. The solutions are mainly in agreement with the regional NNE-SSW extension, representing typical normal faulting on 30-50° north-dipping planes, while a few exhibit slip in an NNE-SSW direction, on a roughly subhorizontal plane. Moment magnitudes were calculated by spectral analysis

  3. Integration of seismic methods with reservoir simulation, Pikes Peak heavy oil field, Saskatchewan

    NASA Astrophysics Data System (ADS)

    Zou, Ying

    The Pikes Peak heavy oil field has been operated by Husky Energy Ltd since 1981. Steam injection has been successfully employed to increase production. Efforts in geophysics and reservoir engineering have been made to improve interpretations in the mapping of reservoir conditions. This dissertation developed tools and a working flow for integrating the analysis of time-lapse seismic surveys with reservoir simulation, and applied them to the Pikes Peak field. Two time-lapse 2D seismic lines acquired in February 1991 and March 2000 in the eastern part of the field were carefully processed to produce wavelet and structure matched final sections. Reservoir simulation based on the field reservoir production history was carried out. It provided independent complementary information for the time-lapse seismic analysis. A rock physics procedure based on Gassmann's equation and Batzle and Wang's empirical relationship successfully linked the reservoir engineering to the seismic method. Based on the resultant seismic models, synthetic seismic sections were generated as the analogy of field seismic sections. The integrated interpretation for the Pikes Peak reservoir drew the following conclusions: The areas with a gas saturation difference, between two compared time steps, have seismic differences. Thicker gas zones correspond with large reflectivity changes on the top of the reservoir and larger traveltime delays in the seismic section. The thin gas zones only induce large reflectivity changes on the top of the reservoir, and do not have large time delays below the reservoir zone. High temperature regions also correlate with areas having large seismic energy differences. High temperature with thick gas (steam and methane) zones may be evidence for steam existence. The seismic differences at locations far from the production zone are due to the lower pressure that causes solution gas to evolve from the oil. Pressure changes propagate much faster (˜20 m in one month) than

  4. The Indirect Boundary Element Method (IBEM) for Seismic Response of Topographical Irregularities in Layered Media

    NASA Astrophysics Data System (ADS)

    Contreras Zazueta, M. A.; Perton, M.; Sanchez-Sesma, F. J.; Sánchez-Alvaro, E.

    2013-12-01

    The seismic hazard assessment of extended developments, such as a dam, a bridge or a pipeline, needs the strong ground motion simulation taking into account the effects of surface geology. In many cases the incoming wave field can be obtained from attenuation relations or simulations for layered media using Discrete Wave Number (DWN). Sometimes there is a need to include in simulations the seismic source as well. A number of methods to solve these problems have been developed. Among them the Finite Element and Finite Difference Methods (FEM and FDM) are generally preferred because of the facility of use. Nevertheless, the analysis of realistic dynamic loading induced by earthquakes requires a thinner mesh of the entire domain to consider high frequencies. Consequently this may imply a high computational cost. The Indirect Boundary Element Method (IBEM) can also be employed. Here it is used to study the response of a site to historical seismic activity. This method is particularly suited to model wave propagation through wide areas as it requires only the meshing of boundaries. Moreover, it is well suited to represent finely the diffraction that can occur on a fault. However, the IBEM has been applied mainly to simple geometrical configurations. In this communication significant refinements of the formulation are presented. Using IBEM we can simulate wave propagation in complex geometrical configurations such as a stratified medium crossed by thin faults or having a complex topography. Two main developments are here described; one integrates the DWN method inside the IBEM in order to represent the Green's functions of stratified media with relatively low computational cost but assuming unbounded parallel flat layers, and the other is the extension of IBEM to deal with multi-regions in contact which allows more versatility with a higher computational cost compared to the first one but still minor to an equivalent FEM formulation. The two approaches are fully

  5. Seismic Studies

    SciTech Connect

    R. Quittmeyer

    2006-09-25

    This technical work plan (TWP) describes the efforts to develop and confirm seismic ground motion inputs used for preclosure design and probabilistic safety 'analyses and to assess the postclosure performance of a repository at Yucca Mountain, Nevada. As part of the effort to develop seismic inputs, the TWP covers testing and analyses that provide the technical basis for inputs to the seismic ground-motion site-response model. The TWP also addresses preparation of a seismic methodology report for submission to the U.S. Nuclear Regulatory Commission (NRC). The activities discussed in this TWP are planned for fiscal years (FY) 2006 through 2008. Some of the work enhances the technical basis for previously developed seismic inputs and reduces uncertainties and conservatism used in previous analyses and modeling. These activities support the defense of a license application. Other activities provide new results that will support development of the preclosure, safety case; these results directly support and will be included in the license application. Table 1 indicates which activities support the license application and which support licensing defense. The activities are listed in Section 1.2; the methods and approaches used to implement them are discussed in more detail in Section 2.2. Technical and performance objectives of this work scope are: (1) For annual ground motion exceedance probabilities appropriate for preclosure design analyses, provide site-specific seismic design acceleration response spectra for a range of damping values; strain-compatible soil properties; peak motions, strains, and curvatures as a function of depth; and time histories (acceleration, velocity, and displacement). Provide seismic design inputs for the waste emplacement level and for surface sites. Results should be consistent with the probabilistic seismic hazard analysis (PSHA) for Yucca Mountain and reflect, as appropriate, available knowledge on the limits to extreme ground motion at

  6. Seismic small-scale discontinuity sparsity-constraint inversion method using a penalty decomposition algorithm

    NASA Astrophysics Data System (ADS)

    Zhao, Jingtao; Peng, Suping; Du, Wenfeng

    2016-02-01

    We consider sparsity-constraint inversion method for detecting seismic small-scale discontinuities, such as edges, faults and cavities, which provide rich information about petroleum reservoirs. However, where there is karstification and interference caused by macro-scale fault systems, these seismic small-scale discontinuities are hard to identify when using currently available discontinuity-detection methods. In the subsurface, these small-scale discontinuities are separately and sparsely distributed and their seismic responses occupy a very small part of seismic image. Considering these sparsity and non-smooth features, we propose an effective L 2-L 0 norm model for improvement of their resolution. First, we apply a low-order plane-wave destruction method to eliminate macro-scale smooth events. Then, based the residual data, we use a nonlinear structure-enhancing filter to build a L 2-L 0 norm model. In searching for its solution, an efficient and fast convergent penalty decomposition method is employed. The proposed method can achieve a significant improvement in enhancing seismic small-scale discontinuities. Numerical experiment and field data application demonstrate the effectiveness and feasibility of the proposed method in studying the relevant geology of these reservoirs.

  7. A comparison of methods to estimate seismic phase delays: numerical examples for coda wave interferometry

    NASA Astrophysics Data System (ADS)

    Mikesell, T. Dylan; Malcolm, Alison E.; Yang, Di; Haney, Matthew M.

    2015-07-01

    Time-shift estimation between arrivals in two seismic traces before and after a velocity perturbation is a crucial step in many seismic methods. The accuracy of the estimated velocity perturbation location and amplitude depend on this time shift. Windowed cross-correlation and trace stretching are two techniques commonly used to estimate local time shifts in seismic signals. In the work presented here we implement Dynamic Time Warping (DTW) to estimate the warping function - a vector of local time shifts that globally minimizes the misfit between two seismic traces. We compare all three methods using acoustic numerical experiments. We show that DTW is comparable to or better than the other two methods when the velocity perturbation is homogeneous and the signal-to-noise ratio is high. When the signal-to-noise ratio is low, we find that DTW and windowed cross-correlation are more accurate than the stretching method. Finally, we show that the DTW algorithm has good time resolution when identifying small differences in the seismic traces for a model with an isolated velocity perturbation. These results impact current methods that utilize not only time shifts between (multiply) scattered waves, but also amplitude and decoherence measurements.

  8. Seismic wave generation systems and methods for cased wells

    DOEpatents

    Minto, James; Sorrells, Martin H; Owen, Thomas E.; Schroeder, Edgar C.

    2011-03-29

    A vibration source (10) includes an armature bar (12) having a major length dimension, and a driver (20A) positioned about the armature bar. The driver (20A) is movably coupled to the armature bar (12), and includes an electromagnet (40). During operation the electromagnet (40) is activated such that the driver (20A) moves with respect to the armature bar (12) and a vibratory signal is generated in the armature bar. A described method for generating a vibratory signal in an object includes positioning the vibration source (10) in an opening of the object, coupling the armature bar (12) to a surface of the object within the opening, and activating the electromagnet (40) of the driver (20A) such that the driver moves with respect to the armature bar (12) and a vibratory signal is generated in the armature bar and the object.

  9. A new varied continuation step method in seismic migration by phase shift plus interpolation

    SciTech Connect

    Guotian, T. )

    1992-01-01

    In this paper the principle of wave equation migration using phase shift plus interpolation is described briefly. Wave field extrapolation formula in such migration and final imaging equation are properly modified, with downward extrapolation operator redefined, so that the imaging can be achieved by using fast Fourier transform (FFT). A new varied continuation step method is given which is different from usual one in time domain. The new method, which is different from usual varied continuation step method for time domain interpolation in phase shift plus interpolation migration, uses the downward extrapolation continuation step much longer than a quarter of an apparent wave length; therefore, the efficiency of such seismic migration is improved satisfactorily. The processing results of theoretical model, coal field and high dip seismic data show that this new method is a f-k domain migration technique which is economic and suitable to the seismic data collected from the area where there are high dip formations and complicated geological structures.

  10. Geomorphological features of active tectonics and ongoing seismicity of northeastern Kumaun Himalaya, Uttarakhand, India

    NASA Astrophysics Data System (ADS)

    Pathak, Vivekanand; Pant, Charu C.; Darmwal, Gopal Singh

    2015-08-01

    The northeastern part of Kumaun Lesser Himalaya, Uttarakhand, India, lying between the rupture zones of 1905, Kangra and 1934, Bihar-Nepal earthquakes and known as `central seismic gap' is a segment of an active fault known to produce significant earthquakes and has not slipped in an unusually long time when compared to other segments. The studied section forms a part of this seismic gap and is seismically an active segment of the Himalayan arc, as compared to the remaining part of the Kumaun Lesser Himalaya and it is evident by active geomorphological features and seismicity data. The geomorphological features of various river valley transects suggest that the region had a history of tectonic rejuvenation which is testified by the deposition of various levels of terraces and their relative uplift, shifting and ponding of river channels, uplifted potholes, triangular facets on fault planes, fault scarps, etc. Further, the seismic data of five-station digital telemetered seismic network along with two stand alone systems show the distribution of earthquakes in or along the analyzed fault transects. It is observed that the microseismic earthquakes (magnitude 1.0-3.0) frequently occur in the region and hypocenters of these earthquakes are confined to shallow depths (10-20 km), with low stress drop values (1.0-10 bar) and higher peak ground velocity (PGV). The cluster of events is observed in the region, sandwiched between the Berinag Thrust (BT) in south and Main Central Thrust (MCT) in north. The occurrences of shallow focus earthquakes and the surface deformational features in the different river valley transect indicates that the region is undergoing neotectonic rejuvenation. In absence of chronology of the deposits it is difficult to relate it with extant seismicity, but from the geomorphic and seismic observations it may be concluded that the region is still tectonically active. The information would be very important in identifying the areas of hazard prone and

  11. The seismic method in the search for oil and gas: Current techniques and future developments

    SciTech Connect

    Berkhout, A.J.

    1986-08-01

    In applying seismic echo techniques to oil and gas exploration, the underground is ''illuminated'' from the surface by acoustic waves. The incident wavefield is reflected at the geologic layer boundaries and is registered at the surface, yielding detailed information on earth's upper structure. An important aspect of the seismic method is that an unprocessed seismic image does not represent the actual picture. Each reflection has been distorted during its propagation through earth. These distortions have to be corrected before an accurate picture can be developed. This is in most cases accomplished by ''seismic inversion.'' In this paper, current seismic techniques for oil and gas search, and their further development, are reviewed, with emphasis on seismic inversion. It is shown that important new developments in theory, software, and hardware have yielded significant improvements in wave theory solutions. Most research results presented are general and apply equally well to other echo technique applications, such as ultrasonic medical imaging, nondestructive testing, acoustic microscopy, sonar, and ground radar.

  12. Volcanic activity observed from continuous seismic records in the region of the Klyuchevskoy group of volcanoes

    NASA Astrophysics Data System (ADS)

    Shapiro, N.; Droznin, D.; Droznina, S.; Senyukov, S.; Chebrov, V.; Gordeev, E.; Frank, W.

    2015-12-01

    We analyze continuous seismic records from 18 permanent stations operated in vicinity of the Klyuchevskoy group of volcanos (Kamchatka, Russia) during the period between 2009 and 2014. We explore the stability of the inter-station cross-correlation to detect different periods of sustained emission from seismic energy. The main idea of this approach is that cross-correlation waveforms computed from a wavefield emitted by a seismic source from a fixed position remain stable during the period when this source is acting. The detected periods of seismic emission correspond to different episodes of activity of volcanoes: Klyuchevskoy, Tolbachik, Shiveluch, and Kizimen. For Klyuchevskoy and Tolbachik whose recent eruptions are mostly effusive, the detected seismic signals correspond to typical volcanic tremor, likely caused by degassing processes. For Shiveluch and Kizimen producing more silicic lavas, the observed seismic emission often consists of many repetitive long period (LP) seismic events that might be related to the extrusion of viscous magmas. We develop an approach for automatic detection of these individual LP events in order to characterize variations of their size and recurrence in time.

  13. Multi-level continuous active source seismic monitoring (ML-CASSM): Application to shallow hydrofracture monitoring

    NASA Astrophysics Data System (ADS)

    Ajo Franklin, J. B.; Daley, T. M.; Butler-Veytia, B.; Peterson, J.; Gasperikova, E.; Hubbard, S. S.

    2010-12-01

    Induced subsurface processes occur over a wide variety of time scales ranging from seconds (e.g. fracture initiation) to days (e.g. unsteady multiphase flow) and weeks (e.g. induced mineral precipitation). Active source seismic monitoring has the potential to dynamically characterize such alterations and allow estimation of spatially localized rates. However, even optimal timelapse seismic surveys have limited temporal resolution due to both the time required to acquire a survey and the cost of continuous field deployment of instruments and personnel. Traditional timelapse surveys are also limited by experimental repeatability due to a variety of factors including geometry replication and near-surface conditions. Recent research has demonstrated the value of semi-permanently deployed seismic systems with fixed sources and receivers for use in monitoring a variety of processes including near-surface stress changes (Silver et.al. 2007), subsurface movement of supercritical CO2 (Daley et.al. 2007), and preseismic velocity changes in fault regions (Niu et. al. 2008). This strategy, referred to as continuous active source seismic monitoring (CASSM), allows both precise quantification of traveltime changes on the order of 1.1 x 10-7 s and temporal sampling on the order of minutes. However, as previously deployed, CASSM often sacrifices spatial resolution for temporal resolution with previous experiments including only a single source level. We present results from the first deployment of CASSM with a large number of source levels under automated control. Our system is capable of autonomously acquiring full tomographic datasets (10 sources, 72 receivers) in 3 minutes without human intervention, thus allowing active source seismic imaging (rather than monitoring) of processes with short durations. Because no sources or receivers are moved in the acquisition process, signal repeatability is excellent and subtle waveform changes can be interpreted with increased confidence

  14. Martian seismicity

    NASA Technical Reports Server (NTRS)

    Phillips, Roger J.; Grimm, Robert E.

    1991-01-01

    The design and ultimate success of network seismology experiments on Mars depends on the present level of Martian seismicity. Volcanic and tectonic landforms observed from imaging experiments show that Mars must have been a seismically active planet in the past and there is no reason to discount the notion that Mars is seismically active today but at a lower level of activity. Models are explored for present day Mars seismicity. Depending on the sensitivity and geometry of a seismic network and the attenuation and scattering properties of the interior, it appears that a reasonable number of Martian seismic events would be detected over the period of a decade. The thermoelastic cooling mechanism as estimated is surely a lower bound, and a more refined estimate would take into account specifically the regional cooling of Tharsis and lead to a higher frequency of seismic events.

  15. A preliminary census of engineering activities located in Sicily (Southern Italy) which may "potentially" induce seismicity

    NASA Astrophysics Data System (ADS)

    Aloisi, Marco; Briffa, Emanuela; Cannata, Andrea; Cannavò, Flavio; Gambino, Salvatore; Maiolino, Vincenza; Maugeri, Roberto; Palano, Mimmo; Privitera, Eugenio; Scaltrito, Antonio; Spampinato, Salvatore; Ursino, Andrea; Velardita, Rosanna

    2015-04-01

    The seismic events caused by human engineering activities are commonly termed as "triggered" and "induced". This class of earthquakes, though characterized by low-to-moderate magnitude, have significant social and economical implications since they occur close to the engineering activity responsible for triggering/inducing them and can be felt by the inhabitants living nearby, and may even produce damage. One of the first well-documented examples of induced seismicity was observed in 1932 in Algeria, when a shallow magnitude 3.0 earthquake occurred close to the Oued Fodda Dam. By the continuous global improvement of seismic monitoring networks, numerous other examples of human-induced earthquakes have been identified. Induced earthquakes occur at shallow depths and are related to a number of human activities, such as fluid injection under high pressure (e.g. waste-water disposal in deep wells, hydrofracturing activities in enhanced geothermal systems and oil recovery, shale-gas fracking, natural and CO2 gas storage), hydrocarbon exploitation, groundwater extraction, deep underground mining, large water impoundments and underground nuclear tests. In Italy, induced/triggered seismicity is suspected to have contributed to the disaster of the Vajont dam in 1963. Despite this suspected case and the presence in the Italian territory of a large amount of engineering activities "capable" of inducing seismicity, no extensive researches on this topic have been conducted to date. Hence, in order to improve knowledge and correctly assess the potential hazard at a specific location in the future, here we started a preliminary study on the entire range of engineering activities currently located in Sicily (Southern Italy) which may "potentially" induce seismicity. To this end, we performed: • a preliminary census of all engineering activities located in the study area by collecting all the useful information coming from available on-line catalogues; • a detailed compilation

  16. MAGNETOMETRY, SELF-POTENTIAL, AND SEISMIC - ADDITIONAL GEOPHYSICAL METHODS HAVING POTENTIALLY SIGNIFICANT FUTURE UTILIZATION IN AGRICULTURE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Geophysical methods can provide important information in agricultural settings, and the use of these techniques are becoming more and more widespread. Magnetrometry, self-potential, and seismic are three geophysical methods, all of which have the potential for substantial future use in agriculture, ...

  17. Best estimate method versus evaluation method: a comparison of two techniques in evaluating seismic analysis and design. Technical report

    SciTech Connect

    Bumpus, S.E.; Johnson, J.J.; Smith, P.D.

    1980-07-01

    The concept of how two techniques, Best Estimate Method and Evaluation Method, may be applied to the tradditional seismic analysis and design of a nuclear power plant is introduced. Only the four links of the seismic analysis and design methodology chain (SMC)--seismic input, soil-structure interaction, major structural response, and subsystem response--are considered. The objective is to evaluate the compounding of conservatisms in the seismic analysis and design of nuclear power plants, to provide guidance for judgments in the SMC, and to concentrate the evaluation on that part of the seismic analysis and design which is familiar to the engineering community. An example applies the effects of three-dimensional excitations on the model of a nuclear power plant structure. The example demonstrates how conservatisms accrue by coupling two links in the SMC and comparing those results to the effects of one link alone. The utility of employing the Best Estimate Method vs the Evauation Method is also demonstrated.

  18. Application of a cross correlation-based picking algorithm to an active seismic experiment in Sicily and Aeolian Islands

    NASA Astrophysics Data System (ADS)

    Diaz, Alejandro; Álvarez, Isaac; De la Torre, Ángel; García, Luz; Benítez, Ma Carmen; Cortés, Guillermo

    2014-05-01

    The detection of the arrival time of seismic waves or picking is of great importance in many seismology applications. Traditionally, picking has been carried out by human operators. This process is not systematic and relies completely on the expertise and judgment of the analysts. The limitations of manual picking and the increasing amount of data daily stored in the seismic networks worldwide distributed and in active seismic experiments lead to the development of automatic picking algorithms. Current conventional algorithms work with single signals, such as the "short-term average over long-term average" (STA/LTA) algorithm, autoregressive methods or the recently developed "Adaptive Multiband Picking Algorithm" (AMPA). This work proposes a correlation-based picking algorithm, whose main advantage is the fact of using the information of a set of signals, improving the signal to noise ratio and therefore the picking accuracy. The main advantage of this approach is that the algorithm does not require to set up sophisticated parameters, in contrast to other automatic algorithms. The accuracy of the conventional STA/LTA algorithm, the recently developed AMPA algorithm, an autoregressive method, and a preliminary version of the cross correlation-based picking algorithm were assessed using a huge data set composed by active seismic signals from experiments in Tenerife Island (January 2007, Spain). The experiment consisted of the deployment of a dense seismic network on Tenerife Island (125 seismometers in total) and the shooting of air-guns around the island with the Spanish oceanographic vessel Hespérides (6459 air shots in total). Only 110937 signals (13.74% of the total) had the signal to noise ratio enough to be manually picked. Results showed that the use of the cross correlation-based picking algorithm significantly increases the number of signals that can be considered in the tomography. A new active seismic experiment will cover Sicily and Aeolian Islands (TOMO

  19. Test of a new method for seismic indices and granulation parameters extraction

    NASA Astrophysics Data System (ADS)

    Peralta, R. A.; Samadi, R.; Michel, E.

    2015-09-01

    In the framework of the data base project SSI (Stellar Seismic Indices, we have developed and tested a new method aiming at optimizing the simultaneous measurement of both the seismic indices characterizing the oscillations (Δν, νmax) and the indices characterizing the granulation signature. Here, we describe this method which is intended to take advantage of the MLE (maximum likelihood estimate) algorithm combined with the parametrized representation of the red giants pulsation spectrum following the Universal Pattern [6]. We report its performances tested on Monte Carlo simulations.

  20. The 1995 forum on appropriate criteria and methods for seismic design of nuclear piping

    SciTech Connect

    Slagis, G.C.

    1996-12-01

    A record of the 1995 Forum on Appropriate Criteria and Methods for Seismic Design of Nuclear Piping is provided. The focus of the forum was the earthquake experience data base and whether the data base demonstrates that seismic inertia loads will not cause failure in ductile piping systems. This was a follow-up to the 1994 Forum when the use of earthquake experience data, including the recent Northridge earthquake, to justify a design-by-rule method was explored. Two possible topics for the next forum were identified--inspection after an earthquake and design for safe-shutdown earthquake only.

  1. A New Standard Installation Method of the Offline Seismic Observation Station in Heavy Snowfall Area of Tohoku Region

    NASA Astrophysics Data System (ADS)

    Hirahara, S.; Nakayama, T.; Hori, S.; Sato, T.; Chiba, Y.; Okada, T.; Matsuzawa, T.

    2015-12-01

    Soon after the 2011 Tohoku earthquake, seismic activity of Tohoku region, NE Japan is induced in the inland area of Akita prefecture and the border area between Fukushima and Yamagata prefectures. We plan to install a total of 80 offline seismic observation stations in these areas for studying the effect of megathrust earthquake on the activities of inland earthquakes. In our project, maintenance will be held twice-a-year for 4 years from 2015 by using 2.0Hz short-period 3-component seismometer, KVS-300 and ultra-low-power data logger, EDR-X7000 (DC12V 0.08W power supply). We installed seismometer on the rock surface or the slope of the natural ground at the possible sites confirmed with low noise level to obtain distinct seismic waveform data. We report an improvement in installation method of the offline seismic observation station in the heavy snowfall area of Tohoku region based on the retrieved data. In the conventional method, seismometer was installed in the hand-dug hole of a slope in case it is not waterproof. Data logger and battery were installed in the box container on the ground surface, and then, GPS antenna was installed on the pole fixed by stepladder. There are risks of the inclination of seismometer and the damage of equipment in heavy snowfall area. In the new method, seismometer is installed in the robust concrete box on the buried basement consists of precast concrete mass to keep its horizontality. Data logger, battery, and GPS antenna are installed on a high place by using a single pole with anchor bolt and a pole mount cabinet to enhance their safety. As a result, total costs of installation are kept down because most of the equipment is reusable. Furthermore, an environmental burden of waste products is reduced.

  2. Stable and unstable phases of elevated seismic activity at the persistently restless Telica Volcano, Nicaragua

    NASA Astrophysics Data System (ADS)

    Rodgers, Mel; Roman, Diana C.; Geirsson, Halldor; LaFemina, Peter; McNutt, Stephen R.; Muñoz, Angelica; Tenorio, Virginia

    2015-01-01

    Telica Volcano, Nicaragua, is a persistently restless volcano with daily seismicity rates that can vary by orders of magnitude without apparent connection to eruptive activity. Low-frequency (LF) events are dominant and peaks in seismicity rate show little correlation with eruptive episodes, presenting a challenge for seismic monitoring and eruption forecasting. A short period seismic station (TELN) has been operated on Telica's summit since 1993, and in 2010 the installation of a six-station broadband seismic and eleven-station continuous GPS network (the TESAND network) was completed to document in detail the seismic characteristics of a persistently restless volcano. Between our study period of November 2009 and May 2013, over 400,000 events were detected at the TESAND summit station (TBTN), with daily event rates ranging from 5 to 1400. We present spectral analyses and classifications of ~ 200,000 events recorded by the TESAND network between April 2010 and March 2013, and earthquake locations for a sub-set of events between July 2010 and February 2012. In 2011 Telica erupted in a series of phreatic vulcanian explosions. Six months before the 2011 eruption, we observe a sudden decrease in LF events concurrent with a swarm of high-frequency (HF) events, followed by a decline in overall event rates, which reached a minimum at the eruption onset. We observe repeated periods of high and low seismicity rates and suggest these changes in seismicity represent repeated transitions between open-system and closed-system degassing. We suggest that these short- and long-term transitions between open to closed-system degassing form part of a long-term pattern of stable vs. unstable phases at Telica. Stable phases are characterised by steady high-rate seismicity and represent stable open-system degassing, whereas unstable phases are characterised by highly variable seismicity rates and represent repeated transitions from open to closed-system degassing, where the system is

  3. Seismic imaging of the geodynamic activity at the western Eger rift in central Europe

    NASA Astrophysics Data System (ADS)

    Mullick, N.; Buske, S.; Hrubcova, P.; Ruzek, B.; Shapiro, S.; Wigger, P.; Fischer, T.

    2015-04-01

    The western Eger rift at the Czech-German border in central Europe is an important geodynamically active area within the European Cenzoic rift system (ECRS) in the forelands of the Alps. Along with two other active areas of the ECRS, the French Massif Central and the east and west Eifel volcanic fields, it is characterized by numerous CO2-rich fluid emission points and frequent micro-seismicity. Existence of a plume(s) is indicated in the upper mantle which may be responsible for these observations. Here we reprocess a pre-existing deep seismic reflection profile '9HR' and interpret the subsurface structures as mapped by seismic reflectivity with previous findings, mainly from seismological and geochemical studies, to investigate the geodynamic activity in the subsurface. We find prominent hints of pathways which may allow magmatic fluids originating in the upper mantle to rise through the crust and cause the observed fluid emanations and earthquake activity.

  4. Active and long-lived permanent forearc deformation driven by the subduction seismic cycle

    NASA Astrophysics Data System (ADS)

    Aron Melo, Felipe Alejandro

    I have used geological, geophysical and engineering methods to explore mechanisms of upper plate, brittle deformation at active forearc regions. My dissertation particularly addresses the permanent deformation style experienced by the forearc following great subduction ruptures, such as the 2010 M w8.8 Maule, Chile and 2011 Mw9.0 Tohoku, Japan earthquakes. These events triggered large, shallow seismicity on upper plate normal faults above the rupture reaching Mw7.0. First I present new structural data from the Chilean Coastal Cordillera over the rupture zone of the Maule earthquake. The study area contains the Pichilemu normal fault, which produced the large crustal aftershocks of the megathrust event. Normal faults are the major neotectonic structural elements but reverse faults also exist. Crustal seismicity and GPS surface displacements show that the forearc experiences pulses of rapid coseismic extension, parallel to the heave of the megathrust, and slow interseismic, convergence-parallel shortening. These cycles, over geologic time, build the forearc structural grain, reactivating structures properly-oriented respect to the deformation field of each stage of the interplate cycle. Great subduction events may play a fundamental role in constructing the crustal architecture of extensional forearc regions. Static mechanical models of coseismic and interseismic upper plate deformation are used to explore for distinct features that could result from brittle fracturing over the two stages of the interplate cycle. I show that the semi-elliptical outline of the first-order normal faults along the Coastal Cordillera may define the location of a characteristic, long-lived megathrust segment. Finally, using data from the Global CMT catalog I analyzed the seismic behavior through time of forearc regions that have experienced great subduction ruptures >Mw7.7 worldwide. Between 61% and 83% of the cases where upper plate earthquakes exhibited periods of increased seismicity

  5. Development of a low cost method to estimate the seismic signature of a geothermal field from ambient seismic noise analysis, Authors: Tibuleac, I. M., J. Iovenitti, S. Pullammanapallil, D. von Seggern, F.H. Ibser, D. Shaw and H. McLahlan

    NASA Astrophysics Data System (ADS)

    Tibuleac, I. M.; Iovenitti, J. L.; Pullammanappallil, S. K.; von Seggern, D. H.; Ibser, H.; Shaw, D.; McLachlan, H.

    2015-12-01

    A new, cost effective and non-invasive exploration method using ambient seismic noise has been tested at Soda Lake, NV, with promising results. Seismic interferometry was used to extract Green's Functions (P and surface waves) from 21 days of continuous ambient seismic noise. With the advantage of S-velocity models estimated from surface waves, an ambient noise seismic reflection survey along a line (named Line 2), although with lower resolution, reproduced the results of the active survey, when the ambient seismic noise was not contaminated by strong cultural noise. Ambient noise resolution was less at depth (below 1000m) compared to the active survey. Useful information could be recovered from ambient seismic noise, including dipping features and fault locations. Processing method tests were developed, with potential to improve the virtual reflection survey results. Through innovative signal processing techniques, periods not typically analyzed with high frequency sensors were used in this study to obtain seismic velocity model information to a depth of 1.4km. New seismic parameters such as Green's Function reflection component lateral variations, waveform entropy, stochastic parameters (Correlation Length and Hurst number) and spectral frequency content extracted from active and passive surveys showed potential to indicate geothermal favorability through their correlation with high temperature anomalies, and showed potential as fault indicators, thus reducing the uncertainty in fault identification. Geothermal favorability maps along ambient seismic Line 2 were generated considering temperature, lithology and the seismic parameters investigated in this study and compared to the active Line 2 results. Pseudo-favorability maps were also generated using only the seismic parameters analyzed in this study.

  6. Battery equalization active methods

    NASA Astrophysics Data System (ADS)

    Gallardo-Lozano, Javier; Romero-Cadaval, Enrique; Milanes-Montero, M. Isabel; Guerrero-Martinez, Miguel A.

    2014-01-01

    Many different battery technologies are available for the applications which need energy storage. New researches are being focused on Lithium-based batteries, since they are becoming the most viable option for portable energy storage applications. As most of the applications need series battery strings to meet voltage requirements, battery imbalance is an important matter to be taken into account, since it leads the individual battery voltages to drift apart over time, and premature cells degradation, safety hazards, and capacity reduction will occur. A large number of battery equalization methods can be found, which present different advantages/disadvantages and are suitable for different applications. The present paper presents a summary, comparison and evaluation of the different active battery equalization methods, providing a table that compares them, which is helpful to select the suitable equalization method depending on the application. By applying the same weight to the different parameters of comparison, switch capacitor and double-tiered switching capacitor have the highest ratio. Cell bypass methods are cheap and cell to cell ones are efficient. Cell to pack, pack to cell and cell to pack to cell methods present a higher cost, size, and control complexity, but relatively low voltage and current stress in high-power applications.

  7. Seismic Activity: Public Alert and Warning: Legal Implications

    NASA Astrophysics Data System (ADS)

    Zocchetti, D.

    2007-12-01

    As science and technology evolve in ways that increase our ability to inform the public of potentially destructive seismic activity, there are significant legal issues for consideration. Even though countries and even states within the United States have differing legal tenets that could either change or at least re-shape the outcome of specific legal questions that this session will be pondering, there are fundamental legal principals that will permeate. It is often said that the law lags behind society and in particular its technological developments. No doubt in the area of warning the public of impending destructive forces of nature or society, the law will need to do some catching up. The law is probably adequately developed for at least some preliminary discussion of the key issues. No matter the legal scheme, if there is a failure or perceived failure in the system to warn people of a pending emergencies, albeit an earthquake, tsunami, or other predictable event, those who are harmed or believe they are harmed will seek relief under the law. Every day there are situations wherein the failure to warn or to adequately warn is key, such as with faulty or defective consumer products, escaped prisoners, and police high-speed vehicle chases. With alert and warning systems for disaster, however, we have a unique set of facts. Generally, the systems and their failures occur during emergencies or at least during situations under apparently exigent circumstances when the disaster's predictability is widely recognized as less than 100 percent. The law, in particular United States tort law, has been particularly lenient when people and organizations are operating during compressed timeframes and their actions are generally considered necessary to address circumstances relative to public safety. The legal system has been forgiving when the actor that failed or appeared to fail was government. The courts have liberally applied the principal of sovereign immunity to

  8. Predicting earthquakes by analyzing accelerating precursory seismic activity

    USGS Publications Warehouse

    Varnes, D.J.

    1989-01-01

    During 11 sequences of earthquakes that in retrospect can be classed as foreshocks, the accelerating rate at which seismic moment is released follows, at least in part, a simple equation. This equation (1) is {Mathematical expression},where {Mathematical expression} is the cumulative sum until time, t, of the square roots of seismic moments of individual foreshocks computed from reported magnitudes;C and n are constants; and tfis a limiting time at which the rate of seismic moment accumulation becomes infinite. The possible time of a major foreshock or main shock, tf,is found by the best fit of equation (1), or its integral, to step-like plots of {Mathematical expression} versus time using successive estimates of tfin linearized regressions until the maximum coefficient of determination, r2,is obtained. Analyzed examples include sequences preceding earthquakes at Cremasta, Greece, 2/5/66; Haicheng, China 2/4/75; Oaxaca, Mexico, 11/29/78; Petatlan, Mexico, 3/14/79; and Central Chile, 3/3/85. In 29 estimates of main-shock time, made as the sequences developed, the errors in 20 were less than one-half and in 9 less than one tenth the time remaining between the time of the last data used and the main shock. Some precursory sequences, or parts of them, yield no solution. Two sequences appear to include in their first parts the aftershocks of a previous event; plots using the integral of equation (1) show that the sequences are easily separable into aftershock and foreshock segments. Synthetic seismic sequences of shocks at equal time intervals were constructed to follow equation (1), using four values of n. In each series the resulting distributions of magnitudes closely follow the linear Gutenberg-Richter relation log N=a-bM, and the product n times b for each series is the same constant. In various forms and for decades, equation (1) has been used successfully to predict failure times of stressed metals and ceramics, landslides in soil and rock slopes, and volcanic

  9. Subsurface structure of the geothermal well site in Ilan, Taiwan by using the seismic exploration method

    NASA Astrophysics Data System (ADS)

    Yen, Ting-Ching; Shih, Ruey-Chuyan; Wang, Chien-Ying

    2015-04-01

    Geothermal energy could be a feasible way to reconcile the energy needs of a growing population and economic development. Several studies have shown that the Ilan area is a significantly potential area for developing the geothermal energy in Taiwan. However, since the Ilan Plain is covered by the thick Quaternary sediments, the previous studies of the subsurface structure in this area are mostly at a large-scale. The purpose of this study is to find an appropriate drilling site for the geothermal well in Ilan by using the seismic exploration method. We cooperated with the seismic survey team from National Central University again, used the two vibrators (EnviroVibe) along with a 432-channel seismograph to conduct more seismic surveys in the Ilan area. Since we have collected more 2-D seismic sections in the different directions to sketch the structures underneath, we are now able to describe the geometry of the subsurface structures in three dimensions. The seismic profiles showed that the sediments are thickened to the east, and the bedding planes are dominantly dipping to the northeast and slightly tilted. As we have known the Ilan area is located in a tectonic divergent area, the major fault system passing through this area may result in a derivative structure, and provide the channels for inflow of the hot water to produce geothermal power. Currently, we have construct a 3D model of the subsurface structure, and is waiting for the evidence from core boring to examine the accuracy of the interpretation.

  10. Seismicity study of volcano-tectonic in and around Tangkuban Parahu active volcano in West Java region, Indonesia

    NASA Astrophysics Data System (ADS)

    Ry, Rexha V.; Priyono, A.; Nugraha, A. D.; Basuki, A.

    2016-05-01

    Tangkuban Parahu is one of the active volcano in Indonesia located about 15 km northern part of Bandung city. The objective of this study is to investigate the seismic activity in the time periods of January 2013 to December 2013. First, we identified seismic events induced by volcano-tectonic activities. These micro-earthquake events were identified as having difference of P-wave and S-wave arrival times less than three seconds. Then, we constrained its location of hypocenter to locate the source of the activities. Hypocenter determination was performed using adaptive simulated annealing method. Using these results, seismic tomographic inversions were conducted to image the three-dimensional velocity structure of Vp, Vs, and the Vp/Vs ratio. In this study, 278 micro-earthquake events have been identified and located. Distribution of hypocenters around Tangkuban Parahu volcano forms an alignment structure and may be related to the stress induced by magma below, also movement of shallow magma below Domas Crater. Our preliminary tomographic inversion results indicate the presences of low Vp, high Vs, and low Vp/Vs ratio that associate to accumulated young volcanic eruption products and hot material zones.

  11. Application of the SASSI soil structure interaction method to CANDU 6 NPP seismic analysis

    SciTech Connect

    Ricciuti, R.A.; Elgohary, M.; Usmani, S.A.

    1996-12-01

    The standard CANDU 6 NPP has been conservatively qualified for a Design Basis Earthquake (DBE) peak horizontal ground acceleration of 0.2 g. Currently there are potential opportunities for siting the CANDU 6 at higher seismicity sites. In order to be able to extend the use of a standardized design for sites with higher seismicity than the standard plant, various design options, including the use of the SASSI Soil Structure Interaction (SSI) analysis method, are being evaluated. This paper presents the results of a study to assess the potential benefits from utilization of the SASSI computer program and the use of more realistic damping ratios for the structures.

  12. EVALUATIONS BY QUESTIONNAIRES ABOUT SIMPLE METHODS OF SEISMIC STRENGTHENING AND SETBACK OF HOUSES

    NASA Astrophysics Data System (ADS)

    Mizuno, Norio; Miyajima, Masakatsu

    Law on promotion of renovation for earthquake-resistant structures was revised in 2006. Since then administrative agencies have been promoting seismic diagnosis and retrofit of houses. But citizens living in densely built-up areas cannot rebuild their houses because of their economic reasons and Building Standards Act regulations. Therefore, we conducted questionnaire surveys of construction companies located in Ishikawa Prefecture and citizens living in Kanazawa City. The results of surveys show that many construction companies are not in favor of simple method of seismic retrofit, and that width of roads hardly influence the citizens' consciousness to renovation for earthquake-resistant structures.

  13. Markov Chain Monte Carlo Sampling Methods for 1D Seismic and EM Data Inversion

    2008-09-22

    This software provides several Markov chain Monte Carlo sampling methods for the Bayesian model developed for inverting 1D marine seismic and controlled source electromagnetic (CSEM) data. The current software can be used for individual inversion of seismic AVO and CSEM data and for joint inversion of both seismic and EM data sets. The structure of the software is very general and flexible, and it allows users to incorporate their own forward simulation codes and rockmore » physics model codes easily into this software. Although the softwae was developed using C and C++ computer languages, the user-supplied codes can be written in C, C++, or various versions of Fortran languages. The software provides clear interfaces for users to plug in their own codes. The output of this software is in the format that the R free software CODA can directly read to build MCMC objects.« less

  14. Methods and apparatus for use in detecting seismic waves in a borehole

    DOEpatents

    West, Phillip B.; Fincke, James R.; Reed, Teddy R.

    2006-05-23

    The invention provides methods and apparatus for detecting seismic waves propagating through a subterranean formation surrounding a borehole. In a first embodiment, a sensor module uses the rotation of bogey wheels to extend and retract a sensor package for selective contact and magnetic coupling to casing lining the borehole. In a second embodiment, a sensor module is magnetically coupled to the casing wall during its travel and dragged therealong while maintaining contact therewith. In a third embodiment, a sensor module is interfaced with the borehole environment to detect seismic waves using coupling through liquid in the borehole. Two or more of the above embodiments may be combined within a single sensor array to provide a resulting seismic survey combining the optimum of the outputs of each embodiment into a single data set.

  15. Recent Seismic and Geodetic Activity at Multiple Volcanoes in the Ecuadorean Andes

    NASA Astrophysics Data System (ADS)

    Hernandez, S.; Ruiz, M. C.; McCausland, W. A.; Prejean, S. G.; Mothes, P. A.; Bell, A. F.; Hidalgo, S.; Barrington, C.; Yepez, M.; Aguaiza, S.; Plain, M.

    2015-12-01

    The state of volcanic activity often fluctuates between periods of repose and unrest. The transition time between a period of repose and unrest, or vice versa for an open system, can occur within a matter of hours or days. Because of this short time scale, real-time seismic and geodetic (e.g. tiltmeter, GPS) monitoring networks are crucial for characterizing the state of activity of a volcano. In the Ecuadorean Andes, 5 volcanoes demonstrate long-term (Tungurahua, Reventador, and Guagua Pichincha) or recently reactivated (Cotopaxi, Chiles-Cerro Negro) seismic and geodetic activity. The Instituto Geofisico regularly characterizes volcano seismicity into long period, very long period, volcano-tectonic, and tremor events. Significant recent changes at these volcanoes include: rigorous reactivation of glacier-capped Cotopaxi, drumbeat seismicity absent a dome extrusion at Tungurahua, and regularly reoccurring (~7 day recurrence interval), shallow seismic swarms at Guagua Pichincha. These volcanoes locate along both the Western and Eastern Cordillera of the Ecuadorean Andes and, where data are available, manifest important variations in chemical composition, daily gas flux, and surficial deformation. We summarize the long-term geophysical parameters measured at each volcano and place recent changes in each parameter in a larger magmatic and hydrothermal context. All of the studied volcanoes present significant societal hazards to local and regional communities.

  16. Comparison of seismic sources for shallow seismic: sledgehammer and pyrotechnics

    NASA Astrophysics Data System (ADS)

    Brom, Aleksander; Stan-Kłeczek, Iwona

    2015-10-01

    The pyrotechnic materials are one of the types of the explosives materials which produce thermal, luminous or sound effects, gas, smoke and their combination as a result of a self-sustaining chemical reaction. Therefore, pyrotechnics can be used as a seismic source that is designed to release accumulated energy in a form of seismic wave recorded by tremor sensors (geophones) after its passage through the rock mass. The aim of this paper was to determine the utility of pyrotechnics for shallow seismic engineering. The work presented comparing the conventional method of seismic wave excitation for seismic refraction method like plate and hammer and activating of firecrackers on the surface. The energy released by various sources and frequency spectra was compared for the two types of sources. The obtained results did not determine which sources gave the better results but showed very interesting aspects of using pyrotechnics in seismic measurements for example the use of pyrotechnic materials in MASW.

  17. Variations of terrestrial geomagnetic activity correlated to M6+ global seismic activity

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2013-04-01

    From the surface of the Sun, as a result of a solar flare, are expelled a coronal mass (CME or Coronal Mass Ejection) that can be observed from the Earth through a coronagraph in white light. This ejected material can be compared to an electrically charged cloud (plasma) mainly composed of electrons, protons and other small quantities of heavier elements such as helium, oxygen and iron that run radially from the Sun along the lines of the solar magnetic field and pushing into interplanetary space. Sometimes the CME able to reach the Earth causing major disruptions of its magnetosphere: mashed in the region illuminated by the Sun and expanding in the region not illuminated. This interaction creates extensive disruption of the Earth's geomagnetic field that can be detected by a radio receiver tuned to the ELF band (Extreme Low Frequency 0-30 Hz). The Radio Emissions Project (scientific research project founded in February 2009 by Gabriele Cataldi and Daniele Cataldi), analyzing the change in the Earth's geomagnetic field through an induction magnetometer tuned between 0.001 and 5 Hz (bandwidth in which possible to observe the geomagnetic pulsations) was able to detect the existence of a close relationship between this geomagnetic perturbations and the global seismic activity M6+. During the arrival of the CME on Earth, in the Earth's geomagnetic field are generated sudden and intensive emissions that have a bandwidth including between 0 and 15 Hz, an average duration of 2-8 hours, that preceding of 0-12 hours M6+ earthquakes. Between 1 January 2012 and 31 December 2012, all M6+ earthquakes recorded on a global scale were preceded by this type of signals which, due to their characteristics, have been called "Seismic Geomagnetic Precursors" (S.G.P.). The main feature of Seismic Geomagnetic Precursors is represented by the close relationship that they have with the solar activity. In fact, because the S.G.P. are geomagnetic emissions, their temporal modulation depends

  18. Anthropogenically-Induced Superficial Seismic Activity Modulated By Slow-Slip Events in Guerrero, Mexico

    NASA Astrophysics Data System (ADS)

    Frank, W.; Shapiro, N.; Husker, A. L.; Kostoglodov, V.; Campillo, M.

    2014-12-01

    We use the data of the MASE seismic experiment operated during 2.5 years in Guerrero, Mexico to create a large catalog of seismic multiplets. This catalog is dominated by families of Low-Frequency Earthquakes (LFE) occurring in vicinity of the main subduction interface. In addition to more than one thousand LFE families, we detected nine repeating seismic event families that are located in the upper crust and are anthropogenically induced (AI) by mining blasts. Analysis of the recurrence of these AI events in time shows that their activity significantly increases during the strong Slow-Slip Event (SSE) in 2006. Modeled static stress perturbations induced by the SSE at the surface are ~5 kPa that is on the same order of magnitude as dynamic stress perturbations observed to trigger other low stress drop phenomena, such as tectonic tremor. We propose therefore that strong SSEs in Guerrero impose an extensional regime throughout the continental crust, modifying the stress field near the surface and increasing AI activity. This modulation of the recurrence of the crustal seismic events by the SSE-induced stress might be related to another recent observation: the SSE-induced reduction of seismic velocities linked to nonlinear elastic effects caused by opening of cracks (Rivet et al., 2011, 2014).

  19. High resolution imaging of vadose zone transport using crosswell radar and seismic methods

    SciTech Connect

    Majer, Ernest L.; Williams, Kenneth H.; Peterson, John E.; Daley, Thomas E.

    2001-10-10

    The summary and conclusions are that overall the radar and seismic results were excellent. At the time of design of the experiments we did not know how well these two methods could penetrate or resolve the moisture content and structure. It appears that the radar could easily go up to 5, even 10 meters between boreholes at 200 Mhz and even father (up to 20 to 40 m) at 50 Mhz. The seismic results indicate that at several hundred hertz propagation of 20 to 30 meters giving high resolution is possible. One of the most important results, however is that together the seismic and radar are complementary in their properties estimation. The radar being primarily sensitive to changes in moisture content, and the seismic being primarily sensitive to porosity. Taken in a time lapse sense the radar can show the moisture content changes to a high resolution, with the seismic showing high resolution lithology. The significant results for each method are: Radar: (1) Delineated geological layers 0.25 to 3.5 meters thick with 0.25 m resolution; (2) Delineated moisture movement and content with 0.25 m resolution; (3) Compared favorably with neutron probe measurements; and (4) Penetration up to 30 m. Radar results indicate that the transport of the riverwater is different from that of the heavier and more viscous sodium thiosulfate. It appears that the heavier fluids are not mixing readily with the in-situ fluids and the transport may be influenced by them. Seismic: (1) Delineated lithology at .25 m resolution; (2) Penetration over 20 meters, with a possibility of up to 30 or more meters; and (3) Maps porosity and density differences of the sediments. Overall the seismic is mapping the porosity and density distribution. The results are consistent with the flow field mapped by the radar, there is a change in flow properties at the 10 to 11 meter depth in the flow cell. There also appears to be break through by looking at the radar data with the denser sodium thiosulfate finally

  20. Seismic Surveys Negatively Affect Humpback Whale Singing Activity off Northern Angola

    PubMed Central

    Cerchio, Salvatore; Strindberg, Samantha; Collins, Tim; Bennett, Chanda; Rosenbaum, Howard

    2014-01-01

    Passive acoustic monitoring was used to document the presence of singing humpback whales off the coast of Northern Angola, and opportunistically test for the effect of seismic survey activity in the vicinity on the number of singing whales. Two Marine Autonomous Recording Units (MARUs) were deployed between March and December 2008 in the offshore environment. Song was first heard in mid June and continued through the remaining duration of the study. Seismic survey activity was heard regularly during two separate periods, consistently throughout July and intermittently in mid-October/November. Numbers of singers were counted during the first ten minutes of every hour for the period from 24 May to 1 December, and Generalized Additive Mixed Models (GAMMs) were used to assess the effect of survey day (seasonality), hour (diel variation), moon phase and received levels of seismic survey pulses (measured from a single pulse during each ten-minute sampled period) on singer number. Application of GAMMs indicated significant seasonal variation, which was the most pronounced effect when assessing the full dataset across the entire season (p<0.001); however seasonality almost entirely dropped out of top-ranked models when applied to a reduced dataset during the July period of seismic survey activity. Diel variation was significant in both the full and reduced datasets (from p<0.01 to p<0.05) and often included in the top-ranked models. The number of singers significantly decreased with increasing received level of seismic survey pulses (from p<0.01 to p<0.05); this explanatory variable was included among the top ranked models for one MARU in the full dataset and both MARUs in the reduced dataset. This suggests that the breeding display of humpback whales is disrupted by seismic survey activity, and thus merits further attention and study, and potentially conservation action in the case of sensitive breeding populations. PMID:24618836

  1. Seismic surveys negatively affect humpback whale singing activity off northern Angola.

    PubMed

    Cerchio, Salvatore; Strindberg, Samantha; Collins, Tim; Bennett, Chanda; Rosenbaum, Howard

    2014-01-01

    Passive acoustic monitoring was used to document the presence of singing humpback whales off the coast of Northern Angola, and opportunistically test for the effect of seismic survey activity in the vicinity on the number of singing whales. Two Marine Autonomous Recording Units (MARUs) were deployed between March and December 2008 in the offshore environment. Song was first heard in mid June and continued through the remaining duration of the study. Seismic survey activity was heard regularly during two separate periods, consistently throughout July and intermittently in mid-October/November. Numbers of singers were counted during the first ten minutes of every hour for the period from 24 May to 1 December, and Generalized Additive Mixed Models (GAMMs) were used to assess the effect of survey day (seasonality), hour (diel variation), moon phase and received levels of seismic survey pulses (measured from a single pulse during each ten-minute sampled period) on singer number. Application of GAMMs indicated significant seasonal variation, which was the most pronounced effect when assessing the full dataset across the entire season (p<0.001); however seasonality almost entirely dropped out of top-ranked models when applied to a reduced dataset during the July period of seismic survey activity. Diel variation was significant in both the full and reduced datasets (from p<0.01 to p<0.05) and often included in the top-ranked models. The number of singers significantly decreased with increasing received level of seismic survey pulses (from p<0.01 to p<0.05); this explanatory variable was included among the top ranked models for one MARU in the full dataset and both MARUs in the reduced dataset. This suggests that the breeding display of humpback whales is disrupted by seismic survey activity, and thus merits further attention and study, and potentially conservation action in the case of sensitive breeding populations. PMID:24618836

  2. Tomographic image of a seismically active volcano: Mammoth Mountain, California

    USGS Publications Warehouse

    Dawson, Phillip B.; Chouet, Bernard A.; Pitt, Andrew M.

    2016-01-01

    High-resolution tomographic P wave, S wave, and VP/VS velocity structure models are derived for Mammoth Mountain, California, using phase data from the Northern California Seismic Network and a temporary deployment of broadband seismometers. An anomalous volume (5.1 × 109 to 5.9 × 1010m3) of low P and low S wave velocities is imaged beneath Mammoth Mountain, extending from near the surface to a depth of ∼2 km below sea level. We infer that the reduction in seismic wave velocities is due to the presence of CO2 distributed in oblate spheroid pores with mean aspect ratio α = 1.6 × 10−3 to 7.9 × 10−3 (crack-like pores) and mean gas volume fraction ϕ = 8.1 × 10−4 to 3.4 × 10−3. The pore density parameter κ = 3ϕ/(4πα) = na3=0.11, where n is the number of pores per cubic meter and a is the mean pore equatorial radius. The total mass of CO2 is estimated to be 4.6 × 109 to 1.9 × 1011 kg. The local geological structure indicates that the CO2 contained in the pores is delivered to the surface through fractures controlled by faults and remnant foliation of the bedrock beneath Mammoth Mountain. The total volume of CO2 contained in the reservoir suggests that given an emission rate of 500 tons day−1, the reservoir could supply the emission of CO2 for ∼25–1040 years before depletion. Continued supply of CO2 from an underlying magmatic system would significantly prolong the existence of the reservoir.

  3. Tomographic image of a seismically active volcano: Mammoth Mountain, California

    NASA Astrophysics Data System (ADS)

    Dawson, Phillip; Chouet, Bernard; Pitt, Andrew

    2016-01-01

    High-resolution tomographic P wave, S wave, and VP/VS velocity structure models are derived for Mammoth Mountain, California, using phase data from the Northern California Seismic Network and a temporary deployment of broadband seismometers. An anomalous volume (5.1 × 109 to 5.9 × 1010m3) of low P and low S wave velocities is imaged beneath Mammoth Mountain, extending from near the surface to a depth of ˜2 km below sea level. We infer that the reduction in seismic wave velocities is due to the presence of CO2 distributed in oblate spheroid pores with mean aspect ratio α = 1.6 × 10-3 to 7.9 × 10-3 (crack-like pores) and mean gas volume fraction ϕ = 8.1 × 10-4 to 3.4 × 10-3. The pore density parameter κ = 3ϕ/(4πα) = na3=0.11, where n is the number of pores per cubic meter and a is the mean pore equatorial radius. The total mass of CO2 is estimated to be 4.6 × 109 to 1.9 × 1011 kg. The local geological structure indicates that the CO2 contained in the pores is delivered to the surface through fractures controlled by faults and remnant foliation of the bedrock beneath Mammoth Mountain. The total volume of CO2 contained in the reservoir suggests that given an emission rate of 500 tons day-1, the reservoir could supply the emission of CO2 for ˜25-1040 years before depletion. Continued supply of CO2 from an underlying magmatic system would significantly prolong the existence of the reservoir.

  4. Tomographic Image of a Seismically Active Volcano: Mammoth Mountain, California

    NASA Astrophysics Data System (ADS)

    Dawson, P. B.; Chouet, B. A.; Pitt, A. M.

    2015-12-01

    High-resolution tomographic P wave, S wave, and VP /VS velocity structure models are derived for Mammoth Mountain, California using phase data from the Northern California Seismic Network and a temporary deployment of broadband seismometers. An anomalous volume (˜50 km3) of low P and low S wave velocities is imaged beneath Mammoth Mountain, extending from near the surface to a depth of ˜2 km below sea level. We infer that the reduction in seismic wave velocities is primarily due to the presence of CO2 distributed in oblate-spheroid pores with mean aspect ratio α ˜8 x 10-4 (crack-like pores) and gas volume fraction φ ˜4 x 10-4. The pore density parameter κ = 3φ / (4πα) = na3 = 0.12, where n is the number of pores per cubic meter and a is the mean pore equatorial radius. The total mass of CO2 is estimated to range up to ˜1.6 x 1010 kg if the pores exclusively contain CO2, although he presence of an aqueous phase may lower this estimate by up to one order of magnitude. The local geological structure indicates that the CO2 contained in the pores is delivered to the surface through fractures controlled by faults and remnant foliation of the bedrock beneath Mammoth Mountain. The total volume of CO2 contained in the reservoir suggests that given an emission rate of 5 x 105 kg day-1, the reservoir could supply the emission of CO2 for ˜8 to ˜90 years before depletion. Continued supply of CO2 from an underlying magmatic system would significantly prolong the existence of the reservoir.

  5. Validating 3D Seismic Velocity Models Using the Spectral Element Method

    NASA Astrophysics Data System (ADS)

    Maceira, M.; Rowe, C. A.; Allen, R. M.; Obrebski, M. J.

    2010-12-01

    As seismic instrumentation, data storage and dissemination and computational power improve, seismic velocity models attempt to resolve smaller structures and cover larger areas. However, it is unclear how accurate these velocity models are and, while the best models available are used for event determination, it is difficult to put uncertainties on seismic event parameters. Model validation is typically done using resolution tests that assume the imaging theory used is accurate and thus only considers the impact of the data coverage on resolution. We present the results of a more rigorous approach to model validation via full three-dimensional waveform propagation using Spectral Element Methods (SEM). This approach makes no assumptions about the theory used to generate the models but require substantial computational resources. We first validate 3D tomographic models for the Western USA generated using both ray-theoretical and finite-frequency methods. The Dynamic North America (DNA) Models of P- and S- velocity structure (DNA09-P and DNA09-S) use teleseismic body-wave traveltime residuals recorded at over 800 seismic stations provided by the Earthscope USArray and regional seismic networks. We performed systematic computations of synthetics for the dataset used to generate the DNA models. Direct comparison of these synthetic seismograms to the actual observations allows us to accurately assess and validate the models. Implementation of the method for a densely instrumented region such as that covered by the DNA model provides a useful testbed for the validation methods that we will subsequently apply to other, more challenging study areas.

  6. Simultaneous denoising and reconstruction of 5D seismic data via damped rank-reduction method

    NASA Astrophysics Data System (ADS)

    Chen, Yangkang; Zhang, Dong; Jin, Zhaoyu; Chen, Xiaohong; Zu, Shaohuan; Huang, Weilin; Gan, Shuwei

    2016-06-01

    The Cadzow rank-reduction method can be effectively utilized in simultaneously denoising and reconstructing 5D seismic data that depends on four spatial dimensions. The classic version of Cadzow rank-reduction method arranges the 4D spatial data into a level-four block Hankel/Toeplitz matrix and then applies truncated singular value decomposition (TSVD) for rank-reduction. When the observed data is extremely noisy, which is often the feature of real seismic data, traditional TSVD cannot be adequate for attenuating the noise and reconstructing the signals. The reconstructed data tends to contain a significant amount of residual noise using the traditional TSVD method, which can be explained by the fact that the reconstructed data space is a mixture of both signal subspace and noise subspace. In order to better decompose the block Hankel matrix into signal and noise components, we introduced a damping operator into the traditional TSVD formula, which we call the damped rank-reduction method. The damped rank-reduction method can obtain a perfect reconstruction performance even when the observed data has extremely low signal-to-noise ratio (SNR). The feasibility of the improved 5D seismic data reconstruction method was validated via both 5D synthetic and field data examples. We presented comprehensive analysis of the data examples and obtained valuable experience and guidelines in better utilizing the proposed method in practice. Since the proposed method is convenient to implement and can achieve immediate improvement, we suggest its wide application in the industry.

  7. Simultaneous denoising and reconstruction of 5-D seismic data via damped rank-reduction method

    NASA Astrophysics Data System (ADS)

    Chen, Yangkang; Zhang, Dong; Jin, Zhaoyu; Chen, Xiaohong; Zu, Shaohuan; Huang, Weilin; Gan, Shuwei

    2016-09-01

    The Cadzow rank-reduction method can be effectively utilized in simultaneously denoising and reconstructing 5-D seismic data that depend on four spatial dimensions. The classic version of Cadzow rank-reduction method arranges the 4-D spatial data into a level-four block Hankel/Toeplitz matrix and then applies truncated singular value decomposition (TSVD) for rank reduction. When the observed data are extremely noisy, which is often the feature of real seismic data, traditional TSVD cannot be adequate for attenuating the noise and reconstructing the signals. The reconstructed data tend to contain a significant amount of residual noise using the traditional TSVD method, which can be explained by the fact that the reconstructed data space is a mixture of both signal subspace and noise subspace. In order to better decompose the block Hankel matrix into signal and noise components, we introduced a damping operator into the traditional TSVD formula, which we call the damped rank-reduction method. The damped rank-reduction method can obtain a perfect reconstruction performance even when the observed data have extremely low signal-to-noise ratio. The feasibility of the improved 5-D seismic data reconstruction method was validated via both 5-D synthetic and field data examples. We presented comprehensive analysis of the data examples and obtained valuable experience and guidelines in better utilizing the proposed method in practice. Since the proposed method is convenient to implement and can achieve immediate improvement, we suggest its wide application in the industry.

  8. Military applications and examples of near-surface seismic surface wave methods (Invited)

    NASA Astrophysics Data System (ADS)

    sloan, S.; Stevens, R.

    2013-12-01

    Although not always widely known or publicized, the military uses a variety of geophysical methods for a wide range of applications--some that are already common practice in the industry while others are truly novel. Some of those applications include unexploded ordnance detection, general site characterization, anomaly detection, countering improvised explosive devices (IEDs), and security monitoring, to name a few. Techniques used may include, but are not limited to, ground penetrating radar, seismic, electrical, gravity, and electromagnetic methods. Seismic methods employed include surface wave analysis, refraction tomography, and high-resolution reflection methods. Although the military employs geophysical methods, that does not necessarily mean that those methods enable or support combat operations--often times they are being used for humanitarian applications within the military's area of operations to support local populations. The work presented here will focus on the applied use of seismic surface wave methods, including multichannel analysis of surface waves (MASW) and backscattered surface waves, often in conjunction with other methods such as refraction tomography or body-wave diffraction analysis. Multiple field examples will be shown, including explosives testing, tunnel detection, pre-construction site characterization, and cavity detection.

  9. Explosive Activity at Tungurahua Volcano: Analysis of Seismic and Infrasonic Data from 2006 - 2011

    NASA Astrophysics Data System (ADS)

    Steele, A. L.; Ruiz, M. C.; Lyons, J. J.

    2012-12-01

    propagated through the atmosphere and into the earth (η = acoustic energy/seismic energy), calculated from discrete explosions, is used to infer temporal changes in shallow conduit conditions across and between phases of activity. Typically, values in explosion VASR during the 5 years display relatively high acoustic partitioning (η ~ 1-1000), which we relate to a moderately open vent system. However, we attribute lower VASR during the early stages of May-July 2010 to an initially, partially choked conduit, an alteration in volcanic conditions that is reflected within the anomalous results of other statistical tests applied to this period of activity. Through continuous explosive degassing, we envision that the plug is eventually cleared, as an increase in explosion VASR is observed towards the latter stages of the active phase. Several statistical techniques applied to the 2006-2011 explosion dataset at Tungurahua were useful for revealing patterns in eruptive behavior, with statistical differences between periods of activity identifying a temporal evolution in eruption mechanism. Continued monitoring and a comparison of Tungurahua data with similar explosive records at other volcanoes, will lead to improved tools for analyzing sequences of explosive eruptions and more robust forecasting methods.

  10. Detecting and characterizing coal mine related seismicity in the Western U.S. using subspace methods

    NASA Astrophysics Data System (ADS)

    Chambers, Derrick J. A.; Koper, Keith D.; Pankow, Kristine L.; McCarter, Michael K.

    2015-11-01

    We present an approach for subspace detection of small seismic events that includes methods for estimating magnitudes and associating detections from multiple stations into unique events. The process is used to identify mining related seismicity from a surface coal mine and an underground coal mining district, both located in the Western U.S. Using a blasting log and a locally derived seismic catalogue as ground truth, we assess detector performance in terms of verified detections, false positives and failed detections. We are able to correctly identify over 95 per cent of the surface coal mine blasts and about 33 per cent of the events from the underground mining district, while keeping the number of potential false positives relatively low by requiring all detections to occur on two stations. We find that most of the potential false detections for the underground coal district are genuine events missed by the local seismic network, demonstrating the usefulness of regional subspace detectors in augmenting local catalogues. We note a trade-off in detection performance between stations at smaller source-receiver distances, which have increased signal-to-noise ratio, and stations at larger distances, which have greater waveform similarity. We also explore the increased detection capabilities of a single higher dimension subspace detector, compared to multiple lower dimension detectors, in identifying events that can be described as linear combinations of training events. We find, in our data set, that such an advantage can be significant, justifying the use of a subspace detection scheme over conventional correlation methods.

  11. A hybrid method for strong low-frequency noise suppression in prestack seismic data

    NASA Astrophysics Data System (ADS)

    Hu, Chunhua; Lu, Wenkai

    2014-09-01

    Low-frequency components are important portion of seismic data in exploration geophysics, and have great effects on seismic imaging of deep subsurface and full waveform inversion. Unfortunately, seismic data usually suffers from various kinds of noises and has low signal to noise ratio (SNR) in low-frequency band, although this situation has been improved by developments of acquisition technology. In this paper, we propose a low-frequency cascade filter (LFCF) in Fourier domain for strong low-frequency noise suppression in prestack gathers. LFCF includes a 1D adaptive median filter in f-x domain and a 2D notch filter in f-k domain, which is able to process high-amplitude swell noise, random noise, and seismic interference noise. We employ traces rearrangement and spike-detection mechanisms in adaptive f-x median filter, which can handle strong noise specifically, such as wide-spreading swell noise and tug noise. And a notch filter in f-k domain is designed to separate reflection signal and random noise by different apparent velocities. Through these means, our method can effectively attenuate low-frequency random and coherent noise while simultaneously protect the signal. Experiments on synthetic example and field data are conducted, and the results demonstrate that our method is practical and effective and can preserve signal down to 2 Hz.

  12. Seismic hydraulic fracture migration originated by successive deep magma pulses: The 2011-2013 seismic series associated to the volcanic activity of El Hierro Island

    NASA Astrophysics Data System (ADS)

    Díaz-Moreno, A.; Ibáñez, J. M.; De Angelis, S.; García-Yeguas, A.; Prudencio, J.; Morales, J.; Tuvè, T.; García, L.

    2015-11-01

    In this manuscript we present a new interpretation of the seismic series that accompanied eruptive activity off the coast of El Hierro, Canary Islands, during 2011-2013. We estimated temporal variations of the Gutenberg-Richter b value throughout the period of analysis, and performed high-precision relocations of the preeruptive and syneruptive seismicity using a realistic 3-D velocity model. Our results suggest that eruptive activity and the accompanying seismicity were caused by repeated injections of magma from the mantle into the lower crust. These magma pulses occurred within a small and well-defined volume resulting in the emplacement of fresh magma along the crust-mantle boundary underneath El Hierro. We analyzed the distribution of earthquake hypocenters in time and space in order to assess seismic diffusivity in the lower crust. Our results suggest that very high earthquake rates underneath El Hierro represent the response of a stable lower crust to stress perturbations with pulsatory character, linked to the injection of magma from the mantle. Magma input from depth caused large stress perturbations to propagate into the lower crust generating energetic seismic swarms. The absence of any preferential alignment in the spatial pattern of seismicity reinforces our hypothesis that stress perturbation and related seismicity, had diffusive character. We conclude that the temporal and spatial evolution of seismicity was neither tracking the path of magma migration nor it defines the boundaries of magma storage volumes such as a midcrustal sill. Our conceptual model considers pulsatory magma injection from the upper mantle and its propagation along the Moho. We suggest, within this framework, that the spatial and temporal distributions of earthquake hypocenters reflect hydraulic fracturing processes associated with stress propagation due to magma movement.

  13. Development of near surface seismic methods for urban and mining applications

    NASA Astrophysics Data System (ADS)

    Malehmir, Alireza; Brodic, Bojan; Place, Joachim; Juhlin, Christopher; Bastani, Mehrdad

    2014-05-01

    traditional landstreamers, which are either constructed for refraction and MASW methods or for reflection seismic imaging purposes. The landstreamer system, assembled in 2013, has so far been tested against planted 10- and 28-Hz coil-based sensors. Two preliminary surveys were performed in 2013, one for imaging the shallow (< 50 m) crystalline basement that controls mineralization at a location in northern Sweden and another one for site characterization at a planned access tunnel in the city of Stockholm. The comparison test showed that the digital sensors on the streamer provided superior results (in terms of resolution and sensitivity to noise) than the planted geophones, suggesting that digital sensors are more suitable for urban and mining applications. In the Stockholm survey, the system was coupled to twelve 3C-digital wireless sensors to cover areas where the access was restricted due to road traffic and existing city infrastructures. The wireless sensors were used to collect data in a passive mode during the survey; these data were later harvested and merged with the active data using GPS time stamps (nanoseconds accuracy). The system thus also allows a combination of active and passive seismic data acquisition if required. Preliminary results for the mining application show successful imaging of the shallow crystalline basement as a high-velocity (> 4000 m/s) media. Clear refracted and reflected arrivals are present in raw shot gathers. Future efforts will be geared to (i) exploiting information recorded on the horizontal components in order to extract rock mechanic parameters and anisotropy information, (ii) the development and application of a multi-component source to complement the landstreamer system, and (iii) a number of tests at underground sites. Acknowledgments: Formas, SGU, BeFo, SBUF, Skanska, Boliden, FQM and NGI

  14. Multivariable Observations of Pre and Co-Seismic Electromagnetic Activity in Peru: Past, Present and Future

    NASA Astrophysics Data System (ADS)

    Heraud, J. A.; Lira, J. A.; Montes, L.; Rosas, S.; Centa, V.; Bleier, T. E.

    2012-12-01

    The Mw8.0 earthquake in Pisco, Peru of August 15, 2007 was reported previously and shown to have produced extensive co-seismic luminescence away from the epicenter. Continued research will be presented in which a high coincidence exists between the location of the areas where the luminescence was video recorded and reported by qualified witnesses and the geological formation in the bay in which Jurassic and Cretaceous lithologic igneous components are present, a condition that contributes to the displacement of electric charges in the rock. Additionally, the San Lorenzo Island has become the focus of a new research effort due to the past record of pre-seismic EQLs reported and published in relation with the mega-earthquake of 1746, the previously reported co-seismic EQLs in 2007 and new evidence of pre-seismic EQLs reported one and a half days before a ML4.6 earthquake on July 29, 2012. New experiments are hitherto being deployed in San Lorenzo Island to pursue the identification of favorable conditions for the propagation of electric charges in connection with pressure on rocks due to seismic activity. Thus, continuously recording video cameras, charge potential measuring plates, recording of HF and VHF noise and the installation of a new magnetometer to detect pulse activity in the local magnetic field and twin (+/-) air conductivity sensors are being installed on the island. Additionally, a new rock experiment to analyze the displacement of charges with local rocks is under way. The expectation of a Mega earthquake in the Lima area is building up as we approach the third century without mayor seismic activity in the area so the deployment of a new network of five magnetometers for the Lima area has started.

  15. Evaluating the Relationship Between Seismicity and Subsurface Well Activity in Utah

    NASA Astrophysics Data System (ADS)

    Lajoie, L. J.; Bennett, S. E. K.

    2014-12-01

    Understanding the relationship between seismicity and subsurface well activity is crucial to evaluating the seismic hazard of transient, non-tectonic seismicity. Several studies have demonstrated correlations between increased frequency of earthquake occurrence and the injection/production of fluids (e.g. oil, water) in nearby subsurface wells in intracontinental settings (e.g. Arkansas, Colorado, Ohio, Oklahoma, Texas). Here, we evaluate all earthquake magnitudes for the past 20-30 years across the diverse seismotectonic settings of Utah. We explore earthquakes within 5 km and subsequent to completion dates of oil and gas wells. We compare seismicity rates prior to well establishment with rates after well establishment in an attempt to discriminate between natural and anthropogenic earthquakes in areas of naturally high background seismicity. In a few central Utah locations, we find that the frequency of shallow (0-10 km) earthquakes increased subsequent to completion of gas wells within 5 km, and at depths broadly similar to bottom hole depths. However, these regions typically correspond to mining regions of the Wasatch Plateau, complicating our ability to distinguish between earthquakes related to either well activity or mining. We calculate earthquake density and well density and compare their ratio (earthquakes per area/wells per area) with several published metrics of seismotectonic setting. Areas with a higher earthquake-well ratio are located in relatively high strain regions (determined from GPS) associated with the Intermountain Seismic Belt, but cannot be attributed to any specific Quaternary-active fault. Additionally, higher ratio areas do not appear to coincide with anomalously high heat flow values, where rocks are typically thermally weakened. Incorporation of timing and volume data for well injection/production would allow for more robust temporal statistical analysis and hazard analysis.

  16. Training toward Advanced 3D Seismic Methods for CO2 Monitoring, Verification, and Accounting

    SciTech Connect

    Christopher Liner

    2012-05-31

    The objective of our work is graduate and undergraduate student training related to improved 3D seismic technology that addresses key challenges related to monitoring movement and containment of CO{sub 2}, specifically better quantification and sensitivity for mapping of caprock integrity, fractures, and other potential leakage pathways. We utilize data and results developed through previous DOE-funded CO{sub 2} characterization project (DE-FG26-06NT42734) at the Dickman Field of Ness County, KS. Dickman is a type locality for the geology that will be encountered for CO{sub 2} sequestration projects from northern Oklahoma across the U.S. midcontinent to Indiana and Illinois. Since its discovery in 1962, the Dickman Field has produced about 1.7 million barrels of oil from porous Mississippian carbonates with a small structural closure at about 4400 ft drilling depth. Project data includes 3.3 square miles of 3D seismic data, 142 wells, with log, some core, and oil/water production data available. Only two wells penetrate the deep saline aquifer. In a previous DOE-funded project, geological and seismic data were integrated to create a geological property model and a flow simulation grid. We believe that sequestration of CO{sub 2} will largely occur in areas of relatively flat geology and simple near surface, similar to Dickman. The challenge is not complex geology, but development of improved, lower-cost methods for detecting natural fractures and subtle faults. Our project used numerical simulation to test methods of gathering multicomponent, full azimuth data ideal for this purpose. Our specific objectives were to apply advanced seismic methods to aide in quantifying reservoir properties and lateral continuity of CO{sub 2} sequestration targets. The purpose of the current project is graduate and undergraduate student training related to improved 3D seismic technology that addresses key challenges related to monitoring movement and containment of CO{sub 2

  17. An Idea for an Active Seismic Experiment on Mars in 2008

    NASA Technical Reports Server (NTRS)

    Lognonne, Ph.; Banerdt, B.; Giardini, D.; Costard, F.

    2001-01-01

    The detection of liquid water is of prime interest and should have deep implications in the understanding of the Martian hydrological cycle and also in exobiology. In the frame of the 2007 joint CNES-NASA mission to Mars, a set of 4 NETLANDERS developed by an European consortium is expected to be launched in June 2007. We propose to use a second spacecraft going or landing to Mars to release near one of the Netlander a series of artificial metallic meteorites, in order to perform an active seismic experiment providing a seismic profile of the crust and subsurface.

  18. A Global Sensitivity Analysis Method on Maximum Tsunami Wave Heights to Potential Seismic Source Parameters

    NASA Astrophysics Data System (ADS)

    Ren, Luchuan

    2015-04-01

    A Global Sensitivity Analysis Method on Maximum Tsunami Wave Heights to Potential Seismic Source Parameters Luchuan Ren, Jianwei Tian, Mingli Hong Institute of Disaster Prevention, Sanhe, Heibei Province, 065201, P.R. China It is obvious that the uncertainties of the maximum tsunami wave heights in offshore area are partly from uncertainties of the potential seismic tsunami source parameters. A global sensitivity analysis method on the maximum tsunami wave heights to the potential seismic source parameters is put forward in this paper. The tsunami wave heights are calculated by COMCOT ( the Cornell Multi-grid Coupled Tsunami Model), on the assumption that an earthquake with magnitude MW8.0 occurred at the northern fault segment along the Manila Trench and triggered a tsunami in the South China Sea. We select the simulated results of maximum tsunami wave heights at specific sites in offshore area to verify the validity of the method proposed in this paper. For ranking importance order of the uncertainties of potential seismic source parameters (the earthquake's magnitude, the focal depth, the strike angle, dip angle and slip angle etc..) in generating uncertainties of the maximum tsunami wave heights, we chose Morris method to analyze the sensitivity of the maximum tsunami wave heights to the aforementioned parameters, and give several qualitative descriptions of nonlinear or linear effects of them on the maximum tsunami wave heights. We quantitatively analyze the sensitivity of the maximum tsunami wave heights to these parameters and the interaction effects among these parameters on the maximum tsunami wave heights by means of the extended FAST method afterward. The results shows that the maximum tsunami wave heights are very sensitive to the earthquake magnitude, followed successively by the epicenter location, the strike angle and dip angle, the interactions effect between the sensitive parameters are very obvious at specific site in offshore area, and there

  19. Common features and peculiarities of the seismic activity at Phlegraean Fields, Long Valley, and Vesuvius

    USGS Publications Warehouse

    Marzocchi, W.; Vilardo, G.; Hill, D.P.; Ricciardi, G.P.; Ricco, C.

    2001-01-01

    We analyzed and compared the seismic activity that has occurred in the last two to three decades in three distinct volcanic areas: Phlegraean Fields, Italy; Vesuvius, Italy; and Long Valley, California. Our main goal is to identify and discuss common features and peculiarities in the temporal evolution of earthquake sequences that may reflect similarities and differences in the generating processes between these volcanic systems. In particular, we tried to characterize the time series of the number of events and of the seismic energy release in terms of stochastic, deterministic, and chaotic components. The time sequences from each area consist of thousands of earthquakes that allow a detailed quantitative analysis and comparison. The results obtained showed no evidence for either deterministic or chaotic components in the earthquake sequences in Long Valley caldera, which appears to be dominated by stochastic behavior. In contrast, earthquake sequences at Phlegrean Fields and Mount Vesuvius show a deterministic signal mainly consisting of a 24-hour periodicity. Our analysis suggests that the modulation in seismicity is in some way related to thermal diurnal processes, rather than luni-solar tidal effects. Independently from the process that generates these periodicities on the seismicity., it is suggested that the lack (or presence) of diurnal cycles is seismic swarms of volcanic areas could be closely linked to the presence (or lack) of magma motion.

  20. Feasibility of using a seismic surface wave method to study seasonal and weather effects on shallow surface soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this paper is to study the feasibility of using a seismic surface wave method to investigate seasonal and weather effects on shallow surface soils. In the study, temporal variations of subsurface soil properties were measured and monitored by using a combination of a new seismic su...

  1. More Than the Sum of Its Parts: Increased Information Content through a Combination of Ground-Penetrating-Radar and Seismic Methods on Temperate Glaciers.

    NASA Astrophysics Data System (ADS)

    Rabenstein, L.; Maurer, H.; Merz, K.; Lüthi, M. P.

    2014-12-01

    Over temperate glaciers images obtained from ground-penetrating-radar (GPR) are often blurred because electromagnetic waves are scattered on water pockets or by complex glacial bed topography, or damped due to a higher overall water content within the glacier. A combination of seismic and GPR surveying can increase the data information content and aid interpretation of subsurface structure. In September 2012 we acquired surface and borehole GPR and seismic data in the ablation zone of the Rhone Glacier located in central Switzerland. GPR data were acquired using antenna frequencies of 25, 50 and 100 MHz. Active reflection seismic data were recorded along a coincident profile across the glacier. Seismic waves were generated with small explosive sources spaced at 4m, and recorded on 30 Hz geophones at 2 m spacing. Both methods resulted in images showing a maximum depth of the glacier of approximately 130 m. However, the seismic image of the glacier bed was of much higher resolution and showed a clear primary reflection from the base, whereas the GPR image often showed several reflections of similar amplitude, above and from the bedrock interface, or no reflection at all. We interpreted a series of crenulations along the glacier bed reflector in the seismic image as melt water channels. This interpretation was supported by the intermittent nature of GPR glacier bed reflections, which are expected to be more sensitive to changes in water content than to the ice-rock interface. First break travel time inversions of the surface seismic data yielded velocities of 3320 m/s near the top of the glacier, and remarkably constant values of 3720 m/s at depths below 4.5m. However, travel time inversion of seismic data between boreholes which penetrated as far as the glacier bed, indicate a 3D anisotropy of seismic velocity, ranging from 3650 m/s horizontally across the glacier to 3850 m/s horizontally along the line of the glacier. Vertical seismic velocity was found to lie

  2. Seismic evidence for active underplating below the megathrust earthquake zone in Japan.

    PubMed

    Kimura, Hisanori; Takeda, Tetsuya; Obara, Kazushige; Kasahara, Keiji

    2010-07-01

    Determining the structure of subduction zones is important for understanding mechanisms for the generation of interplate phenomena such as megathrust earthquakes. The peeling off of the uppermost part of a subducting slab and accretion to the bottom of an overlying plate (underplating) at deep regions has been inferred from exhumed metamorphic rocks and deep seismic imaging, but direct seismic evidence of this process is lacking. By comparing seismic reflection profiles with microearthquake distributions in central Japan, we show that repeating microearthquakes occur along the bottom interface of the layer peeling off from the subducting Philippine Sea plate. This region coincides with the location of slow-slip events that may serve as signals for monitoring active underplating. PMID:20616277

  3. Seismic and satellite observations of calving activity at major glacier fronts in Greenland

    NASA Astrophysics Data System (ADS)

    Danesi, Stefania; Salimbeni, Simone; Urbini, Stefano; Pondrelli, Silvia; Margheriti, Lucia

    2016-04-01

    The interaction between oceans and large outlet glaciers in polar regions contributes to the budget of the global water cycle. We have observed the dynamic of sizeable outlet glaciers in Greenland by the analysis of seismic data collected by the regional seismic network Greenland Ice Sheet Monitoring Network (GLISN) trying also to find out correspondence in the glacier tongue evolution derived by the observation of satellite images. By studying the long-period seismic signals at stations located at the mouth of large fjords (e.g. ILULI, NUUG, KULLO), we identify major calving events through the detection of the ground flexure in response to seiche waves generated by iceberg detachments. 
For the time spanning the period between 2010-2014, we fill out calving-event catalogues which can be useful for the estimation of spatial and temporal variations in volume of ice loss at major active fronts in Greenland.

  4. Two-dimensional seismic attenuation images of Stromboli Island using active data

    NASA Astrophysics Data System (ADS)

    Prudencio, J.; Del Pezzo, E.; Ibáñez, J. M.; Giampiccolo, E.; Patané, D.

    2015-03-01

    In this work we present intrinsic and scattering seismic attenuation 2-D images of Stromboli Volcano. We used 21,953 waveforms from air gun shots fired by an oceanographic vessel and recorded at 33 inland and 10 ocean bottom seismometer seismic stations. Coda wave envelopes of the filtered seismic traces were fitted to the energy transport equation in the diffusion approximation, obtaining a couple of separate Qi and Qs in six frequency bands. Using numerically estimated sensitivity kernels for coda waves, separate images of each quality factor were produced. Results appear stable and robust. They show that scattering attenuation prevails over intrinsic attenuation. The scattering pattern shows a strong concordance with the tectonic lineaments in the area, while an area of high total attenuation coincides with the zone where most of the volcanic activity occurs. Our results provide evidence that the most important attenuation effects in volcanic areas are associated with the presence of geological heterogeneities.

  5. Seismic sequence near Zakynthos Island, Greece, April 2006: Identification of the activated fault plane

    NASA Astrophysics Data System (ADS)

    Serpetsidaki, A.; Sokos, E.; Tselentis, G.-A.; Zahradnik, J.

    2010-01-01

    The April 2006 earthquake sequence near Zakynthos (Western Greece) is analysed to identify the fault plane(-s). The sequence (33 events) was relocated to assess physical insight into the hypocenter uncertainty. Moment tensor solution of three major events was performed, simultaneously with the determination of the centroid position. Joint analysis of the hypocenter position, centroid position and nodal planes indicated sub-horizontal fault planes. Moment tensor solutions of 15 smaller events were performed under assumption that the source positions are those of the hypocenters (without seeking centroids). Their focal mechanisms are highly similar and agree with the analysis of the three major events. The preferable seismotectonic interpretation is that the whole sequence activated a single sub-horizontal fault zone at a depth of about 13 km, corresponding to the interplate subduction boundary. Considering that the Ionian Sea is a high-seismicity area, the identification of the seismic fault is significant for the seismic hazard investigation of the region.

  6. Method for enhancing low frequency output of impulsive type seismic energy sources and its application to a seismic energy source for use while drilling

    DOEpatents

    Radtke, Robert P; Stokes, Robert H; Glowka, David A

    2014-12-02

    A method for operating an impulsive type seismic energy source in a firing sequence having at least two actuations for each seismic impulse to be generated by the source. The actuations have a time delay between them related to a selected energy frequency peak of the source output. One example of the method is used for generating seismic signals in a wellbore and includes discharging electric current through a spark gap disposed in the wellbore in at least one firing sequence. The sequence includes at least two actuations of the spark gap separated by an amount of time selected to cause acoustic energy resulting from the actuations to have peak amplitude at a selected frequency.

  7. Overview on geophysical monitoring at the Ketzin CO2 storage site (Germany) using seismic and geoelectric methods (Invited)

    NASA Astrophysics Data System (ADS)

    Bergmann, P.; Ivandic, M.; Ivanova, A.; Juhlin, C.; Lueth, S.; Schmidt-Hattenberger, C.

    2013-12-01

    At Ketzin, a town close to Berlin, the first European onshore pilot scale project was initiated in 2004. After baseline characterization and drilling, CO2 injection was commenced in June 2008. As of August 2013, ~67 kilotons have been injected. Using one injection well, the CO2 is injected in a super-critical state into sandstones of the Stuttgart Formation, a saline aquifer at 620 m to 650 m depth. The depth of the Ketzin reservoir and injected mass of CO2 are not representative for CCS activities at an industrial scale. However, due to the relatively small amount of CO2 injected, combined with a complex storage reservoir, the site poses qualified conditions for testing of monitoring approaches. Consequently, a wide range of geophysical methods are in operation at the Ketzin site. Asides from well logging, both seismic methods and electric resistivity tomography (ERT) are being extensively applied. The applied survey setups comprise surface measurements, borehole measurements, and combined surface-downhole measurements. So far, the most comprehensive view onto the CO2 migration in the Ketzin reservoir is provided by two repeat 3D seismic surveys acquired in 2009 and 2012. They revealed a time-lapse seismic signal from the reservoir which indicates that the CO2 has progressively expanded to distances of 400-600 m away from the injection well by 2012. The apparent westward component of the plume migration observed in the 2009 data, is confirmed by a more pronounced westward component in the 2012 data. Consistent with the seismic monitoring, an increase in electrical resistivity around the injector was mapped by means of repeated surface-downhole ERT which indicates the presence of the injected CO2. These ERT surveys consist of current injections at the surface and voltage registration at the storage reservoir by means of a permanent electrode array that is installed in three wells (injector plus two monitoring wells). The imaged resistivity increase is consistent

  8. Methods and systems for low frequency seismic and infrasound detection of geo-pressure transition zones

    DOEpatents

    Shook, G. Michael; LeRoy, Samuel D.; Benzing, William M.

    2006-07-18

    Methods for determining the existence and characteristics of a gradational pressurized zone within a subterranean formation are disclosed. One embodiment involves employing an attenuation relationship between a seismic response signal and increasing wavelet wavelength, which relationship may be used to detect a gradational pressurized zone and/or determine characteristics thereof. In another embodiment, a method for analyzing data contained within a response signal for signal characteristics that may change in relation to the distance between an input signal source and the gradational pressurized zone is disclosed. In a further embodiment, the relationship between response signal wavelet frequency and comparative amplitude may be used to estimate an optimal wavelet wavelength or range of wavelengths used for data processing or input signal selection. Systems for seismic exploration and data analysis for practicing the above-mentioned method embodiments are also disclosed.

  9. Including Faults Detected By Near-Surface Seismic Methods in the USGS National Seismic Hazard Maps - Some Restrictions Apply

    NASA Astrophysics Data System (ADS)

    Williams, R. A.; Haller, K. M.

    2014-12-01

    Every 6 years, the USGS updates the National Seismic Hazard Maps (new version released July 2014) that are intended to help society reduce risk from earthquakes. These maps affect hundreds of billions of dollars in construction costs each year as they are used to develop seismic-design criteria of buildings, bridges, highways, railroads, and provide data for risk assessment that help determine insurance rates. Seismic source characterization, an essential component of hazard model development, ranges from detailed trench excavations across faults at the ground surface to less detailed analysis of broad regions defined mainly on the basis of historical seismicity. Though it is a priority for the USGS to discover new Quaternary fault sources, the discovered faults only become a part of the hazard model if there are corresponding constraints on their geometry (length and depth extent) and slip-rate (or recurrence interval). When combined with fault geometry and slip-rate constraints, near-surface seismic studies that detect young (Quaternary) faults have become important parts of the hazard source model. Examples of seismic imaging studies with significant hazard impact include the Southern Whidbey Island fault, Washington; Santa Monica fault, San Andreas fault, and Palos Verdes fault zone, California; and Commerce fault, Missouri. There are many more faults in the hazard model in the western U.S. than in the expansive region east of the Rocky Mountains due to the higher rate of tectonic deformation, frequent surface-rupturing earthquakes and, in some cases, lower erosion rates. However, the recent increase in earthquakes in the central U.S. has revealed previously unknown faults for which we need additional constraints before we can include them in the seismic hazard maps. Some of these new faults may be opportunities for seismic imaging studies to provide basic data on location, dip, style of faulting, and recurrence.

  10. A multi-decadal view of seismic methods for detecting precursors of magma movement and eruption

    NASA Astrophysics Data System (ADS)

    Chouet, Bernard A.; Matoza, Robin S.

    2013-02-01

    With the emergence of portable broadband seismic instrumentation, availability of digital networks with wide dynamic range, and development of new powerful analysis techniques made possible by greatly increased computer capacity, volcano seismology has now reached a mature stage where insights are rapidly being gained on the role played by magmatic and hydrothermal fluids in the generation of seismic waves. Volcanoes produce a wide variety of signals originating in the transport of magma and related hydrothermal fluids and their interaction with solid rock. Typical signals include (1) brittle failure earthquakes that reflect the response of the rock to stress changes induced by magma movement; (2) pressure oscillations accompanying the dynamics of liquids and gases in conduits and cracks; and (3) magma fracturing and fragmentation. Oscillatory behaviors within magmatic and hydrothermal systems are the norm and are the expressions of the complex rheologies of these fluids and nonlinear characteristics of associated processes underlying the release of thermo-chemical and gravitational energy from volcanic fluids along their ascent path. The interpretation of these signals and quantification of their source mechanisms form the core of modern volcano seismology. The accuracy to which the forces operating at the source can be resolved depends on the degree of resolution achieved for the volcanic structure. High-resolution tomography based on iterative inversions of seismic travel-time data can image three-dimensional structures at a scale of a few hundred meters provided adequate local short-period earthquake data are available. Hence, forces in a volcano are potentially resolvable for periods longer than ~ 1 s. In concert with techniques aimed at the interpretation of processes occurring in the fluid, novel seismic methods have emerged that are allowing the detection of stress changes in volcanic structures induced by magma movement. These methods include (1) ambient

  11. Seismic activity triggered by water wells in the Paraná Basin, Brazil

    NASA Astrophysics Data System (ADS)

    AssumpçãO, Marcelo; Yamabe, Tereza H.; Barbosa, José Roberto; Hamza, Valiya; Lopes, Afonso E. V.; Balancin, Lucas; Bianchi, Marcelo B.

    2010-07-01

    Triggered seismicity is commonly associated with deep water reservoirs or injection wells where water is injected at high pressure into the reservoir rock. However, earth tremors related solely to the opening of groundwater wells are extremely rare. Here we present a clear case of seismicity induced by pore-pressure changes following the drilling of water wells that exploit a confined aquifer in the intracratonic Paraná Basin of southeastern Brazil. Since 2004, shallow seismic activity, with magnitudes up to 2.9 and intensities V MM, has been observed near deep wells (120-200 m) that were drilled in early 2003 near the town of Bebedouro. The wells were drilled for irrigation purposes, cross a sandstone layer about 60-80 m thick and extract water from a confined aquifer in fractured zones between basalt flow layers. Seismic activity, mainly event swarms, has occurred yearly since 2004, mostly during the rainy season when the wells are not pumped. During the dry season when the wells are pumped almost continuously, the activity is very low. A seismographic network, installed in March 2005, has located more than 2000 microearthquakes. The events are less than 1 km deep (mostly within the 0.5 km thick basalt layer) and cover an area roughly 1.5 km × 5 km across. The seismicity generally starts in a small area and expands to larger distances with an equivalent hydraulic diffusivity ranging from 0.06 to 0.6 m2/s. Geophysical and geothermal logging of several wells in the area showed that water from the shallow sandstone aquifer enters the well at the top and usually forms waterfalls. The waterfalls flow down the sides of the wells and feed the confined, fractured aquifer in the basalt layer at the bottom. Two seismic areas are observed: the main area surrounds several wells that are pumped continuously during the dry season, and a second area near another well (about 10 km from the first area) that is not used for irrigation and not pumped regularly. The main area

  12. Characterising Seismicity at Alutu, an Actively Deforming Volcano in the Main Ethiopian Rift

    NASA Astrophysics Data System (ADS)

    Wilks, M.; Nowacki, A.; Kendall, J. M.; Wookey, J. M.; Biggs, J.; Bastow, I. D.; Ayele, A.; Bedada, T.

    2013-12-01

    The Main Ethiopian Rift (MER) provides a unique example of the tectonic and volcanic processes occuring during the transition from continental rifting to oceanic spreading. Situated 100 km south of Addis Ababa along the eastern rift margin, Alutu is a silicic stratovolcano that geodetic measurements (InSAR and GPS) have shown is actively deforming. Though the volcano has received relatively little scientific attention it is also a site of economic significance as a geothermal power plant resides within the caldera. As part of ARGOS (Alutu Research Geophysical ObservationS), a multi-disciplinary project aiming to investigate the magmatic and hydrothermal processes occuring at Alutu, a seismic network of 12 broadband seismometers was deployed in January 2012. Other components of ARGOS include InSAR, GPS, geologic mapping and magnetotellurics. From the seismic dataset, P- and S-wave arrivals across the array were manually picked and used to locate events using a non-linear earthquake location algorithm (NonLinLoc) and a predefined 1D velocity model. Perturbations were later applied to this velocity model to investigate the sensitivity of the locations and evaluate the true uncertainties of the solutions. Over 1000 events were successfully located during 2012, where picks were possible at 4 or more stations. Seismicity clusters at both shallow depths (z<2 km) beneath the caldera and at deeper depths of 5-15 km. There is a significant increase in seismicity during the rainy months, suggesting the shallow events may be related to the hydrothermal system. We interpret the deeper events as being magmatic in origin. Events are also located along the eastern border faults that bound the outer edges of the MER and highlights that seismicity arises concurrently via tectonic processes. An adapted version of Richter's original local magnitude scale (ML) to account for attenuation within the MER (Keir et al., 2006) was then used to compute magnitudes for the best located events

  13. Time Reversal Imaging of Seismic Sources by the Spectral Element Method.

    NASA Astrophysics Data System (ADS)

    Larmat, C.; Montagner, J.; Fink, M.; Capdeville, Y.; Clevede, E.; Tourin, A.

    2005-12-01

    The increasing power of computers and numerical methods (such as spectral elements methods) makes it possible to simulate more and more accurately the propagation of seismic waves in heterogeneous media and even to conceive new applications such as time reversal experiments within the three--dimensional Earth. These latter use the time reversal invariance and the spatial reciprocity of the wave equation. The idea is to construct a reverse movie of the propagation by sending the time--reversed recorded signals back from the receivers. The energy refocuses back at the location and the time of the original source. The concept of time-reversal has previously been successfully applied for acoustic waves in many fields such as medical imaging, oceanography and non destructive testing. For simulating the propagation of waves in the Earth as well as their time-reversed propagation, we used 2 different techniques, the normal mode summation technique (Gilbert and Dziewonski, 1975) and the spectral element method coupled with the modal solution (Capdeville et al., 2003). The first method is very accurate for 1D-earth models such as PREM whereas the second method is required for general heterogeneous 3D-models. For the first time, we have performed several synthetic and real data time-reversal experiments for seismic waves until the time of focalisation at the source. These tests show that sources are successfully localized in time and in space (though less accurately at depth), especially at very long period (> 200s) where the seismic properties of the Earth are well constrained. The corresponding movies are visible at the following address: http://www.gps.caltech.edu/~carene. We collect and send back the seismograms of the Global network of broadband seismic stations of the Federation of Digital Seismic Network (FDSN). We first consider a moderately large earthquake which can be considered as a point source in both time and space (Peru, June 23, 2001, Mw = 8.4). The

  14. Temporal variation of mass-wasting activity in Mount St. Helens crater, Washington, U. S. A. indicated by seismic activity

    SciTech Connect

    Mills, H.H. )

    1991-11-01

    In the crater of Mount St. Helens, formed during the eruption of 18 May 1980, thousands of rockfalls may occur in a single day, and some rock and dirty-snow avalanches have traveled more than 1 km from their source. Because most seismic activity in the crater is produced by mass wasting, the former can be used to monitor the latter. The number and amplitude of seismic events per unit time provide a generalized measure of mass-wasting activity. In this study 1-min averages of seismic amplitudes were used as an index of rockfall activity during summer and early fall. Plots of this index show the diurnal cycle of rockfall activity and establish that the peak in activity occurs in mid to late afternoon. A correlation coefficient of 0.61 was found between daily maximum temperature and average seismic amplitude, although this value increases to 0.72 if a composite temperature variable that includes the maximum temperature of 1 to 3 preceding days as well as the present day is used. Correlation with precipitation is much weaker.

  15. Tools and Methods for Visualizing and Representing Seismic Waves in College Classrooms

    NASA Astrophysics Data System (ADS)

    Wysession, M. E.; McDaris, J. R.; Mogk, D. W.

    2011-12-01

    Remarkable new advances in visualizing seismic waves now provide exciting opportunities for teaching and learning in the areas of geophysics dealing with earthquakes, earth structure, and seismic wave propagation. An online workshop entitled "Visualizing Seismic Waves for Teaching and Research" was held in the spring of 2011, sponsored by On the Cutting Edge (http://serc.carleton.edu/NAGTWorkshops/geophysics/seismic11/index.html). This workshop developed a comprehensive collection of visualizations, animations, sound records, and teaching lessons involving seismic waves that can be used throughout the geoscience curriculum, from introductory courses through upper division courses for undergraduate and graduate students. The results of the workshop are archived and publicly available through the One The Cutting Edge website at http://serc.carleton.edu/NAGTWorkshops/geophysics/visualizations.html. The goal of providing these visualizations is to help students (and colleagues in related geoscience disciplines) to understand the underlying principles of seismology, to visualize what earthquake waves look like as they propagate through Earth, and to be able to work with seismograms and the large volumes of seismological data that are now available. The visualizations (and auditizations) take many different forms. Some are synthetic records that can demonstrate both the physics of wave propagation and the structure of the earth (both global and regional). In some cases these are part of databases that generated representations for large earthquakes (e.g., tsunami or surface wave propagation). Others are ways of visualizing actual data, such as from the EarthScope Transportable Array, in ways that are engaging and intuitively understandable. These online web resources are available to the entire community, and everyone is encouraged to contribute and upload activities and demonstrations of their own so that others can benefit from them as well.

  16. Asymmetric active seismicity along the ultra-slow spreading Gakkel Ridge

    NASA Astrophysics Data System (ADS)

    Hopper, John R.; Voss, Peter H.; Lavier, Luc L.

    2015-04-01

    Ultra-slow spreading ridges are frequently characterised by spreading segments that are largely magma starved. Spreading along such segments does not occur by crustal creation/accretion processes such as intrusions, diking and volcanism, but rather by mechanical extension of the lithosphere, exposing the mantle to seafloor where it interacts with seawater to form serpentinite. Such exhumation is thought to occur along detachment faults that form concave down surfaces and produce an extensional geometry that is highly asymmetric. A consequence of all models that have been developed to simulate this type of extension is that stress and strain is focused primarily on the footwall block of the spreading system. This would predict that at any given time, only one side of the system should show active seismicity. In 2001, the Gakkel Ridge was extensively sampled by dredging during the AMORE cruise. These samples showed that the ridge is divided into distinct segments that today are either magmatically robust (only basalts recovered) or magmatically starved (dominantly serpentinised peridotite and gabbros recovered). We extracted earthquake data along the Gakkel Ridge from the global catalogs to investigate if these distinct segments exhibit any differences in active seismicity. We show that the western volcanic zone shows symmetric active seismicity, with earthquakes occurring on both sides of the ridge axis along a relatively restricted region. In contrast, the sparsely magmatic zone shows active seismicity dominantly along along the southern half of the ridge, with comparatively little seismicity to the north. These results are consistent with the proposed models for the formation of amagmatic spreading centers.

  17. Elevated Seismic Activity Beneath the Slumbering Morne aux Diables Volcano, Northern Dominica and the Monitoring Role of the Seismic Research Centre

    NASA Astrophysics Data System (ADS)

    Watts, R. B.; Robertson, R. E.; Abraham, W.; Cole, P.; de Roche, T.; Edwards, S.; Higgins, M.; Johnson, M.; Joseph, E. P.; Latchman, J.; Lynch, L.; Nath, N.; Ramsingh, C.; Stewart, R. C.

    2012-12-01

    Since June 2009, periods of elevated seismic activity have been experienced around the flanks of Morne Aux Diables Volcano in northern Dominica. This long-dormant volcano is a complex of 7 andesitic lava domes with a central depression where a cold soufrière is evident. Prior to this activity, seismicity was very quiet except for a short period in 2000 and an intense short-lived swarm in April 2003. The most recent earthquake activity has been regularly felt by residents in villages on all flanks of the complex. In Dec 09/Jan10, scientists from the Seismic Research Centre (SRC), based in Trinidad & Tobago, in collaboration with staff of the Office of Disaster Management (ODM) and Dominica Public Seismic Network (DPSN) improved the monitoring capacity around this volcano from 1 to 7 seismic stations. Earthquakes are determined to be volcano-tectonic in nature and located at shallow depths (<4 km) beneath the central depression. Additionally, in Jan/Feb 10 geothermal sampling was undertaken and 2 permanent GPS sites were deployed. Public information leaflets prepared by SRC scientists using a "Question & Answer" format have been distributed to concerned citizens whilst many public meetings were carried out by ODM staff. Field investigations indicate that the previous Late Pleistocene activity of Morne Aux Diables switched from Pelèan dome growth and gravitational collapse to more explosive pumice-falls and associated ignimbrites, both styles forming extensive pyroclastic fans around the central complex. The town of Portsmouth is located on one of these fans ~5 km southwest of the central depression. Sporadic, short bursts of seismic activity continue at the time of writing.

  18. Seismic activity near the Moriyoshi-zan volcano in Akita Prefecture, northeastern Japan: implications for geofluid migration and a midcrustal geofluid reservoir

    NASA Astrophysics Data System (ADS)

    Kosuga, M.

    2014-12-01

    The 2011 off the Pacific coast of Tohoku (Tohoku-oki) earthquake caused increased seismicity in many inland areas in Japan. A triggered seismic cluster north of the Moriyoshi-zan volcano in Akita prefecture, Tohoku District, is of interest in light of the contribution of geofluids to seismic activity. We observed an active seismic cluster characterized by the migration of seismicity and reflected/scattered phases. We relocated hypocenters of the cluster using data from temporal observations and the hypoDD location technique, which significantly increased the hypocentral accuracy. We interpreted a complex spatiotemporal variation of seismicity in the cluster as the migration of pore fluid pressure from multiple pressure sources. The hydraulic diffusivity of the cluster was in the range of 0.01 to 0.7 m2/s and increased with time, implying that the migration of hypocenters accelerated after a pathway for fluids was formed by fracturing of the wall rock during the initial stage of seismic activity. A prominent feature of the seismograms is a reflected/scattered phase observed at stations around the volcano. We regard the phase as S-to-S scattered waves and estimated the location of the scatterers using a back-projection method. The scatterers are inferred to be located about 5 km northwest of the Moriyoshi-zan volcano, at an approximate depth of 13 km. The Moriyoshi-zan area is one of the source areas of deep low-frequency earthquakes that have been interpreted as events generated by the migration of geofluids. The depth of the scatterers is close to the upper depth limit of low-frequency earthquakes. Thus, we interpret the observed scatterers to be a reservoir of geofluid that came from the uppermost mantle accompanying contemporaneous low-frequency earthquakes.

  19. Investigation of the relationships between seismic activities and radon level in western Turkey.

    PubMed

    Tarakçı, M; Harmanşah, C; Saç, M M; İçhedef, M

    2014-01-01

    The distribution of radon activity is determined from pre-earthquake data. Analysis using Normal, Gamma, Weibull and Rayleigh distributions indicates that the variation of radon levels in seismically active regions is best described by a normal distribution. It was observed that radon levels would change in compressive fault lines prior to earthquake. Besides that it tended to increase before the earthquake and then decrease towards the time of earthquake occurrences. PMID:24215813

  20. The contribution of activated processes to Q. [stress corrosion cracking in seismic wave attenuation

    NASA Technical Reports Server (NTRS)

    Spetzler, H. A.; Getting, I. C.; Swanson, P. L.

    1980-01-01

    The possible role of activated processes in seismic attenuation is investigated. In this study, a solid is modeled by a parallel and series configuration of dashpots and springs. The contribution of stress and temperature activated processes to the long term dissipative behavior of this system is analyzed. Data from brittle rock deformation experiments suggest that one such process, stress corrosion cracking, may make a significant contribution to the attenuation factor, Q, especially for long period oscillations under significant tectonic stress.

  1. Analysis of Seismic Activity of the last 15 Years Nearby Puerto Rico and Caribbean Region.

    NASA Astrophysics Data System (ADS)

    Huerta-Lopez, C. I.; Torres-Ortíz, D. M.; Fernández-Heredia, A. I.; Martínez-Cruzado, J. A.

    2015-12-01

    An earthquake catalog of the seismicity occurred during the last 15 years in the Caribbean region, nearby the vicinity of Puerto Rico Island (PRI) was compiled in order to capture the big picture of the regional seismic activity ratio and in particular at the epicentral regions of several historical and instrumentally recorded (during 2008-20015) large to moderate magnitude earthquakes occurred nearby PRI in onshore and offshore, which include the M6.4 earthquake of 01/13/2014, the largest earthquake recorded instrumentally nearby PRI. From the point of view of joint temporal-spatial distribution of epicenters, episodic temporal-spatial seismic activity is clearly seen as temporal-spatial concentrations during certain time intervals in different regions. These localized concentrations of epicenters that occur during certain time intervals in well localized/concentrated regions may suggest "seismic gaps" that shows no regular time interval, neither spatial pattern. In the epicentral region of the M6.4 01/13/2014 earthquake and the historical Mona Passage M7.5 earthquake of 10/11/1918, episodic concentrations in time and space of small magnitude earthquakes epicenters is evident, however do not show temporal pattern. Preliminary results of statistical analysis of an ongoing research in terms of the parameter b (Gutenberg-Richter relationship), and the Omori's law with the aim to relate the tectonic framework of the region (or sub-regions) such as structural heterogeneity stress are here presented/discussed.

  2. Combining statistical and physics-based methods for predicting induced seismic hazard during reservoir stimulation

    NASA Astrophysics Data System (ADS)

    Gischig, V. S.; Mena Cabrera, B.; Goertz-Allmann, B.; Wiemer, S.

    2012-12-01

    observed data. We demonstrate that the model can reasonably reproduce both the temporal evolution of observed event statistics, and minimally the extent of at the seismic cloud recorded during the Basel reservoir stimulation in 2006. We also argue that triggering pressure is at a realistic order of magnitude, because modeled and measured wellhead pressure curves are in good agreement. Furthermore, the model is tested against observations in a pseudo-prospective manner, and compared to the existing purely statistical forecasting methods. Finally, we use the calibrated model to explore different injection scenarios, and their consequences for seismic hazard. Translating the calibrated models with different injection scenarios into probabilistic seismic hazard allows us to qualitatively compare their effects on the probability of occurrence of a hazardous event. Our modeling strategy and statistical testing procedure forms a test-bed that can be used to investigate the forecasting capabilities of future models developed towards higher physical complexity.

  3. Application of GPR and seismic methods in landslides investigation and determination of hydrogeological conditions

    NASA Astrophysics Data System (ADS)

    Czaja, Klaudia; Matuła, Rafał

    2013-04-01

    Ground Penetrating Radar (GPR) belongs to non-invasive geophysical methods which use an artificially induced electromagnetic field as the way for inspection. GPR is applied not only to recognition of shallow geological structure but also to archeological studies. The basic assumption of the applicability of GPR is the existance of a distinct boundary between two lithological horizons defined by a change in permittivity values, which results in a change in electromagnetic wave velocity. For that reason this method is used to locate empty spaces and saturated zones. The purpose of this measurements was to determine the details of the sliding body, including the thickness and lateral extension of the landslide material, the depth of the sliding surface and water content of the subsurface. What is more correlation between GPR and seismic methods was searched. Studied area was located in the Southern part of Poland. Geological structure is characteristic for Carpathian flysch - overlaying claystones, shales and sandstones. Measurements were carried out using GPR equipment from the Swedish company Mala Geoscience. Due to the required depth range and resolution unshielded antennas with frequencies from 25 MHz to 200 MHz were used. Profiles were traced parallel to the landslide axis. Following forms of GPR survey were applied: CO (common offset), CMP (common mid point), WARR (wide-angle reflection-refraction). Modeling attempt electromagnetic field distribution in the medium was undertaken to select the most appropriate measurement parameters and to improve the interpretation. Programme GPRMax2D v. 2.0 was used to create models. The GPR numerical analysis uses the finite - difference time - domain method (FDTD). The FDTD approach to the numerical solution of Maxwell's equations consist of discretization both the space and the time continua. Due to geological structure (presence of low resistivity clays and shales) attenuation of electromagnetic wave was high. In order to

  4. a method of gravity and seismic sequential inversion and its GPU implementation

    NASA Astrophysics Data System (ADS)

    Liu, G.; Meng, X.

    2011-12-01

    In this abstract, we introduce a gravity and seismic sequential inversion method to invert for density and velocity together. For the gravity inversion, we use an iterative method based on correlation imaging algorithm; for the seismic inversion, we use the full waveform inversion. The link between the density and velocity is an empirical formula called Gardner equation, for large volumes of data, we use the GPU to accelerate the computation. For the gravity inversion method , we introduce a method based on correlation imaging algorithm,it is also a interative method, first we calculate the correlation imaging of the observed gravity anomaly, it is some value between -1 and +1, then we multiply this value with a little density ,this value become the initial density model. We get a forward reuslt with this initial model and also calculate the correaltion imaging of the misfit of observed data and the forward data, also multiply the correaltion imaging result a little density and add it to the initial model, then do the same procedure above , at last ,we can get a inversion density model. For the seismic inveron method ,we use a mothod base on the linearity of acoustic wave equation written in the frequency domain,with a intial velociy model, we can get a good velocity result. In the sequential inversion of gravity and seismic , we need a link formula to convert between density and velocity ,in our method , we use the Gardner equation. Driven by the insatiable market demand for real time, high-definition 3D images, the programmable NVIDIA Graphic Processing Unit (GPU) as co-processor of CPU has been developed for high performance computing. Compute Unified Device Architecture (CUDA) is a parallel programming model and software environment provided by NVIDIA designed to overcome the challenge of using traditional general purpose GPU while maintaining a low learn curve for programmers familiar with standard programming languages such as C. In our inversion processing

  5. Seismic images of the active fault system in the Yunlin and Chiayi area of Taiwan.

    NASA Astrophysics Data System (ADS)

    Sun, Wei-Hsiang; Shih, Ruey-Chyuan

    2015-04-01

    The Yunlin and Chiayi area in western Taiwan are well known of having a higher risk of earthquake disaster. The main fault system that controls the structure deformation in this area consists of the Chiuchiungkeng fault, the Meishan fault, and the Gukeng fault. According to historical records, the 1906 Meishan earthquake, magnitude 7.1, was triggered by the right-lateral strike-slip fault Meishan fault. Previous Seismic surveys showed that the Meishan fault is a high angle fault with flower structure. The Chiuchiungkeng fault is a thrust fault, located at front of the western foothills. Formations on the hanging wall and foot wall of the fault, both dipping to the east with different angles, can be identified from seismic images. The Gukeng fault was never been studied before. From the recent study of GPS monitoring, we may found that the velocity field near the Gukeng fault had a significant difference at both side of the fault. In addition, there is other information showed that there exists an aseismic gap around the fault. The above phenomena could be considered as a stress accumulation along the Gukeng fault. In the other words, the Gukeng fault could be playing an important role of controlling the regional surface deformation and seismicity distribution in this area. In this case, it will be worthwhile of knowing where the Gukeng fault is, and its subsurface structure. In this presentation, we will show our study of the subsurface structure of the Gukeng fault by using the seismic exploration method. The data consist of the shallow seismic reflection images those conducted by ourselves and the deeper seismic profiles acquired by CPC. Three dimensional relationships between the Gukeng fault, the Meishan fault, the Chiuchiungkeng fault, and other structures such as the Hsiaomei anticline will be illustrated as well.

  6. Seismic activity in the Sunnyside mining district, Carbon and Emery Counties, Utah, during 1968

    USGS Publications Warehouse

    Dunrud, C. Richard; Maberry, John O.; Hernandez, Jerome H.

    1970-01-01

    More than 20,000 local earth tremors were recorded by the seismic monitoring network in the Sunnyside mining district during 1968. This is about 40 percent of the number of tremors recorded by the network in 1967. In 1968 a total of 281 tremors were of sufficient magnitude to be located accurately--about 50 percent of the number of tremors in 1967 that were located accurately. As in previous years, nearly all the earth tremors originated near, or within a few thousand feet of, the mine workings. This distribution indicates that mine-induced stress changes caused most of the seismic activity. However, over periods of weeks and months there were significant changes in the distribution of seismic activity caused by tremors that were not directly related to mining but probably were caused by adjustment of natural stresses 6r by a complex combination of both natural and mine-induced stress changes. In 1968 the distribution of tremor hypocenters varied considerably with time, relative to active mining areas and to faults present in the mine workings. During the first 6 months, most tremors originated along or near faults that trend close to or through the active mine workings. However, in the last 6 months, the tremor hypocenters tended to concentrate in the rock mass closer to, or around, the active mining areas. This shift in concentration of seismic activity with time has been noted throughout the district many times since recording began in 1963, and is apparently caused by spontaneous releases of stored strain energy resulting from mine-induced stress changes. These spontaneous releases of strain energy, together with rock creep, apparently are the mechanism of adjustment within the rock mass toward equilibrium conditions, which are continually disrupted by mining. Although potentially hazardous bumps were rare in the Sunnyside mining district during 1968, smaller bumps and rock falls were more common in a given active mining area whenever hypocenters of larger

  7. Elevated shear strength of sediments on active margins: Evidence for seismic strengthening

    NASA Astrophysics Data System (ADS)

    Sawyer, Derek E.; DeVore, Joshua R.

    2015-12-01

    Earthquakes are a primary trigger of submarine landslides, yet some of the most seismically active areas on Earth show a surprisingly low frequency of submarine landslides. Here we show that within the uppermost 100 m below seafloor (mbsf) in previously unfailed sediment, active margins have elevated shear strength by a factor of 2-3 relative to the same interval on passive margins. The elevated shear strength is seen in a global survey of undrained shear strength with depth as well as a normalized analysis that accounts for lithology and stress state. The enhanced shear strength is highest within the uppermost 10 mbsf. These results indicate that large areas of modern day slopes on active margins have enhanced slope stability, which may explain the relative paucity of landslides. These findings lend support to the seismic strengthening hypothesis that the repeated exposure to earthquake energy gradually increases shear strength by shear-induced compaction.

  8. Application of the Huang-Hilbert transform and natural time to the analysis of seismic electric signal activities

    SciTech Connect

    Papadopoulou, K. A.; Skordas, E. S.

    2014-12-01

    The Huang method is applied to Seismic Electric Signal (SES) activities in order to decompose them into their components, named Intrinsic Mode Functions (IMFs). We study which of these components contribute to the basic characteristics of the signal. The Hilbert transform is then applied to the IMFs in order to determine their instantaneous amplitudes. The results are compared with those obtained from the analysis in a new time domain termed natural time, after having subtracted the magnetotelluric background from the original signal. It is shown that these instantaneous amplitudes, when combined with the natural time analysis, can be used for the distinction of SES from artificial noises.

  9. Active Learning Methods

    ERIC Educational Resources Information Center

    Zayapragassarazan, Z.; Kumar, Santosh

    2012-01-01

    Present generation students are primarily active learners with varied learning experiences and lecture courses may not suit all their learning needs. Effective learning involves providing students with a sense of progress and control over their own learning. This requires creating a situation where learners have a chance to try out or test their…

  10. Method and apparatus for coupling seismic sensors to a borehole wall

    DOEpatents

    West, Phillip B.

    2005-03-15

    A method and apparatus suitable for coupling seismic or other downhole sensors to a borehole wall in high temperature and pressure environments. In one embodiment, one or more metal bellows mounted to a sensor module are inflated to clamp the sensor module within the borehole and couple an associated seismic sensor to a borehole wall. Once the sensing operation is complete, the bellows are deflated and the sensor module is unclamped by deflation of the metal bellows. In a further embodiment, a magnetic drive pump in a pump module is used to supply fluid pressure for inflating the metal bellows using borehole fluid or fluid from a reservoir. The pump includes a magnetic drive motor configured with a rotor assembly to be exposed to borehole fluid pressure including a rotatable armature for driving an impeller and an associated coil under control of electronics isolated from borehole pressure.

  11. On the validation of seismic imaging methods: Finite frequency or ray theory?

    SciTech Connect

    Maceira, Monica; Larmat, Carene; Porritt, Robert W.; Higdon, David M.; Rowe, Charlotte A.; Allen, Richard M.

    2015-01-23

    We investigate the merits of the more recently developed finite-frequency approach to tomography against the more traditional and approximate ray theoretical approach for state of the art seismic models developed for western North America. To this end, we employ the spectral element method to assess the agreement between observations on real data and measurements made on synthetic seismograms predicted by the models under consideration. We check for phase delay agreement as well as waveform cross-correlation values. Based on statistical analyses on S wave phase delay measurements, finite frequency shows an improvement over ray theory. Random sampling using cross-correlation values identifies regions where synthetic seismograms computed with ray theory and finite-frequency models differ the most. Our study suggests that finite-frequency approaches to seismic imaging exhibit measurable improvement for pronounced low-velocity anomalies such as mantle plumes.

  12. On the validation of seismic imaging methods: Finite frequency or ray theory?

    DOE PAGESBeta

    Maceira, Monica; Larmat, Carene; Porritt, Robert W.; Higdon, David M.; Rowe, Charlotte A.; Allen, Richard M.

    2015-01-23

    We investigate the merits of the more recently developed finite-frequency approach to tomography against the more traditional and approximate ray theoretical approach for state of the art seismic models developed for western North America. To this end, we employ the spectral element method to assess the agreement between observations on real data and measurements made on synthetic seismograms predicted by the models under consideration. We check for phase delay agreement as well as waveform cross-correlation values. Based on statistical analyses on S wave phase delay measurements, finite frequency shows an improvement over ray theory. Random sampling using cross-correlation values identifiesmore » regions where synthetic seismograms computed with ray theory and finite-frequency models differ the most. Our study suggests that finite-frequency approaches to seismic imaging exhibit measurable improvement for pronounced low-velocity anomalies such as mantle plumes.« less

  13. Method Apparatus And System For Detecting Seismic Waves In A Borehole

    DOEpatents

    West, Phillip B.; Sumstine, Roger L.

    2006-03-14

    A method, apparatus and system for detecting seismic waves. A sensing apparatus is deployed within a bore hole and may include a source magnet for inducing a magnetic field within a casing of the borehole. An electrical coil is disposed within the magnetic field to sense a change in the magnetic field due to a displacement of the casing. The electrical coil is configured to remain substantially stationary relative to the well bore and its casing along a specified axis such that displacement of the casing induces a change within the magnetic field which may then be sensed by the electrical coil. Additional electrical coils may be similarly utilized to detect changes in the same or other associated magnetic fields along other specified axes. The additional sensor coils may be oriented substantially orthogonally relative to one another so as to detect seismic waves along multiple orthogonal axes in three dimensional space.

  14. Near-Surface Seismic Refraction Methods to Characterize Areas of Karst Geology near Carlsbad, NM

    NASA Astrophysics Data System (ADS)

    Cafferky, S.; Bonal, N. D.; Barnhart, K.

    2012-12-01

    Near-surface seismic refraction methods applied to karst geology can give some ideas as to the nature of the void spaces as well as the stratigraphy of the area. A seismic geophone array was laid out near Carlsbad, NM, an area known to contain karst features. Using an impact (sledge hammer), seismic data was collected along two intersecting lines of geophones as well as two gridded areas to get three-dimensional information. The data was picked for the first arrivals of the P-wave, which were graphed and examined for changes in slope and inconsistencies in shape. The data analyzed shows a two-layer model and some inconsistencies such as polarity reversals and delayed arrival times that may represent karst features. Additional processing is used to enhances these features and map them in three-dimensions. The mapped features are compared with known karst features in the area (e.g. sinkholes) for ground-truth information. These methods may be used in the future for detection and classification of other near-surface voids. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  15. PRESS40: a project for involving students in active seismic risk mitigation

    NASA Astrophysics Data System (ADS)

    Barnaba, Carla; Contessi, Elisa; Rosa Girardi, Maria

    2016-04-01

    To memorialize the anniversary of the 1976 Friuli earthquake, the Istituto Statale di Istruzione Superiore "Magrini Marchetti" in Gemona del Friuli (NE Italy), with the collaboration of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), has promoted the PRESS40 Project (Prevenzione Sismica nella Scuola a 40 anni dal terremoto del Friuli, that in English sounds like "Seismic Prevention at School 40 years later the Friuli earthquake"). The project has developed in the 2015-2016 school year, starting from the 40th anniversary of the Friuli earthquake, and it aims to disseminate historical memory, seismic culture and awareness of seismic safety in the young generations, too often unconscious of past experiences, as recent seismic hazard perception tests have demonstrated. The basic idea of the PRESS40 Project is to involve the students in experimental activities to be active part of the seismic mitigation process. The Project is divided into two main parts, the first one in which students learn-receive knowledge from researchers, and the second one in which they teach-bring knowledge to younger students. In the first part of the project, 75 students of the "Magrini Marchetti" school acquired new geophysical data, covering the 23 municipalities from which they come from. These municipalities represent a wide area affected by the 1976 Friuli earthquake. In each locality a significant site was examined, represented by a school area. At least, 127 measurements of ambient noise have been acquired. Data processing and interpretation of all the results are still going on, under the supervision of OGS researchers.The second part of the project is planned for the early spring, when the students will present the results of geophysical survey to the younger ones of the monitored schools and to the citizens in occasion of events to commemorate the 40th anniversary of the Friuli earthquake.

  16. Seismicity and eruptive activity at Fuego Volcano, Guatemala: February 1975 -January 1977

    USGS Publications Warehouse

    Yuan, A.T.E.; McNutt, S.R.; Harlow, D.H.

    1984-01-01

    We examine seismic and eruptive activity at Fuego Volcano (14??29???N, 90?? 53???W), a 3800-m-high stratovolcano located in the active volcanic arc of Guatemala. Eruptions at Fuego are typically short-lived vulcanian eruptions producing ash falls and ash flows of high-alumina basalt. From February 1975 to December 1976, five weak ash eruptions occurred, accompanied by small earthquake swarms. Between 0 and 140 (average ??? 10) A-type or high-frequency seismic events per day with M > 0.5 were recorded during this period. Estimated thermal energies for each eruption are greater by a factor of 106 than cumulative seismic energies, a larger ratio than that reported for other volcanoes. Over 4000 A-type events were recorded January 3-7, 1977 (cumulative seismic energy ??? 109 joules), yet no eruption occurred. Five 2-hour-long pulses of intense seismicity separated by 6-hour intervals of quiescence accounted for the majority of events. Maximum likelihood estimates of b-values range from 0.7 ?? 0.2 to 2.1 ?? 0.4 with systematically lower values corresponding to the five intense pulses. The low values suggest higher stress conditions. During the 1977 swarm, a tiltmeter located 6 km southeast of Fuego recorded a 14 ?? 3 microradian tilt event (down to SW). This value is too large to represent a simple change in the elastic strain field due to the earthquake swarm. We speculate that the earthquake swarm and tilt are indicative of subsurface magma movement. ?? 1984.

  17. Seismic activity near the Moriyoshi-zan volcano in Akita Prefecture, northeastern Japan: implications for geofluid migration and a midcrustal geofluid reservoir

    NASA Astrophysics Data System (ADS)

    Kosuga, Masahiro

    2014-12-01

    The 2011 off the Pacific coast of Tohoku (Tohoku-oki) earthquake caused increased seismicity in many inland areas in Japan. A seismic cluster north of the Moriyoshi-zan volcano in Akita prefecture, Tohoku District, is of interest in light of the contribution of geofluids to seismic activity. We observed a seismic cluster characterized by the migration of seismicity and reflected/scattered phases. We relocated hypocenters of the cluster using data from temporal observations and the hypoDD location technique, which significantly increased the hypocentral accuracy. We interpreted a complex spatiotemporal variation of seismicity in the cluster as the migration of pore fluid pressure from multiple pressure sources. The hydraulic diffusivity of the cluster was in the range of 0.01 to 0.7 m2/s and increased with time, implying that the migration of hypocenters accelerated after a pathway for fluids was formed by fracturing of the wall rock during the initial stage of seismic activity. A prominent feature of the seismograms is a reflected/scattered phase observed at stations around the volcano. We regard the phase as S-to- S scattered waves and estimated the location of the scatterers using a back-projection method. The scatterers are inferred to be located about 5 km northwest of the Moriyoshi-zan volcano, at an approximate depth of 13 km. The Moriyoshi-zan area is one of the source areas of deep low-frequency earthquakes that have been interpreted as events generated by the migration of geofluids. The depth of the scatterers is close to the upper limit of the depth at which low-frequency earthquakes occur. Thus, we interpret the observed scatterers to be a reservoir of geofluid that came from the uppermost mantle accompanying contemporaneous low-frequency earthquakes.

  18. Imaging spatial and temporal seismic source variations at Sierra Negra Volcano, Galapagos Islands using back-projection methods

    NASA Astrophysics Data System (ADS)

    Kelly, C. L.; Lawrence, J. F.; Ebinger, C. J.

    2013-12-01

    Imaging spatial and temporal seismic source variations at Sierra Negra Volcano, Galapagos Islands using back-projection methods Cyndi Kelly1, Jesse F. Lawrence1, Cindy Ebinger2 1Stanford University, Department of Geophysics, 397 Panama Mall, Stanford, CA 94305, USA 2University of Rochester, Department of Earth and Environmental Science, 227 Hutchison Hall, Rochester, NY 14627, USA Low-magnitude seismic signals generated by processes that characterize volcanic and hydrothermal systems and their plumbing networks are difficult to observe remotely. Seismic records from these systems tend to be extremely 'noisy', making it difficult to resolve 3D subsurface structures using traditional seismic methods. Easily identifiable high-amplitude bursts within the noise that might be suitable for use with traditional seismic methods (i.e. eruptions) tend to occur relatively infrequently compared to the length of an entire eruptive cycle. Furthermore, while these impulsive events might help constrain the dynamics of a particular eruption, they shed little insight into the mechanisms that occur throughout an entire eruption sequence. It has been shown, however, that the much more abundant low-amplitude seismic 'noise' in these records (i.e. volcanic or geyser 'tremor') actually represents a series of overlapping low-magnitude displacements that can be directly linked to magma, fluid, and volatile movement at depth. This 'noisy' data therefore likely contains valuable information about the processes occurring in the volcanic or hydrothermal system before, during and after eruption events. In this study, we present a new method to comprehensively study how the seismic source distribution of all events - including micro-events - evolves during different phases of the eruption sequence of Sierra Negra Volcano in the Galapagos Islands. We apply a back-projection search algorithm to image sources of seismic 'noise' at Sierra Negra Volcano during a proposed intrusion event. By analyzing

  19. Locadiff with ambient seismic noise : theoretical background and application to monitoring volcanoes and active faults.

    NASA Astrophysics Data System (ADS)

    Larose, Eric; Obermann, Anne; Planes, Thomas; Rossetto, Vincent; Margerin, Ludovic; Sens-Schoenfelder, Christoph; Campillo, Michel

    2015-04-01

    This contribution will cover recent theoretical, numerical, and field data processing developments aiming at modeling how coda waves are perturbed (in phase and amplitude) by mechanical changes in the crust. Using continuous ambient seismic noise, we cross-correlate data every day and compare the coda of the correlograms. We can relative velocity changes and waveform decorrelation along the year, that are related to mechanical changes in the shallow crust, associated to the seismic or volcanic activity, but also to environmental effects such as hydrology. Bibliography : Anne Obermann, Thomas Planes, Eric Larose and Michel Campillo, Imaging pre- and co-eruptive structural changes of a volcano with ambient seismic noise, J. Geophys. Res. 118 6285-6294 (2013). A. Obermann, B. Froment, M. Campillo, E. Larose, T. Planès, B. Valette, J. H. Chen, and Q. Y. Liu, Seismic noise correlations to image structural and mechanical changes associated with the Mw7.9 2008-Wenchuan earthquake, J. Geophys. Res. Solid Earth, 119, 1-14,(2014). Thomas Planès, Eric Larose, Ludovic Margerin, Vincent Rossetto, Christoph Sens-Schoenfelder, Decorrelation and phase-shift of coda waves induced by local changes : Multiple scattering approach and numerical validation, Waves in Random and Complex Media 24, 99-125, (2014)

  20. Seismicity on the western Greenland Ice Sheet: Surface fracture in the vicinity of active moulins

    SciTech Connect

    Carmichael, Joshua D.; Joughin, Ian; Behn, Mark D.; Das, Sarah; King, Matt A.; Stevens, Laura; Lizarralde, Dan

    2015-06-25

    We analyzed geophone and GPS measurements collected within the ablation zone of the western Greenland Ice Sheet during a ~35 day period of the 2011 melt season to study changes in ice deformation before, during, and after a supraglacial lake drainage event. During rapid lake drainage, ice flow speeds increased to ~400% of winter values, and icequake activity peaked. At times >7 days after drainage, this seismicity developed variability over both diurnal and longer periods (~10 days), while coincident ice speeds fell to ~150% of winter values and showed nightly peaks in spatial variability. Approximately 95% of all detected seismicity in the lake basin and its immediate vicinity was triggered by fracture propagation within near-surface ice (<330 m deep) that generated Rayleigh waves. Icequakes occurring before and during drainage frequently were collocated with the down flow (west) end of the primary hydrofracture through which the lake drained but shifted farther west and outside the lake basin after the drainage. We interpret these results to reveal vertical hydrofracture opening and local uplift during the drainage, followed by enhanced seismicity and ice flow on the downstream side of the lake basin. This region collocates with interferometric synthetic aperture radar-measured speedup in previous years and could reflect the migration path of the meltwater supplied to the bed by the lake. The diurnal seismic signal can be associated with nightly reductions in surface melt input that increase effective basal pressure and traction, thereby promoting elevated strain in the surficial ice.

  1. A New Method for Calculating Seismic Velocities in Antigorite-Bearing Serpentinites

    NASA Astrophysics Data System (ADS)

    Watanabe, T.; Shirasugi, Y.; Michibayashi, K.

    2013-12-01

    Serpentinites play key roles in subduction zone processes including transportation of water, seismogenesis and slab-mantle coupling. Seismological mapping of serpentinites will give us insights into these processes. In order to interpret seismological observations, we must have a good understanding of seismic properties of serpentinites. Determination of elastic constants of antigorite (Bezacier et al., 2010; 2013) has enabled us to calculate the Voigt and Reuss bounds of seismic velocities in serpentinites with given modal compositions and CPOs. Although the Hill averages have been often employed for the prediction of velocity, it should be noted that they have large uncertainties. There is considerable difference between the two bounds due to the strong elastic anisotropy of antigorite. Microstructural variables like the grain shape and the spatial distribution of grains should be taken into account for a better prediction. We propose a calculation method which accounts for the grain shape of strongly dimensionally anisotropic minerals like micas and serpentines. A mineral grain is treated as an oblate spheroid, and embedded in a homogeneous matrix. Strain in the matrix is disturbed by embedded spheroidal inclusions, and evaluated by Eshelby's method (Eshelby, 1957). Elastic constants of the composite material are calculated by differentiating the elastic energy with respect to strain. We employed the differential effective medium method, which repeats introducing inclusions by a small amount and calculates effective elastic constants by evaluating the change in elastic strain energy density from the previous step. This method evaluates implicitly the stress and strain disturbance due to other inclusions. Our method is an extension of the method of Nishizawa and Yoshino (2001), and can be applied to a distributed geometrical orientation of mineral grains. Comparison was made between calculated and measured velocities in four natural antigorite

  2. Seismic activity, inferred crustal stresses and seismotectonics in the Rana region, Northern Norway

    NASA Astrophysics Data System (ADS)

    Hicks, Erik C.; Bungum, Hilmar; Lindholm, Conrad D.

    2000-10-01

    The seismotectonic significance of the Rana region is known both from the fact that this was the location of the largest known earthquake in Fennoscandia in recent times, the MS 5.8-6.2 earthquake of August 31, 1819, and from its relatively high, constant seismic activity also in the 20th century. In order to study this region in more detail, a local seismic network has been in operation there since July 1997, as part of the NEONOR (Neotectonics in Norway) project. The network was primarily designed to detect possible activity on the Båsmoen fault which runs ˜50 km subparallel to the Rana fjord, and which shows signs of likely post glacial activity. The results have revealed a quite complex spatio-temporal distribution of seismic activity, and has also shown no activity on the Båsmoen fault itself. During the first 18 months of operation (July 1997-January 1999), the network has detected 373 locatable seismic events, of which 267 were local earthquakes. Most of these earthquakes occurred in five groups in the western parts of the network. All five groups had similar NNW-ESW trends in epicenter locations, and all have shallow foci (2-12 km), similar to what has also been found earlier for other concentrated earthquake zones in Northern Norway, and the magnitude range is between ML 0.1 and 2.8. Earthquake focal mechanism solutions within the network reveal a predominance for normal faulting with the tensional stress axis perpendicular do the coastline (implying an unusual coast-parallel orientation of the principal horizontal compressive stress). The earthquakes occur in a region of maximum post-glacial uplift gradients, which supports deglaciation flexure as a viable explanation for these earthquakes. A certain influence from more local factors, however, tied in general to crustal in homogeneities, cannot be ruled out.

  3. Fault activation after vigorous eruption: the December 8, 2015 seismic swarm at Mt. Etna

    NASA Astrophysics Data System (ADS)

    Alparone, Salvatore; Bonforte, Alessandro; Guglielmino, Francesco; Maiolino, Vincenza; Puglisi, Giuseppe; Ursino, Andrea

    2016-04-01

    From December 2, 2015, volcanic activity suddenly occurred on Mt. Etna with very violent fire fountaining at central crater, known also as "Voragine". This activity continued with other intense episodes at the same crater during the three following days and involving also, in turn, all the other three summit craters. This sudden eruption produced a rapid deflation of the volcano and was followed, from December 8, by a seismic swarm, with almost eighty earthquakes during this day, located on the uppermost segment of the Pernicana-Provenzana fault system (PFS). This seismicity was characterized by shallow foci (from few hundred meters until 1.5 km below the sea level) and mainshock with 3.6 magnitude. In order to investigate and measure the dynamics controlling and accompanying the PFS activation, a dataset composed of C-Band Sentinel-1A data has been used for SAR Interferometry (InSAR) analysis. Some interferograms have been generated from ascending and descending orbits in order to analyze both short- and long-term deformation. The availability of GPS data allowed comparing and integrating them with InSAR for ground truth and modeling aims. The surface kinematics and modeling obtained by DInSAR and GPS data and integration have been compared to the distribution of the seismicity and related focal mechanisms in order to define the fault geometry and motion. Moreover, essential constraints have been achieved about the PFS dynamic and its relationship with the intense volcanic activity occurred.

  4. Radar imaging of winter seismic survey activity in the National Petroleum Reserve-Alaska

    USGS Publications Warehouse

    Jones, Benjamin M.; Rykhus, Russ; Lu, Zhiming; Arp, C.D.; Selkowitz, D.J.

    2008-01-01

    During the spring of 2006, Radarsat-1 synthetic aperture radar (SAR) imagery was acquired on a continual basis for the Teshekpuk Lake Special Area (TLSA), in the northeast portion of the National Petroleum Reserve, Alaska (NPR-A) in order to monitor lake ice melting processes. During data processing, it was discovered that the Radarsat-1 imagery detected features associated with winter seismic survey activity. Focused analysis of the image time series revealed various aspects of the exploration process such as the grid profile associated with the seismic line surveys as well as trails and campsites associated with the mobile survey crews. Due to the high temporal resolution of the dataset it was possible to track the progress of activities over a one month period. Spaceborne SAR imagery can provide information on the location of winter seismic activity and could be used as a monitoring tool for land and resource managers as increased petroleum-based activity occurs in the TLSA and NPR-A. ?? 2008 Cambridge University Press.

  5. A Large-N Mixed Sensor Active + Passive Seismic Array near Sweetwater, TX

    NASA Astrophysics Data System (ADS)

    Barklage, M.; Hollis, D.; Gridley, J. M.; Woodward, R.; Spriggs, N.

    2014-12-01

    A collaborative high-density seismic survey using broadband and short period seismic sensors was conducted March 7 - April 30, 2014 near Sweetwater, TX. The objective of the survey was to use a combination of controlled source shot slices and passive seismic recordings recorded by multiple types of sensors with different bandwidths and sensitivities to image the subsurface. The broadband component of the survey consisted of 25 continuously recording seismic stations comprised of 20 Trillium Compact Posthole sensors from Nanometrics and 5 Polar Trillium 120PHQs from the IRIS/PASSCAL Instrument Center (PIC). The broadband stations also utilized 25 Centaur digitizers from Nanometrics as well as 25 polar quick deploy enclosures from the PIC. The broadband array was designed to maximize horizontal traveling seismic energy for surface wave analysis over the primary target area with sufficient offset for imaging objectives at depth. The short period component of the survey consisted of 2639 receiver locations using Zland nodes from NodalSeismic. The nodes are further divided into 3 sub-arrays: 1) outlier array 2) active source array 3) backbone array. The outlier array consisted of 25 continuously recording nodes distributed around the edge of the survey at a distance of ~5 km from the survey boundary, and provided valuable constraints to passive data analysis techniques at the edge of the survey boundary. The active source patch consisted of densely spaced nodes that were designed to record signals from a Vibroseis source truck for active source reflection processing and imaging. The backbone array consisted of 292 nodes that covered the entirety of the survey area to maximize the value of the passive data analysis. By utilizing continuous recording and smartly designed arrays for measuring local and regional earthquakes we can incorporate velocity information derived from passive data analysis into the active source processing workflow to produce a superior subsurface

  6. Fault mirrors in seismically active fault zones: A fossil of small earthquakes at shallow depths

    NASA Astrophysics Data System (ADS)

    Kuo, Li-Wei; Song, Sheng-Rong; Suppe, John; Yeh, En-Chao

    2016-03-01

    Fault mirrors (FMs) are naturally polished and glossy fault slip surfaces that can record seismic deformation at shallow depths. They are important for investigating the processes controlling dynamic fault slip. We characterize FMs in borehole samples from the hanging wall damage zone of the active Hsiaotungshi reverse fault, Taiwan. Here we report the first documented occurrence of the combination of silica gel and melt patches coating FMs, with the silica gel resembling those observed on experimentally formed FMs that were cataclastically generated. In addition, the melt patches, which are unambiguous indicators of coseismic slip, suggest that the natural FMs were produced at seismic rates, presumably resulting from flash heating at asperities on the slip surfaces. Since flash heating is efficient at small slip, we propose that these natural FMs represent fossils of small earthquakes, formed in either coseismic faulting and folding or aftershock deformation in the active Taiwan fold-and-thrust belt.

  7. Grid-Search Location Methods for Ground-Truth Collection from Local and Regional Seismic Networks

    SciTech Connect

    Schultz, C A; Rodi, W; Myers, S C

    2003-07-24

    The objective of this project is to develop improved seismic event location techniques that can be used to generate more and better quality reference events using data from local and regional seismic networks. Their approach is to extend existing methods of multiple-event location with more general models of the errors affecting seismic arrival time data, including picking errors and errors in model-based travel-times (path corrections). Toward this end, they are integrating a grid-search based algorithm for multiple-event location (GMEL) with a new parameterization of travel-time corrections and new kriging method for estimating the correction parameters from observed travel-time residuals. Like several other multiple-event location algorithms, GMEL currently assumes event-independent path corrections and is thus restricted to small event clusters. The new parameterization assumes that travel-time corrections are a function of both the event and station location, and builds in source-receiver reciprocity and correlation between the corrections from proximate paths as constraints. The new kriging method simultaneously interpolates travel-time residuals from multiple stations and events to estimate the correction parameters as functions of position. They are currently developing the algorithmic extensions to GMEL needed to combine the new parameterization and kriging method with the simultaneous location of events. The result will be a multiple-event location method which is applicable to non-clustered, spatially well-distributed events. They are applying the existing components of the new multiple-event location method to a data set of regional and local arrival times from Nevada Test Site (NTS) explosions with known origin parameters. Preliminary results show the feasibility and potential benefits of combining the location and kriging techniques. They also show some preliminary work on generalizing of the error model used in GMEL with the use of mixture

  8. Wave-equation-based travel-time seismic tomography - Part 1: Method

    NASA Astrophysics Data System (ADS)

    Tong, P.; Zhao, D.; Yang, D.; Yang, X.; Chen, J.; Liu, Q.

    2014-11-01

    In this paper, we propose a wave-equation-based travel-time seismic tomography method with a detailed description of its step-by-step process. First, a linear relationship between the travel-time residual Δt = Tobs-Tsyn and the relative velocity perturbation δ c(x)/c(x) connected by a finite-frequency travel-time sensitivity kernel K(x) is theoretically derived using the adjoint method. To accurately calculate the travel-time residual Δt, two automatic arrival-time picking techniques including the envelop energy ratio method and the combined ray and cross-correlation method are then developed to compute the arrival times Tsyn for synthetic seismograms. The arrival times Tobs of observed seismograms are usually determined by manual hand picking in real applications. Travel-time sensitivity kernel K(x) is constructed by convolving a~forward wavefield u(t,x) with an adjoint wavefield q(t,x). The calculations of synthetic seismograms and sensitivity kernels rely on forward modeling. To make it computationally feasible for tomographic problems involving a large number of seismic records, the forward problem is solved in the two-dimensional (2-D) vertical plane passing through the source and the receiver by a high-order central difference method. The final model is parameterized on 3-D regular grid (inversion) nodes with variable spacings, while model values on each 2-D forward modeling node are linearly interpolated by the values at its eight surrounding 3-D inversion grid nodes. Finally, the tomographic inverse problem is formulated as a regularized optimization problem, which can be iteratively solved by either the LSQR solver or a~nonlinear conjugate-gradient method. To provide some insights into future 3-D tomographic inversions, Fréchet kernels for different seismic phases are also demonstrated in this study.

  9. Evidence for activity of the Calabrian arc system and implications for historical seismicity in Eastern Sicily

    NASA Astrophysics Data System (ADS)

    Gallais, F.; Gutscher, M.-A.; Graindorge, D.; Polonia, A.

    2009-04-01

    The Wadati-Benioff zone under Calabria and the Tyrrhenian Sea is located in the centre of the Mediterranean Sea, a region characterized by complex tectonics. The presence of deep earthquakes under the Tyrrhenian Sea to a depth of 500 km, depicting an Ionian slab dipping about 70° towards the NW (Selvaggi and Chiarabba, 95), related with an active volcanic arc (the Aeolian Islands). The Calabrian peninsula is among the most seismically active regions in the Mediterranean area. Several historical seismic events, such as 1169 and 1693 earthquakes, reached MCS intensities of XI and are associated with destructive tsunami (Piatanesi and Tinti, 1998). The source of these two strongest earthquakes has still not been identified with certainty. The 1693 earthquake struck Eastern Sicily (60000 people killed) and generated a 5-10 m high tsunami (Piatanesi and Tinti, 1998). The 1169 earthquake had similar intensities and a comparable isoseismal pattern, suggesting an equivalent source. Because of the tsunami generated in 1693 and because the isoseismals are open to the sea, the source region appears to be offshore. The subduction fault plane would then be a good candidate for the 1693 event. However, a lack of instrumentally recorded thrust earthquakes, characteristic of active subduction zone, suggests that if subduction is active, the fault plane may be locked since the instrumental period. Reported recent GPS motions suggest that the subduction of the Ionian lithosphere beneath the Tyrrhenian basin plays an minor role in controlling the active deformation of the Eurasia-Nubia plate boundary, but may be locally still active in particular in the Calabrian arc (D'Agostino et al., 08). Moreover the offshore accretionary wedge is known to include compressional anticlines and ongoing hydrological activity (mud volcanoes). We present preliminary results from reprocessed 96-channels seismic reflection profiles acquired during the French "Archimede" cruise (1997) crossing the

  10. Seismic activity during the recent eruptive period at Volcán de Colima, México

    NASA Astrophysics Data System (ADS)

    Arambula, R.; Reyes, G.; González, M.; Ramirez, C.; Martínez, A.

    2013-12-01

    Volcán de Colima is an andesitic volcano and is located in the Western part of Mexico, between the states of Jalisco and Colima. It is considered the most active in Mexico based upon its more than 40 effusive and explosive eruptive episodes in the past 500 years. Based upon its last period of activity (2007-2011), the volcano is considered as an open system. On January 3, 2013, a new period of activity started at Volcán of Colima, with the occurrence of Long-Period events (LPs) of low amplitude and proximal Volcano-Tectonic events (VTs) under the crater. An exponential growth of the continuous seismic signal (RMS) of nearest station was observed during the next three days. Finally, a moderately-sized vulcanian explosion occurred with pyroclastic flows emplaced mainly to the west. Then, another three moderate explosions partially destroyed the lava dome formed during the activity of 2007-2011. In late January a new lava dome started to grow inside the fresh crater; the seismic activity associated with this new lava dome was composed of mainly LPs. Some distal VTs have also been observed within 30 kilometers of the volcano. The emission rate has been estimated at less than 0.1 m3/s. During the first days of April, lava flows commenced to the west and southwest of the volcano. Rockfalls and some small pyroclastic flows followed reaching the base of the volcanic edifice. With a program based on Hidden Markov Models (HMMs) more than 100 rockfalls have been recognized automatically per day, also more than 1538 explosions have occurred up to July 30 with a mean of 7 daily. These explosions originated from depths less than 3 km below the crater, determined using the seismic amplitude method. The maximum energy of these explosions was 1.5e+9 Joules for the explosion on January 29. The most energetic explosions also had Very-Long-Period events (VLPs) associated with them with periods of between 30 and 10 sec. The accumulated energy of all the explosions is 3.9e+9 Joules

  11. Ionospheric plasma deterioration in the area of enhanced seismic activity as compared to antipodal sites far from seismicity

    NASA Astrophysics Data System (ADS)

    Gulyaeva, Tamara; Arikan, Feza; Poustovalova, Ljubov; Stanislawska, Iwona

    2016-07-01

    The early magnetogram records from two nearly antipodal sites at Greenwich and Melbourne corresponding to the activity level at the invariant magnetic latitude of 50 deg give a long series of geomagnetic aa indices since 1868. The aa index derived from magnetic perturbation values at only two observatories (as distinct from the planetary ap index) experiences larger extreme values if either input site is well situated to the overhead ionospheric and/or field aligned current systems producing the magnetic storm effects. Analysis of the earthquakes catalogues since 1914 has shown the area of the peak global earthquake occurrence in the Pacific Ocean southwards from the magnetic equator, and, in particular, at Australia. In the present study the ionospheric critical frequency, foF2, is analyzed from the ionosonde measurements at the nearby observatories, Canberra and Slough (Chilton), and Moscow (control site) since 1944 to 2015. The daily-hourly-annual percentage occurrence of positive ionospheric W index (pW+) and negative index (pW-) is determined. It is found that the ionospheric plasma depletion pW- of the instant foF2 as compared to the monthly median is well correlated to the aa index at all three sites but the positive storm signatures show drastic difference at Canberra (no correlation of pW+ with aa index) as compared to two other sites where the high correlation is found of the ionospheric plasma density enhancement with the geomagnetic activity. A possible suppression of the enhanced ionospheric variability over the region of intense seismicity is discussed in the paper. This study is supported by TUBITAK EEEAG 115E915.

  12. A rock-physical modeling method for carbonate reservoirs at seismic scale

    NASA Astrophysics Data System (ADS)

    Li, Jing-Ye; Chen, Xiao-Hong

    2013-03-01

    Strong heterogeneity and complex pore systems of carbonate reservoir rock make its rock physics model building and fluid substitution difficult and complex. However, rock physics models connect reservoir parameters with seismic parameters and fluid substitution is the most effective tool for reservoir prediction and quantitative characterization. On the basis of analyzing complex carbonate reservoir pore structures and heterogeneity at seismic scale, we use the gridding method to divide carbonate rock into homogeneous blocks with independent rock parameters and calculate the elastic moduli of dry rock units step by step using different rock physics models based on pore origin and structural feature. Then, the elastic moduli of rocks saturated with different fluids are obtained using fluid substitution based on different pore connectivity. Based on the calculated elastic moduli of rock units, the Hashin-Shtrikman-Walpole elastic boundary theory is adopted to calculate the carbonate elastic parameters at seismic scale. The calculation and analysis of carbonate models with different combinations of pore types demonstrate the effects of pore type on rock elastic parameters. The simulated result is consistent with our knowledge of real data.

  13. Active-source seismic imaging below Lake Malawi (Nyasa) from the SEGMeNT project

    NASA Astrophysics Data System (ADS)

    Shillington, D. J.; Scholz, C. A.; Gaherty, J. B.; Accardo, N. J.; McCartney, T.; Chindandali, P. R. N.; Kamihanda, G.; Trinhammer, P.; Wood, D. A.; Khalfan, M.; Ebinger, C. J.; Nyblade, A.; Mbogoni, G. J.; Mruma, A. H.; Salima, J.; Ferdinand-Wambura, R.

    2015-12-01

    Little is known about the controls on the initiation and development of magmatism and segmentation in young rift systems. The northern Lake Malawi (Nyasa) rift in the East African Rift System is an early stage rift exhibiting pronounced tectonic segmentation, which is defined in the upper crust by ~100-km-long border faults. Very little volcanism is associated with rifting; the only surface expression of magmatism occurs in an accommodation zone between segments to the north of the lake in the Rungwe Volcanic Province. The SEGMeNT (Study of Extension and maGmatism in Malawi aNd Tanzania) project is a multidisciplinary, multinational study that is acquiring a suite of geophysical, geological and geochemical data to characterize deformation and magmatism in the crust and mantle lithosphere along 2-3 segments of this rift. As a part of the SEGMeNT project, we acquired seismic reflection and refraction data in Lake Malawi (Nyasa) in March-April 2015. Over 2000 km of seismic reflection data were acquired with a 500 to 2580 cu in air gun array from GEUS/Aarhus and a 500- to 1500-m-long seismic streamer from Syracuse University over a grid of lines across and along the northern and central basins. Air gun shots from MCS profiles and 1000 km of additional shooting with large shot intervals were also recorded on 27 short-period and 6 broadband lake bottom seismometers from Scripps Oceanographic Institute as a part of the Ocean Bottom Seismic Instrument Pool (OBSIP) as well as the 55-station onshore seismic array. The OBS were deployed along one long strike line and two dip lines. We will present preliminary data and results from seismic reflection and refraction data acquired in the lake and their implications for crustal deformation within and between rift segments. Seismic reflection data image structures up to ~5-6 km below the lake bottom, including syntectonic sediments, intrabasinal faults and other complex horsts. Some intrabasinal faults in both the northern and

  14. High-resolution seismic array imaging based on an SEM-FK hybrid method

    NASA Astrophysics Data System (ADS)

    Tong, Ping; Chen, Chin-wu; Komatitsch, Dimitri; Basini, Piero; Liu, Qinya

    2014-04-01

    We demonstrate the feasibility of high-resolution seismic array imaging based on teleseismic recordings using full numerical wave simulations. We develop a hybrid method that interfaces a frequency-wavenumber (FK) calculation, which provides analytical solutions to 1-D layered background models with a spectral-element (SEM) numerical solver to calculate synthetic responses of local media to plane-wave incidence.This hybrid method accurately deals with local heterogeneities and discontinuity undulations, and represents an efficient tool for the forward modelling of teleseismic coda (including converted and scattered) waves. We benchmark the accuracy of the SEM-FK hybrid method against FK solutions for 1-D media. We then compute sensitivity kernels for teleseismic coda waves by interacting the forward teleseismic waves with an adjoint wavefield, produced by injecting coda waves as adjoint sources, based on adjoint techniques. These sensitivity kernels provide the basis for mapping variations in subsurface discontinuities, density and velocity structures through non-linear conjugate-gradient methods. We illustrate various synthetic imaging experiments, including discontinuity characterization, volumetric structural inversion for the crust or subduction zones. These tests show that using pre-conditioners based upon the scaled product of sensitivity kernels for different phases, combining finite-frequency traveltime and waveform inversion, and/or adopting hierarchical inversions from long- to short-period waveforms could reduce the non-linearity of the seismic inverse problem and speed up its convergence. The encouraging results of these synthetic examples suggest that inversion of teleseismic coda phases based on the SEM-FK hybrid method and adjoint techniques is a promising tool for structural imaging beneath dense seismic arrays.

  15. OVERVIEW ON BNL ASSESSMENT OF SEISMIC ANALYSIS METHODS FOR DEEPLY EMBEDDED NPP STRUCTURES.

    SciTech Connect

    XU,J.; COSTANTINO, C.; HOFMAYER, C.; GRAVES, H.

    2007-04-01

    A study was performed by Brookhaven National Laboratory (BNL) under the sponsorship of the U. S. Nuclear Regulatory Commission (USNRC), to determine the applicability of established soil-structure interaction analysis methods and computer programs to deeply embedded and/or buried (DEB) nuclear power plant (NPP) structures. This paper provides an overview of the BNL study including a description and discussions of analyses performed to assess relative performance of various SSI analysis methods typically applied to NPP structures, as well as the importance of interface modeling for DEB structures. There are four main elements contained in the BNL study: (1) Review and evaluation of existing seismic design practice, (2) Assessment of simplified vs. detailed methods for SSI in-structure response spectrum analysis of DEB structures, (3) Assessment of methods for computing seismic induced earth pressures on DEB structures, and (4) Development of the criteria for benchmark problems which could be used for validating computer programs for computing seismic responses of DEB NPP structures. The BNL study concluded that the equivalent linear SSI methods, including both simplified and detailed approaches, can be extended to DEB structures and produce acceptable SSI response calculations, provided that the SSI response induced by the ground motion is very much within the linear regime or the non-linear effect is not anticipated to control the SSI response parameters. The BNL study also revealed that the response calculation is sensitive to the modeling assumptions made for the soil/structure interface and application of a particular material model for the soil.

  16. Estimation of seismic attenuation in carbonate rocks using three different methods: Application on VSP data from Abu Dhabi oilfield

    NASA Astrophysics Data System (ADS)

    Bouchaala, F.; Ali, M. Y.; Matsushima, J.

    2016-06-01

    In this study a relationship between the seismic wavelength and the scale of heterogeneity in the propagating medium has been examined. The relationship estimates the size of heterogeneity that significantly affects the wave propagation at a specific frequency, and enables a decrease in the calculation time of wave scattering estimation. The relationship was applied in analyzing synthetic and Vertical Seismic Profiling (VSP) data obtained from an onshore oilfield in the Emirate of Abu Dhabi, United Arab Emirates. Prior to estimation of the attenuation, a robust processing workflow was applied to both synthetic and recorded data to increase the Signal-to-Noise Ratio (SNR). Two conventional methods of spectral ratio and centroid frequency shift methods were applied to estimate the attenuation from the extracted seismic waveforms in addition to a new method based on seismic interferometry. The attenuation profiles derived from the three approaches demonstrated similar variation, however the interferometry method resulted in greater depth resolution, differences in attenuation magnitude. Furthermore, the attenuation profiles revealed significant contribution of scattering on seismic wave attenuation. The results obtained from the seismic interferometry method revealed estimated scattering attenuation ranges from 0 to 0.1 and estimated intrinsic attenuation can reach 0.2. The subsurface of the studied zones is known to be highly porous and permeable, which suggest that the mechanism of the intrinsic attenuation is probably the interactions between pore fluids and solids.

  17. Structure of the deep oceanic lithosphere in the Northwestern Pacific ocean basin derived from active-source seismic data

    NASA Astrophysics Data System (ADS)

    Ohira, A.; Kodaira, S.; Nakamura, Y.; Fujie, G.; Arai, R.; Miura, S.

    2015-12-01

    Many seismological studies have detected the sharp seismic discontinuities in the upper mantle, some of which are interpreted the lithosphere-asthenosphere boundary (LAB). However there are few data at the old Pacific plate, in particular at ocean basin, which is critical information for understanding nature of the oceanic LAB. In 2014 we conducted an active-source refraction/reflection survey along a 1130-km-long line in southeast of the Shatsky Rise. Five ocean bottom seismometers (OBSs) were deployed and recovered by R/V Kairei of JAMSTEC. We used an airgun array with a total volume of 7,800 cubic inches with firing at intervals of 200 m. Multi-channel seismic reflection (MCS) data were also collected with a 444-channel, 6,000-m-long streamer cable. In OBS records the apparent velocity of the refraction waves from the uppermost mantle was high (< 8.6 km/sec), and considered to be caused by preferred orientation of olivine (e.g., Kodaira et al., 2014). Another remarkable feature is wide-angle reflection waves from the deep lithosphere at large (150-500 km) offsets. We applied the traveltime mapping method (Fujie et al., 2006), forward analysis (Zelt and Smith, 1992) and the amplitude modeling (Larsen and Grieger, 1998) to the OBS data. The results show that deep mantle reflectors exist at the depths from 35 to 60 km, and one possible explanation is that these reflectors correspond to patched low velocity zones around the base of the lithosphere. On MCS sections the clear and sharp Moho was imaged only at the southwestern end of the profile, but Moho was ambiguous or even not imaged in the most part of the profile. Since our seismic line covers the oceanic lithosphere with different ages that correspond to different stages of the Shatsky activity, the Moho appearance may reflect the variation of the Shatsky activity.

  18. Seismic time-frequency analysis of the recent 2015 eruptive activity of Volcán de Colima, Mexico

    NASA Astrophysics Data System (ADS)

    Vargas-Bracamontes, D. M.; Nava Pichardo, F. A.; Reyes Dávila, G. A.; Arámbula-Mendoza, R.; Martínez Fierros, A.; Ramírez Vázquez, A.; González Amezcua, M.

    2015-12-01

    Volcán de Colima is an andesitic stratovolcano located in western Mexico. It is considered the most active volcano in Mexico, with activity characterized mainly by intermittent effusive and explosive episodes. On July 10th-12th 2015, Volcán de Colima underwent its most intense eruptive phase since its Plinian eruption in 1913. A partial collapse of the dome and of the crater wall generated several pyroclastic flows, the largest of which reached almost 10 km to the south of the volcano. Lava flows along with incandescent rockfalls descended through various flanks of the volcanic edifice. Ashfall affected people up to 40 km from the volcano's summit. Inhabitants from the small villages closest to the volcano were evacuated and authorities sealed off a 12 km area. We present an overview of the seismic activity that preceded and accompanied this eruptive phase, with data from the closest broadband and short period seismic stations of the Volcán de Colima monitoring network. We focus on the search of temporal information within the spectral content of the seismic signals. We first employ common time-frequency representations such as Fourier and wavelet transforms, but we also apply more recent techniques proposed for the analysis of non-stationary signals, such as empirical mode decomposition and the synchrosqueezing transform. We present and discuss the performances of these various methods characterizing and quantifying spectral changes which could be used to forecast future eruptive events and to evaluate the course of volcanic processes during ongoing eruptions.

  19. High-resolution seismic monitoring of rockslide activity in the Illgraben, Switzerland

    NASA Astrophysics Data System (ADS)

    Burtin, Arnaud; Hovius, Niels; Dietze, Michael; McArdell, Brian

    2014-05-01

    Rockfalls and rockslides are important geomorphic processes in landscape dynamics. They contribute to the evolution of slopes and supply rock materials to channels, enabling fluvial incision. Hillslope processes are also a natural hazard that we need to quantify and, if possible, predict. For these reasons, it is necessary to determine the triggering conditions and mechanisms involved in rockfalls. Rainfall is a well-known contributor since water, through soil moisture or pore pressure, may lead to the inception and propagation of cracks and can induce slope failure. Water can also affect slope stability through effects of climatic conditions such as the fluctuations of temperature around the freezing point. During the winter of 2012, we have recorded with a seismic array of 8 instruments substantial rockslide activity that affected a gully in the Illgraben catchment in the Swiss Alps. Three stations were positioned directly around the gully with a nearest distance of 400 m. The period of intense activity did not start during a rainstorm as it is common in summer but during a period of oscillation of temperatures around the freezing point. The activity did not occur in a single event but lasted about a week with a decay in time of the event frequency. Many individual events had two distinct seismic signals, with first, a short duration phase of about 10 s at frequencies below 5 Hz that we interpret as a slope failure signature, followed by a second long duration signal of > 60 s at frequencies above 10 Hz that we attribute to the propagation of rock debris down the slope. Thanks to the array of seismic sensors, we can study the fine details of this rockslide sequence by locating the different events, determining their distribution in time, and systematic quantification of seismic metrics (energy, duration, intensity...). These observations are compared to independent meteorological constrains and laser scan data to obtain an estimate of the volume mobilized by the

  20. Seismic microzonation and velocity models of El Ejido area (SE Spain) from the diffuse-field H/V method

    NASA Astrophysics Data System (ADS)

    García-Jerez, Antonio; Seivane, Helena; Navarro, Manuel; Piña-Flores, José; Luzón, Francisco; Vidal, Francisco; Posadas, Antonio M.; Aranda, Carolina

    2016-04-01

    El Ejido town is located in the Campo de Dalías coastal plain (Almería province, SE Spain), emplaced in one of the most seismically active regions of Spain. The municipality has 84000 inhabitants and presented a high growth rate during the last twenty years. The most recent intense seismic activity occurred close to this town was in 1993 and 1994, with events of Mb = 4.9 and Mb = 5.0, respectively. To provide a basis for site-specific hazard analysis, we first carried out a seismic microzonation of this town in terms of predominant periods and geotechnical properties. The predominant periods map was obtained from ambient noise observations on a grid of 250 x 250 m in the main urban area, and sparser measurements on the outskirts. These broad-band records, of about 20 minutes long each, were analyzed by using the horizontal-to-vertical spectral ratio technique (H/V). Dispersion curves obtained from two array measurements of ambient noise and borehole data provided additional geophysical information. All the surveyed points in the town were found to have relatively long predominant periods ranging from 0.8 to 2.3 s and growing towards the SE. Secondary high-frequency (> 2Hz) peaks were found at about the 10% of the points only. On the other hand, Vs30 values of 550 - 650 m/s were estimated from the array records, corresponding to cemented sediments and medium-hard rocks. The local S-wave velocity structure has been inverted from the H/V curves for a subset of the measurement sites. We used an innovative full-wavefield method based on the diffuse-wavefield approximation (Sánchez-Sesma et al., 2011) combined with the simulated annealing algorithm. Shallow seismic velocities and deep boreholes data were used as constraints. The results show that the low-frequency resonances are related with the impedance contrast between several hundred meters of medium-hard sedimentary rocks (marls and calcarenites) with the stiffer basement of the basin, which dips to the SE. These

  1. Exploring a long-lasting volcanic eruption by means of in-soil radon measurements and seismic activity

    NASA Astrophysics Data System (ADS)

    Falsaperla, Susanna; Neri, Marco; Di Grazia, Giuseppe; Langer, Horst; Spampinato, Salvatore

    2016-04-01

    We analyze in-soil radon (Rn) emission and ambient parameters (barometric pressure and air temperature measurements) along with seismic activity during the longest flank eruption of this century at Mt. Etna, Italy. This eruption occurred between 14 May 2008 and 6 July 2009, from a N120-140°E eruptive fissure extending between 3050 and 2620 m above sea level. It was heralded by a short-lived (~5 hours) episode of lava fountaining three days before a dike-forming intrusion fed a lava emission, which affected the summit area of the volcano over ~15 months. The peculiar position of the station for the Rn measurement, which was at an altitude of 2950 m above sea level and near (~1 km) the summit active craters, offered us the uncommon chance: i) to explore the temporal development of the gas emission close (<2 km) to the 2008-2009 eruptive vents in the long term, and ii) to analyze the relationship between in-soil Rn fluxes and seismic signals (in particular, local earthquakes and volcanic tremor) during the uninterrupted lava emission. This approach reveals important details about the recharging phases characterizing the 2008-2009 eruption, which are not visible with other methods of investigation. Our study benefitted from the application of methods of pattern classification developed in the framework of the European MEDiterrranean Supersite Volcanoes (MED­SUV) project.

  2. Study of time dynamics of seismicity for the Mexican subduction zone by means of the visibility graph method.

    NASA Astrophysics Data System (ADS)

    Ramírez-Rojas, Alejandro; Telesca, Luciano; Lovallo, Michele; Flores, Leticia

    2015-04-01

    By using the method of the visibility graph (VG), five magnitude time series extracted from the seismic catalog of the Mexican subduction zone were investigated. The five seismic sequences represent the seismicity which occurred between 2005 and 2012 in five seismic areas: Guerrero, Chiapas, Oaxaca, Jalisco and Michoacan. Among the five seismic sequences, the Jalisco sequence shows VG properties significantly different from those shown by the other four. Such a difference could be inherent in the different tectonic settings of Jalisco with respect to those characterizing the other four areas. The VG properties of the seismic sequences have been put in relationship with the more typical seismological characteristics (b-value and a-value of the Gutenberg-Richter law). The present study was supported by the Bilateral Project Italy-Mexico "Experimental Stick-slip models of tectonic faults: innovative statistical approaches applied to synthetic seismic sequences", jointly funded by MAECI (Italy) and AMEXCID (Mexico) in the framework of the Bilateral Agreement for Scientific and Technological Cooperation PE 2014-2016

  3. Ion density variation during seismic activity as measured by SROSS-C2 satellite

    NASA Astrophysics Data System (ADS)

    Bardhan, Ananna; Sharma, Dinesh Kumar; Kumar, Sarvesh

    ABSTRACT Ion density (O+ and H+) as a precursory parameter to seismic activity has been analysed from year 1995-1998, using RPA payload aboard SROSS-C2 satellite at an average altitude range of ~ 500 km over the Indian region. The details of seismic events during this period are downloaded from United State Geological Survey (USGS) website. Total of six events from the period of 1995-1998 are analyzed which are free from other perturbing phenomena like solar flares and thunderstorms/ lighting. It has been observed that there is considerable enhancement in average values of heavier ion - O+ density and decrease in lighter ion - H+ ion density during seismic affected time over the normal days. The increase in O+ ion density varies from 1.4 to 8.1 times and decrease in H+ ion density varies from 1.4 to 19.9 times compared to normal day's ion densities respectively. VLF emissions generated due to anomalous electric field during seimogenic activity could plausible candidature of change in ion concentration values during these events.

  4. Peculiarities of ULF electromagnetic disturbances before strong earthquakes in seismic active zone of Kamchatka peninsula

    NASA Astrophysics Data System (ADS)

    Kopytenko, Y. A.; Ismagilov, V. S.; Schekotov, A.; Molchanov, O.; Chebrov, V.; Raspopov, O. M.

    2006-12-01

    Regular observations of ULF electromagnetic disturbances and acoustic emissions at st. Karymshino in seismic active zone of Kamchatka peninsula were carried out during 2001-2003 years. Five seismic active periods with strong earthquakes (M>5) were displayed during this period. These EQs occurred at the Pacific at 20-60 km depth at 100-140 km distances to the East from the st. Karymshino. Analysis of normalized dynamic power spectra of data of high-sensitive (0.2 pT/sqrt(Hz)) three-component induction magnetometer achieved a significant disorder of daily variation and increasing of the magnetic disturbance intensities (from 0.2 to ~1 pT) in the whole investigated frequency range (0.2-5 Hz). The anomaly intensity increasing was observed during the 12-18 hours before main seismic shocks. Maximum of the increasing occurred during 4-6 hours before the EQs. An increasing of acoustic emissions (F=30 Hz) was observed during the same period. A sharp decreasing of the magnetic disturbance intensities was observed 2-4 hours before the EQs. We suppose that physical processes in a hearth of forthcoming EQ lead to an irreversible avalanche-like formation of cracks and stimulation of the acoustic and ULF electromagnetic disturbances.

  5. Active deformation and seismicity in the Southern Alps (Italy): The Montello hill as a case study

    NASA Astrophysics Data System (ADS)

    Danesi, Stefania; Pondrelli, Silvia; Salimbeni, Simone; Cavaliere, Adriano; Serpelloni, Enrico; Danecek, Peter; Lovati, Sara; Massa, Marco

    2015-06-01

    The Montello anticline is a morphotectonic feature of the east pede-mountain of the South Alpine Chain in northern Italy, which lies ca. 40 km northwest of Venice, Italy. The purpose of this study is to characterize the present-day crustal deformation and seismotectonics of the Montello area through multi-parametric geophysical observations. We used new data obtained from the installation of a temporary network of 12 seismic stations and 6 GPS sites. The GPS observations indicate that there is ~ 1 mm/yr shortening across the Montello thrust. Sites located north of the Montello thrust front deviate from the ~ NNW-ward Adria-Eurasia convergence direction, as they are constrained by a relative rotation pole in northwestern Italy that has a NNE-ward motion trend. Over 18 months, seismographic recordings allowed us to locate 142 local seismic events with Ml 0.5-3.5 with good reliability (rms < 0.5). After cross-correlation analysis, we classified 42 of these events into six clusters, with cross-correlation thresholds > 0.80. The source focal solutions indicate that: (i) there is thrusting seismic activity on the basal, sub-horizontal, portion of the Montello structure; and (ii) strike-slip source kinematics prevail on the western edge of the Montello hill. Our observations on the source mechanisms and the measured crustal deformation confirm that the Montello thrust is tectonically active.

  6. Effect of cohesion and fill amplification on seismic stability of municipal solid waste landfills using limit equilibrium method.

    PubMed

    Savoikar, Purnanand; Choudhury, Deepankar

    2010-12-01

    Municipal solid waste (MSW) landfills in seismic zones are subjected to the seismic forces both in the horizontal and vertical directions. The stability of landfills against these seismic forces was evaluated by computing the factor of safety of landfills with different modes of failure among which failures of landfills due to translation are very common. Conventionally, the seismic stability of landfill is evaluated by using pseudo-static limit equilibrium method. In the present study, seismic stability of landfills is evaluated by both the conventional pseudo-static and modern pseudo-dynamic method. The pseudo-dynamic method is superior as it takes into account the effect of duration and frequency of earthquake motion and corresponding body waves in addition to the variation of earthquake accelerations along depth and time. In the present study, the effects of cohesion and fill amplification on seismic stability of landfill are also taken into account. It was noticed that, neglecting cohesion of fill material as well as liner material, results in a lower factor of safety and, hence, a very conservative/uneconomic design. Also, fill amplification is found to reduce the factor of safety values computed only by using the pseudo-dynamic method, showing its advantage. Generalized expressions are developed for factor of safety and yield acceleration against translational failure, which can be used for evaluating the seismic stability of MSW landfills. Comparisons of results under static condition with existing, similar methodology show a very good agreement. However, the present study seems to provide unique results for the seismic case. PMID:19837709

  7. Shear wave velocity profile estimation by integrated analysis of active and passive seismic data from small aperture arrays

    NASA Astrophysics Data System (ADS)

    Lontsi, A. M.; Ohrnberger, M.; Krüger, F.

    2016-07-01

    We present an integrated approach for deriving the 1D shear wave velocity (Vs) information at few tens to hundreds of meters down to the first strong impedance contrast in typical sedimentary environments. We use multiple small aperture seismic arrays in 1D and 2D configuration to record active and passive seismic surface wave data at two selected geotechnical sites in Germany (Horstwalde & Löbnitz). Standard methods for data processing include the Multichannel Analysis of Surface Waves (MASW) method that exploits the high frequency content in the active data and the sliding window frequency-wavenumber (f-k) as well as the spatial autocorrelation (SPAC) methods that exploit the low frequency content in passive seismic data. Applied individually, each of the passive methods might be influenced by any source directivity in the noise wavefield. The advantages of active shot data (known source location) and passive microtremor (low frequency content) recording may be combined using a correlation based approach applied to the passive data in the so called Interferometric Multichannel Analysis of Surface Waves (IMASW). In this study, we apply those methods to jointly determine and interpret the dispersion characteristics of surface waves recorded at Horstwalde and Löbnitz. The reliability of the dispersion curves is controlled by applying strict limits on the interpretable range of wavelengths in the analysis and further avoiding potentially biased phase velocity estimates from the passive f-k method by comparing to those derived from the SPatial AutoCorrelation method (SPAC). From our investigation at these two sites, the joint analysis as proposed allows mode extraction in a wide frequency range (~ 0.6-35 Hz at Horstwalde and ~ 1.5-25 Hz at Löbnitz) and consequently improves the Vs profile inversion. To obtain the shear wave velocity profiles, we make use of a global inversion approach based on the neighborhood algorithm to invert the interpreted branches of the

  8. A Hamiltonian Particle Method with a Staggered Particle Technique for Simulating Seismic Wave Propagation

    NASA Astrophysics Data System (ADS)

    Takekawa, Junichi; Mikada, Hitoshi; Goto, Tada-nori

    2014-08-01

    We present a Hamiltonian particle method (HPM) with a staggered particle technique for simulating seismic wave propagation. In the conventional HPM, physical variables, such as particle displacement and stress, are defined at the center, i.e., at the same position, of each particle. As most seismic simulations using finite difference methods (FDM) are practiced with staggered grid techniques, we know the staggered alignment of space variables could improve the numerical accuracy. In the present study, we hypothesized that staggered technique could improve the numerical accuracy also in the HPM and tested the hypothesis. First, we conducted a plane wave analysis for the HPM with the staggered particles in order to verify the validity of our strategy. The comparison of grid dispersion in our strategy with that in the conventional one suggests that the accuracy would be improved dramatically by use of the staggered technique. It is also observed that the dispersion of waves is dependent on the propagation direction due to the difference in the average spacing of the neighboring two particles for the same parameters, as is usually observed in FDM with a rotated staggered grid. Next, we compared the results from the conventional Lamb's problem using our HPM with those from an analytical approach in order to demonstrate the effectiveness of the staggered particle technique. Our results showed better agreement with the analytical solutions than those from HPM without the staggered particles. We conclude that the staggered particle technique would be a method to improve the calculation accuracy in the simulation of seismic wave propagation.

  9. Deep seismic soundings on the 1-AP profile in the Barents Sea: Methods and results

    NASA Astrophysics Data System (ADS)

    Sakoulina, T. S.; Kashubin, S. N.; Pavlenkova, G. A.

    2016-07-01

    Profile 1-AP with a length of 1300 km intersects the Barents Sea from The Kola Peninsula to Franz Josef Land. The combined Common Depth Point (CDP) and Deep Seismic Sounding (DSS) seismic studies were carried out on this profile. The DSS measurements were conducted with the standalone bottom seismic stations with an interval of 5-20 km between them. The stations recorded the signals generated by the large air guns with a step of 250 m. Based on these data, the detailed P-velocity section of the Earth's crust and uppermost mantle have been constructed for the entire profile and the S-velocity section for its southern part. The use of a variety of methods for constructing the velocity sections enabled us to assess the capabilities of each method from the standpoint of the highest reliability and informativity of the models. The ray tracing method yielded the best results. The 1-PR profile crosses two large basins—the South Barents and North Barents ones, with the thickness of the sediments increasing from 8 to 10 km in the south to 12-15 km in the north. The Earth's crust pertains to the continental type along the entire profile. Its thickness averages 32 to 36 km and only increases to 43 km at the boundary between the two basins. The distinct change in the wave field at this boundary suggests the presence of a large deep fault in this zone. The high-velocity blocks are revealed in the crust of the South Barents basin, whereas the North Barents crust is characterized by relatively low velocities.

  10. A method to establish seismic noise baselines for automated station assessment

    USGS Publications Warehouse

    McNamara, D.E.; Hutt, C.R.; Gee, L.S.; Benz, H.M.; Buland, R.P.

    2009-01-01

    We present a method for quantifying station noise baselines and characterizing the spectral shape of out-of-nominal noise sources. Our intent is to automate this method in order to ensure that only the highest-quality data are used in rapid earthquake products at NEIC. In addition, the station noise baselines provide a valuable tool to support the quality control of GSN and ANSS backbone data and metadata. The procedures addressed here are currently in development at the NEIC, and work is underway to understand how quickly changes from nominal can be observed and used within the NEIC processing framework. The spectral methods and software used to compute station baselines and described herein (PQLX) can be useful to both permanent and portable seismic stations operators. Applications include: general seismic station and data quality control (QC), evaluation of instrument responses, assessment of near real-time communication system performance, characterization of site cultural noise conditions, and evaluation of sensor vault design, as well as assessment of gross network capabilities (McNamara et al. 2005). Future PQLX development plans include incorporating station baselines for automated QC methods and automating station status report generation and notification based on user-defined QC parameters. The PQLX software is available through the USGS (http://earthquake. usgs.gov/research/software/pqlx.php) and IRIS (http://www.iris.edu/software/ pqlx/).

  11. Active and passive seismic studies of geothermal resources in New Mexico and investigations of earthquake hazards to geothermal development

    SciTech Connect

    Morgan, P.; Daggett, P.H.

    1980-01-01

    Seismic data were collected in southwestern New Mexico to investigate the sources of the geothermal anomalies and to investigate the potential earthquake hazards of geothermal development. No major crustal structure anomalies have been located related to known geothermal resources, and no areas of continual seismicity have been identified, which is interpreted to indicate a lack of active, or recently active crustal intrusions in southwestern New Mexico. Without a magnetic heat source, the geothermal potential of the known anomalies is probably limited to intermediate and low temperature applications (<180/sup 0/C). The lack of continual seismicity indicates low seismic hazard in the area directly related to geothermal development, although the historic and geologically recent tectonic activity should be taken into consideration during any development in the area. A model of forced groundwater convection is presented to explain the geothermal anomalies in southwestern New Mexico, which is consistent with all available geological and geophysical data from the area.

  12. Applicability of Equivalent Static Method to seismic response of piping and other components

    SciTech Connect

    Hsieh, B.J.

    1993-02-01

    The Equivalent Static Method (ESM) is a simple and cost effective approach in the design of systems and components subjected to seismic loads. However, its applicability is restricted to systems which can be represented by a simple model.'' In this paper the restriction to a simple model is examined using the example of a propped cantilever, for which some codes or standards explicitly state that ESM is not applicable. By comparing ESM results for the propped cantilever with those for a regular (un-propped) cantilever, it is found that ESM can conditionally be applied to the propped cantilever configuration.

  13. Applicability of Equivalent Static Method to seismic response of piping and other components

    SciTech Connect

    Hsieh, B.J.

    1993-02-01

    The Equivalent Static Method (ESM) is a simple and cost effective approach in the design of systems and components subjected to seismic loads. However, its applicability is restricted to systems which can be represented by a ``simple model.`` In this paper the restriction to a simple model is examined using the example of a propped cantilever, for which some codes or standards explicitly state that ESM is not applicable. By comparing ESM results for the propped cantilever with those for a regular (un-propped) cantilever, it is found that ESM can conditionally be applied to the propped cantilever configuration.

  14. Seismic monitoring of Poland - temporary seismic project - first results

    NASA Astrophysics Data System (ADS)

    Trojanowski, J.; Plesiewicz, B.; Wiszniowski, J.; Suchcicki, J.; Tokarz, A.

    2012-04-01

    The aim of the project is to develop national database of seismic activity for seismic hazard assessment. Poland is known as a region of very low seismicity, however some earthquakes occur from time to time. The historical catalogue consists of less than one hundred earthquakes in the time span of almost one thousand years. Due to such a low occurrence rate, the study has been focussing on events at magnitudes lower than 2 which are more likely to occur during a few-year-long project. There are 24 mobile seismic stations involved in the project which are deployed in temporary locations close to humans neighbourhood. It causes a high level of noise and disturbances in recorded seismic signal. Moreover, the majority of Polish territory is covered by a thick sediments. It causes the problem of a reliable detection method for small seismic events in noisy data. The majority of algorithms is based on the concept of STA/LTA ratio and is designed for strong teleseismic events registered on many stations. Unfortunately they fail on the problem of weak events in the signal with noise and disturbances. It has been decided to apply Real Time Recurrent Neural Network (RTRN) to detect small natural seismic events from Poland. This method is able to assess relations of seismic signal in frequency domains as well as in time of seismic phases. The RTRN was taught by wide range of seismic signals - regional, teleseismic as well as blasts. The method is routinely used to analyse data from the project. In the firs two years of the project the seismic network was set in southern Poland, where relatively large seismicity in known. Since the mid-2010 the stations have been working in several regions of central and northern Poland where some minor historical earthquakes occurred. Over one hundred seismic events in magnitude range from 0.5 to 2.3 confirms the activity of Podhale region (Tatra Mountains, Carpathians), where an earthquake of magnitude 4.3 occurred in 2004. Initially three

  15. Application of k-means and Gaussian mixture model for classification of seismic activities in Istanbul

    NASA Astrophysics Data System (ADS)

    Kuyuk, H. S.; Yildirim, E.; Dogan, E.; Horasan, G.

    2012-08-01

    Two unsupervised pattern recognition algorithms, k-means, and Gaussian mixture model (GMM) analyses have been applied to classify seismic events in the vicinity of Istanbul. Earthquakes, which are occurring at different seismicity rates and extensions of the Thrace-Eskisehir Fault Zone and the North Anatolian Fault (NAF), Turkey, are being contaminated by quarries operated around Istanbul. We have used two time variant parameters, complexity, the ratio of integrated powers of the velocity seismogram, and S/P amplitude ratio as classifiers by using waveforms of 179 events (1.8 < M < 3.0). We have compared two algorithms with classical multivariate linear/quadratic discriminant analyses. The total accuracies of the models for GMM, k-means, linear discriminant function (LDF), and quadratic discriminant function (QDF) are 96.1%, 95.0%, 96.1%, 96.6%, respectively. The performances of models are discussed for earthquakes and quarry blasts separately. All methods clustered the seismic events acceptably where QDF slightly gave better improvements compared to others. We have found that unsupervised clustering algorithms, for which no a-prior target information is available, display a similar discriminatory power as supervised methods of discriminant analysis.

  16. Causality between expansion of seismic cloud and maximum magnitude of induced seismicity in geothermal field

    NASA Astrophysics Data System (ADS)

    Mukuhira, Yusuke; Asanuma, Hiroshi; Ito, Takatoshi; Häring, Markus

    2016-04-01

    is seismic moment density (Mo/m3) and V stim is stimulated rock volume (m3). Mopossible = D ∗ V stim(1) We applied this conceptual model to real microseismic data set from Basel EGS project where several induced seismicity with large magnitude occurred and brought constructive damage. Using the hypocenter location determined by the researcher of Tohoku Univ., Japan and moment magnitude estimated from Geothermal Explorers Ltd., operating company, we were able to estimate reasonable seismic moment density meaning that one representative parameter exists and can characterize seismic activity at Basel at each time step. With stimulated rock volume which was also inferred from microseismic information, we estimated possible seismic moment and assess the difference with observed value. Possible seismic moment significantly increased after shut-in when the seismic cloud (stimulated zone) mostly progressed, resulting that the difference with the observed cumulative seismic moment automatically became larger. This suggests that there is moderate seismic moment which will be released in near future. In next few hours, the largest event actually occurred. Therefore, our proposed model was successfully able to forecast occurrence of the large events. Furthermore, best forecast of maximum magnitude was Mw 3 level and the largest event was Mw 3.41, showing reasonable performance in terms of quantitative forecast in magnitude. Our attempt to assess the seismic activity from microseismic information was successful and it also suggested magnitude release can be correlate with the expansion of seismic cloud as the definition of possible seismic moment model indicates. This relationship has been observed in microseismic observational study and several previous study also suggested their correlation with stress released rock volume. Our model showed harmonic results with these studies and provide practical method having clear physical meaning to assess the seismic activity in real

  17. Earth's magnetic field anomalies that precede the M6+ global seismic activity

    NASA Astrophysics Data System (ADS)

    Cataldi, Gabriele; Cataldi, Daniele; Straser, Valentino

    2014-05-01

    In this work has been analyzed the Earth's magnetic field variations and the M6+ global seismic activity to verify if M6+ earthquakes are preceded by a change of the Earth's magnetic field. The data of Earth's magnetic field used to conduct the study of correlation are provided by the induction magnetometer of Radio Emissions Project's station (Lat: 41°41'4.27"N, Long: 12°38'33,60"E, Albano Laziale, Rome, Italy), equipped with a ELF receiver prototype (with a vertically aligned coil antenna) capable to detect the variations of the intensity of the Earth's magnetic field on Z magnetic component. The M6+ global seismic activity data are provided in real-time by USGS, INGV and CSEM. The sample of data used to conduct the study refers to the period between 1 January 2012 and 31 December 2012. The Earth's magnetic field variations data set has been marked with the times (time markers) of M6+ earthquakes occurred on a global scale and has been verified the existence of disturbances of the Earth's geomagnetic field in the time interval that preceded the M6+ global seismic activity. The correlation study showed that all M6+ earthquakes recorded on 2012 were preceded by an increase of the Earth's magnetic field, detected in the Z magnetic component. The authors measured the time lag elapsed between the maximum increment of the Earth's magnetic field recorded before an earthquake M6+ and the date and time at which this occurred, and has been verified that the minimum time lag recorded between the Earth's magnetic field increase and the earthquake M6+ has been 1 minute (9 October 2012, Balleny Islands, M6,4); while, the maximum time lag recorded has been 3600 minutes (26 June 2012, China, M6,3). The average time lag has been 629.47 minutes. In addition, the average time lag is deflected in relation to the magnitude increase. Key words: Seismic Geomagnetic Precursor (SGP), Interplanetary Seismic Precursor (ISP), Earth's magnetic field variations, earthquakes, prevision.

  18. The role of the Montello hill in the seismicity and active deformation of Southern Alps

    NASA Astrophysics Data System (ADS)

    Pondrelli, S.; Serpelloni, E.; Danesi, S.; Lovati, S.; Massa, M.; Mastrolembo Ventura, B.; Danecek, P.; Cavaliere, A.; Salimbeni, S.

    2013-12-01

    The most remarkable geomorphological feature of the eastern Southern Alps (northern Italy) is the Montello anticline, a ~15km long SSW-NNE elongated hill, sited ~40km north of Venice, and offset of ~15 km to the south from the main pede-Alpine thrust front. It has been generated by the uplift and the deformation produced by a S-verging blind thrust, constrained by morphotectonic analyses of uplifted river terraces and sub-surface data. Despite it is presently considered as one of the main S-verging seismogenic segments of the tectonically active Southern Alps thrust front, its real seismogenic potential is still matter of debate. Although the area has been hit in 1695 by a Mw 6.5 earthquake, the Montello is currently characterized by slower seismicity activity than its confining segments and geodetic deformation rates are at the mm/yr level. In order to study the present day crustal deformation at the fault-scale and to improve the detection of background seismicity associated to the 'seismically silent' Montello thrust and to understand its interseismic behavior, we have installed a temporary multi-parametric geophysical network, which integrates space geodetic (GPS) and seismological observations during the 2010-2011 time-interval, running semi-continuous GPS experiments from 2009 to 2013. We recorded 142 local events (compared to the 43 events located by the Italian Seismic Network), located with good reliability (rms < 0.5) with Ml between 1.5 and 3.5. The available continuous and semi-continuous GPS data show that ~2 mm/yr of N-S convergence are accommodated across this sector of the Southern Alps, but the deformation signal appears more complex than what expected by a single thrust fault. GPS, although preliminary and not sampling optimally possible lateral variations of the strain-rate field, show a remarkable change of the kinematics across the external Montello thrust front. The GPS and seismological data collected during the experiment suggest that the

  19. Geomorphology, active duplexing, and earthquakes within the Central Himalayan seismic gap

    NASA Astrophysics Data System (ADS)

    Morell, K. D.; Sandiford, M.; Rajendran, C. C.; Rajendran, K.

    2013-12-01

    The ~500 km long 'Central Himalayan seismic gap' of northwest India, is the largest section of the Himalaya that has not experienced a very large earthquake (Mw > 7.0) in the past 200-500 years. The slip deficit associated with this seismic quiescence has led many to suggest that the region is overdue for a great earthquake (Mw >8), an event which could be potentially devastating given the region's high population (>10 million). Despite the recognition that the region is under considerable seismic risk, the geometry of active fault structures that could potentially fail during large earthquakes remains poorly defined. This has arisen, to a certain extent, because moderate earthquakes, such as the Mw 6.3 1999 event near the city of Chamoli and the Mw 7.0 1991 earthquake near Uttarkashi (responsible for ~1000 deaths), have not produced obvious surface ruptures and do not appear to coincide with surficially mapped faults. We present new geomorphic and river longitudinal profile data that define a prominent ~400 km long distinctive geomorphic transition at the base of the high Himalaya in the seismic gap, defined as a sharp dividing line north of which there are significant increases in normalized river steepness (ksn), hillslope angles, and local relief. We interpret the morphologic changes across the geomorphic boundary to be produced due to a northward increase in rock uplift rate, given that the boundary cross-cuts mapped structures and lithologic contacts, yet coincides exactly with: 1) the axial trace of the geophysically-imaged ramp-flat transition in the Main Himalayan Thrust, 2) significant northward increases in instrumentally-recorded seismicity, and 3) an order of magnitude change in published Ar-Ar bedrock cooling ages. The available datasets suggest that such an increase in rock uplift rate is best explained by a ~400 km long by ~50 km wide active duplex along the Main Himalayan Thrust ramp, with the leading edge of the duplex giving rise to the

  20. Estimating primaries from passive seismic data

    NASA Astrophysics Data System (ADS)

    Cheng, Hao; Wang, De-Li; Feng, Fei; Zhu, Heng

    2015-12-01

    Passive seismic sources can generally be divided into transient sources and noise sources. Noise sources are particularly the continuous, random small bursts, like background noise. The virtual-shot gathers obtained by the traditional cross-correlation algorithm from passive seismic data not only contain primaries, but also include surface-related multiples. Through estimating primaries by sparse inversion, we can directly obtain primaries from passive seismic data activated by transient sources, which are free of surface-related multiples. The problem of estimating primaries from passive seismic data activated by noise sources has not been discussed to date. First, by introducing the optimisation problem via the L1-norm constraint, this paper makes the traditional method of estimating primaries by sparse inversion from passive seismic data activated by transient sources improved, which overcomes the time-window problem. During the sparse inversion, the sparsifying transform, S = C2⊗W, is introduced. In the sparsifying-transform domain, the transformed data is more sparse, so the solution becomes more accurate. Second, this paper proposes estimating primaries from passive seismic data activated by noise sources. In the case of the sparse assumption not holding, we use the least-squares method based on the principle of minimum energy to estimate primaries from passive seismic data using the noise sources. Finally, we compare the primaries estimated from passive seismic data using transient sources and noise sources and analyse the characteristics of the estimated primaries obtained from two passive seismic data.

  1. Improved Simplified Methods for Effective Seismic Analysis and Design of Isolated and Damped Bridges in Western and Eastern North America

    NASA Astrophysics Data System (ADS)

    Koval, Viacheslav

    The seismic design provisions of the CSA-S6 Canadian Highway Bridge Design Code and the AASHTO LRFD Seismic Bridge Design Specifications have been developed primarily based on historical earthquake events that have occurred along the west coast of North America. For the design of seismic isolation systems, these codes include simplified analysis and design methods. The appropriateness and range of application of these methods are investigated through extensive parametric nonlinear time history analyses in this thesis. It was found that there is a need to adjust existing design guidelines to better capture the expected nonlinear response of isolated bridges. For isolated bridges located in eastern North America, new damping coefficients are proposed. The applicability limits of the code-based simplified methods have been redefined to ensure that the modified method will lead to conservative results and that a wider range of seismically isolated bridges can be covered by this method. The possibility of further improving current simplified code methods was also examined. By transforming the quantity of allocated energy into a displacement contribution, an idealized analytical solution is proposed as a new simplified design method. This method realistically reflects the effects of ground-motion and system design parameters, including the effects of a drifted oscillation center. The proposed method is therefore more appropriate than current existing simplified methods and can be applicable to isolation systems exhibiting a wider range of properties. A multi-level-hazard performance matrix has been adopted by different seismic provisions worldwide and will be incorporated into the new edition of the Canadian CSA-S6-14 Bridge Design code. However, the combined effect and optimal use of isolation and supplemental damping devices in bridges have not been fully exploited yet to achieve enhanced performance under different levels of seismic hazard. A novel Dual-Level Seismic

  2. Recent high-resolution seismic reflection studies of active faults in the Puget Lowland

    NASA Astrophysics Data System (ADS)

    Liberty, L. M.; Pratt, T. L.

    2005-12-01

    In the past four years, new high-resolution seismic surveys have filled in key gaps in our understanding of active structures beneath the Puget Lowland, western Washington State. Although extensive regional and high-resolution marine seismic surveys have been fundamental to understanding the tectonic framework of the area, these marine profiles lack coverage on land and in shallow or restricted waterways. The recent high-resolution seismic surveys have targeted key structures beneath water bodies that large ships cannot navigate, and beneath city streets underlain by late Pleistocene glacial deposits that are missing from the waterways. The surveys can therefore bridge the gap between paleoseismic and marine geophysical studies, and test key elements of models proposed by regional-scale geophysical studies. Results from these surveys have: 1) documented several meters of vertical displacement on at least two separate faults in the Olympia area; 2) clarified the relationship between the Catfish Lake scarp and the underlying kink band in the Tacoma fault zone; 3) provided a first look at the structures beneath the north portion of the western Tacoma fault zone, north of previous marine profiles; 4) documented that deformation along the Seattle fault extends well east of Lake Sammamish; 5) imaged the Seattle fault beneath the Vasa Park trench; and 6) documented multiple fault strands in and south of the Seattle fault zone south of Bellevue. The results better constrain interpretations of paleoseismic investigations of past earthquakes on these faults, and provide targets for future paleoseismic studies.

  3. Temporal Variations of Magnetic Field Associated with Seismic Activity at Cerro Machin Volcano, Colombia

    NASA Astrophysics Data System (ADS)

    Londono, J. M.; Serna, J. P.; Guzman, J.

    2011-12-01

    A study of magnetic variations was carried out at Cerro Machin Volcano, Colombia for the period 2009 -2010, with two permanent magnetometers located at South and North of the central dome, separated about 2.5 km each other. After corrections, we found that there is no clear correlation between volcanic seismicity and temporal changes of magnetic field for each magnetometer station, if they are analyzed individually. On the contrary, when we calculated the residual Magnetic field (RMF), for each magnetometer, and then we made the subtraction between them, and plot it vs time, we found a clear correlation of changes in local magnetic field with the occurrence of volcanic seismicity (ML >1.6). We found a change in the RMF between 1584 nT and 1608 nT, each time that a volcano-tectonic earthquake occurred. The máximum lapse time between the previous change in RMF and the further occurrence of the earthquake is 24 days, with an average of 11 days. This pattern occurred more than 9 times during the studied period. Based on the results, we believed that the simple methodology proposed here, is a good tool for monitoring changes in seismicity associated with activity at Cerro Machín volcano. We suggest that the temporal changes of RMF at Cerro Machín Volcano, are associated with piezo-magnetic effects, due to changes in strain-stress inside the volcano, produced by the interaction between local faulting and magma movement.

  4. Geological and tectonic implications obtained from first seismic activity investigation around Lembang fault

    NASA Astrophysics Data System (ADS)

    Afnimar; Yulianto, Eko; Rasmid

    2015-12-01

    The Lembang fault located at northern part of populated Bandung basin is the most conspicuous fault that potentially capable in generating earthquakes. The first seismic investigation around Lembang fault has been done by deploying a seismic network from May 2010 till December 2011 to estimate the seismic activities around that fault. Nine events were recorded and distributed around the fault. Seven events were likely to be generated by the Lembang fault and two events were not. The events related to the Lembang fault strongly suggest that this fault has left-lateral kinematic. It shows vector movement of Australian plate toward NNE might have been responsible for the Lembang fault kinematic following its initial vertical gravitational movement. The 1-D velocity model obtained from inversion indicates the stratigraphy configuration around the fault composed at least three layers of low Vp/Vs at the top, high Vp/Vs at the middle layer and moderate Vp/Vs at the bottom. In comparison with general geology of the area, top, mid and bottom layers may consecutively represent Quaternary volcanic layer, pre-Quaternary water-filled sedimentary layer and pre-Quaternary basement. Two eastern events related to minor faults and were caused by a gravitational collapse.

  5. Physical modeling of the formation and evolution of seismically active fault zones

    USGS Publications Warehouse

    Ponomarev, A.V.; Zavyalov, A.D.; Smirnov, V.B.; Lockner, D.A.

    1997-01-01

    Acoustic emission (AE) in rocks is studied as a model of natural seismicity. A special technique for rock loading has been used to help study the processes that control the development of AE during brittle deformation. This technique allows us to extend to hours fault growth which would normally occur very rapidly. In this way, the period of most intense interaction of acoustic events can be studied in detail. Characteristics of the acoustic regime (AR) include the Gutenberg-Richter b-value, spatial distribution of hypocenters with characteristic fractal (correlation) dimension d, Hurst exponent H, and crack concentration parameter Pc. The fractal structure of AR changes with the onset of the drop in differential stress during sample deformation. The change results from the active interaction of microcracks. This transition of the spatial distribution of AE hypocenters is accompanied by a corresponding change in the temporal correlation of events and in the distribution of event amplitudes as signified by a decrease of b-value. The characteristic structure that develops in the low-energy background AE is similar to the sequence of the strongest microfracture events. When the AR fractal structure develops, the variations of d and b are synchronous and d = 3b. This relation which occurs once the fractal structure is formed only holds for average values of d and b. Time variations of d and b are anticorrelated. The degree of temporal correlation of AR has time variations that are similar to d and b variations. The observed variations in laboratory AE experiments are compared with natural seismicity parameters. The close correspondence between laboratory-scale observations and naturally occurring seismicity suggests a possible new approach for understanding the evolution of complex seismicity patterns in nature. ?? 1997 Elsevier Science B.V. All rights reserved.

  6. Encouraging the use of seismic methods for the hydrogeophysical characterization of the critical zone

    NASA Astrophysics Data System (ADS)

    Pasquet, S.; Bodet, L.; Chalikakis, K.; Flipo, N.; Longuevergne, L.; Guérin, R.

    2015-12-01

    The characterization, study and monitoring of hydrosystems mainly rely on piezometric and log data, e.g. on local information. Fortunately, hydrogeophysics provide appropriate tools to interpolate boreholes information and to image heterogeneities in the critical zone. When electrical and electromagnetic methods predominate in such context, we recently suggested the use of classical seismic methods not only to provide a characterization of the subsurface geometry, but also to estimate the mechanical properties of the critical zone influenced by its water content. We tested, on two critical zone observatories with distinct hydrogeological characteristics, the simultaneous estimation of pressure (P-) and shear (S-) wave seismic velocities (VP and VS, respectively) from P-wave travel-time tomography and surface-wave dispersion inversion respectively. On both sites, e.g. a fractured environment with strong discontinuities and a continuous multi-layered hydrosystem, we were able to image spatial and/or temporal variations of VP/VS ratio, whose evolution was strongly associated to the water content observed locally.

  7. Combined seismic and hydraulic method of modeling flow in fractured low permeability rocks

    SciTech Connect

    Witherspoon, P.A.; Long, J.C.S.; Majer, E.L.; Myer, L.R.

    1987-06-01

    Modeling flow of ground water in hard rocks where a network of fractures provides the dominant flow paths is a major problem. This paper summarizes a program of investigations currently underway in this laboratory to characterize the geometry of fractured rocks and develop methods of handling flow in such systems. Numerical models have been developed to investigate flow behavior in two- and three-dimensional fracture networks. The results demonstrate the insights that can be gained from modeling studies of fractured rocks. A key problem is gathering the necessary data on fracture geometry. Investigations have been started to determine how vertical seismic profiling (VSP) might be improved and applied to this problem. A VSP experiment in The Geysers geothermal field in northern California, where fracture orientation is known, produced shear wave splitting and velocity anisotropy in agreement with theory. The results suggest the potential application of 3-component, multi-source VSP data in determining fracture orientation and average spacing. We believe a combination of seismic and hydraulic methods can greatly enhance an understanding of fluid flow and transport in low permeability rock systems where fractures provide the dominant paths. 40 refs, 16 figs., 4 tabs.

  8. Surface and downhole shear wave seismic methods for thick soil site investigations

    USGS Publications Warehouse

    Hunter, J.A.; Benjumea, B.; Harris, J.B.; Miller, R.D.; Pullan, S.E.; Burns, R.A.; Good, R.L.

    2002-01-01

    Shear wave velocity-depth information is required for predicting the ground motion response to earthquakes in areas where significant soil cover exists over firm bedrock. Rather than estimating this critical parameter, it can be reliably measured using a suite of surface (non-invasive) and downhole (invasive) seismic methods. Shear wave velocities from surface measurements can be obtained using SH refraction techniques. Array lengths as large as 1000 m and depth of penetration to 250 m have been achieved in some areas. High resolution shear wave reflection techniques utilizing the common midpoint method can delineate the overburden-bedrock surface as well as reflecting boundaries within the overburden. Reflection data can also be used to obtain direct estimates of fundamental site periods from shear wave reflections without the requirement of measuring average shear wave velocity and total thickness of unconsolidated overburden above the bedrock surface. Accurate measurements of vertical shear wave velocities can be obtained using a seismic cone penetrometer in soft sediments, or with a well-locked geophone array in a borehole. Examples from thick soil sites in Canada demonstrate the type of shear wave velocity information that can be obtained with these geophysical techniques, and show how these data can be used to provide a first look at predicted ground motion response for thick soil sites. ?? 2002 Published by Elsevier Science Ltd.

  9. Feasibility study of the seismic reflection method in Amargosa Desert, Nye County, Nevada

    USGS Publications Warehouse

    Brocher, T.M.; Hart, P.E.; Carle, S.F.

    1990-01-01

    The seismic performance of steel moment-framed buildings has been of particular interest since brittle fractures were discovered at the beam-column connections of some frames following the M6.7 1994 Northridge earthquake. This report presents an investigation of the seismic behavior of an instrumented 13-story steel moment frame building located in the greater Los Angeles area of California. An extensive strong motion dataset, ambient vibration data, engineering drawings and earthquake damage reports are available for this building. The data are described and subsequently analyzed. The results of the analyses show that the building response is more complex than would be expected from its highly symmetrical geometry. The building's response is characterized by low damping in the fundamental mode, larger peak accelerations in the intermediate stories than at the roof, extended periods of vibration after the cessation of strong input shaking, beating in the response, and significant torsion during strong shaking at the top of the concrete piers which extend from the basement to the second floor. The analyses of the data and all damage detection methods employed except one method based on system identification indicate that the response of the structure was elastic in all recorded earthquakes. These findings are in general agreement with the results of intrusive inspections (meaning fireproofing and architectural finishes were removed) conducted on approximately 5 percent of the moment connections following the Northridge earthquake, which found no earthquake damage.

  10. Analyzing the subsurface structure using seismic refraction method: Case study STMKG campus

    SciTech Connect

    Wibowo, Bagus Adi; Ngadmanto, Drajat; Daryono

    2015-04-24

    A geophysic survey is performed to detect subsurface structure under STMKG Campus in Pondok Betung, South Tangerang, Indonesia, using seismic refraction method. The survey used PASI 16S24-U24. The waveform data is acquired from 3 different tracks on the research location with a close range from each track. On each track we expanded 24 geofons with spacing between receiver 2 meters and the total length of each track about 48 meters. The waveform data analysed using 2 different ways. First, used a seismic refractionapplication WINSISIM 12 and second, used a Hagiwara Method. From both analysis, we known the velocity of P-wave in the first and second layer and the thickness of the first layer. From the velocity and the thickness informations we made 2-D vertical subsurface profiles. In this research, we only detect 2 layers in each tracks. The P-wave velocity of first layer is about 200-500 m/s with the thickness of this layer about 3-6 m/s. The P-wave velocity of second layer is about 400-900 m/s. From the P-wave velocity data we interpreted that both layer consisted by similar materials such as top soil, soil, sand, unsaturated gravel, alluvium and clay. But, the P-wave velocity difference between those 2 layers assumed happening because the first layer is soil embankment layer, having younger age than the layer below.

  11. Combination of the discontinuous Galerkin method with finite differences for simulation of seismic wave propagation

    NASA Astrophysics Data System (ADS)

    Lisitsa, Vadim; Tcheverda, Vladimir; Botter, Charlotte

    2016-04-01

    We present an algorithm for the numerical simulation of seismic wave propagation in models with a complex near surface part and free surface topography. The approach is based on the combination of finite differences with the discontinuous Galerkin method. The discontinuous Galerkin method can be used on polyhedral meshes; thus, it is easy to handle the complex surfaces in the models. However, this approach is computationally intense in comparison with finite differences. Finite differences are computationally efficient, but in general, they require rectangular grids, leading to the stair-step approximation of the interfaces, which causes strong diffraction of the wavefield. In this research we present a hybrid algorithm where the discontinuous Galerkin method is used in a relatively small upper part of the model and finite differences are applied to the main part of the model.

  12. Active faults in the deformation zone off Noto Peninsula, Japan, revealed by high- resolution seismic profiles

    NASA Astrophysics Data System (ADS)

    Inoue, T.; Okamura, Y.; Murakami, F.; Kimura, H.; Ikehara, K.

    2008-12-01

    Recently, a lot of earthquakes occur in Japan. The deformation zone which many faults and folds have concentrated exists on the Japan Sea side of Japan. The 2007 Noto Hanto Earthquake (MJMA 6.9) and 2007 Chuetsu-oki Earthquake (MJMA 6.8) were caused by activity of parts of faults in this deformation zone. The Noto Hanto Earthquake occurred on 25 March, 2007 under the northwestern coast of Noto Peninsula, Ishikawa Prefecture, Japan. This earthquake is located in Quaternary deformation zone that is continued from northern margin of Noto Peninsula to southeast direction (Okamura, 2007a). National Institute of Advanced Industrial Science and Technology (AIST) carried out high-resolution seismic survey using Boomer and 12 channels short streamer cable in the northern part off Noto Peninsula, in order to clarify distribution and activities of active faults in the deformation zone. A twelve channels short streamer cable with 2.5 meter channel spacing developed by AIST and private corporation is designed to get high resolution seismic profiles in shallow sea area. The multi-channel system is possible to equip on a small fishing boat, because the data acquisition system is based on PC and the length of the cable is short and easy to handle. Moreover, because the channel spacing is short, this cable is very effective for a high- resolution seismic profiling survey in the shallow sea, and seismic data obtained by multi-channel cable can be improved by velocity analysis and CDP stack. In the northern part off Noto Peninsula, seismic profiles depicting geologic structure up to 100 meters deep under sea floor were obtained. The most remarkable reflection surface recognized in the seismic profiles is erosion surface at the Last Glacial Maximum (LGM). In the western part, sediments about 30 meters (40 msec) thick cover the erosional surface that is distributed under the shelf shallower than 100m in depth and the sediments thin toward offshore and east. Flexures like deformation in

  13. Seismic Imaging of VTI, HTI and TTI based on Adjoint Methods

    NASA Astrophysics Data System (ADS)

    Rusmanugroho, H.; Tromp, J.

    2014-12-01

    Recent studies show that isotropic seismic imaging based on adjoint method reduces low-frequency artifact caused by diving waves, which commonly occur in two-wave wave-equation migration, such as Reverse Time Migration (RTM). Here, we derive new expressions of sensitivity kernels for Vertical Transverse Isotropy (VTI) using the Thomsen parameters (ɛ, δ, γ) plus the P-, and S-wave speeds (α, β) as well as via the Chen & Tromp (GJI 2005) parameters (A, C, N, L, F). For Horizontal Transverse Isotropy (HTI), these parameters depend on an azimuthal angle φ, where the tilt angle θ is equivalent to 90°, and for Tilted Transverse Isotropy (TTI), these parameters depend on both the azimuth and tilt angles. We calculate sensitivity kernels for each of these two approaches. Individual kernels ("images") are numerically constructed based on the interaction between the regular and adjoint wavefields in smoothed models which are in practice estimated through Full-Waveform Inversion (FWI). The final image is obtained as a result of summing all shots, which are well distributed to sample the target model properly. The impedance kernel, which is a sum of sensitivity kernels of density and the Thomsen or Chen & Tromp parameters, looks crisp and promising for seismic imaging. The other kernels suffer from low-frequency artifacts, similar to traditional seismic imaging conditions. However, all sensitivity kernels are important for estimating the gradient of the misfit function, which, in combination with a standard gradient-based inversion algorithm, is used to minimize the objective function in FWI.

  14. The Influence of Seismic Amplification and Distanced Surcharge on the Active Thrust on Earth-Reinforced Walls

    SciTech Connect

    Biondi, Giovani; Grassi, Francesco; Maugeri, Michele

    2008-07-08

    The paper describes a closed form pseudo-static solution for the estimation of the active earth-pressure coefficient for an earth-reinforced wall assuming a non-uniform profile of the seismic coefficients along the wall height and a distanced uniformly-distributed surcharge on the backfill surface. The static and seismic hydraulic conditions of the backfill are also accounted for. A parametric analysis is carried out and the obtained results are discussed.

  15. Analysis of the seismicity activity of the volcano Ceboruco, Nayarit, Mexico

    NASA Astrophysics Data System (ADS)

    Rodriguez-Ayala, N. A.; Nunez-Cornu, F. J.; Escudero, C. R.; Zamora-Camacho, A.; Gomez, A.

    2014-12-01

    The Ceboruco is a stratovolcano is located in the state of Nayarit,Mexico (104 ° 30'31 .25 "W, 21 ° 7'28 .35" N, 2280msnm). This is an volcano active, as part of the Trans-Mexican Volcanic Belt, Nelson (1986) reports that it has had activity during the last 1000 years has averaged eruptions every 125 years or so, having last erupted in 1870, currently has fumarolic activity. In the past 20 years there has been an increase in the population and socio-economic activities around the volcano (Suárez Plascencia, 2013); which reason the Ceboruco study has become a necessity in several ways. Recent investigations of seismicity (Rodríguez Uribe et al., 2013) have classified the earthquakes in four families Ceboruco considering the waveform and spectral features. We present analysis included 57 days of seismicity from March to October 2012, in the period we located 97 events with arrivals of P and S waves clear, registered in at least three seasons, three components of the temporal network Ceboruco volcano.

  16. Present activity and seismogenic potential of a low-angle normal fault system (Città di Castello, Italy): Constraints from surface geology, seismic reflection data and seismicity

    NASA Astrophysics Data System (ADS)

    Brozzetti, Francesco; Boncio, Paolo; Lavecchia, Giusy; Pace, Bruno

    2009-01-01

    We present new constraints on an active low-angle normal fault system in the Città di Castello-Sansepolcro basin (CSB) of the northern Apennines of Italy. New field data from the geological survey of the Carta Geologica d' Italia (CARG project) define the surface geometry of the normal fault system and lead to an interpretation of the CROP 03 deep-crust seismic reflection profile (Castiglion Fiorentino-Urbania segment), with particular attention paid to the geometry of the Plio-Quaternary extensional structures. Surface and sub-surface geological data are integrated with instrumental and historical seismicity in order to define the seismotectonics of the area. Low-angle east-dipping reflectors are the seismic expression of the well-known Altotiberina Fault (AF), a regional extensional detachment on which both east- and west-dipping high-angle faults, bounding the CSB, sole out. The AF breakaway zone is located ˜ 10 km west of the CSB. Within the extensional allochthon, synthetic east-dipping planes prevail. Displacement along the AF is ˜ 4.5 km, which agrees with the cumulative offset due to its synthetic splays. The evolution of the CSB has mainly been controlled by the east-dipping fault system, at least since Early Pleistocene time; this system is still active and responsible for the seismicity of the area. A low level of seismic activity was recorded instrumentally within the CSB, but several damaging earthquakes have occurred in historical times. The instrumental seismicity and the intensity data points of the largest historical earthquakes (5 events with maximum MCS intensity of IX to IX-X) allow us to propose two main seismogenic structures: the Monte Santa Maria Tiberina (Mmax = 5.9) and Città di Castello (Mmax up to 6.5) normal faults. Both are synthetic splays of the AF detachment, dipping to the NE at moderate (45-50°) to low (25-30°) angles and cutting the upper crust up to the surface. This study suggests that low-angle normal faults (at least

  17. TOMO-ETNA MED-SUV.ISES an active seismic and passive seismic experiment at Mt. Etna volcano. An integrated marine and onland geophysical survey.

    NASA Astrophysics Data System (ADS)

    Ibáñez, Jesus. M.; Patane, Domenico; Puglisi, Guisseppe; Zuccarello, Lucciano; Bianco, Francesca; Luehr, Birger; Diaz-Moreno, Alejandro; Prudencio, Janire; Koulakov, Ivan; Del Pezzo, Edoardo; Cocina, Ornella; Coltelli, Mauro; Scarfi, Lucciano; De Gori, Pascuale; Carrion, Francisco

    2014-05-01

    An active seismic experiment to study the internal structure of Etna Volcano is going to carried out on Sicily and Aeolian islands. The main objective of the TOMO-ETNA MED-SUV.ISES experiment, beginning in summer 2014, is to perform a high resolution seismic tomography, in velocity and attenuation, in Southern Italy, by using active and passive seismic data, in an area encompassing outstanding volcanoes as Mt. Etna, and Aeolian volcanoes. The achievement of this objective is based on the integration and sharing of the in-situ marine and land experiments and observations and on the implementation of new instruments and monitoring systems. For the purpose, onshore and offshore seismic stations and passive and active seismic data generated both in marine and terrestrial environment will be used. Additionally, other geophysical data, mainly magnetic and gravimetric data will be considered to obtain a joint Upper Mantle-Crust structure that could permit to make progress in the understanding of the dynamic of the region. This multinational experiment which involves institutions from Spain, Italy, Germany, United Kingdom, Ireland, France, Malta, Portugal, Russia, USA and Mexico. During the experiment more than 6.600 air gun shots performed by the Spanish Oceanographic vessel "Sarmiento de Gamboa" will be recorder on a dense local seismic network consisting of 100 on land non-permanent stations, 70 on land permanent stations and 20-25 OBSs. Contemporaneously other marine geophysical measures will be performed using a marine Gravimeter LaCoste&Romberg Air-Sea Gravity System II and a Marine Magnetometer SeaSPY. The experiments will provide a unique data set in terms of data quantity and quality, and it will provide a detailed velocity and attenuation structural image of volcano edifice. The results will be essential in the development and interpretation of future volcanic models. It is noteworthy that this project is fully transversal, multidisciplinary and crosses several

  18. Complex Seismic Source Inversion Method with the Data Covariance Matrix: Application to the 2010 Haiti Earthquake

    NASA Astrophysics Data System (ADS)

    Kasahara, A.; Yagi, Y.

    2010-12-01

    In the finite fault source inversion, seismic source area has usually been approximated by simple fault plane model for simplicity. This approximation, however, may generate the correlated modeling errors originated from the focal mechanism variation in a rupture process, which contributed to biased results in the seismic waveform analysis. This effect becomes predominant for analysis of seismic data around the nodal planes. From CMT inversion analysis, the January 12, 2010 Haiti earthquake may accompany both strike and dip slip on different fault planes (Nettles and Hjörleifsdóttir, 2010, GJI). In addition, one single fault plane model cannot explain teleseismic body wave well due to complex source process and existence of many mechanism-sensitive stations. For waveform analysis of this earthquake, we developed inversion method that estimates moment tensor component for each space knot in seismic source area and applied it to teleseismic P-wave data recorded at FDSN network stations and Global Seismograph Network stations. In general, such high flexibility source model had caused the unstable and unrealistic result. To avoid this problem, we applied new formulation that considers the data covariance components of observed errors and modeling errors originated from uncertainty of Green's function (Yagi and Fukahata, 2010, AGU). It has already been shown that the new formulation can derive plausible solution without non-negative constraint. For inversion, we arranged space knots on the plane of which strike and dip are same as that of the USGS finite fault model. We confirmed that result is robust against change of strike, dip and knot interval. The result shows that P-axes in main rupture area are north-south direction, which is consistent with stress field of the region. Main rupture area can be divided into 3 patches, near the hypocenter, east and west side of the hypocenter patch, which have different focal mechanisms. Reverse fault is dominant in the

  19. Structural mapping in basin-and-range-like geology by electromagnetic methods: A powerful aid to seismic

    SciTech Connect

    Galibert, P.Y.; Andrieux, P.; Guerin, R.

    1996-11-01

    A case history is presented where electromagnetic (EM) methods were applied as a complement to seismic, for structural mapping in basin-and-range-like geology: 366 five-component magnetotelluric (MT) soundings were carried out together with 331 transient soundings (TDEM) along seismic lines. Due to high structural complexity, seismic shows a number of limitations. For the same reasons, MT is highly perturbed and three specific interpretation techniques were comprehensively applied: (1) a classical correction of static effect using TDEM sounding, to determine the high-frequency nondistorted apparent resistivities and thus the corrected tensor; (2) a so-called regional correction based upon the same concept as the static effect, to transform distorted resistivity curves due to the horst/graben situation into plausible 1D curves, through the use of nomograms built for 2D H-polarization situations; and (3) a stripping technique which made it possible to map areas where a deep conductive Mesozoic shale was present below carbonates, at a depth of 3 km. After the best MT interpretation was obtained along each line, it was integrated with seismic and with the results from two boreholes. A crude empirical law relating resistivity and acoustic velocity was established and the MT horizons were plotted on the two-way traveltime seismic sections. The final integrated cross-sections obtained are undoubtedly of greater use to the explorationist than the initial seismic sections alone and two wells were accurately predicted.

  20. Assessment and surveillance of active seismic regions through time series satellite data

    NASA Astrophysics Data System (ADS)

    Zoran, M. A.; Savastru, R. S.; Savastru, D. M.

    2013-08-01

    Satellite time-series data, coupled with ground based observations where available, can enable scientists to survey pre-earthquake signals in the areas of strong tectonic activity. Cumulative stress energy in seismic active regions under operating tectonic force manifests various earthquakes' precursors. Space-time anomalies of Earth's emitted radiation (radon in underground water and soil, thermal infrared in spectral range measured from satellite months to weeks before the occurrence of earthquakes etc.), and electromagnetic anomalies are considered as pre-seismic signals. This energy transformation may result in enhanced transient thermal infrared (TIR) emission, which can be detected through satellites equipped with thermal sensors like AVHRR (NOAA), MODIS (Terra/Aqua). This paper presents observations made using time series NOAA-AVHRR and MODIS satellite data-derived land surface temperature (LST) and outgoing longwave radiation (OLR) values in case of 27th 2004 earthquake recorded in seismic Vrancea region, Romania, using anomalous TIR signals as reflected in LST rise and high OLR values which followed similar growth pattern spatially and temporally. In all analyzed cases, starting with almost one week prior to a moderate or strong earthquake a transient thermal infrared rise in LST of several Celsius degrees (°C) and the increased OLR values higher than the normal have been recorded around epicentral areas, function of the magnitude and focal depth, which disappeared after the main shock. As Vrancea area has a significant regional tectonic activity in Romania and Europe, the joint analysis of geospatial and in-situ geophysical information is revealing new insights in the field of hazard assessment.

  1. High-Resolution Seismic Reflection Studies of Active Faults: a Case Study from Washington State

    NASA Astrophysics Data System (ADS)

    Liberty, L. M.; Pratt, T. L.

    2007-12-01

    In the past five years, new high-resolution seismic surveys have filled in gaps in our understanding of active structures beneath the Puget Lowland region of Washington State. The extensive forests have made recognition of active faults difficult, but new Light Distance and Ranging (LIDAR) detailed topographic data have made a major breakthrough in mapping active faults. Extensive regional and high-resolution marine seismic surveys have been fundamental to understanding the tectonic framework of the area. These marine profiles, however, lack coverage beneath water bodies that large ships cannot navigate and beneath city streets underlain by late Pleistocene glacial deposits that are missing from the waterways. Recent land surveys and profiles in restricted waterways can therefore bridge the gap between paleoseismic and marine geophysical studies, and test elements of models proposed by regional-scale geophysical studies. We have also been venturing into more congested areas to seismically image faults in key urban locations. Results from recent surveys have: 1) documented new faults that had long been suspected in the Olympia area; 2) clarified the relationship between the LIDAR scarps and observed structures across the Tacoma fault zone; 3) provided a window into structures beneath the north and eastern portions of the western Tacoma fault zone; 4) documented deformation along the Seattle fault near a paleoseismic trench; 5) mapped the eastern part the Seattle fault zone beyond its previously mapped limits; and 6) documented multiple fault strands in the Seattle fault zone in the cities of Bellevue and Seattle. The results better constrain interpretations of paleoseismic data collected on these faults, and provide targets for future paleoseismic studies.

  2. Geology of the area of induced seismic activity at Monticello Reservoir, South Carolina

    SciTech Connect

    Secor, D.T. Jr.; Smith, W.A.; Snoke, A.W.; Peck, L.S.; Pitcher, D.M.; Prowell, D.C.; Simpson, D.H.

    1982-08-10

    This study provides geological background information necessary for an evaluation of the earthquake hazard in an area of induced seismic activity at Monticello Reservoir, South Carolina. This region contains a thick stratified sequence of Proterozoic Z and Cambrian metasedimentary and metavolcanic rocks. In the early to middle Paleozoic, this sequence was recrystallized and deformed under metamorphic conditions that ranged from greenschist to amphibolite facies and experienced at least two episodes of folding. The region has been intruded by late kinematic to postkinematic granitoid plutons of Silurian and Carboniferous ages and by numerous northwest trending diabase diks of Late Traissic and Early Jurassic age. The region south of Monticello Reservoir in the Carolina slate belt experienced two episodes of faulting in the late Paleozoic and/or early to middle Mesozoic. The older group of faults trends approximately east, has only small displacements, and is characterized by extensive silicifiction of the fault zones. The younger group of faults trends approximately north has experienced dip slip displacements up to 1700 m and is characterized by carbonate mineralization in the fault zones. Both sets of faults are cut by an undeformed diabase dike of Late Triassic or Early Jurassic age. The induced seismic activity around Monticello Reservoir is occurring in a heterogeneous quartz monzonite pluton of Carboniferous age. The pluton contains large enclaves of country rock and is cut by numerous, diversely oriented small faults and joint. These local inhomogeneities in the pluton together with an irregular stress field are interpreted to control the diffuse seismic activity around the reservoir. In view of the apparent absence of lengthy faults it is unlikely that a large-magnitude earthquake will occur in response to the stress and pore pressure changes related to the impoundment of Monticello Reservoir.

  3. Tomography and Methods of Travel-Time Calculation for Regional Seismic Location

    SciTech Connect

    Myers, S; Ballard, S; Rowe, C; Wagoner, G; Antolik, M; Phillips, S; Ramirez, A; Begnaud, M; Pasyanos, M E; Dodge, D A; Flanagan, M P; Hutchenson, K; Barker, G; Dwyer, J; Russell, D

    2007-07-02

    We are developing a laterally variable velocity model of the crust and upper mantle across Eurasia and North Africa to reduce event location error by improving regional travel-time prediction accuracy. The model includes both P and S velocities and we describe methods to compute travel-times for Pn, Sn, Pg, and Lg phases. For crustal phases Pg and Lg we assume that the waves travel laterally at mid-crustal depths, with added ray segments from the event and station to the mid crustal layer. Our work on Pn and Sn travel-times extends the methods described by Zhao and Xie (1993). With consideration for a continent scale model and application to seismic location, we extend the model parameterization of Zhao and Xie (1993) by allowing the upper-mantle velocity gradient to vary laterally. This extension is needed to accommodate the large variation in gradient that is known to exist across Eurasia and North African. Further, we extend the linear travel-time calculation method to mantle-depth events, which is needed for seismic locators that test many epicenters and depths. Using these methods, regional travel times are computed on-the-fly from the velocity model in milliseconds, forming the basis of a flexible travel time facility that may be implemented in an interactive locator. We use a tomographic technique to improve upon a laterally variable starting velocity model that is based on Lawrence Livermore and Los Alamos National Laboratory model compilation efforts. Our tomographic data set consists of approximately 50 million regional arrivals from events that meet the ground truth (GT) criteria of Bondar et al. (2004) and other non-seismic constraints. Each datum is tested to meet strict quality control standards that include comparison with established distance-dependent travel-time residual populations relative to the IASPIE91 model. In addition to bulletin measurements, nearly 50 thousand arrival measurements were made at the national laboratories. The tomographic

  4. Movement of the Earth pole and the seismic activity in 2001-2012

    NASA Astrophysics Data System (ADS)

    Andreev, Aleksey; Zabbarova, Regina; Lapaeva, Valentina; Nefedyev, Yuri

    2014-05-01

    The relationship between the parameters which characterize the movement of the Earth pole and seismic activity are considered. The correlation of the considered parameters is studied. The discussions about the relationship of poles movement and irregularity in speed of Earth rotation with seismic activity were actively performed in 60- 70th years of last century. Mainly, the influence of seismicity on pole movement was considered in this works. In particular, the question about excitation of a pole by earthquakes chandler's fluctuations was studied. An interest in the similar researches continues till now. The chandler's movements investigations and their relation with rotation of the Earth and seismicity were proceeded. The correlation between appearance of earthquakes and abnormal evasion of time and latitude for the observatories located near an epicenter was also discussed. What changes in position of the Earth pole do occur as a result of the strongest earthquakes? To answer on this question it is necessary to study variations of "an average pole", where the basic periodic components in movement of a pole having amplitude 0.1"-0.3" are accepted. To perform the analysis of the pole co-ordinates (X and Y) the International service of the Earth rotation for 1995-2012 have been considered. Linear Orlov-Saharov transformation has been applied to an exception of the periodic movement. On the basis of this positions changes of an average pole (aperiodicity displacement and long periodical variations of an axis of rotation in a Earth body) have been calculated with an interval of 0.1 years. Was found the changes of position of an average pole of the Earth was preceded the most considerable seismic events of the beginning of 21 century. As a whole, the increase of seismic activity has begun after 2002 only. For example, there were 2 strong earthquakes with magnitude 7 and more (Salvador, India) in 2001 , 2 earthquakes (Tajikistan, Taiwan) occurred in 2002, and 5

  5. Preliminary Results from the iMUSH Active Source Seismic Experiment

    NASA Astrophysics Data System (ADS)

    Levander, Alan; Kiser, Eric; Palomeras, Imma; Zelt, Colin; Schmandt, Brandon; Hansen, Steve; Harder, Steven; Creagar, Kenneth; Vidale, John; Abers, Geoffrey

    2015-04-01

    iMUSH (imaging Magma Under Saint Helens) is a US NSF sponsored multi-disciplinary investigation of Mount Saint Helens (MSH), currently the most active volcano in the Cascades arc in the northwestern United States. The project consists of active and passive seismic experiments, extensive magnetotelluric sounding, and geological/geochemical studies involving scientists at 7 institutions in the U.S. and Europe. The long-term goal of the seismic project is to combine analysis of the active source data with that of data from the 70 element broadband seismograph operating from summer 2014 until 2016. Combining seismic and MT analyses with other data, we hope to image the MSH volcanic plumbing system from the surface to the subducting Juan de Fuca slab. Here we describe preliminary results of the iMUSH active source seismic experiment, conducted in July and August 2014. The active source experiment consisted of twenty-three 454 or 908 kg weight shots recorded by ~3500 seismographs deployed at ~6,000 locations. Of these instruments, ~900 Nodal Seismic instruments were deployed continuously for two weeks in an areal array within 10 km of the MSH summit. 2,500 PASSCAL Texan instruments were deployed twice for five days in 3 areal arrays and 2 dense orthogonal linear arrays that extended from MSH to distances > 80 km. Overall the data quality from the shots is excellent. The seismograph arrays also recorded dozens of micro-earthquakes beneath the MSH summit and along the MSH seismic zone, and numerous other local and regional earthquakes. In addition, at least one low frequency event beneath MSH was recorded during the experiment. At this point we have begun various types of analysis of the data set: We have determined an average 1D Vp structure from stacking short-term/long-term average ratios, we have determined the 2-D Vp structure from ray-trace inversions along the two orthogonal profiles (in the NW-SE and NE-SW directions), and we have made low-fold CMP stacks of the

  6. Active Tectonics of off-Hokuriku, Central Japan, by two ships seismic reflection profiling

    NASA Astrophysics Data System (ADS)

    Kato, Naoko; Sato, Hiroshi; Ishiyama, Tatsuya; Abe, Susumu; Shiraishi, Kazuya

    2015-04-01

    Along the southern to eastern margin of the Sea of Japan, active faults are densely distributed. These submarine active faults produced tsunami disasters, such as 1983 Nihonkai-chubu earthquake (M7.7) and 1993 Hokkaido Nansei-oki earthquake (M7.8). To estimate tsunami hazards, we performed deep seismic reflection profiling to obtain the information of tsunami source faults, off-Hokuriku area in the central part of Honshu, Japan. The survey is carried out as a part of research project named "the integrated research project on seismic and tsunami hazards around the Sea of Japan" funded by MEXT. To obtain long offset data in busy marine activity area, we used two vessels; a gun-ship with 3020 cu. inch air-gun and a cable-ship with a 2-km-long, streamer cable with 156 channels and 480 cu. inch air-gun. Common-midpoint reflection data were acquired using two ships at 4 km offset. The survey area consists of stretched continental crust associated with rifting and opening of the Sea of Japan in early Miocene and is marked by densely distributed syn-rift normal faults. Fault reactivation of normal faults as reverse faults is common. Two phases of fault reactivation are identified from the seismic sections after termination of opening of the Sea of Japan. One is the late Miocene NS trending shortening deformation. This is produced by NS-trending convergence of the Shikoku basin (15 Ma), which belongs to the Philippine Sea plate (PHS) to SW Japan at Nankai trough (Kimura et al., 2005). After the initiation of the subduction of PHS at Nankai trough, the strong shortening deformation is terminated and the fold-and-thrust belt was unconformably covered by sub-horizontal Pliocene sediments. Some horizons of unconformities represent multiple events of shortening driven from the subduction interface. Some normal faults reactivated as active strike-slip and reverse faults in Quaternary. Well observed example is the 2007 Noto peninsula earthquake (M6.8). The 2007 Noto peninsula

  7. The application of seismic stratigraphic methods on exploration 3D seismic data to define a reservoir model in OPL 210, Deepwater Nigeria

    SciTech Connect

    Ragnhild, L.; Ventris, P.; Osahon, G.

    1995-08-01

    OPL 210 lies in deepwater on the northwestern flank of the Niger Delta. The partners in this block are Allied Energy and The Statoil and BP Alliance. The license has a 5 year initial exploration phase and carries a 2 well commitment. At present the database comprises a 1 x 1 km grid of 2D seismic across the block, and 450 sq. km of 3D in an area of special interest. A larger 3D survey is planned for 1995. Little is known about the reservoir in the deep water, but we expect our main target to be ponded slope and basin turbidites. As such the bulk of the shelf well data available has little or no relevance to the play type likely to be encountered. Prior to drilling, seismic stratigraphy has been one of several methods used to generate a consistent predictive reservoir model. The excellent quality and high resolution of the 3D data have allowed identification and detailed description of several distinctive seismic facies. These facies are described in terms of their internal geometries and stacking patterns. The geometries are then interpreted based on a knowledge of depositional processes from analog slope settings. This enables a predictive model to be constructed for the distribution of reservoir within the observed facies. These predictions will be tested by one of the first wells drilled in the Nigerian deepwater in mid 1995.

  8. Field Report on the iMUSH Active Source Seismic Experiment

    NASA Astrophysics Data System (ADS)

    Kiser, E.; Levander, A.; Schmandt, B.; Palomeras, I.; Harder, S. H.; Creager, K. C.; Vidale, J. E.; Malone, S. D.

    2014-12-01

    In the second half of July we completed the iMUSH active source seismic experiment, one component of the Imaging Magma Under Saint Helens project. A team of ~75 volunteers deployed 3500 seismographs to ~5920 locations on and around Mount St. Helens over the course of 3 weeks. This instrument deployment was accompanied by 23 shots distributed around the volcano. Instrumentation consisted of ~2550 Reftek 125A (Texan) seismographs with 4.5 Hz geophones, and 920 Nodal Seismic recorders with 10 Hz geophones. The shots were also recorded by the permanent stations of the Pacific Northwest Seismograph Network and 70 iMUSH broadband seismographs. Fifteen of the shots, 424 kg each, formed two rings around Mount Saint Helens at 15 km and 30 km radius from the summit. Eight of the shots, 828 kg each, were fired at distances of 50 to 80 km from MSH on NW-SE and NE-SW azimuths. The deployment geometry consisted of two lines oriented NW/SE and NE/SW, and three arrays. The offset of the lines ranged from 150 km to 190 km with an average spacing of 200 m. The first array was centered on the volcano with a radius of 30 km, and required both driving and hiking to deploy. Arrays two and three were set out with, and centered on, the NW/SE line. These arrays had a distance range from MSH of 30-75 km and an azimuth range of about 100 degrees. In addition to this large-scale deployment, we set out 7 beamforming arrays approximately collocated with iMUSH broadband seismographs, and above clusters of seismicity in the region. The aperture of these arrays was about 1 km with an instrument spacing of 100 m. The final deployment ended only days before the AGU abstract deadline, so we have not yet examined all of the data. However, the preliminary indications are that signal to noise is excellent: The shots, several of which registered on PNSN as ML>2.1, carried across the entire array, and were recorded as far away as Seattle and Corvallis on permanent stations. The array also recorded a

  9. Geoazur's contribution in instrumentation to monitor seismic activity of the Earth

    NASA Astrophysics Data System (ADS)

    Yates, B.; Hello, Y.; Anglade, A.; Desprez, O.; Ogé, A.; Charvis, P.; Deschamps, A.; Galve, A.; Nolet, G.; Sukhovich, A.

    2011-12-01

    Seismic activity in the earth is mainly located near the tectonic plate boundaries, in the deep ocean (expansion centers) or near their margins (subduction zones). Travel times and waveforms of recorded seismograms can be used to reconstruct the three-dimensional wave speed distribution in the earth with seismic tomography or to image specific boundaries in the deep earth. Because of the lack of permanent sea-bottom seismometers these observation are conducted over short period of time using portable ocean bottom seismometers. Geaozur has a long experience and strong skills in designing and deploying Ocean Bottom Seismometers all over the world. We have developed two types of ocean bottom instruments. The "Hippocampe" for long deployment and "Lady bug" for aftershock monitoring or for fast overlaps during wide angle experiments. Early warning systems for tsunamis and earthquakes have been developed in recent years but these need real time data transmission and direct control of the instrument. We have developed a permanent real time Broad Band instrument installed in the Mediterranean Sea and connected to the Antares Neutrinos telescope. This instrument offers all the advantages of a very heavy and costly installation, such as the ability to do real-time seismology on the seafloor. Such real-time seafloor monitoring is especially important for seismic hazard. Major earthquakes cause human and economic losses directly related to the strong motion of the ground or by induced phenomena such as tsunamis and landslides. Fiber optical cables provide a high-capacity lightweight alternative to traditional copper cables. Three-component sensors analyze permanently the noise signal and detect the events to record. Major events can force the network to transmit data with almost zero lag time. The optical link also allows us to retrieve events at a later date. However, OBSs alone can never provide the density and long term, homogeneous data coverage needed for local and global

  10. Fault mirrors of seismically active faults: A fossil of small earthquakes at shallow depths

    NASA Astrophysics Data System (ADS)

    Kuo, L.; Song, S.; Suppe, J.

    2013-12-01

    Many faults are decorated with naturally polished and glossy surfaces named fault mirrors (FMs) formed during slips. The characterization of FMs is of paramount importance to investigate physico-chemical processes controlling dynamic fault mechanics during earthquakes. Here we present detailed microstructural and mineralogical observations of the FMs from borehole cores of seismically active faults. The borehole cores were recovered from 600 to 800 m depth located in the hanging wall of the Hsiaotungshi fault in Taiwan which ruptured during 1935 Mw7.1 Hsinchu-Taichung earthquake. Scanning electron microscope (SEM) images of FMs show that two distinct textural domains, fault gouge and coated materials (nanograins, melt patchs, and graphite), were cut by a well-defined boundary. Melt patches and graphite, determined by X-ray diffraction (XRD), Transmission electron microscope (TEM), and SEM-EDS analysis, were found to be distributed heterogeneously on the slip surfaces. On the basis of the current kinematic cross section of the Hsiaotungshi fault, all the FMs were exhumed less than 5 km, where ambient temperatures are less than 150°C. It seems that the amorphous materials on the FMs were generated by seismic slips. The sintering nanograins coating the slip surfaces was also suggested to be produced at high slip rates from both natural observation and recent rock deformation experiments. In addition, graphite could be produced by seismic slips and lubricate the fault based on the rock deformation experiments. Our observation suggests that the FMs were composed of several indicators of coseismic events (melt patches, sintering nanograins, and graphite) corresponding to small thermal perturbation generated by seismic slips. Although the contribution of these coseismic indicators on frictional behavior remains largely unknown, it suggests that multiple dynamic weakening mechanisms such as flash heating, powder lubrication and graphitization may be involved during

  11. A Feasibility Study of Non-Seismic Geophysical Methods forMonitoring Geologic CO2 Sequestration

    SciTech Connect

    Gasperikova, Erika; Hoversten, G. Michael

    2006-07-01

    Because of their wide application within the petroleumindustry it is natural to consider geophysical techniques for monitoringof CO2 movement within hydrocarbon reservoirs, whether the CO2 isintroduced for enhanced oil/gas recovery or for geologic sequestration.Among the available approaches to monitoring, seismic methods are by farthe most highly developed and applied. Due to cost considerations, lessexpensive techniques have recently been considered. In this article, therelative merits of gravity and electromagnetic (EM) methods as monitoringtools for geological CO2 sequestration are examined for two syntheticmodeling scenarios. The first scenario represents combined CO2 enhancedoil recovery (EOR) and sequestration in a producing oil field, theSchrader Bluff field on the north slope of Alaska, USA. The secondscenario is a simplified model of a brine formation at a depth of 1,900m.

  12. Forward modeling of 4D seismic response to the CO2 injection at the Ketzin pilot site with the reflectivity method

    NASA Astrophysics Data System (ADS)

    Ivanova, Alexandra; Ivandic, Monika; Kempka, Thomas; Gil, Magdalena; Bergmann, Peter; Lüth, Stefan

    2014-05-01

    When CO2 replaces brine as a free gas it is well known to affect the elastic properties of porous media considerably. 3D seismic time-lapse surveys (4D seismics) have proven to be a suitable technique for monitoring of injected CO2. Forward modeling of a 4D seismic response to the CO2 fluid substitution in a storage reservoir is an important step in such studies. In order to track the migration of CO2 at the Ketzin pilot site (Germany), 3D time-lapse seismic data were acquired by means of a baseline (pre-injection) survey in 2005 and the monitor surveys in 2009 and 2012. Results of 4D seismic forward modeling with the reflectivity method suggest that effects of the injected CO2 on the 4D seismic data at the Ketzin pilot site are significant regarding both seismic amplitudes and time delays. They prove the corresponding observations in the real 4D seismic data at the Ketzin pilot site. However reservoir heterogeneity and seismic resolution, as well as random and coherent seismic noise are negative factors to be considered while the interpretation. In spite of these negative factors, results of 4D seismic forward modeling with the reflectivity method support the conclusion that the injected CO2 can be monitored at the Ketzin pilot site both qualitatively and quantitatively.

  13. Integrating EarthScope seismic, GPS, and other active Earth observations into informal education programs in parks and museums

    NASA Astrophysics Data System (ADS)

    Lillie, R. J.; Goddard, C.; Braunmiller, J.; Trehu, A. M.

    2008-12-01

    EarthScope is a National Science Foundation program that uses seismic, GPS, and other geophysical devices to explore the structure and evolution of the North American continent and to understand the physical processes that cause earthquakes and volcanic eruptions. Two challenges facing the EarthScope community include providing the public with access to timely science results and presenting complex data and related principles in language and formats accessible to varied audiences. A series of workshops for park and museum educators combines scientific observations with interpretive methods to convey stories of the dynamic landscape of the western United States. The initial workshop, held at the Mt. Rainier National Park Education Center, focused on how EarthScope data and scientific results enhance the "sense of place" represented by the coastlines, valleys, and mountains of the Cascadia Subduction Zone. Participants learned how seismic and GPS instruments monitor earthquakes, volcanoes, and tsunamis that reveal the power of Earth's forces in the Pacific Northwest. A second workshop, held at the University of Nevada-Reno, related EarthScope observations to active continental rifting in the Basin and Range Province. Future workshops will focus on the San Andreas Fault, Colorado Plateau, Rio Grande Rift, and other regions. The workshops are helping interpretive professionals learn how observations of dynamic landscapes can be used to connect various audiences to many of the physical, historical, and cultural aspects of a park or museum site.

  14. Comparison of Vibroseis and explosive source methods for deep crustal seismic reflection profiling in the Basin and Range province

    USGS Publications Warehouse

    Brocher, T.M.; Hart, P.E.

    1991-01-01

    Direct comparison of low-fold, high-energy explosive and high-fold, lower-energy Vibroseis methods for acquiring deep crustal seismic reflection data in the Basin and Range Province suggests that the high-fold common midpoint (CMP) method there does not provide the best possible image of lower crustal structure. -from Authors

  15. Time Variation of Seismic Anisotropy, Stress and Cracks on Active Volcanoes (Invited)

    NASA Astrophysics Data System (ADS)

    Savage, M. K.

    2013-12-01

    We summarize measurements of seismic anisotropy and its relation to other geophysical measurements of stress and cracks on eleven active volcanoes; Unzen (Unz), Sakurajima (Sak), Aso, Asama (Asm) and Kirishima (Kir) in Japan; Okmok (Okm) in Alaska, Ruapehu (Rua) and Tongariro (Ton) in New Zealand, Soufriere Hills (Sou) in Montserrat, Kilauea (Kil) in Hawaii and Piton de la Fournaise (PdF) in La Reunion. We used the MFAST shear wave splitting computer code, an objective code that is fully automatic except for the S arrival pick. Fast polarization directions (phi) should be parallel to cracks and hence the maximum horizontal stress direction. Time delays (dt) increase with path length and percent anisotropy, usually related to crack density. Where possible we used S waves from deep earthquakes to ensure that the movement of the earthquakes was not correlated with the volcanic activity. At some volcanoes we used families of repeating events with similar waveforms and at most volcanoes we also computed splitting at earthquakes local to the volcano. We compared the phi and dt variation in time to eruption occurrences and to other available parameters including seismicity rate, b-values, focal mechanisms, isotropic velocity changes from noise cross-correlation, Vp/Vs ratios, Geodetic measurements such as GPS and tilt, and gas flux. All volcanoes had some stations with excellent shear wave arrivals that yielded measureable splitting. Individual measurements showed scatter in most areas, but at most of the volcanoes, moving averages of phi or dt (or both) yielded time variations that correlated with other measurements related to volcanic activity or to stress changes or changes in crack-filling material such as gas flux. The multiplet studies did not yield slowly varying splitting but instead showed distinct jumps in splitting parameters at various times, which appears to be caused in part by cycle skipping. Time resolution of changes depends on the seismicity available

  16. Thermal anomalies in fumaroles at Vulcano island (Italy) and their relationship with seismic activity and stress-induced permeability changes

    NASA Astrophysics Data System (ADS)

    Madonia, Paolo; Cusano, Paola; Diliberto, Iole Serena; Cangemi, Marianna

    2016-04-01

    Fumarole thermal monitoring is a useful tool in the evaluation of volcanic activity, since temperatures strongly relate to the upward flux of magmatic volatiles. Once depurated from meteorological noise, their variations can reflect permeability changes due to crustal stress dynamics eventually associated to seismic activity. In this work, we discuss a fumarole temperature record acquired in the period September 2009 - May 2012 at Vulcano island (Italy), during which changes of volcanic state, local seismic activity and teleseisms occurred. Apart from positive thermal anomalies driven by increments in volcanic activity, we observed 3 episodes at least of concurrence between tectonic earthquakes and fumarole temperature increments, with particular reference to the local August 16th, 2010 Lipari earthquake, the March 11th, 2011 Sendai-Honshu (Japan) earthquake and a seismic swarm occurred along the Tindari-Letojanni fault in July-August 2011. We interpreted the seismic-related anomalies as "crustal fluid transients", i.e. signals of volcanogenic vapour flow variations induced by stress-induced permeability changes. From this perspective fumarolic activity can be considered as a tracer of geodynamic instability but, since seismic and volcanic phenomena are in mutual cause-effect relationships, a multidisciplinary observation system is mandatory for correctly addressing thermal data interpretation.

  17. Assessment of Stress-Strain State of Seismically Active Region of Armenia According to the Results of Hydrogeodynamic Monitoring

    NASA Astrophysics Data System (ADS)

    Munkhsaikhan, A.; Avetyan, R.; Pashayan, R.

    2015-12-01

    Results of hydrogeodynamic monitoring, data of the chemical analysis of water were compared with seismic regime of the region aiming to study and evaluate stress-strain state of earth crust of Central Armenia during 2010-2014. Methodolgy of processing water level data came down to allocating tectonic-seismic stress taking into account the following factors: atmosphere pressure, precipitations, size of snow cover and tidal variations. The overall picture of the stress-strain state of the territory yearly was defined by calculated value of deformations around each hydrogeodynamic borehole taking into account the number of seismic events which occurred during that period. Maps of the isolines of equal values of deformations were drawn which reflect space-time regularity of the modern geodynamics of Armenia. The resluts of the correlation between parametres of hydrogeochemical effects and charaectreristics of earthquakes have shown that statistically significant connection between effect parametres (effect time, extremum time) and characteristics of seismic events (energetic class, epicentral distance ) was determined for the changes of parameters of the chemical composition of underground water. Histogram of changes of values of geochemical components of waters of mineral springs in space was drawn for the period of monitoring observations. The analysis of data allowed allocating more informative parameters of chemical composition of mineral water: gas component-carbon dioxide (CO2). Magnesium -Mg2+, chloride -Cl- where allocated from the macrocomponenet composition. According to the catalogue of seismic data there was drawn diagram of the frequency of earthquakes, reflecting the distribution of the earthquake number according to magnitude M (according to rule LgN=a-bM) in logarithmic scale. Coefficient of seismic activity was calculated - a, by which variations seismic activity of the region is evaluated. Thus, modern tectonic movements of earth crust of Armenia are

  18. Geomorphic evidence of active faults growth in the Norcia seismic area (central Apennines, Italy)

    NASA Astrophysics Data System (ADS)

    Materazzi, Marco; Aringoli, Domenico; Farabollini, Piero; Giacopetti, Marco; Pambianchi, Gilberto; Tondi, Emanuele; Troiani, Francesco

    2016-04-01

    Fault-growth by segment linkage is one of the fundamental processes controlling the evolution, in both time and the space, of fault systems. In fact, step-like trajectories shown by length-displacement diagrams for individual fault arrays suggest that the development of evolved structures result by the linkage of single fault segments. The type of interaction between faults and the rate at which faults reactivate not only control the long term tectonic evolution of an area, but also influence the seismic hazard, as earthquake recurrence intervals tend to decrease as fault slip rate increase. The use of Geomorphological investigations represents an important tool to constrain the latest history of active faults. In this case, attention has to be given to recognize morphostructural, historical, environmental features at the surface, since they record the long-term seismic behavior due to the fault growth processes (Tondi and Cello, 2003). The aim of this work is to investigate the long term morphotectonic evolution of a well know seismic area in the central Apennines: the Norcia intramontane basin (Aringoli et al., 2005). The activity of the Norcia seismic area is characterized by moderate events and by strong earthquakes with maximum intensities of X-XI degrees MCS and equivalent magnitudes around 6.5±7.0 (CPTI, 2004). Based on the morphostructural features as well as on the historical seismicity of the area, we may divide the Norcia seismic area into three minor basins roughly NW-SE oriented: the Preci sub-basin in the north; the S. Scolastica and the Castel S. Maria sub-basins in the south. The wider basin (S. Scolastica) is separated from the other two by ridges transversally oriented with respect the basins themselves; they are the geomorphological response to the tectonic deformation which characterizes the whole area. Other geomorphological evidences of tectonic activity are represented by deformation of old summit erosional surfaces, hydrographic network

  19. Numerical simulation of seismic wave propagation produced by earthquake by using a particle method

    NASA Astrophysics Data System (ADS)

    Takekawa, Junichi; Madariaga, Raul; Mikada, Hitoshi; Goto, Tada-nori

    2012-12-01

    We propose a forward wavefield simulation based on a particle continuum model to simulate seismic waves travelling through a complex subsurface structure with arbitrary topography. The inclusion of arbitrary topography in the numerical simulation is a key issue not only for scientific interests but also for disaster prediction and mitigation purposes. In this study, a Hamiltonian particle method (HPM) is employed. It is easy to introduce traction-free boundary conditions in HPM and to refine the particle density in space. Any model with complex geometry and velocity structure can be simulated by HPM because the connectivity between particles is easily calculated based on their relative positions and the free surfaces are automatically introduced. In addition, the spatial resolution of the simulation could be refined in a simple manner even in a relatively complex velocity structure with arbitrary surface topography. For these reasons, the present method possesses great potential for the simulation of strong ground motions. In this paper, we first investigate the dispersion property of HPM through a plane wave analysis. Next, we simulate surface wave propagation in an elastic half space, and compare the numerical results with analytical solutions. HPM is more dispersive than FDM, however, our local refinement technique shows accuracy improvements in a simple and effective manner. Next, we introduce an earthquake double-couple source in HPM and compare a simulated seismic waveform obtained with HPM with that computed with FDM to demonstrate the performance of the method. Furthermore, we simulate the surface wave propagation in a model with a surface of arbitrary topographical shape and compare with results computed with FEM. In each simulation, HPM shows good agreement with the reference solutions. Finally, we discuss the calculation costs of HPM including its accuracy.

  20. A new method to identify earthquake swarms applied to seismicity near the San Jacinto Fault, California

    NASA Astrophysics Data System (ADS)

    Zhang, Qiong; Shearer, Peter M.

    2016-02-01

    Understanding earthquake clustering in space and time is important but also challenging because of complexities in earthquake patterns and the large and diverse nature of earthquake catalogs. Swarms are of particular interest because they likely result from physical changes in the crust, such as slow slip or fluid flow. Both swarms and clusters resulting from aftershock sequences can span a wide range of spatial and temporal scales. Here we test and implement a new method to identify seismicity clusters of varying sizes and discriminate them from randomly occurring background seismicity. Our method searches for the closest neighboring earthquakes in space and time and compares the number of neighbors to the background events in larger space/time windows. Applying our method to California's San Jacinto Fault Zone (SJFZ), we find a total of 89 swarm-like groups. These groups range in size from 0.14 to 7.23 km and last from 15 minutes to 22 days. The most striking spatial pattern is the larger fraction of swarms at the northern and southern ends of the SJFZ than its central segment, which may be related to more normal-faulting events at the two ends. In order to explore possible driving mechanisms, we study the spatial migration of events in swarms containing at least 20 events by fitting with both linear and diffusion migration models. Our results suggest that SJFZ swarms are better explained by fluid flow because their estimated linear migration velocities are far smaller than those of typical creep events while large values of best-fitting hydraulic diffusivity are found.

  1. A new method to identify earthquake swarms applied to seismicity near the San Jacinto Fault, California

    NASA Astrophysics Data System (ADS)

    Zhang, Qiong; Shearer, Peter M.

    2016-05-01

    Understanding earthquake clustering in space and time is important but also challenging because of complexities in earthquake patterns and the large and diverse nature of earthquake catalogues. Swarms are of particular interest because they likely result from physical changes in the crust, such as slow slip or fluid flow. Both swarms and clusters resulting from aftershock sequences can span a wide range of spatial and temporal scales. Here we test and implement a new method to identify seismicity clusters of varying sizes and discriminate them from randomly occurring background seismicity. Our method searches for the closest neighbouring earthquakes in space and time and compares the number of neighbours to the background events in larger space/time windows. Applying our method to California's San Jacinto Fault Zone (SJFZ), we find a total of 89 swarm-like groups. These groups range in size from 0.14 to 7.23 km and last from 15 min to 22 d. The most striking spatial pattern is the larger fraction of swarms at the northern and southern ends of the SJFZ than its central segment, which may be related to more normal-faulting events at the two ends. In order to explore possible driving mechanisms, we study the spatial migration of events in swarms containing at least 20 events by fitting with both linear and diffusion migration models. Our results suggest that SJFZ swarms are better explained by fluid flow because their estimated linear migration velocities are far smaller than those of typical creep events while large values of best-fitting hydraulic diffusivity are found.

  2. Accelerating seismic interpolation with a gradient projection method based on tight frame property of curvelet

    NASA Astrophysics Data System (ADS)

    Cao, Jingjie; Wang, Yanfei; Wang, Benfeng

    2015-08-01

    Seismic interpolation, as an efficient strategy of providing reliable wavefields, belongs to large-scale computing problems. The rapid increase of data volume in high dimensional interpolation requires highly efficient methods to relieve computational burden. Most methods adopt the L1 norm as a sparsity constraint of solutions in some transformed domain; however, the L1 norm is non-differentiable and gradient-type methods cannot be applied directly. On the other hand, methods for unconstrained L1 norm optimisation always depend on the regularisation parameter which needs to be chosen carefully. In this paper, a fast gradient projection method for the smooth L1 problem is proposed based on the tight frame property of the curvelet transform that can overcome these shortcomings. Some smooth L1 norm functions are discussed and their properties are analysed, then the Huber function is chosen to replace the L1 norm. The novelty of the proposed method is that the tight frame property of the curvelet transform is utilised to improve the computational efficiency. Numerical experiments on synthetic and real data demonstrate the validity of the proposed method which can be used in large-scale computing.

  3. Curvilinear Grid Finite-Difference Method to Simulate Seismic Wave Propagation with Topographic Fluid-Solid Interface at Sea Bottom

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Zhang, W.; Chen, X.

    2014-12-01

    This paper presents a curvilinear grid finite difference method for modeling seismic wave propagation with topographic fluid (acoustic) and solid (elastic) interface. The curvilinear grid finite difference method has been successfully used for seismic wave simulation with free surface topography and earthquake dynamics with complex falut geometry. For seismic wave simulation with topographic sea bottom, we use the curvilinear grid to conform the grid to the sea bottom to avoid artifical scatterings due to stair-case approximation. We solve the acoustic wave equation in the water layer and the elastic wave equation in the solid below the sea bottom. The fluid-solid interface condition is implemented by decomposing velocity and stress components to normal and parallel directions of the sea bottom. The results exhibit high accuracy by comparsion with analytical solutions for flat interfaces and also work very well when the fluid-solid interface is topographic. The scheme can be easily extended to 3-D situation.

  4. A method to update fault transmissibility multipliers in the flow simulation model directly from 4D seismic

    NASA Astrophysics Data System (ADS)

    Benguigui, Amran; Yin, Zhen; MacBeth, Colin

    2014-04-01

    We propose a new approach to update fault seal estimates in fluid flow simulation models by direct use of 4D seismic amplitudes calibrated by a well geological constraint. The method is suited to compartmentalized reservoirs and based on metrics created from differences in the 4D seismic signature on either side of major faults. The effectiveness of the approach is demonstrated by application to data from the fault controlled Heidrun field in the Norwegian Sea. The results of this application appear favourable and show that our method can detect variations of fault permeability along the major controlling faults in the field. Updates of the field simulation model with the 4D seismic-derived transmissibilities are observed to decrease the mismatch between the predicted and historical field production data in the majority of wells in our sector of interest.

  5. Structure of the active rift zone and margins of the northern Imperial Valley from Salton Seismic Imaging Project (SSIP) data

    NASA Astrophysics Data System (ADS)

    Livers, A.; Han, L.; Delph, J. R.; White-Gaynor, A. L.; Petit, R.; Hole, J. A.; Stock, J. M.; Fuis, G. S.

    2012-12-01

    First-arrival refraction data were used to create a seismic velocity model of the upper crust across the actively rifting northern Imperial Valley and its margins. The densely sampled seismic refraction data were acquired by the Salton Seismic Imaging Project (SSIP) , which is investigating rift processes in the northern-most rift segment of the Gulf of California extensional province and earthquake hazards at the southern end of the San Andreas Fault system. A 95-km long seismic line was acquired across the northern Imperial Valley, through the Salton Sea geothermal field, parallel to the five Salton Butte volcanoes and perpendicular to the Brawley Seismic Zone and major strike-slip faults. Nineteen explosive shots were recorded with 100 m seismometer spacing across the valley and with 300-500 m spacing into the adjacent ranges. First-arrival travel times were picked from shot gathers along this line and a seismic velocity model was produced using tomographic inversion. Sedimentary basement and seismic basement in the valley are interpreted to be sediment metamorphosed by the very high heat flow. The velocity model shows that this basement to the west of the Brawley Seismic Zone is at ~4-km depth. The basement shallows to ~2-km depth in the active geothermal field and Salton Buttes volcanic field which locally coincide with the Brawley Seismic Zone. At the eastern edge of the geothermal field, the basement drops off again to ~3.5-km depth. The eastern edge of the valley appears to be fault bounded by the along-strike extension of the Sand Hills Fault, an inactive strike-slip fault. The seismic velocities to the east of the fault correspond to metamorphic rock of the Chocolate Mountains, different from the metamorphosed basement in the valley. The western edge of the valley appears to be fault bounded by the active Superstition Hills Fault. To the west of the valley, >4-km deep valley basement extends to the active Superstition Hills Fault. Basement then shallows

  6. Improved seismic risk estimation for Bucharest, based on multiple hazard scenarios, analytical methods and new techniques

    NASA Astrophysics Data System (ADS)

    Toma-Danila, Dragos; Florinela Manea, Elena; Ortanza Cioflan, Carmen

    2014-05-01

    a very local-dependent hazard. Also, for major earthquakes, nonlinear effects need to be considered. This problem is treated accordingly, by using recent microzonation studies, together with real data recorded at 4 events with Mw≥6. Different ground motion prediction equations are also analyzed, and improvement of them is investigated. For the buildings and population damage assessment, two open-source software are used and compared: SELENA and ELER. The damage probability for buildings is obtained through capacity-spectrum based methods. The spectral content is used for spectral acceleration at 0.2, 0.3 and 1 seconds. As the level of analysis (6 sectors for all the city) has not the best resolution with respect to the Bucharest hazard scenarios defined, we propose a procedure on how to divide the data into smaller units, taking into consideration the construction code (4 periods) and material. This approach relies on free data available from real estate agencies web-sites. The study provides an insight view on the seismic risk analysis for Bucharest and an improvement of the real-time emergency system. Most important, the system is also evaluated through real data and relevant scenarios. State-of-the art GIS maps are also presented, both for seismic hazard and risk.

  7. Variation in harbour porpoise activity in response to seismic survey noise.

    PubMed

    Pirotta, Enrico; Brookes, Kate L; Graham, Isla M; Thompson, Paul M

    2014-05-01

    Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency. PMID:24850891

  8. Variation in harbour porpoise activity in response to seismic survey noise

    PubMed Central

    Pirotta, Enrico; Brookes, Kate L.; Graham, Isla M.; Thompson, Paul M.

    2014-01-01

    Animals exposed to anthropogenic disturbance make trade-offs between perceived risk and the cost of leaving disturbed areas. Impact assessments tend to focus on overt behavioural responses leading to displacement, but trade-offs may also impact individual energy budgets through reduced foraging performance. Previous studies found no evidence for broad-scale displacement of harbour porpoises exposed to impulse noise from a 10 day two-dimensional seismic survey. Here, we used an array of passive acoustic loggers coupled with calibrated noise measurements to test whether the seismic survey influenced the activity patterns of porpoises remaining in the area. We showed that the probability of recording a buzz declined by 15% in the ensonified area and was positively related to distance from the source vessel. We also estimated received levels at the hydrophones and characterized the noise response curve. Our results demonstrate how environmental impact assessments can be developed to assess more subtle effects of noise disturbance on activity patterns and foraging efficiency. PMID:24850891

  9. Seismic protection of frame structures via semi-active control: modeling and implementation issues

    NASA Astrophysics Data System (ADS)

    Gattulli, Vincenzo; Lepidi, Marco; Potenza, Francesco

    2009-12-01

    Theoretical and practical issues concerning the multi-faceted task of mitigating the latero-torsional seismic response of a prototypal frame structure with asymmetric mass distribution are approached. Chevron braces with embedded magnetorheological dampers acting on the interstory drift are used to ensure additional energy dissipation. The semi-active control strategy employed to govern the modification of the damper characteristics via feedback is based on the selection of optimal forces according to a H2/LQG criterion, with respect to which the actual forces are regulated by a clipped-optimal logic. A dynamic observer is used to estimate the state through a non-collocated placement of the acceleration sensors. Several aspects to be addressed throughout the complex process including the design, modelization, and implementation phases of semi-active protection systems are discussed. Finally, experimental results obtained to mitigate the motion induced by ground excitation in a large-scale laboratory prototype, simulating the seismic response of a two-story building, are summarized.

  10. Possibilities for Observations of Electromagnetic Perturbations Related to Seismic Activity with Swarm Satellites

    NASA Astrophysics Data System (ADS)

    De Santis, A.; Mandea, M.; Balasis, G.

    2014-12-01

    It has been suggested that intense seismic activity might generate upward electromagnetic (EM) perturbations that can be detected by ground-based and low altitude spaceborne measurements. For instance, DEMETER satellite (2004-2010) very low frequency (VLF) wave observations pointed out a statistically significant decrease of the measured ionospheric wave intensity a few hours before large shallow earthquakes (EQs). This result would confirm the existence of a lithosphere-atmosphere-ionosphere coupling before the occurrence of an impending significant EQ. Swarm offers a great opportunity to study EM perturbations possibly related to seismic activity because it is a multi-satellite low Earth orbit (LEO) mission with a unique space-time configuration able to measure both electric and magnetic fields at various altitudes in the topside ionosphere. Here, we are analyzing, using various signal processing techniques, Swarm measurements shortly before and after large shallow EQs (magnitude above 7 and depth < 40 km) that occurred in the first year of the mission and report on the initial results of our analysis.

  11. Amplitude analysis of active source seismic data from the grounding zone of Whillans Ice Stream

    NASA Astrophysics Data System (ADS)

    Horgan, Huw; Anandakrishnan, Sridhar; Alley, Richard; Christianson, Knut

    2015-04-01

    Amplitude analysis of active source seismic data is often used to estimate acoustic properties and thereby infer the lithology of the substrate beneath glaciers and ice streams. The substrate beneath the ice streams of West Antarctica is of particular interest as here subglacial sediment deformation results in the rapid flow of the overriding ice. At the grounding zone, where the grounded ice sheet transitions to the floating ice shelf, this substrate is thought to stiffen due to tidal compaction resulting in a zone of higher basal shear stress which is manifest in the buckling of the internal layering in the overriding ice. Here we investigate these processes by estimating subglacial properties using active source seismic data acquired across the grounding zone of Whillans Ice Stream. Perhaps uniquely, we are able to test our methodology due to the survey crossing from an ice overlying sediment interface into a known ice overlying water interface. Our analysis indicates that lithological variations within the grounding zone are below the resolution of our methodology with the exception of a body of water trapped by a hydropotential reversal upstream of the grounding zone.

  12. Estimating activity-related energy expenditure under sedentary conditions using a tri-axial seismic accelerometer.

    PubMed

    van Hees, Vincent T; van Lummel, Rob C; Westerterp, Klaas R

    2009-06-01

    Activity-related energy expenditure (AEE) is difficult to quantify, especially under sedentary conditions. Here, a model was developed using the detected type of physical activity (PA) and movement intensity (MI), based on a tri-axial seismic accelerometer (DynaPort MiniMod; McRoberts B.V., The Hague, the Netherlands), with energy expenditure for PA as a reference. The relation between AEE (J/min/kg), MI, and the type of PA was determined for standardized PAs as performed in a laboratory including: lying, sitting, standing, and walking. AEE (J/min/kg) was calculated from total energy expenditure (TEE) and sleeping metabolic rate (SMR) as assessed with indirect calorimetry ((TEEx0.9)-SMR). Subsequently, the model was validated over 23-h intervals in a respiration chamber. Subjects were 15 healthy women (age: 22+/-2 years; BMI: 24.0+/-4.0 kg/m2). Predicted AEE in the chamber was significantly related to measured AEE both within (r2=0.81+/-0.06, P<0.00001) and between (r2=0.70, P<0.001) subjects. The explained variation in AEE by the model was higher than the explained variation by MI alone. This shows that a tri-axial seismic accelerometer is a valid tool for estimating AEE under sedentary conditions. PMID:19282829

  13. Long Term Seismic Observation in Mariana by OBSs : Activity of Deep Earthquakes

    NASA Astrophysics Data System (ADS)

    Shiobara, H.; Mochizuki, K.; Ohki, S.; Kanazawa, T.; Fukao, Y.; Sugioka, H.; Suyehiro, K.

    2003-12-01

    In order to obtain the deep arc structural image of Mariana, a large-scale seismic observation by using 58 long-term ocean bottom seismometers (LTOBS) has been started since June 2003 for about one year. It is a part of the MARGINS program (US-JAPAN COLLABORATIVE RESEARCH: MULTI-SCALE SEISMIC IMAGING OF THE MARIANA SUBDUCTION FACTORY), and the aim of this observation is the crustal and mantle structure modeling by using passive and active seismic sources. The 50 and 8 LTOBSs are owned by LDEO and ERI, respectively, and they were deployed during the cruise of R/V Kaiyo (Jamstec), KY03-06. Prior to this experiment, we made a pilot long-term seismic array observation in the same area by using 10 LTOBSs, deployed in Oct. 2001 by R/V Yokosuka (Jamstec) and recovered in Feb. 2003 by R/V Kaiyo. This LTOBS has been developed by ERI, which has the PMD sensor (WB2023LP) and a titanium sphere housing (D=50cm) and was already used in several long-term observations (ex. trans-PHS array observation presented at the AGU fall meeting, 2000, S51B-02). Two of 10 LTOBSs could not be recovered due to malfunction of the releasing system, and one recovered had a trouble in the sensor control unit. But, seven others have obtained more than 11 months long data continuously. As passive source studies of these observations use characteristic deep earthquakes in this area, the activity of them will be introduced in this presentation, from the data obtained just above them. At the first step, difference of hypocenters of known events, listed on the PDE catalog, is examined. There are 59 events of epicenters within a circular area centered at 19° N, 145° E with radius of 1000km from the catalog during the observation. P and S arrivals are picked by using the WIN system, and the iasp91 model (only {VP} with {{VP}/{V_S}=1.732}) is used for the hypocenter determination. Station corrections are applied only for the sediment layer, estimated from several arrival time data of P and P-S converted

  14. Near-surface Fun with Seismic Data

    NASA Astrophysics Data System (ADS)

    Clapp, M.

    2015-12-01

    What is happening in the near-surface often has a direct effect on human activity. Seismic exploration has routinely targeted geology at depths of kilometers to tens of kilometers. However, these techniques can be applied to answer questions about shallower targets. Several recent experiments demonstrate seismic applicability to near-surface problems. One example is passive seismic monitoring using ambient noise to identify shallow changes and potential hazards in a producing hydrocarbon field. Another example is the use of seismic reflection data from within the water column to determine layering caused by temperature and salinity differences in depth. A third example is identifying historical elevation changes along coast lines using seismic reflection data. These examples show that exploration seismic methods can be effectively used for a variety of near-surface applications.

  15. Prediction of Ground Vibration from Trains Using Seismic Reflectivity Methods for a Porous Soil

    NASA Astrophysics Data System (ADS)

    NELSON, J. T.

    2000-03-01

    Biot's model of wave propagation in porous isotropic materials is explored for predicting ground vibration from rail vehicles on vertically heterogeneous isotropic saturated soil and rock using seismic reflectivity methods combined with a multi-degree-of-freedom model of a transit vehicle bogie. A sketch of the mathematical theory, canonical results for step loads on a porous half-space, spectral responses for simple layer profiles, and an example of a prediction for rail transit vehicles are presented. The model indicates that saturation of the soil introduces excess attenuation in the vibration response of the soil, and that both pitch and roll moments in addition to vertical forces caused by the vehicle bogie may be significant sources of vibration.

  16. Validation needs of seismic probabilistic risk assessment (PRA) methods applied to nuclear power plants

    SciTech Connect

    Kot, C.A.; Srinivasan, M.G.; Hsieh, B.J.

    1985-01-01

    An effort to validate seismic PRA methods is in progress. The work concentrates on the validation of plant response and fragility estimates through the use of test data and information from actual earthquake experience. Validation needs have been identified in the areas of soil-structure interaction, structural response and capacity, and equipment fragility. Of particular concern is the adequacy of linear methodology to predict nonlinear behavior. While many questions can be resolved through the judicious use of dynamic test data, other aspects can only be validated by means of input and response measurements during actual earthquakes. A number of past, ongoing, and planned testing programs which can provide useful validation data have been identified, and validation approaches for specific problems are being formulated.

  17. A nearly analytic exponential time difference method for solving 2D seismic wave equations

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao; Yang, Dinghui; Song, Guojie

    2014-02-01

    In this paper, we propose a nearly analytic exponential time difference (NETD) method for solving the 2D acoustic and elastic wave equations. In this method, we use the nearly analytic discrete operator to approximate the high-order spatial differential operators and transform the seismic wave equations into semi-discrete ordinary differential equations (ODEs). Then, the converted ODE system is solved by the exponential time difference (ETD) method. We investigate the properties of NETD in detail, including the stability condition for 1-D and 2-D cases, the theoretical and relative errors, the numerical dispersion relation for the 2-D acoustic case, and the computational efficiency. In order to further validate the method, we apply it to simulating acoustic/elastic wave propagation in multilayer models which have strong contrasts and complex heterogeneous media, e.g., the SEG model and the Marmousi model. From our theoretical analyses and numerical results, the NETD can suppress numerical dispersion effectively by using the displacement and gradient to approximate the high-order spatial derivatives. In addition, because NETD is based on the structure of the Lie group method which preserves the quantitative properties of differential equations, it can achieve more accurate results than the classical methods.

  18. FM&TI (Forward Modeling & Tomographic Inversion) approach in passive and active seismic studies

    NASA Astrophysics Data System (ADS)

    Koulakov, Ivan

    2010-05-01

    Seismic tomography is like a photography taken by a camera with deformed and blurred lenses. Amplitudes and shapes of seismic patterns derived at tomographic images are often strongly biased with respect to real structures in the Earth. In particular, tomography usually provides continuous velocity distributions, while the major velocity changes in the Earth often occur on first order interfaces. While working with noisy data, one has to apply strong damping which makes impossible retrieving realistic amplitudes of anomalies. Uneven ray sampling may cause variable damping effect: within one model, one may obtain over- and underdamped solutions in different parts of the study area. Lack of some ray orientations may cause smearing of seismic patterns. Due to these and other reasons, quantitative values reported in most tomographic studies, although supported by pseudo-formal criteria (e.g. trade-off curves), do not often represent the reality. We propose an approach which is used to construct a realistic structure of the Earth based on a combination of forward modeling and tomographic inversion. Based on available a-priori information we construct a synthetic model with realistic patterns. Then we compute synthetic times and invert them using the same tomographic code with the same parameters as in the case of observed data processing. The reconstruction result is compared with the tomographic image of observed data inversion. For the parts where discrepancy is observed, we correct the synthetic model and repeat the forward modeling and inversion again. After several trials we obtain similar results of synthetic and observed data inversion. In this case we claim that the derived synthetic model adequately represents the real structure of the Earth. In the talk, several examples of applying this approach at various scales for different data schemes are presented: (1) few real and synthetic examples of active source refraction travel time data; (2) local earthquake

  19. Seismicity and active tectonic processes in the ultra-slow spreading Lena Trough, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Läderach, C.; Schlindwein, V.; Schenke, H.-W.; Jokat, W.

    2011-03-01

    With its remote location in the ice-covered Fram Strait, Lena Trough is a poorly known segment of the global mid-ocean ridge system. It is a prominent member of the ultra-slow spreading mid-ocean ridges but its spreading mechanisms are not well understood. We relocalized teleseismically recorded earthquakes from the past five decades to identify tectonic processes in Lena Trough and the adjacent Spitsbergen Fracture Zone (FZ). During two cruises with RV Polarstern in 2008 and 2009 we deployed seismic arrays on ice floes to record the local seismicity of Lena Trough. We could identify and localize microseismic events which we assume to be present in the entire rift valley. In contrast, our relocalization of teleseismically recorded earthquakes shows an asymmetric epicentre distribution along Lena Trough with earthquakes occurring predominately along the western valley flanks of Lena Trough. In 2009 February/March, several high-magnitude earthquakes peaking in an Mb 6.6 event occurred in an outside-corner setting of the Spitsbergen FZ. This is the strongest earthquake which has ever been recorded in Fram Strait and its location at the outside-corner high of the ultra-slow spreading ridge is exceptional. Comparing the seismicity with the magnetic anomalies and high-resolution multibeam bathymetry, we divide Lena Trough in a symmetrically spreading northern part and an asymmetrically spreading southern part south of the South Lena FZ. We propose that a complex interaction between the former De Geer Megashear zone, which separated Greenland from Svalbard starting at Late Mesozoic/Early Cenozoic times, and the developing rift in the southern Lena Trough resulted an increasing eastward dislocation towards the Spitsbergen FZ between older spreading axes and the recent active spreading axis which we believe to be located west of the bathymetric rift valley flanks in a wide extensional plain.

  20. Spatial distribution of intrinsic and scattering seismic attenuation in active volcanic islands - II: Deception Island images

    NASA Astrophysics Data System (ADS)

    Prudencio, Janire; Ibáñez, Jesús M.; García-Yeguas, Araceli; Del Pezzo, Edoardo; Posadas, Antonio M.

    2013-12-01

    In this work, we present regional maps of the inverse intrinsic quality factor (Qi-1), the inverse scattering quality factor (Qs-1) and total inverse quality factor (Qt-1) for the volcanic environment of Deception Island (Antarctica). Our attenuation study is based on diffusion approximation, which permits us to obtain the attenuation coefficients for every single couple source-receiver separately. The data set used in this research is derived from an active seismic experiment using more than 5200 offshore shots (air guns) recorded at 32 onshore seismic stations and four ocean bottom seismometers. To arrive at a regional distribution of these values, we used a new mapping technique based on a Gaussian space probability function. This approach led us to create `2-D probabilistic maps' of values of intrinsic and scattering seismic attenuation. The 2-D tomographic images confirm the existence of a high attenuation body below an inner bay of Deception Island. This structure, previously observed in 2-D and 3-D velocity tomography of the region, is associated with a massive magma reservoir. Magnetotelluric studies reach a similar interpretation of this strong anomaly. Additionally, we observed areas with lower attenuation effects that bear correlation with consolidated structures described in other studies and associated with the crystalline basement of the area. Our calculations of the transport mean-free path and absorption length for intrinsic attenuation gave respective values of ≈ 950 m and 5 km, which are lower than the values obtained in tectonic regions or volcanic areas such as Tenerife Island. However, as observed in other volcanic regions, our results indicate that scattering effects dominate strongly over the intrinsic attenuation.

  1. Geodynamics of the Dead Sea Fault: Do active faulting and past earthquakes determine the seismic gaps?

    NASA Astrophysics Data System (ADS)

    Meghraoui, Mustapha

    2014-05-01

    The ~1000-km-long North-South trending Dead Sea transform fault (DSF) presents structural discontinuities and includes segments that experienced large earthquakes (Mw>7) in historical times. The Wadi Araba and Jordan Valley, the Lebanese restraining bend, the Missyaf and Ghab fault segments in Syria and the Ziyaret Fault segment in Turkey display geometrical complexities made of step overs, restraining and releasing bends that may constitute major obstacles to earthquake rupture propagation. Using active tectonics, GPS measurements and paleoseismology we investigate the kinematics and long-term/short term slip rates along the DSF. Tectonic geomorphology with paleoseismic trenching and archeoseismic investigations indicate repeated faulting events and left-lateral slip rate ranging from 4 mm/yr in the southern fault section to 6 mm/yr in the northern fault section. Except for the northernmost DSF section, these estimates of fault slip rate are consistent with GPS measurements that show 4 to 5 mm/yr deformation rate across the plate boundary. However, recent GPS results showing ~2.5 mm/yr velocity rate of the northern DSF appears to be quite different than the ~6 mm/yr paleoseismic slip rate. The kinematic modeling that combines GPS and seismotectonic results implies a complex geodynamic pattern where the DSF transforms the Cyprus arc subduction zone into transpressive tectonics on the East Anatolian fault. The timing of past earthquake ruptures shows the occurrence of seismic sequences and a southward migration of large earthquakes, with the existence of major seismic gaps along strike. In this paper, we discuss the role of the DSF in the regional geodynamics and its implication on the identification of seismic gaps.

  2. Seismicity on the western Greenland Ice Sheet: Surface fracture in the vicinity of active moulins

    DOE PAGESBeta

    Carmichael, Joshua D.; Joughin, Ian; Behn, Mark D.; Das, Sarah; King, Matt A.; Stevens, Laura; Lizarralde, Dan

    2015-06-25

    We analyzed geophone and GPS measurements collected within the ablation zone of the western Greenland Ice Sheet during a ~35 day period of the 2011 melt season to study changes in ice deformation before, during, and after a supraglacial lake drainage event. During rapid lake drainage, ice flow speeds increased to ~400% of winter values, and icequake activity peaked. At times >7 days after drainage, this seismicity developed variability over both diurnal and longer periods (~10 days), while coincident ice speeds fell to ~150% of winter values and showed nightly peaks in spatial variability. Approximately 95% of all detected seismicitymore » in the lake basin and its immediate vicinity was triggered by fracture propagation within near-surface ice (<330 m deep) that generated Rayleigh waves. Icequakes occurring before and during drainage frequently were collocated with the down flow (west) end of the primary hydrofracture through which the lake drained but shifted farther west and outside the lake basin after the drainage. We interpret these results to reveal vertical hydrofracture opening and local uplift during the drainage, followed by enhanced seismicity and ice flow on the downstream side of the lake basin. This region collocates with interferometric synthetic aperture radar-measured speedup in previous years and could reflect the migration path of the meltwater supplied to the bed by the lake. The diurnal seismic signal can be associated with nightly reductions in surface melt input that increase effective basal pressure and traction, thereby promoting elevated strain in the surficial ice.« less

  3. An adaptive subspace trust-region method for frequency-domain seismic full waveform inversion

    NASA Astrophysics Data System (ADS)

    Zhang, Huan; Li, Xiaofan; Song, Hanjie; Liu, Shaolin

    2015-05-01

    Full waveform inversion is currently considered as a promising seismic imaging method to obtain high-resolution and quantitative images of the subsurface. It is a nonlinear ill-posed inverse problem, the main difficulty of which that prevents the full waveform inversion from widespread applying to real data is the sensitivity to incorrect initial models and noisy data. Local optimization theories including Newton's method and gradient method always lead the convergence to local minima, while global optimization algorithms such as simulated annealing are computationally costly. To confront this issue, in this paper we investigate the possibility of applying the trust-region method to the full waveform inversion problem. Different from line search methods, trust-region methods force the new trial step within a certain neighborhood of the current iterate point. Theoretically, the trust-region methods are reliable and robust, and they have very strong convergence properties. The capability of this inversion technique is tested with the synthetic Marmousi velocity model and the SEG/EAGE Salt model. Numerical examples demonstrate that the adaptive subspace trust-region method can provide solutions closer to the global minima compared to the conventional Approximate Hessian approach and the L-BFGS method with a higher convergence rate. In addition, the match between the inverted model and the true model is still excellent even when the initial model deviates far from the true model. Inversion results with noisy data also exhibit the remarkable capability of the adaptive subspace trust-region method for low signal-to-noise data inversions. Promising numerical results suggest this adaptive subspace trust-region method is suitable for full waveform inversion, as it has stronger convergence and higher convergence rate.

  4. Proceedings of seismic engineering 1991

    SciTech Connect

    Ware, A.G. )

    1991-01-01

    This book contains proceedings of the Seismic Engineering Technical Subcommittee of the ASME Pressure Vessels and Piping Division. Topics covered include: seismic damping and energy absorption, advanced seismic analysis methods, new analysis techniques and applications of advanced methods, seismic supports and test results, margins inherent in the current design methods, and risk assessment, and component and equipment qualification.

  5. Imaging Seismic Source Variations Using Back-Projection Methods at El Tatio Geyser Field, Northern Chile

    NASA Astrophysics Data System (ADS)

    Kelly, C. L.; Lawrence, J. F.

    2014-12-01

    During October 2012, 51 geophones and 6 broadband seismometers were deployed in an ~50x50m region surrounding a periodically erupting columnar geyser in the El Tatio Geyser Field, Chile. The dense array served as the seismic framework for a collaborative project to study the mechanics of complex hydrothermal systems. Contemporaneously, complementary geophysical measurements (including down-hole temperature and pressure, discharge rates, thermal imaging, water chemistry, and video) were also collected. Located on the western flanks of the Andes Mountains at an elevation of 4200m, El Tatio is the third largest geyser field in the world. Its non-pristine condition makes it an ideal location to perform minutely invasive geophysical studies. The El Jefe Geyser was chosen for its easily accessible conduit and extremely periodic eruption cycle (~120s). During approximately 2 weeks of continuous recording, we recorded ~2500 nighttime eruptions which lack cultural noise from tourism. With ample data, we aim to study how the source varies spatially and temporally during each phase of the geyser's eruption cycle. We are developing a new back-projection processing technique to improve source imaging for diffuse signals. Our method was previously applied to the Sierra Negra Volcano system, which also exhibits repeating harmonic and diffuse seismic sources. We back-project correlated seismic signals from the receivers back to their sources, assuming linear source to receiver paths and a known velocity model (obtained from ambient noise tomography). We apply polarization filters to isolate individual and concurrent geyser energy associated with P and S phases. We generate 4D, time-lapsed images of the geyser source field that illustrate how the source distribution changes through the eruption cycle. We compare images for pre-eruption, co-eruption, post-eruption and quiescent periods. We use our images to assess eruption mechanics in the system (i.e. top-down vs. bottom-up) and

  6. Assessing Acoustic Sound Levels Associated with Active Source Seismic Surveys in Shallow Marine Environments

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, D. R.; Tolstoy, M.; Thode, A.; Diebold, J. B.; Webb, S. C.

    2004-12-01

    The potential effect of active source seismic research on marine mammal populations is a topic of increasing concern, and controversy surrounding such operations has begun to impact the planning and permitting of academic surveys [e.g., Malakoff, 2002 Science]. Although no causal relationship between marine mammal strandings and seismic exploration has been proven, any circumstantial evidence must be thoroughly investigated. A 2002 stranding of two beaked whales in the Gulf of California within 50 km of a R/V Ewing seismic survey has been a subject of concern for both marine seismologists and environmentalists. In order to better understand possible received levels for whales in the vicinity of these operations, modeling is combined with ground-truth calibration measurements. A wide-angle parabolic equation model, which is capable of including shear within the sediment and basement layers, is used to generate predictive models of low-frequency transmission loss within the Gulf of California. This work incorporates range-dependent bathymetry, sediment thickness, sound velocity structure and sub-bottom properties. Oceanic sounds speed profiles are derived from the U.S. Navy's seasonal GDEM model and sediment thicknesses are taken from NOAA's worldwide database. The spectral content of the Ewing's 20-airgun seismic array is constrained by field calibration in the spring of 2003 [Tolstoy et al., 2004 GRL], indicating peak energies at frequencies below a few hundred Hz, with energy spectral density showing an approximate power-law decrease at higher frequencies (being ~40 dB below peak at 1 kHz). Transmission loss is estimated along a series of radials extending from multiple positions along the ship's track, with the directivity of the array accounted for by phase-shifting point sources that are scaled by the cube root of the individual airgun volumes. This allows the time-space history of low-frequency received levels to be reconstructed within the Gulf of California

  7. Seismic Activity in Northern Izu-Bonin arc by Ocean Bottom Seismograph Observations

    NASA Astrophysics Data System (ADS)

    Obana, K.; Kamiya, S.; Kodaira, S.; Suetsugu, D.; Takahashi, N.; Sakaguchi, H.

    2006-12-01

    The Izu-Bonin Island arc is an oceanic island arc, where the Pacific plate subducts beneath the Philippine Sea plate. Suyehiro et al. (1996) found a thick andesitic middle crust with velocity of 6 km/s in northern Izu arc. Recent active seismic experiments in the Izu-Bonin arc show significant variations of the thickness of the middle crust along the volcanic front (Kodaira et al, 2005). The thickness of the middle crust shows an inverse correlation with the average P-wave crustal velocity and the SiO2 composition of the Quaternary volcanoes along the arc. Crustal evolution in the oceanic island arc is a process including magma evolution in the mantle wedge. To understand the nature of the crustal evolution in the oceanic island arc, we have to clarify structures in the mantle wedge along the arc in addition to the oceanic island arc crust. We conducted seismicity observations by a temporal ocean bottom seismograph (OBS) network in northern Izu-Bonin arc between Tori-shima and Hachijo-jima (30° to 34°N) to investigate structures of the oceanic island arc crust and the mantle wedge in northern Izu-Bonin arc by seismic tomography. The OBS network consists of 40 pop-up type OBSs with a three-component short-period seismometer. The OBSs were deployed in April 2006 and retrieved in July after about 80-day observations. The OBS data were processed with seismic data recorded at island stations on Hachijo-jima and Aoga-shima. These island stations are operated by National Research Institute for Earth Science and Disaster Prevention. From the preliminary results of the hypocenters, many earthquakes were located along the subducting Pacific plate. Along the volcanic front, shallow earthquake clusters were observed around Tori-shima and Sumisu-Jima islands. Another shallow earthquake cluster was observed near a seamount of echelon chains in the back-arc region of the Izu-Bonin arc. Earthquakes in the fore-arc region show strong attenuation at OBSs in the back-arc region

  8. Shallow Seismic Reflection Study of Recently Active Fault Scarps, Mina Deflection, Western Nevada

    NASA Astrophysics Data System (ADS)

    Black, R. A.; Christie, M.; Tsoflias, G. P.; Stockli, D. F.

    2006-12-01

    During the spring and summer of 2006 University of Kansas geophysics students and faculty acquired shallow, high resolution seismic reflection data over actively deforming alluvial fans developing across the Emmigrant Peak (in Fish Lake Valley) and Queen Valley Faults in western Nevada. These normal faults represent a portion of the transition from the right-lateral deformation associated with the Walker Lane/Eastern California Shear Zone to the normal and left-lateral faulting of the Mina Deflection. Data were gathered over areas of recent high resolution geological mapping and limited trenching by KU students. An extensive GPR data grid was also acquired. The GPR results are reported in Christie, et al., 2006. The seismic data gathered in the spring included both walkaway tests and a short CMP test line. These data indicated that a very near-surface P-wave to S-wave conversion was taking place and that very high quality S-wave reflections were probably dominating shot records to over one second in time. CMP lines acquired during the summer utilized a 144 channel networked Geode system, single 28 hz geophones, and a 30.06 downhole rifle source. Receiver spacing was 0.5 m, source spacing 1.0m and CMP bin spacings were 0.25m for all lines. Surveying was performed using an RTK system which was also used to develop a concurrent high resolution DEM. A dip line of over 400m and a strike line over 100m in length were shot across the active fan scarp in Fish Lake Valley. Data processing is still underway. However, preliminary interpretation of common-offset gathers and brute stacks indicates very complex faulting and detailed stratigraphic information to depths of over 125m. Depth of information was actually limited by the 1024ms recording time. Several west-dipping normal faults downstep towards the basin. East-dipping antithetic normal faulting is extensive. Several distinctive stratigraphic packages are bound by the faults and apparent unconformitites. A CMP dip line

  9. Crosswell CASSM(Continuous Active-Source Seismic Monitoring): Recent Developments (Invited)

    NASA Astrophysics Data System (ADS)

    Daley, T. M.; Niu, F.; Ajo Franklin, J. B.; Solbau, R.; Silver, P. G.

    2009-12-01

    Continuous active-source monitoring using borehole sources and sensors in a crosswell configuration has proven to be a useful tool for monitoring subsurface processes (Silver, et al, 2007; Daley, et al, 2007; Niu, et al, 2008). This recent work has focused on two applications: monitoring stress changes related to seismicity and monitoring changes in fluid distribution related to geologic storage of CO2. Field tests have demonstrated precision in travel time measurement of up to 1.1 x 10-7 s, and in velocity perturbation measurement of up to 1.1 x 10-5 (Niu, et al 2008). In this talk I will summarize our preceding work and discuss current developments. Current efforts address both hardware and design challenges to improving the methodology. Hardware issues include deployment of multiple piezoelectric sources in shallow and deep boreholes, source and sensor deployment on tubing inside casing, and deployment with other monitoring instrumentation. Design issues are focused on use of multiple sources and/or sensors to obtain optimal spatial resolution for monitoring processes in the interwell region. This design issue can be investigated with optimal experiment design theory. New field experiments for monitoring seismicity (at SAFOD) and CO2 injection (at a US Dept of Energy pilot) are in the design/deployment stage. Current status of these projects will be discussed. References: Silver, P.G., Daley, T.M., Niu, F., Majer, E.L., 2007, Active source monitoring of crosswell seismic travel time for stress induced changes, Bulletin of Seismological Society of America, v97, n1B, p281-293. Daley, T.M., R.D. Solbau, J.B. Ajo-Franklin, S.M. Benson, 2007, Continuous active-source monitoring of CO2 injection in a brine aquifer, Geophysics, v72, n5, pA57-A61, DOI:10.1190/1.2754716. Niu, F., Silver, P.G., Daley, T.M., Cheng, X., Majer, E.L., 2008, Preseismic velocity changes observed from active source monitoring at the Parkfield SAFOD drill site, Nature, 454, 204-208, DOI:10

  10. High resolution seismic imaging of an active normal fault in the Agri Valley, Southern Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Improta, L.; Bruno, P.; di Fiore, V.; Mariani, S.

    2004-12-01

    The Agri Valley is an intermontane basin located in the Southern Apennine seismic belt (Italy) whose formation in tied to large NW-trending trastensional and extensional faults active since Early Pleistocene. Recent faulting activity in the area is documented by faulted paleosoils and suggested by a M7 earthquake that struck the basin in 1857. On the contrary, present-day background seismicity in the area is extremely low. Despite intense geomorphic investigations, the identification of the source responsible for this historical event and of further large seismogenic faults in the area is still a matter of debate. A new NW trending normal faulting system has been recently recognized based on subtle geomorphic expressions on the ridge bounding the basin westward. Recent faulting activity along this structure is locally documented by a trench. Aimed at yielding new information about the shallow structure of the fault, we conducted a high resolution seismic experiment in a small lacustrine basin, located 4 km south of the trench, in which the presence of the fault is inferred by a linear surface warping but trench excavation is impractical. Both multi-fold wide-angle data and multichannel near vertical reflection data have been collected along a 220-m-long profile in order to obtain an accurate model of the basin combining seismic velocity and reflectivity images. About 3600 first arrival traveltimes picked on 36 wide-angle record sections have been inverted by a non-linear tomographic technique that is specially designed to image complex structures. The tomographic inversion provides a high-resolution velocity model of the basin down to 60 m depth. The model is strongly heterogeneous and displays sharp lateral velocity variations. Seismic reflection processing has been applied to both data sets. Data have been edited for trace quality and first (refracted and direct) arrivals have been muted. A following FK dip filtering on the shot gathers reduced the energy

  11. Method for determining formation quality factor from well log data and its application to seismic reservoir characterization

    DOEpatents

    Walls, Joel; Taner, M. Turhan; Dvorkin, Jack

    2006-08-08

    A method for seismic characterization of subsurface Earth formations includes determining at least one of compressional velocity and shear velocity, and determining reservoir parameters of subsurface Earth formations, at least including density, from data obtained from a wellbore penetrating the formations. A quality factor for the subsurface formations is calculated from the velocity, the density and the water saturation. A synthetic seismogram is calculated from the calculated quality factor and from the velocity and density. The synthetic seismogram is compared to a seismic survey made in the vicinity of the wellbore. At least one parameter is adjusted. The synthetic seismogram is recalculated using the adjusted parameter, and the adjusting, recalculating and comparing are repeated until a difference between the synthetic seismogram and the seismic survey falls below a selected threshold.

  12. Coherence between geodetic and seismic deformation in a context of slow tectonic activity (SW Alps, France)

    NASA Astrophysics Data System (ADS)

    Walpersdorf, A.; Sue, C.; Baize, S.; Cotte, N.; Bascou, P.; Beauval, C.; Collard, P.; Daniel, G.; Dyer, H.; Grasso, J.-R.; Hautecoeur, O.; Helmstetter, A.; Hok, S.; Langlais, M.; Menard, G.; Mousavi, Z.; Ponton, F.; Rizza, M.; Rolland, L.; Souami, D.; Thirard, L.; Vaudey, P.; Voisin, C.; Martinod, J.

    2015-04-01

    A dense, local network of 30 geodetic markers covering a 50 × 60 km2 area in the southwestern European Alps (Briançon region) has been temporarily surveyed in 1996, 2006 and 2011 by GPS. The aim is to measure the current deformation in this seismically active area. The study zone is characterized by a majority of extensional and dextral focal mechanisms, along north-south to N160 oriented faults. The combined analysis of the three measurement campaigns over 15 years and up to 16 years of permanent GPS data from the French RENAG network now enables to assess horizontal velocities below 1 mm/year within the local network. The long observation interval and the redundancy of the dense campaign network measurement help to constrain a significant local deformation pattern in the Briançon region, yielding an average E-W extension of 16 ± 11 nanostrain/year. We compare the geodetic deformation field to the seismic deformation rate cumulated over 37 years, and obtain good coherencies both in amplitude and direction. Moreover, the horizontal deformation localized in the Briançon region represents a major part of the Adriatic-European relative plate motion. However, the average uplift of the network in an extensional setting needs the presence of buoyancy forces in addition to plate tectonics.

  13. Dating previously balanced rocks in seismically active parts of California and Nevada

    USGS Publications Warehouse

    Bell, J.W.; Brune, J.N.; Liu, T.; Zreda, M.; Yount, J.C.

    1998-01-01

    Precariously balanced boulders that could be knocked down by strong earthquake ground motion are found in some seismically active areas of southern California and Nevada. In this study we used two independent surface-exposure dating techniques - rock-varnish microlamination and cosmogenic 36Cl dating methodologies - to estimate minimum- and maximum-limiting ages, respectively, of the precarious boulders and by inference the elapsed time since the sites were shaken down. The results of the exposure dating indicate that all of the precarious rocks are >10.5 ka and that some may be significantly older. At Victorville and Jacumba, California, these results show that the precarious rocks have not been knocked down for at least 10.5 k.y., a conclusion in apparent conflict with some commonly used probabilistic seismic hazard maps. At Yucca Mountain, Nevada, the ages of the precarious rocks are >10.5 to >27.0 ka, providing an independent measure of the minimum time elapsed since faulting occurred on the Solitario Canyon fault.

  14. Tectonic history and thrust-fold deformation style of seismically active structures near Coalinga

    SciTech Connect

    Namson, J.S. ); Davis, T.L.; Lagoe, M.B.

    1990-01-01

    The stratigraphy of the Coalinga region can be divided into tectostratigraphic facies whose boundaries delineate two major tectonic events - one in the mid-Cenozoic (38-17 Ma) and one in the late Cenozoic (less than 3 Ma). The succession of these tectostratigraphic facies, and an integration of geology, subsurface well data, a seismic-reflection profile, and earthquake seismicity on a retrodeformable cross section, yield a model for the tectonic evolution of the Coalinga region. This model suggests that the structural style of both deformational events is characteristic of fold and thrust belts. The model also indicates that the causative fault of the May 2 earthquake is a ramped thrust. The results of this study, in combination with regional geologic relations, suggest that the Coalinga region is part of an active fold and thrust belt which borders the west and south sides of the San Joaquin Valley. The potential for future earthquakes due to movement of other blind thrust faults within this belt should be evaluated.

  15. Seismic activity and water level fluctuations in the artificial lakes of Aliakmonas river (NW Greece)

    NASA Astrophysics Data System (ADS)

    Petrou, Panagiota; Chouliaras, Gerasimos; Drakatos, George

    2015-04-01

    The Public Power Corporation (PPC) of Greece has established four dammed reservoirs, downstream of each other on Aliakmonas River in North Western Greece (namely the artificial lakes of Ilarionas, Polyphyto, Sfikia and Asomata). In addition to the monitoring of the reservoir water levels the PPC has also installed a dense seismological network in the wider area. In this investigation the correlation between the local seismic activity and the water level fluctuations at the Ilarionas and Polyphyto reservoirs is studied. On October 25th, 1984, during the Asomata reservoir initial filling, a Ms=5.4 earthquake occurred in the region which was characterized by weak seismicity, until the strong earthquake of Ms=6.5 that occurred on May 13th, 1995, at a distance of 18 km from the southern edge of the Polyphyto reservoir. More recently, on July 2nd and 3rd, 2013, two moderate earthquakes (Ml=4.7 and Ml=4.6) occurred, almost a year after the filling of the Ilarionas reservoir in 2012. In addition to these events, fourteen earthquakes with magnitudes equal or greater to Ml=4 have also been detected in the wider area of the Aliakmonas reservoir.

  16. High-resolution seismic structure analysis of an active submarine mud volcano area off SW Taiwan

    NASA Astrophysics Data System (ADS)

    Lin, Hsiao-Shan; Hsu, Shu-Kun; Tsai, Wan-Lin; Tsai, Ching-Hui; Lin, Shin-Yi; Chen, Song-Chuen

    2015-04-01

    In order to better understand the subsurface structure related to an active mud volcano MV1 and to understand their relationship with gas hydrate/cold seep formation, we conducted deep-towed side-scan sonar (SSS), sub-bottom profiler (SBP), multibeam echo sounding (MBES), and multi-channel reflection seismic (MCS) surveys off SW Taiwan from 2009 to 2011. As shown in the high-resolution sub-bottom profiler and EK500 sonar data, the detailed structures reveal more gas seeps and gas flares in the study area. In addition, the survey profiles show several submarine landslides occurred near the thrust faults. Based on the MCS results, we can find that the MV1 is located on top of a mud diapiric structure. It indicates that the MV1 has the same source as the associated mud diapir. The blanking of the seismic signal may indicate the conduit for the upward migration of the gas (methane or CO2). Therefore, we suggest that the submarine mud volcano could be due to a deep source of mud compressed by the tectonic convergence. Fluids and argillaceous materials have thus migrated upward along structural faults and reach the seafloor. The gas-charged sediments or gas seeps in sediments thus make the seafloor instable and may trigger submarine landslides.

  17. Improving the seismic imaging in the southern Ryukyu subduction system by using multiple attenuation methods

    NASA Astrophysics Data System (ADS)

    Lyu, Ci-Jhu; Kuo-Chen, Hao; McIntosh, Kirk; Wu, Francis; Liu, Char-Shine

    2015-04-01

    The southern Ryukyu subduction system is at the boundary where the Philippine sea plate subducts northwestward beneath the Eurasian plate near the Taiwan orogen. In previous studies, the boundary where the PSP subducts northward beneath the EP have no clear answers due to a lack of high-resolution crustal-scale geophysical constraints. We want to know the Moho boundary. We analyze in this study the dynamics of SRA system with TAIGER program of 2009, multi-channel marine seismic reflection (MGL0906_23, MGL0906_28, MGL0906_26A, MGL0906_13, MGL0906_18N). Data area covers about 30,000 km2. Shots are spaced every 50 m, hydrophones are spaced every 12.5 m, and CDP spacing is 6.25 m. Recording length is 15 s. Signal of the source is low frequencies (20Hz~60Hz), which can penetrate the shallow sediments and reflex signal of the deep crust. Because multiple can affect the deep structure signals. Therefore, we use a variety of methods to remove multiple effects, and increase Moho signals. In this study, we use four ways to remove the multiple. (1) Increases CDP spacing. (2)Deconvolution. (3) Surface Related Multiple Elimination (SRME). (4)Radon Transform multiple attenuation. From the TAIGER marine reflection data. The shallow structure are Huatung Basin, Yeyama Accretionary Prism, Forearc Basin and Ryukyu Arc (from south to north), respectively. We discover a lot of transform fault zone, and account these stress related with shear zone of Ryukyu subduction system. The deep structure, the crust of PSP velocity is about 5~7 km/s, the PSP Moho velocity is 7.5 km/s. In multichannel reflection seismic, the PSP Moho deep is about 15~20 km under the seabed. Keywords: multiple; Moho boundary; subduction zone; southern Ryukyu Arc (SRA)

  18. Late Quaternary Activity on the Cerro Goden Fault, Puerto Rico and Limitations of High-resolution Seismic Reflection/refraction Data for Trench-scale Investigations

    NASA Astrophysics Data System (ADS)

    Zachariasen, J.; Prentice, C. S.; Schweig, E.; Abreu, R.; Rymer, M. J.; Catchings, R. D.

    2005-12-01

    The Cerro Goden Fault runs along the base of the La Cadena de San Francisco range north of Añasco in western Puerto Rico, and joins with the Great Southern Puerto Rico Fault zone. This fault zone disrupts Eocene and older rocks but its Quaternary history is unclear. It bounds the northern Añasco Valley, which is seismically active. Offshore investigations suggest the fault cuts the sea floor (Grindlay et al., 2005) and an onshore reconnaissance study by Mann et al. (2005) found geomorphic evidence of Quaternary displacement. We gathered high-resolution seismic reflection/refraction data along two lines that crossed the projection of the fault in the Añasco Valley to help identify possible fault strands in the near subsurface. The seismic data were gathered using a shoot-through acquisition method with a BETSY-Seisgun shooting source consisting of 8-gauge, 400 grain shotgun blanks set in holes drilled about 30 cm below the ground surface. Both lines had shot and geophone spacings of 5 m. Common Depth Point (CDP) spacings for both lines were 2.5 m in the shallow section of the profiles. We used the results from the seismic lines to site six trenches where the data revealed discontinuities, possibly attributable to faulting, within the upper 2-3 meters. Our trenches ranged in depth from 2 - 5 meters, but in none of the trenches did we find evidence of surface faulting. A mountain-front-facing subsurface scarp, which may have been produced by older Quaternary faulting, appeared in several trenches. Holocene fluvial sediments have been deposited against this scarp and have buried it, but are unfaulted. Our results suggest either that the Cerro Goden Fault has not been active since the deposition of the Holocene fluvial sediments or that the high-resolution seismic data were not adequate to define the location of fault traces to the precision necessary for trench investigations. Both the seismic data and the buried scarps suggest there may be faults at depth, but

  19. Seismic Attenuation in the Rupture Zone of the 2010 Maule, Chile, Earthquake: Two Spectral Ratio Methods

    NASA Astrophysics Data System (ADS)

    Torpey, M.; Russo, R. M.; Beck, S. L.; Meltzer, A.; Roecker, S. W.

    2013-12-01

    We used data from the IRIS CHAMP temporary seismic network, deployed for 6 months following the February 2010 Mw 8.8 Maule earthquake, to estimate differential attenuation of P and S waves in the Maule rupture zone, 33°S - 38°S. We used two complementary spectral ratio methods both of which assume identical source-to-station travel paths which allowed us to neglect the source-time function and instrument response of each P-S phase pair. The first method iteratively determines 400 individual Qs values and uncertainties for each phase pair and the second method stacks the spectra of each of the 400 measurements to yield a composite spectrum from which we derive a single Qs. Measurements are deemed acceptable when the two methods agree. We examined 235 local events yielding a total of 1083 Qs measurements.The majority of ray paths evaluated show low Qs values (100-400) with an average Qs over the entire rupture zone of 350 and an average standard deviation of +/- 569. We are evaluating spatial and temporal variability in Qs; however, from our preliminary measurements we do not observe a temporal variability in Qs throughout the rupture zone nor do we recognize any consistent spatial pattern in the measurements. Tomographic inversion of the Qs measurements made along ray paths spanning the upper mantle wedge and South American crust above the Maule rupture region will allow us to interpret the observed Qs variability.

  20. Feasibility of using a seismic surface wave method to study seasonal and weather effects on shallow surface soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of the paper is to study the temporal variations of the subsurface soil properties due to seasonal and weather effects using a combination of a new seismic surface method and an existing acoustic probe system. A laser Doppler vibrometer (LDV) based multi-channel analysis of surface wav...

  1. On dependence of seismic activity on 11 year variations in solar activity and/or cosmic rays

    NASA Astrophysics Data System (ADS)

    Zhantayev, Zhumabek; Khachikyan, Galina; Breusov, Nikolay

    2014-05-01

    It is found in the last decades that seismic activity of the Earth has a tendency to increase with decreasing solar activity (increasing cosmic rays). A good example of this effect may be the growing number of catastrophic earthquakes in the recent rather long solar minimum. Such results support idea on existence a solar-lithosphere relationship which, no doubts, is a part of total pattern of solar-terrestrial relationships. The physical mechanism of solar-terrestrial relationships is not developed yet. It is believed at present that one of the main contenders for such mechanism may be the global electric circuit (GEC) - vertical current loops, piercing and electrodynamically coupling all geospheres. It is also believed, that the upper boundary of the GEC is located at the magnetopause, where magnetic field of the solar wind reconnects with the geomagnetic field, that results in penetrating solar wind energy into the earth's environment. The effectiveness of the GEC operation depends on intensity of cosmic rays (CR), which ionize the air in the middle atmosphere and provide its conductivity. In connection with the foregoing, it can be expected: i) quantitatively, an increasing seismic activity from solar maximum to solar minimum may be in the same range as increasing CR flux; and ii) in those regions of the globe, where the crust is shipped by the magnetic field lines with number L= ~ 2.0, which are populated by anomalous cosmic rays (ACR), the relationship of seismic activity with variations in solar activity will be manifested most clearly, since there is a pronounced dependence of ACR on solar activity variations. Checking an assumption (i) with data of the global seismological catalog of the NEIC, USGS for 1973-2010, it was found that yearly number of earthquake with magnitude M≥4.5 varies into the 11 year solar cycle in a quantitative range of about 7-8% increasing to solar minimum, that qualitatively and quantitatively as well is in agreement with the

  2. Spatial heterogeneities of deviatoric stress and pore-pressure in Kyushu, Japan, and their implication for seismic activity

    NASA Astrophysics Data System (ADS)

    Matsumoto, Satoshi; Chikura, Hiromi; Ohkura, Takahiro; Miyazaki, Masahiro; Shimizu, Hiroshi; Abe, Yuki; Inoue, Hiroyuki; Yoshikawa, Shin; Yamashita, Yusuke

    2013-04-01

    We investigated the spatial variation in stress fields and pore fluid pressures on Kyushu Island, southwestern Japan. High seismic activity is found not only along active faults in Kyushu Island (southwestern Japan) but also in the central area of the island where there are active volcanoes. We consider the focal mechanisms of the shallow earthquakes on Kyushu Island to determine the relative deviatoric stress field and pore fluid factor. Generally, the stress field corresponds to a strike slip regime in this area. A decline in the maximum principal compressional stress is found in the western part of the high seismicity area, in the middle of Kyushu Island; this may be caused by a thickening of the seismogenic zone, as estimated from D90 analysis. At thin seismogenic layer, strike slip faulting dominates and strain rate from GPS study is high. In the active fault zone, seismic activity along the fault is high, and the pore pressure within the zone is higher than the values observed elsewhere, suggesting a mechanism explained by the fault valve model of Sibson [1992]. The pore pressure in the high seismic area with scattered hypocenter distribution in the middle part is lower than that in the active fault zones.

  3. Seismic calm predictors of rockburst

    NASA Astrophysics Data System (ADS)

    Zmushko, Tatjana; Turuntaev, Sergey; Kulikov, Vladimir

    2013-04-01

    The method of "seismic calm" is widely used for forecasting of strong natural earthquakes (Sobolev G.A., Ponomarev A.V., 2003). The "seismic calm" means that during some time period before the main earthquake, the smaller events (with energies of several order smaller than that of the main earthquake) don't occur. In the presented paper the applicability of the method based on the idea of seismic calm for forecasting rockburst is considered. Three deposits (with seismicity induced by mining) are analyzed: Tashtagol iron deposit (Altai, Russia), Vorkuta (North Ural, Russia) and Barentsburg (Spitsbergen, Norway) coalmines. Local seismic monitoring networks are installed on each of them. The catalogues of seismic events were processed and strong events (rockbursts) were studied (Vorkuta M=2,3; Barentsburg M=1,8; Tashtagol M=1,9÷2,2). All catalogues cover at least two years (Vorkuta - 2008-2011, Barentsburg - 2011-2012, Tashtagol - 2002-2012). It was found that the number of seismic events with magnitudes M=0,5÷1 decreased in a month before the main strong event at Vorkuta coalmines. This event was not directly related with coal mining, its epicenter was located aside of the area of coal mining. In Barentsburg mine the rockburst wasn't so strong as in Vorkuta. The number of events with energies M=0,5 decreased slightly before the rockburst, but not so obviously as in Vorkuta case. The seismic events with high energies occur often at Tashtagol iron deposit. Mining methods used there differ from the coal deposit mining. At coalmines the mining combine runs from edge to edge of the wall, cutting off the coal. The considered iron deposit is developed by a method of block blasting. Not all rockbursts occur immediately after the blasting, so, the problem of the rockburst prediction is important for mining safety. To find rockburst precursors it is necessary to separate the events occurred due to the block blasting from the seismic events due to relocation of stresses in

  4. U-series dating of co-seismic gypsum and submarine paleoseismology of active faults in Northern Chile (23°S)

    NASA Astrophysics Data System (ADS)

    Vargas, Gabriel; Palacios, Carlos; Reich, Martin; Luo, Shangde; Shen, Chuan-Chou; González, Gabriel; Wu, Yi-Chen

    2011-01-01

    The convergence of the Nazca and South American plates along the subduction margin of the central Andes results in large subduction earthquakes and tectonic activity along major fault systems. Despite its relevance, the paleoseismic record of this region is scarce, hampering our understanding about the relationship between the Andes building and earthquake occurrence. In this study, we used the U-series disequilibrium method to obtain absolute ages of paleoearthquake events associated with normal displacements along the active Mejillones and Salar del Carmen faults in the Coastal Range of the Atacama Desert of northern Chile. The 230Th- 234U disequilibrium ages in co-seismic gypsum salts sampled along the fault traces together with marine evidences indicate that earthquakes occurred at ca. 29.7 ± 1.7 ka, 11 ± 4 ka and 2.4 ± 0.8 ka. When coupled with paleoseismic marine and radiocarbon ( 14C) records in the nearby Mejillones Bay evidencing large dislocations along the Mejillones Fault, the geochronological dataset presented here is consistent with the notion that gypsum salts formed during large earthquakes as a result of co-seismic dilatancy pumping of saline waters along the major faults. Based on maximum observed cumulative vertical offsets in the studied faults, this phenomena could have occurred episodically at a rate in the order of 1:40 to 1:50 with respect to the very large subduction earthquakes during the latest Pleistocene-Holocene period. The results presented here reveal that the U-series disequilibrium method can be successfully applied to date the gypsum salts deposited along faults during seismic events, and therefore directly constrain the age of large paleoearthquakes in hyperarid and seismically active zones.

  5. Evolution of earthquake rupture potential along active faults, inferred from seismicity rates and size distributions

    NASA Astrophysics Data System (ADS)

    Tormann, Thessa; Wiemer, Stefan; Enescu, Bogdan; Woessner, Jochen

    2016-04-01

    One of the major unresolved questions in seismology is the evolution in time and space of the earthquake rupture potential and thus time-dependent hazard along active faults. What happens after a major event: is the potential for further large events reduced as predicted from elastic rebound, or increased as proposed by current-state short-term clustering models? How does the rupture potential distribute in space, i.e. does it reveal imprints of stress transfer? Based on the rich earthquake record from the Pacific Plate along the Japanese coastline we investigate what information on spatial distributions and temporal changes of a normalized rupture potential (NRP) for different magnitudes can be derived from time-varying, local statistical characteristics of well and frequently observed small-to-moderate seismicity. Seismicity records show strong spatio-temporal variability in both activity rates and size distribution. We analyze 18 years of seismicity, including the massive 2011 M9 Tohoku earthquake and its aftermath. We show that the size distribution of earthquakes has significantly changed before (increased fraction of larger magnitudes) and after that mainshock (increased fraction of smaller magnitudes), strongest in areas of highest coseismic slip. Remarkably, a rapid recovery of this effect is observed within only few years. We combine this significant temporal variability in earthquake size distributions with local activity rates and infer the evolution of NRP distributions. We study complex spatial patterns and how they evolve, and more detailed temporal characteristics in a simplified spatial selection, i.e. inside and outside the high slip zone of the M9 earthquake. We resolve an immediate and strong NRP increase for large events prior to the Tohoku event in the subsequent high slip patch and a very rapid decrease inside this high-stress-release area, coupled with a lasting increase of NRP in the immediate surroundings. Even in the center of the Tohoku

  6. Seismic surface-wave prospecting methods for sinkhole hazard assessment along the Dead Sea shoreline

    NASA Astrophysics Data System (ADS)

    Ezersky, M.; Bodet, L.; Al-Zoubi, A.; Camerlynck, C.; Dhemaied, A.; Galibert, P.-Y.; Keydar, S.

    2012-04-01

    The Dead Sea's coastal areas have been dramatically hit by sinkholes occurrences since around 1990 and there is an obvious potential for further collapse beneath main highways, agricultural lands and other populated places. The sinkhole hazard in this area threatens human lives and compromise future economic developments. The understanding of such phenomenon is consequently of great importance in the development of protective solutions. Several geological and geophysical studies tend to show that evaporite karsts, caused by slow salt dissolution, are linked to the mechanism of sinkhole formation along both Israel and Jordan shorelines. The continuous drop of the Dead Sea level, at a rate of 1m/yr during the past decade, is generally proposed as the main triggering factor. The water table lowering induces the desaturation of shallow sediments overlying buried cavities in 10 to 30 meters thick salt layers, at depths from 25 to 50 meters. Both the timing and location of sinkholes suggest that: (1) the salt weakens as result of increasing fresh water circulation, thus enhancing the karstification process; (2) sinkholes appear to be related to the decompaction of the sediments above karstified zones. The location, depth, thickness and weakening of salt layers along the Dead Sea shorelines, as well as the thickness and mechanical properties of the upper sedimentary deposits, are thus considered as controlling factors of this ongoing process. Pressure-wave seismic methods are typically used to study sinkhole developments in this area. P-wave refraction and reflection methods are very useful to delineate the salt layers and to determine the thickness of overlying sediments. But the knowledge of shear-wave velocities (Vs) should add valuable insights on their mechanical properties, more particularly when the groundwater level plays an important role in the process. However, from a practical point of view, the measurement of Vs remains delicate because of well-known shear

  7. Assessing earthquake source models using 3-D forward modelling of long-period seismic data: application to the SCARDEC method

    NASA Astrophysics Data System (ADS)

    Ferreira, Ana Mg; Vallee, Martin; Charlety, Jean

    2010-05-01

    Accurate earthquake point source parameters (e.g. seismic moment, depth and focal mechanism) provide key first-order information for detailed studies of the earthquake source process and for improved seismic and tsunami hazard evaluation. In order to objectively assess the quality of seismic source models, it is important to go beyond classical resolution checks. In particular, it is desirable to apply sophisticated modelling techniques to quantify inaccuracies due to simplified theoretical formulations and/or Earth structure employed to build the source models. Moreover, it is important to verify how well the models explain data not used in their construction. In this study we assess the quality of the SCARDEC method (see joint abstracts), which is a new automated technique that retrieves simultaneously the seismic moment, focal mechanism, depth and source time functions of large earthquakes. Because the SCARDEC method is based on body-wave deconvolution using ray methods in a 1D Earth model, we test how well SCARDEC source parameters explain long-period seismic data (surface waves and normal modes). We calculate theoretical seismograms using two forward modelling techniques (full ray theory and spectral element method) to simulate the long-period seismic wavefield for the 3D Earth model S20RTS combined with the crust model CRUST2.0, and for two point source models: (i) the SCARDEC model; and (ii) the Global CMT model. We compare the synthetic seismograms with real broadband data from the FDSN for the major subduction earthquakes of the last 20 years. We show that SCARDEC source parameters explain long-period surface waves as well as Global CMT solutions. This can be explained by the fact that most of the differences between SCARDEC and Global CMT solutions are linked to correlated variations of the seismic moment and dip of the earthquakes, and it is theoretically known that for shallow earthquakes it is difficult to accurately resolve these two parameters using

  8. A mixed-grid finite element method with PML absorbing boundary conditions for seismic wave modelling

    NASA Astrophysics Data System (ADS)

    Liu, Shaolin; Li, Xiaofan; Wang, Wenshuai; Liu, Youshan

    2014-10-01

    We have developed a mixed-grid finite element method (MGFEM) to simulate seismic wave propagation in 2D structurally complex media. This method divides the physical domain into two subdomains. One subdomain covering the major part of the physical domain is divided by regular quadrilateral elements, while the other subdomain uses triangular elements to correctly fit a rugged free surface topography. The local stiffness matrix of any quadrilateral element is identical and matrix-vector production is calculated using an element-by-element technique, which avoids assembling a huge global stiffness matrix. As only a few triangular elements exist in the subdomain containing the rugged free surface topography, the memory requirements for storing the assembled subdomain global stiffness matrix are significantly reduced. To eliminate artificial boundary reflections, the MGFEM is also implemented to solve the system equations of PML absorbing boundary conditions (PML ABC). The accuracy and efficiency of the MGFEM is tested in numerical experiments by comparing it with conventional methods, and numerical comparisons also indicate its tremendous ability to describe rugged surfaces.

  9. Correlation Between Radon Outgassing and Seismic Activity Along the Hayward Fault Near Berkeley, California

    NASA Astrophysics Data System (ADS)

    Holtmann-Rice, D.; Cuff, K.

    2003-12-01

    Results from previous studies indicate that radon concentration values are significantly higher over selected sections of the Hayward fault than adjacent areas. This phenomenon is believed to be attributed to the presence of abundant fractures in rock associated with the fault, which act as pathways for radon as it migrates from depth towards the earth?s surface. In an attempt to determine whether or not a relationship exists between seismicity along the fault, the production of microfractures, and emanation of radon, a radon outgassing monitoring study was conducted along an active section of the Hayward fault in Berkeley, California. The study was carried out by using an alphaMETER 611, which is a device capable of accurately measuring radon concentrations every 15 minutes. The alphaMETER was placed at the bottom of a sealed one meter deep well, in close proximity to a section of the Hayward fault located along the northwestern face of the Berkeley Hills. Once per week for several months data collected by the alphaMETER was downloaded into a laptop computer. Data from the alphaMETER was then compared with seismic data recorded by local seismometers to see if any correlation existed. A general correlation between variation in radon concentration and the occurrence of small earthquakes was found. Significant peaks in radon concentration were observed within an approximately one week period before the occurrence of small earthquakes. Concentration values then decreased dramatically just prior to and during periods when the earthquakes occurred. Such correlation is very similar to that recently observed in association with a magnitude five earthquake along the Anatolian Fault, reported by geoscientists working in Turkey using similar instrumentation (Inan, 2003, personal communication). The most plausible explanation for the observed correlation is as follows: 1) prior to a given earthquake, stress build up within a particular fault region leads to the formation of

  10. Grid-Search Location Methods for Ground-Truth Collection From Local and Regional Seismic Networks

    SciTech Connect

    William Rodi; Craig A. Schultz; Gardar Johannesson; Stephen C. Myers

    2005-05-13

    This project investigated new techniques for improving seismic event locations derived from regional and local networks. The technqiues include a new approach to empirical travel-time calibration that simultaneously fits data from multiple stations and events, using a generalization of the kriging method, and predicts travel-time corrections for arbitrary event-station paths. We combined this calibration approach with grid-search event location to produce a prototype new multiple-event location method that allows the use of spatially well-distributed events and takes into account correlations between the travel-time corrections from proximate event-station paths. Preliminary tests with a high quality data set from Nevada Test Site explosions indicated that our new calibration/location method offers improvement over the conventional multiple-event location methods now in common use, and is applicable to more general event-station geometries than the conventional methods. The tests were limited, however, and further research is needed to fully evaluate, and improve, the approach. Our project also demonstrated the importance of using a realistic model for observational errors in an event location procedure. We took the initial steps in developing a new error model based on mixture-of-Gaussians probability distributions, which possess the properties necessary to characterize the complex arrival time error processes that can occur when picking low signal-to-noise arrivals. We investigated various inference methods for fitting these distributions to observed travel-time residuals, including a Markov Chain Monte Carlo technique for computing Bayesian estimates of the distribution parameters.

  11. Semi-active seismic response control of base-isolated building with MR damper

    NASA Astrophysics Data System (ADS)

    Soda, Satsuya; Kusumoto, Haruhide; Chatani, Ryosuke; Iwata, Norio; Fujitani, Hideo; Shiozaki, Yoichi; Hiwatashi, Takeshi

    2003-07-01

    This study deals with a shake table test on a three-story base-isolated steel frame. The frame rests on four roller bearings for isolation and is equipped with four laminated rubbers as shear spring. An MR damper is used in the test to perform semi-active seismic response control. The basic control algorithm applied in the study is to simulate the load-deflection of an origin-restoring friction damper (ORFD) which is a sort of friction damper that looses its resistance when it moves toward the origin, making sure for the base-isolated system to minimize residual displacement even after an extremely strong ground motion. Also attempted is a hybrid type control that superposes viscous damping on the ORFD when the damper moves from the peak displacement toward the origin.

  12. A 3-D spectral-element and frequency-wave number hybrid method for high-resolution seismic array imaging

    NASA Astrophysics Data System (ADS)

    Tong, Ping; Komatitsch, Dimitri; Tseng, Tai-Lin; Hung, Shu-Huei; Chen, Chin-Wu; Basini, Piero; Liu, Qinya

    2014-10-01

    We present a three-dimensional (3-D) hybrid method that interfaces the spectral-element method (SEM) with the frequency-wave number (FK) technique to model the propagation of teleseismic plane waves beneath seismic arrays. The accuracy of the resulting 3-D SEM-FK hybrid method is benchmarked against semianalytical FK solutions for 1-D models. The accuracy of 2.5-D modeling based on 2-D SEM-FK hybrid method is also investigated through comparisons to this 3-D hybrid method. Synthetic examples for structural models of the Alaska subduction zone and the central Tibet crust show that this method is capable of accurately capturing interactions between incident plane waves and local heterogeneities. This hybrid method presents an essential tool for the receiver function and scattering imaging community to verify and further improve their techniques. These numerical examples also show the promising future of the 3-D SEM-FK hybrid method in high-resolution regional seismic imaging based on waveform inversions of converted/scattered waves recorded by seismic array.

  13. Quaternary grabens in southernmost Illinois: Deformation near an active intraplate seismic zone

    USGS Publications Warehouse

    Nelson, W.J.; Denny, F.B.; Follmer, L.R.; Masters, J.M.

    1999-01-01

    Narrow grabens displace Quaternary sediments near the northern edge of the Mississippi Embayment in extreme southern Illinois, east-central United States. Grabens are part of the Fluorspar Area Fault Complex (FAFC), which has been recurrently active throughout Phanerozoic time. The FAFC strikes directly toward the New Madrid Seismic Zone (NMSZ), scene of some of the largest intra-plate earthquakes in history. The NMSZ and FAFC share origin in a failed Cambrian rift (Reelfoot Rift). Every major fault zone of the FAFC in Illinois exhibits Quaternary displacement. The structures appear to be strike-slip pull-apart grabens, but the magnitude and direction of horizontal slip and their relationship to the current stress field are unknown. Upper Tertiary strata are vertically displaced more than 100 m, Illinoian and older Pleistocene strata 10 to 30 m, and Wisconsinan deposits 1 m or less. No Holocene deformation has been observed. Average vertical slip rates are estimated at 0.01 to 0.03 mm/year, and recurrence intervals for earthquakes of magnitude 6 to 7 are on the order of 10,000s of years for any given fault. Previous authors remarked that the small amount of surface deformation in the New Madrid area implies that the NMSZ is a young feature. Our findings show that tectonic activity has shifted around throughout the Quaternary in the central Mississippi Valley. In addition to the NMSZ and southern Illinois, the Wabash Valley (Illinois-Indiana), Benton Hills (Missouri), Crowley's Ridge (Arkansas-Missouri), and possibly other sites have experienced Quaternary tectonism. The NMSZ may be only the latest manifestation of seismicity in an intensely fractured intra-plate region.

  14. Active Source Tomography of Stromboli Volcano (Italy): Results From the 2006 Seismic Experiment.

    NASA Astrophysics Data System (ADS)

    Zuccarello, L.; Patanè, D.; Cocina, O.; Castellano, M.; Sgroi, T.; Favali, P.; de Gori, P.

    2008-12-01

    Stromboli island, located in the Southern Tyrrhenian sea, is the emerged part (about 900 m a.s.l.) of a 3km-high strato-volcano. Its persistent Strombolian activity, documented for over 2000 years, is sometimes interrupted by lava effusions or major explosions. Despite the amount of recent published geophysical studies aimed to clarifying eruption dynamics, the spatial extend and geometrical characteristics of the plumbing system remain poorly understood. In fact, the knowledge of the inner structure and the zones of magma storage is limited to the upper few hundreds meters of the volcanic edifice and P- and S-waves velocity models are available only in restricted areas. In order to obtain a more suitable internal structural and velocity models of the volcano, from 25 November to 2 December 2006, a seismic tomography experiment through active seismics using air-gun sources was carried out and the final Vp model is here presented. The data has been inverted for the Vp structure by using the code Simulps13q, considering a 3D grid of nodes spaced 0.5 km down to 2 km depth, beneath the central part of volcano. The results show a relatively high velocity zones located both in the inner part of the volcanic structure, at about 1km b.s.l. and in the last 200-300 m a.s.l. in correspondence with the volcanic conduit. Slower zones were located around the summit craters in agreement with volcanological and petrological informations for the area. The relatively high velocity zones could suggest the presence of intrusive bodies related to the plumbing system.

  15. Exhumed analogues of seismically active carbonate-bearing thrusts: fault architecture and deformation mechanisms

    NASA Astrophysics Data System (ADS)

    Tesei, T.; Collettini, C.; Viti, C.; Barchi, M. R.

    2012-12-01

    In May 2012 a M = 5.9 earthquake followed by a long aftershock sequence struck the Northern Italy. The sequence occurred at 4-10 km depth within the active front of Northern Apennines Prism and the major events nucleate within, or propagate through, a thick sequence of carbonates. In an inner sector of the Northern Apennines, ancient carbonate-bearing thrusts exposed at the surface, represent exhumed analogues of structures generating seismicity in the active front. Here we document fault architecture and deformation mechanisms of three regional carbonate bearing thrusts with displacement of several kilometers and exhumation in the range of 1-4 km. Fault zone structure and deformation mechanisms are controlled by the lithology of the faulted rocks. In layered limestones and marly-limestones the fault zone is up to 200 m thick and is characterized by intense pressure solution. In massive limestones the deformation generally occurs along thin and sharp slip planes that are in contact with fault portions affected by either cataclasis or pressure solution. SEM and TEM observations show that pressure solution surfaces, made of smectite lamellae, with time tend to form an interconnected network affected by frictional sliding. Sharp slipping planes along massive limestones show localization along Y shear planes that separate an extremely comminuted cataclasites from an almost undeformed protolith. The comparison of the three shear zones depicts a fault zone structure extremely heterogeneous as the result of protolith lithology, geometrical complexities and the presence of inherited structures. We observe the competition between brittle (cataclasis, distributed frictional sliding along phyllosilicates and extremely localized slip within carbonates) and pressure solution processes, that suggest a multi-mode of slip behaviour. Extreme localization along carbonate-bearing Y shear planes is our favorite fault zone feature representing past seismic ruptures along the studied

  16. Study on Seismic Zoning of Sino-Mongolia Arc Areas

    NASA Astrophysics Data System (ADS)

    Xu, G.

    2015-12-01

    According to the agreement of Cooperation on seismic zoning between Institute of Geophysics, China Earthquake Administration and Research Center of Astronomy and Geophysics, Mongolian Academy of Science, the data of geotectonics, active faults, seismicity and geophysical field were collected and analyzed, then field investigation proceeded for Bolnay Faults, Ar Hutul Faults and Gobi Altay Faults, and a uniform earthquake catalogue of Mongolia and North China were established for the seismic hazard study in Sino-Mongolia arc areas. Furthermore the active faults and epicenters were mapped and 2 seismic belts and their 54 potential seismic sources are determined. Based on the data and results above mentioned the seismicity parameters for the two seismic belts and their potential sources were studied. Finally, the seismic zoning with different probability in Sino-Mongolia arc areas was carried out using China probabilistic hazard analysis method. By analyzing the data and results, we draw the following main conclusions. Firstly, the origin of tectonic stress field in the study areas is the collision and pressure of the India Plate to Eurasian Plate, passing from the Qinghai-Tibet Plateau. This is the reason why the seismicity is higher in the west than in the east, and all of earthquakes with magnitude 8 or greater occurred in the west. Secondly, the determination of the 2 arc seismic belts, Altay seismic belt and Bolnay-Baikal seismic belt, are reasonable in terms of their geotectonic location, geodynamic origin and seismicity characteristics. Finally, there are some differences between our results and the Mongolia Intensity Zoning map published in 1985 in terms of shape of seismic zoning map, especially in the areas near Ulaanbaatar. We argue that our relsults are reasonable if we take into account the data use of recent study of active faults and their parameters, so it can be used as a reference for seismic design.

  17. Method for interpreting seismic records to yield indications of gas/oil in an earth formation

    SciTech Connect

    Thompson, D.; Brown, R.; Runge, R.

    1983-08-09

    The present invention indicates that acoustic characteristics associated with gas/oil-containing strata of an earth formation, including reflectivity coefficients can be normalized (and favorably compared) with similar characteristics calculated and displayed by means of a machine-implemented processing method in which well logging and geologic data are fed thereto to calculate such characteristics without the need for shearwave velocities. In more detail, in accordance with the invention brine-saturated bulk and shear moduli, (i.e., Kw and Gw) of the strata of interest can be predicted as a function of, say, brine-saturated P-wave modulus (Pw) alone (independent of shear-wave velocity). In that way, resulting acoustic values including seismic velocities and amplitudes (also, reflectivities) as a function of saturation can ultimately be provided. Such values, when compared to actual field-generated characteristics, are surprisingly accurate predictors of the amount of gas/oil saturation in the zone of interest. The method has particular applicability to designating gas-sand zones within formations of interest.

  18. On causes of the low seismic activity in the Earth's polar latitudes

    NASA Astrophysics Data System (ADS)

    Levin, Boris; Sasorova, Elena; Domanski, Andrei

    2016-04-01

    The irregularity of distribution of seismic activity in the world was observed at the beginning of the era of instrumental seismology (B. Gutenberg, C. Richter, K. Kasahara). At the same time, the global nature of the symmetry of this effect has been established only in this millennium, with the participation of authors (Levin B.W., Sasorova E.V., 2010). Analysis of the global earthquake catalogs showed that almost all seismic events over the last century occurred within a limited latitudinal band contained between the 65 N and 65 S. The seismic activity in the polar regions of the planet was manifested very weakly. The reasons for such features were found by following the analysis of the characteristics associated with the theory of the figure of the Earth. In the works of the French mathematician A. Veronne (1912) was the first to introduce the concept of "critical" latitudes (φ1 = ±35°15' 22″) wherein the radius of the ellipsoid of revolution is equal to the radius of the sphere of the same volume. Variation of the radius vector of the ellipsoid at this latitude is equal to zero. There is the boundary between the compressed areas of the polar zones and equatorial region, where the rocks of the Earth are dominated by tensile forces. Analysis of the specific characteristics of the gravity force distribution on the surface of the ellipsoid has shown that there is a distribution of the same character with a singular point at latitude φ2 = ±61° 52' 12″. In case of variations in the angular velocity of the planet's rotation the variation of gravity force at the latitude φ2 is negligible, compared with variations of gravity force on the equator and pole, which exceed the previous value by 3-4 orders. Attempted analysis of the model of the ellipsoid of revolution in the theory of axisymmetric elastic shells has allowed to establish that in the elastic shell of the planet must occur meridional and ring forces. The theory shows that when the flatness (or polar

  19. Periods of the Earth's seismicity activation and their relationship to variations in the Earth's rotation velocity

    NASA Astrophysics Data System (ADS)

    Sasorova, Elena; Levin, Boris

    2015-04-01

    It is known that Earth's seismic activity (SA) demonstrates distinct roughness (nonuniformity) in time. Periods of intensification of the SA followed by periods of its decaying. For strong earthquakes these periods are continued several decades. It was also noted that there is a pronounced periodic amplification and attenuation of the SA with a period of about 30 years, which is manifested mainly in two latitudinal belts 50°N-30°N and 0°-30°S [Levin, Sasorova, 2014, 2015]. This work deals with the hypothesis that it is the properties of rotating non-uniform rate of the planet may be the cause of the periodicity of manifestations SA. The objective of this work is the searching of the spatial-temporal interconnection between the Earth rotation irregularity and the observed cyclic increasing and decreasing of the Earth's SA. This requires preparation a long series of observations of seismic events with representative data sets (EQ selected from 1895 up to date with a magnitude M> = 7.5, based on the catalog NEIC). Two sources of data on the angular velocity of the Earth's rotation of (length of day, LOD) were adapted: the world-known database IERS (Annual Report, International Earth Rotation Service) and the data, which were presented in the work (McCarthy, D.D., and Babcock A.K., 1986). The first one contains daily observations from 1962 to 2013, the second one was identified semi-annual observations from 1720 to 1984. It was prepared concatenated data set (CLOD) for the period from 1720 to 2013. Characteristic periods in the time series CLOD: 62, 32, and 23 years have been isolated by the use of spectral analysis. Next, it were used a band-pass filters for the four frequency bands from 124 to 45 years, from 37 do 25 years, from 25 to 19 years, and in the range of less than 19 years. In the frequency bands 37-25 years and 25-19 years marked clear periodic oscillations close to a sine wave. The amplitude of the oscillations with the 1720 to 1790 gradually

  20. The ROBEX-ASN - A Concept Study for an active seismic Network on the Moon

    NASA Astrophysics Data System (ADS)

    Czeluschke, A.; Knapmeyer, M.; Sohl, F.; Bamberg, M.; Lange, C.; Luther, R.; Margonis, A.; Rosta, R.; Schmitz, N.; Robex Asn Study Team

    2014-04-01

    The Helmholtz Alliance "Robotic Exploration of Extreme Environments - ROBEX", brings together space and deep-sea researchers. The project partners are jointly developing technologies for the exploration of highly inaccessible terrains. The research on the Moon and in the deep sea would answer different scientific questions but should be addressed by a common method (seismic surveys) and technological solution. The overall goal is to develop a combination of a stationary system and one or more mobile elements. The stationary system would provide the energy supply and the possibility to exchange data between the elements and the ground station. The mobile elements will perform the actual scientific exploration in the deep sea or on the Moon. It is the overarching objective of the ROBEX Alliance is the equipment of these systems with innovative technologies for energy exchange and data transfer. Most processes should be conducted fully autonomously [4]. Science-critical decisions will be made semi-autonomously with Human-in-the Loop.

  1. Active tectonic data calling for the re-evaluation of the seismic hazard along the Vienna Basin Transform Fault

    NASA Astrophysics Data System (ADS)

    Decker, K.; Hinsch, R.; Peresson, H.; Wagreich, M.

    2003-04-01

    The Vienna Basin Transform Fault is a slow moving active fault passing through the most populated and most productive region of Austria with 2.4 million inhabitants producing c. 45% of the Austrian GDP. Active faulting in this highly vulnerable environment is accompanied by historically moderate seismicity (Imax ~ 8-9) in a narrow NE-striking zone paralleling the fault. Novel tectonic data such as maps of active faults and computed seismic slip deficits indicate that previous hazard analyses for the surrounding of Vienna may both underestimate the probability of severe earthquakes and the maximum credible earthquake. Slip rates of the fault in the Vienna Basin are derived from an actively subsiding pull-apart structure filled with up to 140 m Quaternary sediments. 1.5 to 2 km sinistral displacement, which accumulated during basin formation in the last 400 (?) ky corresponds to a slip rate of 1.6 - 2.5 mm/y. This is in good agreement with GPS data showing 2 mm slip per year and precise leveling proving surface subsidence up to 1 mm/y. The data, however, strongly contrast from slip rates computed from cumulative seismic moments of earthquakes. Seismic energy release only accounts for c. 0.2 mm/yr slip proving a seismic slip deficit for the historical time window of about 750 y. In addition, seismic slip calculations for arbitrarily selected fault sectors reveal large differences between the fastest (0.5 mm/yr) and slowest (0.02 mm/yr) seismically moving sector. We relate these to the locking of fault segments. Both results indicate that the seismic cycle exceeds the length of available seismological observation and larger earthquakes than those recorded need to be expected along the fault. Additional data to call for hazard re-evaluation come from the integration of subcrop data, Quaternary thickness, earthquake data, geophysical data (Gegenleitner et al., this vol.) and geomorphology, which results in a detailed map of active faults. The map depicts a major NE

  2. Installation of a digital, wireless, strong-motion network for monitoring seismic activity in a western Colorado coal mining region

    SciTech Connect

    Peter Swanson; Collin Stewart; Wendell Koontz

    2007-01-15

    A seismic monitoring network has recently been installed in the North Fork Valley coal mining region of western Colorado as part of a NIOSH mine safety technology transfer project with two longwall coal mine operators. Data recorded with this network will be used to characterize mining related and natural seismic activity in the vicinity of the mines and examine potential hazards due to ground shaking near critical structures such as impoundment dams, reservoirs, and steep slopes. Ten triaxial strong-motion accelerometers have been installed on the surface to form the core of a network that covers approximately 250 square kilometers (100 sq. miles) of rugged canyon-mesa terrain. Spread-spectrum radio networks are used to telemeter continuous streams of seismic waveform data to a central location where they are converted to IP data streams and ported to the Internet for processing, archiving, and analysis. 4 refs.

  3. Onshore-offshore seismic networks: an inescapable approach to reveal the crustal structure and the seismic activity of large subduction zones

    NASA Astrophysics Data System (ADS)

    Charvis, P.; Galve, A.; Laigle, M.; Hirn, A.; Hello, Y. M.; Oge, A.; Yates, B. A.

    2013-12-01

    Ninety percent of the seismic energy released worldwide and ninety percent of the largest earthquakes and tsunamis occur in subduction zones. Several recent catastrophic subduction earthquakes surprised us on many aspects, either because we had been unable to anticipate their extremely large magnitude (2011 Tohoku Earthquake, Mw 9.0), or because we had considered the subduction as partly aseismic (2004 Sumatra Andaman earthquake, Mw 9.1). One of the reasons for our present ignorance of the behavior of large subduction earthquakes is the lack of marine data to image and monitor the structure and evolution of megathrust faults offshore. Over the last 15 years, our group has conducted several passive and active seismic experiments* in the forearc regions of the Ecuador-Colombia, Lesser Antilles and Hellenic subduction zones. The objectives of these experiments were to image the subduction interplate fault at depth and accurately locate the current earthquake activity of the megathrusts using arrays of combined ocean-bottom and land-based seismometers. In the case of very large events and in the absence of geodetic data in the offshore part of the faults, the precise knowledge of current seismicity is mandatory to estimate the seismogenic behavior and potential of the fault interface. 2D dense active seismic lines, shot jointly with multichannel acquisitions, provide invaluable images of the deep structure of the Lesser Antilles arc and forearc, which allow locating the updip and downdip limits of the expected seismogenic zone. Assuming that the Moho is the downdip limit of the seismogenic zone, the 26 km-thick crust of the arc makes the seismogenic zone 3 times wider than it is in ';standard' oceanic arcs (like Marianas). 3D active and passive experiments in the Lesser Antilles and Ecuador forearcs provide an unprecedented way to image the structure in 3D down to the lower plate. The tomography documents the spatial variability of the interplate fault structure and of

  4. Multi-Parameter Observation and Detection of Pre-Earthquake Signals in Seismically Active Areas

    NASA Technical Reports Server (NTRS)

    Ouzounov, D.; Pulinets, S.; Parrot, M.; Liu, J. Y.; Hattori, K.; Kafatos, M.; Taylor, P.

    2012-01-01

    The recent large earthquakes (M9.0 Tohoku, 03/2011; M7.0 Haiti, 01/2010; M6.7 L Aquila, 04/2008; and M7.9 Wenchuan 05/2008) have renewed interest in pre-anomalous seismic signals associated with them. Recent workshops (DEMETER 2006, 2011 and VESTO 2009 ) have shown that there were precursory atmospheric /ionospheric signals observed in space prior to these events. Our initial results indicate that no single pre-earthquake observation (seismic, magnetic field, electric field, thermal infrared [TIR], or GPS/TEC) can provide a consistent and successful global scale early warning. This is most likely due to complexity and chaotic nature of earthquakes and the limitation in existing ground (temporal/spatial) and global satellite observations. In this study we analyze preseismic temporal and spatial variations (gas/radon counting rate, atmospheric temperature and humidity change, long-wave radiation transitions and ionospheric electron density/plasma variations) which we propose occur before the onset of major earthquakes:. We propose an Integrated Space -- Terrestrial Framework (ISTF), as a different approach for revealing pre-earthquake phenomena in seismically active areas. ISTF is a sensor web of a coordinated observation infrastructure employing multiple sensors that are distributed on one or more platforms; data from satellite sensors (Terra, Aqua, POES, DEMETER and others) and ground observations, e.g., Global Positioning System, Total Electron Content (GPS/TEC). As a theoretical guide we use the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model to explain the generation of multiple earthquake precursors. Using our methodology, we evaluated retrospectively the signals preceding the most devastated earthquakes during 2005-2011. We observed a correlation between both atmospheric and ionospheric anomalies preceding most of these earthquakes. The second phase of our validation include systematic retrospective analysis for more than 100 major earthquakes (M>5

  5. A Trial of the Delineation of Gas Hydrate Bearing Zones using Seismic Methods Offshore Tokai Japan

    NASA Astrophysics Data System (ADS)

    Inamori, T.; Hato, M.

    2002-12-01

    MITI Research Well 'Nankai Trough' was drilled at offshore Tokai Japan in 1999/2000 and the existence of gas hydrate was confirmed by various proofs through borehole measurement or coring. It gave so big impact to the view of Japan_fs future energy resources and other scientific interests.The METI, Ministry of Economy, Trade and Industry, has started the national project "Methane Hydrate Exploration study" in Japan since the fall 2001. Bottom Simulating Reflectors (BSRs) were widely found on the marine seismic data acquired offshore Japan especially in the shelf-slope near Nankai Trough. BSRs are thought to be the bottom of gas hydrate stability zones, we cannot, however, get the information of gas hydrate bearing zones, such as the height of those, the porosity, the gas hydrate saturation etc, only from BSRs. In order to estimate the amount of gas hydrate accurately, we have to get those reservoir parameters of gas hydrate bearing zones from marine seismic data. The velocity of these zones is greater than that of the surrounding sediment, because pure gas hydrate has high velocity that is more than 3,000 m/s. This means the interval velocity is the key for exploration of gas hydrate. First, we have tried to image the gas hydrate bearing zones from seismic stacking velocity analysis. After the conversion to interval velocity from NMO velocity by Dix's equation, we imaged the P-wave velocity section through 2D seismic line. We successfully imaged high velocity zones above BSRs and low velocity zones beneath BSRs on P-wave velocity section. But the resolution of the section from the velocity analysis is not so high. Although we have only two adjacent well log data on the seismic line, in order to make more detailed map, we tried to execute the seismic impedance inversion with MITI Nankai Trough Well data. We made a simple initial model and inverted to seismic impedance value. We got the good impedance section and delineated the gas hydrate bearing zones through it

  6. Locating an active fault zone in Coso geothermal field by analyzing seismic guided waves from microearthquake data

    SciTech Connect

    SGP-TR-150-16

    1995-01-26

    Active fault systems usually provide high-permeability channels for hydrothermal outflow in geothermal fields. Locating such fault systems is of a vital importance to plan geothermal production and injection drilling, since an active fault zone often acts as a fracture-extensive low-velocity wave guide to seismic waves. We have located an active fault zone in the Coso geothermal field, California, by identifying and analyzing a fault-zone trapped Rayleigh-type guided wave from microearthquake data. The wavelet transform is employed to characterize guided-wave's velocity-frequency dispersion, and numerical methods are used to simulate the guided-wave propagation. The modeling calculation suggests that the fault zone is {approx} 200m wide, and has a P wave velocity of 4.80 km/s and a S wave velocity of 3.00 km/s, which is sandwiched between two half spaces with relatively higher velocities (P wave velocity 5.60 km/s, and S wave velocity 3.20 km/s). zones having vertical or nearly vertical dipping fault planes.

  7. Seismic hazard assessment in Central Asia using smoothed seismicity approaches

    NASA Astrophysics Data System (ADS)

    Ullah, Shahid; Bindi, Dino; Zuccolo, Elisa; Mikhailova, Natalia; Danciu, Laurentiu; Parolai, Stefano

    2014-05-01

    Central Asia has a long history of large to moderate frequent seismicity and is therefore considered one of the most seismically active regions with a high hazard level in the world. In the hazard map produced at global scale by GSHAP project in 1999( Giardini, 1999), Central Asia is characterized by peak ground accelerations with return period of 475 years as high as 4.8 m/s2. Therefore Central Asia was selected as a target area for EMCA project (Earthquake Model Central Asia), a regional project of GEM (Global Earthquake Model) for this area. In the framework of EMCA, a new generation of seismic hazard maps are foreseen in terms of macro-seismic intensity, in turn to be used to obtain seismic risk maps for the region. Therefore Intensity Prediction Equation (IPE) had been developed for the region based on the distribution of intensity data for different earthquakes occurred in Central Asia since the end of 19th century (Bindi et al. 2011). The same observed intensity distribution had been used to assess the seismic hazard following the site approach (Bindi et al. 2012). In this study, we present the probabilistic seismic hazard assessment of Central Asia in terms of MSK-64 based on two kernel estimation methods. We consider the smoothed seismicity approaches of Frankel (1995), modified for considering the adaptive kernel proposed by Stock and Smith (2002), and of Woo (1996), modified for considering a grid of sites and estimating a separate bandwidth for each site. The activity rate maps are shown from Frankel approach showing the effects of fixed and adaptive kernel. The hazard is estimated for rock site condition based on 10% probability of exceedance in 50 years. Maximum intensity of about 9 is observed in the Hindukush region.

  8. Changes in the Diffuse CO2 Emission and Relation to Seismic Activity in and around El Hierro, Canary Islands

    NASA Astrophysics Data System (ADS)

    Padrón, Eleazar; Melián, Gladys; Marrero, Rayco; Nolasco, Dácil; Barrancos, José; Padilla, Germán; Hernández, Pedro A.; Pérez, Nemesio M.

    2008-01-01

    Significant changes in the diffuse emission of carbon dioxide were recorded in a geochemical station located at El Hierro, Canary Islands, before the occurrence of several seismic events during 2004. Two precursory CO2 efflux increases started thirteen and nine days before two seismic events of magnitude 2.3 and 1.7, which took place near El Hierro Island, Canary Islands, on March 23 and April 15, reaching a maximun value of 51.1 and 46.2 g m-2 d-1, respectively, five and eight days before the two seismic events. Other similar increases started thirteen and five days before the occurrence of two seismic events of magnitude 1.3 and 1.5 which took place on October 15 and 21 respectively, reaching the maximum values four and one day before the earthquakes. These changes were not related to variations in atmospheric or soil parameters. The Material Failure Forecast Method (FFM), which analyzes the rate of precursory phenomena, was successfully applied to forecast the first seismic event that took place in El Hierro Island in 2004.

  9. Seismic activity triggered by the interaction of ice sheet flow with the Sør Rondane Mountains, East-Antarctica

    NASA Astrophysics Data System (ADS)

    Camelbeeck, Thierry; Lombardi, Denis; Martin, Henri; Rapagnani, Giovanni

    2015-04-01

    The interactions of the Antarctic ice sheet with the various marginal orogenic belts is poorly understood. To make up for this lack of knowledge we installed in early 2014 in the Sør Rondane Mountains of eastern Queen Maud Land, five new broadband seismic stations, in addition to an existing permanent station setting up a 90 x 30 km wide seismic network. All stations are set up to be year-round autonomously powered, all but one being on rock outcrops. Despite technical problems encountered during winter, several months of data were collected and so far about 1 month of this dataset has been processed. The background seismic noise is found to be low to extremely low with seasonal variations suggesting influence from meteorological conditions. In addition to teleseismic events, a lot of local seismicity is observed and so far 155 local quakes were detected and localized using manual picking and 2 localization methods (Hypo and NonLinLoc). The inferred locations indicate 2 major source regions for these quakes: at the border between the ice sheet and outcropping mountains and within the fastest moving ice flow suggesting that the detected seismicity is correlated with the ice flow dynamics. Further information regarding the quake focal depths and the inferred crustal model will be discussed.

  10. Zonation of North Alex Mud Volcano Highlighted by 3-D Active and Passive Seismic Data

    NASA Astrophysics Data System (ADS)

    Bialas, J.; Lefeldt, M. R.; Klaeschen, D.; Papenberg, C. A.; Brueckmann, W.

    2010-12-01

    The West Nile Delta forms part of the source of the large turbiditic Nile Deep Sea Fan. Since the late Miocene sediments have formed an up to 10 km thick pile, which includes about 1 - 3 km of Messinian evaporates. The sediment load of the overburden implies strong overpressures and salt-related tectonic deformation. Both are favourable for fluid migration towards the seafloor guided by the fractured margin. The western deltaic system, Rosetta branch, has formed an 80 km wide continental shelf. Here at 700 m water depth the mud volcano North Alex (NA) developed his circular bathymetric feature, which proved to be an active gas and mud-expelling structure. A 3-D high-resolution multichannel seismic survey (IFM-GEOMAR P-Cable system) was completed across the mud volcano. 3-D time migration provided a 3-D data cube with a 6.25 m grid. Vertical seismic sections did reveal a large set of faults located within the main mud volcano as well as surrounding the structure. Internal faults are mainly related to episodic mud expulsion processes and continuous gas and fluid production. Deep cutting external faults surround the structure in a half circle shape. Horizontal amplitude maps (time slices) of indicate recent activity of these faults even up to the seafloor. High gas saturation of the sediments is indicated by inverted reflection events. In the centre the gas front cuts into the seafloor reflection while it dips down with increasing radius. Only with the small grid resolution inward dipping reflections become visible, which form an upward opened concave reflector plane underlying the top gas front. The interpretation assumes an oval lens shaped body (conduit) saturated with gas at the top of the mud volcano. It provides the upper termination of the mud chimney. This separation is further supported by passive seismic observations. Distant earthquakes can stimulate long-period harmonic oscillations in mud volcanoes. Such oscillations are detectable with three

  11. Investigating possible influence of solar activity on some reported seismic-induced ionospheric precursors via VLF wave propagation in Earth-ionosphere waveguide

    NASA Astrophysics Data System (ADS)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar; Sasmal, Sudipta; Ray, Suman

    2016-07-01

    The diurnal propagation characteristic of VLF radio signal have been widely used to study pre-seismic ionospheric anomalies, some of which are often reported to be associated with the event. On the other hand, Solar particle events and geomagnetic activity also drive changes in the magnetosphere, which modify ionospheric parameters through the Earth's magnetic field. There are also effects originating from planetary and tidal waves, thermospheric tides and stratospheric warming. Distinguishing or separating seismically induced ionospheric fluctuations from those of other origin remain vital and challenging. In this work, we investigated the influence of solar and geomagnetic origin on some reported 'seismic ionospheric precursors' before a few major earthquakes. We also investigated anomalies in VLF day-length signal during period of low solar and geomagnetic activity (in relation to seismic activity), to understand the occurrence of VLF anomaly that are unrelated to seismicity and solar activity.

  12. Ground penetrating radar and active seismic investigation of stratigraphically verified pyroclastic deposits

    NASA Astrophysics Data System (ADS)

    Gase, A.; Bradford, J. H.; Brand, B. D.

    2015-12-01

    We conducted ground-penetrating radar (GPR) and active seismic surveys in July and August, 2015 parallel to outcrops of the pyroclastic density current deposits of the May 18th, 1980 eruption of Mount St. Helens (MSH), Washington. The primary objective of this study is to compare geophysical properties that influence electromagnetic and elastic wave velocities with stratigraphic parameters in the un-saturated zone. The deposits of interest are composed of pumice, volcanic ash, and lava blocks comprising a wide range of intrinsic porosities and grain sizes from sand to boulders. Single-offset GPR su