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Sample records for c4997 seismic records

  1. Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume VI S-Wave Measurements in Borehole C4997 Seismic Records, Wave-Arrival Identifications and Interpreted S-Wave Velocity Profile.

    SciTech Connect

    Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

    2007-06-06

    Velocity measurements in shallow sediments from ground surface to approximately 370 to 400 feet bgs were collected by Redpath Geophysics using impulsive S- and P-wave seismic sources (Redpath 2007). Measurements below this depth within basalt and sedimentary interbeds were made by UTA between October and December 2006 using the T-Rex vibratory seismic source in each of the three boreholes. Results of these measurements including seismic records, wave-arrival identifications and interpreted velocity profiles are presented in the following six volumes: I. P-Wave Measurements in Borehole C4993 II. P-Wave Measurements in Borehole C4996 III. P-Wave Measurements in Borehole C4997 IV. S-Wave Measurements in Borehole C4993 V. S-Wave Measurements in Borehole C4996 VI. S-Wave Measurements in Borehole C4997 In this volume (VI), all S-wave measurements are presented that were performed in Borehole C4997 at the WTP with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver.

  2. Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume III P-Wave Measurements in Borehole C4997 Seismic Records, Wave-Arrival Identifications and Interpreted P-Wave Velocity Profile.

    SciTech Connect

    Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

    2007-06-06

    In this volume (III), all P-wave measurements are presented that were performed in Borehole C4997 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 390 to 1220 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 40 ft (later relocated to 27.5 ft due to visibility in borehole after rain) in Borehole C4997, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4997, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

  3. Borehole Summary Report for C4997 Rotary Drilling, WTP Seismic Boreholes Project, CY 2006

    SciTech Connect

    Difebbo, Thomas J.

    2007-02-28

    The following Final Geologic Borehole Report briefly describes the drilling of a single borehole at the Waste Treatment Plant (WTP) on the Hanford, Washington, U.S. Department of Energy (DOE) reservation. The location of the WTP is illustrated in Figure 1-1. The borehole was designated as “C4997”, and was drilled to obtain seismic and lithologic data for the Pretreatment Facility and High-Level Waste Vitrification Plant in the WTP. Borehole C4997 was drilled and logged to a total depth of 1428 ft below ground surface (bgs) on October 8, 2006, and was located approximately 150 ft from a recently cored borehole, designated as “C4998”. Pacific Northwest National Laboratory (PNNL) determined the locations for C4997, C4998, and other boreholes at the WTP in cooperation with the U.S. Army Corps of Engineers (USACE) Review Panel, and the Defense Nuclear Facilities Safety Board (DNFSB). The total depth of Borehole C4997 was also determined by PNNL.

  4. Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume V S-Wave Measurements in Borehole C4996 Seismic Records, Wave-Arrival Identifications and Interpreted S-Wave Velocity Profile.

    SciTech Connect

    Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

    2007-06-06

    Velocity measurements in shallow sediments from ground surface to approximately 370 to 400 feet bgs were collected by Redpath Geophysics using impulsive S- and P-wave seismic sources (Redpath 2007). Measurements below this depth within basalt and sedimentary interbeds were made by UTA between October and December 2006 using the T-Rex vibratory seismic source in each of the three boreholes. Results of these measurements including seismic records, wave-arrival identifications and interpreted velocity profiles are presented in the following six volumes: I. P-Wave Measurements in Borehole C4993 II. P-Wave Measurements in Borehole C4996 III. P-Wave Measurements in Borehole C4997 IV. S-Wave Measurements in Borehole C4993 V. S-Wave Measurements in Borehole C4996 VI. S-Wave Measurements in Borehole C4997 In this volume (V), all S-wave measurements are presented that were performed in Borehole C4996 at the WTP with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver.

  5. 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.

  6. Borehole Summary Report for Waste Treatment Plant Seismic Borehole C4993

    SciTech Connect

    Rust, Colleen F.; Barnett, D. BRENT; Bowles, Nathan A.; Horner, Jake A.

    2007-02-28

    A core hole (C4998) and three boreholes (C4993, C4996, and C4997) were drilled to acquire stratigraphic and downhole seismic data to model potential seismic impacts and to refine design specifications and seismic criteria for the Waste Treatment Plant (WTP) under construction on the Hanford Site. Borehole C4993 was completed through the Saddle Mountains Basalt, the upper portion of the Wanapum Basalt, and associated sedimentary interbeds, to provide a continuous record of the rock penetrated by all four holes and to provide access to the subsurface for geophysical measure¬ment. Presented and compiled in this report are field-generated records for the deep mud rotary borehole C4993 at the WTP site. Material for C4993 includes borehole logs, lithologic summary, and record of rock chip samples collected during drilling through the months of August through early October. The borehole summary report also includes documentation of the mud rotary drilling, borehole logging, and sample collection.

  7. Five-day recorder seismic system

    USGS Publications Warehouse

    Criley, Ed; Eaton, Jerry P.; Ellis, Jim

    1978-01-01

    The 10-day recorder seismic system used by the USGS since 1965 has been modified substantially to improve its dynamic range and frequency response, to decrease its power consumption and physical complexity, and to make its recordings more compatible with other NCER systems to facilitate data processing. The principal changes include: 1. increasing tape speed from 15/160 ips to 15/80 ips (reducing running time from 10 days to 5 days with a 14' reel of 1 mil tape), 2. increasing the FM center frequency by a factor of 4, from 84.4 Hz to 337.6 Hz, 3. replacing the original amplifiers and FM modulators with new low-power units, 4. replacing the chronometer with a higher quality time code generator (with IRIG-C) to permit automation of data retrieval, 5. eliminating the amplifier/WWVB radio field case by incorporating these elements, along with the new TCG, in the weatherproof tape-recorder box, 6. reducing the power consumption of the motor-drive circuit by removal of a redundant component. In the new system, the tape-recorder case houses all components except the seismometers, the WWVB antenna, the 70-amp-hour 12-VDC battery (which powers the system for 5 days), and the cables to connect these external elements to the recorder box. The objectives of this report are: 1. to describe the new 5-day-recorder seismic system in terms of its constituent parts and their functions, 2. to describe modifications to parts of the original system that were retained and to document new or replacement components with appropriate circuit diagrams and constructional details, 3. to provide detailed instructions for the correct adjustment or alignment of the system in the laboratory, and 4. to provide detailed instructions for installing and operating the system in the field.

  8. 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

  9. 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

  10. Processed seismic motion records from earthquakes (1982--1993): Recorded at Scotty`s Castle, California

    SciTech Connect

    Lum, P K; Honda, K K

    1993-10-01

    The 8mm data tape contains the processed seismic data of earthquakes recorded at Scotty`s Castle, California. The seismic data were recorded by seismographs maintained by the DOE/NV in Southern Nevada. Four files were generated from each seismic recorder. They are ``Uncorrected acceleration time histories, 2. corrected acceleration, velocity and displacement time histories, 3. original recording, and 4. Fourier amplitude spectra of acceleration.

  11. Continuous recording of seismic signals in Alpine permafrost

    NASA Astrophysics Data System (ADS)

    Hausmann, H.; Krainer, K.; Staudinger, M.; Brückl, E.

    2009-04-01

    Over the past years various geophysical methods were applied to study the internal structure and the temporal variation of permafrost whereof seismic is of importance. For most seismic investigations in Alpine permafrost 24-channel equipment in combination with long data and trigger cables is used. Due to the harsh environment source and geophone layouts are often limited to 2D profiles. With prospect for future 3D-layouts we introduce an alternative of seismic equipment that can be used for several applications in Alpine permafrost. This study is focussed on controlled and natural source seismic experiments in Alpine permafrost using continuous data recording. With recent data from an ongoing project ("Permafrost in Austria") we will highlight the potential of the used seismic equipment for three applications: (a) seismic permafrost mapping of unconsolidated sediments, (b) seismic tomography in rock mass, and (c) passive seismic monitoring of rock falls. Single recording units (REFTEK 130, 6 channels) are used to continuously record the waveforms of both the seismic signals and a trigger signal. The combination of a small number of recording units with different types of geophones or a trigger allow numerous applications in Alpine permafrost with regard to a high efficiency and flexible seismic layouts (2D, 3D, 4D). The efficiency of the light and robust seismic equipment is achieved by the simple acquisition and the flexible and fast deployment of the (omni-directional) geophones. Further advantages are short (data and trigger) cables and the prevention of trigger errors. The processing of the data is aided by 'Seismon' which is an open source software project based on Matlab® and MySQL (see SM1.0). For active-source experiments automatic stacking of the seismic signals is implemented. For passive data a program for automatic detection of events (e.g. rock falls) is available which allows event localization. In summer 2008 the seismic equipment was used for the

  12. Downhole Measurements of Shear- and Compression-Wave Velocities in Boreholes C4993, C4996, C4997 and C4998 at the Waste Treatment Plant DOE Hanford Site.

    SciTech Connect

    Redpath, Bruce B.

    2007-04-27

    This report describes the procedures and the results of a series of downhole measurements of shear- and compression-wave velocities performed as part of the Seismic Boreholes Project at the site of the Waste Treatment Plant (WTP). The measurements were made in several stages from October 2006 through early February 2007. Although some fieldwork was carried out in conjunction with the University of Texas at Austin (UT), all data acquired by UT personnel are reported separately by that organization.

  13. Design and development of digital seismic amplifier recorder

    SciTech Connect

    Samsidar, Siti Alaa; Afuar, Waldy; Handayani, Gunawan

    2015-04-16

    A digital seismic recording is a recording technique of seismic data in digital systems. This method is more convenient because it is more accurate than other methods of seismic recorders. To improve the quality of the results of seismic measurements, the signal needs to be amplified to obtain better subsurface images. The purpose of this study is to improve the accuracy of measurement by amplifying the input signal. We use seismic sensors/geophones with a frequency of 4.5 Hz. The signal is amplified by means of 12 units of non-inverting amplifier. The non-inverting amplifier using IC 741 with the resistor values 1KΩ and 1MΩ. The amplification results were 1,000 times. The results of signal amplification converted into digital by using the Analog Digital Converter (ADC). Quantitative analysis in this study was performed using the software Lab VIEW 8.6. The Lab VIEW 8.6 program was used to control the ADC. The results of qualitative analysis showed that the seismic conditioning can produce a large output, so that the data obtained is better than conventional data. This application can be used for geophysical methods that have low input voltage such as microtremor application.

  14. Application of Seismic Interferometry to Natural Earthquake Records

    NASA Astrophysics Data System (ADS)

    Torii, K.; Matsuoka, T.; Aizawa, T.

    2007-12-01

    Recently, seismic interferometry has been one of the hottest topics in the exploration geophysics since this can be applied to reflection seismology. Seismic interferometry constructs Green's functions between arbitrary two points by taking cross-correlation of records observed at two locations. These Green's functions correspond to the wavefields as if an impulsive source was set at one location and seismic wave propagates from this source to the other receiver. Therefore, if we chose two surface receivers, we can reconstruct reflection seismic data. In case of using many receivers in a survey line, taking cross-correlation of all observed data at receivers generates pseudo shot-gather data for arbitrary locations. This technique does not need information of time 0 as long as all receivers measure wavefields synchronously. Therefore, there is no limitation with regard to the cause of the seismic vibrations. Natural earthquakes may be very good seismic sources for seismic interferometry. In our study, we adopt data provided by Hi-net system for applications of seismic interferometry. In 1995, 'The Great Hanshin Earthquake' struck around Osaka and Kobe in Japan. After that, Japanese Government decided to construct high-density and high-sensitivity sensor network all over Japan in order to accumulate effective information of earthquakes and understand the mechanism of earthquakes. This seismic network is called 'Hi- net system' in Japan. Hi-net system provides us much effective information, origin time, epicenter, depth, magnitude and waveform, etc... We used waveforms provided by Hi-net and generated pseudo shot-gather data by using seismic interferometry. Then, we applied these data to conventional reflection survey and analyzed underground structures in Japan.

  15. Unexpected non seismic signals recorded by broadband seismic stations during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Polkowski, M.; Grad, M.; Jóźwiak, W.

    2015-12-01

    Broadband seismometer is a very complicated and sensitive device designed to record ground motion with resolutions as low as nm/s. While short period geophone is only mass in a coil the broadband sensor is sophisticated combination of feedback circuits. Experience shows that broadband sensors are very sensitive to ground motion and its orientation, especially tilt. On March 17, 2015 an amazing, strong event was simultaneously recorded by all stations at Z component, with very long period - not typical for seismic events. Records at the same time suggested geomagnetic storm. In this study broadband seismometer response to electromagnetic wave caused by geomagnetic storms is shown and analyzed. Main observation was done using network of 13 broadband stations in northern Poland. Same signal was recorded on all stations on area of 120 km in diameter. Time and shape of recording was exactly the same as recording of magnetic anomaly in permanent magnetic station HEL located about 50 km from the nearest seismic station. The first small event was recorded at about 5 am, and following it strong event started at about 4 pm UTC. An increase of signal amplitude is observed with geomagnetic latitude in the range 52.26 - 53.27o (corresponding geographic 53.69 - 54.54oN). Seismic and magnetic records are compared for other permanent stations in the area, as well as for other recent storms. In this study circumstances needed for recording magnetic anomalies with seismic stations are discussed based on years of seismic recording by Polish permanent stations and temporary passive experiments "13BB star" and PASSEQ. National Science Centre Poland provided financial support for this work via NCN grant DEC-2011/02/A/ST10/00284.

  16. Interaction of seismic and air waves recorded at Stromboli volcano

    NASA Astrophysics Data System (ADS)

    Braun, T.; Ripepe, M.

    1993-01-01

    Explosion-quake seismograms recorded at Stromboli show that seismic phases with a high-amplitude and high-frequency content propagate with a velocity of approximately 330 m/s - the sound speed. The analysis of seismograms, recorded at a distance of 500 m from one of the three active vents, shows for the first onset a low-frequency and particle motion characteristic of a p-wave, which loses its longitudinal polarization with the onset of the air-wave. Recording the explosion-quakes simultaneously with a microphone we could ascertain that the high-frequency onset coincided with the air-wave's. In order to better understand the seismic wavefield generated by the atmospheric pressure, we performed a controlled source experiment at Stromboli using a seismic gun. Seismograms with the same two phases and particle motions comparable with the volcano-seismic data were obtained. A second experiment demonstrated, that the airwave propagates at least in the uppermost 1 m of the ground. We suggest that the seismic source of the corresponding seismograms is an explosion at the top of the magma column and conclude that the p- and air-waves are both generated in the same point and at the same time.

  17. 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.

  18. Successes and failures of recording and interpreting seismic data in structurally complex area: seismic case history

    SciTech Connect

    Morse, V.C.; Johnson, J.H.; Crittenden, J.L.; Anderson, T.D.

    1986-05-01

    There are successes and failures in recording and interpreting a single seismic line across the South Owl Creek Mountain fault on the west flank of the Casper arch. Information obtained from this type of work should help explorationists who are exploring structurally complex areas. A depth cross section lacks a subthrust prospect, but is illustrated to show that the South Owl Creek Mountain fault is steeper with less apparent displacement than in areas to the north. This cross section is derived from two-dimensional seismic modeling, using data processing methods specifically for modeling. A flat horizon and balancing technique helps confirm model accuracy. High-quality data were acquired using specifically designed seismic field parameters. The authors concluded that the methodology used is valid, and an interactive modeling program in addition to cross-line control can improve seismic interpretations in structurally complex areas.

  19. 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.

  20. Wide aperture seismic recording in offshore west Sicily and Bolivia

    SciTech Connect

    Tilander, N.G.; Lattimore, R.K.

    1994-12-31

    Seismic operations using the Wide Aperture Recording (WAR) technique were carried out in offshore west Sicily (16.5 km offsets) and in the Sub-Andean Cordillera of Bolivia (9.0 km offsets) where conventional offset data have traditionally proved inadequate for imaging complex subsurface structures. In both cases, noise-free wide aperture events were visible at long offsets, and were successfully stacked using both hyperbolic and linear moveout. In the Sicily datasets, the resulting seismic images disagree with earlier structural interpretations, but the lack of reliable ``calibration`` data in terms of well control or usable conventional seismic data make final evaluation and interpretation of the Sicily wide aperture data ambiguous. In Bolivia good quality seismic data are present across a portion of the WAR survey; the results show that the wide aperture technique may produce a valid structural image, provided the subsurface geometries are sufficiently broad and shallow. For tight structures, the technique is unlikely to produce valid images. In general, the authors` studies show that considerable effort is required at the data processing and interpretation stage, including full waveform and ray-trace modeling, in order to identify event arrivals and to attempt to validate the wide aperture structural images. Reliable calibration data in the form of well control or conventional seismic data are needed in order to provide an understanding of the WAR results.

  1. Robust seismic velocity change estimation using ambient noise recordings

    NASA Astrophysics Data System (ADS)

    Daskalakis, E.; Evangelidis, C. P.; Garnier, J.; Melis, N. S.; Papanicolaou, G.; Tsogka, C.

    2016-04-01

    We consider the problem of seismic velocity change estimation using ambient noise recordings. Motivated by (Zhan et al., 2013) we study how the velocity change estimation is affected by seasonal fluctuations in the noise sources. More precisely, we consider a numerical model and introduce spatio-temporal seasonal fluctuations in the noise sources. We show that indeed, as pointed out in (Zhan et al., 2013), the stretching method is affected by these fluctuations and produces misleading apparent velocity variations which reduce dramatically the signal to noise ratio of the method. We also show that these apparent velocity variations can be eliminated by an adequate normalization of the cross-correlation functions. Theoretically we expect our approach to work as long as the seasonal fluctuations in the noise sources are uniform, an assumption which holds for closely located seismic stations. We illustrate with numerical simulations in homogeneous and scattering media that the proposed normalization significantly improves the accuracy of the velocity change estimation. Similar behavior is also observed with real data recorded in the Aegean volcanic arc. We study in particular the volcano of Santorini during the seismic unrest of 2011-2012 and observe a decrease in the velocity of seismic waves which is correlated with GPS measured elevation.

  2. Robust seismic velocity change estimation using ambient noise recordings

    NASA Astrophysics Data System (ADS)

    Daskalakis, E.; Evangelidis, C. P.; Garnier, J.; Melis, N. S.; Papanicolaou, G.; Tsogka, C.

    2016-06-01

    We consider the problem of seismic velocity change estimation using ambient noise recordings. Motivated by Zhan et al., we study how the velocity change estimation is affected by seasonal fluctuations in the noise sources. More precisely, we consider a numerical model and introduce spatio-temporal seasonal fluctuations in the noise sources. We show that indeed, as pointed out by Zhan et al., the stretching method is affected by these fluctuations and produces misleading apparent velocity variations which reduce dramatically the signal to noise ratio of the method. We also show that these apparent velocity variations can be eliminated by an adequate normalization of the cross-correlation functions. Theoretically we expect our approach to work as long as the seasonal fluctuations in the noise sources are uniform, an assumption which holds for closely located seismic stations. We illustrate with numerical simulations in homogeneous and scattering media that the proposed normalization significantly improves the accuracy of the velocity change estimation. Similar behaviour is also observed with real data recorded in the Aegean volcanic arc. We study in particular the volcano of Santorini during the seismic unrest of 2011-2012 and observe a decrease in the velocity of seismic waves which is correlated with GPS measured elevation.

  3. Extending the North Atlantic Hurricane Record using Seismic Noise

    NASA Astrophysics Data System (ADS)

    Ebeling, Carl; Stein, Seth

    2010-05-01

    An ongoing debate within the climatological community centers on whether rising North Atlantic sea-surface temperatures attributed to anthropogenic global warming are changing the frequency or energy of hurricanes. A short and incomplete observational record makes it difficult to answer this question. Since North Atlantic hurricane records were based entirely on ship logs and land observations before aircraft reconnaissance began in 1944, it is possible that hurricanes may have gone unobserved before then. Even after the initiation of regular aircraft observation, not all areas were monitored. Hence the potential for sampling problems exists up until the advent of satellite-based observation in the mid-1960's, implying that an undercount in the historical record is likely. To address this issue, we are developing methodology to improve the record of the number of North Atlantic hurricanes through the analysis of their signals recorded on decades of historical seismograms. Ambient seismic noise--signals derived from natural sources not related to earthquakes--is generated by atmospheric energy and so has been used as a proxy for oceanic wave climate and an indication of decadal-scale climate variability. Hence ambient seismic noise should be usable to detect hurricanes that may have gone unobserved. As a first step in developing such a methodology, we are using digital data from the HRV (Harvard, Massachusetts, USA) and SJG (San Juan, Puerto Rico, USA) seismic stations to calibrate seismic noise signals correlated with maximum wind speeds of well-characterized North Atlantic hurricanes, and investigate the development of a hurricane discriminant. Although a hurricane signature is not apparent in raw HRV power data, filtering of data recorded during hurricane Andrew (August 1992) in the 5-7 second passband retrieves a signal correlatable with Andrew's maximum wind speed. An empirical hurricane discriminant based on power amplitudes in this passband demonstrates that

  4. A Comparison of Seismic Records of Calving Glaciers

    NASA Astrophysics Data System (ADS)

    Walter, Fabian; Amundson, Jason M.; O'Neel, Shad; Clinton, John F.; Luethi, Martin P.; Bassis, Jeremy; Fricker, Helen Amanda

    2010-05-01

    Glacier calving is a key process in the cryosphere's contribution to sea level rise. It is responsible for virtually all of Antarctica's ice mass loss to the ocean and about half of Greenland's negative mass balance. As glacier calving is a highly complicated and variable phenomenon, its physical laws are poorly understood. For this reason "dynamical mass loss" is one of the critical mechanisms that have yet to be incorporated into large-scale ice sheet models that aim to predict future sea level variations. As calving environments are almost always difficult to access, data pertaining to calving processes are usually gathered remotely. Seismometers have recently proven to be a valuable tool for studying calving, even though they may be located far away from the calving front. Pre-existing global and regional seismic networks thus constitute a valuable resource for the study of glacier calving as they allow for automatic detection and monitoring of calving activity. Various sources occurring nearly simultaneously give rise to calving seismicity. Potential source mechanisms include fracturing, hydraulic transients, glacier acceleration, ocean wave action, and icebergs scraping the fjord walls, bottom, or terminus. Fracturing and hydraulic transients emit seismic energy above 1 Hz and are only recorded locally, whereas glacier acceleration, iceberg scraping, and ocean waves may produce waveforms with periods of 100's or 1000's of seconds and can be recorded by far-field seismometers. We present examples of such low-frequency seismicity from Jakobshavn Isbrae, Greenland, and Columbia and Yahtse Glaciers, Alaska. Finally, we discuss the possibility of remotely investigating calving behavior by comparing the seismic signature of individual calving events from different glaciological settings.

  5. Characterizing North Texas Seismicity with a High Density Network of Exploration Seismic Reflection Recorders

    NASA Astrophysics Data System (ADS)

    Hayward, C.; Barklage, M.; Hollis, D.; DeShon, H. R.; Magnani, M. B.

    2014-12-01

    A series of low magnitude earthquakes in North Texas near Azle, Texas began 5-Nov 2013 and continues to the present. By 3-Jan 2014, hypocenters based on a temporary local network were sufficiently well defined to plan an experiment using a dense network near the epicenters. On 25-Feb 2014, NodalSeismic in cooperation with Southern Methodist University, installed and operated 130 vertical 10 Hz recorders distributed along three lines within a few km of the epicenters and collected 10 days of continuous seismic recording at 500 samples/second. Data was converted from SEGD to standard earthquake seismological formats (SEED) for processing.During the time of the high density recording, relatively few events in the Azle area were detected by the 12 station local network; however, correlation processing on the dense network detected over 100 events. In addition regional events from local quarries as well as a teleseism were well recorded. One of the 10Hz recorders was within 50m of a 1 Hz vertical seismometer, providing the ability to evaluate the utility of the high frequency geophones for recording broader band signals. By comparing catalogs from the local network with detection lists from the high density network, the detection threshold for the augmented network is determined. Delta time offsets for the teleseismic signal may be used to determine relative station corrections (static offsets) prior to fitting classical hyperbola to a velocity model and to estimate epicenters. Comparison between dense network location results and results using standard techniques on the 12 station local network provides an assessment of the utility of this high density technique to quickly evaluate areas where induced seismicity is suspected. Finally, the method provides an opportunity to compare background noise levels between the rapidly installed low cost exploration systems and the more carefully deployed local network.

  6. Multiband array detection and location of seismic sources recorded by dense seismic networks

    NASA Astrophysics Data System (ADS)

    Poiata, Natalia; Satriano, Claudio; Vilotte, Jean-Pierre; Bernard, Pascal; Obara, Kazushige

    2016-06-01

    We present a new methodology for detection and space-time location of seismic sources based on multiscale, frequency-selective coherence of the wave field recorded by dense large-scale seismic networks and local antennas. The method is designed to enhance coherence of the signal statistical features across the array of sensors and consists of three steps: signal processing, space-time imaging, and detection and location. The first step provides, for each station, a simplified representation of seismic signal by extracting multiscale non-stationary statistical characteristics, through multiband higher-order statistics or envelopes. This signal processing scheme is designed to account for a priori unknown transients, potentially associated with a variety of sources (e.g. earthquakes, tremors), and to prepare data for a better performance in posterior steps. Following space-time imaging is carried through 3-D spatial mapping and summation of station-pair time-delay estimate functions. This step produces time-series of 3-D spatial images representing the likelihood that each pixel makes part of a source. Detection and location is performed in the final step by extracting the local maxima from the 3-D spatial images. We demonstrate the efficiency of the method in detecting and locating seismic sources associated with low signal-to-noise ratio on an example of the aftershock earthquake records from local stations of International Maule Aftershock Deployment in Central Chile. The performance and potential of the method to detect, locate and characterize the energy release associated with possibly mixed seismic radiation from earthquakes and low-frequency tectonic tremors is further tested on continuous data from southwestern Japan.

  7. Multi-band array detection and location of seismic sources recorded by dense seismic networks

    NASA Astrophysics Data System (ADS)

    Poiata, Natalia; Satriano, Claudio; Vilotte, Jean-Pierre; Bernard, Pascal; Obara, Kazushige

    2016-02-01

    We present a new methodology for detection and space-time location of seismic sources based on multi-scale, frequency-selective coherence of the wave field recorded by dense large-scale seismic networks and local antennas. The method is designed to enhance coherence of the signal statistical features across the array of sensors and consists of three steps: signal processing, space-time imaging, and detection and location. The first step provides, for each station, a simplified representation of seismic signal by extracting multi-scale non-stationary statistical characteristics, through multi-band higher-order statistics or envelopes. This signal processing scheme is designed to account for a priori unknown transients, potentially associated with a variety of sources (e.g., earthquakes, tremors), and to prepare data for a better performance in posterior steps. Following space-time imaging is carried through 3D spatial mapping and summation of station-pair time-delay estimate functions. This step produces time series of 3D spatial images representing the likelihood that each pixel makes part of a source. Detection and location is performed in the final step by extracting the local maxima from the 3D spatial images. We demonstrate the efficiency of the method in detecting and locating seismic sources associated with low signal-to-noise ratio on an example of the aftershock earthquake records from local stations of International Maule Aftershock Deployment in Central Chile. The performance and potential of the method to detect, locate and characterize the energy release associated with possibly mixed seismic radiation from earthquakes and low-frequency tectonic tremors is further tested on continuous data from southwestern Japan.

  8. Monitoring Klyuchevskoy group of volcanoes (Kamchatka) using seismic noise records

    NASA Astrophysics Data System (ADS)

    Gómez-García, Clara; Brenguier, Florent; Shapiro, Nikolai M.; Droznin, Dmitry V.; Droznina, Svetlana Y.; Chebrov, Victor N.; Gordeev, Evgenii I.

    2016-04-01

    In the last decade, extraction of Green functions from seismic ambient noise has been used extensive and efficiently in different contexts and scales: from imaging to monitoring the Earth's interior and from global to local scales. By using coda waves of noise cross-correlations to estimate travel time perturbations, we can assign changes in delay times to changes in the medium's velocity. Due to this technique attribute of continuous recording of the medium, it can accurately detect very small seismic velocity changes linked to small disturbances in volcano interiors. However, cross-correlation functions (CCF) do not necessary converge to media Green function: measurements of waveforms perturbations within a volcanic edifice are affected by the noise fluctuation. The Klyuchevskoy volcanic group, located above the edge of the Pacific Plate subducting beneath Kamchatka, is one of the most active clusters of volcanoes in the word. It is characterized by strongly localized volcanic tremor sources, which often dominate the recorded wavefield. To monitor and get measurements of temporal changes of these active volcanoes, we use coda waves of daily CCF from a total of 19 seismic stations from the seismic network operated by the Kamchatka Branch of the Geophysical Service (KBGS) of the Russian Academy of Sciences. Our study period goes from January 2009 to July 2013 in which two eruptions occurred: one from the Klyuchevskoy volcano (2009-2010) and the other from the Tolbachik volcano (2012-2013). After a quality checking of the records and testing different filters, we filter data in the frequency range 0.08 - 7 Hz and we use the Moving Window Cross Spectrum (MWCS) method to measure the relative time shifts. As both eruptions are characterized by emissions of seismic tremors, we avoid the choice of an arbitrary reference CCF: we compute velocity changes between all pairs of daily CCF. We retrieve a continuous velocity change time series for each station pair using a

  9. Seismic Record Processing Program (SRP), Version 1.03

    SciTech Connect

    Karabalis, D.L.; Cokkinides, G.J.; Rizos, D.C.

    1992-04-01

    The Seismic Record Processing Program (SRP) is an interactive computer code developed for the calculation of artificial earthquake records that comply with the US Nuclear Regulatory Commission Standard Review Plan. The basic objective of SRP is the calculation of artificial seismic time histories that correspond to Design Response Spectra specified in the US Atomic Energy Commission Regulatory Guide 1.60 and/or the Power Spectral Density (PSD) requirements of the NRC Standard Review Plan. However, SRP is a general computer code and can accommodate any arbitrarily specified Target Response Spectra (TRS) or PSD requirements. In addition, among its other futures, SRP performs quadratic baseline correction and calculates correlations factors for a set of up to three earthquake records. This manual is prepared in two parts. The first part describes the methodologies and criteria used while the second is a user`s manual. In section 1 of the first part, the techniques used for the adjustment of a given earthquake record to a required TRS family of curves for a set of specified damping ratios are presented. Similarly, in section 2 of the first part, the PSD of an earthquake record is compared to a target PSD and adjusted accordingly. Sections 3 and 4 of the first part deal with the subjects of baseline correction and correlation of earthquake records, respectively. The second part is the user`s manual. The user`s manual contains a list of the computer hardware requirements, instructions for the program installation, a description of the user generated input files, and a description of all the program menus and commands.

  10. Lotung large-scale seismic test strong motion records

    SciTech Connect

    Not Available

    1992-03-01

    The Electric Power Research Institute (EPRI), in cooperation with the Taiwan Power Company (TPC), constructed two models (1/4 scale and 1/12 scale) of a nuclear plant concrete containment structure at a seismically active site in Lotung, Taiwan. Extensive instrumentation was deployed to record both structural and ground responses during earthquakes. The experiment, generally referred to as the Lotung Large-Scale Seismic Test (LSST), was used to gather data for soil-structure interaction (SSI) analysis method evaluation and validation as well as for site ground response investigation. A number of earthquakes having local magnitudes ranging from 4.5 to 7.0 have been recorded at the LSST site since the completion of the test facility in September 1985. This report documents the earthquake data, both raw and processed, collected from the LSST experiment. Volume 1 of the report provides general information on site location, instrument types and layout, data acquisition and processing, and data file organization. The recorded data are described chronologically in subsequent volumes of the report.

  11. Landslide caracteristics determination using bayesian inversion and seismic recording

    NASA Astrophysics Data System (ADS)

    Mangeney, A.; Moretti, L.; Capdeville, Y.; Stutzmann, E.; Bodin, T.; Bouchut, F.

    2014-12-01

    Gravitational instabilities, such as landslides, avalanches, or debris flows, play a key role in erosional processes and represent one of the major natural hazards in mountainous, coastal, and volcanic regions. Despite the great amount of field, experimental and numerical work devoted to this problem, the understanding of the physical processes at work in gravitational flows is still an open issue, in particular due to the lack of observations relevant to their dynamics. In this context, the seismic signal generated by gravitational flows is a unique opportunity to obtain information on their dynamics and characteristics. Here we present the study of the 1997 Boxing Day landslide that occurred in Montserrat. We accessed the force applied by the landslide to the ground surface responsible of the seismic waves by inverting the seismic waveform recorded (force-time function). This force was then used as a constraint in a bayesian inversion problem where the forward problem is the force-time function calculation obtained by simulating the landslide with the SHALTOP model (mangeney et al., 2007). With this method, we are able to give an estimate of the rheology (friction coefficient) and the initial shape of the collapsing mass. The volume retrieved is very similar to that obtained by field observations. The friction coefficient determined is also similar to that constrained by former studies or to that predicted by empirical laws (Lucas et al., 2014). Furthermore the method permits to give an estimate of the error made on these parameters.

  12. Processed seismic motion records from Big Bear, California earthquake of June 28, 1992, recorded at seismograph stations in southern Nevada

    SciTech Connect

    Lum, P.K.; Honda, K.K.

    1993-04-01

    The 8mm data-tape contains the processed seismic data of the Big Bear, California earthquake of June 28, 1992. The seismic data were recorded by 15 seismographs maintained by the DOE/NV in Southern Nevada. Four files were generated from each seismic recorder. They are ``Uncorrected acceleration time histories, 2. Corrected acceleration, velocity and displacement time histories, 3. Pseudo response velocity spectra, and 4. Fourier amplitude spectra of acceleration.``

  13. Processed seismic motion records from Landers, California earthquake of June 28, 1992, recorded at seismograph stations in southern Nevada

    SciTech Connect

    Lum, P.K.; Honda, K.K.

    1993-04-01

    The 8mm data tape contains the processed seismic data of the Landers, California earthquake of June 28, 1992. The seismic, data were recorded by 19 seismographs maintained by the DOE/NV in Southern Nevada. Four files were generated from each seismic recorder. They are ``Uncorrected acceleration time histories, 2. Corrected acceleration, velocity and displacement time histories, 3. Pseudo response velocity spectra, and 4. Fourier amplitude spectra of acceleration.``

  14. Autonomous, continuously recording broadband seismic stations at high-latitude

    NASA Astrophysics Data System (ADS)

    Beaudoin, B.; Parker, T.; Bonnett, B.; Tytgat, G.; Anderson, K.; Fowler, J.

    2009-04-01

    IRIS PASSCAL is in the third year of an NSF funded development and acquisition effort to establish a pool of cold-hardened seismic stations specifically for high-latitude broadband deployments. We have two complete years of field trials and have successfully recorded continuous seismic data during both years with data recovery rates of ~90%. Our design is premised on a 2W autonomous system recording to local media, capable of lasting two years without service. The system is composed of four new design elements: a heavily insulated station enclosure; a state-of-health (SOH) Iridium modem; a light weight, easily deployed solar panel mount; and a power system that includes power switching between primary (Lithium Thionyl Chloride) and secondary batteries. The station enclosures have proved most critical in keeping our data acquisition systems operating within manufacturer specifications and primary batteries within a 50-70% efficiency range. Enclosures with 2.5cm-thick vacuum panels and 5cm of foam insulation have kept interior enclosure temperatures 25-30°C above background (typically below -50°C). This austral summer we are deploying version three of our enclosures. Significant changes in the design include thicker vacuum panels (5cm), more robust construction, and simplified cable routing. An important aspect of our station design is easy installation and minimal weight. To simplify installation our station enclosures are packed with datalogger, SOH communications and batteries in the lab or base camp, so that access to the internal components is not necessary at the remote site. Bulkhead connectors allow a user to fully interact with the system without ever having to open the enclosure. Solar panel mounts are also fully constructed prior to deployment. Once on site, digging two large holes (one for the enclosure and one for the broadband seismometer) and constructing the site takes roughly 2 hours. A station designed to record continuously for 12-14 months is

  15. Finding Trapped Miners by Using a Prototype Seismic Recording System Made from Music-Recording Hardware

    USGS Publications Warehouse

    Pratt, Thomas L.

    2009-01-01

    The goal of this project was to use off-the-shelf music recording equipment to build and test a prototype seismic system to listen for people trapped in underground chambers (mines, caves, collapsed buildings). Previous workers found that an array of geophones is effective in locating trapped miners; displaying the data graphically, as well as playing it back into an audio device (headphones) at high speeds, was found to be effective for locating underground tapping. The desired system should record the data digitally to allow for further analysis, be capable of displaying the data graphically, allow for rudimentary analysis (bandpass filter, deconvolution), and allow the user to listen to the data at varying speeds. Although existing seismic reflection systems are adequate to record, display and analyze the data, they are relatively expensive and difficult to use and do not have an audio playback option. This makes it difficult for individual mines to have a system waiting on the shelf for an emergency. In contrast, music recording systems, like the one I used to construct the prototype system, can be purchased for about 20 percent of the cost of a seismic reflection system and are designed to be much easier to use. The prototype system makes use of an ~$3,000, 16-channel music recording system made by Presonus, Inc., of Baton Rouge, Louisiana. Other manufacturers make competitive systems that would serve equally well. Connecting the geophones to the recording system required the only custom part of this system - a connector that takes the output from the geophone cable and breaks it into 16 microphone inputs to be connected to the music recording system. The connector took about 1 day of technician time to build, using about $300 in off-the-shelf parts. Comparisons of the music recording system and a standard seismic reflection system (A 24-channel 'Geode' system manufactured by Geometrics, Inc., of San Jose, California) were carried out at two locations. Initial

  16. Chelyabinsk airburst shockwave characteristics from Korkino coal mine seismic records

    NASA Astrophysics Data System (ADS)

    Popova, Olga; Rybnov, Yurij; Shuvalov, Valery; Jenniskens, Peter; Kharlamov, Vladimir; Usoltseva, Olga; Dyagilev, Ruslan

    The Chelyabinsk airburst of 15 February 2013, was exceptional because of the large kinetic energy of the impacting body and the airburst that was generated, creating significant damage and injuries in a densely populated area. The butterfly-shape of the damaged area (Popova et al., 2013) was explained from the fact that the energy was deposited over a range of altitudes. Some uncertainty remains about the source energy because it is not known precisely at what pressure glass is expected to break. Reasonable results were obtained for energies of 300-520 kt TNT and over pressures of 500-1000 Pa under assumption that energy release follows the light curve (Popova et al., 2013). There were no any instrumental records of overpressure in the damaged area. However, the coal mine at Korkino is situated in the damage area close to the meteoroid trajectory, almost immediately below the region of highest energy deposition. Its seismic control system with three-component geophones 3G4.5 recorded the blast wave from the meteoroid entry indirectly from its coupling to the ground. This is the only instrumental record of the airburst close to the meteoroid trajectory. Analysis of these records is presented, which allowed us to determine the source location and strength. The direction of the blast wave arrival coincides with the shortest distance to the trajectory. The amplitude of shock wave is evaluated and the measured values are in agreement with estimates of the source energy based on our numerical modeling of the glass damage area. Popova O.,Jenniskens P., Emel’yanenko V. et al. (the Chelyabinsk Airburst Consortium) Chelyabinsk Airburst, Damage Assessment, Meteorite Recovery, and Characterization, Science, 2013, 342, 1069-1073

  17. Seismicity in West Iberia: small scale seismicity recording from a Dense Seismic Broadband Deployment in Portugal (WILAS Project)

    NASA Astrophysics Data System (ADS)

    Afonso Dias, Nuno; Custódio, Susana; Silveira, Graça; Carrilho, Fernando; Haberland, Christian; Lima, Vânia; Rio, Inês; Góngora, Eva; Marreiros, Célia; Morais, Iolanda; Vales, Dina; Fonseca, João; Caldeira, Bento; Villaseñor, Antonio

    2013-04-01

    Over the last years several projects targeted the lithospheric structure and its correlation with the surface topography, e.g. EarthSCOPE/USArray or TOPO-EUROPE. Two projects focused on the Iberian Peninsula, one giving particular attention to the southern collision margin (TOPO-MED) and the other to the central cratonic Massif (TOPO-IBERIA/IBERArray). These projects mostly rely on deployed dense seismic broadband (BB) networks with an average inter-station spacing of 60km, which strongly increases the available network spatial coverage. The seismicity recording in such networks is critical to access current rates of lithospheric deformation. Within the scope of project WILAS - West Iberia Lithosphere and Astenosphere Structure (PTDC/CTE-GIX/097946/2008), a 3-year project funded by the Portuguese Science & Technology Foundation (FCT), we deployed a temporary network of 30 BB stations in Portugal between 2010 and 2012, doubling the total number of operating BB stations. Together with the permanent and TOPO-IBERIA stations, the resulting networks provided a full and dense coverage of the Iberian Peninsula. The majority of the permanent stations in Portugal, aimed at the seismic surveillance, are located in the southern part of the country in result of the active tectonic convergence between Iberia and Africa. Therefore, the temporary stations were mainly deployed in the north of Portugal. These temporary stations allowed an improvement of the earthquake detection threshold. The detection of seismic events was based on the analysis of daily spectrograms of the entire network, the new events detected being analysed and included in the catalogue. The new detected events are located mainly in the north, with magnitudes as low as 0.5 ML and in the offshore in the Estremadura Spur. Some additional events were also located south of Portugal, between the Gorringe Bank and the Gulf of Cadiz, in this case the lower magnitudes being ~2.0ML. Focal mechanisms will also be

  18. Recorded seismic response of Pacific Park Plaza. II. System identification

    USGS Publications Warehouse

    Safak, F.; Celebi, M.

    1992-01-01

    This is the second of two companion papers on the recorded seismic response of the Pacific Park Plaza building, in Emeryville, Calif., during the October 17, 1989, Ms = 7.1 (surface-wave magnitude) Loma Prieta earthquake. In this second part, the recorded data are analyzed in more detail by using system-identification techniques. The three-dimensional behavior and the coupled modes of the building are determined, and the effects of soil-structure interaction are investigated. The study shows that the response of the building is nonlinear at the beginning, and becomes linear after 17 sec into the earthquake. The dominant motion of the building follows an elliptical path oriented in the southeast-northwest direction. Some of the modes are complex, with nonproportional damping, and there are phase differences among modal response components. The fundamental mode of the building is a translation in the southeast-northwest direction at 0.4 Hz, with 13% damping. The wing displacements relative to the center core are large, about 50% of the center core displacements, and indicate significant torsion in the center core. The soil-structure interaction is characterized by a vibration at 0.7 Hz. This is believed to be the fundamental frequency of the surrounding soil medium. The rocking motions of the building are negligible.

  19. Joint Determination of Event Location and Magnitude from Historical Seismic Damage Records

    NASA Astrophysics Data System (ADS)

    Park, S.; Hong, T. K.

    2014-12-01

    Large earthquakes have long recurrence intervals. It is crucial to consider long-time seismicity for a proper assessment of potential seismic hazards. It is required to use historical earthquake records to complement the long-time seismicity records. Historical earthquake records remain as in seismic damage description with limited accuracy in source parameters including event location and its size. It is important to determine epicenters and magnitudes of historical earthquakes accurately. A noble method to determine the event location and magnitude from historical seismic damage records is introduced. Seismic damage is typically proportional to the event magnitude, and is inversely proportional to the distance. This feature allows us to deduce the event magnitude and location from spatial distribution of seismic intensities. However, the magnitude and distance trade off each other, inhibiting unique determination of event magnitude and location. The Gutenberg-Richter frequency-magnitude relationship is additionally considered to constrain the source parameters. The Gutenberg-Richter frequency-magnitude relationship is assumed to be consistent between instrumental and historical seismicity. A set of event location and magnitude that satisfy the chance of event occurrence according to the Gutenberg-Richter frequency-magnitude relationship is selected. The accuracy of the method is tested for synthetic data sets, and the validity of the method is examined. The synthetic tests present high accuracy of the method. The method is applied to historical seismic damage records, which allows us to calibrate the source parameters of historical earthquakes.

  20. Wide-angle seismic recordings from the 1998 Seismic Hazards Investigation of Puget Sound (SHIPS), western Washington and British Columbia

    USGS Publications Warehouse

    Brocher, Thomas M.; Parsons, Tom; Creager, Ken C.; Crosson, Robert S.; Symons, Neill P.; Spence, George D.; Zelt, Barry C.; Hammer, Philip T.C.; Hyndman, Roy D.; Mosher, David C.; Trehu, Anne M.; Miller, Kate C.; Brink, Uri S. ten; Fisher, Michael A.; Pratt, Thomas L.; Alvarez, Marcos G.; Beaudoin, Bruce C.; Louden, Keith E.; Weaver, Craig S.

    1999-01-01

    This report describes the acquisition and processing of deep-crustal wide-angle seismic reflection and refraction data obtained in the vicinity of Puget Lowland, the Strait of Juan de Fuca, and Georgia Strait, western Washington and southwestern British Columbia, in March 1998 during the Seismic Hazards Investigation of Puget Sound (SHIPS). As part of a larger initiative to better understand lateral variations in crustal structure along the Cascadia margin, SHIPS participants acquired 1000 km of deep-crustal multichannel seismic-reflection profiles and 1300 km of wideangle airgun shot lines in this region using the R/V Thompson and R/V Tully. The Tully was used to record airgun shots fired by the Thompson in two different geometries: (1) expanding spread profiles (ESPs) and (2) constant offset profiles (COPs). Prior to this reflection survey, we deployed 257 Reftek and 15 ocean-bottom seismic recorders to record the airgun signals at far offsets. All data were recorded digitally on large-capacity hard disks. Although most of these stations only recorded the vertical component of motion, 95 of these seismographs recorded signals from an oriented 3-component seismometer. By recording signals generated by the Thompson's marine air gun array, operated in two differing geometries having a total volume of 110 and 79 liters (6730 and 4838 cu. in.), respectively, the arrays of wide-angle recorders were designed to (1) image the crustal structure, particularly in the vicinity of crustal faults and Cenozoic sedimentary basins, (2) determine the geometry of the Moho, and (3) image the subducting Gorda and Juan de Fuca plates. Nearly 33,300 air gun shots were recorded along several seismic lines. In this report, we illustrate the expanding spread profiles acquired using the Thompson and Tully, describe the land and ocean-bottom recording of the air gun signals, discuss the processing of the land recorder data into common receiver gathers, and illustrate the processed wide

  1. Analysis of Seismicity Recorded at an Underground Coal Mine During a Fatal Fire and Explosion Sequence

    NASA Astrophysics Data System (ADS)

    Swanson, P. L.

    2002-12-01

    On July 31, 2000 a sequence of four explosions occurred at the Willow Creek underground coal mine (Helper, UT) killing two miners and injuring 8 others. An investigation by the Mine Safety and Health Administration (MSHA) points to a roof fall as the most likely source of ignition of methane and other gaseous hydrocarbons which led to the explosions. NIOSH operated a seismic monitoring system at the mine in 1998-2000. Seismicity recorded by the underground array prior to and during the explosion sequence has been analyzed in an attempt to place constraints on the initial ignition source. Velocity sensors (4.5 Hz) were deployed in a 12-station underground array measuring 0.9 by 2.2 km. Throughout mining of the D-3 longwall panel, rates of seismic event occurrence, face advance, and methane accumulation were observed to be closely correlated indicating a strong association between longwall caving/deformation processes and gas release. At the approximate time of the first explosion a low-amplitude, emergent multiple-pulse seismic signal was observed which is interpreted to be the seismic signature of the first explosion. Features characteristic of caving- or fracture-related events are absent indicating that it was not accompanied nor preceded by such an event at least within the few seconds of recorded pre-trigger time. The preceding seismic event that was large enough to be recorded by the seismic monitoring system occurred 11 minutes before the first explosion. This observation does not rule out the possibility of a smaller fall that may have been ejected into the mine opening with damaging force but was not large enough to produce a seismic event that triggered the system. Consequently, the data appear incapable of supporting or refuting a rock fall as the ignition source. Seismic events were not recorded at the estimated times of the other three explosions.

  2. Glacial seismic events from Greenland recorded by the POLENET/LAPNET seismic array during the IPY 2007-2009

    NASA Astrophysics Data System (ADS)

    Kozlovskaya, E.

    2012-12-01

    Glacial earthquakes are seismic events associated with rapid changes in the dynamics of ice sheets and glaciers. They belong to the class of so-called slow earthquakes caused by a variety of stick-slip and creep processes. Recordings of glacial events are depleted in high frequencies and can be detected from recordings of broadband seismic instruments. Monitoring of such events from Greenland at regional distances was one of the major targets of the POLENET/LAPNET passive seismic experiment in northern Fennoscandia (northern parts of Finland, Sweden, Norway and Russian Karelia) during the IPY 2007-2009. The POLENET/LAPNET array, with the average spacing between stations of 70 km, recorded high-frequency continuous data of 37 temporary stations, which were in operation during the time frame from 01.05.2008 to 31.09.2009, and of 21 stations of selected permanent networks in the Fennoscandia. Glacial events from Greenland were identified using manual analysis of the continuous POLENET/LAPNET data filtered by a bandpass filter from 35 s to 140 s frequency band. The detected events were located using standard array techniques. Our study demonstrated that the POLENET/LAPNET array, located at regional distances from Greenland, recorded more such events than the Global Seismographic Network (GSN) during the same observation period. In addition, the array detected a number of slow earthquakes originating from northern part of Mid-Atlantic Ridge, Iceland, vicinity of Spitsbergen, Jan Mayen Island and a number of events originated from Arctic Canada. This shows that analysis of recordings of broadband stations in low-frequency can provide new information about seismicity and spreading processes in the Arctics. Our study proves that glacial earthquakes in Greenland show a seasonality, with most of events occurring during summer months. We found out that during 2008, significant number of events originated from the northern part of Greenland, where recent investigation using

  3. Monitoring seismic velocity changes caused by the 2014 Northern Aegean earthquake using continuous ambient noise records

    NASA Astrophysics Data System (ADS)

    Evangelidis, Christos; Daskalakis, Emmanouil; Tsogka, Chrysoula

    2016-04-01

    The 24 May 2014 Northern Aegean earthquake (6.9 Mw), an event on the Northern Aegean Trough (NAT), ruptured on two different fault segments with a total ruptured length of ~100 km. For the second delayed segment, rupture propagated eastward from the hypocenter for ˜65 km with a supershear velocity (5.5 km/s). Low-aftershock seismicity on the supershear segment implies a simple and linear fault geometry there. An effort to monitor temporal seismic velocity changes across the ruptured area of the Northern Aegean earthquake is underway. In recent years, neighboring seismic broadband stations near active faults have been successfully used to detect such changes. The crosscorrelation functions (CCF) of ambient noise records between stations yields the corresponding traveltimes for those inter-station paths. Moreover, the auto-correlation functions (ACF) at each station produce the seismic responce for a coincident source and receiver position. Possible temporal changes of the measured traveltimes from CCFs and ACFs correspond to seismic velocity changes. Initially, we investigate the characteristics and sources of the ambient seismic noise as recorded at permanent seismic stations installed around NAT at the surrounding islands and in mainland Greece and Turkey. The microseismic noise levels show a clear seasonal variation at all stations. The noise levels across the double frequency band (DF; period range 4-8 s) reflect the local sea-weather conditions within a range of a few hundred kilometers. Three years of continuous seismic records framing the main shock have been analysed from ~15 stations within a radius of 100 km from the epicentre. We observe a clear decrease of seismic velocities most likely corresponding to the co-seismic shaking. The spatial variation of this velocity drop is imaged from all inter-station paths that correspond to CCF measurements and for station sites that correspond to ACF measurements. Thus, we explore a possible correlation between co-seismic

  4. Investigations of Periodic Disturbances on Seismic Aftershock Recordings

    NASA Astrophysics Data System (ADS)

    Liebsch, Mattes; Gorschlüter, Felix; Knoop, Jan-Frederik; Altmann, Jürgen

    2013-04-01

    The Comprehensive Nuclear Test-Ban Treaty Organisation (CTBTO) runs the International Monitoring System (IMS) to detect possible violations of the treaty. The seismic sensors of the IMS are set up to detect every underground explosion with a yield of 1 kT TNT equivalent or even better everywhere on the world. Under consideration of all IMS data the hypocentre of a large underground explosion is located within an area of about 1000 sq km. To verify if it was a violation of the Test-Ban Treaty the CTBTO (after CTBT entry into force) is allowed to carry out an on-site inspection (OSI) in the area of suspicion. During an OSI the hypocentre is to be located much more precisely; for this a local seismic aftershock monitoring system (SAMS) can be installed to detect small seismic events caused as a consequence of the explosion, such as relaxation of the rock around the cavity. However the magnitude of these aftershock signals is extremely weak. Other difficulties arise from other seismic signals in the inspection area, for example caused by vehicles of the inspectors, from coupling of airborne signals to the ground, or even by intended attempts to disturb the OSI. While the aftershock signals have a pulsed shape, man-made seismic signals (primarily created by engines) usually show periodic characteristics and thus are representable as a sum of sine functions and their harmonics. A mathematical expression for the Hann-windowed discrete Fourier transform of the underlying sine is used to characterise every such disturbance by the amplitude, frequency and phase. The contributions of these sines are computed and subtracted from the complex spectrum sequentially. Synthetic sines superposed to real signals, orders of magnitude stronger than the latter, can be removed successfully. Removal of periodic content from the signals of a helicopter overflight reduces the amplitude by a factor 3.3 when the frequencies are approximately constant. To reduce or prevent disturbing seismic

  5. Integrated Observation and Database System for Seismic Records using Web GIS and Data Interoperation

    NASA Astrophysics Data System (ADS)

    Tobita, Jun; Fukuwa, Nobuo; Kurata, Kazumi

    A Web-GIS based system is developed for utilization of seismic records observed by a number of organizations and its effective integration by data interoperation technology on the Internet. Various data on ground, building and regional conditions are collected and viewed on the Web GIS, such as geological condition on shallow and deep soil, structural specification on the observed buildings, estimated distribution of seismic intensity and seismic waves, and indices on disaster mitigation potential of the area. Further aspects on utilization of the system for aseismic structural design, regional disaster mitigation and disaster education are also discussed. New ways for low-cost and efficient seismic observation procedure are introduced using the developed system with assistance of school teachers and students, engineers, building users and the persons who are interested in the seismic observation and disaster mitigation.

  6. Attenuation (1/Q) estimation in reflection seismic records

    NASA Astrophysics Data System (ADS)

    Raji, Wasiu; Rietbrock, Andreas

    2013-08-01

    Despite its numerous potential applications, the lack of a reliable method for determining attenuation (1/Q) in seismic data is an issue when utilizing attenuation for hydrocarbon exploration. In this paper, a new method for measuring attenuation in reflection seismic data is presented. The inversion process involves two key stages: computation of the centroid frequency for the individual signal using a variable window length and fast Fourier transform; and estimation of the difference in the centroid frequency and travel time for paired incident and transmitted signals. The new method introduces a shape factor and a constant which allows several spectral shapes to be used to represent a real seismic signal without altering the mathematical model. Application of the new method to synthetic data shows that it can provide reliable estimates of Q using any of the spectral shapes commonly assumed for real seismic signals. Tested against two published methods of Q measurement, the new method shows less sensitivity to interference from noise and change of frequency bandwidth. The method is also applied to a 3D data set from the Gullfaks field, North Sea, Norway. The trace length is divided into four intervals: AB, BC, CD, and DE. Results show that interval AB has the lowest 1/Q value, and that interval BC has the highest 1/Q value. The values of 1/Q measured in the CDP stack using the new method are consistent with those measured using the classical spectral ratio method.

  7. Seismic hazard from instrumentally recorded, historical and simulated earthquakes: Application to the Tibet-Himalayan region

    NASA Astrophysics Data System (ADS)

    Sokolov, Vladimir; Ismail-Zadeh, Alik

    2015-08-01

    We present a new approach to assessment of regional seismic hazard, which accounts for observed (instrumentally recorded and historic) earthquakes, as well as for seismic events simulated for a significantly longer period of time than that of observations. We apply this approach to probabilistic seismic hazard analysis (PSHA) for the Tibet-Himalayan region. The large magnitude synthetic events, which are consistent with the geophysical and geodetic data, together with the observed earthquakes are employed for the Monte-Carlo PSHA. Earthquake scenarios for hazard assessment are generated stochastically to sample the magnitude and spatial distribution of seismicity, as well as the distribution of ground motion for each seismic event. The peak ground acceleration values, which are estimated for the return period of 475 yr, show that the hazard level associated with large events in the Tibet-Himalayan region significantly increases if the long record of simulated seismicity is considered in the PSHA. The magnitude and the source location of the 2008 Wenchuan M = 7.9 earthquake are among the range of those described by the seismic source model accepted in our analysis. We analyze the relationship between the ground motion data obtained in the earthquake's epicentral area and the obtained PSHA estimations using a deaggregation technique. The proposed approach provides a better understanding of ground shaking due to possible large-magnitude events and could be useful for risk assessment, earthquake engineering purposes, and emergency planning.

  8. Do faults preserve a record of seismic slip: A second opinion

    NASA Astrophysics Data System (ADS)

    Rowe, Christie D.; Griffith, W. Ashley

    2015-09-01

    Exhumed fault zones offer insights into deformation processes associated with earthquakes in unparalleled spatial resolution; however it can be difficult to differentiate seismic slip from slow or aseismic slip based on evidence in the rock record. Fifteen years ago, Cowan (1999) defined the attributes of earthquake slip that might be preserved in the rock record, and he identified pseudotachylyte as the only reliable indicator of past earthquakes found in ancient faults. This assertion was based on models of frictional heat production (Sibson, 1975, 1986) providing evidence for fast slip. Significant progress in fault rock studies has revealed a range of reaction products which can be used to detect frictional heating at peak temperatures less than the melt temperature of the rock. In addition, features formed under extreme transient stress conditions associated with the propagating tip of an earthquake rupture can now be recognized in the rock record, and are also uniquely seismic. Thus, pseudotachylyte is no longer the only indicator of fossilized earthquake ruptures. We review the criteria for seismic slip defined by Cowan (1999), and we determine that they are too narrow. Fault slip at rates in the range 10-4-101 m/s is almost certainly dynamic. This implies that features reproduced in experiments at rates as low as 10-4 m/s may be indicators of seismic slip. We conclude with a summary of the rock record of seismic slip, and lay out the current challenges in the field of earthquake geology.

  9. Weather-related Ground Motions Recorded by Taiwan Broadband Seismic Network Stations

    NASA Astrophysics Data System (ADS)

    Yang, C. F.; Chi, W. C.

    2014-12-01

    Broadband seismometers record ground motions, which can be induced by weather-related processes. Analyzing such signals might help to better understand those natural processes. Previously, abnormal seismic signals have been detected during rainfall and snowmelt events. The amplitudes of those seismic signals correlated with the variations of the discharge in a nearby river and scientists have proposed that such signals were generated by bed load transport. Here, we used the continuous seismic data from the Broadband Array in Taiwan for Seismology (BATS) to analyze the weather-related ground motions during rainfall events. The sampling rate for seismic data is 100 samples per second. We compared the seismic data with the precipitation data from the rain gauge stations in Taiwan in three select rainfall periods, Typhoon Kalmaegi in 2008, Typhoon Morakot in 2009 and the East Asian rainy season in 2012. During raining, the Power Spectral Density (PSD) of high frequency (> 1 Hz) seismic noises is apparently high, and the amplitude of the seismic noise also correlates with the local precipitation, especially at the stations in the drainage basins, and the PSD decreased gradually after peaks of precipitation. At some seismic stations, we observed vertical ground motions at several bands of frequencies: 0-1 Hz, 1-5 Hz, and 5-45 Hz. However, on horizontal components we found the 5-45 Hz energy splits into two bands: 5-25 Hz and 30-45 Hz. For stations near the ridge tops or on the coastal plain, the 30-45 Hz band energy is weaker or missing. Preliminary results show that the amplitudes of the seismic waves correlate with the stream flow discharge. Next, we plan to study the sources of the different bands of energy to examine if we can monitor and quantify natural processes, like precipitation and river discharge, using seismic signals.

  10. Analysis of seismic noise recorded by temporary seismic array near the Pyhäsalmi underground mine in Finland

    NASA Astrophysics Data System (ADS)

    Afonin, Nikita; Kozlovskaya, Elena; Narkilahti, Janne; Nevalainen, Jouni

    2016-04-01

    The Pyhäsalmi mine is an underground copper and zinc mine located in central Finland. It is one of the oldest and deepest underground mines in Europe, in which ore is excavated from the depth of about 1450 m. Due to the large amount of heavy machinery, the mine itself is a source of strong seismic and acoustic noise. This continuous noise creates a problem for high-resolution active source seismic experiments. That is why in out study we investigated the opportunity to use this seismic noise for studying structure of the uppermost crust. For this we installed 24 3-component DSU-SA MEMS seismic sensors with the autonomous RAUD eX data acquisition units produced by Sercel Ltd. along a 10 km long line crossing the mine area. The array recorded continuous seismic data from 29.10.2013 to 1.11.2013 with the sampling rate of 500 sps. The continuous data for the period 5 days were processed in several steps including single station data analysis, pre-filtering and time-domain stacking. The processed data set was used to estimate empirical Green's functions (EGF) between pairs of stations in the frequency band of 1-100 Hz. We developed our own procedure of stacking EGF in time-domain and, as a result, we were able to extract not only Rayleigh, but also refracted P-waves. Finally, we calculated surface wave dispersion curves and solved inversion problems for surface waves and refracted waves. In our paper we concentrate mainly on details of our data processing routine and its influence on quality of results of EGF extraction. The study is a part of SEISLAB project funded by he European Regional Development Fund (ERDF), Council of Oulu region (Finland) and Pyhäsalmi Mine Oy.

  11. 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.

  12. Unsupervised pattern recognition in continuous seismic wavefield records using Self-Organizing Maps

    NASA Astrophysics Data System (ADS)

    Köhler, Andreas; Ohrnberger, Matthias; Scherbaum, Frank

    2010-09-01

    Modern acquisition of seismic data on receiver networks worldwide produces an increasing amount of continuous wavefield recordings. In addition to manual data inspection, seismogram interpretation requires therefore new processing utilities for event detection, signal classification and data visualization. The use of machine learning techniques automatises decision processes and reveals the statistical properties of data. This approach is becoming more and more important and valuable for large and complex seismic records. Unsupervised learning allows the recognition of wavefield patterns, such as short-term transients and long-term variations, with a minimum of domain knowledge. This study applies an unsupervised pattern recognition approach for the discovery, imaging and interpretation of temporal patterns in seismic array recordings. For this purpose, the data is parameterized by feature vectors, which combine different real-valued wavefield attributes for short time windows. Standard seismic analysis tools are used as feature generation methods, such as frequency-wavenumber, polarization and spectral analysis. We use Self-Organizing Maps (SOMs) for a data-driven feature selection, visualization and clustering procedure. The application to continuous recordings of seismic signals from an active volcano (Mount Merapi, Java, Indonesia) shows that volcano-tectonic and rockfall events can be detected and distinguished by clustering the feature vectors. Similar results are obtained in terms of correctly classifying events compared to a previously implemented supervised classification system. Furthermore, patterns in the background wavefield, that is the 24-hr cycle due to human activity, are intuitively visualized by means of the SOM representation. Finally, we apply our technique to an ambient seismic vibration record, which has been acquired for local site characterization. Disturbing wavefield patterns are identified which affect the quality of Love wave dispersion

  13. SLAMMER: Seismic LAndslide Movement Modeled using Earthquake Records

    USGS Publications Warehouse

    Jibson, Randall W.; Rathje, Ellen M.; Jibson, Matthew W.; Lee, Yong W.

    2013-01-01

    This program is designed to facilitate conducting sliding-block analysis (also called permanent-deformation analysis) of slopes in order to estimate slope behavior during earthquakes. The program allows selection from among more than 2,100 strong-motion records from 28 earthquakes and allows users to add their own records to the collection. Any number of earthquake records can be selected using a search interface that selects records based on desired properties. Sliding-block analyses, using any combination of rigid-block (Newmark), decoupled, and fully coupled methods, are then conducted on the selected group of records, and results are compiled in both graphical and tabular form. Simplified methods for conducting each type of analysis are also included.

  14. Recording and investigation of the seismic signal generated by hypervelocity impact experiments and numerical models

    NASA Astrophysics Data System (ADS)

    Güldemeister, N.; Moser, D.; Wünnemann, K.; Hoerth, T.; Schäfer, F.

    2013-09-01

    Meteorite impacts can cause environmental consequences, one of which is the generation of ground motions that may exceed the magnitude of the largest earthquakes [1]. Impacts generate shock waves that attenuate with distance until they even tually turn into seismic waves. Thus, meteorite impact may be considered as a source for seismic shaking similar to earthquakes. Seismic signals have been recorded in explosion experiments [2] and in hydrocode models of large impact events such as the Chicxulub crater [3]. To determine how much of the kinetic energy Ekin of the impactoris turned into seismic energy Eseis can be investigated experimentally (by recording the acoustic emission) or by numerical models. The ratio of Eseis/Ekin is the so called seismic efficiency k. The seismic efficiency depends on material properties (porosity) and is usually estimated to range between 10-2 and 10-6 [2,4]. In the framework of the "MEMIN" (multidisciplinary experimental and modeling impact crater research network) project a suite of hypervelocity impact experiments on a decimeter scale have been carried out [5]. We use acoustic emission (AE) technique and pressure gauges in high spatiotemporal Meteorite impacts can cause environmental consequences, one of which is the generation of ground motions that may exceed the magnitude of the largest earthquakes [1]. Impacts generate shock waves that attenuate with distance until they even tually turn into seismic waves. Thus, meteorite impact may be considered as a source for seismic shaking similar to earthquakes. Seismic signals have been recorded in explosion experiments [2] and in hydrocode models of large impact events such as the Chicxulub crater [3]. To determine how much of the kinetic energy Ekin of the impactoris turned into seismic energy Eseis can be investigated experimentally (by recording the acoustic emission) or by numerical models. The ratio of Eseis/Ekin is the so called seismic efficiency k. The seismic efficiency depends

  15. Micro-seismicity in Alberta recorded by the Canadian Rockies and Alberta Network

    NASA Astrophysics Data System (ADS)

    Schultz, R.; Gu, Y. J.

    2012-12-01

    Documented seismicity throughout Alberta, Canada has been relatively low in recent history, with fewer than fifteen events (ML > 3.5) recorded by the Geological Survey of Canada (GSC) since 1985. The notable lack of seismicity could be partially attributed to limited or intermittent station coverage in the province. For this reason, the Alberta Geological Survey (AGS) has been involved in a continued effort to maintain, improve and expand regional seismic networks. Broadband seismic data from the Canadian Rockies and Alberta Network (CRANE) and catalog excerpts from the Canadian National Seismic Network (CNSN) were analyzed. Micro-seismic hypocenters were located using Antelope, a software package from Boulder Real Time Technologies, Inc.. Analysis of data from September, 2006 to June, 2010 shows these events are typically naturally occurring or anthropogenic (e.g., mining blasts, which are not usually part of the earthquake catalogs). More than one hundred and twenty natural earthquakes were located in western and central Alberta, with the majority occurring along the Rocky Mountain foothills. During this period, earthquakes magnitudes (ML) ranging from 0.5 to 4.0 were measured and the magnitude of completeness is ~2.8 for this dataset. The substantial number of unreported events suggests that the existing earthquake catalogs, based exclusively on national seismic network stations, are incomplete. The addition of the CRANE dataset has improved the understanding of background seismicity by providing updated hypocenter locations and waveforms of more than thirty previously unrecorded earthquakes. Future endeavors to incorporate data from additional networks would prove invaluable for the identification of emergent trends or induced events.

  16. Performance of an island seismic station for recording T-phases

    SciTech Connect

    Hanson, J. A., LLNL

    1998-05-01

    As part of the International Monitoring System (IMS) a worldwide hydroacoustic network consisting of 6 hydrophone and 5 island seismic stations has been planned which will monitor for underwater or low altitude atmospheric explosions. Data from this network is to be integrated with other IMS networks monitoring the Comprehensive Nuclear Test-Ban Treaty. The seismic (T-phase) stations are significantly less sensitive than hydrophones to ocean borne acoustic waves. T-phase signal strength at seismic stations depends on the amplitude of the signal in the water column, the hydroacoustic-seismic conversion efficiency, and loss on the seismic portion of the path through the island. In order to understand how these factors influence the performance of T-phase stations seismic and hydroacoustic data are examined from instruments currently deployed on or around Ascension Island in the South Atlantic Ocean. T-phase recordings for the last 3 years have been collected from the GSN seismic station ASCN on Ascension Island. Surrounding the island are 5 hydrophones which are part of the U.S. Air Force Missile Impact Locating System (MILS). Data from this system have been obtained for some of the events observed at ASCN. Four of the hydrophones are located within 30 km of the coast while the fifth instrument is 100 km to the south. Amplitude spectral estimates of the signal-to-noise levels (SNL) are computed and generally peak between 3 and 8 Hz for both the seismometer and hydrophone data. The seismic SNL generally decays to 1 between 10 and 15 Hz while the hydrophone SNL is still large well above 20 Hz. The ratios of the hydrophone-to-seismometer SNL, at their peak in energy, range between 10 and 100 (20-40 dB) unless a hydrophone is partially blocked by the Ascension Island landmass.

  17. Deep seismic profiling using off-line recorders, Miura Peninsula, Kanto, Japan.

    NASA Astrophysics Data System (ADS)

    Kawamura, T.; Hirata, N.; Sato, H.; Onishi, M.; Noda, K.

    2003-12-01

    The deep seismic profiling around Metropolitan Tokyo (Kanto area) began from 2002 under the project named . The deep seismic profiling was performed along the Tokyo Bay (Tokyo Bay 2003) from July to August in 2003, to obtain an image of the source fault of the Kanto earthquake of 1923 (M7.9), and deeper extension of inland active faults in Miura Peninsula. In the Tokyo Bay 2003, seismic reflection data were acquired along a 71-km-long seismic line from the Miura Peninsula to Tokyo Bay, using digital-telemetry cable system, including ocean bottom cables. However, this seismic line at Miura Peninsula passes through the densely populated area and due to the cultural noise the low S/N ratio was expected. Keeping away from the noise along the cable-type receiver line, 51 off-line recorders with a 4.5 Hz and 3-compornent geophone were deployed at carefully selected, quiet receiver points. During 90 days continuous recording, seismic signals produced by four vibroseis trucks at 195 locations and air-guns (1500 cu. inch) at 4280 locations were recorded including ca. 150 of earthquakes. Judging from the preliminary receiver gathers, two later phases (A and B) are recognized. The later phase A, located at TWT (Two-way travel time) 4 to 5.5 sec., is interpreted as a reflection from the top of the Philippine Sea Plate. The later phase B at TWT 7 to 8 sec. corresponds to the deeper reflection under the Philippine Sea Plate, respectively.

  18. Mid-continental Seismicity in the U.S. as recorded by the USArray

    NASA Astrophysics Data System (ADS)

    Vernon, F.; Astiz, L.; Martynov, V. G.; Karasu, G.; Tytell, J.; Cox, T. A.; Eakins, J. A.; Newman, R. L.; Reyes, J. C.; Davis, G. A.

    2012-12-01

    In contrast to the seismically well-instrumented Pacific region (i.e. California, Oregon and Washington states), the intercontinental regions of the U.S. have been more sparsely monitored. Thus as the Transportable Array (TA) stations started rolling eastward with its uniform deployment grid, an systematic view of seismic activity in the USArray deployment region became possible. The Array Network Facility (ANF) uses the Antelope environmental monitoring software developed by Boulder Real Time Technologies (BRTT) to acquire and locate seismic events. To maintain a consistent methodology across diverse tectonic regions, the iasp91 velocity model is used for all automatic and analyst reviewed locations. All events are associated with corresponding solutions from available regional network and global seismic bulletins. We note that although about 50% of all events located by the ANF until June 2012 have not been reported by any other regional seismic bulletin, many of these could be quarry blasts that are excluded from published regional network bulletins. The ANF seismic bulletin is complete to Ml ~ 2.0 and does not distinguish between earthquakes and blasts. By analyzing the time of day in which seismic events located by ANF occur, as well as establishing locations of mining operations, we have confirmed that the majority of events in the intermontane plateaus can likely be associated with blasting, mostly of large surface coal and precious metals mines. However, not all events recorded in the intermontane region are blasts. The USArray has recorded felt minor earthquakes in Colorado, Oklahoma, Texas, Arkansas, South Dakota and Ohio as well as the swarms in Yellowstone, Oklahoma and Arkansas. Notable events recorded by the TA are the 2008 Wells Nevada earthquake, the April 2008 Illinois earthquake and the more recently the August 2011 Colorado and the Virginia earthquakes. By far, the most seismically active region in the mid-continental region during the USArray

  19. Seismic reading taken at MSC recording impact of Apollo 13 S-IVB with surface

    NASA Technical Reports Server (NTRS)

    1970-01-01

    A seismic reading taken from instruments at the Manned Spacecraft Center (MSC) recording impact of the Apollo 13 S-IVB/Instrument Unit with lunar surface. The expended Saturn third stage and instrument unit impacted the lunar surface at 7:09 p.m., April 14, 1970. The location of the impact was 2.4 degrees south latitude and 27.9 degrees west longitude, about 76 nautical miles west-northwest of the Apollo 12 Lunar Surface Experiment package deployment site. The S-IVB/IU impact was picked up by the Passive Seismic Experiment, a component of the package and transmitted to instruments at the Mission Control Center.

  20. Development and programming of Geophonino: A low cost Arduino-based seismic recorder for vertical geophones

    NASA Astrophysics Data System (ADS)

    Soler-Llorens, J. L.; Galiana-Merino, J. J.; Giner-Caturla, J.; Jauregui-Eslava, P.; Rosa-Cintas, S.; Rosa-Herranz, J.

    2016-09-01

    The commercial data acquisition systems used for seismic exploration are usually expensive equipment. In this work, a low cost data acquisition system (Geophonino) has been developed for recording seismic signals from a vertical geophone. The signal goes first through an instrumentation amplifier, INA155, which is suitable for low amplitude signals like the seismic noise, and an anti-aliasing filter based on the MAX7404 switched-capacitor filter. After that, the amplified and filtered signal is digitized and processed by Arduino Due and registered in an SD memory card. Geophonino is configured for continuous registering, where the sampling frequency, the amplitude gain and the registering time are user-defined. The complete prototype is an open source and open hardware system. It has been tested by comparing the registered signals with the ones obtained through different commercial data recording systems and different kind of geophones. The obtained results show good correlation between the tested measurements, presenting Geophonino as a low-cost alternative system for seismic data recording.

  1. UK National Data Centre archive of seismic recordings of (presumed) underground nuclear tests 1964-1996

    NASA Astrophysics Data System (ADS)

    Young, John; Peacock, Sheila

    2016-04-01

    The year 1996 has particular significance for forensic seismologists. This was the year when the Comprehensive Test Ban Treaty (CTBT) was signed in September at the United Nations, setting an international norm against nuclear testing. Blacknest, as a long time seismic centre for research into detecting and identifying underground explosions using seismology, provided significant technical advice during the CTBT negotiations. Since 1962 seismic recordings of both presumed nuclear explosions and earthquakes from the four seismometer arrays Eskdalemuir, Scotland (EKA), Yellowknife, Canada (YKA), Gauribidanur, India (GBA), and Warramunga, Australia (WRA) have been copied, digitised, and saved. There was a possibility this archive would be lost. It was decided to process the records and catalogue them for distribution to other groups and institutions. This work continues at Blacknest but the archive is no longer under threat. In addition much of the archive of analogue tape recordings has been re-digitised with modern equipment, allowing sampling rates of 100 rather than 20 Hz.

  2. Processed seismic motion records from St. George, Utah earthquake of September 2, 1992, recorded at seismic stations in southern Nevada

    SciTech Connect

    Lum, P.K.; Honda, K.K.

    1993-04-01

    As part of the contract with the US Department of Energy, Nevada Field Office (DOE/NV), URS/John A. Blume & Associates, Engineers (URS/Blume) maintains a network of seismographs in southern Nevada to monitor the ground motion generated by the underground nuclear explosions (UNEs) at the Nevada Test Site (NTS). The seismographs are located in the communities surrounding the NTS and the Las Vegas valley. When these seismographs are not used for monitoring the UNE generated motions, a limited number of seismographs are maintained for monitoring motion generated by other than UNEs (e.g. motion generated by earthquakes, wind, blast). During the subject earthquake of September 2, 1992, a total of 16 of these systems recorded the earthquake motions. This report contains the recorded data.

  3. The Ocean-Continent Boundary Effect on Seismic Noise Recorded on Land

    NASA Astrophysics Data System (ADS)

    Stutzmann, E.; Gualtieri, L.; Capdeville, Y.; Farra, V.; Mangeney, A.

    2014-12-01

    Seismic noise in the period band 3-10s is generated at the surface of the ocean by the interaction of ocean gravity waves. Noise signal is dominated by Rayleigh waves and is recorded worldwide, both on the ocean seafloor and on continent. Microseismic Rayleigh waves, like any other elastic wave, loose energy when traveling from the ocean to the continent. Thus, the noise records on continent are affected by the propagation of microseismic waves, especially across the boundary between the ocean and the continent, the main structural boundary along the source-receiver path. At the ocean-continent boundary, Rayleigh waves dissipate a significant amount of energy (e.g. McGarr, 1969) and noise Love waves may be generated (e.g. Gregersen, 1977). In order to investigate the effect of the ocean-continent boundary on seismic noise records, we simulate the propagation of the seismic wavefield across the seafloor using the spectral-element method in the secondary microseismic period band (3-10s). A single noise source is located at the surface of the ocean and the signal is recorded at the seafloor, both in deep and shallow ocean regions and on continent. The seismograms computed in a model with continental slope are compared to those computed in a model with flat seafloor, for varying periods and slopes. In the presence of the continental slope, the seismic records are affected by a secondary virtual source, generated by the seafloor topography. The effect of the spatial distribution of noise sources is also investigated.

  4. Seismic recording of small zero frequency displacement from moderate events

    NASA Astrophysics Data System (ADS)

    Pino, Nicola Alessandro; Di Luccio, Francesca

    2005-06-01

    The use of modern broadband seismometers allows the observation of dynamic and static near-field effects. In the fortunate case of the great 1994 Bolivia earthquake a 6 mm coseismic permanent offset was observed at distances of about 600 km. On the other hand no surface static displacement from moderate events has been observed yet. This is mainly due to the intrinsic difficulties in the instrument removal. In the present paper we analyze broadband waveforms from a couple of events in southern Italy, recorded at distance of 50 km, by applying the technique for instrument removal recently introduced by Zhu [2003]. We derive stable and reliable measures of very small coseismic static offset produced by moderate magnitude earthquakes. Our results, successfully tested against synthetic prediction, give permanent displacement of a few tenths of millimeters, one order of magnitude smaller than usual geodetic resolution.

  5. Catalog of seismic records obtained in support of the ERDA/Nevada Operations Office, October 1963 through June 1976

    USGS Publications Warehouse

    Navarro, R.; Sembera, E.D.; Jungblut, W.L.

    1977-01-01

    The United States Geological Survey (USGS), Branch of Earthquake Hazards (BEH), Las Vegas, Nevada has provided ERDA, Nevada Operations Office, with seismic monitoring support to the underground nuclear weapons test program conducted at the Nevada Test Site (NTS) since September 1961. Activities from September 15, 1961 to September 13, 1963 are summarized in the report, "Seismic Dats Summary Nuclear Detonation Program, 1961 thru 1963", (Mickey and Shugart 1964) which lists seismic records obtained from all announced underground nuclear tests conducted during that period.

  6. Seismic and Acoustic Records of the March 2009 Ahwiyah Point Rock Fall, Yosemite Valley, California

    NASA Astrophysics Data System (ADS)

    Zimmer, V.; Stock, G. M.; Sitar, N.

    2009-12-01

    During the winter of 2008-2009, a seismic network was installed in Yosemite Valley for the purpose of rock fall monitoring. The network consisted of several 8 Hz geophones, accelerometers, and infrasound acoustic sensors recorded at sampling rates of 500 and 1000 samples-per-second. On March 28, 2009, at 5:26am, a very large rock fall occurred at Ahwiyah Point, near Half Dome. This rock fall originated near the summit of Ahwiyah Point and fell approximately 600 m, sliding down the steeply (70 degree) dipping cliff face and striking ledges along the way. Rock debris knocked down hundreds of trees and buried 300 meters of the southern portion of the Mirror Lake trail. Detachment and impact seismic signals were recorded by the local seismic network at a distance of 4.4 to 6.8 kilometers, as well as by regional seismic stations up to 400 kilometers away, registering as a local magnitude 2.4 earthquake. The volume of the rock fall is estimated to be ~43,000 cubic meters, the largest to occur in Yosemite Valley in 22 years, a fact reflected in the magnitude of recorded shaking. The detachment portion of the signal represents several weak impacts of the falling rock mass which can be correlated across different stations. The impact portion of the signal contains distinct P and Rayleigh wave phases. The first infrasound signal arrives later than expected to correlate with the first detachment seismic signal. The main acoustic signal correlates well with the main impact. In addition, there is a lower (0.5 Hz) signal that arrives later than the main impact and may be correlated with a small airblast that knocked over trees outside of the debris field. Data collected from this rock fall event provides an important opportunity to evaluate the ability of seismic and acoustic sensors to detect rock falls, learn about the dynamics of rock falls, and explore the mechanisms by which seismic waves are generated during rock fall events and travel locally in mountainous terrain.

  7. Lake sediments as systematic recorders of seismic shaking: potential and limitations

    NASA Astrophysics Data System (ADS)

    Moernaut, Jasper; Van Daele, Maarten; Strasser, Michael; De Batist, Marc

    2013-04-01

    Instrumental and written records of past earthquakes generally do not extend further back in time than a few hundred years. This is often insufficient to provide reliable information on earthquake recurrence patterns, information that is indispensable for a reliable seismic hazard assessment. Seismically-induced sedimentary features have been found in many lake records worldwide. This encompasses features created during and shortly after the earthquake such as in-situ deformations, liquefaction features, sublacustrine landslides, turbidites and subaerial landslides which propagated into the lake. Also, sedimentary imprints of long-term postseismic effects can be present, such as increased sedimentation rates, outburst floods, changes in water level and chemistry, etc. Up to now, only few comparative studies have been conducted to determine in which ways and how reliably lacustrine sediment sequences can register strong seismic shaking. Therefore, effectively quantifing paleo-earthquake parameters such as magnitude, rupture type and location based on lacustrine sedimentary archives remains a challenging task. Here, we present a comparative overview of relatively recent studies on earthquake-induced sedimentary features in different types of modern lakes in different tectonic settings and discuss the criteria used to single out earthquake shaking as their causative mechanism. Landslide records in Switzerland and turbidite records in Chile and Japan pointed out that the occurrence and/or scale of subaquatic slope failures can correlate with seismic intensity. It also seems that the continuity and type of the paleoseismic record is strongly dependent on lithology, sedimentation rate and slope morphology within the lake basins. Especially in settings with high frequency of strong earthquakes, this can lead to an underrepresentation of paleoseismic events in the records. However, for lake systems which exhibit ideal characteristics, a single coring site can be sufficient

  8. Large-explosive source, wide-recording aperture, seismic profiling on the Columbia Plateau, Washington

    SciTech Connect

    Jarchow, C.M. . Dept. of Geophysics); Catchings, R.D.; Lutter, W.J. )

    1994-02-01

    Clear subsurface seismic images have been obtained at low cost on the Columbia Plateau, Washington. The Columbia Plateau is perhaps the most notorious of all bad-data'' areas because large impedance contrasts in surface flood basalts severely degrade the seismic wavefield. This degradation was mitigated in this study via a large-explosive source, wide-recording aperture shooting method. The shooting method emphasizes the wide-angle portion of the wavefield, where Fermat's principle guarantees reverberation will not interfere with the seismic manifestations of crucial geologic interfaces. The basalt diving wave, normally discarded in standard common midpoint (CMP) seismic profiling, can be used to image basalt velocity structure via travel-time inversion. Maximum depth-penetration of the diving wave tightly constrains basalt-sediment interface depth. An arrival observed only at shot-receiver offsets greater than 15 km can be used to determine the velocity and geometry of basement via simultaneous inversion. The results from this study suggest that previous geologic hypotheses and hydrocarbon play concepts for the Columbia Plateau may have been in error.

  9. Seismic interferometry by multidimensional deconvolution applied to ambient noise recorded in Malargüe, Argentina

    NASA Astrophysics Data System (ADS)

    Weemstra, Cornelis; Draganov, Deyan; Ruigrok, Elmer; Wapenaar, Kees; Gomez, Martin

    2016-04-01

    Seismic interferometry refers to the principle of generating new responses. These new responses are conventionally obtained by simple crosscorrelation of recordings made by separate receivers: a first receiver acts as `virtual source' whose response is retrieved at the other receivers. The recorded wavefields may be passive (e.g. seismic noise) or active (e.g. in an industrial context). The newly retrieved responses can be used to extract receiver-receiver phase velocities, which often serve as input parameter for tomographic inverse problems. More recently, the coda of the newly retrieved responses have been found to correlate with temporally varying parameters such as hydrocarbon production and precipitation. For all applications, however, the accuracy of the retrieved responses is of great importance. Irregularities in the illumination patttern often degrade this accuracy: correct response retrieval relies on a uniform illumination of the receivers. Reformulating the theory underlying seismic interferometry by crosscorrelation as a multidimensional deconvolution (MDD) process, allows the removal of the imprint of the illumination pattern on the retrieved responses by means of a so-called point-spread function (PSF). We use a seismic array in Malargüe, Argentina, to assess the feasibility of SI by MDD on ambient seismic noise recordings. The array, which has an aperture of approximately 60 km, is located just east of the Andean mountain range. The shape of the array lends itself well for the application of SI by MDD: its T-shape allows the construction of a PSF along one of the two receiver lines. These receivers act as the virtual sources and their responses are retrieved by the receivers along the other (perpendicular) line of receivers. A frequency-dependent analysis of the slowness along both lines allows us to select time windows during which most ambient seismic surface waves propagate in a favorable direction, that is, traversing the line of virtual

  10. Impact of wind on ambient noise recorded by seismic array in northern Poland

    NASA Astrophysics Data System (ADS)

    Lepore, Simone; Markowicz, Krzysztof; Grad, Marek

    2016-03-01

    Seismic interferometry and beam-forming techniques were applied to the ambient noise recorded during January 2014 at the "13 BB star" array composed of thirteen seismic stations located in northern Poland. The circular and symmetric geometry of the array allowed the evaluation of the azimuths of noise sources and the velocities of recovered surface waves with a good reliability. After having pre-processed the raw records of the ambient noise in time- and frequency-domain, we studied the associated power spectral density to identify the frequency bands suitable for the recovery of the surface waves. Then the crosscorrelation was performed between all the station pairs of the array to retrieve the Green's function, from which the velocity range of the surface waves can be determined. Making use of that analysis, the direction of the noise wavefield was linked to the maximum amplitude of the beam-power, estimated by the mixing in the frequency-domain of all the corresponding noise records. The results were related day by day to the mean wind velocity around Europe at 10 m above ground level obtained from global surveys carried out during the same month. Significant correlation between the direction of maximum beam-power associated to the ambient noise recorded at "13 BB star" and the average wind velocity was found.

  11. Recordings from the deepest borehole in the New Madrid Seismic Zone

    USGS Publications Warehouse

    Wang, Z.; Woolery, E.W.

    2006-01-01

    The recordings at the deepest vertical strong-motion array (VSAS) from three small events, the 21 October 2004 Tiptonville, Tennessee, earthquake; the 10 February 2005 Arkansas earthquake; and the 2 June 2005 Ridgely, Tennessee, earthquake show some interesting wave-propagation phenomena through the soils: the S-wave is attenuated from 260 m to 30 m depth and amplified from 30 m to the surface. The S-wave arrival times from the three events yielded different shear-wave velocity estimates for the soils. These different estimates may be the result of different incident angles of the S-waves due to different epicentral distances. The epicentral distances are about 22 km, 110 km, and 47 km for the Tiptonville, Arkansas, and Ridgely earthquakes, respectively. These recordings show the usefulness of the borehole strong-motion array. The vertical strong-motion arrays operated by the University of Kentucky have started to accumulate recordings that will provide a database for scientists and engineers to study the effects of the near-surface soils on the strong ground motion in the New Madrid Seismic Zone. More information about the Kentucky Seismic and Strong-Motion Network can be found at www.uky.edu/KGS/geologichazards. The digital recordings are available at ftp://kgsweb.uky.edu.

  12. Impact of wind on ambient noise recorded by seismic array in northern Poland

    NASA Astrophysics Data System (ADS)

    Lepore, Simone; Markowicz, Krzysztof; Grad, Marek

    2016-06-01

    Seismic interferometry and beam-forming techniques were applied to the ambient noise recorded during January 2014 at the `13 BB star' array composed of thirteen seismic stations located in northern Poland. The circular and symmetric geometry of the array allowed the evaluation of the azimuths of noise sources and the velocities of recovered surface waves with a good reliability. After having pre-processed the raw records of the ambient noise in time- and frequency-domain, we studied the associated power spectral density to identify the frequency bands suitable for the recovery of the surface waves. Then the cross-correlation was performed between all the station pairs of the array to retrieve the Green's function, from which the velocity range of the surface waves can be determined. Making use of that analysis, the direction of the noise wavefield was linked to the maximum amplitude of the beam-power, estimated by the mixing in the frequency-domain of all the corresponding noise records. The results were related day by day to the mean wind velocity around Europe at 10 m above ground level obtained from global surveys carried out during the same month. Significant correlation between the direction of maximum beam-power associated to the ambient noise recorded at `13 BB star' and the average wind velocity was found.

  13. Calibration Shots Recorded for the Salton Seismic Imaging Project, Salton Trough, California

    NASA Astrophysics Data System (ADS)

    Murphy, J. M.; Rymer, M. J.; Fuis, G. S.; Stock, J. M.; Goldman, M.; Sickler, R. R.; Miller, S. A.; Criley, C. J.; Ricketts, J. W.; Hole, J. A.

    2009-12-01

    The Salton Seismic Imaging Project (SSIP) is a collaborative venture between the U.S. Geological Survey, California Institute of Technology, and Virginia Polytechnic Institute and State University, to acquire seismic reflection/wide angle refraction data, and currently is scheduled for data acquisition in 2010. The purpose of the project is to get a detailed subsurface 3-D image of the structure of the Salton Trough (including both the Coachella and Imperial Valleys) that can be used for earthquake hazards analysis, geothermal studies, and studies of the transition from ocean-ocean to continent-continent plate-boundary. In June 2009, a series of calibration shots were detonated in the southern Imperial Valley with specific goals in mind. First, these shots were used to measure peak particle velocity and acceleration at various distances from the shots. Second, the shots were used to calibrate the propagation of energy through sediments of the Imperial Valley. Third, the shots were used to test the effects of seismic energy on buried clay drainage pipes, which are abundant throughout the irrigated parts of the Salton Trough. Fourth, we tested the ODEX drilling technique, which uses a down-hole casing hammer for a tight casing fit. Information obtained from the calibration shots will be used for final planning of the main project. The shots were located in an unused field adjacent to Hwy 7, about 6 km north of the U.S. /Mexican border (about 18 km southeast of El Centro). Three closely spaced shot points (16 meters apart) were aligned N-S and drilled to 21-m, 23.5-m, and 27-m depth. The holes were filled with 23-kg, 68-kg, and 123-kg of ammonium-nitrate explosive, respectively. Four instrument types were used to record the seismic energy - six RefTek RT130 6-channel recorders with a 3-component accelerometer and a 3-component 2-Hz velocity sensor, seven RefTek RT130 3-channel recorders with a 3-component 4.5-Hz velocity sensor, 35 Texans with a vertical component 4

  14. Reducing magnetic field induced noise in broad-band seismic recordings

    NASA Astrophysics Data System (ADS)

    Forbriger, Thomas

    2007-04-01

    Seismic broad-band sensors are known to be sensitive to the magnetic field. Magnetic storms and man-made disturbances of the magnetic field can produce significant noise in seismic recordings. I show that variations in the magnetic field translate directly into apparent acceleration of the seismic sensor within the period range from 60 to 1200s for all leaf-spring sensors under investigation. For a Streckeisen STS-1V this is shown even for periods down to 1s. The sensitivity is quantified in magnitude and direction. Both are quite stable over many time windows and signal periods. The sensitivities obtained by linear regression of the acceleration signal on magnetic field recordings during a magnetic storm can effectively be applied to reduce noise in seismic signals. The sensitivity varies in magnitude from sensor to sensor but all are in the range from 0.05 to 1.2ms-2T-1. Seismograms from sensors at Black Forest Observatory (BFO) and stations of the German Regional Seismic Network were investigated. Although these are mainly equipped with leaf-spring sensors, the problem is not limited to this type of instrument. The effect is not observable on the horizontal component STS-1s at BFO while it is significant in the recordings of the vertical STS-1. The main difference between these instruments is the leaf-spring suspension in the vertical component that appears to be the source of the trouble. The suspension springs are made of temperature compensated Elinvar alloys that inherently are ferromagnetic and may respond to the magnetic field in various ways. However, the LaCoste Romberg ET-19 gravimeter at BFO, which uses this material too, does not respond to magnetic storms at a similar magnitude neither do the Invar-wire strainmeters. An active shielding, composed of three Helmholtz coils and a feedback system, is installed at station Stuttgart and provides an improvement of signal-to-noise ratio by almost a factor of 20 at this particular station. The passive

  15. Factors limiting the sensitivity and dynamic range of a seismic system employing analog magnetic tape recording and a seismic amplifier with adjustable gain settings and several output levels

    USGS Publications Warehouse

    Eaton, Jerry P.; Van Schaack, John R.

    1977-01-01

    In the course of modernizing the low-speed-tape-recorder portable seismic systems and considering the possibilities for the design of a cassette-tape-recorder seismic refraction system, the factors that limit the sensitivity and dynamic range of such systems have been reviewed. These factors will first be stated briefly, and then their influence on systems such as the new 5-day-tape seismic system will be examined in more detail. To fix ideas, we shall assume that the system consists of the following elements: 1. A seismic sensor: usually a moving coil inertial seismometer with a period of about 1 second, a coil resistance of about 5000 ohms, and an effective motor constant of 1.0 V/cm/sec (across a 10K load terminating the seismometer sensitivity-and-damping-adjustment resistive network). 2. A seismic amplifier/voltage controlled oscillator unit made up of the following components: a) A fixed gain preamplifier with an input resistance of 10K and an internal noise level of 0.5 muVpp referred to the preamp input (0.1 Hz <= freq. <= 30 hz). b) An adjustable gain (0 to 42 db in 6 db steps) intermediate amplifier c) One or more fixed gain output amplifiers. d) Two sections of 6 db/octave bandpass filter serving to couple the 3 amplifier stages together. e) Voltage controlled oscillators for each output amplifier to produce modulated FM carriers for recording on separate tape tracks or modulated FM subcarriers for subsequent multiplexing and direct recording on tape in the California Network format. 3. An analog magnetic tape recorder: e.g. the PI 5100 (15/80 ips recording in the FM mode or in the direct mode with the 'broad-band' variant-of the Cal Net multiplex system, or 15/16 ips recording in the direct mode with the standard Cal Net multiplex system), or the Sony TC-126 cassette recorder operating in the direct record mode with the standard Cal Net multiplex system. 4. Appropriate magnetic tape playback equipment: e.g., the Bell and Howell 3700-B for the PI-5100 or

  16. Recording of remote ground explosions in the Barents Region by the Seismic &Infrasound Integrated Array "Apatity"

    NASA Astrophysics Data System (ADS)

    Vinogradov, Y.; Vinogradov, A.

    2003-04-01

    Since 1996, Kola Regional Seismological Centre (KRSC) has been engaged in infrasonic research and development. As part of this effort, a small-aperture microbarographic array was installed in conjunction with the seismic array near lake Imandra in the Kola Peninsula; the digitised data are transmitted in real time to the Processing Centre in Apatity; a data processing includes frequency-wavenumber analysis of the array recordings, estimation of phase velocity and azimuth, and evaluation of group velocity based on travel time calculations. The whole system was named the Seismic and InfraSound Integrated Array (SISIA) "Apatity". We present some examples of coupled recordings for selected events in the Kola Peninsula and adjacent regions. Explosions at large mines in the Barents region are routinely detected by the seismic systems installed in northern Fennoscandia and NW Russia. Seismic and infrasound emission from Khibiny, Pechenga, Kovdor and Olenegorsk mines in the Murmansk County are recording by SISIA "Apatity", and the presented 19 reference records show a high sensitivity of the system and a good accuracy for localisation of events within distance range of 30 to 220 km. A capability of the SISIA for detection of events in a remote zone (more than 220 km) was evaluated in case study performed in September 04 - 09, 2002. A set of explosions caused by ammunition demolition in Northern Finland, at a distance of 300 km from the array, have been successfully recorded in Apatity. Three separate phase arrivals for each of five events were identified as follows: the Tropospheric arrival (Iw), the Stratospheric arrival (Is) and the Thermospheric arrival (It). Was found, that all 15 estimates of azimuth are very consistent, ranging from 278 to 288 degrees (true azimuth is 284 degrees). The observed group velocities (average travel velocities) range between 326-336 m/s for the Iw arrival, 300-305 m/s for the Is arrival and 244-254 m/s for the It arrival. The phase

  17. The CSMS (Configurable Seismic Monitoring System) Poorboy deployment: Seismic recording in Pinedale, Wyoming, of the Bullion NTS (Nevada Test Site) nuclear test under the verification provisions of the new TTBT protocol

    SciTech Connect

    Harben, P.E.; Rock, D.W.; Carlson, R.C.

    1990-07-10

    The Configurable Seismic Monitoring System (CSMS), developed at the Lawrence Livermore National Laboratory (LLNL) was deployed in a 13-m deep vault on the AFTAC facility at Pinedale, Wyoming to record the Bullion nuclear test. The purpose of the exercise was to meet all provisions of the new TTBT protocol on in-country seismic recording at a Designated Seismic Station (DSS). The CSMS successfully recorded the Bullion event consistent with and meeting all requirements in the new treaty protocol. In addition, desirable seismic system features not specified in the treaty protocol were determined; treaty protocol ambiguities were identified, and useful background noise recordings at the Pinedale site were obtained. 10 figs.

  18. Empirical analysis of seismic records for eleven nuclear tests at the Nevada Test Site

    SciTech Connect

    Younker, J.L.; Springer, D.L.; Vergino, E.S.

    1982-08-09

    Regional seismic records for eleven underground nuclear explosions were processed and analyzed (empirically) in a search for source and path related patterns in the signals. These nuclear tests were conducted between August, 1979 and April, 1980; all were located in Yucca Flat at the Nevada Test Site (NTS). The seismic signals generated by these explosions were recorded on the LLNL four-station network, located at distances of 200 to 400 km from the NTS. Amplitudes were measured for consistently recorded vertical component body waves, and for vertical and transverse components of surface waves. Correlation between phase amplitudes was statistically determined, and amplitude ratios were compared for four stations for the same event, and at a single station for the complete set of events. Previous studies have shown that certain amplitude ratios are relatively unaffected by the size of the explosion but sensitive to propagation effects. For this set of events, we do not find a statistically significant change in the ratio of Pg:Lg due to different propagation paths to the four stations. We do, however, find increased variability in the amplitude measurements for the smaller events in the population considered in this study.

  19. Lotung large-scale seismic test strong motion records. Volume 1, General description: Final report

    SciTech Connect

    Not Available

    1992-03-01

    The Electric Power Research Institute (EPRI), in cooperation with the Taiwan Power Company (TPC), constructed two models (1/4 scale and 1/12 scale) of a nuclear plant concrete containment structure at a seismically active site in Lotung, Taiwan. Extensive instrumentation was deployed to record both structural and ground responses during earthquakes. The experiment, generally referred to as the Lotung Large-Scale Seismic Test (LSST), was used to gather data for soil-structure interaction (SSI) analysis method evaluation and validation as well as for site ground response investigation. A number of earthquakes having local magnitudes ranging from 4.5 to 7.0 have been recorded at the LSST site since the completion of the test facility in September 1985. This report documents the earthquake data, both raw and processed, collected from the LSST experiment. Volume 1 of the report provides general information on site location, instrument types and layout, data acquisition and processing, and data file organization. The recorded data are described chronologically in subsequent volumes of the report.

  20. Earthquake recordings from the 2002 Seattle Seismic Hazard Investigation of Puget Sound (SHIPS), Washington State

    USGS Publications Warehouse

    Pratt, Thomas L.; Meagher, Karen L.; Brocher, Thomas M.; Yelin, Thomas; Norris, Robert; Hultgrien, Lynn; Barnett, Elizabeth; Weaver, Craig S.

    2003-01-01

    This report describes seismic data obtained during the fourth Seismic Hazard Investigation of Puget Sound (SHIPS) experiment, termed Seattle SHIPS . The experiment was designed to study the influence of the Seattle sedimentary basin on ground shaking during earthquakes. To accomplish this, we deployed seismometers over the basin to record local earthquakes, quarry blasts, and teleseisms during the period of January 26 to May 27, 2002. We plan to analyze the recordings to compute spectral amplitudes at each site, to determine the variability of ground motions over the basin. During the Seattle SHIPS experiment, seismometers were deployed at 87 sites in a 110-km-long east-west line, three north-south lines, and a grid throughout the Seattle urban area (Figure 1). At each of these sites, an L-22, 2-Hz velocity transducer was installed and connected to a REF TEK Digital Acquisition System (DAS), both provided by the Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL) of the Incorporated Research Institutes for Seismology (IRIS). The instruments were installed on January 26 and 27, and were retrieved gradually between April 18 and May 27. All instruments continuously sampled all three components of motion (velocity) at a sample rate of 50 samples/sec. To ensure accurate computations of amplitude, we calibrated the geophones in situ to obtain the instrument responses. In this report, we discuss the acquisition of these data, we describe the processing and merging of these data into 1-hour long traces and into windowed events, we discuss the geophone calibration process and its results, and we display some of the earthquake recordings.

  1. Mapping the sources of the seismic wave field at Kilauea volcano, Hawaii, using data recorded on multiple seismic Antennas

    USGS Publications Warehouse

    Almendros, J.; Chouet, B.; Dawson, P.; Huber, Caleb G.

    2002-01-01

    Seismic antennas constitute a powerful tool for the analysis of complex wave fields. Well-designed antennas can identify and separate components of a complex wave field based on their distinct propagation properties. The combination of several antennas provides the basis for a more complete understanding of volcanic wave fields, including an estimate of the location of each individual wave-field component identified simultaneously by at least two antennas. We used frequency-slowness analyses of data from three antennas to identify and locate the different components contributing to the wave fields recorded at Kilauea volcano, Hawaii, in February 1997. The wave-field components identified are (1) a sustained background volcanic tremor in the form of body waves generated in a shallow hydrothermal system located below the northeastern edge of the Halemaumau pit crater; (2) surface waves generated along the path between this hydrothermal source and the antennas; (3) back-scattered surface wave energy from a shallow reflector located near the southeastern rim of Kilauea caldera; (4) evidence for diffracted wave components originating at the southeastern edge of Halemaumau; and (5) body waves reflecting the activation of a deeper tremor source between 02 hr 00 min and 16 hr 00 min Hawaii Standard Time on 11 February.

  2. Detecting Seismic Signatures in the Rock Record at the Japan Trench

    NASA Astrophysics Data System (ADS)

    Rabinowitz, H. S.; Savage, H. M.; Polissar, P. J.; Plank, T. A.; Rowe, C. D.; Kirkpatrick, J. D.

    2014-12-01

    IODP Expedition 343 (JFAST) drilled through the plate boundary at the Japan Trench where potentially several megathrust earthquakes have occurred, most recently the 2011 Mw 9.1 Tohoku-oki earthquake. Here, we investigate structural features of the plate boundary at the JFAST site to determine their seismic history. Using trace element geochemistry as a tool to fingerprint sedimentary units, we develop a stratigraphy of the JFAST core that shows significant plate boundary complexity. To determine the seismic history of the faults identified in the core, we use a novel method to detect temperature rise along faults: the thermal destruction of organic molecules. We interpret the destruction of alkenones, a common biomarker found in marine sediments, along faults to be a result of coseismic heating. In order to constrain initial alkenone concentration, we use our trace element stratigraphy to correlate individual JFAST samples with their protolith in the DSDP Site 436 reference core. We find that at least three faults demonstrate significant destruction of alkenones, implying that these faults have experienced shallow seismic slip. In the past, frictional work has been difficult to measure on faults due to a paucity of available coseismic temperature proxies preserved in the rock record. By coupling experimentally determined reaction kinetics of alkenone destruction with models of temperature rise during earthquakes, we convert the alkenone destruction measurements into estimates of maximum temperature rise on faults in the JFAST core. This novel measurement allows us to explore energy budgets at the subduction interface.

  3. Composition and variation of noise recorded at the Yellowknife Seismic Array, 1991-2007

    USGS Publications Warehouse

    Koper, K.D.; De Foy, B.; Benz, H.

    2009-01-01

    We analyze seismic noise recorded on the 18 short-period, vertical component seismometers of the Yellowknife Seismic Array (YKA). YKA has an aperture of 23 km and is sited on cratonic lithosphere in an area with low cultural noise. These properties make it ideal for studying natural seismic noise at periods of 1-3 s. We calculated frequency-wave number spectra in this band for over 6,000 time windows that were extracted once per day for 17 years (1991-2007). Slowness analysis reveals a rich variety of seismic phases originating from distinct source regions: Rg waves from the Great Slave Lake; Lg waves from the Atlantic, Pacific, and Arctic Oceans; and teleseismic P waves from the north Pacific and equatorial mid-Atlantic regions. The surface wave energy is generated along coastlines, while the body wave energy is generated at least in part in deep-water, pelagic regions. Surface waves tend to dominate at the longer periods and, just as in earthquake seismograms, Lg is the most prominent arrival. Although the periods we study are slightly shorter than the classic double-frequency microseismic band of 4-10 s, the noise at YKA has clear seasonal behavior that is consistent with the ocean wave climate in the Northern Hemisphere. The temporal variation of most of the noise sources can be well fit using just two Fourier components: yearly and biyearly terms that combine to give a fast rise in microseismic power from mid-June through mid-October, followed by a gradual decline. The exception is the Rg energy from the Great Slave Lake, which shows a sharp drop in noise power over a 2-week period in November as the lake freezes. The L g noise from the east has a small but statistically significant positive slope, perhaps implying increased ocean wave activity in the North Atlantic over the last 17 years. Copyright 2009 by the American Geophysical Union.

  4. Processed seismic motion records from earthquakes (1982--1993): Recorded at Scotty`s Castle, California

    SciTech Connect

    Lum, P.K.; Honda, K.K.

    1993-10-01

    As part of the contract with the US Department of Energy, Nevada Operations Office (DOE/NV), URS/John A. Blume & Associates, Engineers (URS/Blume) maintained a network of seismographs to monitor the ground motion generated by the underground nuclear explosions (UNEs) at the Nevada Test Site (NTS). The seismographs were located in the communities surrounding the NTS and the Las Vegas valley. When these seismographs were not used for monitoring the UNE generated motions, a limited number of seismographs were maintained for monitoring motion generated by other than UNEs (e.g. motion generated by earthquakes, wind, blast). Scotty`s Castle was one of the selected earthquake monitoring station. During the period from 1982 through 1993, numerous earthquakes with varied in magnitudes and distances were recorded at Scotty`s Castle. The records from 24 earthquakes were processed and included in this report. Tables 1 and 2 lists the processed earthquakes in chronological order and in the order of epicentral distances, respectively. Figure 1 shows these epicenters and magnitudes. Due to the potential benefit of these data for the scientific community, DOE/NV and the National Park Service authorize the release of these records.

  5. Processed seismic motion records from earthquakes, 1982-1993: Recorded at Scotty's Castle, California

    NASA Astrophysics Data System (ADS)

    Lum, P. K.; Honda, K. K.

    1993-10-01

    As part of the contract with the US Department of Energy, Nevada Operations Office (DOE/NV), URS/John A. Blume & Associates, Engineers (URS/Blume) maintained a network of seismographs to monitor the ground motion generated by the underground nuclear explosions (UNE's) at the Nevada Test Site (NTS). The seismographs were located in the communities surrounding the NTS and the Las Vegas valley. When these seismographs were not used for monitoring the UNE generated motions, a limited number of seismographs were maintained for monitoring motion generated by other than UNE's (e.g. motion generated by earthquakes, wind, blast). Scotty's Castle was one of the selected earthquake monitoring stations. During the period from 1982 through 1993, numerous earthquakes which varied in magnitudes and distances were recorded at Scotty's Castle. The records from 24 earthquakes were processed and included in this report. The processed earthquakes are listed in chronological order and in the order of epicentral distances, respectively. These epicenters and magnitudes are shown. Due to the potential benefit of these data for the scientific community, DOE/NV and the National Park Service authorize the release of these records.

  6. Basin-scale Green's functions from the ambient seismic field recorded by MeSO-net stations

    NASA Astrophysics Data System (ADS)

    Viens, Loïc.; Koketsu, Kazuki; Miyake, Hiroe; Sakai, Shin'ichi; Nakagawa, Shigeki

    2016-04-01

    Seismic waves propagating through the Earth can be significantly affected by velocity structures such as sedimentary basins. We investigate the propagation characteristics of seismic waves across the Kanto basin, Japan, using Green's functions extracted from the ambient seismic field. We use two stations situated on the eastern and southern edges of the basin as virtual sources, and approximately 420 stations, which are mainly a part of the Metropolitan Seismic Observation network (MeSO-net), as receivers. Using seismometers aligned along two straight lines with the virtual sources, we find that several types of waves can be recovered, each with different sensitivities to the layers that compose the basin. We also show that after amplitude calibration, the extracted Green's functions can accurately simulate the seismic waves of two moderate Mw 4-5 shallow earthquakes that occurred close to the virtual sources. Furthermore, we find that the distribution of the 5% damped pseudovelocity response at a period of 6 s computed from the records of each event and the Green's function waveforms have similar amplification patterns. This study supports the fact that dense networks recording continuously the ambient seismic field in metropolitan areas can be used to accurately assess seismic hazard at high spatial resolution.

  7. Seismic and acoustic recordings of an unusually large rockfall at Mount St. Helens, Washington

    USGS Publications Warehouse

    Moran, S.C.; Matoza, R.S.; Garces, M.A.; Hedlin, M.A.H.; Bowers, D.; Scott, W.E.; Sherrod, D.R.; Vallance, J.W.

    2008-01-01

    On 29 May 2006 a large rockfall off the Mount St. Helens lava dome produced an atmospheric plume that was reported by airplane pilots to have risen to 6,000 m above sea level and interpreted to be a result of an explosive event. However, subsequent field reconnaissance found no evidence of a ballistic field, indicating that there was no explosive component. The rockfall produced complex seismic and infrasonic signals, with the latter recorded at sites 0.6 and 13.4 km from the source. An unusual, very long-period (50 s) infrasonic signal was recorded, a signal we model as the result of air displacement. Two high-frequency infrasonic signals are inferred to result from the initial contact of a rock slab with the ground and from interaction of displaced air with a depression at the base of the active lava dome. Copyright 2008 by the American Geophysical Union.

  8. Detection and identification of seismic signals recorded at Krakatau volcano (Indonesia) using artificial neural networks

    NASA Astrophysics Data System (ADS)

    Ibs-von Seht, M.

    2008-10-01

    The Anak Krakatau volcano (Indonesia) has been monitored by a multi-parametric system since 2005. A variety of signal types can be observed in the records of the seismic stations installed on the island volcano. These include volcano-induced signals such as LP, VT, and tremor-type events as well as signals not originating from the volcano such as regional tectonic earthquakes and transient noise signals. The work presented here aims at the realization of a system that automatically detects and identifies the signals in order to estimate and monitor current activity states of the volcano. An artificial neural network approach was chosen for the identification task. A set of parameters was defined, describing waveform and spectrogram properties of events detected by an amplitude-ratio-based (STA/LTA) algorithm. The parameters are fed into a neural network which is, after a training phase, able to generalize input data and identify corresponding event types. The success of the identification depends on the network architecture and training strategy. Several tests have been performed in order to determine appropriate network layout and training for the given problem. The performance of the final system is found to be well suited to get an overview of the seismic activity recorded at the volcano. The reliability of the network classifier, as well as general drawbacks of the methods used, are discussed.

  9. Hydrological signatures on seismic and strain records at the Canfranc Underground Laboratory (Central Pyrenees).

    NASA Astrophysics Data System (ADS)

    Diaz, Jordi; Crescentini, Luca; Ruiz, Mario; Amoruso, Antonella; Gallart, Josep

    2013-04-01

    , even if its characterization is more difficult. Strain data provided by the high-resolution laser strainmeters is available for one main episode and some of the shorter ones. A clearly anomalous strain has been identified in all the checked cases, coincident in time with the anomalous seismic signal. This coincidence allows discarding a possible origin related to any kind of instrumental malfunction. It is well know that even light rain produces large signals in deformation instruments located at superficial or very shallow levels. Even in interferometers located at large depths (as in Grand Sasso), deformation changes related to long-term changes in the aquifer have been identified. Therefore, we estimate that underground water may be related to the observed signals also in this case. We have reviewed data from a close meteorological station, founding a correlation between periods of heavy rain and the presence of a high level of noise in the 2-10 Hz seismic band. Anomalous deformation changes have also been recorded during most rainy days in the strainmeters. It seems clear that the observed signal does not correspond to water flooding in nearby rivers or creeks, as its frequency content is very narrow. Mechanisms related to changes in fluid-filled cracks have been proposed by Chouet (1988, 1996) to explain similar tremor-like signals. Those models have been originally proposed in volcanic settings, but have also been applied to areas with hydrothermal circulation or in passive margins. In our geological setting, the seismic and strain signals may be generated by changes of pressure in nearby fractured rocks due to water percolation after heavy rain periods. However, those hypotheses must still be taken with care as further theoretical and observational work is clearly needed.

  10. Seismicity in 2010 and major earthquakes recorded and located in Costa Rica from 1983 until 2012, by the local OVSICORI-UNA seismic network

    NASA Astrophysics Data System (ADS)

    Ronnie, Q.; Segura, J.; Burgoa, B.; Jimenez, W.; McNally, K. C.

    2013-05-01

    This work is the result of the analysis of existing information in the earthquake database of the Observatorio Sismológico y Vulcanológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), and seeks disclosure of basic seismological information recorded and processed in 2010. In this year there was a transition between the software used to record, store and locate earthquakes. During the first three months of 2010, we used Earthworm (http://folkworm.ceri.memphis.edu/ew-doc), SEISAN (Haskov y Ottemoller, 1999) and Hypocenter (Lienert y Haskov, 1995) to capture, store and locate the earthquakes, respectively; in April 2010, ANTELOPE (http://www.brtt.com/software.html) start to be used for recording and storing and GENLOC (Fan at al, 2006) and LOCSAT (Bratt and Bache 1988), to locate earthquakes. GENLOC was used for local events and LOCSAT for regional and distant earthquakes. The local earthquakes were located using the 1D velocity model of Quintero and Kissling (2001) and for regional and distant earthquakes IASPEI91 (Kennett and Engdahl, 1991) was used. All the events for 2010 and shown in this work were rechecked by the authors. We located 3903 earthquakes in and around Costa Rica and 746 regional and distant seismic events were recorded (see Figure 1). In this work we also give a summary of major earthquakes recorded and located by OVSICORI-UNA network between 1983 and 2012. Seismicity recorded by OVSICORI-UNA network in 2010

  11. Estimation of azimuthal anisotropy in the NW Pacific from seismic ambient noise in seafloor records

    NASA Astrophysics Data System (ADS)

    Takeo, Akiko; Forsyth, Donald W.; Weeraratne, Dayanthie S.; Nishida, Kiwamu

    2014-10-01

    We analysed background surface waves in seismic ambient noise by cross-correlating continuous records of eight ocean bottom seismometers and nine differential pressure gauges deployed in the northwestern Pacific Ocean by the PLATE project. After estimating the clock delay and instrumental phase responses of differential pressure gauges by using cross-correlation functions, we measured average phase velocities in the area of the array for the fundamental-, first higher- and second higher-mode Rayleigh waves, and the fundamental-mode Love waves at a period range of 3-40 s by waveform fitting. We then measured phase-velocity anomalies of fundamental-mode and first higher-mode Rayleigh waves for each pair of stations at a period range of 5-25 s, and corrected the effect of variation in water-depths. The seismic anomalies imply the presence of strong azimuthal anisotropy beneath the eastern part of array. The direction of maximum velocity is approximately N35°E in the fossil seafloor spreading direction perpendicular to magnetic lineations from the ancient triple junction at this location. The peak-to-peak intensity of shear-wave velocity anisotropy in the mantle is ˜7 per cent.

  12. Infrasound and seismic signals from Baikonur spaceport rocket launches recorded by Kazakh stations

    NASA Astrophysics Data System (ADS)

    Smirnov, Alexandr; Sokolova, Inna; Mikhailova, Natalya

    2015-04-01

    The monitoring network of the Institute of Geophysical Researches, Kazakhstan consists of 2 infrasound arrays, 8 seismic arrays and 7 3C stations. 5 of these stations are a part of IMS CTBTO. The Institute of Geophysical Researches monitors round-the-clock many sorts of seismoacoustic events. Tens of rockets are launched every year from Baikonur spaceport located in Central Kazakhstan. Baikonur rockets fly over several regions of Kazakhstan. Kazakh monitoring stations record launches, rocket stage falls, satellite recovery and sometimes accidents. A catalog of events associated with such activity is built. Some waveform features are collected. The catalog also contains some kinematic and dynamic parameters of the events sources. The signals from accidents of Dnepr rocket of July 26, 2006 and Proton rocket of September 5, 2007 and of July 2, 2013 were studied in details. Discrimination of the events associated with spaceport activity and its exclusion from seismic bulletins allows improving the bulletins quality. And in case of accident this information helps to estimate the event parameters and to start recovery procedures in proper time.

  13. Lessons learned from near-fault recordings of the Emilia, 2012 seismic sequence

    NASA Astrophysics Data System (ADS)

    Masi, Angelo; Mucciarelli, Marco; Chiauzzi, Leonardo; Gallipoli, Maria Rosaria; Stabile, Tony; Lizza, Carmine; Vignola, Luigi

    2013-04-01

    Lessons learned from near-fault recordings of the Emilia, 2012 seismic sequence Marco Mucciarelli (CNR-OGS, Trieste, Italy) Leonardo Chiauzzi, Angelo Masi (Basilicata University, Potenza, Italy) Maria Rosaria Gallipoli, Tony Stabile (IMAA-CNR, Tito Scalo, Italy) Carmine Lizza, Luigi Vignola (Mallet s.r.l., Marsicovetere, Italy) The Emilia 2012 seismic sequence provided a wealth of strong motion data, both from permanent and temporary network. The accelerometric station closest to epicentre is managed by the RAN network and it is located in the town of Mirandola (Code MRN), just close to the faults that generated the two main earthquakes of the sequence that are the M=5.9 and M=5.8, occurred on May 20 and 29 respectively. At same site of the MRN-RAN station, after the event occurred on May, 20 2012, a temporary accelerometric station was installed (code CNR) just 5 meters away. While the MRN-RAN station is inside a small building (electric substation) the CNR station was installed in free-field. After the mainshock, the site was also well characterised from the geophysical and geotechnical stand point with surface and down-hole surveys, and laboratory dynamic test on undisturbed samples. The analysis of the recordings, also compared with code provisions, provided several useful insights: 1) while the geological setting is apparently 1-D, there is a strong difference between horizontal components, not only for the mainshock but also for lesser quakes (magnitude down to below 2) thus ruling out a source effect; 2) the mismatch with the spectra provided by the Italian seismic code is due mainly to a poor performance of Vs30-based classification for deep soil site like the ones in the Po Valley rather than to PSHA estimates of hazard on rock conditions; 3) the influence of the housing of the RAN station is clearly visible at high frequency, the only portion of the spectra where the to station show different spectra ordinates; 4) integral parameters like Housner

  14. Submarine Paleoearthquake Records and Seismic Risk Assessment in the Sea of Marmara, Turkey

    NASA Astrophysics Data System (ADS)

    Cagatay, M. Namik; Biltekin, Demet; Erel, Levent; Henry, Pierre; Gasperini, Luca; McHugh, Cecilia M.; Grall, Celine; Gungor, L. Nurdan; Gungor, Emin; Polonia, Alina; Zabci, Cengiz; Akkok, Remzi

    2014-05-01

    Long-term paleoearthquake history of faults is important for probabilistic earthquake risk assessment. Such records can be obtained from the study of mass-transport units triggered by seismic activity in marine and lake basins. The Sea of Marmara (SoM), located on the North Anatolian Fault (NAF), is an important laboratory for the study of paleoearthquake records, mainly because it has: a) more than 2000 years of historical earthquake records with which radiometrically dated sedimentary earthquake records can be correlated, b) high sedimentation rates (≤3m/kyrs) so that individual events can be distinguished, and c) cold fluid and hydrocarbon seeps along active faults, leaving sedimentary and geochemical signatures of earthquake activity. After the destructive 1912 Mw 7.4 Mürefte and 1999 Mw 7.4 Izmit and Mw 7.2 Duzce earthquakes, the SoM represent a seismic gap. It is therefore crucial to obtain information on the long-term earthquake history of the NAF in the SoM. We have carried out a systematic study of the 24 cores recovered from the various Marmara basins and highs characterizing the different segments of the NAF, using high resolution digital X-Ray Radiography and µ-XRF Core Scanner, MSCL physical properties and grain-size analyses. The chronology was determined using AMS radiocarbon and radionuclide methods. Turbidite-homogenite deposits (TH) triggered by earthquakes are commonly characterized by multiple sand-silt laminae above a sharp and often erosional base and a homogeneous mud at the top. However, in shallow basins (<110 m) such as Gölcük and Gemlik, the TH units consists of red brown coarse to medium silt units having a sharp basal boundary. The basal TH parts have high gamma density and magnetic susceptibility, and are often enriched in one or more of elements, such as Si, Zr, Ca, Ti, K and Fe, indicative of coarse detrital silicate and carbonate shell input. Radionuclide and radiocarbon dated TH units in different basins of the SoM can be

  15. Paleogeodetic records of seismic and aseismic subduction from central Sumatran microatolls, Indonesia

    USGS Publications Warehouse

    Natawidjaja, D.H.; Sieh, K.; Ward, S.N.; Cheng, H.; Edwards, R. Lawrence; Galetzka, J.; Suwargadi, B.W.

    2004-01-01

    We utilize coral microatolls in western Sumatra to document vertical deformation associated with subduction. Microatolls are very sensitive to fluctuations in sea level and thus act as natural tide gauges. They record not only the magnitude of vertical deformation associated with earthquakes (paleoseismic data), but also continuously track the long-term aseismic deformation that occurs during the intervals between earthquakes (paleogeodetic data). This paper focuses on the twentieth century paleogeodetic history of the equatorial region. Our coral paleogeodetic record of the 1935 event reveals a classical example of deformations produced by seismic rupture of a shallow subduction interface. The site closest to the trench rose 90 cm, whereas sites further east sank by as much as 35 cm. Our model reproduces these paleogeodetic data with a 2.3 m slip event on the interface 88 to 125 km from the trench axis. Our coral paleogeodetic data reveal slow submergence during the decades before and after the event in the areas of coseismic emergence. Likewise, interseismic emergence occurred before and after the 1935 event in areas of coseismic submergence. Among the interesting phenomenon we have discovered in the coral record is evidence of a large aseismic slip or "silent even" in 1962, 27 years after the 1935 event. Paleogeodetic deformation rates in the decades before, after, and between the 1935 and 1962 events have varied both temporally and spatially. During the 25 years following the 1935 event, submergence rates were dramatically greater than in prior decades. During the past four decades, however, rates have been lower than in the preceding decades, but are still higher than they were prior to 1935. These paleogeodetic records enable us to model the kinematics of the subduction interface throughout the twentieth century. Copyright 2004 by the American Geophysical Union.

  16. 15/16 ips Operation of the Precision Instrument Company Model P15100 tape recorder to record the standard (30 Hz) NCER seismic data multiplex system

    USGS Publications Warehouse

    Eaton, Jerry P.

    1976-01-01

    In recent months the need has arisen to record special seismic networks consisting of a dozen or more standard NCER seismic systems telemetered to a central collection point on a reliable, portable, low-power tape recorder. Because of its simplicity and the ease with which it can be adapted for the purpose, the PI 5100 field recorder should be considered for such use. In the tests described here, a PI 5100 was speeded up to run at 15/16 inches per second (ips) and signals from the standard multiplex system test modulator bank were recorded on one tape track by means of a simple, improvised AM record amplifier. The results of these tests are extremely encouraging: the dynamic range of the system when played back on the Bell and Howell Model 3700 B reproduce machine, with subtractive compensation, is nearly as high as for the system employing the B&H 3700 B for recording. These notes indicate the principle employed to speed up the recorder, outline the circuit required to drive the tape heads in the AM record mode, and describe the tests carried out to evaluate the system's performance.

  17. Transient Creep and Mechanical Instabilities - Microstructural Records of Aseismic to Seismic Transitions

    NASA Astrophysics Data System (ADS)

    White, J. C.

    2013-12-01

    Within the overall framework of a layered seismic-aseismic crust, mixed-mode brittle-ductile deformation along faults and shear zones occurs at all crustal depths regardless of the ambient pressure and temperature; earthquake rupture occurs in the deepest crust, while upper crustal faults evolve to aseismic shear zones. The mechanics of this transition at a local scale have implications for the evolution of crustal-scale phenomena. These include the periodicity of seismic events, whether ductile shear at depth drives upper crustal earthquakes or vice versa and the rupture history of apparently weak faults. Transitions from ductile flow to brittle rupture at a range of crustal levels exhibit microstructural commonalities e.g. plagioclase and pyroxene in granulites, calcite in sub-greenschist rocks. The primary difficulty in elucidating these microstructural transitions resides in the tendency of ductile and brittle effects to destroy evidence of the other. Given the latter issue, the diversity of deformation histories preserved in the rock record present a fruitful ground for study. Several field examples are described where steady-state dislocation creep (glide + climb) substructures typical of the background deformation are replaced by a predominance of dislocation glide and recrystallization, reflecting the inability of recovery processes to match the strain hardening rate of interacting dislocations. The dominance of dislocation glide (crystal plasticity) in a Peierls or cross-slip deformation regime is particularly significant because of its role in enhancing the thermo-mechanical feedback that favors ductile localization during the lead up to discrete rupture. Localization can in many cases be initiated by material changes in the form of introduction of weaker rocks such as coarse-grained pegmatites and veins.

  18. Seismic slip recorded in tourmaline fault mirrors from Elba Island (Italy)

    NASA Astrophysics Data System (ADS)

    Viti, C.; Brogi, A.; Liotta, D.; Mugnaioli, E.; Spiess, R.; Dini, A.; Zucchi, M.; Vannuccini, G.

    2016-05-01

    This paper reports the first example of fault mirrors developed in an unusual protolith, consisting of tourmaline crystals with interstitial goethite. The deformation mechanisms active in the fault zone have been investigated from the outcrop to the nanoscale, aiming to identify possible traces of frictional heating at seismic slip rate, as observed for other fault mirrors in different protoliths. The investigation revealed the superposition of two main deformational stages. The first was dominated by brittle processes and produced a cataclastic/ultracataclastic principal slip zone, a few mm thick; the second was associated with seismic slip and produced a sharp discontinuity (the principal slip surface) within the cataclastic/ultracataclastic zone. The mirror-like coating, a few microns thick, occurs on the principal slip surface, and is characterized by 1) absence of interstitial goethite; 2) occurrence of truncated tourmaline crystals; 3) highly variable grain size, from 200 μm to 200 nm; 4) tourmaline close packing with interlobate grain boundaries, and 5) tourmaline random crystallographic orientation. Micro and nanostructural investigations indicate the occurrence of thermally-activated processes, involving both interstitial goethite and tourmaline. In particular, close to the principal slip surface, goethite is completely decomposed, and produced an amorphous porous material, with local topotactic recrystallization of hematite. Tourmaline clasts are typically characterized by strongly lobate boundaries, indicative of reaction and partial decomposition at grain boundaries. TEM observations revealed the occurrence of tourmaline nanograins, a few tens of nm in size, characterized by rounded shape and fading amorphous boundaries, that cannot be obtained by brittle processes. Lastly, the peculiar interlobate microstructure of the mirror surface is interpreted as the result of grain boundary recrystallization processes taking place by deformation at high

  19. Recorded earthquake responses from the integrated seismic monitoring network of the Atwood Building, Anchorage, Alaska

    USGS Publications Warehouse

    Celebi, M.

    2006-01-01

    An integrated seismic monitoring system with a total of 53 channels of accelerometers is now operating in and at the nearby free-field site of the 20-story steel-framed Atwood Building in highly seismic Anchorage, Alaska. The building has a single-story basement and a reinforced concrete foundation without piles. The monitoring system comprises a 32-channel structural array and a 21-channel site array. Accelerometers are deployed on 10 levels of the building to assess translational, torsional, and rocking motions, interstory drift (displacement) between selected pairs of adjacent floors, and average drift between floors. The site array, located approximately a city block from the building, comprises seven triaxial accelerometers, one at the surface and six in boreholes ranging in depths from 15 to 200 feet (???5-60 meters). The arrays have already recorded low-amplitude shaking responses of the building and the site caused by numerous earthquakes at distances ranging from tens to a couple of hundred kilometers. Data from an earthquake that occurred 186 km away traces the propagation of waves from the deepest borehole to the roof of the building in approximately 0.5 seconds. Fundamental structural frequencies [0.58 Hz (NS) and 0.47 Hz (EW)], low damping percentages (2-4%), mode coupling, and beating effects are identified. The fundamental site frequency at approximately 1.5 Hz is close to the second modal frequencies (1.83 Hz NS and 1.43 EW) of the building, which may cause resonance of the building. Additional earthquakes prove repeatability of these characteristics; however, stronger shaking may alter these conclusions. ?? 2006, Earthquake Engineering Research Institute.

  20. Analysis of Background Seismic Noise Recorded at the Amundsen-Scott South Pole Station, Antarctica

    NASA Astrophysics Data System (ADS)

    Anderson, K. R.; Aster, R.; Beaudoin, B. C.; Butler, R.

    2006-12-01

    station. Therefore, encroachment of any of these noise sources into the Quiet Sector will adversely affect the signal-to-noise ratio in the frequencies above 1 Hz for seismograms recorded at QSPA. At this point, QSPA is by far the quietest seismic station in the world at these high frequencies. We hope that we can preserve these low background noise levels and keep the QSPA one of the quietest places on Earth.

  1. Seismic Site Effects from the Seafloor Motion Recorded by the Short-period Ocean Bottom Seismometers

    NASA Astrophysics Data System (ADS)

    Lin, J. Y.; Cheng, W. B.; Chin, S. J.; Hsu, S. K.; Dong, J. J.

    2014-12-01

    For decades, it has been mentioned that submarine slope failures are spatially linked to the presence of gas hydrates/gas-charged sediments. When triggered by earthquakes, oversteepen and instable sediments may prompt breakouts of the slopes containing gas hydrates and cause submarine landslides and tsunamis. Widely distributed BSRs have been observed in the area offshore of southwestern Taiwan where the active accretionary complex meets with the passive China continental margin. In the region, large or small scale landslides were also reported based on seismic interpretations. In order to clarify the link between earthquake, landslide and the presence of gas hydrate, we evaluate the response of seafloor sediments in regard to passive dynamic loads. Horizontal-to-vertical (H/V) spectral ratios are used to characterize the local sediment response. Ambient noise as well as distant earthquakes are used as generators of the passive dynamic loads. Based on this study, we aim to characterize the site in terms of its physical properties and the local site effect produced by shallow marine sediments. The results show that the maximum H/V ratios appeared in the range of 5-10 Hz, where the horizontal amplitudes increased by an order of magnitude relative to the vertical amplitude. The stations located in the northwestern part of study area were characterized by another relatively small peak at proximately 2 Hz, which may indicates the presence of a discontinuity of sediments. For most stations, the H/V ratios estimated based on the earthquake (i.e. strong input signal) and noise (background, micro-seismic noise) records were characterized by different pattern. No distinct peak is observed for the H/V pattern calculated during earthquakes. This phenomenon may suggest that no clear sedimentary boundary exist when a stronger motion applies. Estimating H/V spectral ratios of data recorded by the seven short period OBSs (Ocean Bottom Seismometer) deployed in the southwest Taiwan

  2. Local Seismicity Recorded by ChilePEPPER: Implications for Dynamic Accretionary Prism Response and Long-term Prism Evolution

    NASA Astrophysics Data System (ADS)

    de Moor, A.; Trehu, A. M.; Tryon, M. D.

    2015-12-01

    To investigate the dynamic response of the outer accretionary wedge updip from the patch of greatest slip during the Mw8.8 2010 Maule earthquake, 10 Ocean Bottom Seismometers (OBS) were deployed from May 2012 to March 2013 in a small array with an inter-instrument spacing of ~12 km . Nine instruments were recovered, with 4 recording data on 3 intermediate-band 3-component seismometers and a differential pressure gauge and 5 recording data from absolute pressure gauges. [note: All instruments were also equipped with a fluid flow meter sensitive to flow rates as low as 0.0001 cm/yr in or out of the sediments. However, no flow signal was detected.] Here we present hypocenters for 569 local events that have S-P times less than 17 seconds (i.e. within ~125 km of the array) using hand-picked arrival times and a 1D velocity model derived from a 2D seismic refraction profile through the region (Moscoso et al 2011, EPSL). We analyze the distribution of seismicity in the context of published slip models, ChilePEPPER high-resolution seismic reflection data, critical taper analysis done by Cubas et al 2013 (EPSL), and offshore gravity data. The data show distinct segmentation within the outer prism. The northern section of the study area is characterized by a lack of seismicity, accretion of nearly all incoming sediment and a prism at critical taper. In contrast, abundant seismicity, significant sediment underthrusting at the deformation front and a prism below critical taper angle characterize the southern part of the study area. Both coseismic slip and post-rupture local seismicity can be related to density anomalies within the upper plate as revealed by free air gravity data corrected for the effects of bathymetry and the subducting plate. [ChilePEPPER - Project Evaluating Prism Post-Earthquake Response

  3. Cataloguing Seismic Waveform Properties Recorded With a 3D Network in a Gold Mine in South Africa

    NASA Astrophysics Data System (ADS)

    Julia, J.; Nyblade, A. A.; Gok, R.; Walter, W. R.; Linzer, L.; Durrheim, R. J.; Dirks, P.

    2007-12-01

    The SAVUKA gold mine is located in the northwestern edge of the Witwatersrand basin, a Late Archean (3.07- 2.71~Ga) intracratonic basin in South Africa that hosts the largest known gold-uranium-pyrite ore deposits in the world. Seismic events related to the mine activity span several orders of magnitude through a variety of sources that include mine blasts, pillar collapses, and faulting events. These events are systematically recorded and catalogued through an in-mine, 3D seismic network consisting of 20, three-component, short-period stations with natural frequencies ranging between 4.5 and 28.0~Hz and deployed as deep as ~3.5 km. After 5 months of seismic monitoring of the mine, we have been able to assemble a database of over 6000 events spanning magnitudes in the -2.5 < ML < 4.4 range. The potential of this unique data set for characterizing the detailed seismic properties of the basin and studying source properties of non-double couple events is explored through simple, first-pass analysis on the recorded waveforms. Moreover, the in-mine network is complemented by a small array of 4 broadband stations interspaced ~10~km apart on the surface of the mine, and by a number of AfricaArray stations in South Africa and neighboring countries located at regional distances (50- 1000~km) from the mine. The largest mine-induced events are clearly recorded at distances as far away from the mine as 450~km and provide a unique opportunity for studying the regional propagation of seismic phases as well as the structure of the cratonic crust underlying the basin.

  4. Surface seismic measurements of near-surface P-and S-wave seismic velocities at earthquake recording stations, Seattle, Washington

    USGS Publications Warehouse

    Williams, R.A.; Stephenson, W.J.; Frankel, A.D.; Odum, J.K.

    1999-01-01

    We measured P-and S-wave seismic velocities to about 40-m depth using seismic-refraction/reflection data on the ground surface at 13 sites in the Seattle, Washington, urban area, where portable digital seismographs recently recorded earthquakes. Sites with the lowest measured Vs correlate with highest ground motion amplification. These sites, such as at Harbor Island and in the Duwamish River industrial area (DRIA) south of the Kingdome, have an average Vs in the upper 30 m (V??s30) of 150 to 170 m/s. These values of V??s30 place these sites in soil profile type E (V??s30 < 180 m/s). A "rock" site, located at Seward Park on Tertiary sedimentary deposits, has a V??S30 of 433 m/s, which is soil type C (V??s30: 360 to 760 m/s). The Seward Park site V??s30 is about equal to, or up to 200 m/s slower than sites that were located on till or glacial outwash. High-amplitude P-and S-wave seismic reflections at several locations appear to correspond to strong resonances observed in earthquake spectra. An S-wave reflector at the Kingdome at about 17 to 22 m depth probably causes strong 2-Hz resonance that is observed in the earthquake data near the Kingdome.

  5. Incrementally developed slickenfibers — Geological record of repeating low stress-drop seismic events?

    NASA Astrophysics Data System (ADS)

    Fagereng, Åke; Remitti, Francesca; Sibson, Richard H.

    2011-10-01

    An accretionary mélange of Triassic age ocean floor sediments exposed in the Chrystalls Beach Complex, South Island, New Zealand, comprises competent sandstone and chert phacoids set in a cleaved mudstone matrix, deformed in a continuous-discontinuous style at subgreenschist conditions. Deformation structures include a pervasive anastomosing fault-fracture mesh of multiple shearing surfaces, subparallel to cleavage, coated with incrementally developed quartz-calcite slickenfibers. Microstructural observations reveal slickenfiber growth by 'crack-seal' shear slip increments of 10-100 μm, with incremental slip transfer of the same order accommodated by opening of extension fractures that link en echelon slip surfaces. Individual slip surfaces can be traced for meters to tens of meters so that the ratio of average slip, u, to potential rupture length, L, predominantly lies within the range, 10 - 6 < u/ L < 10 - 5 , characteristic of microearthquakes obeying 'constant stress-drop' scaling with a low stress-drop Δτ ~ 30 kPa, typical of low frequency earthquakes. The host-rock assemblage, metamorphic environment, inference of near-lithostatic fluid overpressures, low stress-drop and mixed continuous-discontinuous shearing, resemble conditions and characteristics of low frequency earthquakes as identified within the seismic signals recorded during episodic tremor and slow slip events, at the downdip end of the seismogenic subduction thrust interface and within accretionary prisms.

  6. A brittle failure model for long-period seismic events recorded at Turrialba Volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Eyre, Thomas S.; Bean, Christopher J.; De Barros, Louis; Martini, Francesca; Lokmer, Ivan; Mora, Mauricio M.; Pacheco, Javier F.; Soto, Gerardo J.

    2015-03-01

    A temporary seismic network, consisting of 23 broadband and six short-period stations, was installed in a dense network at Turrialba Volcano, Costa Rica, between 8 March and 4 May 2011. During this time 513 long-period (LP) events were observed. Due to their pulse-like waveforms, the hypothesis that the events are generated by a slow-failure mechanism, based on a recent new model by Bean et al. (2014), is tested. A significant number (107) of the LPs are jointly inverted for their source locations and mechanisms, using full-waveform moment tensor inversion. The locations are mostly shallow, with depths < 800 m below the active Southwest Crater. The results of the decompositions of the obtained moment tensor solutions show complex source mechanisms, composed of high proportions of isotropic and low, but seemingly significant, proportions of compensated linear vector dipole and double-couple components. It is demonstrated that this can be explained as mode I tensile fracturing with a strong shear component. The source mechanism is further investigated by exploring scaling laws within the data. The LPs recorded follow relationships very similar to those of conventional earthquakes, exhibiting frequency-magnitude and corner frequency versus magnitude relationships that can be explained by brittle failure. All of these observations indicate that a slow-failure source model can successfully describe the generation of short-duration LP events at Turrialba Volcano.

  7. Low-frequency whale and seismic airgun sounds recorded in the mid-Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Nieukirk, Sharon L.; Stafford, Kathleen M.; Mellinger, David K.; Dziak, Robert P.; Fox, Christopher G.

    2004-04-01

    Beginning in February 1999, an array of six autonomous hydrophones was moored near the Mid-Atlantic Ridge (35 °N-15 °N, 50 °W-33 °W). Two years of data were reviewed for whale vocalizations by visually examining spectrograms. Four distinct sounds were detected that are believed to be of biological origin: (1) a two-part low-frequency moan at roughly 18 Hz lasting 25 s which has previously been attributed to blue whales (Balaenoptera musculus); (2) series of short pulses approximately 18 s apart centered at 22 Hz, which are likely produced by fin whales (B. physalus); (3) series of short, pulsive sounds at 30 Hz and above and approximately 1 s apart that resemble sounds attributed to minke whales (B. acutorostrata); and (4) downswept, pulsive sounds above 30 Hz that are likely from baleen whales. Vocalizations were detected most often in the winter, and blue- and fin whale sounds were detected most often on the northern hydrophones. Sounds from seismic airguns were recorded frequently, particularly during summer, from locations over 3000 km from this array. Whales were detected by these hydrophones despite its location in a very remote part of the Atlantic Ocean that has traditionally been difficult to survey.

  8. Automatic Detection and Identification of Seismic Signals Recorded at Krakatau Volcano (Indonesia) Using Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Ibs-von Seht, M.; Kniess, R.

    2006-12-01

    A number of different event types can be observed in the records of seismic stations operated on Krakatau volcano (Indonesia). These include volcano-induced signals such as LP, VT, and hybrid-type events as well as signals not originating from the volcano such as local and regional tectonic earthquakes and transient noise signals. The work presented here aims at the realization of a system that automatically detects and identifies the signals in order to estimate and monitor current activity states of the volcano. An artificial neural network (ANN) approach was chosen for the identification task. A set of parameters were defined, describing waveform and spectrogram properties of events detected by an STA/LTA algorithm. The parameters are fed into an ANN which is, after a training phase, able to generalize input data and identify corresponding event types. The success of the identification depends on the network architecture and training strategy. Several tests have been performed in order to determine an appropriate network layout and training intensity for the given problem. The resulting network shows a good performance. A practical implementation of the system for the volcano observatory routine is sketched.

  9. Snap, Crackle, Pop: Dilational fault breccias record seismic slip below the brittle-plastic transition

    NASA Astrophysics Data System (ADS)

    Melosh, Ben L.; Rowe, Christie D.; Smit, Louis; Groenewald, Conrad; Lambert, Christopher W.; Macey, Paul

    2014-10-01

    Off-fault dynamic tensile cracks form behind an earthquake rupture front with distinct orientation and spacing. These cracks explode the wall rock and create breccias, which we hypothesize will preserve a unique fingerprint of dynamic rupture. Identification of these characteristic breccias may enable a new tool for identifying paleoseismic slip surfaces in the rock record. Using previous experimental and theoretical predictions, we develop a field-based model of dynamic dilational breccia formation. Experimental studies find that secondary tensile fracture networks comprise closely spaced fractures at angles of 70-90° from a slip surface, as well as fractures that branch at angles of ∼30° from a primary mode I fracture. The Pofadder Shear Zone, in Namibia and South Africa, preserves breccias formed in the brittle-ductile transition zone displaying fracture patterns consistent with those described above. Fracture spacing is approximately two orders of magnitude less than predicted by quasi-static models. Breccias are clast-supported, monomict and can display an abrupt transition from fracture network crackle breccia to mosaic breccia textures. Brecciation occurs by the intersection of off-fault dynamic fractures and wall rock fabric; this is in contrast to previous models of fluid pressure gradient-driven failure “implosion breccias”. This mechanism tends to form many similar sized clasts with particle size distributions that may not display self-similarity; where self-similarity is observed the distributions have relatively low D-values of 1.47±0.37, similar to other studies of dynamic processes. We measure slip distances at dilational breccia stepovers, estimating earthquake magnitudes between Mw 2.8-5.8 and associated rupture lengths of 0.023-3.3 km. The small calculated rupture dimensions, in combination with our geologic observations, suggest that some earthquakes nucleated within the quartz-plastic transitional zone and potentially record deep

  10. Evaluation of the southern California seismic velocity models through simulation of recorded events

    NASA Astrophysics Data System (ADS)

    Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Khoshnevis, Naeem; Cheng, Keli

    2016-06-01

    Significant effort has been devoted over the last two decades to the development of various seismic velocity models for the region of southern California, United States. These models are mostly used in forward wave propagation simulation studies, but also as base models for tomographic and source inversions. Two of these models, the community velocity models CVM-S and CVM-H, are among the most commonly used for this region. This includes two alternative variations to the original models, the recently released CVM-S4.26 which incorporates results from a sequence of tomographic inversions into CVM-S, and the user-controlled option of CVM-H to replace the near-surface profiles with a VS30-based geotechnical model. Although either one of these models is regarded as acceptable by the modeling community, it is known that they have differences in their representation of the crustal structure and sedimentary deposits in the region, and thus can lead to different results in forward and inverse problems. In this paper, we evaluate the accuracy of these models when used to predict the ground motion in the greater Los Angeles region by means of an assessment of a collection of simulations of recent events. In total, we consider 30 moderate-magnitude earthquakes (3.5 < Mw < 5.5) between 1998 and 2014, and compare synthetics with data recorded by seismic networks during these events. The simulations are done using a finite-element parallel code, with numerical models that satisfy a maximum frequency of 1 Hz and a minimum shear wave velocity of 200 m s-1. The comparisons between data and synthetics are ranked quantitatively by means of a goodness-of-fit (GOF) criteria. We analyse the regional distribution of the GOF results for all events and all models, and draw conclusions from the results and how these correlate to the models. We find that, in light of our comparisons, the model CVM-S4.26 consistently yields better results.

  11. Evaluation of the Southern California Seismic Velocity Models through Simulation of Recorded Events

    NASA Astrophysics Data System (ADS)

    Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Khoshnevis, Naeem; Cheng, Keli

    2016-03-01

    Significant effort has been devoted over the last two decades to the development of various seismic velocity models for the region of southern California, United States. These models are mostly used in forward wave propagation simulation studies, but also as base models for tomographic and source inversions. Two of these models, the community velocity models CVM-S and CVM-H, are among the most commonly used for this region. This includes two alternative variations to the original models, the recently released CVM-S4.26 which incorporates results from a sequence of tomographic inversions into CVM-S, and the user-controlled option of CVM-H to replace the near-surface profiles with a VS30-based geotechnical (GTL) model. Although either one of these models is regarded as acceptable by the modeling community, it is known that they have differences in their representation of the crustal structure and sedimentary deposits in the region, and thus can lead to different results in forward and inverse problems. In this article we evaluate the accuracy of these models when used to predict the ground motion in the greater Los Angeles region by means of an assessment of a collection of simulations of recent events. In total, we consider 30 moderate-magnitude earthquakes (3.5 < Mw < 5.5) between 1998 and 2014, and compare synthetics with data recorded by seismic networks during these events. The simulations are done using a finite element parallel code, with numerical models that satisfy a maximum frequency of 1 Hz and a minimum shear wave velocity of 200 m/s. The comparisons between data and synthetics are ranked quantitatively by means of a goodness-of-fit (GOF) criteria. We analyze the regional distribution of the GOF results for all events and all models, and draw conclusions from the results and how these correlate to the models. We find that, in light of our comparisons, the model CVM-S4.26 consistently yields better results.

  12. Historical Earthquake Records and their Application for Seismic Hazard and Risk Assessment in Tianshui, Gansu Province, Northwestern China

    NASA Astrophysics Data System (ADS)

    Wang, L.; Wang, Z.

    2009-12-01

    Tianshui, located in southeastern Gansu Province of northwestern China, was a center of early Chinese civilization and the birthplace of “Ba Gua” or “eight symbols.” It has a long history of earthquakes and many strong and large earthquakes have occurred there. Earthquakes, ancient or modern ones, have not only been well recorded, but also left marks on many historical landmarks and buildings that can still be seen today. For example, major damage by the 1654 Tianshui earthquake (M8.0) and some minor damage by the 2008 Wenchuan earthquake can be seen in the Maiji Grotto. A new effort to investigate and reexamine the historical macroseismic records is under way, with the aim of better seismic hazard and risk assessment for the Tianshui area. Seismic hazard and risk will be assessed for the Tianshui area using the 2,500 years of intensity observations (records). The results will be used by local governments and communities for developing more effective mitigation policies in the aftermath of the 2008 Wenchuan earthquake. The results will also be compared to hazard and risk assessments derived from other approaches, such as probabilistic and deterministic seismic hazard analyses.

  13. The application of back-propagation neural network to automatic picking seismic arrivals from single-component recordings

    NASA Astrophysics Data System (ADS)

    Dai, Hengchang; MacBeth, Colin

    1997-07-01

    An automatic approach is developed to pick P and S arrivals from single component (1-C) recordings of local earthquake data. In this approach a back propagation neural network (BPNN) accepts a normalized segment (window of 40 samples) of absolute amplitudes from the 1-C recordings as its input pattern, calculating two output values between 0 and 1. The outputs (0,1) or (1,0) correspond to the presence of an arrival or background noise within a moving window. The two outputs form a time series. The P and S arrivals are then retrieved from this series by using a threshold and a local maximum rule. The BPNN is trained by only 10 pairs of P arrivals and background noise segments from the vertical component (V-C) recordings. It can also successfully pick seismic arrivals from the horizontal components (E-W and N-S). Its performance is different for each of the three components due to strong effects of ray path and source position on the seismic waveforms. For the data from two stations of TDP3 seismic network, the success rates are 93%, 89%, and 83% for P arrivals and 75%, 91%, and 87% for S arrivals from the V-C, E-W, and N-S recordings, respectively. The accuracy of the onset times picked from each individual 1-C recording is similar. Adding a constraint on the error to be 10 ms (one sample increment), 66%, 59% and 63% of the P arrivals and 53%, 61%, and 58% of the S arrivals are picked from the V-C, E-W and N-S recordings respectively. Its performance is lower than a similar three-component picking approach but higher than other 1-C picking methods.

  14. Establishment of data base of regional seismic recordings from earthquakes, chemical explosions and nuclear explosions in the Former Soviet Union

    SciTech Connect

    Ermolenko, N.A.; Kopnichev, Yu.F.; Kunakov, V.G.; Kunakova, O.K.; Rakhmatullin, M.Kh.; Sokolova, I.N.; Vybornyy, Zh.I.

    1995-06-01

    In this report results of work on establishment of a data base of regional seismic recordings from earthquakes, chemical explosions and nuclear explosions in the former Soviet Union are described. This work was carried out in the Complex Seismological Expedition (CSE) of the Joint Institute of Physics of the Earth of the Russian Academy of Sciences and Lawrence Livermore National Laboratory. The recording system, methods of investigations and primary data processing are described in detail. The largest number of digital records was received by the permanent seismic station Talgar, situated in the northern Tien Shan, 20 km to the east of Almaty city. More than half of the records are seismograms of underground nuclear explosions and chemical explosions. The nuclear explosions were recorded mainly from the Semipalatinsk test site. In addition, records of the explosions from the Chinese test site Lop Nor and industrial nuclear explosions from the West Siberia region were obtained. Four records of strong chemical explosions were picked out (two of them have been produced at the Semipalatinsk test site and two -- in Uzbekistan). We also obtained 16 records of crustal earthquakes, mainly from the Altai region, close to the Semipalatinsk test site, and also from the West China region, close to the Lop Nor test site. In addition, a small number of records of earthquakes and underground nuclear explosions, received by arrays of temporary stations, that have been working in the southern Kazakhstan region are included in this report. Parameters of the digital seismograms and file structure are described. Possible directions of future work on the digitizing of unique data archive are discussed.

  15. An Open Hardware seismic data recorder - a solid basis for citizen science

    NASA Astrophysics Data System (ADS)

    Mertl, Stefan

    2015-04-01

    "Ruwai" is a 24-Bit Open Hardware seismic data recorder. It is built up of four stackable printed circuit boards fitting the Arduino Mega 2560 microcontroller prototyping platform. An interface to the BeagleBone Black single-board computer enables extensive data storage, -processing and networking capabilities. The four printed circuit boards provide a uBlox Lea-6T GPS module and real-time clock (GPS Timing shield), an Texas Instruments ADS1274 24-Bit analog to digital converter (ADC main shield), an analog input section with a Texas Instruments PGA281 programmable gain amplifier and an analog anti-aliasing filter (ADC analog interface pga) and the power conditioning based on 9-36V DC input (power supply shield). The Arduino Mega 2560 is used for controlling the hardware components, timestamping sampled data using the GPS timing information and transmitting the data to the BeagleBone Black single-board computer. The BeagleBone Black provides local data storage, wireless mesh networking using the optimized link state routing daemon and differential GNSS positioning using the RTKLIB software. The complete hardware and software is published under free software - or open hardware licenses and only free software (e.g. KiCad) was used for the development to facilitate the reusability of the design and increases the sustainability of the project. "Ruwai" was developed within the framework of the "Community Environmental Observation Network (CEON)" (http://www.mertl-research.at/ceon/) which was supported by the Internet Foundation Austria (IPA) within the NetIdee 2013 call.

  16. Implosion, earthquake, and explosion recordings from the 2000 Seattle Kingdome Seismic Hazards Investigation of Puget Sound (SHIPS), Washington

    USGS Publications Warehouse

    Brocher, Thomas M.; Pratt, Thomas L.; Weaver, Craig S.; Snelson, Catherine M.; Frankel, Arthur D.

    2002-01-01

    This report describes seismic data obtained in Seattle, Washington, March 24-28, 2000, during a Seismic Hazards Investigation of Puget Sound (SHIPS). The seismic recordings obtained by this SHIPS experiment, nicknamed Kingdome SHIPS, were designed to (1) measure site responses throughout Seattle and to (2) help define the location of the Seattle fault. During Kingdome SHIPS, we recorded the Kingdome implosion, four 150-lb (68-kg) shots, and a Mw = 7.6 teleseism using a dense network of seismographs deployed throughout Seattle. The seismographs were deployed at a nominal spacing of 1 km in a hexagonal grid extending from Green Lake in the north to Boeing Field in the south. The Seattle Kingdome was a domed sports stadium located in downtown Seattle near the Seattle fault. The Seattle Kingdome was imploded (demolished) at 8:32 AM local time (16:32 UTC) on March 26 (JD 086), 2000. The seismic energy produced by implosion of the Kingdome was equivalent to a local earthquake magnitude of 2.3. Strong impacts produced by the implosion of the Kingdome generated seismic arrivals to frequencies as low as 0.1 Hz. Two shots located north of the Seattle fault, where the charges were detonated within the ground water column (Discovery and Magnuson Parks), were much more strongly coupled than were the two shots to the south of the Seattle fault, where the shots were detonated above the water table (Lincoln and Seward Parks). Thirty-eight RefTek stations, scattered throughout Seattle, recorded the Mw = 7.6 Japan Volcano Islands earthquake (22.4°N, 143.6°E, 104 km depth) of 28 March 2000 (JD 088). This teleseism produced useful signals for periods between 4 and 7 seconds. Only a few recordings of small magnitude local earthquakes were made, and these recordings are not presented. In this report, we describe the acquisition of these data, discuss the processing and merging of the data into common shot gathers, and illustrate the acquired data. We also describe the format and

  17. Analysis of recently digitized continuous seismic data recorded during the March-May, 1980, eruption sequence at Mount St. Helens

    NASA Astrophysics Data System (ADS)

    Moran, S. C.; Malone, S. D.

    2013-12-01

    The May 18, 1980, eruption of Mount St. Helens (MSH) was an historic event, both for society and for the field of volcanology. However, our knowledge of the eruption and the precursory period leading up it is limited by the fact that most of the data, particularly seismic recordings, were not kept due to severe limitations in the amount of digital data that could be handled and stored using 1980 computer technology. Because of these limitations, only about 900 digital event files have been available for seismic studies of the March-May seismic sequence out of a total of more than 4,000 events that were counted using paper records. Fortunately, data from a subset of stations were also recorded continuously on a series of 24 analog 14-track IRIG magnetic tapes. We have recently digitized these tapes and time-corrected and cataloged the resultant digital data streams, enabling more in-depth studies of the (almost) complete pre-eruption seismic sequence using modern digital processing techniques. Of the fifteen seismic stations operating near MSH for at least a part of the two months between March 20 and May 18, six stations have relatively complete analog recordings. These recordings have gaps of minutes to days because of radio noise, poor tape quality, or missing tapes. In addition, several other stations have partial records. All stations had short-period vertical-component sensors with very limited dynamic range and unknown response details. Nevertheless, because the stations were at a range of distances and were operated at a range of gains, a variety of earthquake sizes were recorded on scale by at least one station, and therefore a much more complete understanding of the evolution of event types, sizes and character should be achievable. In our preliminary analysis of this dataset we have found over 10,000 individual events as recorded on stations 35-40 km from MSH, spanning a recalculated coda-duration magnitude range of ~1.5 to 4.1, including many M < 3

  18. On the potential of recording earthquakes for global seismic tomography by low-cost autonomous instruments in the oceans

    NASA Astrophysics Data System (ADS)

    Simons, Frederik J.; Nolet, Guust; Georgief, Paul; Babcock, Jeff M.; Regier, Lloyd A.; Davis, Russ E.

    2009-05-01

    We describe the development and testing of an autonomous device designed to revolutionize Earth structure determination via global seismic tomography by detecting earthquakes at teleseismic distances in the oceans. One prototype MERMAID, short for Mobile Earthquake Recording in Marine Areas by Independent Divers, was constructed and tested at sea. The instrument combines two readily available, relatively low-cost but state-of-the-art components: a Sounding Oceanographic Lagrangian Observer, or SOLO float, and an off-the-shelf hydrophone, with custom-built data logging hardware. We report on the development of efficient wavelet-based algorithms for the detection and discrimination of seismic events and analyze three time series of acoustic pressure collected at a depth of 700 m in pilot experiments conducted offshore San Diego, CA. In these tests, over 120 hours of data were gathered, and five earthquakes, of which one was teleseismic, were recorded and identified. Quantitative estimates based on these results suggest that instruments of the MERMAID type may collect up to a hundred tomographically useful teleseismic events per year. The final design will also incorporate a Global Positioning System receiver, onboard signal processing software optimized for low-power chips, and high-throughput satellite communication equipment for telemetered data transfer. With these improvements, we hope to realize our vision of a global array of autonomous floating sensors for whole-earth seismic tomography.

  19. Infrasound and Seismic Recordings of a US Airstrike on an ISIS Car Bomb Factory on June 3, 2015

    NASA Astrophysics Data System (ADS)

    Aleqabi, G. I.; Ghalib, H. A. A.; Wysession, M. E.

    2015-12-01

    Concurrent infrasound and seismic records of a jet airstrike in Iraq are presented. Media reports stated that US jets carried out a large airstrike on June 3, 2015, just after midnight local time, that targeted and destroyed an ISIS car bomb factory in Hawija, Iraq, just south of the city of Kirkuk, Iraq. The resulting explosion was felt within Kirkuk and at other locations as far as 34 km away from the Hawija factory. Seismic broadband stations located in northern Iraq, at a distance of about 160 km, show clear simultaneous signals of infrasound waves on the seismometers as well as on collocated infrasound equipment. From an analysis of the body waves, the Pg to Lg time difference is nearly ~20 sec, with a back azimuth of 250o to 260o, which is consistent with explosion location. The time difference between the Pg and infrasound signals is just over 7 minutes, consistent with sound speed in the atmosphere. No clear Rg wave was observed. As was demonstrated by Aleqabi, Wysession, and Ghalib [2015, BSSA, in press], broadband seismic recordings are able to identify and distinguish between several different kinds of MOUT (military operations in urban terrain) and even determine the magnitudes of ordinance used in certain blasts. The addition of collocated infrasound equipment provides additional constraints that can be used in the analysis of the size and form of the MOUT.

  20. MASW on the standard seismic prospective scale using full spread recording

    NASA Astrophysics Data System (ADS)

    Białas, Sebastian; Majdański, Mariusz; Trzeciak, Maciej; Gałczyński, Edward; Maksym, Andrzej

    2015-04-01

    The Multichannel Analysis of Surface Waves (MASW) is one of seismic survey methods that use the dispersion curve of surface waves in order to describe the stiffness of the surface. Is is used mainly for geotechnical engineering scale with total length of spread between 5 - 450 m and spread offset between 1 - 100 m, the hummer is the seismic source on this surveys. The standard procedure of MASW survey is: data acquisition, dispersion analysis and inversion of extracting dispersion curve to obtain the closest theoretical curve. The final result includes share-wave velocity (Vs) values at different depth along the surveyed lines. The main goal of this work is to expand this engineering method to the bigger scale with the length of standard prospecting spread of 20 km using 4.5 Hz version of vertical component geophones. The standard vibroseis and explosive method are used as the seismic source. The acquisition were conducted on the full spread all the time during each single shoot. The seismic data acquisition used for this analysis were carried out on the Braniewo 2014 project in north of Poland. The results achieved during standard MASW procedure says that this method can be used on much bigger scale as well. The different methodology of this analysis requires only much stronger seismic source.

  1. Seismic stratigraphy of the East Antarctic margin: a record of Cenozoic environmental changes

    NASA Astrophysics Data System (ADS)

    Leychenkov, German; Guseva, Julia

    2010-05-01

    We have analyzed more than 120000 km of MCS sections collected on the East Antarctic margin (EAM) from 7E to 142E to correlate seismic stratigraphy with Antarctic glacial history predicted from drilling data and deep-sea proxy records, and to estimate what sort of information about ice sheet behavior and paleoceanographic conditions is contained in seismic records. Most of analyzed MCS lines are located on the continental rise and only the Prydz Bay (PB) shelf was studied in details. Five mayor horizons numbered up-section from "1" to "5" are identified in sedimentary cover of deep water EAM (continental rise). Horizon "1" and "2" are correlated with asynchronous Gondwana breakup and early post-breakup events, respectively; horizons "3", "4" and "5" are proposed to be isochronous surfaces related to Late Cenozoic paleoenvironmental transitions. The distinguishing feature of EAM sedimentary cover is the clear upward change in reflection pattern across horizons "3" and "4" that separates a lower sedimentary unit with mostly parallel reflectors from an upper one consisting of variety of acoustic facies typical of active down-slope and along slope processes. This change is associated with the arrival of the ice sheet to the Antarctic margin and significant increase in sedimentary input to deep water regions. Major results of our study are following: 1) Widespread development of channel-levee systems and other facies related to mass-wasting on the EAM is observed above horizon "4" and this interface is proposed to mark continental-scale Antarctic glaciation in the Early Oligocene. However, earliest signs of active down-slope processes are revealed on the Wilkes Land margin (WLM) above horizon "3" and we infer that this margin was glaciated first, probably in the Late Eocene. Under the temperate climate condition debris was delivered to the slope and rise by glaciers (which flowed from central Antarctica via Aurora Subglacial Basin) and abundant melt-water. The rate of

  2. Seismicity in the Raton Basin of Southern Colorado and Northern New Mexico, USA, as Recorded by a Local Array

    NASA Astrophysics Data System (ADS)

    Macartney, H.

    2013-12-01

    Microseismic events (recorded by a dense network of seismometers deployed in the Raton Basin of southern Colorado and northern New Mexico, USA, over a period of 18 months following the occurrence of a 5.3 magnitude event near Trinidad CO in August, 2011. Micro-seismicity was observed in the region, concentrated in six clusters at depths of 6-12 km below the surface, deep in the basement, and 4-10 km below zones used for fluid disposal from an overlying coalbed methane natural gas field. Clusters are separated from disposal zones by large aseismic intervals. The clusters are mixed in character; both planar and elongate amorphous swarms, some continually active and some as short-lived bursts, with larger initial events tending to occur deeper and smaller after-shocks propagating upward and away from the nucleating events. Magnitudes range between 0 and 3, with the vast majority being less than 1.5M. Most of the clusters have no disposal wells above and no seismic activity was correlated with changes in fluid disposal. No seismicity was detected from hydraulic fracturing operations.

  3. The footprints of typhoons on seismic records and their implications on small-scale coupling mechanisms in South China Sea

    NASA Astrophysics Data System (ADS)

    Xiao, H.; Xue, M.; Yang, T.; Liu, C.; Hua, Q.; Xia, S.; Huang, H.; Le, B. M.; Huo, D.; Pan, M.; Li, L.

    2015-12-01

    By investigating the footprints of typhoons on seismic records, we can understand their contributions to seismic noises as well as to small-scale coupling mechanisms of typhoon-land and typhoon-ocean-land. We analyze the signatures of typhoon KAI-TAK and BOPHA using seismic data from the ocean-bottom seismometers (OBSs) deployed in the central basin of South China Sea by Tongji University in 2012 as well as seismic stations (IC.QIZ,HK.HKPS and RM.SZP) on lands.Our preliminary results show that typhoons mainly enhance microseisms at the frequency band of ~0.1-0.5 Hz, including both long period double frequency (LPDF) and short period double frequency (SPDF) microseisms. A positive correlation observed between the amplitude of microseisms and the height of local ocean waves. Because OBSs are deployed at the bottom of ocean, single frequency (SF) microseisms are not prominent on them due to their fast attenuation with depth. During the typhoon KAI-TAK, the increase of LPDF energy is very small in OBSs while that is very high on land stations, indicating that LPDF microseisms are generated at nearby shorelines and can propagate towards the sea through the solid earth. However, the increase of SPDF energy is almost the same level for both OBSs and land stations indicating that the generation of SPDF is probably local.However, we also observe a small amount of energy arrives before the increases of the wave heights at the land station HK.HKPS. We derive that this energy may from a source that is not local: while LPDF can be generated at nearby shorelines and SPDF can be generated everywhere locally, they can both transmit through the solid part of the Earth to a station some distance away, i.e. HK.HKPS. In addition, we find that typhoons enhance not only the microseisms as expected but also the seismic energy from higher frequency bands. The spectrum amplitude during Typhoon periods, normalized by that of no-storm periods, shows that land stations produce stronger higher

  4. Seismic airgun sounds recorded on moored hydrophones near the Mid-Atlantic Ridge and East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Mellinger, D. K.; Nieukirk, S. L.; Dziak, R. P.; Haxel, J. H.; Fox, C. G.

    2003-12-01

    Sounds of seismic airguns were detected in two years of data collected from large, remote areas near the Mid-Atlantic Ridge (MAR) and the East Pacific Rise (EPR). From February 1999-February 2001, six autonomous hydrophones were moored near the MAR between 15-35 N and 33-50 W, and six more were moored in the EPR between 8 N - 8 S and 95-110 W. Continuous acoustic data recovered from both arrays were examined for sounds associated with seismic airgun activity. This was done using an automatic detection algorithm designed to identify repetitive sounds in the 20-60 Hz band. Airgun impulses occurred every 10-20 s and were recorded frequently on all hydrophones. In the Atlantic, airgun activity peaked in the summer months, and airgun impulses were detected in nearly 100% of the hours examined; Pacific seasonal trends were less obvious. Because of the high source level of the airgun signals, it was possible to estimate the locations of ships conducting seismic surveys despite their great distance, often over 3,000 km from our array. In the Atlantic, we located seismic vessels, presumably commercial, working off the coast of Nova Scotia during summer, and off western Africa and northeast Brazil in spring, summer,and fall. During summer 1999, research airguns were recorded on the MAR near 26 N 50 W. In the eastern tropical Pacific, the predominant source of airgun sounds was seismic vessels in the nearshore waters of southern Ecuador and northern Peru. All of the areas in which intense airgun activity was detected include important habitat for marine mammals; one area included habitat of the critically endangered northern right whale. Sounds from airguns appear to be a major contributor to the sound field in the Atlantic and parts of the Pacific Ocean, and may be of concern given the recent interest in ocean noise and its effects on marine mammals. Acoustic pressure levels of earthquakes are also investigated, and received levels in some common marine mammal habitats are

  5. Wide-angle seismic recording from the 2002 Georgia Basin Geohazards Initiative, northwestern Washington and British Columbia

    USGS Publications Warehouse

    Brocher, Thomas M.; Pratt, Thomas L.; Spence, George D.; Riedel, Michael; Hyndman, Roy D.

    2003-01-01

    This report describes the acquisition and processing of shallow-crustal wide-angle seismicreflection and refraction data obtained during a collaborative study in the Georgia Strait, western Washington and southwestern British Columbia. The study, the 2002 Georgia Strait Geohazards Initiative, was conducted in May 2002 by the Pacific Geoscience Centre, the U.S. Geological Survey, and the University of Victoria. The wide-angle recordings were designed to image shallow crustal faults and Cenozoic sedimentary basins crossing the International Border in southern Georgia basin and to add to existing wide-angle recordings there made during the 1998 SHIPS experiment. We recorded, at wide-angle, 800 km of shallow penetration multichannel seismic-reflection profiles acquired by the Canadian Coast Guard Ship (CCGS) Tully using an air gun with a volume of 1.967 liters (120 cu. in.). Prior to this reflection survey, we deployed 48 Refteks onshore to record the airgun signals at wide offsets. Three components of an oriented, 4.5 Hz seismometer were digitally recorded at all stations. Nearly 160,300 individual air gun shots were recorded along 180 short seismic reflection lines. In this report, we illustrate the wide-angle profiles acquired using the CCGS Tully, describe the land recording of the air gun signals, and summarize the processing of the land recorder data into common-receiver gathers. We also describe the format and content of the archival tapes containing the SEGY-formated, common-receiver gathers for the Reftek data. Data quality is variable but the experiment provided useful data from 42 of the 48 stations deployed. Three-fourths of all stations yielded useful first-arrivals to source-receiver offsets beyond 10 km: the average maximum source-receiver offset for first arrivals was 17 km. Six stations yielded no useful data and useful firstarrivals were limited to offsets less than 10 km at five stations. We separately archived our recordings of 86 local and regional

  6. Comparison of seismic and SO2 time series recorded during eruptive phases of Tungurahua volcano (Ecuador) between 2010 and 2013

    NASA Astrophysics Data System (ADS)

    Battaglia, J.; Hidalgo, S.; Steele, A.; Arellano, S. R.; Ruiz, M. C.; Galle, B.

    2013-12-01

    Tungurahua is one of the most active volcanoes in Ecuador. It is a large andesitic stratovolcano which has been continuously erupting since 1999. Its activity has slightly changed since late 2009 and is now characterized by the occurrence of well-defined eruptive phases lasting from few weeks to months, separated by quiescence periods with a comparable duration range. Eruptive phases include the emission of ash and gases with the occurrence of Strombolian to Vulcanian explosions that can produce short runout pyroclastic flows. The monitoring networks operating on the volcano include 4 permanent DOAS instruments, 5 broadband seismic stations coupled with infrasound sensors and 5 short period seismometers. We examined the data from these instruments for the period 2010-2013 with the aim of looking for possible correlations between seismic and acoustic recordings and the amounts of SO2 emitted by the volcano. The seismicity related to eruptive/degassing processes is dominated by explosion quakes and longer duration tremors. To quantify both phenomena, we proceeded in two ways. First, we established the acoustic and seismic energies of individual explosions and calculated cumulative daily values. Secondly, to quantify the intensity of background tremor we calculated sliding median amplitudes in different frequency bands. On the other hand, NOVAC-1 type DOAS spectrometers operate during daylight only providing up to 140 daily measurements. Valid measurements are only obtained under good weather conditions, leading to irregular and sometimes sparse time series. Usually, daily average fluxes of SO2 are extrapolated from the available measurements. Alternately, we determined the daily observed SO2 masses by integrating all valid recordings during the 11 hours of daily measurement. This approach strongly reduces SO2 measured emissions during quiescence periods and provides time series having an improved correlation on a long time scale (years) with the eruptive phases of

  7. Data quality of seismic records from the Tohoku, Japan earthquake as recorded across the Albuquerque Seismological Laboratory networks

    USGS Publications Warehouse

    Ringler, A.T.; Gee, L.S.; Marshall, B.; Hutt, C.R.; Storm, T.

    2012-01-01

    Great earthquakes recorded across modern digital seismographic networks, such as the recent Tohoku, Japan, earthquake on 11 March 2011 (Mw = 9.0), provide unique datasets that ultimately lead to a better understanding of the Earth's structure (e.g., Pesicek et al. 2008) and earthquake sources (e.g., Ammon et al. 2011). For network operators, such events provide the opportunity to look at the performance across their entire network using a single event, as the ground motion records from the event will be well above every station's noise floor.

  8. Large Earthquake Hazard of the San Jacinto Fault Zone, CA, from Long Record of Simulated Seismicity Assimilating the Available Instrumental and Paleoseismic Data

    NASA Astrophysics Data System (ADS)

    Zöller, G.; Ben-Zion, Y.

    2014-11-01

    We investigate spatio-temporal properties of earthquake patterns in the San Jacinto fault zone (SJFZ), California, between Cajon Pass and the Superstition Hill Fault, using a long record of simulated seismicity constrained by available seismological and geological data. The model provides an effective realization of a large segmented strike-slip fault zone in a 3D elastic half-space, with heterogeneous distribution of static friction chosen to represent several clear step-overs at the surface. The simulated synthetic catalog reproduces well the basic statistical features of the instrumental seismicity recorded at the SJFZ area since 1981. The model also produces events larger than those included in the short instrumental record, consistent with paleo-earthquakes documented at sites along the SJFZ for the last 1,400 years. The general agreement between the synthetic and observed data allows us to address with the long-simulated seismicity questions related to large earthquakes and expected seismic hazard. The interaction between m ≥ 7 events on different sections of the SJFZ is found to be close to random. The hazard associated with m ≥ 7 events on the SJFZ increases significantly if the long record of simulated seismicity is taken into account. The model simulations indicate that the recent increased number of observed intermediate SJFZ earthquakes is a robust statistical feature heralding the occurrence of m ≥ 7 earthquakes. The hypocenters of the m ≥ 5 events in the simulation results move progressively towards the hypocenter of the upcoming m ≥ 7 earthquake.

  9. Amplitude and phase normalization of seismograms from multiple seismograph recording systems for the Yellowstone-Snake River Plain seismic refraction experiment

    SciTech Connect

    Baker, M.R.; Braile, L.W.; Smith, R.B.

    1982-04-10

    A z transform filter theory method for the normalization of the instrument responses of several seismographs is presented. In this method, an inverse filter is derived by consideration of the seismometer/recorder characteristics which may be applied to a given seismogram to convert the system frequency response to that of a reference system. Inverse filters are derived for the seismographs used on the 1978 Yellowstone-Snake River Plain seismic profiling experiment. It is shown by application to these data that the inverse filters are effective in amplitude normalization and that their use allows improvement in the amplitude and waveform character of seismic record sections.

  10. Processed seismic motion records from Little Skull Mountain, Nevada earthquake of June 29, 1992, recorded at stations in southern Nevada

    SciTech Connect

    Lum, P.K.; Honda, K.K.

    1992-12-31

    As part of the contract with the US Department of Energy, Nevada Field Office (DOE/NV), URS/John A. Blume & Associates, Engineers (URS/Blume) maintains a network of seismographs in southern Nevada to monitor the ground motion generated by the underground nuclear explosions (UNEs) at the Nevada Test Site (NTS). The seismographs are located in the communities surrounding the NTS and the Las Vegas valley. When these seismographs are not used for monitoring the UNE generated motions, a limited number of seismographs are maintained for monitoring motion generated by other than UNEs (e.g. motion generated by earthquakes, wind, blast). During the subject earthquake of June 29, 1992, a total of 20 of these systems recorded the earthquake motions. This report contains the recorded data.

  11. Processed seismic motion records from Big Bear, California earthquake of June 28, 1992, recorded at seismograph stations in southern Nevada

    SciTech Connect

    Lum, P.K.; Honda, K.K.

    1993-04-01

    As part of the contract with the US Department of Energy, Nevada Field office (DOE/NV), URS/John A. Blume & Associates, Engineers (URS/Blume) maintains a network of seismographs in southern Nevada to monitor the ground motion generated by the underground nuclear explosions (UNEs) at the Nevada Test Site (NTS). The seismographs are located in the communities surrounding the NTS and the Las Vegas valley. When these seismographs are not used for monitoring the UNE generated motions, a limited number of seismographs are maintained for monitoring motion generated by other than UNEs (e.g. motion generated by earthquakes, wind, blast). During the subject earthquake of June 28, 1992, a total of 15 of these systems recorded the earthquake motions. This report contains the recorded data.

  12. Processed seismic motion records from Landers, California earthquake of June 28, 1992, recorded at seismograph stations in southern Nevada

    SciTech Connect

    Lum, P.K.; Honda, K.K.

    1993-04-01

    As part of the contract with the US Department of Energy, Nevada Field office (DOE/NV), URS/John A. Blume & Associates, Engineers (URS/Blume) maintains a network of seismographs in southern Nevada to monitor the ground motion generated by the underground nuclear explosions (UNEs) at the Nevada Test Site (NTS). The seismographs are located in the communities surrounding the NTS and the Las Vegas valley. When these seismographs are not used for monitoring the UNE generated motions, a limited number of seismographs are maintained for monitoring motion generated by other than UNEs (e.g. motion generated by earthquakes, wind, blast). During the subject earthquake of June 28, 1992, a total of 19 of these systems recorded the earthquake motions. This report contains the recorded data.

  13. Build your own low-cost seismic/bathymetric recorder annotator

    USGS Publications Warehouse

    Robinson, W.

    1994-01-01

    An inexpensive programmable annotator, completely compatible with at least three models of widely used graphic recorders (Raytheon LSR-1811, Raytheon LSR-1807 M, and EDO 550) has been developed to automatically write event marks and print up to sixteen numbers on the paper record. Event mark and character printout intervals, character height and character position are all selectable with front panel switches. Operation is completely compatible with recorders running in either continuous or start-stop mode. ?? 1994.

  14. The preglacial sediment record of Lake Ladoga, Russia - first results from a seismic survey and sediment coring in 2013

    NASA Astrophysics Data System (ADS)

    Melles, Martin; Krastel, Sebastian; Fedorov, Grigory; Subetto, Dmitry A.; Savelieva, Larisa A.; Andreev, Andrej; Wagner, Bernd

    2014-05-01

    The new German-Russian project PLOT (Paleolimnological Transect) aims at investigating the Late Quaternary climatic and environmental history along a more than 6000 km long longitudinal transect crossing northern Eurasia. Special emphasis is put on the preglacial history. For this purpose shallow and deep seismic surveys shall be carried out on five lakes, which potentially host preglacial sediment records, followed by sediment coring based on the results of the seismic campaigns. The well-studied Lake El'gygytgyn represents the eastern-most location of the transect and acts as reference site. Within the scope of a pilot phase for the PLOT project, funded by the German Federal Ministry of Education and Research, we were able to investigate Lake Ladoga, which is located close to St. Petersburg at the western end of the transect. Lake Ladoga is the largest lake in Europe, covering an area of almost 18.000 km2. The modern sedimentation as well as the late glacial and Holocene history of the lake were already studied in detail over the past decades. The older, preglacial lake history, however, is only rudimentary known from a core transect drilled in the southern lake in the 1930th. The cores of up to about 60 m length were only briefly described and are not existing any more. The results from these cores, known from unpublished reports only, suggest the existence of marine sediments of presumably Eemian age, representing a time when Lake Lagoga was part of a precursor of the Baltic Sea, which had a connection via Ladoga and Onega Lakes to the White Sea and further to the Arctic Ocean. In late August/early September 2013 we carried out a seismic survey on Lake Ladoga using a Mini-GI-Gun and a 32-channel seismic streamer. In total, 1500 km of seismic profiles were measured, covering most parts of the lake. The seismic lines typically show acoustically well stratified Holocene muds overlaying rather transparent postglacial varves. These sediment successions can reach

  15. Investigation on the real-time prediction of ground motions using seismic records observed in deep boreholes

    NASA Astrophysics Data System (ADS)

    Miyakoshi, H.; Tsuno, S.

    2013-12-01

    The present method of the EEW system installed in the railway field of Japan predicts seismic ground motions based on the estimated earthquake information about epicentral distances and magnitudes using initial P-waves observed on the surface. In the case of local earthquakes beneath the Tokyo Metropolitan Area, however, a method to directly predict seismic ground motions using P-waves observed in deep boreholes could issue EEWs more simply and surely. Besides, a method to predict seismic ground motions, using S-waves observed in deep boreholes and S-wave velocity structures beneath seismic stations, could show planar distributions of ground motions for train operation control areas in the aftermath of earthquakes. This information is available to decide areas in which the emergency inspection of railway structures should be performed. To develop those two methods, we investigated relationships between peak amplitudes on the surface and those in deep boreholes, using seismic records of KiK-net stations in the Kanto Basin. In this study, we used earthquake accelerograms observed in boreholes whose depths are deeper than the top face of Pre-Neogene basement and those on the surface at 12 seismic stations of KiK-net. We selected 243 local earthquakes whose epicenters are located around the Kanto Region. Those JMA magnitudes are in the range from 4.5 to 7.0. We picked the on-set of P-waves and S-waves using a vertical component and two horizontal components, respectively. Peak amplitudes of P-waves and S-waves were obtained using vertical components and vector sums of two horizontal components, respectively. We estimated parameters which represent site amplification factors beneath seismic stations, using peak amplitudes of S-waves observed in the deep borehole and those on the surface, to minimize the residuals between calculations by the theoretical equation and observations. Correlation coefficients between calculations and observations are high values in the range

  16. From collision to collapse: phases of lithospheric evolution as monitored by seismic records

    NASA Astrophysics Data System (ADS)

    Meissner, Rolf; Tanner, Barbara

    1993-08-01

    Deep seismic reflection profiles in Europe and elsewhere cover a range of different tectonic units. Specifically, in western and central Europe they cross structures relating to the Alpine, Variscan and Caledonian orogens with considerable crustal shortening, delamination, and interfingering. The Variscan mountain belts in France and Germany show collapsed structures from various collision events between 300 and 350 Ma ago. Still further north in middle England and the southwest Baltic Sea traces of the Caledonian collision around 400 Ma and associated collapse structures are visible. Here, the terrain East Avalonia (Cadomia) docked to the colliding continents of Baltica and Laurentia in a complex pattern with closing oceans and compressional boundaries, which can still be seen in today's seismic sections in Britain and the SW Baltic Sea. All the processes of crustal shortening, interfingering and delamination were certainly active during the compressional stages of these earlier orogens and have left their marks, which are still recognizable in today's seismic image of the crust. Crustal roots and high elevations have disappeared in the extensional collapse phase, thermal events have intruded, 'underplated' or otherwise modified the stretched lower crust. In the Variscan internides massif granite production started, and the lower crust assumed an especially strong and thick sheared, laminated structure with a plane Moho. The various tectonic stages are illuminated by a gross analysis of reflectivity patterns. We postulate that the fate of these patterns from their origin to their death is imbedded in thermally and rheologically varying creep processes, which always accompany the brittle and ductile deformation in the Earth's crust.

  17. Seismic stratigraphy of the Antarctic Peninsula pacific margin: A record of Pliocene-Pleistocene ice volume and paleoclimate

    SciTech Connect

    Larter, R.D.; Barker, P.F. )

    1989-08-01

    Multichannel seismic profiles across the Pacific margin of the Antarctic Peninsula show a series of oblique progradational sequences. These sequences exhibit a variety of unusual characteristics that suggest they were produced by the action of ice sheets grounded out to the shelf edge at times of glacial maximum. Reflection events from deeper stratigraphic levels, followed down the continental slope and onto the rise, overlie ocean crust of known age, showing that at least eight such glacial sequences have been deposited within the past 6 m.y. Similar groundings have probably occurred on most Antarctic margins, but the depositional record is particularly well preserved at this margin because of Pliocene-Pleistocene thermal subsidence. Neogene global sea-level fluctuations have been attributed to changes in volume of continental ice sheets. The depositional sequences on the Pacific margin of the Antarctic Peninsula are thought to record West Antarctic ice-sheet fluctuations directly. Further investigation of these sequences would assess the relation between fluctuations in ice volume and the low-latitude record of global sea-level change.

  18. Historical seismometry database project: A comprehensive relational database for historical seismic records

    NASA Astrophysics Data System (ADS)

    Bono, Andrea

    2007-01-01

    The recovery and preservation of the patrimony made of the instrumental registrations regarding the historical earthquakes is with no doubt a subject of great interest. This attention, besides being purely historical, must necessarily be also scientific. In fact, the availability of a great amount of parametric information on the seismic activity in a given area is a doubtless help to the seismologic researcher's activities. In this article the project of the Sismos group of the National Institute of Geophysics and Volcanology of Rome new database is presented. In the structure of the new scheme the matured experience of five years of activity is summarized. We consider it useful for those who are approaching to "recovery and reprocess" computer based facilities. In the past years several attempts on Italian seismicity have followed each other. It has almost never been real databases. Some of them have had positive success because they were well considered and organized. In others it was limited in supplying lists of events with their relative hypocentral standards. What makes this project more interesting compared to the previous work is the completeness and the generality of the managed information. For example, it will be possible to view the hypocentral information regarding a given historical earthquake; it will be possible to research the seismograms in raster, digital or digitalized format, the information on times of arrival of the phases in the various stations, the instrumental standards and so on. The relational modern logic on which the archive is based, allows the carrying out of all these operations with little effort. The database described below will completely substitute Sismos' current data bank. Some of the organizational principles of this work are similar to those that inspire the database for the real-time monitoring of the seismicity in use in the principal offices of international research. A modern planning logic in a distinctly historical

  19. Joint interpretation of high-precision tilt data and mining induced seismic events recorded underground in deep level gold mine in South Africa

    NASA Astrophysics Data System (ADS)

    Milev, Alexander; Share, Pieter; Durrheim, Ray; Naoi, Makoto; Nakatani, Masao; Yabe, Yasuo; Ogasawara, Hiroshi

    2013-04-01

    Seismicity associated with deep-level mining has for long been a problem, leading to rockburst and other similar hazards. Several studies have been completed in an attempt to minimize the total amount of seismicity. In this study high resolution measurements of ground tilting in combination with seismic monitoring is used to observe how the rock mass responds to mining. A good correspondence between the coseismic and the aseismic tilt was found. The rate of coseismic and aseismic tilt, as well as seismicity recorded by the mine seismic network, are approximately constant until the daily blasting time, which takes place from about 19:30 until shortly before 21:00. During the blasting time and the subsequent seismic events, the coseismic and aseismic tilt shows a rapid increase. In an attempt to distinguish between the different mechanisms of tilting two types of events were recognized. The "fast" seismic events characterized with sharp increase of the tilt during the seismic rupture and "slow" seismic events characterized by creep type post seismic deformations. Tilt behaviour before and after a seismic event was also analysed. The fact that no recognizable aftertilt was observed for more of the "fast" seismic events means that there is no gradual release of stress and an associated continuous strain rate change afterwards. It can therefore be concluded that a large seismic event causes a rapid change in the state of stress rather than a gradual change in the strain rate. The mechanism of the observed "slow" seismic events is more complicated. Although several explanations have been proposed, a suggestion for further work could be to investigate the presence of "slow" events in or after blasting time more closely. During the monitoring period a seismic event with MW 2.2 occurred in the vicinity of the instrumented site. This event was recorded by both the CSIR integrated monitoring system and JAGUARS acoustic emission network. More than 21,000 AE aftershocks were

  20. Pre-instrumental seismicity in Central Africa using felt seisms recorded mainly at the meteorological stations of DRC, Rwanda and Burundi during the colonial period

    NASA Astrophysics Data System (ADS)

    Mulumba, J.-L.; Delvaux, D.

    2012-04-01

    Seismic hazard assessment and mitigation of catastrophes are primarily based on the identification and characterization of seismically active zones. These tasks still rely heavily on the existing knowledge of the seismic activity over the longest possible time period. The first seismic network in Equatorial Africa (IRSAC network) was operated from the Lwiro scientific base on the western shores of Lake Kivu between 1953 and 1963. Before this installation, the historical record of seismic activity in Central Africa is sparse. Even for the relatively short period concerned, spanning only 50-60 years, the historical record is far from being complete. A first attempt has been made by Herrinckx (1959) who compiled a list 960 felt seisms recorded at the meteorological stations between 1915 and 1954 in Congo, Rwanda and Burundi. They were used to draw a density map of felt seisms per square degree. We completed this data base by exploiting the meteorological archives and any available historical report to enlarge the database which now reaches 1513 entries between 1900 and 1959. These entries have been exanimate in order to identify possible historical seismic events. Those are defined by 3 or more quasi-simultaneous records observed over a relatively short distance (a few degrees of latitude/longitude) within a short time difference (few hours). A preliminary list of 115 possible historical seisms has been obtained, identified by 3 to 15 different stations. The proposed location is taken as the average latitude and longitude of the stations where the felt seisms were recorded. Some of the most important ones are associated to aftershocks that have been felt at some stations after the main shocks. The most recent felt seisms have been also recorded instrumentally, which helps to validate the procedure followed. The main difficulties are the magnitude estimation and the possible spatial incompleteness of the recording of felt seism evidence at the margin of the observation

  1. A new algorithm for tight integration of real-time GPS and strong-motion records, demonstrated on simulated, experimental, and real seismic data

    NASA Astrophysics Data System (ADS)

    Tu, Rui; Ge, Maorong; Wang, Rongjiang; Walter, Thomas R.

    2014-01-01

    The complementary advantages of GPS and seismic measurements are well recognized in seismotectonic monitoring studies. Therefore, integrated processing of the two data streams has been proposed recently in an attempt to obtain accurate and reliable information of surface displacements associated with earthquakes. A hitherto still critical issue in the integrated processing is real-time detection and precise estimation of the transient baseline error in the seismic records. Here, we report on a new approach by introducing the seismic acceleration corrected by baseline errors into the state equation system. The correction is performed and regularly updated in short epochs (with increments which may be as short as seconds), so that station position, velocity, and acceleration can be constrained very tightly and baseline error can be estimated as a random-walk process. With the adapted state equation system, our study highlights the use of a new approach developed for integrated processing of GPS and seismic data by means of sequential least-squares adjustment. The efficiency of our approach is demonstrated and validated using simulated, experimental, and real datasets. The latter were collected at collocated GPS and seismic stations around the 4 April 2010, E1 Mayor-Cucapah earthquake (Mw, 7.2). The results have shown that baseline errors of the strong-motion sensors are corrected precisely and high-precision seismic displacements are real-timely obtained by the new approach.

  2. Recorded seismic response of a base-isolated steel bridge carrying a steel water pipe

    USGS Publications Warehouse

    Safak, E.; Brady, A.G.

    1989-01-01

    A set of strong motion records was obtained from the base-isolated Santa Ana River Pipeline Bridge during the magnitude 5.9 Whittier Narrows, California, earthquake of October 1, 1987. The analysis of the records show that the level of excitation was not strong enough to fully activate the base isolators. The dominant modes of the response are the translations of the abutment-bridge-pipe system in the longitudinal and transverse directions, and the bending of the steel truss between supports in the vertical direction.

  3. Impact of wind on ambient noise recorded by the "13 BB star" seismic array in northern Poland

    NASA Astrophysics Data System (ADS)

    Lepore, Simone; Markowicz, Krzysztof; Grad, Marek

    2016-04-01

    Seismic interferometry and beam forming techniques were applied to ambient noise recorded during January 2014 at the "13 BB star" array, composed of thirteen seismic stations located in northern Poland, with the aim of evaluating the azimuth of noise sources and the velocities of surface waves. After normalizing the raw recordings in time and frequency domain, the spectral characteristics of the ambient noise were studied to choose a frequency band suitable for the waves' retrieval. To get the velocity of surface waves by seismic interferometry, the crosscorrelation between all station pairs was analysed for the vertical and horizontal components in the 0.05-0.1 Hz, 0.1-1 Hz and 1 10 Hz frequency bands. For each pair, the crosscorrelation was applied to one hour recordings extracted from the ambient noise. The obtained traces were calculated for a complete day, and then summed together: the daily results were stacked for the whole January 2014. In the lowest frequency range, most of the energy is located around the 3.0 km/s line, meaning that the surface waves coming from the uppermost mantle will be retrieved. The intermediate frequency range shows most of the energy between the 2.0 km/s and 1.5 km/s lines: consequently, surface waves originating from the crust will be retrieved. In the highest frequency range, the surface waves are barely visible on the crosscorrelation traces, implying that the associated energy is strongly attenuated. The azimuth variation associated to the noise field was evaluated by means of the beam forming method, using the data from the whole array for all the three components. To that, the beam power was estimated in a small range of frequencies every day for the whole month. For each day, one hour long results of beam forming applications were stacked together. To avoid aliasing and near field effects, the minimum frequency was set at 0.05 Hz and the maximum to 0.1 Hz. In this frequency band, the amplitude maximum was sought

  4. 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.

  5. Suppression of Periodic Disturbances in Seismic Aftershock Recordings for Better Localisation of Underground Explosions

    NASA Astrophysics Data System (ADS)

    Gorschlüter, Felix; Altmann, Jürgen

    2014-03-01

    For precise localisation of a potential underground nuclear explosion, the Comprehensive Nuclear-Test-Ban Treaty Organization, during an on-site inspection, can set up seismic sensors to find the very small signals from aftershocks. These signals can be masked by periodic disturbances from, for example, helicopters. We present a new method to characterise every such disturbance by the amplitude, frequency and phase of the underlying sine in the time domain using a mathematical expression for its Hann-windowed discrete Fourier transform. The contributions of these sines are computed and subtracted from the complex spectrum sequentially. Two examples show the performance of the procedure: (1) synthetic sines superposed to a coal-mine induced event, orders of magnitude stronger than the latter, can be removed successfully, (2) removal of periodic content from the signals of a helicopter overflight reduces the amplitude by a factor 3.3 when the frequencies are approximately constant. The procedure cannot yet cope with peaks that change frequency too fast, for example by the Doppler effect when passing, and with peaks that lie too close to each other. Improvement to solve these problems seems possible.

  6. One Landslide forecasting method using ground ruptures model and strong seismic records

    NASA Astrophysics Data System (ADS)

    Tang, Aiping; Cui, Yuping

    2010-05-01

    According to the assessment report of Taiwan earthquake (Ms.7.1 Sep. 21.1999) and Wenchuan earthquake (Ms.8.0, May 21.2008), there were vast ground rupture and strong ground motion to be observed in the above two events, and a great number of a landslides had also been found over a broad area,which damaged and destroyed homes and other structures, blocked roads, disrupted pipelines, and caused other serious damage like barrier lakes. So, it is very important to analysis the distribution and characteristics of landslides under earthquake dynamic loads and forecast what areas may be susceptible to landsliding in future earthquakes. Landslide disaster characteristics including frequency, distribution, and geometries etc in Taiwan and Wenchuan earthquake are summarized at first, and then the correlation between landslide spatial distribution and ground rupture, and strong earthquake motion are explored by using of statistics analysis respectively. Lastly, a landslide disaster forecasting model is built up. The model includes viscoplastic behaviors of soil and rock under seismic dynamic load, and takes into account directly the landslide spatial distribution related to earthquake intensity and ground rupture through a statistical model. A Prediction was made and compared to the results in Wenchuan earthquake.

  7. Real-time seismic monitoring of the integrated cape girardeau bridge array and recorded earthquake response

    USGS Publications Warehouse

    Celebi, M.

    2006-01-01

    This paper introduces the state of the art, real-time and broad-band seismic monitoring network implemented for the 1206 m [3956 ft] long, cable-stayed Bill Emerson Memorial Bridge in Cape Girardeau (MO), a new Mississippi River crossing, approximately 80 km from the epicentral region of the 1811-1812 New Madrid earthquakes. The bridge was designed for a strong earthquake (magnitude 7.5 or greater) during the design life of the bridge. The monitoring network comprises a total of 84 channels of accelerometers deployed on the superstructure, pier foundations and at surface and downhole free-field arrays of the bridge. The paper also presents the high quality response data obtained from the network. Such data is aimed to be used by the owner, researchers and engineers to assess the performance of the bridge, to check design parameters, including the comparison of dynamic characteristics with actual response, and to better design future similar bridges. Preliminary analyses of ambient and low amplitude small earthquake data reveal specific response characteristics of the bridge and the free-field. There is evidence of coherent tower, cable, deck interaction that sometimes results in amplified ambient motions. Motions at the lowest tri-axial downhole accelerometers on both MO and IL sides are practically free from any feedback from the bridge. Motions at the mid-level and surface downhole accelerometers are influenced significantly by feedback due to amplified ambient motions of the bridge. Copyright ASCE 2006.

  8. Characterization of the 2015 M4.0 Venus, Texas, Earthquake Sequence Using Locally Recorded Seismic Data

    NASA Astrophysics Data System (ADS)

    Scales, M. M.; DeShon, H. R.; Hayward, C.; Magnani, M. B.; Walter, J. I.; Pratt, T. L.

    2015-12-01

    We present high-resolution relative earthquake relocations derived using differential time data from waveform cross-correlation and first motion fault plane solutions to characterize the 2015 M4.0 Venus, TX, earthquake sequence. On 7 May 2015, a M4.0 earthquake occurred in Johnson County, TX, south of the Dallas-Fort Worth metroplex. It is the largest event recorded to date in the Fort Worth (Barnett Shale) Basin, which is an active shale gas production area that has been associated with induced earthquakes. The USGS moment tensor indicated normal faulting along NE-SW trending faults and two additional felt aftershocks were reported in the National Earthquake Information Center catalog. Beginning on 11 May 2015, a temporary seismic network was deployed. Over the first week, SMU deployed 13 vertical-component RT125s and 3 USGS NetQuakes instruments. The RT125s were replaced with 7 short-period 3-component instruments provided by IRIS and 4 broadband stations deployed throughout Johnson County by the University of Texas. To date, we have located over 100 events that define a 5 km long normal fault striking 35°NE and dipping ~70°. Events occur in the Precambrian granitic basement at depths of 4-6km. These locations are near the bottom of the Ellenburger Group (~3.5km in depth), which is an Ordovician carbonate platform overlying the basement and is often used for wastewater disposal. Five large volume injection wells operate within 10km of the earthquake sequence and inject very near, if not through, the Ellenburger-basement contact. These wells were temporarily shut down by the Texas Railroad Commission for testing but were reported at the time to have no causal effect on the earthquake activity. We explore temporal and spatial correlations between seismicity, wastewater injection data and subsurface fault data to better understand the cause of the Venus sequence.

  9. Seismic source functions from free-field ground motions recorded on SPE: Implications for source models of small, shallow explosions

    NASA Astrophysics Data System (ADS)

    Rougier, Esteban; Patton, Howard J.

    2015-05-01

    Reduced displacement potentials (RDPs) for chemical explosions of the Source Physics Experiments (SPE) in granite at the Nevada Nuclear Security Site are estimated from free-field ground motion recordings. Far-field P wave source functions are proportional to the time derivative of RDPs. Frequency domain comparisons between measured source functions and model predictions show that high-frequency amplitudes roll off as ω- 2, but models fail to predict the observed seismic moment, corner frequency, and spectral overshoot. All three features are fit satisfactorily for the SPE-2 test after cavity radius Rc is reduced by 12%, elastic radius is reduced by 58%, and peak-to-static pressure ratio on the elastic radius is increased by 100%, all with respect to the Mueller-Murphy model modified with the Denny-Johnson Rc scaling law. A large discrepancy is found between the cavity volume inferred from RDPs and the volume estimated from laser scans of the emplacement hole. The measurements imply a scaled Rc of ~5 m/kt1/3, more than a factor of 2 smaller than nuclear explosions. Less than 25% of the seismic moment can be attributed to cavity formation. A breakdown of the incompressibility assumption due to shear dilatancy of the source medium around the cavity is the likely explanation. New formulas are developed for volume changes due to medium bulking (or compaction). A 0.04% decrease of average density inside the elastic radius accounts for the missing volumetric moment. Assuming incompressibility, established Rc scaling laws predicted the moment reasonable well, but it was only fortuitous because dilation of the source medium compensated for the small cavity volume.

  10. Subsurface Seismic Record of Sediment Failures in the Neogene of Deepwater West Africa: Causal Mechanisms and Characteristics

    NASA Astrophysics Data System (ADS)

    Oluboyo, A. P.; Zhunussov, D.; Huuse, M.; Gawthorpe, R.

    2010-12-01

    Catastrophic sediment failures in deepwater margins are initiated by a wide range of triggering mechanisms including but not limited to; sea-level fluctuations, earthquakes, rapid sediment overburdening, progressive slope failures and gas hydrate destabilization. Three-dimensional seismic interpretation of a 1,400 km2 3D volume from the Neogene stratigraphic record of the Lower Congo Basin (LCB) demonstrates the existence of two major types of sediment failures within an elongate salt bound mini-basin (c. 15 km by 60 km). These slope instabilities are distinguished on the basis of their size, origin, geometries and deformational structures.Within the Middle Miocene, a regionally extensive, frontally emergent mass transport deposit occurs, and is a part of a much larger, regionally prevalent sediment failure deposit within the LCB. This deposit covers an area of ~ 750 km2 with an average thickness of ~ 60 m and a volume of 45 km3, with its lateral extent delimited by the salt diapirs which bound the mini-basin. Seismically, it exhibits chaotic, discontinuous, low amplitude semi-transparent facies with an erosive basal scour surface and an irregular upper bounding surface.The second type of sediment failure is a Pliocene aged, detached MTC with a short run out distance c. 10km. The slump is areally constrained to the flank of the western bounding salt-cored fold, with a preserved scarp along the fold crest. This deposit is frontally confined, with an average thickness of ~250 m and covers an area ~ 100 km2 (4 km by 26 km). It is defined by a high amplitude reflection at the base, with a series of syndepositional thrusts detaching off this surface at the terminal end of the deposit. Compressional structures are also seismically resolvable in strata adjacent to the distal end of the MTC. The presence of pressure ridges along the top bounding surface, coupled with the differential compaction of the slump deposits and mounded topography relative to local bathymetry

  11. The record of iceberg roll generated waves from sediments and seismics

    NASA Astrophysics Data System (ADS)

    Rosser, N. J.; Szczucinski, W.; Strzelecki, M.; Long, A. J.; Norman, E. C.; Dunning, S.; Drewniak, M.

    2013-12-01

    Iceberg-roll tsunamis in coastal settings have been observed to generate significant local waves, that hold potential to be recorded in coastal depositional records. Capturing the past magnitude and frequency of such events remains challenging, hindered by a lack of a good understanding of the nature, recurrence and scale of iceberg rolls, and more specifically those rolls that generate waves. Here we consider the sedimentary evidence for iceberg rolls in West Central Greenland, based upon survey of depositional environments in a range of open and confined coastal environments. We examine both an open 80 km fjord setting, and a series of confined ice-marginal beaches. We combine a detailed interpretation of sediment deposits from shore-normal transects with wider-scale high-resolution terrestrial laser scanning of sediments. Our sites - Vaigat, which separates Disko Island from the Nussuaq Peninsular, and the northern shore of Icefjord - both have a recent history of tsunamis, triggered variously by large rock avalanches, landslides and iceberg rolls. Icebergs in Vaigat and Icefjord are observed to undergo frequent failure and roll, generating - where circumstances permit - nearshore waves of meter-scale. To obtain a more detailed understanding of the likely recurrence of such iceberg roll waves and to consider their influence upon the preserved sedimentary record, we undertook an intensive 2-month monitoring campaign during sea-ice free conditions in summer 2013 to determine the patterns in the location, magnitude, frequency and timing of iceberg roll waves. Innovatively, using microseismic monitoring combined with time-lapse photography and weather monitoring, we derive a first-order model of the occurrence of iceberg roll waves. We then use this to inform our interpretation of deposits in these two environments, and consider the presence and absence of records of iceberg roll deposits in such settings. The study was funded by Polish National Science Centre grant

  12. Real-Time Seismic Monitoring of Thenewcape Girardeau (mo) Bridge and Recorded Earthquake Response

    NASA Astrophysics Data System (ADS)

    çelebi, Mehmet

    This paper introduces the state of the art, real-time and broad-band seismic monitoring network implemented for the 1206 m [3956 ft] long, cable-stayed Bill Emerson Memorial Bridge in Cape Girardeau (MO), a new Mississippi River crossing, approximately 80 km from the epicentral region of the 1811-1812 New Madrid earthquakes. Design of the bridge accounted for the possibility of a strong earthquake (magnitude 7.5 or greater) during the design life of the bridge. The monitoring network consists of a superstructure and two free-field arrays and comprises a total of 84 channels of accelerometers deployed on the superstructure, pier foundations and free-field in the vicinity of the bridge. The paper also introduces the high quality response data obtained from the network. Such data is aimed to be used by the owner, researchers and engineers to (1) assess the performance of the bridge, (2) check design parameters, including the comparison of dynamic characteristics with actual response, and (3) better design future similar bridges. Preliminary analyses of low-amplitude ambient vibration data and that from a small earthquake reveal specific response characteristics of this new bridge and the free-field in its proximity. There is coherent tower-cabledeck interaction that sometimes results in amplified ambient motions. Also, while the motions at the lowest (tri-axial) downhole accelerometers on both MO and IL sides are practically free-from any feedback from the bridge, the motions at the middle downhole and surface accelerometers are significantly influenced by amplified ambient motions of the bridge.

  13. Chimera States in Earthquake Sequencing: Preliminary Results from Global Seismic Records

    NASA Astrophysics Data System (ADS)

    Vasudevan, Kris; Cavers, Michael S.

    2015-04-01

    Earthquakes are occurrences resulting from significant stress-field alterations among faults. In general, spatio-temporal stress-field fluctuations are complex. They evolve continuously. We propose that they are akin to the dynamics of the collective behaviour of weakly-coupled non-linear "oscillators". Here, an oscillation refers to a fault-system reaching a threshold value for an earthquake occurrence at a given time and then, falling into a quiescence period during which the stress-build-up reoccurs in a prescribed manner. The duration of the quiescence period varies from one fault system to the other, depending on the forces behind it. Since mapping of global stress-field fluctuations in real time at all scales is an impossible task, we consider an earthquake zone as a proxy for a collection of weakly-coupled oscillators the dynamics of which would befit the ubiquitous Kuramoto model. In the present work, we apply the Kuramoto model to understand the non-linear dynamics on a directed graph of a sequence of global earthquakes. For directed graphs with certain properties, the Kuramoto model yields either synchronization or asynchronization. Inclusion of non-local effects evokes the occurrence of chimera states or the co-existence of synchronous and asynchronous behaviour of oscillators. In this presentation, we show how we build the model for directed graphs derived from global seismicity data. Then, we present conditions under which chimera states could occur and subsequently, point out the role of Kuramoto model in understanding the evolution of synchronous and asynchronous regions. We interpret our results with the spectral properties of directed graphs.

  14. Seismological results from the records obtained by the Seismic Alert System of Mexico (SASMEX). The analysis of the earthquake of March 20, 2012 and other examples

    NASA Astrophysics Data System (ADS)

    Ramos Perez, S.; Rodriguez Gonzalez, M.; Uribe Carvajal, A.; Espinosa Aranda, J.; Cuellar Martinez, A.

    2013-05-01

    In this talk we show seismological processes performed with data obtained from the records collected by the strong motion recorders that constitute the seismic alert system of Mexico (SASMEX). The instruments and the triggering algorithms are original design of CIRES, This has allowed that optimal time modifications, improvements and error corrections. Punctual parameters as first time arrivals, S-P times, and maximum acceleration (Amax) for each seismic station can be obtained from the warning record it self, before the earthquake arrives. When the system initiates the alert process the S-P time at least two sites are already known and at this moment common time is set in all the array which allows the synchronization of all the records, these are recovered during field trips after every trigger. The time histories are obtained by A/D converters (12 bits) and MEMS accelerometers. During the March 20, 2012 earthquake nine seismic stations of the SASMEX array detected the event at less than one hundred kilometres of epicentral distance, this allowed to calculate the location of the hypocenter, the maxima displacements associated to each of these sites. The greatest value corresponds to the Llano Grande seismic station, 0.47m on the SW direction, for the NS component. The distributions of Amax and the estimated movement displacement are shown. The foreshock of October 6 is also analysed, The behaviour of the SASMEX during the earthquakes of Tehuacan (June 15, 1999) and of Guatemala (Nov 7, 2012) are shown as examples of the possibility that the nature of the seismic activity it self point the need and probable success of increasing the coverage of SASMEX.

  15. Applying distance sampling to fin whale calls recorded by single seismic instruments in the northeast Atlantic.

    PubMed

    Harris, Danielle; Matias, Luis; Thomas, Len; Harwood, John; Geissler, Wolfram H

    2013-11-01

    Automated methods were developed to detect fin whale calls recorded by an array of ocean bottom seismometers (OBSs) deployed off the Portuguese coast between 2007 and 2008. Using recordings collected on a single day in January 2008, a standard seismological method for estimating earthquake location from single instruments, the three-component analysis, was used to estimate the relative azimuth, incidence angle, and horizontal range between each OBS and detected calls. A validation study using airgun shots, performed prior to the call analysis, indicated that the accuracy of the three-component analysis was satisfactory for this preliminary study. Point transect sampling using cue counts, a form of distance sampling, was then used to estimate the average probability of detecting a call via the array during the chosen day. This is a key step to estimating density or abundance of animals using passive acoustic data. The average probability of detection was estimated to be 0.313 (standard error: 0.033). However, fin whale density could not be estimated due to a lack of an appropriate estimate of cue (i.e., vocalization) rate. This study demonstrates the potential for using a sparse array of widely spaced, independently operating acoustic sensors, such as OBSs, for estimating cetacean density. PMID:24180763

  16. Investigation of Historic Seismic and Infrasound Records from Events Occurred at the Region of Novaya Zemplya Test Site by the USSR Stations

    NASA Astrophysics Data System (ADS)

    Sokolova, Inna

    2014-05-01

    Located in the north the Novaya Zemlya Test Site was used in Soviet time for conducting unique nuclear weapon tests in different mediums. 130 nuclear explosions with total yield 265 megatons were conducted at the Test Site for the period 1955-1990. During this period the following nuclear explosions were conducted: 1 surface explosion, 85 air explosions, 2 above water explosions, 3 underwater explosions and 39 underground explosions (in boreholes and tunnels). In addition, tectonic earthquakes and induced earthquakes caused by multi-megatons UNE occur near the Test Site. Unfortunately, only few seismic events occurred on the territory of the Test Site were recorded by digital stations. However, the archives of different seismological organizations of the USSR contain huge amount of analogue seismograms recorded by permanent and temporary stations. Historical seismograms of nuclear explosions and earthquakes from Novaya Zemlya Test site territory were digitized by the Complex Seismological Expedition IPE RAS and by the Institute of Geophysical Researches RK; a database of the events from the Test Site containing 470 seismograms at epicentral distance 2100-3800 was created. The database includes seismic records of air, underground nuclear explosions, and records of underwater nuclear explosion conducted within "Korall" exercise. In addition, infrasound records of waves from multi-megatons air nuclear explosions recorded by a microbarograph installed at Talgar seismic station at distance ~3600 km from the Test Site were digitized. Kinematic and dynamic parameters of nuclear explosions records conducted in different mediums (air, under water and underground) were investigated by the digitized records from events at Novaya Zemlya Test Site; specific features of wave pattern for each class of events were found.

  17. Problem-dependent 3-d Inversion of P-wave Arrivals From Local Events Recorded During The Svekalapko Deep Seismic Experiment In Finland

    NASA Astrophysics Data System (ADS)

    Kozlovskaya, E.; Hjelt, S.-E.; Yliniemi, J.; Korhonen, J.; Elo, S.; Svekalapko Seismic Tomography Working Group

    The SVEKALAPKO temporary seismic array was originally designed for studying the lithospheric structure beneath the southern Finland by means of teleseismic events. In addition, the high quality recordings of local seismic events (earthquakes and quarry blasts) registered by the SVEKALAPKO array contain a lot of information about the structure of the upper lithosphere beneath the southern Finland. However, the traditional local event tomography of SVEKALAPKO data cannot result in the ve- locity model valid for proper geological interpretation. The main reasons for this is the lack of the space resolution, which results in strong non-uniqueness of the to- mographic inversion. This problem can be treated by introducing various kinds of a-priori information into the inversion algorithm. The a-priori information available for the SVEKALAPKO study area includes not only the information from previous control source seismic experiments, but also potential fields data and petrophysical data. Usage of such a non-homogeneous a-priori information required a problem- dependent algorithm of seismic data inversion, which was developed on the base of non-probabilistic uncertainty measures. An example of this algorithm application to SVEKALAPKO local seismic event data is presented.

  18. Teleseismically recorded seismicity before and after the May 7, 1986, Andreanof Islands, Alaska, earthquake

    USGS Publications Warehouse

    Engdahl, E.R.; Billington, S.; Kisslinger, C.

    1989-01-01

    The Andreanof Islands earthquake (Mw 8.0) is the largest event to have occurred in that section of the Aleutian arc since the March 9, 1957, Aleutian Islands earthquake (Mw 8.6). Teleseismically well-recorded earthquakes in the region of the 1986 earthquake are relocated with a plate model and with careful attention to the focal depths. The data set is nearly complete for mb???4.7 between longitudes 172??W and 179??W for the period 1964 through April 1987 and provides a detailed description of the space-time history of moderate-size earthquakes in the region for that period. Additional insight is provided by source parameters which have been systematically determined for Mw???5 earthquakes that occurred in the region since 1977 and by a modeling study of the spatial distribution of moment release on the mainshock fault plane. -from Authors

  19. Broadband recording of Strombolian explosions and associated very-long-period seismic signals on Mount Erebus Volcano, Ross Island, Antarctica

    NASA Astrophysics Data System (ADS)

    Rowe, C. A.; Aster, R. C.; Kyle, P. R.; Schlue, J. W.; Dibble, R. R.

    In December 1996 and January 1997, broadband seismometers were deployed on the summit plateau of Mount Erebus at radial distances of 0.7, 1.4 and 1.9 km from the central crater and lava lake. Strombolian explosions at Erebus previously have been observed to produce seismic and acoustic energy between 1 and 6 Hz. New observations document significant energy with spectral peaks as grave as 20 s. Nearly identical very-long-period (VLP) signals begin ∼1.5 s prior to explosions, have dilatational onsets and persist for up to 150 s. Similar VLP waveforms were recorded at all three stations, indicating that the seismograms are essentially source-dominated. Particle motions suggest an initial depth for the VLP source of up to several hundred meters, migrating deeper in the course of ∼15 s. Such explosion-associated VLP signals may indicate a nondestructive lossy resonance or nonlinear fluid-flow excitation within the shallow magmatic system.

  20. Trajectory of the August 7, 2010 Biwako fireball determined from seismic recordings

    NASA Astrophysics Data System (ADS)

    Yamada, Masumi; Mori, Jim

    2012-01-01

    The Biwako fireball on August 7, 2010, produced a strong sonic boom throughout central Japan around 17:00 JST (UTC+9). There were many visual observations and reports of the sound in the Tokai and Kinki regions at that time. We have estimated the trajectory of this fireball and the location of its termination point by analyzing seismograms recorded on a dense local network. The isochrons of the arrival times are close to concentric circles, which suggest that the fireball disappeared due to fragmentation during entry. The fireball trajectory which explains the arrival times of the signal has a relatively high incident angle (55 degrees relative to the horizon) and the source is thought to disappear at a height of 26-km east of Lake Biwa. The azimuthal angle and velocity of the fireball are difficult to determine uniquely from this dataset. We identified an event thought to be due to fragmentation, with a location 3-km ENE and 9-km higher than the termination point. This location is consistent with the trajectory determined from the signal arrival. Based on this trajectory model, the source of the signal spans a horizontal range of 26 to 70 km, and the altitude of the source producing the sonic boom is about 30 to 50 km.

  1. First seismic survey of Lake Saint-Jean (Québec, Canada): sedimentary record of the last deglaciation

    NASA Astrophysics Data System (ADS)

    Nutz, Alexis; Schuster, Mathieu; Ghienne, Jean-François; Raphaël, Certain; Nicolas, Robin; Claude, Roquin; Frédéric, Bouchette; Cousineau Pierre, A.

    2015-04-01

    The general post-glacial evolution of the Lake Saint-Jean region (Canada/Québec) was, until now, only known from onshore studies (outcrops and geomorphology). Because this lake corresponds to sediment depocentre since the area is ice free (latest Pleistocene and the entire Holocene), a comprehensive sedimentary archive could be expected from this area. As a consequence, the offshore archives of Lake Saint-Jean leave a basic, but crucial, question: can the transition from glacial to post-glacial periods be deciphered? The stratigraphy of the last deglacial sequence is investigated in Lake Saint-Jean (Québec, Canada) from 300 km of echo-sounder 2D seismic profiles. The sedimentary archive of this basin is documented from the Late Pleistocene Laurentidian ice-front recession to the present-day situation. Ten seismic units have been identified that reflect spatio-temporal variations in depositional processes characterizing different periods of the Lake Saint-Jean basin evolution. During the postglacial marine flooding, a high deposition rate of mud settling, from proglacial glacimarine and then prodeltaic plumes in the Laflamme Gulf, produced an extensive, up to 50 m thick mud sheet draping the isostatically depressed marine basin floor. Subsequently, closing of the water body due to glacio-isostatic rebound that occurred at 8.5 cal. ka BP and ice-sheet retreat outside the Saint-Jean catchment at 7.5 cal. ka BP drastically modify the hydrodynamics and sedimentation. Hyperpycnal flows appeared because fresh lake water replaced dense marine water. River sediments were transferred towards the deeper part of the lake into river-related confined lobes. The water body is also marked by the onset of a wind-driven internal circulation associating wave-related hydrodynamics and bottom currents with sedimentary features including shoreface deposits, sediment drifts, a sedimentary shelf and important erosional surfaces. The Lake Saint-Jean reveals important diversity and

  2. Toward Improved Methods of Estimating Attenuation, Phase and Group velocity of surface waves observed on Shallow Seismic Records

    NASA Astrophysics Data System (ADS)

    Diallo, M. S.; Holschneider, M.; Kulesh, M.; Scherbaum, F.; Ohrnberger, M.; Lück, E.

    2004-05-01

    This contribution is concerned with the estimate of attenuation and dispersion characteristics of surface waves observed on a shallow seismic record. The analysis is based on a initial parameterization of the phase and attenuation functions which are then estimated by minimizing a properly defined merit function. To minimize the effect of random noise on the estimates of dispersion and attenuation we use cross-correlations (in Fourier domain) of preselected traces from some region of interest along the survey line. These cross-correlations are then expressed in terms of the parameterized attenuation and phase functions and the auto-correlation of the so-called source trace or reference trace. Cross-corelation that enter the optimization are selected so as to provide an average estimate of both the attenuation function and the phase (group) velocity of the area under investigation. The advantage of the method over the standard two stations method using Fourier technique is that uncertainties related to the phase unwrapping and the estimate of the number of 2π cycle skip in the phase phase are eliminated. However when mutliple modes arrival are observed, its become merely impossible to obtain reliable estimate the dipsersion curves for the different modes using optimization method alone. To circumvent this limitations we using the presented approach in conjunction with the wavelet propagation operator (Kulesh et al., 2003) which allows the application of band pass filtering in (ω -t) domain, to select a particular mode for the minimization. Also by expressing the cost function in the wavelet domain the optimization can be performed either with respect to the phase, the modulus of the transform or a combination of both. This flexibility in the design of the cost function provides an additional mean of constraining the optimization results. Results from the application of this dispersion and attenuation analysis method are shown for both synthetic and real 2D shallow

  3. Analysis and models of pre-injection surface seismic array noise recorded at the Aquistore carbon storage site

    NASA Astrophysics Data System (ADS)

    Birnie, Claire; Chambers, Kit; Angus, Doug; Stork, Anna

    2016-05-01

    Noise is a persistent feature in seismic data and so poses challenges in extracting increased accuracy in seismic images and physical interpretation of the subsurface. In this paper, we analyse passive seismic data from the Aquistore carbon capture and storage pilot project permanent seismic array to characterise, classify and model seismic noise. We perform noise analysis for a three month subset of passive seismic data from the array and provide conclusive evidence that the noise field is not white, stationary, or Gaussian; characteristics commonly yet erroneously assumed in most conventional noise models. We introduce a novel noise modelling method that provides a significantly more accurate characterisation of real seismic noise compared to conventional methods, which is quantified using the Mann-Whitney-White statistical test. This method is based on a statistical covariance modelling approach created through the modelling of individual noise signals. The identification of individual noise signals, broadly classified as stationary, pseudo-stationary and non-stationary, provides a basis on which to build an appropriate spatial and temporal noise field model. Furthermore, we have developed a workflow to incorporate realistic noise models within synthetic seismic datasets providing an opportunity to test and analyse detection and imaging algorithms under realistic noise conditions.

  4. Analysis and models of pre-injection surface seismic array noise recorded at the Aquistore carbon storage site

    NASA Astrophysics Data System (ADS)

    Birnie, Claire; Chambers, Kit; Angus, Doug; Stork, Anna L.

    2016-08-01

    Noise is a persistent feature in seismic data and so poses challenges in extracting increased accuracy in seismic images and physical interpretation of the subsurface. In this paper, we analyse passive seismic data from the Aquistore carbon capture and storage pilot project permanent seismic array to characterise, classify and model seismic noise. We perform noise analysis for a three-month subset of passive seismic data from the array and provide conclusive evidence that the noise field is not white, stationary, or Gaussian; characteristics commonly yet erroneously assumed in most conventional noise models. We introduce a novel noise modelling method that provides a significantly more accurate characterisation of real seismic noise compared to conventional methods, which is quantified using the Mann-Whitney-White statistical test. This method is based on a statistical covariance modelling approach created through the modelling of individual noise signals. The identification of individual noise signals, broadly classified as stationary, pseudo-stationary and non-stationary, provides a basis on which to build an appropriate spatial and temporal noise field model. Furthermore, we have developed a workflow to incorporate realistic noise models within synthetic seismic data sets providing an opportunity to test and analyse detection and imaging algorithms under realistic noise conditions.

  5. 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.

  6. Friction weakening in granular flows deduced from seismic records at the Soufrière Hills Volcano, Montserrat

    NASA Astrophysics Data System (ADS)

    Levy, Clara; Mangeney, Anne; Bonilla, Fabian; Hibert, Clément; Calder, Eliza S.; Smith, Patrick J.

    2015-11-01

    Accurate modeling of rockfalls and pyroclastic flows is still an open issue, partly due to a lack of measurements related to their dynamics. Using seismic data from the Soufrière Hills Volcano, Montserrat, and granular flow modeling, we show that the power laws relating the seismic energy Es to the seismic duration ts and relating the loss of potential energy ΔEp to the flow duration tf are very similar, like the power laws observed at Piton de la Fournaise, Reunion Island. Observations showing that tf≃ts suggest a constant ratio Es/ΔEp≃10-5. This similarity in these two power laws can be obtained only when the granular flow model uses a friction coefficient that decreases with the volume transported. Furthermore, with this volume-dependent friction coefficient, the simulated force applied by the flow to the ground correlates well with the seismic energy, highlighting the signature of this friction weakening effect in seismic data.

  7. Late-stage stretching and subsidence rates in the Danakil Depression, evidenced from borehole records and seismic reflection data

    NASA Astrophysics Data System (ADS)

    Booth, Adam; Bastow, Ian; Magee, Craig; Keir, Derek; Corti, Giacomo; Jackson, Chris; Wilkinson, Jason

    2016-04-01

    The Ethiopian and Afar Rift systems provide a globally unique opportunity to study the incipient transition from continental rifting to sea-floor spreading. A consensus has emerged that a considerable proportion of plate extension in Ethiopia is accommodated by dyke intrusion, with smaller contributions from crustal thinning. However, observations of thinned crust and a pulse in Quaternary-Recent basaltic volcanism within Ethiopia's Danakil Depression have been cited (Bastow and Keir, 2011) as evidence that localised plate stretching may mark the final stages of continent-ocean transition. We explore this hypothesis using an archive of five 2-D seismic reflection profiles, each between 7-10 km in length, and ˜120 borehole records distributed over an area of 225 km2. From depth and age relationships of key marker horizons, we also suggest local subsidence and extension rates. The borehole archive reveals extensive evaporite sequences deposited in and around an asymmetric basin, bounded to the west by a network of east-dipping normal faults. West of the basin, the maximum observed thickness of evaporites is 150 m, beneath which are deposits of clastic sediment, but a sequence of evaporites at least 900 m thick is observed at the basin centre. The sedimentary architecture of these sequences suggests deposition in a shallow salt-pan environment, with seasonal - potentially diurnal - freshening of the brine supply (Warren, 2012). Isotopic analysis of reef carbonates in the basin flank dates the last marine incursion into the Danakil Depression at 24-230ka (Lalou et al., 1970; Bonatti et al., 1971; Bannert et al., 1971), therefore the evaporite sequence must be younger than this. A key marker horizon within the evaporites is the potash-bearing Houston Formation, also distinct in borehole records given its high porosity (25-40%) and radioactivity (50-250 API units). The elevation of the Houston Formation is ˜500 m deeper in the centre of the basin than on the flank

  8. Late 18th to early 19th century sea-level history and inter-seismic behavior along the western Myanmar plate boundary belt recorded by coral microatolls

    NASA Astrophysics Data System (ADS)

    Liu, Sze-Chieh; Shyu, J. Bruce H.

    2016-04-01

    Along the western Myanmar plate boundary belt, the Indian-Australian plate is subducting obliquely beneath the Burma micro-plate at a rate of about 23 mm/yr. Although information about the 1762 Arakan earthquake, the only major historical event occurred along this plate boundary belt, has been delineated recently from uplifted coastal features, constraints on the inter-seismic behavior of this belt is still very limited, due to the lack of high resolution instrumental records in the area. Therefore, we utilized coral microatolls to analyze relative sea level history, in order to obtain potential information of land-level change along the western coast of Myanmar. Our sample was collected from northwestern Ramree Island, approximately 80 km away from the trench. Previous studies suggest that the coral was uplifted and killed during a local earthquake event in 1848, and recorded relative sea level history of ~80 years prior to that event. Since the highest level of survival (HLS) of coral microatolls is constrained within a few centimeters of the lowest tide level of the area, the patterns of annual growth bands of the coral microatoll in x-radiograph provide us yearly record of relative sea level, and we used U-Th dating technique to constrain the age of the coral. Our results show that this coral microatoll may have recorded the inter-seismic subsidence of northwestern Ramree Island, punctuated by several climatic events that produced die-down records of the coral growth bands. We hope the data obtained from this coral microatoll, combined with previously reported information of the area, will enable us to further understand the seismic behavior of this major plate boundary belt.

  9. Array analyses of volcanic earthquakes and tremor recorded at Las Cañadas caldera (Tenerife Island, Spain) during the 2004 seismic activation of Teide volcano

    NASA Astrophysics Data System (ADS)

    Almendros, Javier; Ibáñez, Jesús M.; Carmona, Enrique; Zandomeneghi, Daria

    2007-02-01

    We analyze data from three seismic antennas deployed in Las Cañadas caldera (Tenerife) during May-July 2004. The period selected for the analysis (May 12-31, 2004) constitutes one of the most active seismic episodes reported in the area, except for the precursory seismicity accompanying historical eruptions. Most seismic signals recorded by the antennas were volcano-tectonic (VT) earthquakes. They usually exhibited low magnitudes, although some of them were large enough to be felt at nearby villages. A few long-period (LP) events, generally associated with the presence of volcanic fluids in the medium, were also detected. Furthermore, we detected the appearance of a continuous tremor that started on May 18 and lasted for several weeks, at least until the end of the recording period. It is the first time that volcanic tremor has been reported at Teide volcano. This tremor was a small-amplitude, narrow-band signal with central frequency in the range 1-6 Hz. It was detected at the three antennas located in Las Cañadas caldera. We applied the zero-lag cross-correlation (ZLCC) method to estimate the propagation parameters (back-azimuth and apparent slowness) of the recorded signals. For VT earthquakes, we also determined the S-P times and source locations. Our results indicate that at the beginning of the analyzed period most earthquakes clustered in a deep volume below the northwest flank of Teide volcano. The similarity of the propagation parameters obtained for LP events and these early VT earthquakes suggests that LP events might also originate within the source volume of the VT cluster. During the last two weeks of May, VT earthquakes were generally shallower, and spread all over Las Cañadas caldera. Finally, the analysis of the tremor wavefield points to the presence of multiple, low-energy sources acting simultaneously. We propose a model to explain the pattern of seismicity observed at Teide volcano. The process started in early April with a deep magma

  10. Strong ground motion generated by controlled blasting experiments and mining induced seismic events recorded underground at deep level mines in South Africa

    NASA Astrophysics Data System (ADS)

    Milev, A.; Selllers, E.; Skorpen, L.; Scheepers, L.; Murphy, S.; Spottiswoode, S. M.

    2011-12-01

    A number of simulated rockbursts were conducted underground at deep level gold mines in South Africa in order to estimate the rock mass response when subjected to strong ground motion. The rockbursts were simulated by means of large blasts detonated in solid rock close to the sidewall of a tunnel. The simulated rockbursts involved the design of the seismic source, seismic observations in the near and far field, high-speed video filming, a study of rock mass conditions such as fractures, joints, rock strength etc. Knowledge of the site conditions before and after the simulated rockbursts was also gained. The numerical models used in the design of the simulated rockbursts were calibrated by small blasts taking place at each experimental site. A dense array of shock type accelerometers was installed along the blasting wall to monitor the attenuation of the strong ground motion as a function of the distance from the source. The attenuation of peak particle velocities, was found to be proportional to R^-1.7. Special investigations were carried out to evaluate the mechanism and the magnitude of damage, as well as the support behaviour under excessive dynamic loading. The strong ground motion generated by mining induced seismic events was studied, as part of this work, not only to characterize the rock mass response, but also to estimate the site effect on the surface of the underground excavations. A stand-alone instrument especially designed for recording strong ground motions was used to create a large database of peak particle velocities measured on stope hangingwalls. A total number of 58 sites located in stopes where the Carbon Leader Reef, Ventersdorp Contact Reef, Vaal Reef and Basal Reef are mined, were monitored. The peak particle velocities were measured at the surface of the excavations to identify the effect of the free surface and the fractures surrounding the underground mining. Based on these measurements the generally accepted velocity criterion of 3 m

  11. Friction weakening in granular flows deduced from seismic records at the Soufrière Hills Volcano, Montserrat

    NASA Astrophysics Data System (ADS)

    Levy, Clara; Mangeney, Anne; Bonilla, Fabian; Hibert, Clément; Calder, Eliza; Smith, Paddy

    2015-04-01

    Accurate modelling of rockfalls and pyroclastic flows is still an open issue, partly due the lack of measurements related to the dynamics of such events. Using seismic data from the Soufrière Hills Volcano and granular flow modelling, we show that the power laws relating the seismic energy Es to the seismic duration ts and relating the loss of potential energy ΔEp to the flow duration tf are very similar (Ei ≈ tiβ with i = s,p), as observed previously at Piton de la Fournaise, Reunion Island. Observations showing that tf ≃ ts suggest a constant ratio Es/ΔEp ≃ 10-5. This similarity in the power laws can be obtained only when the granular flow model uses a friction coefficient that decreases with the volume involved. Furthermore, with this volume-dependent friction coefficient, the simulated force applied by the flow to the ground correlates well with the seismic energy, highlighting the signature of this friction weakening effect in seismic data.

  12. Seismic Symphonies

    NASA Astrophysics Data System (ADS)

    Strinna, Elisa; Ferrari, Graziano

    2015-04-01

    The project started in 2008 as a sound installation, a collaboration between an artist, a barrel organ builder and a seismologist. The work differs from other attempts of sound transposition of seismic records. In this case seismic frequencies are not converted automatically into the "sound of the earthquake." However, it has been studied a musical translation system that, based on the organ tonal scale, generates a totally unexpected sequence of sounds which is intended to evoke the emotions aroused by the earthquake. The symphonies proposed in the project have somewhat peculiar origins: they in fact come to life from the translation of graphic tracks into a sound track. The graphic tracks in question are made up by copies of seismograms recorded during some earthquakes that have taken place around the world. Seismograms are translated into music by a sculpture-instrument, half a seismograph and half a barrel organ. The organ plays through holes practiced on paper. Adapting the documents to the instrument score, holes have been drilled on the waves' peaks. The organ covers about three tonal scales, starting from heavy and deep sounds it reaches up to high and jarring notes. The translation of the seismic records is based on a criterion that does match the highest sounds to larger amplitudes with lower ones to minors. Translating the seismogram in the organ score, the larger the amplitude of recorded waves, the more the seismogram covers the full tonal scale played by the barrel organ and the notes arouse an intense emotional response in the listener. Elisa Strinna's Seismic Symphonies installation becomes an unprecedented tool for emotional involvement, through which can be revived the memory of the greatest disasters of over a century of seismic history of the Earth. A bridge between art and science. Seismic Symphonies is also a symbolic inversion: the instrument of the organ is most commonly used in churches, and its sounds are derived from the heavens and

  13. The April 2009 L'Aquila (Italy) seismic sequence: recordings in the Anfiteatro Flavio (Colosseum)

    NASA Astrophysics Data System (ADS)

    Caserta, A.; Marra, F.; Cara, F.; Valente, G.

    2015-12-01

    We show a preliminary study concerning the interaction of the seismic wave-field coming from aftershocks of the 2009 seismic sequence in Abruzzo and the structure of the Anfiteatro Flavio, usually called Colosseum. By using mainly Arias intensity, we assess how the incoming energy beneath the foundations is convoyed into the monument, through what preferential frequencies such process takes place, how the trapped energy increases amplitude vibration with floors. Moreover, we also investigate the role played by the near-surface geology in generating differential motions below the monument foundations. In addition we also check, in a preliminary way, the foundation dynamical behaviour under the action of the incoming wave-field.

  14. Low-sensitivity acceleration seismic records obtained on sea floor in the source region of the 2004 Sumatra-Andaman Earthquake

    NASA Astrophysics Data System (ADS)

    Shinohara, M.; Yamada, T.; Kanazawa, T.

    2005-12-01

    To understand characteristics of large earthquakes occurred in a subduction zone, it is necessary to study an asperity where large earthquakes occur repeatedly. Because observation near an asperity is needed for studies of asperities, ocean bottom seismometer (OBS) is essential to observe seismic waves from earthquakes in subduction area. Since a conventional OBS is designed for high-sensitivity observation, OBS records of large earthquake occurred near OBS are often saturated. To record large amplitude seismic waves, a servo-type accelerometer is suitable. However it was difficult for OBS to use an accelerometer due to large electric power consumption. Recently a servo-type accelerometer with a large dynamic range and low-power consumption is being developed. In addition, a pressure vessel of OBS can contain much more batteries by using a large size titanium sphere. For the long-term sea floor observation of aftershock of the 2004 Sumatra-Andaman earthquake, we installed a small three-component accelerometer in a conventional long-term OBS and obtained both high-sensitivity seismogram and low-sensitivity (strong motion) accelerograms on the sea floor. We used a compact three-component servo-type accelerometer whose weight is 85 grams as a seismic sensor. Measurement range and resolution of the sensor are 3 G and 10-5 G. The sensor was directly attached to the inside of the pressure vessel. Signals from the accelerometer were digitally recorded to Compact Flash memory with 16 bit resolution and a sampling frequency of 100 Hz. The OBS with the accelerometer was deployed on February 24, 2005 in a southern part of the source region of the 2004 Sumatra-Andaman earthquake by R/V Natsushima belonging to JAMSTEC, and recovered on August 3 by R/V Baruna Jaya I belonging to BPPT, Indonesia. The accelerograms were obtained from the deployment to April 13 when the CF memory became full. Although there are some small troubles for the recording, we could obtain low

  15. Ground motions recorded in Rome during the April 2009 L’Aquila seismic sequence: site response and comparison with ground‐motion predictions based on a global dataset

    USGS Publications Warehouse

    Caserta, Arrigo; Boore, David; Rovelli, Antonio; Govoni, Aladino; Marra, Fabrizio; Monica, Gieseppe Della; Boschi, Enzo

    2013-01-01

    The mainshock and moderate‐magnitude aftershocks of the 6 April 2009 M 6.3 L’Aquila seismic sequence, about 90 km northeast of Rome, provided the first earthquake ground‐motion recordings in the urban area of Rome. Before those recordings were obtained, the assessments of the seismic hazard in Rome were based on intensity observations and theoretical considerations. The L’Aquila recordings offer an unprecedented opportunity to calibrate the city response to central Apennine earthquakes—earthquakes that have been responsible for the largest damage to Rome in historical times. Using the data recorded in Rome in April 2009, we show that (1) published theoretical predictions of a 1 s resonance in the Tiber valley are confirmed by observations showing a significant amplitude increase in response spectra at that period, (2) the empirical soil‐transfer functions inferred from spectral ratios are satisfactorily fit through 1D models using the available geological, geophysical, and laboratory data, but local variability can be large for individual events, (3) response spectra for the motions recorded in Rome from the L’Aquila earthquakes are significantly amplified in the radial component at periods near 1 s, even at a firm site on volcanic rocks, and (4) short‐period response spectra are smaller than expected when compared to ground‐motion predictions from equations based on a global dataset, whereas the observed response spectra are higher than expected for periods near 1 s.

  16. Source locations of teleseismic P, SV, and SH waves observed in microseisms recorded by a large aperture seismic array in China

    NASA Astrophysics Data System (ADS)

    Liu, Qiaoxia; Koper, Keith D.; Burlacu, Relu; Ni, Sidao; Wang, Fuyun; Zou, Changqiao; Wei, Yunhao; Gal, Martin; Reading, Anya M.

    2016-09-01

    Transversely polarized seismic waves are routinely observed in ambient seismic energy across a wide range of periods, however their origin is poorly understood because the corresponding source regions are either undefined or weakly constrained, and nearly all models of microseism generation incorporate a vertically oriented single force as the excitation mechanism. To better understand the origin of transversely polarized energy in the ambient seismic wavefield we make the first systematic attempt to locate the source regions of teleseismic SH waves observed in microseismic (2.5-20 s) noise. We focus on body waves instead of surface waves because the source regions can be constrained in both azimuth and distance using conventional array techniques. To locate microseismic sources of SH waves (as well as SV and P waves) we continuously backproject the vertical, radial, and transverse components of the ambient seismic wavefield recorded by a large-aperture array deployed in China during 2013-2014. As expected, persistent P wave sources are observed in the North Atlantic, North Pacific, and Indian Oceans, mainly at periods of 2.5-10 s, in regions with the strong ocean wave interactions needed to produce secondary microseisms. SV waves are commonly observed to originate from locations indistinguishable from the P wave sources, but with smaller signal-to-noise ratios. We also observe SH waves with about half or less the signal-to-noise ratio of SV waves. SH source regions are definitively located in deep water portions of the Pacific, away from the sloping continental shelves that are thought to be important for the generation of microseismic Love waves, but nearby regions that routinely generate teleseismic P waves. The excitation mechanism for the observed SH waves may therefore be related to the interaction of P waves with small-wavelength bathymetric features, such as seamounts and basins, through some sort of scattering process.

  17. The seismic-stratigraphic record of lake-level fluctuations in Lake Challa: Hydrological stability and change in equatorial East Africa over the last 140 kyr

    NASA Astrophysics Data System (ADS)

    Moernaut, J.; Verschuren, D.; Charlet, F.; Kristen, I.; Fagot, M.; De Batist, M.

    2010-02-01

    Seismic-reflection data from crater lake Challa (Mt. Kilimanjaro, equatorial East Africa) reveal a ˜ 210-m thick sedimentary infill containing distinct seismic-stratigraphic signatures of late-Quaternary lake-level fluctuations. Extrapolation of a well-constrained age model on the cored upper part of the sequence suggests that these lake-level fluctuations represent a detailed and continuous record of moisture-balance variation in equatorial East Africa over the last 140 kyr. This record indicates that the most severe aridity occurred during peak Penultimate glaciation immediately before ˜ 128 kyr BP (coeval with Heinrich event 11) and during a Last Interglacial 'megadrought' period between ˜ 114 and ˜ 97 kyr BP; in comparison, Last Glacial Maximum (LGM) aridity was modest. It was preceded by ˜ 75 000 years of relatively stable and moist climate conditions interrupted by eleven short-lived dry spells, five of which match the timing of Heinrich events 2 to 6. Climate history near the East African equator reflects variation in the precessional forcing of monsoon rainfall modulated by orbital eccentricity, but precession-driven moisture fluctuations were less extreme than those observed in northern and southern tropical Africa. The near-continuous moist climate from ˜ 97 to 20.5 kyr BP recorded in the Lake Challa record contrasts with the trend towards greater aridity after ˜ 70 kyr BP documented in equatorial West Africa. This long period of moist glacial climate and a short, relatively modest LGM drought can be attributed to greater independence of western Indian Ocean monsoon dynamics from northern high-latitude glaciation than those in the tropical Atlantic Ocean. This rather persistent moist glacial climate regime may have helped maintain high biodiversity in the tropical forest ecosystems of the Eastern Arc mountains in Tanzania.

  18. Crustal migration of CO2-rich magmatic fluids recorded by tree-ring radiocarbon and seismicity at Mammoth Mountain, CA, USA

    NASA Astrophysics Data System (ADS)

    Lewicki, J. L.; Hilley, G. E.; Shelly, D. R.; King, J. C.; McGeehin, J. P.; Mangan, M.; Evans, W. C.

    2014-03-01

    Unrest at Mammoth Mountain over the past several decades, manifest by seismicity, ground deformation, diffuse CO2 emissions, and elevated He3/He4 ratios in fumarolic gases has been driven by the release of CO2-rich fluids from basaltic intrusions in the middle to lower crust. Recent unrest included the occurrence of three lower-crustal (32-19 km depth) seismic swarms beneath Mammoth Mountain in 2006, 2008 and 2009 that were consistently followed by peaks in the occurrence rate of shallow (⩽10 km depth) earthquakes. We measured C14 in the growth rings (1998-2012) of a tree growing in the largest (∼0.3 km) area of diffuse CO2 emissions on Mammoth Mountain (the Horseshoe Lake tree kill; HLTK) and applied atmospheric CO2 concentration source area modeling to confirm that the tree was a reliable integrator of magmatic CO2 emissions over most of this area. The tree-ring C14 record implied that magmatic CO2 emissions from the HLTK were relatively stable from 1998 to 2009, nearly doubled from 2009 to 2011, and then declined by the 2012 growing season. The initial increase in CO2 emissions was detected during the growing season that immediately followed the largest (February 2010) peak in the occurrence rate of shallow earthquakes. Migration of CO2-rich magmatic fluids may have driven observed patterns of elevated deep, then shallow seismicity, while the relationship between pore fluid pressures within a shallow (upper 3 km of crust) fluid reservoir and permeability structure of the reservoir cap rock may have controlled the temporal pattern of surface CO2 emissions.

  19. Crustal migration of CO2-rich magmatic fluids recorded by tree-ring radiocarbon and seismicity at Mammoth Mountain, CA, USA

    USGS Publications Warehouse

    Lewicki, Jennifer L.; Hilley, George E.; Shelly, David R.; King, John C.; McGeehin, John P.; Mangan, Margaret T.; Evans, William C.

    2014-01-01

    Unrest at Mammoth Mountain over the past several decades, manifest by seismicity, ground deformation, diffuse CO2 emissions, and elevated 3He/4He ratios in fumarolic gases has been driven by the release of CO2-rich fluids from basaltic intrusions in the middle to lower crust. Recent unrest included the occurrence of three lower-crustal (32–19 km depth) seismic swarms beneath Mammoth Mountain in 2006, 2008 and 2009 that were consistently followed by peaks in the occurrence rate of shallow (≤10 km depth) earthquakes. We measured 14C in the growth rings (1998–2012) of a tree growing in the largest (∼0.3 km2) area of diffuse CO2 emissions on Mammoth Mountain (the Horseshoe Lake tree kill; HLTK) and applied atmospheric CO2 concentration source area modeling to confirm that the tree was a reliable integrator of magmatic CO2 emissions over most of this area. The tree-ring 14C record implied that magmatic CO2 emissions from the HLTK were relatively stable from 1998 to 2009, nearly doubled from 2009 to 2011, and then declined by the 2012 growing season. The initial increase in CO2 emissions was detected during the growing season that immediately followed the largest (February 2010) peak in the occurrence rate of shallow earthquakes. Migration of CO2-rich magmatic fluids may have driven observed patterns of elevated deep, then shallow seismicity, while the relationship between pore fluid pressures within a shallow (upper 3 km of crust) fluid reservoir and permeability structure of the reservoir cap rock may have controlled the temporal pattern of surface CO2 emissions.

  20. Micro-seismicity recorded during a gallery excavation in the Opalinus Clay of the Mont Terri URL: preliminary description of in situ damage mechanism

    NASA Astrophysics Data System (ADS)

    Le Gonidec, Y.; Wassermann, J.; Nussbaum, C. O.; Gibert, D.; Sarout, J.

    2012-12-01

    A gallery Ga08 has been excavated in August 2008 in the Opalinus Clay formation at the Mont Terri Underground Rock Laboratory to join the end-face of the pre-existing gallery Ga04. In situ acoustic experiments were performed to monitor the evolution of the induced Excavation Damaged Zone (EDZ): the end-face of Ga04 was instrumented with acoustic transducers allowing for both active (acoustic surveys) and passive (acoustic emissions, AE) seismic monitoring. The multifrequency acoustic surveys put in evidence the heterogeneous structure of the rock mass, which acts as a frequency filterfor acoustic waves, and its elastic anisotropy properties modeled by using the Thomsen's Weak Transverse Isotropy model. The in situ acoustic emissions, recorded during and following the excavation of the Ga08 gallery, put in evidence the activity of the excavation process mainly located on the excavated face, only few AE sources being localized inside the rock mass. Some are associated to good quality seismic traces and we attempt to analyze the mechanisms of the associated sources to inform about the damage mechanisms related to the gallery excavation.

  1. Toward the Autonomous Recording and Transmission of Seismic Data from the Oceans: Testing the Son-O-Mermaid Float in the Sargasso Sea

    NASA Astrophysics Data System (ADS)

    Simon, J. D.; Simons, F. J.; Vincent, H. T.; Nolet, G.

    2015-12-01

    We report on the deployment of two new Son-O-Mermaid floats into theSargasso Sea during a cruise aboard the R/V Atlantic Explorer, whichdeparted from Bermuda in May of 2015. Son-O-Mermaid is a freelyfloating and autonomous oceangoing system composed of a surface buoyconnected to a length of cable from which a three-hydrophone array issuspended. The main objective of the Son-O-Mermaid project is torecord signals suitable for global tomography in the deep ocean andprovide the seismic community with an abundance of novel raypaths frompreviously unsampled regions of the Earth. The Son-O-Mermaid float,with its ability to continually record, analyze, and transmit seismicdata from the oceans in near-real time has the potential torevolutionize the field of seismology. We analyze new data returnedfrom this deployment, a previous Son-O-Mermaid test, as well as theongoing MERMAID mission in the time, spectral, and wavelet domains. Afull description of the float and deployment report will be presented.A short-term goal of the project is determining realistic magnitude,distance, and pressure relationships for teleseismic earthquakes thatare recorded in the water column. Our analysis of this question isaided by synthetics created using SPECFEM2D and guided by the data,especially noise records recorded by Son-O-Mermaid and MERMAID fromoceans throughout the world. Synthetics provide an idealized waveformuseful for understanding the often very messy and noisy arrivalscommon in midcolumn acoustic recordings. Notably, synthetics allowthe confirmation or rejection of unlikely phases which are matched toearthquake databases after arrivals are detected by automatic pickingalgorithms. Additionally, marine-acoustic processing techniques willbe improved once the underwater acoustic field is better modeled usingrealistic signal-to-noise ratios and noise spectra returned fromSon-O-Mermaid and MERMAID missions. This analysis, particularly whenimplemented in the wavelet domain, is proving

  2. Seismic signal of avalanches

    NASA Astrophysics Data System (ADS)

    Pesaresi, Damiano; Ravanat, Xavier; Thibert, Emmanuel

    2010-05-01

    The characterization of avalanches with seismic signals is an important task. For risk mitigation, estimating remotely avalanche activity by means of seismic signals is a good alternative to direct observations that are often limited by visual conditions and observer's availability. In seismology, the main challenge is to discriminate avalanche signals within the natural earth seismic activity and background noise. Some anthropogenic low frequency (infra-sound) sources like helicopters also generate seismic signals. In order to characterize an avalanche seismic signal, a 3-axis broad band seismometer (Guralp 3T) has been set-up on a real scale avalanche test site in Lautaret (France). The sensor is located in proximity of 2 avalanche paths where avalanches can be artificially released. Preliminary results of seismic records are presented, correlated with avalanche physical parameters (volume released, velocity, energy).

  3. A Two-Radius Circular Array Method: Extracting Independent Information on Phase Velocities of Love Waves From Microtremor Records From a Simple Seismic Array

    NASA Astrophysics Data System (ADS)

    Tada, T.; Cho, I.; Shinozaki, Y.

    2005-12-01

    We have invented a Two-Radius (TR) circular array method of microtremor exploration, an algorithm that enables to estimate phase velocities of Love waves by analyzing horizontal-component records of microtremors that are obtained with an array of seismic sensors placed around circumferences of two different radii. The data recording may be done either simultaneously around the two circles or in two separate sessions with sensors distributed around each circle. Both Rayleigh and Love waves are present in the horizontal components of microtremors, but in the data processing of our TR method, all information on the Rayleigh waves ends up cancelled out, and information on the Love waves alone are left to be analyzed. Also, unlike the popularly used frequency-wavenumber spectral (F-K) method, our TR method does not resolve individual plane-wave components arriving from different directions and analyze their "vector" phase velocities, but instead directly evaluates their "scalar" phase velocities --- phase velocities that contain no information on the arrival direction of waves --- through a mathematical procedure which involves azimuthal averaging. The latter feature leads us to expect that, with our TR method, it is possible to conduct phase velocity analysis with smaller numbers of sensors, with higher stability, and up to longer-wavelength ranges than with the F-K method. With a view to investigating the capabilities and limitations of our TR method in practical implementation to real data, we have deployed circular seismic arrays of different sizes at a test site in Japan where the underground structure is well documented through geophysical exploration. Ten seismic sensors were placed equidistantly around two circumferences, five around each circle, with varying combinations of radii ranging from several meters to several tens of meters, and simultaneous records of microtremors around circles of two different radii were analyzed with our TR method to produce

  4. Mapping the North Sea base-Quaternary: using 3D seismic to fill a gap in the geological record

    NASA Astrophysics Data System (ADS)

    Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

    2014-05-01

    The identification and mapping of the base-Quaternary boundary in the central parts of the North Sea is problematic due to the change from an unconformable transition between Pliocene and Pleistocene deltaic deposits in the southern North Sea to a conformable one further north (Sejrup et al 1991; Gatliff et al 1994). The best estimates of the transition use seismic reflection data to identify a 'crenulated reflector' (Buckley 2012), or rely on correlating sparse biostratigraphy (Cameron et al 1987). Recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) allows greater confidence in the correlation to a regional 3D seismic dataset and show that the base-Quaternary can be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The mapped horizon is presented here alongside the difference between this new interpretation and the previously interpreted base-Quaternary (Buckley 2012). The revised base-Quaternary surface reaches a depth of 1248 ms TWT or approximately 1120 m (assuming average velocity of 1800 m/s) showing an elongate basin shape that follows the underlying structure of the Central Graben. The difference between the revised base-Quaternary and the traditional base-Quaternary reaches a maximum of over 600 ms TWT or approximately 540 m in the south-west with over 300 ms TWT or approximately 270 m at the Josephine well (56° 36.11'N, 2° 27.09'E) in the centre of the basin. Mapping this new base-Quaternary allows for the interpretation of the paleo-envionrment during the earliest Quaternary. Seismic attribute analysis indicates a deep water basin with sediment deposition from multiple deltas and redistribution by deep

  5. U-Th dating of broken speleothems from Cacahuamilpa cave, Mexico: Are they recording past seismic events?

    NASA Astrophysics Data System (ADS)

    Méjean, Pauline; Garduño-Monroy, Victor-Hugo; Pinti, Daniele L.; Ghaleb, Bassam; Bouvier, Laura; Gomez-Vasconcelos, Martha G.; Tremblay, Alain

    2015-01-01

    Cacahuamilpa cave is one of the largest karst systems in Central Mexico. The cave contains numerous massive speleothems broken and fallen following oriented directions, damaged during cataclysmic geological events. One fallen and two broken speleothems were sampled in the Cacahuamilpa cave for dating the rupture event using measured U-Th disequilibrium ages. A total of eight small carbonate cores were drilled perpendicular and longitudinal to the rupture surface. Results showed three groups of ages (weighted average): 0.95 ± 0.02 ka, 28.8 ± 0.2 ka and 88.0 ± 0.7 ka. This indicates that the construction of the Cacahuamilpa karst system, for which no absolute ages existed before this study, initiated at least since Late Pleistocene. The first two groups of ages might be related to two distinct episodes of intense seismic activity. Calculated minimum horizontal ground acceleration and frequency values of the seismic events needed to create the rupture of the stalagmites dated at 0.95 ± 0.02 ka and 28.8 ± 0.2 ka range between 1.3 and 2.0 m s-2 and between 13.4 and 20.8 Hz, respectively. These parameters are compatible with earthquakes of magnitude equal or higher than 7 M, with an epicentral distance between 50 and 100 km from the Cacahuamilpa cave. The stalagmite rupture dated at 88.0 ± 0.7 ka might result from the invasion of the cave by one of the older lahars deposits of the nearby volcano Nevado del Toluca, and successively fell by gravity instability.

  6. Preliminary TEX86 temperatures and a lake level record of tropical climate extremes derived from sediment cores and seismic stratigraphy from Lake Turkana, East Africa

    NASA Astrophysics Data System (ADS)

    Morrissey, A. J.; Scholz, C. A.; Russell, J. M.

    2012-12-01

    Lake Turkana is the largest lake in the Eastern Branch of the East African Rift System and records hydrologic conditions of a region spanning nearly 2.5 degrees of latitude (~2.0 - 4.5 degrees N) in the African tropics. New data suggest the Turkana region likely experienced much wetter and cooler climate over several intervals since the latest Pleistocene. Lake level was extremely low twice during the latest Pleistocene, evidenced by depositional hiatuses in high-resolution CHIRP seismic reflection data that correlate with sediments that have low water-content, abundant sand, and low total organic carbon (TOC as low as <0.7%). Lake Turkana, like many lakes in northern tropical Africa, had a wetter climate during the African Humid Period. Intervals of high lake levels (up to ~440 m amsl) are indicated by flat-lying, laterally continuous, low-amplitude reflections that correlate in sediment cores to dark, fine-grained, laminated sediment with high TOC (up to ~6%). Calcium carbonate accumulation during this time period is nearly 0%, and combined with evidence of laminated, unbioturbated sediment suggests a fresh, stratified lake with anoxic bottom waters. During the early mid-Holocene, lake level began to fall to close to present levels (~365 m amsl). Sediments deposited during this time period have low but variable organic carbon content (~0.5 - ~2%) and are much higher in inorganic carbon (from fine-grained calcite precipitation). A moderate lowstand during the late Holocene is indicated by an erosional unconformity seen down to ~40 m below the current lake surface in several seismic profiles. This record of lake level extremes suggests highly variable rainfall patterns, forced by migration of the Intertropical Convergence Zone) across tropical East Africa over the last 20,000 years. More than 50 sediment samples from 3 piston cores represent a continuous record of TEX86 temperature from ~20,000 years ago to modern. The generally low (<0.25) BIT index for the

  7. Notes on a broad-band variant of the NCER seismic data multiplex system for use with field tape recorders

    USGS Publications Warehouse

    Eaton, Jerry P.

    1976-01-01

    Tests of the standard NCER multiplex system recorded and played back on both the Bell and Howell 3700B (about 0.1% tape speed variation) and on the Sony TC-126 cassette recorder (about 1% tape speed variation) showed that subtractive compensation employing a reference frequency multiplexed on the data track was remarkably effective in reducing tape-speed-variation-induced noise 1 and, hence, in increasing the dynamic range of the record/playback system. Further tests suggested that the 0 to 30 Hz bandwidth of the standard system (8 data channels) might be increased substantially, at the 'price' of reducing the number of data channels to 3 or 4, without serious loss of dynamic range if subtractive compensation could be implemented effectively with the broader-band system.

  8. Preliminary results of receiver function analysis of seismic data recorded from a broadband deployment across the Gulf Coast Plain

    NASA Astrophysics Data System (ADS)

    Gurrola, H.; Pratt, K. W.; Pulliam, J.; Dunbar, J. A.

    2011-12-01

    In summer of 2010, 21 broadband seismographs were installed at 16-18 km spacing along a transect running from Johnson City, TX, (on the Edwards Plateau), to Matagorda Island to study the current structure of this rifted passive margin. The large magnetic anomaly that parallels the coast throughout the Gulf region moves on-shore beneath our transect such that we will be able to investigate the source of this anomaly. A second important target that will be imaged in this Balcones fault which is associated with the Ouachita front. This project is funded by a grant from the Norman Hackerman Advanced Research Program (NHARP), a biannual competition among Texas Universities to support research, and makes use of Texas Tech, Baylor, and UT Austin equipment. As a result, the deployment includes a less uniform array of seismic equipment, (10 Trillium compact seismometers and 10 Guralps; including 40Ts, 3Ts and 3ESPs), than projects supported by the IRIS PASSCAL center. Our vault construction was similar to Flexible array vaults, but Gulf Coast provides a more challenging environment for deployment than most encountered in the western US. The shallow water table and loose sediment can become almost fluid when storms deluge the area with rain. In dry periods, mud cracks near the vaults cause the vaults to tilt. As a result, even high quality, shallow seismic vaults can "float" or shift sufficiently to cause one or two components of the seismic stations to drift against their stops in days or weeks. As a result, the only data consistently available from all our stations, are vertical components. Horizontal component data from the summer of 2010 can be hit and miss due to the tilting of the vaults. These issues have been reduced in the summer of 2011 due to the drought. To address the data's shortcomings, we will average the vertical components from our stations and nearby EarthScope TA stations, (up 300 km away), to isolate the cleanest representation of the incoming P

  9. Volcano seismicity in Alaska

    NASA Astrophysics Data System (ADS)

    Buurman, Helena

    I examine the many facets of volcano seismicity in Alaska: from the short-lived eruption seismicity that is limited to only the few weeks during which a volcano is active, to the seismicity that occurs in the months following an eruption, and finally to the long-term volcano seismicity that occurs in the years in which volcanoes are dormant. I use the rich seismic dataset that was recorded during the 2009 eruption of Redoubt Volcano to examine eruptive volcano seismicity. I show that the progression of magma through the conduit system at Redoubt could be readily tracked by the seismicity. Many of my interpretations benefited greatly from the numerous other datasets collected during the eruption. Rarely was there volcanic activity that did not manifest itself in some way seismically, however, resulting in a remarkably complete chronology within the seismic record of the 2009 eruption. I also use the Redoubt seismic dataset to study post-eruptive seismicity. During the year following the eruption there were a number of unexplained bursts of shallow seismicity that did not culminate in eruptive activity despite closely mirroring seismic signals that had preceded explosions less than a year prior. I show that these episodes of shallow seismicity were in fact related to volcanic processes much deeper in the volcanic edifice by demonstrating that earthquakes that were related to magmatic activity during the eruption were also present during the renewed shallow unrest. These results show that magmatic processes can continue for many months after eruptions end, suggesting that volcanoes can stay active for much longer than previously thought. In the final chapter I characterize volcanic earthquakes on a much broader scale by analyzing a decade of continuous seismic data across 46 volcanoes in the Aleutian arc to search for regional-scale trends in volcano seismicity. I find that volcanic earthquakes below 20 km depth are much more common in the central region of the arc

  10. Comparison of the historical record of earthquake hazard with seismic-hazard models for New Zealand and the continental United States

    USGS Publications Warehouse

    Stirling, M.; Petersen, M.

    2006-01-01

    We compare the historical record of earthquake hazard experienced at 78 towns and cities (sites) distributed across New Zealand and the continental United States with the hazard estimated from the national probabilistic seismic-hazard (PSH) models for the two countries. The two PSH models are constructed with similar methodologies and data. Our comparisons show a tendency for the PSH models to slightly exceed the historical hazard in New Zealand and westernmost continental United States interplate regions, but show lower hazard than that of the historical record in the continental United States intraplate region. Factors such as non-Poissonian behavior, parameterization of active fault data in the PSH calculations, and uncertainties in estimation of ground-motion levels from historical felt intensity data for the interplate regions may have led to the higher-than-historical levels of hazard at the interplate sites. In contrast, the less-than-historical hazard for the remaining continental United States (intraplate) sites may be largely due to site conditions not having been considered at the intraplate sites, and uncertainties in correlating ground-motion levels to historical felt intensities. The study also highlights the importance of evaluating PSH models at more than one region, because the conclusions reached on the basis of a solely interplate or intraplate study would be very different.

  11. Notes on some experiments on the application of subtractive compensation to USGS seismic magnetic tape recording and playback systems

    USGS Publications Warehouse

    Eaton, Jerry P.

    1975-01-01

    The purpose of these experiments is to lay the groundwork for the implementation of subtractive compensation of the USGS seismic network tape playbacks utilizing the Develco model 6203 discriminators at a x1 playback speed. Although the Develco discriminators were designed for this application and a matching Develco compensation discriminator was purchased, effective use of this system for subtractive compensation has been blocked by the inadequate (frequency dependent) matching of the phase of the compensation signal to that of the data signal at the point compensation is carried out in the data discriminators. John Van Schaack has ameliorated the phase mismatch problem by an empirical alteration of the compensation discriminator input bandpass filter. We have selected a set (of eight) Develco discriminators and adjusted their compensation signal input levels to minimize spurious signals (noise) originating from tape speed irregularities. The sensitivity of the data discriminators was adjusted so that deviations of +125 Hz and -125 Hz produced output signals of +2.00 volts and -2.00 volts, respectively. The eight data discriminators are driven by a multiplex signal on a single tape track (subcarriers 680, 1020, 1360, 1700, 2040, 2380, 2720, and 3060 Hz). The Develco-supplied compensation discriminator requires an unmodulated 3125 Hz signal on a separate tape track.

  12. Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume IV S-Wave Measurements in Borehole C4993 Seismic Records, Wave-Arrival Identifications and Interpreted S-Wave Velocity Profile.

    SciTech Connect

    Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

    2007-06-06

    In this volume (IV), all S-wave measurements are presented that were performed in Borehole C4993 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. S-wave measurements were performed over the depth range of 370 to 1300 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1200 ft, depth intervals of 20 ft were used. Shear (S) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition, a second average shear wave record was recorded by reversing the polarity of the motion of the T-Rex base plate. In this sense, all the signals recorded in the field were averaged signals. In all cases, the base plate was moving perpendicular to a radial line between the base plate and the borehole which is in and out of the plane of the figure shown in Figure 1.1. The definition of “in-line”, “cross-line”, “forward”, and “reversed” directions in items 2 and 3 of Section 2 was based on the moving direction of the base plate. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4993, and a 3-D geophone from the University of Texas (UT) was embedded near the borehole at about 1.5 ft below the ground surface. The Redpath geophone and the UT geophone were properly aligned so that one of the horizontal components in each geophone was aligned with the direction of horizontal shaking of the T-Rex base plate. This volume is organized into 12 sections as follows. Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vs Profile at Borehole C4993

  13. Seismic moment tensors of acoustic emissions recorded during laboratory rock deformation experiments: sensitivity to attenuation and anisotropy

    NASA Astrophysics Data System (ADS)

    Stierle, Eva; Vavryčuk, Václav; Kwiatek, Grzegorz; Charalampidou, Elli-Maria; Bohnhoff, Marco

    2016-04-01

    Seismic moment tensors can provide information on the size and orientation of fractures producing acoustic emissions (AEs) and on the stress conditions in the sample. The moment tensor inversion of AEs is, however, a demanding procedure requiring carefully calibrated sensors and accurate knowledge of the velocity model. In field observations, the velocity model is usually isotropic and time independent. In laboratory experiments, the velocity is often anisotropic and time dependent and attenuation might be significant due to opening or closure of microcracks in the sample during loading. In this paper, we study the sensitivity of the moment tensor inversion to anisotropy of P-wave velocities and attenuation. We show that retrieved moment tensors critically depend on anisotropy and attenuation and their neglect can lead to misinterpretations of the source mechanisms. The accuracy of the inversion also depends on the fracturing mode of AEs: tensile events are more sensitive to P-wave anisotropy and attenuation than shear events. We show that geometry of faulting in anisotropic rocks should be studied using the source tensors, since the P- and T-axes of the moment tensors are affected by velocity anisotropy and deviate from the true orientation of faulting. The stronger the anisotropy is, the larger the deviations are. Finally, we prove that the moment tensor inversion applied to a large dataset of AEs can be utilized to provide information on the attenuation parameters of the rock sample. The method is capable of measuring anisotropic attenuation in the sample and allows for detection of dilatant cracking according to the stress regime.

  14. Relative sea level variations recorded by coral microatolls over the last two centuries in Martinique and Guadeloupe: implication for seismic hazard

    NASA Astrophysics Data System (ADS)

    Eric, J.; Jennifer, W.; Feuillet, N.; Deschamps, P.; Guy, C.; Paul, T.; Galetzka, J. E.; Jean-Marie, S.; Bruno, H.

    2012-12-01

    The Lesser Antilles arc is a region of high seismic hazard, which results from the convergence of the American and Caribbean plates at 2cm/yr. Several earthquakes of magnitude ≥ 7 have struck the islands in the past. The largest ones (M 8+) occurred four years apart on January 11 1839 and February 8, 1843, offshore Martinique and Guadeloupe respectively. The 1843 event destroyed the town of Pointe-à-Pitre and killed several thousand people. It was probably a megathrust event. To better constrain the seismic hazard induced by this poorly known subduction interface, we have quantified the surface deformations of Lesser Antilles arc recorded by coral skeletons in Martinique and Guadeloupe. Certain coral species form microatolls, whose upwards growth is limited by the yearly lowest tides (Highest Level of Survival- HLS). They act as tide gauges and provide powerful tools to quantify with a precision of few centimeters the sea-level variations induced by tectonic or climatic processes at annual scale over several centuries. We identified several places where microatolls are growing on Martinique, Guadeloupe, Antigua and Barbuda Islands. Several reefs were first surveyed with low altitude helicopter flights. High-resolution aerial photographs were acquired by a drone in some areas, which allowed identifying sites featuring abundant microatolls. Accurate total station mapping of several sites showed that microatolls within the same area recorded the HLS with a precision of about 4±1cm. Several heads were sampled with a hydraulic chain saw along the eastern coast of Martinique and Guadeloupe. Most are Siderastrea Siderea or Diploria strigosa. Using sclerochronology combined with chemical analysis and U/Th dating, we have determined annual growth rates of 5 mm/yr for the former and of ~10mm/year for the latter. During the last two centuries, all microatolls sampled in Martinique recorded a local relative sea level (RSL) rise of ≈ 2-3 mm/yr, interrupted by sudden

  15. Record of Subducting Topography revealed in 3D Seismic Imaging of Pleistocene unconformities, offshore Southern Costa Rica

    NASA Astrophysics Data System (ADS)

    Edwards, J. H.; Kluesner, J. W.; Silver, E. A.

    2015-12-01

    3D seismic reflection data (CRISP) collected across the southern Costa Rica forearc reveals broad, survey-wide erosional events in the upper ~1 km of slope sediments in the mid-slope to outer shelf. The upper 0-280 m of continuous, weakly deformed sediments, designated by IODP Expedition 344 as structural domain I, is bounded by a major erosional event, (CRISP-U1, dated near 1 Ma), suggesting wave-plain erosion from the present shelf break out to 25 km seaward, to a present-day water depth of 900-1300 m. The eastern toe of its surface is characterized by a large drainage system, likely including submarine channels that eroded to depths >1500 m below present-day water depth. CRISP-U1 is variably uplifted by a series of fault propagation folds and cut by an intersecting array of normal faults. Another, major erosional event, (CRISP-M1, approximately 2 Ma) extended from the outer shelf to the mid slope and removed 500-1000 m of material. Overlying CRISP-M1 is up to 1 km of sediments that are more deformed by fault propagation folds, back thrusts, and intersecting arrays of normal faults. Unconformities with smaller areal extent are variably found in these overlying sediments across the mid-slope to outer shelf, at present-day water depths >220 m. Below CRISP-M1, sediments are more densely deformed and also contain major unconformities that extend survey-wide. Both unconformities, CRISP-U1 and CRISP-M1, are encountered in well U1413 and are demarcated by major benthic foraminifera assemblage changes at 149 mbsf and ~504 mbsf (Harris et al., 2013, Proceeding of the IODP, Volume 344).CRISP-M1 is likely correlative to the major sediment facies and benthic foraminifera assemblage change found in U1379 at ~880 mbsf (Vannuchi et al., 2013). The unconformities and intersecting array of normal faults may demarcate the passing of topography on the downgoing Cocos plate, episodically lifting and then subsiding the Costa Rica margin, with amplitudes up to about 1 km.

  16. Seismic attenuation in Florida

    SciTech Connect

    Bellini, J.J.; Bartolini, T.J.; Lord, K.M.; Smith, D.L. . Dept. of Geology)

    1993-03-01

    Seismic signals recorded by the expanded distribution of earthquake seismograph stations throughout Florida and data from a comprehensive review of record archives from stations GAI contribute to an initial seismic attenuation model for the Florida Plateau. Based on calculations of surface particle velocity, a pattern of attenuation exists that appears to deviate from that established for the remainder of the southeastern US. Most values suggest greater seismic attenuation within the Florida Plateau. However, a separate pattern may exist for those signals arising from the Gulf of Mexico. These results have important implications for seismic hazard assessments in Florida and may be indicative of the unique lithospheric identity of the Florida basement as an exotic terrane.

  17. Volcanism and tectonics in action along the Southern Andes: space-time analysis of current deformation recorded by GNSS and seismicity

    NASA Astrophysics Data System (ADS)

    Tassara, Andres; Giorgis, Scott; Yáñez, Vicente; Garcia, Francisco; Baez, Juan Carlos; Lara, Luis

    2016-04-01

    The Southern Andean margin is perhaps the best natural laboratory on Earth to study the relationship between volcanism and active tectonics. Convergence between Nazca and Southamerican plates along the Southern Andes is relatively rapid (66 mm/yr) and slightly oblique (15-20°) with respect to the continental margin. The trench-normal component of convergence is mainly released along the megathrust fault by great subduction earthquakes. At the time scale of millions of years, the trench-parallel component has been mostly released by dextral strike-slip along the Liquiñe-Ofqui Fault Zone (LOFZ), a long-lived (Eocene-Recent) crustal-scale structure more than 1000 km long which is intimately related to the Southern Volcanic Zone (SVZ) of the Andes. Volcanic systems of the SVZ are clustered near intersections of the LOFZ with oblique and inherited basement structures. In contrast with this clear relationship between crustal tectonics and volcanism at long time-scales, little is still known (here and elsewhere) at the time scale of earthquakes and eruptions about the mechanisms by which they actually interact to create the observed long-term relationship. Into this framework, we are taking advantage of the largely unpublished and very unique geodetic and seismic database that is available for us via the project Active Tectonics and Volcanism at the Southern Andes (ACT&VO-SA) in order to gain understanding about the physical link between contemporary tectono-volcanic processes occurred recently along the southern Andean margin and the long-term construction of the LOFZ-SVZ. We will present a characterization of the current surface velocity field along this region deduced from a kinematic analysis of a network of continuous GNSS stations operating since 2007 and relate this with the spatio-temporal evolution of crustal seismicity recorded by seismic networks maintained by Chilean institutions in order to analyze the possible connection between crustal deformation and

  18. Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume I P-Wave Measurements in Borehole C4993 Seismic Records, Wave-Arrival Identifications and Interpreted P-Wave Velocity Profile.

    SciTech Connect

    Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

    2007-07-06

    In this volume (I), all P-wave measurements are presented that were performed in Borehole C4993 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 370 to 1400 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1200 ft, depth intervals of 20 ft were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4993, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4993, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

  19. Deep Downhole Seismic Testing at the Waste Treatment Plant Site, Hanford, WA. Volume II P-Wave Measurements in Borehole C4996 Seismic Records, Wave-Arrival Identifications and Interpreted P-Wave Velocity Profile.

    SciTech Connect

    Stokoe, Kenneth H.; Li, Song Cheng; Cox, Brady R.; Menq, Farn-Yuh

    2007-07-06

    In this volume (II), all P-wave measurements are presented that were performed in Borehole C4996 at the Waste Treatment Plant (WTP) with T-Rex as the seismic source and the Lawrence Berkeley National Laboratory (LBNL) 3-D wireline geophone as the at-depth borehole receiver. P-wave measurements were performed over the depth range of 360 to 1400 ft, typically in 10-ft intervals. However, in some interbeds, 5-ft depth intervals were used, while below about 1180 ft, depth intervals of 20 ft were used. Compression (P) waves were generated by moving the base plate of T-Rex for a given number of cycles at a fixed frequency as discussed in Section 2. This process was repeated so that signal averaging in the time domain was performed using 3 to about 15 averages, with 5 averages typically used. In addition to the LBNL 3-D geophone, called the lower receiver herein, a 3-D geophone from Redpath Geophysics was fixed at a depth of 22 ft in Borehole C4996, and a 3-D geophone from the University of Texas was embedded near the borehole at about 1.5 ft below the ground surface. This volume is organized into 12 sections as follows: Section 1: Introduction, Section 2: Explanation of Terminology, Section 3: Vp Profile at Borehole C4996, Sections 4 to 6: Unfiltered P-wave records of lower vertical receiver, reaction mass, and reference receiver, Sections 7 to 9: Filtered P-wave signals of lower vertical receiver, reaction mass and reference receiver, Section 10: Expanded and filtered P-wave signals of lower vertical receiver, and Sections 11 and 12: Waterfall plots of unfiltered and filtered lower vertical receiver signals.

  20. Dynamic deformations of shallow sediments in the Valley of Mexico, Part I: Three-dimensional strains and rotations recorded on a seismic array

    USGS Publications Warehouse

    Bodin, P.; Gomberg, J.; Singh, S.K.; Santoyo, M.

    1997-01-01

    We study the spatial variation in earthquake ground motions, or equivalently the dynamic displacement gradient field, using a novel analysis procedure borrowed from geodesy. Seismic data recorded in the Valley of Mexico by a microarray of three three-component surface accelerographs and two three-component accelerographs at depths of 30 m and 102 m constrain our estimates of the dynamic displacement gradient field (from which strains and rotations derive) for four moderate earthquakes at distances of 250 to 300 km. Our study focuses on the effects of low-velocity surface materials on the deformation. At the surface, the gradients corresponding to deformation across vertical planes dominate, and vertical-axis rotations are of similar magnitudes as strains. The greatest peak surface gradient we observed was 206 ??strain for the 14 September 1995 Mw 7.5 earthquake at a distance of ???300 km. However, much larger gradients occur across horizontal planes (???u/???z, where u is a horizontal displacement and z is depth) at some depth between 0 and 30 m. These values are about a factor 10 greater than the corresponding gradient components at the surface, ???u/???z for the 14 September earthquake equaled or exceeded 665 ??strain at depth. The dynamic deformations experienced in Mexico City undoubtedly have occurred before and will occur again in other densely populated areas. However, in many other regions, the sediment response will not remain linear and elastic, resulting instead in liquefaction and ground failure.

  1. Structure and paleoearthquake records of active submarine faults, Cook Strait, New Zealand: Implications for fault interactions, stress loading, and seismic hazard

    NASA Astrophysics Data System (ADS)

    Pondard, Nicolas; Barnes, Philip M.

    2010-12-01

    A new interpretation of active faulting in central Cook Strait, New Zealand, reveals tectonic structures associated with the spatial transition from subduction to continental transform faulting. Marine seismic reflection profiles and multibeam bathymetric data indicate that there are no throughgoing crustal faults connecting the North Island Dextral Fault Belt and the Marlborough Fault System in South Island. The major faults terminate offshore, associated with 5-20 km wide step-overs and a change in regional fault strike. This structure implies that propagation of strike-slip earthquake ruptures across the strait is not probable. Faulted sedimentary sequences in the Wairau Basin (Marlborough shelf), correlated to glacioeustatic sea level cycles, provide a stratigraphic framework for fault analysis. A high-resolution study of the postglacial (<20 ka) vertical displacement history of the Cloudy and Vernon faults reveals up to six and five paleoearthquakes since 18 ka, respectively. These long-timescale records indicate variable recurrence intervals and possibly variable stress drop, thus conforming to the variable slip model of earthquake behavior. Integration of these data with other submarine and terrestrial paleoearthquake records indicates the presence of clustered earthquake sequences involving multiple faults. Different sequences do not always involve the same faults. It appears that earthquake clustering is driven by fault interactions that lead to specific loading conditions favoring the triggering of earthquakes on major faults in relatively short time intervals. Present-day regional Coulomb stress distribution has been calculated in two scenarios considered to represent minimum and maximum loading conditions. The models, incorporating secular tectonic loading and stress changes associated with major crustal earthquakes, indicate high stress loading in a large part of central Cook Strait. These conditions may favor the triggering of future damaging

  2. Seismic source study of the Racha-Dzhava (Georgia) earthquake from aftershocks and broad-band teleseismic body-wave records: An example of active nappe tectonics

    USGS Publications Warehouse

    Fuenzalida, H.; Rivera, L.; Haessler, H.; Legrand, D.; Philip, H.; Dorbath, L.; McCormack, D.; Arefiev, S.; Langer, C.; Cisternas, A.

    1997-01-01

    The Racha-Dzhava earthquake (Ms = 7.0) that occurred on 1991 April 29 at 09:12:48.1 GMT in the southern border of the Great Caucasus is the biggest event ever recorded in the region, stronger than the Spitak earthquake (Ms = 6.9) of 1988. A field expedition to the epicentral area was organised and a temporary seismic network of 37 stations was deployed to record the aftershock activity. A very precise image of the aftershock distribution is obtained, showing an elongated cloud oriented N105??, with one branch trending N310?? in the western part. The southernmost part extends over 80 km, with the depth ranging from 0 to 15 km, and dips north. The northern branch, which is about 30 km long, shows activity that ranges in depth from 5 to 15 km. The complex thrust dips northwards. A stress-tensor inversion from P-wave first-motion polarities shows a state of triaxial compression, with the major principal axis oriented roughly N-S, the minor principal axis being vertical. Body-waveform inversion of teleseismic seismograms was performed for the main shock, which can be divided into four subevents with a total rupture-time duration of 22 s. The most important part of the seismic moment was released by a gentle northerly dipping thrust. The model is consistent with the compressive tectonics of the region and is in agreement with the aftershock distribution and the stress tensor deduced from the aftershocks. The focal mechanisms of the three largest aftershocks were also inverted from body-wave records. The April 29th (Ms = 6.1) and May 5th (Ms = 5.4) aftershocks have thrust mechanisms on roughly E-W-oriented planes, similar to the main shock. Surprisingly, the June 15th (Ms = 6.2) aftershock shows a thrust fault striking N-S. This mechanism is explained by the structural control of the rupture along the east-dipping geometry of the Dzirula Massif close to the Borzhomi-Kazbeg strike-slip fault. In fact, the orientation and shape of the stress tensor produce a thrust on a N

  3. Geometry of basement faults around the Soultz geothermal wells from reflected and converted seismic waves recorded during the 2007 multisource VSP survey

    NASA Astrophysics Data System (ADS)

    Lubrano Lavadera, P.; Marthelot, J.; Zillmer, M.; Cornet, F. H.; Genter, A.

    2012-12-01

    reflected on this fault and recorded in the two wells provides traveltimes that fit the high apparent velocity downgoing waves for the shots located in positions allowing reflections. Depending on the incidence angles of the reflected waves at the geophones, these waves are observed in a complementary way on vertical or horizontal geophones. The geometry of the VSP survey allows illuminating vertically and horizontally the GPK3 fault in the depth range 3 to 4.7 km and in a 1000m lateral interval respectively. In contrast, the 2D surface seismic lines shot around the wells show no reliable reflections within the basement. In addition to the major fault, the Soultz VSP data include several evidences of basement faults where reflected waves and converted waves coincide at the well. VSP is one of the few geophysical techniques able to image fault zones within a deep seated granite.

  4. Volcanic tremor at Volcán de Colima, México recorded during May 2002 and its interactions with the seismic signals produced by low-energy explosive activity and rockfalls

    NASA Astrophysics Data System (ADS)

    Zobin, Vyacheslav M.; Reyes, Gabriel A.; Bretón, Mauricio

    2016-05-01

    The May 2002 eruption episode at Volcán de Colima, México represented the transition period between two stages of effusive activity which were characterized by the formation of lava flows. The short-period seismic signals, recorded during May 2002 at a distance of 1.6 km from the crater, were represented by volcanic tremor and the signals produced by low-energy explosions and rockfalls. Two types of volcanic tremor were recognized: harmonic with two fundamental spectral frequencies of 1.2-1.4 Hz and 1.6-1.7 Hz and non-harmonic. The existence of two fundamental frequencies of volcanic tremor may indicate a two-vent magmatic conduit. No clear relationship between the variations in the spectral content of tremor and occurrence of explosions was observed. The waveforms of the signals, produced by low-energy explosions and rockfalls and recorded on the background of volcanic tremor, were strongly modulated by the low-frequency harmonic tremor signals, forming, in this manner, pseudo-long period events. Fourier analysis of the seismic signals associated with low-energy explosions and rockfalls but recorded on the background of regular seismic noise indicated their high-frequency sources characterized by dominant frequencies within 2-3 Hz and 3-4.5 Hz, respectively.

  5. 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.

  6. Earthquake-induced soft-sediment deformations and seismically amplified erosion rates recorded in varved sediments of Köyceğiz Lake (SW Turkey)

    NASA Astrophysics Data System (ADS)

    Avşar, Ulaş; Jónsson, Sigurjón; Avşar, Özgür; Schmidt, Sabine

    2016-06-01

    Earthquake-triggered landslides amplify erosion rates in catchments, i.e., catchment response (CR) to seismic shocks. In addition to historical eyewitness accounts of muddy rivers implying CRs after large earthquakes, several studies have quantitatively reported increased sediment concentrations in rivers after earthquakes. However, only a few paleolimnological studies could detect CRs within lacustrine sedimentary sequences as siliciclastic-enriched intercalations within background sedimentation. Since siliciclastic-enriched intercalations can easily be of nonseismic origin, their temporal correlation with nearby earthquakes is crucial to assign a seismic triggering mechanism. In most cases, either uncertainties in dating methods or the lack of recent seismic activity has prevented reliable temporal correlations, making the seismic origin of observed sedimentary events questionable. Here we attempt to remove this question mark by presenting sedimentary traces of CRs in the 370-year-long varved sequence of Köyceğiz Lake (SW Turkey) that we compare with estimated peak ground acceleration (PGA) values of several nearby earthquakes. We find that earthquakes exceeding estimated PGA values of ~20 cm/s2 can induce soft-sediment deformations, while CRs seem only to be triggered by PGA levels higher than 70 cm/s2. In Köyceğiz Lake, CRs produce Cr- and Ni-enriched sedimentation due to the seismically mobilized soils derived from ultramafic rocks in the catchment. Given the varve chronology, the residence time of the seismically mobilized material in the catchment is determined to be 5 to 10 years.

  7. 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.

  8. Seismic monitoring of geomorphic processes

    NASA Astrophysics Data System (ADS)

    Burtin, A.; Hovius, N.; Turowski, J. M.

    2014-12-01

    In seismology, the signal is usually analysed for earthquake data, but these represent less than 1% of continuous recording. The remaining data are considered as seismic noise and were for a long time ignored. Over the past decades, the analysis of seismic noise has constantly increased in popularity, and this has led to develop new approaches and applications in geophysics. The study of continuous seismic records is now open to other disciplines, like geomorphology. The motion of mass at the Earth's surface generates seismic waves that are recorded by nearby seismometers and can be used to monitor its transfer through the landscape. Surface processes vary in nature, mechanism, magnitude and space and time, and this variability can be observed in the seismic signals. This contribution aims to give an overview of the development and current opportunities for the seismic monitoring of geomorphic processes. We first describe the common principles of seismic signal monitoring and introduce time-frequency analysis for the purpose of identification and differentiation of surface processes. Second, we present techniques to detect, locate and quantify geomorphic events. Third, we review the diverse layout of seismic arrays and highlight their advantages and limitations for specific processes, like slope or channel activity. Finally, we illustrate all these characteristics with the analysis of seismic data acquired in a small debris-flow catchment where geomorphic events show interactions and feedbacks. Further developments must aim to fully understand the richness of the continuous seismic signals, to better quantify the geomorphic activity and improve the performance of warning systems. Seismic monitoring may ultimately allow the continuous survey of erosion and transfer of sediments in the landscape on the scales of external forcing.

  9. Seismic Catalogue and Seismic Network in Haiti

    NASA Astrophysics Data System (ADS)

    Belizaire, D.; Benito, B.; Carreño, E.; Meneses, C.; Huerfano, V.; Polanco, E.; McCormack, D.

    2013-05-01

    The destructive earthquake occurred on January 10, 2010 in Haiti, highlighted the lack of preparedness of the country to address seismic phenomena. At the moment of the earthquake, there was no seismic network operating in the country, and only a partial control of the past seismicity was possible, due to the absence of a national catalogue. After the 2010 earthquake, some advances began towards the installation of a national network and the elaboration of a seismic catalogue providing the necessary input for seismic Hazard Studies. This paper presents the state of the works carried out covering both aspects. First, a seismic catalogue has been built, compiling data of historical and instrumental events occurred in the Hispaniola Island and surroundings, in the frame of the SISMO-HAITI project, supported by the Technical University of Madrid (UPM) and Developed in cooperation with the Observatoire National de l'Environnement et de la Vulnérabilité of Haiti (ONEV). Data from different agencies all over the world were gathered, being relevant the role of the Dominican Republic and Puerto Rico seismological services which provides local data of their national networks. Almost 30000 events recorded in the area from 1551 till 2011 were compiled in a first catalogue, among them 7700 events with Mw ranges between 4.0 and 8.3. Since different magnitude scale were given by the different agencies (Ms, mb, MD, ML), this first catalogue was affected by important heterogeneity in the size parameter. Then it was homogenized to moment magnitude Mw using the empirical equations developed by Bonzoni et al (2011) for the eastern Caribbean. At present, this is the most exhaustive catalogue of the country, although it is difficult to assess its degree of completeness. Regarding the seismic network, 3 stations were installed just after the 2010 earthquake by the Canadian Government. The data were sent by telemetry thought the Canadian System CARINA. In 2012, the Spanish IGN together

  10. Seismic offset balancing

    SciTech Connect

    Ross, C.P.; Beale, P.L.

    1994-01-01

    The ability to successfully predict lithology and fluid content from reflection seismic records using AVO techniques is contingent upon accurate pre-analysis conditioning of the seismic data. However, all too often, residual amplitude effects remain after the many offset-dependent processing steps are completed. Residual amplitude effects often represent a significant error when compared to the amplitude variation with offset (AVO) response that the authors are attempting to quantify. They propose a model-based, offset-dependent amplitude balancing method that attempts to correct for these residuals and other errors due to sub-optimal processing. Seismic offset balancing attempts to quantify the relationship between the offset response of back-ground seismic reflections and corresponding theoretical predictions for average lithologic interfaces thought to cause these background reflections. It is assumed that any deviation from the theoretical response is a result of residual processing phenomenon and/or suboptimal processing, and a simple offset-dependent scaling function is designed to correct for these differences. This function can then be applied to seismic data over both prospective and nonprospective zones within an area where the theoretical values are appropriate and the seismic characteristics are consistent. A conservative application of the above procedure results in an AVO response over both gas sands and wet sands that is much closer to theoretically expected values. A case history from the Gulf of Mexico Flexure Trend is presented as an example to demonstrate the offset balancing technique.

  11. Seismic Ecology

    NASA Astrophysics Data System (ADS)

    Seleznev, V. S.; Soloviev, V. M.; Emanov, A. F.

    The paper is devoted to researches of influence of seismic actions for industrial and civil buildings and people. The seismic actions bring influence directly on the people (vibration actions, force shocks at earthquakes) or indirectly through various build- ings and the constructions and can be strong (be felt by people) and weak (be fixed by sensing devices). The great number of work is devoted to influence of violent seismic actions (first of all of earthquakes) on people and various constructions. This work is devoted to study weak, but long seismic actions on various buildings and people. There is a need to take into account seismic oscillations, acting on the territory, at construction of various buildings on urbanized territories. Essential influence, except for violent earthquakes, man-caused seismic actions: the explosions, seismic noise, emitted by plant facilities and moving transport, radiation from high-rise buildings and constructions under action of a wind, etc. can exert. Materials on increase of man- caused seismicity in a number of regions in Russia, which earlier were not seismic, are presented in the paper. Along with maps of seismic microzoning maps to be built indicating a variation of amplitude spectra of seismic noise within day, months, years. The presence of an information about amplitudes and frequencies of oscillations from possible earthquakes and man-caused oscillations in concrete regions allows carry- ing out soundly designing and construction of industrial and civil housing projects. The construction of buildings even in not seismically dangerous regions, which have one from resonance frequencies coincident on magnitude to frequency of oscillations, emitted in this place by man-caused objects, can end in failure of these buildings and heaviest consequences for the people. The practical examples of detail of engineering- seismological investigation of large industrial and civil housing projects of Siberia territory (hydro power

  12. Seismic source parameters

    SciTech Connect

    Johnson, L.R.

    1994-06-01

    The use of information contained on seismograms to infer the properties of an explosion source presents an interesting challenge because the seismic waves recorded on the seismograms represent only small indirect, effects of the explosion. The essential physics of the problem includes the process by which these elastic waves are generated by the explosion and also the process involved in propagating the seismic waves from the source region to the sites where the seismic data are collected. Interpretation of the seismic data in terms of source properties requires that the effects of these generation and propagation processes be taken into account. The propagation process involves linear mechanics and a variety of standard seismological methods have been developed for handling this part of the problem. The generation process presents a more difficult problem, as it involves non-linear mechanics, but semi-empirical methods have been developed for handling this part of the problem which appear to yield reasonable results. These basic properties of the seismic method are illustrated with some of the results from the NPE.

  13. Landslide seismic magnitude

    NASA Astrophysics Data System (ADS)

    Lin, C. H.; Jan, J. C.; Pu, H. C.; Tu, Y.; Chen, C. C.; Wu, Y. M.

    2015-11-01

    Landslides have become one of the most deadly natural disasters on earth, not only due to a significant increase in extreme climate change caused by global warming, but also rapid economic development in topographic relief areas. How to detect landslides using a real-time system has become an important question for reducing possible landslide impacts on human society. However, traditional detection of landslides, either through direct surveys in the field or remote sensing images obtained via aircraft or satellites, is highly time consuming. Here we analyze very long period seismic signals (20-50 s) generated by large landslides such as Typhoon Morakot, which passed though Taiwan in August 2009. In addition to successfully locating 109 large landslides, we define landslide seismic magnitude based on an empirical formula: Lm = log ⁡ (A) + 0.55 log ⁡ (Δ) + 2.44, where A is the maximum displacement (μm) recorded at one seismic station and Δ is its distance (km) from the landslide. We conclude that both the location and seismic magnitude of large landslides can be rapidly estimated from broadband seismic networks for both academic and applied purposes, similar to earthquake monitoring. We suggest a real-time algorithm be set up for routine monitoring of landslides in places where they pose a frequent threat.

  14. Imaging geothermal systems associated with oceanic ridge: first analysis of records from a dense seismic network deployed within and around the Reykjanes high-temperature area, SW-Iceland

    NASA Astrophysics Data System (ADS)

    Jousset, P. G.; Ágústsson, K.; Verdel, A.; Blanck, H.; Stefánsson, S. A.; Erbas, K.; Deon, F.; Erlendsson, Ö.; Guðnason, E. Á.; Specht, S.; Hersir, G. P.; Halldórsdóttir, S.; Wemstraa, K.; Franke, S.; Bruhn, D.; Flovenz, O. G.; Tryggvason, H.; Friðleifsson, G. Ó.

    2014-12-01

    Manifestations of supercritical water in magmatic environments have so far only been accessible from analogue outcrops of fossil systems and by simulating pressure/temperature conditions in the laboratory. In order to assess the unknown properties of such reservoirs, scientific drilling is used when Earth surface sampled rocks cannot sufficiently explain past geological processes and when geophysical imaging does not sufficiently explain observed phenomena. However, our understanding of structural and dynamic characteristics of geothermal systems can be improved through application of advanced and/or innovative exploration technologies. Unlike resistivity imaging, active and passive seismic techniques have rarely been used in volcanic geothermal areas, because processing techniques were not adapted to geothermal conditions. Recent advances in volcano-seismology have introduced new processing techniques for assessing subsurface structures and controls on fluid flow in geothermal systems. We present here preliminary analyses of seismic records around a geothermal reservoir located both on-land and offshore along the Reykjanes Ridge, SW-Iceland. We deployed on-land stations (20 broad-band and 10 short-period seismometers) and 24 Ocean Bottom Seismometers which are recording since April 2014. Together with existing permanent stations, the complete network comprises 66 stations. The network was designed so that several processing techniques can be used with the data set and address scientific questions concerning geothermal systems and the oceanic ridge. We present the network deployment, our approach and preliminary results from the first months.

  15. Structure of the North Anatolian Fault Zone from the Auto-Correlation of Ambient Seismic Noise Recorded at a Dense Seismometer Array

    NASA Astrophysics Data System (ADS)

    Taylor, D. G.; Rost, S.; Houseman, G.

    2015-12-01

    In recent years the technique of cross-correlating the ambient seismic noise wavefield at two seismometers to reconstruct empirical Green's Functions for the determination of Earth structure has been a powerful tool to study the Earth's interior without earthquake or man-made sources. However, far less attention has been paid to using auto-correlations of seismic noise to reveal body wave reflections from interfaces in the subsurface. In principle, the Green's functions thus derived should be comparable to the Earth's impulse response to a co-located source and receiver. We use data from a dense seismic array (Dense Array for Northern Anatolia - DANA) deployed across the northern branch of the North Anatolian Fault Zone (NAFZ) in the region of the 1999 magnitude 7.6 Izmit earthquake in western Turkey. The NAFZ is a major strike-slip system that extends ~1200 km across northern Turkey and continues to pose a high level of seismic hazard, in particular to the mega-city of Istanbul. We construct reflection images for the entire crust and upper mantle over the ~35 km by 70 km footprint of the 70-station DANA array. Using auto-correlations of vertical and horizontal components of ground motion, both P- and S-wave velocity information can be retrieved from the wavefield to constrain crustal structure further to established methods. We show that clear P-wave reflections from the crust-mantle boundary (Moho) can be retrieved using the autocorrelation technique, indicating topography on the Moho on horizontal scales of less than 10 km. Offsets in crustal structure can be identified that seem to be correlated with the surface expression of the fault zone in the region. The combined analysis of auto-correlations using vertical and horizontal components will lead to further insight into the fault zone structure throughout the crust and upper mantle.

  16. Seismic Data Gathering and Validation

    SciTech Connect

    Coleman, Justin

    2015-02-01

    Three recent earthquakes in the last seven years have exceeded their design basis earthquake values (so it is implied that damage to SSC’s should have occurred). These seismic events were recorded at North Anna (August 2011, detailed information provided in [Virginia Electric and Power Company Memo]), Fukushima Daichii and Daini (March 2011 [TEPCO 1]), and Kaswazaki-Kariwa (2007, [TEPCO 2]). However, seismic walk downs at some of these plants indicate that very little damage occurred to safety class systems and components due to the seismic motion. This report presents seismic data gathered for two of the three events mentioned above and recommends a path for using that data for two purposes. One purpose is to determine what margins exist in current industry standard seismic soil-structure interaction (SSI) tools. The second purpose is the use the data to validated seismic site response tools and SSI tools. The gathered data represents free field soil and in-structure acceleration time histories data. Gathered data also includes elastic and dynamic soil properties and structural drawings. Gathering data and comparing with existing models has potential to identify areas of uncertainty that should be removed from current seismic analysis and SPRA approaches. Removing uncertainty (to the extent possible) from SPRA’s will allow NPP owners to make decisions on where to reduce risk. Once a realistic understanding of seismic response is established for a nuclear power plant (NPP) then decisions on needed protective measures, such as SI, can be made.

  17. Offshore double-planed shallow seismic zone in the NE Japan forearc region revealed by sP depth phases recorded by regional networks

    NASA Astrophysics Data System (ADS)

    Gamage, Shantha S. N.; Umino, Norihito; Hasegawa, Akira; Kirby, Stephen H.

    2009-07-01

    We detected the sP depth phase at small epicentral distances of about 150 km or more in the seismograms of shallow earthquakes in the NE Japan forearc region. The focal depths of 1078 M > 3 earthquakes that occurred from 2000 to 2006 were precisely determined using the time delay of the sP phase from the initial P-wave arrival. The distribution of relocated hypocentres clearly shows the configuration of a double-planed shallow seismic zone beneath the Pacific Ocean. The upper plane has a low dip angle near the Japan Trench, increasing gradually to ~30° at approximately 100 km landward of the Japan Trench. The lower plane is approximately parallel to the upper plane, and appears to be the near-trench counterpart of the lower plane of the double-planed deep seismic zone beneath the land area. The distance between the upper and lower planes is 28-32 km, which is approximately the same as or slightly smaller than that of the double-planed deep seismic zone beneath the land area. Focal mechanism solutions of the relocated earthquakes are determined from P-wave initial motion data. Although P-wave initial motion data for these offshore events are not ideally distributed on the focal sphere, we found that the upper-plane events that occur near the Japan Trench are characterized by normal faulting, whereas lower-plane events are characterized by thrust faulting. This focal mechanism distribution is the opposite to that of the double-planed deep seismic zone beneath the land area. The characteristics of these focal mechanisms for the shallow and deep doubled-planed seismic zones can be explained by a bending-unbending model of the subducting Pacific plate. Some of relocated earthquakes took place in the source area of the 1933 Mw8.4 Sanriku earthquake at depths of 10-23 km. The available focal mechanisms for these events are characterized by normal faulting. Given that the 1933 event was a large normal-fault event that occurred along a fault plane dipping landward, the

  18. Continuous H/V Spectral Ratio Analysis of Ambient Noise Recorded by Stationary Seismic Stations to Improve Microzonation Results Obtained by Mobile Stations

    NASA Astrophysics Data System (ADS)

    Van Noten, K.; Lecocq, T.; Meyer, L.; Molron, J.; Camelbeeck, T.

    2015-12-01

    Estimating the resonance frequency and amplification factor of unconsolidated sediments by H/V spectral ratio (HVSR) analysis of seismic ambient noise has been widely used since Nakamura's proposal in 1989. The fundamental frequency (f0) usually correlates well with the thickness of unconsolidated sediments above the bedrock. To measure f0 properly, Nakamura suggested to perform microzonation surveys at night when the artificial microtremor is small and does not fully disrupt the ambient seismic noise. As nightly fieldwork is not always a reasonable demand, we propose an alternative workflow of Nakamura's technique to improve the quality of HVSR results obtained by ambient noise measurements of mobile stations during the day. This new workflow includes the automated H/V calculation of one year of continuous seismic data of a stationary/permanent station located nearby the sites selected for microzonation. By means of an automated python script, the daily, weekly, monthly and seasonally variations of the fundamental frequency and the H/V amplitude at the site where the stationary station is installed are evaluated. Continuous HVSR analysis of sites with constant bedrock depth shows that the changes in the determined f0 and H/V amplitude are dominantly caused by the human behaviour which is stored in the ambient seismic noise (e.g. later onset of traffic in a weekend, quiet Sundays, differences between daily/nightly activity,…). This continuous analysis allows the characterisation of the deviation of the measured f0 to the true f0 throughout the whole year! Consequently, as mobile stations are affected by the same variation of the ambient noise, a correction factor can be applied on the calculated f0 of individual measurements during the microzonation survey and a proper Vs can be estimated. In this presentation, we apply this workflow to two different case studies; i.e. a rural site with a shallow bedrock depth of 30 m and an urban site (Brussels, capital of

  19. Offshore double-planed shallow seismic zone in the NE Japan forearc region revealed by sP depth phases recorded by regional networks

    USGS Publications Warehouse

    Gamage, S.S.N.; Umino, N.; Hasegawa, A.; Kirby, S.H.

    2009-01-01

    We detected the sP depth phase at small epicentral distances of about 150 km or more in the seismograms of shallow earthquakes in the NE Japan forearc region. The focal depths of 1078 M > 3 earthquakes that occurred from 2000 to 2006 were precisely determined using the time delay of the sP phase from the initial P-wave arrival. The distribution of relocated hypocentres clearly shows the configuration of a double-planed shallow seismic zone beneath the Pacific Ocean. The upper plane has a low dip angle near the Japan Trench, increasing gradually to ???30?? at approximately 100 km landward of the Japan Trench. The lower plane is approximately parallel to the upper plane, and appears to be the near-trench counterpart of the lower plane of the double-planed deep seismic zone beneath the land area. The distance between the upper and lower planes is 28-32 km, which is approximately the same as or slightly smaller than that of the double-planed deep seismic zone beneath the land area. Focal mechanism solutions of the relocated earthquakes are determined from P-wave initial motion data. Although P-wave initial motion data for these offshore events are not ideally distributed on the focal sphere, we found that the upper-plane events that occur near the Japan Trench are characterized by normal faulting, whereas lower-plane events are characterized by thrust faulting. This focal mechanism distribution is the opposite to that of the double-planed deep seismic zone beneath the land area. The characteristics of these focal mechanisms for the shallow and deep doubled-planed seismic zones can be explained by a bending-unbending model of the subducting Pacific plate. Some of relocated earthquakes took place in the source area of the 1933 Mw8.4 Sanriku earthquake at depths of 10-23 km. The available focal mechanisms for these events are characterized by normal faulting. Given that the 1933 event was a large normal-fault event that occurred along a fault plane dipping landward, the

  20. Lunar seismic data analysis

    NASA Technical Reports Server (NTRS)

    Nakamura, Y.; Latham, G. V.; Dorman, H. J.

    1982-01-01

    The scientific data transmitted continuously from all ALSEP (Apollo Lunar Surface Experiment Package) stations on the Moon and recorded on instrumentation tapes at receiving stations distributed around the Earth were processed. The processing produced sets of computer-compatible digital tapes, from which various other data sets convenient for analysis were generated. The seismograms were read, various types of seismic events were classified; the detected events were cataloged.

  1. 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.

  2. Progressive Seismic Failure, Seismic Gap, and Great Seismic Risk across the Densely Populated North China Basin

    NASA Astrophysics Data System (ADS)

    Yin, A.; Yu, X.; Shen, Z.

    2014-12-01

    Although the seismically active North China basin has the most complete written records of pre-instrumentation earthquakes in the world, this information has not been fully utilized for assessing potential earthquake hazards of this densely populated region that hosts ~200 million people. In this study, we use the historical records to document the earthquake migration pattern and the existence of a 180-km seismic gap along the 600-km long right-slip Tangshan-Hejian-Cixian (THC) fault zone that cuts across the North China basin. The newly recognized seismic gap, which is centered at Tianjin with a population of 11 million people and ~120 km from Beijing (22 million people) and Tangshan (7 million people), has not been ruptured in the past 1000 years by M≥6 earthquakes. The seismic migration pattern in the past millennium suggests that the epicenters of major earthquakes have shifted towards this seismic gap along the THC fault, which implies that the 180- km gap could be the site of the next great earthquake with M≈7.6 if it is ruptured by a single event. Alternatively, the seismic gap may be explained by aseismic creeping or seismic strain transfer between active faults.

  3. Long-term deformation of the Lesser Antilles arc recorded by Late Pleistocene carbonate platforms: questioning our present knowledge of the megathrust seismic behavior.

    NASA Astrophysics Data System (ADS)

    Leclerc, F.; Feuillet, N.; Weil Accardo, J.; Cabioch, G.; Bazin, S.; Beauducel, F.; Boudon, G.; Deplus, C.; Deschamps, P.; De Min, L.; Jacques, E.; Jean-Frederic, L.; Le Friant, A.; Mélézan, D.; Meriaux, A. S. B.; Perret, M.; Perron, J. T.; Philibosian, B.; Saurel, J. M. M.

    2015-12-01

    The Lesser Antilles subduction zone is relatively seismically quiet, hasn't produced M8+ earthquake since the 19th century and recent geodetic studies indicate that it is presently weakly coupled. However, the islands of the forearc are being uplifted since at least 330 ka, at rates of several tenths of m/ka, due to subduction processes. In order to understand the long-term deformation of the Caribbean margin in this subduction context, we aimed at characterizing and quantifying the along-dip and along-strike pattern of the deformation. Through carbonate platform morphology and stratigraphy studies and modeling, offshore the volcanic arc islands of Les Saintes and Martinique, we show that these reef platforms are composed of multi-superimposed sea-level highstand deposits separated by subaerial exposure surfaces formed during sea-level low stands. This stratigraphy is typical of drowning carbonate platforms and we estimated the subsidence rate of these platforms to be of few tenths of m/ka. By summarizing the previous studies, we picture the vertical deformation pattern along and across the Lesser Antilles arc for the MIS5 highstand deposit. We discuss the different potential processes capable of driving this deformation, such as crustal faulting, volcanism and subducting ridges that have only local effects on the deformation pattern. Finally, we examine the implications of our results for the megathrust. Long-term deformations in the Lesser Antilles, but also seismic cycle-induced deformations, challenge our understanding of the megathrust seismic behavior and indicate that the state of coupling of the megathrust is most probably transient over time in order to sustain these deformation.

  4. 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

  5. Seismic bearing

    NASA Astrophysics Data System (ADS)

    Power, Dennis

    2009-05-01

    Textron Systems (Textron) has been using geophones for target detection for many years. This sensing capability was utilized for detection and classification purposes only. Recently Textron has been evaluating multiaxis geophones to calculate bearings and track targets more specifically personnel. This capability will not only aid the system in locating personnel in bearing space or cartesian space but also enhance detection and reduce false alarms. Textron has been involved in the testing and evaluation of several sensors at multiple sites. One of the challenges of calculating seismic bearing is an adequate signal to noise ratio. The sensor signal to noise ratio is a function of sensor coupling to the ground, seismic propagation and range to target. The goals of testing at multiple sites are to gain a good understanding of the maximum and minimum ranges for bearing and detection and to exploit that information to tailor sensor system emplacement to achieve desired performance. Test sites include 10A Site Devens, MA, McKenna Airfield Ft. Benning, GA and Yuma Proving Ground Yuma, AZ. Geophone sensors evaluated include a 28 Hz triax spike, a 15 Hz triax spike and a hybrid triax spike consisting of a 10 Hz vertical geophone and two 28 Hz horizontal geophones. The algorithm uses raw seismic data to calculate the bearings. All evaluated sensors have triaxial geophone configuration mounted to a spike housing/fixture. The suite of sensors also compares various types of geophones to evaluate benefits in lower bandwidth. The data products of these tests include raw geophone signals, seismic features, seismic bearings, seismic detection and GPS position truth data. The analyses produce Probability of Detection vs range, bearing accuracy vs range, and seismic feature level vs range. These analysis products are compared across test sites and sensor types.

  6. Ancient seismic record of the Tarascan (Purhepecha) Empire. Preclasic Period (3000 Yr B.P.). Jaracuaro Island, Patzcuaro Lake. Michoacan, Mexico

    NASA Astrophysics Data System (ADS)

    Rodriguez Pascua, Miguel Angel; Garduño-Monroy, Victor Hugo; Perez-Lopez, Raul; Israde-Alcantara, Isabel

    2010-05-01

    The Pátzcuaro lake is located in the Mexican State of Michoacán in the Transmexican Volcanic Belt. The Jarácuaro island is formed by Holocene lake sediments highly deformed by active faults (Morelia-Acambay Fault System, MAFS, more than 200 km long). MAFS is an E-W strike-slip fault with a transtensive component in the Pázcuaro Lake zone. Several paleoseismic studies were carried out in the island. Four trenches were made in the active faults that cross the island and it is possible observe that there are two andesitic blocks (>4 m3) over two different faults with surface rupture. The archaeological evidences (pottery, idols, etc), founded in the soils affected by the fault, implies that the age of the events concern to the Pre - Classic period (3.000 years B.P.).The Tarascan (or Purhépecha) Empire supported this earthquakes and put the blocks close both faults on the hanging wall block. The andesitic blocks are carved and polished and the quarry where this blocks were extracted is 1.5 km long out the lake. This cultural behaviour was profusely used by the Tarascan related to natural disasters but not documented before related to earthquakes. Maybe this is ones of the oldest human seismic manifestation, and is the first time that is connected a fault with a seismic movement.

  7. Induced Seismicity Monitoring System

    NASA Astrophysics Data System (ADS)

    Taylor, S. R.; Jarpe, S.; Harben, P.

    2014-12-01

    There are many seismological aspects associated with monitoring of permanent storage of carbon dioxide (CO2) in geologic formations. Many of these include monitoring underground gas migration through detailed tomographic studies of rock properties, integrity of the cap rock and micro seismicity with time. These types of studies require expensive deployments of surface and borehole sensors in the vicinity of the CO2 injection wells. Another problem that may exist in CO2 sequestration fields is the potential for damaging induced seismicity associated with fluid injection into the geologic reservoir. Seismic hazard monitoring in CO2 sequestration fields requires a seismic network over a spatially larger region possibly having stations in remote settings. Expensive observatory-grade seismic systems are not necessary for seismic hazard deployments or small-scale tomographic studies. Hazard monitoring requires accurate location of induced seismicity to magnitude levels only slightly less than that which can be felt at the surface (e.g. magnitude 1), and the frequencies of interest for tomographic analysis are ~1 Hz and greater. We have developed a seismo/acoustic smart sensor system that can achieve the goals necessary for induced seismicity monitoring in CO2 sequestration fields. The unit is inexpensive, lightweight, easy to deploy, can operate remotely under harsh conditions and features 9 channels of recording (currently 3C 4.5 Hz geophone, MEMS accelerometer and microphone). An on-board processor allows for satellite transmission of parameter data to a processing center. Continuous or event-detected data is kept on two removable flash SD cards of up to 64+ Gbytes each. If available, data can be transmitted via cell phone modem or picked up via site visits. Low-power consumption allows for autonomous operation using only a 10 watt solar panel and a gel-cell battery. The system has been successfully tested for long-term (> 6 months) remote operations over a wide range

  8. Newberry Seismic Deployment Fieldwork Report

    SciTech Connect

    Wang, J; Templeton, D C

    2012-03-21

    This report summarizes the seismic deployment of Lawrence Livermore National Laboratory (LLNL) Geotech GS-13 short-period seismometers at the Newberry Enhanced Geothermal System (EGS) Demonstration site located in Central Oregon. This Department of Energy (DOE) demonstration project is managed by AltaRock Energy Inc. AltaRock Energy had previously deployed Geospace GS-11D geophones at the Newberry EGS Demonstration site, however the quality of the seismic data was somewhat low. The purpose of the LLNL deployment was to install more sensitive sensors which would record higher quality seismic data for use in future seismic studies, such as ambient noise correlation, matched field processing earthquake detection studies, and general EGS microearthquake studies. For the LLNL deployment, seven three-component seismic stations were installed around the proposed AltaRock Energy stimulation well. The LLNL seismic sensors were connected to AltaRock Energy Gueralp CMG-DM24 digitizers, which are powered by AltaRock Energy solar panels and batteries. The deployment took four days in two phases. In phase I, the sites were identified, a cavity approximately 3 feet deep was dug and a flat concrete pad oriented to true North was made for each site. In phase II, we installed three single component GS-13 seismometers at each site, quality controlled the data to ensure that each station was recording data properly, and filled in each cavity with native soil.

  9. seismicity and seismotectonics of Libya

    NASA Astrophysics Data System (ADS)

    Ben Suleman, abdunnur

    2015-04-01

    Libya, located at the central Mediterranean margin of the African shield, underwent many episodes of orogenic activity that shaped its geological setting. The present day deformation of Libya is the result of the Eurasia-Africa continental collision. The tectonic evolution of Libya has yielded a complex crustal structure that is composed of a series of basins and uplifts. This study aims to explain in detail the seismicity and seismotectonics of Libya using new data recorded by the recently established Libyan National Seismograph Network (LNSN) incorporating other available geophysical and geological information. Detailed investigations of the Libyan seismicity indicates that Libya has experienced earthquakes of varying magnitudes The seismic activity of Libya shows dominant trends of Seismicity with most of the seismic activity concentrated along the northern coastal areas. Four major clusters of Seismicity were quit noticeable. Fault plane solution was estimated for 20 earthquakes recorded by the Libyan National Seismograph Network in northwestern and northeastern Libya. Results of fault plane solution suggest that normal faulting was dominant in the westernmost part of Libya; strike slip faulting was dominant in northern-central part of Libya. The northern-eastern part of the country suggests that dip-dip faulting were more prevalent.

  10. Probabilistic Simulation of Territorial Seismic Scenarios

    SciTech Connect

    Baratta, Alessandro; Corbi, Ileana

    2008-07-08

    The paper is focused on a stochastic process for the prevision of seismic scenarios on the territory and developed by means of some basic assumptions in the procedure and by elaborating the fundamental parameters recorded during some ground motions occurred in a seismic area.

  11. Functional performance requirements for seismic network upgrade

    SciTech Connect

    Lee, R.C.

    1991-08-18

    The SRL seismic network, established in 1976, was developed to monitor site and regional seismic activity that may have any potential to impact the safety or reduce containment capability of existing and planned structures and systems at the SRS, report seismic activity that may be relevant to emergency preparedness, including rapid assessments of earthquake location and magnitude, and estimates of potential on-site and off-site damage to facilities and lifelines for mitigation measures. All of these tasks require SRL seismologists to provide rapid analysis of large amounts of seismic data. The current seismic network upgrade, the subject of this Functional Performance Requirements Document, is necessary to improve system reliability and resolution. The upgrade provides equipment for the analysis of the network seismic data and replacement of old out-dated equipment. The digital network upgrade is configured for field station and laboratory digital processing systems. The upgrade consists of the purchase and installation of seismic sensors,, data telemetry digital upgrades, a dedicated Seismic Data Processing (SDP) system (already in procurement stage), and a Seismic Signal Analysis (SSA) system. The field stations and telephone telemetry upgrades include equipment necessary for three remote station upgrades including seismic amplifiers, voltage controlled oscillators, pulse calibrators, weather protection (including lightning protection) systems, seismometers, seismic amplifiers, and miscellaneous other parts. The central receiving and recording station upgrades will include discriminators, helicopter amplifier, omega timing system, strong motion instruments, wide-band velocity sensors, and other miscellaneous equipment.

  12. 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

  13. Seismicity of west Texas

    SciTech Connect

    Dumas, D.B.

    1981-01-01

    A four year seismic study has found the Basin and Range province of west Texas and the adjacent area of Mexico to be more seismically active then than heretofore known. A University of Texas five station seismic array around the Marfa Basin has located or detected approximately 800 local and regional earthquakes with S-P times of less than 30 sec. A crustal model for the Basin and Range is derived from natural and artificial sources and contains four layers having velocities of 3.60, 4.93, 6.11, and 6.60 km/sec, respectively, overlying a mantle of 8.37 km/sec. A moderate level of seismic activity has been detected near Van Horn, in the Marfa Basin, and along the Texas-Mexico border between latitudes 30 and 31/sup 0/N. Five earthquake sequences were recorded, two near the Texas-Mexico border and three in the Marfa Basin. Four of these sequences showed quiescent periods in foreshock activity preceding the main shock. On the eastern side of the Marfa Basin a diffuse linear seismic zone may represent an unmapped fault, striking N 50/sup 0/W that coincides with Muehlberger's proposed eastern boundary of Basin and Range faulting. A new epicenter for the Valentine, Texas earthquake of August 16, 1931 has been relocated instrumentally at the northern end of this diffuse zone. Regional and local teleseismic P-wave arrival time anomalies observed for the nearby Gnome underground nuclear explosion of 1961 are used to determine station corrections and thus to locate the new 1931 epicenter at 3.69/sup 0/N, 104.57/sup 0/W. Several estimates of magnitude (m/sub b/) based on intensity data range from 5.6 to 6.4. Fault-plane and composite fault-plane solutions support Muehlberger's hypothesis that the Basin and Range is undergoing extension in a SW-NE direction.

  14. Quarterly seismic monitoring report 96B

    SciTech Connect

    Reidel, S.P.

    1996-06-12

    This report summarizes the location, magnitude, and other pertinent information on earthquakes recorded on and near the Hanford Site by Westinghouse Seismic Monitoring during the period encompassing January 1, 1996 to March 31, 1996.

  15. 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.

  16. Statistical models for seismic magnitude

    NASA Astrophysics Data System (ADS)

    Christoffersson, Anders

    1980-02-01

    In this paper some statistical models in connection with seismic magnitude are presented. Two main situations are treated. The first deals with the estimation of magnitude for an event, using a fixed network of stations and taking into account the detection and bias properties of the individual stations. The second treats the problem of estimating seismicity, and detection and bias properties of individual stations. The models are applied to analyze the magnitude bias effects for an earthquake aftershock sequence from Japan, as recorded by a hypothetical network of 15 stations. It is found that network magnitudes computed by the conventional averaging technique are considerably biased, and that a maximum likelihood approach using instantaneous noise-level estimates for non-detecting stations gives the most consistent magnitude estimates. Finally, the models are applied to evaluate the detection characteristics and associated seismicity as recorded by three VELA arrays: UBO (Uinta Basin), TFO (Tonto Forest) and WMO (Wichita Mountains).

  17. Seismic Tomography.

    ERIC Educational Resources Information Center

    Anderson, Don L.; Dziewonski, Adam M.

    1984-01-01

    Describes how seismic tomography is used to analyze the waves produced by earthquakes. The information obtained from the procedure can then be used to map the earth's mantle in three dimensions. The resulting maps are then studied to determine such information as the convective flow that propels the crustal plates. (JN)

  18. Advanced Seismic While Drilling System

    SciTech Connect

    Robert Radtke; John Fontenot; David Glowka; Robert Stokes; Jeffery Sutherland; Ron Evans; Jim Musser

    2008-06-30

    . An APS Turbine Alternator powered the SeismicPULSER{trademark} to produce two Hz frequency peak signals repeated every 20 seconds. Since the ION Geophysical, Inc. (ION) seismic survey surface recording system was designed to detect a minimum downhole signal of three Hz, successful performance was confirmed with a 5.3 Hz recording with the pumps running. The two Hz signal generated by the sparker was modulated with the 3.3 Hz signal produced by the mud pumps to create an intense 5.3 Hz peak frequency signal. The low frequency sparker source is ultimately capable of generating selectable peak frequencies of 1 to 40 Hz with high-frequency spectra content to 10 kHz. The lower frequencies and, perhaps, low-frequency sweeps, are needed to achieve sufficient range and resolution for realtime imaging in deep (15,000 ft+), high-temperature (150 C) wells for (a) geosteering, (b) accurate seismic hole depth, (c) accurate pore pressure determinations ahead of the bit, (d) near wellbore diagnostics with a downhole receiver and wired drill pipe, and (e) reservoir model verification. Furthermore, the pressure of the sparker bubble will disintegrate rock resulting in an increased overall rates of penetration. Other applications for the SeismicPULSER{trademark} technology are to deploy a low-frequency source for greater range on a wireline for Reverse Vertical Seismic Profiling (RVSP) and Cross-Well Tomography. Commercialization of the technology is being undertaken by first contacting stakeholders to define the value proposition for rig site services utilizing SeismicPULSER{trademark} technologies. Stakeholders include national oil companies, independent oil companies, independents, service companies, and commercial investors. Service companies will introduce a new Drill Bit SWD service for deep HTHP wells. Collaboration will be encouraged between stakeholders in the form of joint industry projects to develop prototype tools and initial field trials. No barriers have been identified

  19. Investigating the coastal paleo-seismic and paleo-tsunami records using vermetid benches in the Eastern Mediterranean: case of the Palm Islands reserve -Lebanon.

    NASA Astrophysics Data System (ADS)

    Elias, A.

    2014-12-01

    The vermetid benches or reefs are thick bio-constructions of marine shells of the Vermetidae group that thrive at sea-level and are used as proxy for crustal tectonic deformation, sea-level changes, paleoclimate reconstruction or paleo-Tsunami markers in different regions especially around the Mediterranean Sea. The Palm Islands Reserve located 5km offshore northern Lebanon in the Eastern Mediterranean, on the hanging wall of a submarine, active thrust fault - the Rankine-Abdeh fault - hold abundant vermetid bio-constructions that are still relatively well preserved. It is an exceptional site for testing and investigating hypothesis on the use of the vermetid benches. We surveyed the surface and shorelines of the Palm Island, the largest of the Islands. The fossil vermetid bio-constructions are present as uplifted benches on its northern side. Also, many of the large boulders mostly found on the south-western shore of the islands still hold vermetid bio-constructions originally from the intertidal position before the boulders were uplifted and thrown over the surface of the island away from the shoreline by powerful waves. Two continuous vertical sections of these bio-constructions, 7 and 13cm thick were sampled for radiocarbon dating. Of the 21 large boulders we surveyed 10 had their vermetid crusts sampled for 14C dating. Their measured radiocarbon ages are spread over many centuries and do not cluster around any single date that could correspond with that of a tsunami or storm event responsible for their transport. On another hand the radiocarbon ages from the uplifted benches show that the last co-seismic rupture of the underlying and offshore Rankine-Abdeh thrust took place after the 9th century AD and resulted in the tectonic uplift of the Palm Islands shoreline, by around 80cm. Interpretation of the morphology and ages of the vermetid bio-constructions found on the overthrown boulders suggest that another such co-seismic event happened towards the end of the

  20. Lake beds in the Yammouneh basin (Lebanon) record more than 12,000 years of seismic history on the Levant fault

    NASA Astrophysics Data System (ADS)

    Daëron, M.; Klinger, Y.; Tapponnier, P.; Elias, A.; Gasse, F.; Sursock, A.; Brax, M.; Jacques, E.; Nemer, T.

    2003-04-01

    The most active seismogenic structure along the eastern shore of the Mediterranean is the Levant fault, which forms the boundary between the African and Arabian plates. In order to study the seismic history of this fault on a millennial time scale in Lebanon, we excavated a series of trenches in the Yammouneh basin, where the active trace of the fault cuts through late Pleistocene lacustrine sediments. Five trench walls across the fault zone, 4m apart from each other, were logged and mapped in 2002 and compared to an exploratory, 5m-deep trench dug in 2001. The walls expose subtabular lake beds, down to a depth of 10.5m, with 2-3m of white, shell-rich calcareous marls that overlie 6-7m of blue-grey clays, oxydized to red brown at shallow depth, that top 1-1.5m of light blue marls. The first-order sedimentary units in the 2002 trench are nearly identical to the units exposed in 2001, implying that the variations in the stratigraphy are climate-driven. The stratigraphic layers, which include finely laminated subunits, are cut and disturbed by coseismic deformation along two subparallel, 1-3m-wide, vertical fault zones, 5-10m apart. The cumulative, apparent vertical offsets of corresponding layers at the base of the deepest walls reach 1.5m. Mapping and comparing the fault splays and apparent offsets (still in progress) on all the trench walls suggests the occurrence of about 20 distinct seismic events. Radiocarbon dating of the stratigraphic sequence is underway. Preliminary dating results confirm that here, the latest earthquake along the Yammouneh fault occurred before the 14th century AD, and suggest 7 interseismic periods in the 11ky preceding that event (likely the 1202 AD earthquake). This would be consistent with a preliminary, average recurrence time of 1500-1600 years. An ongoing paleoclimatologic study of the stratigraphic log should yield more accurate insight into the late Pleistocene climate of the Middle-East, and better constraints on the ages of event

  1. New seismic study begins in Puerto Rico

    USGS Publications Warehouse

    Tarr, A.C.

    1974-01-01

    A new seismological project is now underway in Puerto Rico to provide information needed for accurate assessment of the island's seismic hazard. The project should also help to increase understanding of the tectonics and geologic evolution of the Caribbean region. The Puerto Rico Seismic Program is being conducted by the Geological Survey with support provided by the Puerto Rico Water Resources Authority, an agency responsible for generation and distribution of electric power throughout the Commonwealth. The Program will include the installation of a network of high quality seismograph stations to monitor seismic activity on and around Puerto Rico. These stations will be distributed across the island to record the seismicity as uniformly as possible. The detection and accurate location of small earthquakes, as well as moderate magnitude shocks, will aid in mapping active seismic zones and in compiling frequency of occurrence statistics which ultimately wil be useful in seismic risk-zoning of hte island. 

  2. Tests of the standard (30 hz) NCER FM multiplex telemetry system, augmented by two timing channels and a compensation reference signal, used to record multiplexed seismic network data on magnetic tape

    USGS Publications Warehouse

    Eaton, Jerry P.

    1976-01-01

    The application of subtractive compensation to USGS seismic magnetic tape recording and playback systems was examined in a recent USGS Open-file report (1). It was found, for the standard (30 Hz) NCER multiplex system, that subtractive compensation utilizing a 4688 Hz reference signal multiplexed onto each data track was more effective than that utilizing a 3125 Hz reference signal recorded separately on a different track. Moreover, it was found that the portion of the spectrum between the uppermost data channel (3060 Hz + or - 125 Hz) and the compensation reference signal (4688 Hz) could be used to record an additional timing signal, with a center frequency of 3700 Hz and a broader playback bandwidth (ca 0 to 100 Hz) than that of the standard data channels. Accordingly, for the tests described in that report, the standard 8-datachannel multiplex system was augmented by one additional timing channel with a center frequency of 3700 Hz. The 3700 Hz discriminator used in those tests was not successfully set up to utilize subtractive compensation; so its output from a tape playback was quite noisy. Subsequently, further tests have been carried out on the application of subtractive compensation to a 4-channel broad-band multiplex system and to the standard multiplex system, both recorded on field tape recorders with relatively poor tape speed control (2), (3). In the course of these experiments, it was discovered that two separate timing channe1s, not just one, can be inserted between the uppermost data channel and the compensation reference signal, Furthermore, it was possible to adjust the discriminators used to playback these timing channels so that they profited significantly from subtractive compensation even though the playback bandwidth was 0 to 100 Hz (for short rise times of square wave timing signals). The advantages of recording two timing signals on each data track include: 1) one standard time signal to be used for critical timing, e.g. IRIG E, can be

  3. Method for interpreting seismic records to yield indications of gas/oil in an earth formation such as a sandstone, limestone, or dolostone

    SciTech Connect

    Brown, R.J.; Runge, R.J.; Thompson, D.D.

    1983-02-22

    The present invention indicates that acoustic characteristics associated with gas/oil-containing strata such as a sandstone, limestone or dolostone, including reflectivity coefficients can be normalized (and favorably compared) with similar characteristics calculated and displayed by means of a machineimplemented data processing method in which well logging and geologic data are fed thereto to calculate such characteristics without the need for shear-wave velocities. In more detail, in accordance with the invention brine-saturated bulk and shear moduli, (i.e., kw* and gw*) of a sandstone, limestone or dolostone can be predicted as a function of, say, brine-saturated p-wave modulus (pw*) alone (Independent of shearwave velocity). In that way, resulting acoustic values including seismic velocities and amplitudes (also, reflectivities) as a function of a saturation operator 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 accuracy in designating gas zones within formations of interest due to use of the complete Benedict-Webb-Rubin non-ideal gas law in pseudo-reduced form, as cited in Journal of Current Petroleum Technology, Vol. 22, pp. 889-895.

  4. Seismic azimuthal anisotropy in the oceanic lithosphere and asthenosphere from broadband surface wave analysis of OBS array records at 60 Ma seafloor

    NASA Astrophysics Data System (ADS)

    Takeo, A.; Kawakatsu, H.; Isse, T.; Nishida, K.; Sugioka, H.; Ito, A.; Shiobara, H.; Suetsugu, D.

    2016-03-01

    We analyzed seismic ambient noise and teleseismic waveforms of nine broadband ocean bottom seismometers deployed at a 60 Ma seafloor in the southeastward of Tahiti island, the South Pacific, by the Tomographic Investigation by seafloor ARray Experiment for the Society hotspot project. We first obtained one-dimensional shear wave velocity model beneath the array from average phase velocities of Rayleigh waves at a broadband period range of 5-200 s. The obtained model shows a large velocity reduction at depths between 40 and 80 km, where the lithosphere-asthenosphere boundary might exist. We then estimated shear wave azimuthal anisotropy at depths of 20-100 km by measuring azimuthal dependence of phase velocities of Rayleigh waves. The obtained model shows peak-to-peak intensity of the azimuthal anisotropy of 2%-4% with the fastest azimuth of NW-SE direction both in the lithosphere and asthenosphere. This result suggests that the ancient flow frozen in the lithosphere is not perpendicular to the strike of the ancient mid-ocean ridge but is roughly parallel to the ancient plate motion at depths of 20-60 km. The fastest azimuths in the current asthenosphere are subparallel to current plate motion at depths of 60-100 km. Additional shear wave splitting analysis revealed possible perturbations of flow in the mantle by the hot spot activities and implied the presence of azimuthal anisotropy in the asthenosphere down to a depth of 190-210 km.

  5. Constraining shallow slip and tsunami excitation in megathrust ruptures using seismic and ocean acoustic waves recorded on ocean-bottom sensor networks

    NASA Astrophysics Data System (ADS)

    Kozdon, Jeremy E.; Dunham, Eric M.

    2014-06-01

    Great earthquakes along subduction-zone plate boundaries, like the 2011 magnitude 9.0 Tohoku-Oki, Japan, event, deform the seafloor to generate massive tsunamis. Tsunami wave heights near shore are greatest when excitation occurs far offshore near the trench, where water depths are greatest and fault slip is shallow. The Tohoku event, featuring over 30 m of slip near the trench, exemplifies this hazard. Unfortunately the rupture process that far offshore is poorly constrained with land-based geodetic and even most seafloor deformation measurements, and seismic inferences of shallow slip are often nonunique. Here we demonstrate, through dynamic rupture simulations of the Tohoku event, that long-period guided waves in the ocean (specifically, leaking oceanic P-wave modes known as PL waves) can resolve the shallow rupture process and tsunami excitation near the trench. With predicted pressure changes of ∼0.1-1 MPa along most of the seafloor landward of the trench, and periods of several seconds, these PL waves should be observable with ocean-bottom pressure sensors and/or seismometers. With cabled sensor networks like those being deployed offshore Japan and in other subduction zones, these waves could be used to rapidly quantify shallow slip and near-trench seafloor uplift and improve local tsunami early warning systems.

  6. Seismic monitoring of torrential and fluvial processes

    NASA Astrophysics Data System (ADS)

    Burtin, Arnaud; Hovius, Niels; Turowski, Jens M.

    2016-04-01

    In seismology, the signal is usually analysed for earthquake data, but earthquakes represent less than 1 % of continuous recording. The remaining data are considered as seismic noise and were for a long time ignored. Over the past decades, the analysis of seismic noise has constantly increased in popularity, and this has led to the development of new approaches and applications in geophysics. The study of continuous seismic records is now open to other disciplines, like geomorphology. The motion of mass at the Earth's surface generates seismic waves that are recorded by nearby seismometers and can be used to monitor mass transfer throughout the landscape. Surface processes vary in nature, mechanism, magnitude, space and time, and this variability can be observed in the seismic signals. This contribution gives an overview of the development and current opportunities for the seismic monitoring of geomorphic processes. We first describe the common principles of seismic signal monitoring and introduce time-frequency analysis for the purpose of identification and differentiation of surface processes. Second, we present techniques to detect, locate and quantify geomorphic events. Third, we review the diverse layout of seismic arrays and highlight their advantages and limitations for specific processes, like slope or channel activity. Finally, we illustrate all these characteristics with the analysis of seismic data acquired in a small debris-flow catchment where geomorphic events show interactions and feedbacks. Further developments must aim to fully understand the richness of the continuous seismic signals, to better quantify the geomorphic activity and to improve the performance of warning systems. Seismic monitoring may ultimately allow the continuous survey of erosion and transfer of sediments in the landscape on the scales of external forcing.

  7. Updated Colombian Seismic Hazard Map

    NASA Astrophysics Data System (ADS)

    Eraso, J.; Arcila, M.; Romero, J.; Dimate, C.; Bermúdez, M. L.; Alvarado, C.

    2013-05-01

    The Colombian seismic hazard map used by the National Building Code (NSR-98) in effect until 2009 was developed in 1996. Since then, the National Seismological Network of Colombia has improved in both coverage and technology providing fifteen years of additional seismic records. These improvements have allowed a better understanding of the regional geology and tectonics which in addition to the seismic activity in Colombia with destructive effects has motivated the interest and the need to develop a new seismic hazard assessment in this country. Taking advantage of new instrumental information sources such as new broad band stations of the National Seismological Network, new historical seismicity data, standardized global databases availability, and in general, of advances in models and techniques, a new Colombian seismic hazard map was developed. A PSHA model was applied. The use of the PSHA model is because it incorporates the effects of all seismic sources that may affect a particular site solving the uncertainties caused by the parameters and assumptions defined in this kind of studies. First, the seismic sources geometry and a complete and homogeneous seismic catalog were defined; the parameters of seismic rate of each one of the seismic sources occurrence were calculated establishing a national seismotectonic model. Several of attenuation-distance relationships were selected depending on the type of seismicity considered. The seismic hazard was estimated using the CRISIS2007 software created by the Engineering Institute of the Universidad Nacional Autónoma de México -UNAM (National Autonomous University of Mexico). A uniformly spaced grid each 0.1° was used to calculate the peak ground acceleration (PGA) and response spectral values at 0.1, 0.2, 0.3, 0.5, 0.75, 1, 1.5, 2, 2.5 and 3.0 seconds with return periods of 75, 225, 475, 975 and 2475 years. For each site, a uniform hazard spectrum and exceedance rate curves were calculated. With the results, it is

  8. Seismic Rotations Observed with Inertial Seismic Sensors

    NASA Astrophysics Data System (ADS)

    Jean, V.

    2006-12-01

    Recent interest of the seismological community has arisen for possible rotation effects of the Earth on signals recorded by inertial seismometers. Wiechert and Schluter (1903) and more recently Pancha et al. (2000), Igel et al. (2005, 2006) show that, in the teleseismic range, rotations may be neglected and account for less than 0.1% of the translation waves generated by earthquakes. On the contrary, we may see effects of rotation on seismic traces recorded in the near field of an earthquake. As instruments will deliver unsaturated signals in this near field, rotation detection will be more and more frequent. We may observe rotation effects as well in the noise signal at long period. - In the near field, the three components integrated signal of the accelerograms (i.e; velocity signal) diverge and this drift is the effect of an nearly invisible little jump in acceleration signal. The second integrated step diverges and the co-seismic displacement could not be estimated. - By studying the long period noise, we have found that the two horizontal components of some of GEOSCOPE stations with STS-1 seismometer from Streckeisen, present the same noise both in amplitude and in phase with a coherency greater than 95%. This similarity could occur at some stations and not at others and during some time periods. Therefore, the noise has a quite stable horizontal polarisation at N045 during these periods. We may argue that these two separate effects comes from ground rotations and the way they are recorded by seismic instruments. For example, GEOSCOPE stations equipped by STS-2 which have a quite different mechanical structure do not exhibit the polarisation effect. Mechanical pendulums as vertical LaCoste sensor and horizontal 'garden-gate' sensor present effects of rotations on the different translation motions of the mass. Therefore, for the long period noise, a quite probable explanation is that a rotation around the vertical axis acts similarly on the two horizontal

  9. Seismic tracking of Hurricane Sandy

    NASA Astrophysics Data System (ADS)

    Chen, X.; Wen, L.

    2013-12-01

    Very weak, narrow band seismic signals excited by Hurricane Sandy are detected in cross-correlations of continuous waveforms recorded by stations in eastern United States, at the end of October 2012. We analyze propagational properties of the signal and track the source locations using travel-time difference residual projection, from 26 October to 1 November 2012. We find that (1) the seismic signals driven by Hurricane Sandy are azimuthal dependent. Signals are correlated only within close azimuths from the source, (2) seismic signals propagate as Rayleigh surface wave with an average velocity of about 3.3 km/s, and (3) the inferred seismic source locations follow the path of Sandy before UTC 2012.10.30 12:00:00(about half a day after its landfall in New Jersey), but then deviate from the hurricane center and stay in the coastal area near New England for another 12 hours after the hurricane dissipated. Our research discovers the properties of seismic source excited by Hurricane Sandy and demonstrates the capability of using seismic data to real-time track a hurricane and estimate its direct impacts and the subsequent disasters after it dissipates.

  10. Long-range seismic recording of the MISTY PICTURE high-explosive test, White Sands Missile Range, New Mexico. Environmental research papers, February 1987-February 1988

    SciTech Connect

    Cipar, J.

    1988-02-04

    The Solid Earth Geophysics Branch of the Air Force Geophysics Laboratory recorded the MISTY PICTURE high-explosive test at nine sites in the Tularosa Basin of southern New Mexico. Each site consisted of a three-component seismometer set and a digital-event recorder. The stations were due south of the explosion between 95 and 127 km. Analysis of P-wave travel times indicates that the crust is 30-32 km thick beneath the Tularosa Basin, a side graben of the Rio Grande Rift. S-wave travel times are consistent with earlier surface-wave results. Polarization analysis indicates complex scattered and converted energy between the P- and S-wave groups.

  11. MSNoise: a Python Package for Monitoring Seismic Velocity Changes using Ambient Seismic Noise

    NASA Astrophysics Data System (ADS)

    Lecocq, T.; Caudron, C.; Brenguier, F.

    2013-12-01

    Earthquakes occur every day all around the world and are recorded by thousands of seismic stations. In between earthquakes, stations are recording "noise". In the last 10 years, the understanding of this noise and its potential usage have been increasing rapidly. The method, called "seismic interferometry", uses the principle that seismic waves travel between two recorders and are multiple-scattered in the medium. By cross-correlating the two records, one gets an information on the medium below/between the stations. The cross-correlation function (CCF) is a proxy to the Green Function of the medium. Recent developments of the technique have shown those CCF can be used to image the earth at depth (3D seismic tomography) or study the medium changes with time. We present MSNoise, a complete software suite to compute relative seismic velocity changes under a seismic network, using ambient seismic noise. The whole is written in Python, from the monitoring of data archives, to the production of high quality figures. All steps have been optimized to only compute the necessary steps and to use 'job'-based processing. We present a validation of the software on a dataset acquired during the UnderVolc[1] project on the Piton de la Fournaise Volcano, La Réunion Island, France, for which precursory relative changes of seismic velocity are visible for three eruptions betwee 2009 and 2011.

  12. DigiSeis—A software component for digitizing seismic signals using the PC sound card

    NASA Astrophysics Data System (ADS)

    Amin Khan, Khalid; Akhter, Gulraiz; Ahmad, Zulfiqar

    2012-06-01

    An innovative software-based approach to develop an inexpensive experimental seismic recorder is presented. This approach requires no hardware as the built-in PC sound card is used for digitization of seismic signals. DigiSeis, an ActiveX component is developed to capture the digitized seismic signals from the sound card and deliver them to applications for processing and display. A seismic recorder application software SeisWave is developed over this component, which provides real-time monitoring and display of seismic events picked by a pair of external geophones. This recorder can be used as an educational aid for conducting seismic experiments. It can also be connected with suitable seismic sensors to record earthquakes. The software application and the ActiveX component are available for download. This component can be used to develop seismic recording applications according to user specific requirements.

  13. Seismic Imager Space Telescope

    NASA Technical Reports Server (NTRS)

    Sidick, Erkin; Coste, Keith; Cunningham, J.; Sievers,Michael W.; Agnes, Gregory S.; Polanco, Otto R.; Green, Joseph J.; Cameron, Bruce A.; Redding, David C.; Avouac, Jean Philippe; Ampuero, Jean Paul; Leprince, Sebastien; Michel, Remi

    2012-01-01

    A concept has been developed for a geostationary seismic imager (GSI), a space telescope in geostationary orbit above the Pacific coast of the Americas that would provide movies of many large earthquakes occurring in the area from Southern Chile to Southern Alaska. The GSI movies would cover a field of view as long as 300 km, at a spatial resolution of 3 to 15 m and a temporal resolution of 1 to 2 Hz, which is sufficient for accurate measurement of surface displacements and photometric changes induced by seismic waves. Computer processing of the movie images would exploit these dynamic changes to accurately measure the rapidly evolving surface waves and surface ruptures as they happen. These measurements would provide key information to advance the understanding of the mechanisms governing earthquake ruptures, and the propagation and arrest of damaging seismic waves. GSI operational strategy is to react to earthquakes detected by ground seismometers, slewing the satellite to point at the epicenters of earthquakes above a certain magnitude. Some of these earthquakes will be foreshocks of larger earthquakes; these will be observed, as the spacecraft would have been pointed in the right direction. This strategy was tested against the historical record for the Pacific coast of the Americas, from 1973 until the present. Based on the seismicity recorded during this time period, a GSI mission with a lifetime of 10 years could have been in position to observe at least 13 (22 on average) earthquakes of magnitude larger than 6, and at least one (2 on average) earthquake of magnitude larger than 7. A GSI would provide data unprecedented in its extent and temporal and spatial resolution. It would provide this data for some of the world's most seismically active regions, and do so better and at a lower cost than could be done with ground-based instrumentation. A GSI would revolutionize the understanding of earthquake dynamics, perhaps leading ultimately to effective warning

  14. The slant-stacklet transform and its application to teleseismic PcP-P data recorded at large aperture seismic array

    NASA Astrophysics Data System (ADS)

    Ventosa, S.; Romanowicz, B. A.

    2015-12-01

    In most high-resolution studies of the Earth's Deep Interior, the limited amount and uneven distribution of high-quality observations of short-period teleseismic body waves are major obstacles. Dense broadband seismic networks help to overcome major challenges of low signal-to-noise ratio (SNR) of the target phases and of signal-to-interference ratio (SIR) of other (often stronger) mantle phases when the slowness difference is large enough. Intuitive delay-and-sum (i.e. slant-stack) approaches are routinely applied to combine data of many spatially close stations to improve data quality. Alternative methods developed in the context of image processing, such as Radon transform-based methods, have proven useful in exploration seismology to facilitate enhancement and separation of signals according to their slowness and time of arrival. In this spirit, we have introduced the slant-stacklet transform to define coherency-guided filters able to exploit signals that would have been otherwise rejected because of low SNR or SIR. As an illustration, this method allows us to dramatically increase the amount of high-quality PcP observations using dense arrays in North America and Japan, sampling Central America, the western Pacific and Alaska/western Canada with unprecedented resolution and accuracy. After mantle corrections, the main signal left in these regions is relatively long wavelength in these regions of fast velocities around the Pacific, except at the western border of the Pacific large-low shear-velocity province (LLSVP) where we observe a rapid reduction of Vp velocity over a distance of about 10˚. This is just one step to further increase lowermost mantle imaging using P waves, much more information from PcP and other complementary signals (e.g. PdP) around the globe are needed to resolve volumetric structure, topography of the core-mantle boundary and D" discontinuity, and the trade-offs between them, in order to improve our understanding of the interaction

  15. Seismic properties and deformation record of the shallow upper mantle beneath SE Iberia: insights from mantle xenoliths in Neogene alkaline basalts

    NASA Astrophysics Data System (ADS)

    Konc, Z.; Garrido, C.; Tommasi, A.; Padrón-Navarta, J.; Hidas, K.; Szabo, C.

    2011-12-01

    The volcanic activity in the SE Iberian Volcanic Province is the surface expression of magmatism in a complex geodynamic setting during the Cenozoic development of a Mediterranean-type back-arc basin in the Alboran realm. The late stage of this geodynamical evolution was characterized by Neogene alkaline basalt volcanism erupted at 2-3 Ma in the Tallante and Los Perez (Murcia) volcanic centers. This volcanism entrained numerous mantle xenoliths that provide a snapshot of the structure and composition of the lithospheric mantle beneath this region. Xenoliths are spinel (± plagioclase ± amphibole) lherzolite, and minor harzburgite and wehrlite showing porphyroclastic to fine- to medium-grained granoblastic textures. Mantle xenoliths display a marked olivine crystal preferred orientation (CPO) that is similar in the two investigated volcanic centers. The dominant olivine CPO is [100]-fiber pattern characterized by a strong alignment of olivine [100] axes near or parallel to the peridotite lineation and a girdle distribution of [010] axes with a maximum normal to the peridotite foliation. This CPO is consistent with dominant activation of the high temperature [100]{0kl} slip systems of olivine and suggests simple shear or combinations of simple shear and pure shear with a transtensional component were the dominant deformation regimes. These olivine CPO contrast with those of Ronda peridotite -sampling the lithospheric mantle of the Alboran domain at 23 Ma- which are consistent with a transpressional deformation regime, indicating a temporal evolution of the deformation regime to transpressive to a transtensive in the Miocene. The seismic anisotropy calculated from xenolith's CPO and modal compositions is characterized by fast propagation of P-waves and polarization of fast S-waves parallel to the lineation. Highest delay times are observed for S-waves propagating within the foliation, but at high angle to the lineation, whereas S-waves propagating along the lineation

  16. Building a Smartphone Seismic Network

    NASA Astrophysics Data System (ADS)

    Kong, Q.; Allen, R. M.

    2013-12-01

    We are exploring to build a new type of seismic network by using the smartphones. The accelerometers in smartphones can be used to record earthquakes, the GPS unit can give an accurate location, and the built-in communication unit makes the communication easier for this network. In the future, these smartphones may work as a supplement network to the current traditional network for scientific research and real-time applications. In order to build this network, we developed an application for android phones and server to record the acceleration in real time. These records can be sent back to a server in real time, and analyzed at the server. We evaluated the performance of the smartphone as a seismic recording instrument by comparing them with high quality accelerometer while located on controlled shake tables for a variety of tests, and also the noise floor test. Based on the daily human activity data recorded by the volunteers and the shake table tests data, we also developed algorithm for the smartphones to detect earthquakes from daily human activities. These all form the basis of setting up a new prototype smartphone seismic network in the near future.

  17. A university-developed seismic source for shallow seismic surveys

    NASA Astrophysics Data System (ADS)

    Yordkayhun, Sawasdee; Na Suwan, Jumras

    2012-07-01

    The main objectives of this study were to (1) design and develop a low cost seismic source for shallow seismic surveys and (2) test the performance of the developed source at a test site. The surface seismic source, referred to here as a university-developed seismic source is based upon the principle of an accelerated weight drop. A 30 kg activated mass is lifted by a mechanical rack and pinion gear and is accelerated by a mounted spring. When the mass is released from 0.5 m above the surface, it hits a 30 kg base plate and energy is transferred to the ground, generating a seismic wave. The developed source is portable, environmentally friendly, easy to operate and maintain, and is a highly repeatable impact source. To compare the developed source with a sledgehammer source, a source test was performed at a test site, a study site for mapping a major fault zone in southern Thailand. The sledgehammer and the developed sources were shot along a 300 m long seismic reflection profile with the same parameters. Data were recorded using 12 channels off-end geometry with source and receiver spacing of 5 m, resulting in CDP stacked sections with 2.5 m between traces. Source performances were evaluated based on analyses of signal penetration, frequency content and repeatability, as well as the comparison of stacked sections. The results show that both surface sources are suitable for seismic studies down to a depth of about 200 m at the site. The hammer data are characterized by relatively higher frequency signals than the developed source data, whereas the developed source generates signals with overall higher signal energy transmission and greater signal penetration. In addition, the repeatability of the developed source is considerably higher than the hammer source.

  18. Transparent layers in seismic reflection records from the central Ionian Sea (Mediterranean)—evidence for repeated catastrophic turbidite sedimentation during the Quaternary

    NASA Astrophysics Data System (ADS)

    Hieke, W.

    2000-09-01

    Echosounding and SCS records from the Ionian and Sirte Abyssal Plains show, below the Holocene Augias megaturbidite, two additional thick transparent layers which by analogy are interpreted as turbidites. Estimated thicknesses are 10 and 35 m (upper and lower) as a minimum (no consideration of presumable variations of acoustic velocities). The resulting sediment volumes are about 26 and about 200 km 3, respectively. Both layers occupy the entire abyssal plain basins similar to the Holocene Augias megaturbidite. A provenance of mobilized sediments from the Gulf of Sirte into the basins is assumed. The ages of the two turbidites have been estimated at 235,000 and 650,000 years, respectively. It is speculated that mobilization was triggered by tsunamis related to volcanic events or earthquakes in the southern Aegean region.

  19. Broadband bearing-time records of three-component seismic array data and their application to the study of local earthquake coda

    NASA Astrophysics Data System (ADS)

    Wagner, Gregory S.; Owens, Thomas J.

    1993-09-01

    High-frequency three-component array d, are used to study the P and S coda produced by* cal earthquakes. The data are displayed as broadba bearing-time records which allow us to examine a compl, time history of the propagation directions and arrival tin of direct and scattered phases crossing the array. This ~ sualization technique is used to examine the wavefield ~ two scale lengths using two sub-arrays~of sensors. Resu suggest that P coda is dominated by P energy propag, ing sub-parallel to the direct P arrival. The S coda pro agates in all directions and appears to be composed p~ dominantly of S and/or surface wave energy. Significant more 0e coda appears on the smaller scale length sub-art relative to the larger scale array suggesting that much, the ~, coda remains coherent for only very short distanc

  20. Seismic-while-drilling data processing with seismic interferometry in the Daqing Oilfield experiment

    NASA Astrophysics Data System (ADS)

    Liu, Hongtao 1Huang, Weichuan 24Li, Yuquan

    2014-03-01

    Seismic interferometry was used to process the data collected with seismic-while-drilling (SWD) experiments at the Daqing Oilfield. The experiments simultaneously recorded the data at the drilling stem and on the ground. After conducting the frequency and the energy property analysis, the data was processed using the correlation and deconvolution method. Seismic data was then obtained from excitation of the drill bit. The result maps show that the deconvolution method can suppress the source effects and enhance the resolution of the profile, and that the vertical stacks enhance the seismic response of the subsurface. The interferometry process after band-filtering can obtain maps with very high resolution. Seismic interferometry by deconvolution shows great advantages based on the results of this experimental data. The method can also be applied to the SWD data and the ambient seismic data to obtain better processing results.

  1. Seismic event interpretation using fuzzy logic and neural networks

    SciTech Connect

    Maurer, W.J.; Dowla, F.U.

    1994-01-01

    In the computer interpretation of seismic data, unknown sources of seismic events must be represented and reasoned about using measurements from the recorded signal. In this report, we develop the use of fuzzy logic to improve our ability to interpret weak seismic events. Processing strategies for the use of fuzzy set theory to represent vagueness and uncertainty, a phenomena common in seismic data analysis, are developed. A fuzzy-assumption based truth-maintenance-inferencing engine is also developed. Preliminary results in interpreting seismic events using the fuzzy neural network knowledge-based system are presented.

  2. Seismicity of southern Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Lavayssiere, A.; Gallacher, R. J.; Keir, D.; Ebinger, C. J.; Drooff, C.; Khalfan, M.; Bull, J. M.

    2015-12-01

    Global seismic networks document frequent and unusually deep earthquakes in East African rift sectors lacking central volcanoes. The deep seismicity means that we can use earthquakes to probe the geometry and kinematics of fault systems throughout the crust, and to understand the distribution of strain between large offset border fault systems and intrabasinal faults. The southern Tanganyika rift zone has the highest seismicity rate within East Africa during the period 1973-present, yet earlier temporary seismometer networks have been too sparse in space and time to relocate earthquakes with location and depth errors of < 5-10 km. We address this issue by recording seismicity of southern Lake Tanganyika since June 2014 using a network at 12 broadband seismic stations. The distribution of earthquakes shows that deformation primarily occurs on large offset border faults beneath the lake. Subsidiary earthquake activity occurs along the subparrallel Rukwa graben, and beneath the NE-SW striking Mweru rift. The distribution of earthquakes suggests the southern end of lake Tanganyika is characterized by a network of intersecting NNW and NE striking faults. The depths of earthquakes are distributed throughout the crust, consistent with the relatively strong lithosphere.

  3. Seismic excitation by space shuttles

    USGS Publications Warehouse

    Kanamori, H.; Mori, J.; Sturtevant, B.; Anderson, D.L.; Heaton, T.

    1992-01-01

    Shock waves generated by the space shuttles Columbia (August 13, 1989), Atlantis (April 11, 1991) and Discovery (September 18, 1991) on their return to Edwards Air Force Base, California, were recorded by TERRAscope (Caltech's broadband seismic network), the Caltech-U.S.G.S Southern California Seismic Network (SCSN), and the University of Southern California (USC) Los Angeles Basin Seismic Network. The spatial pattern of the arrival times exhibits hyperbolic shock fronts from which the path, velocity and altitude of the space shuttle could be determined. The shock wave was acoustically coupled to the ground, converted to a seismic wave, and recorded clearly at the broadband TERRAscope stations. The acoustic coupling occurred very differently depending on the conditions of the Earth's surface surrounding the station. For a seismic station located on hard bedrock, the shock wave (N wave) was clearly recorded with little distortion. Aside from the N wave, very little acoustic coupling of the shock wave energy to the ground occurred at these sites. The observed N wave record was used to estimate the overpressure of the shock wave accurately; a pressure change of 0.5 to 2.2 mbars was obtained. For a seismic station located close to the ocean or soft sedimentary basins, a significant amount of shock wave energy was transferred to the ground through acoustic coupling of the shock wave and the oceanic Rayleigh wave. A distinct topography such as a mountain range was found effective to couple the shock wave energy to the ground. Shock wave energy was also coupled to the ground very effectively through large man made structures such as high rise buildings and offshore oil drilling platforms. For the space shuttle Columbia, in particular, a distinct pulse having a period of about 2 to 3 seconds was observed, 12.5 s before the shock wave, with a broadband seismograph in Pasadena. This pulse was probably excited by the high rise buildings in downtown Los Angeles which were

  4. The Southern Kansas Seismic Network

    NASA Astrophysics Data System (ADS)

    Terra, F. M.

    2015-12-01

    Historically aseismic Harper and Sumner counties in Southern Kansas experienced a dramatic increase in seismicity beginning in early 2014, coincident with the development of new oil production in the Mississippi Lime Play. In order to better understand the potential relationships between seismicity and oil development, the USGS installed a real-time telemetered seismic network in cooperation with the Kansas Geological Survey, the Kansas Corporation Commission, the Kansas Department of Health and Environment, Harper County, and the Oklahoma Geological Survey. The network began operation in March 2014 with an initial deployment of 5 NetQuakes accelerometers and by July 2014 had expanded to include 10 broadband sites. The network currently has 14 stations, all with accelerometers and 12 with broadband seismometers. The network has interstation spacing of 15 - 25 km and typical azimuthal gap of 80 for well-located events. Data are continuously streamed to IRIS at 200 samples per second from most sites. Earthquake locations are augmented with additional stations from the USGS National Network, Oklahoma Geological Survey Seismic Network, Kansas Seismic Monitoring Network and the Enid Oklahoma Network. Since the spring of 2014 over 7500 earthquakes have been identified with data from this network, 1400 of which have been manually timed and cataloged. Focal depths for earthquakes typically range between 2 and 7 km. The catalog is available at earthquake.usgs.gov/earthquakes/search/ under network code 'Ismpkansas'. The network recorded the largest known earthquake in Harper County, Mw 4.3, on October 2, 2014 and in Sumner County, Mw 4.9, on November 12, 2014. Recorded ground motions at the epicenter of the October earthquake were 0.70 g (PGA) and 12 cm/s (PGV). These high ground motion values agree with near-source recordings made by other USGS temporary deployments in the U. S. midcontinent, indicating a significant shaking hazard from such shallow, moderate

  5. Quantifying Similarity in Seismic Polarizations

    NASA Astrophysics Data System (ADS)

    Eaton, D. W. S.; Jones, J. P.; Caffagni, E.

    2015-12-01

    Measuring similarity in seismic attributes can help identify tremor, low S/N signals, and converted or reflected phases, in addition to diagnosing site noise and sensor misalignment in arrays. Polarization analysis is a widely accepted method for studying the orientation and directional characteristics of seismic phases via. computed attributes, but similarity is ordinarily discussed using qualitative comparisons with reference values. Here we introduce a technique for quantitative polarization similarity that uses weighted histograms computed in short, overlapping time windows, drawing on methods adapted from the image processing and computer vision literature. Our method accounts for ambiguity in azimuth and incidence angle and variations in signal-to-noise (S/N) ratio. Using records of the Mw=8.3 Sea of Okhotsk earthquake from CNSN broadband sensors in British Columbia and Yukon Territory, Canada, and vertical borehole array data from a monitoring experiment at Hoadley gas field, central Alberta, Canada, we demonstrate that our method is robust to station spacing. Discrete wavelet analysis extends polarization similarity to the time-frequency domain in a straightforward way. Because histogram distance metrics are bounded by [0 1], clustering allows empirical time-frequency separation of seismic phase arrivals on single-station three-component records. Array processing for automatic seismic phase classification may be possible using subspace clustering of polarization similarity, but efficient algorithms are required to reduce the dimensionality.

  6. Hanford Seismic Report for Fiscal Year 2000

    SciTech Connect

    Hartshorn, D.C.; Reidel, S.; Rohay, A.C.

    2000-02-23

    Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the U.S. Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (EWRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EWRN uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 311 triggers on two parallel detection and recording systems during the first quarter of fiscal year (FY) 2000. Twelve seismic events were located by the Hanford Seismic Network within the reporting region of 46{degree}-47{degree}N latitude and 119{degree}-120{degree}W longitude; 2 were earthquakes in the Columbia River Basalt Group, 3 were earthquakes in the pre-basalt sediments, 9 were earthquakes in the crystalline basement, and 1 was a quarry blast. Two earthquakes appear to be related to a major geologic structure, no earthquakes occurred in known swarm areas, and 9 earthquakes were random occurrences. No earthquakes triggered the Hanford Strong Motion

  7. Technology creates role for small seismic crews

    SciTech Connect

    Moriarty, B.J. . Kiwi American Energy Inc.)

    1993-09-27

    While the oil and gas industry focuses on large, complex 3D seismic surveys around the world, other, more-quiet changes are taking place. A new breed of small, high-tech seismic crew is emerging as the latest generation of seismic equipment becomes available. Light, economical equipment formerly used for shallow engineering purposes now can produce high-quality data at depths required for oil and gas exploration. Improvements in acquisition technology and equipment reduce costs of seismic surveys, providing new and expanded opportunities in exploration. These improvements include powerful, light recording systems; advanced seismic processing methods; portable processing and analysis on powerful notebook computers; and light, environmentally safe seismic sources. The growing ability of small crews and compact equipment to acquire high-quality data provides operators the option of shooting surveys in especially sensitive areas or of shooting tailor-made surveys in areas of high interest. Niche surveys of this type are especially useful in mature producing areas, such as the U.S. The paper describes the challenges, the dynamic ranges that must be handled (recording weak signals in the presence of strong ones), seismic equipment, and exploration opportunities.

  8. Final Data Report: P- and S-Wave Velocity Logging Borings C4993, C4996, and C4997 Part A: Interval Logs

    SciTech Connect

    Steller, Robert; Diehl, John

    2007-02-01

    Insitu borehole P- and S-wave velocity measurements were collected in three borings located within the Waste Treatment Plant (WTP) boundaries at the Hanford Site, southeastern Washington. Geophysical data acquisition was performed between August and October of 2006 by Rob Steller, Charles Carter, Antony Martin and John Diehl of GEOVision. Data analysis was performed by Rob Steller and John Diehl, and reviewed by Antony Martin of GEOVision, and report preparation was performed by John Diehl and reviewed by Rob Steller. The work was performed under subcontract with Battelle, Pacific Northwest Division with Marty Gardner as Battelle’s Technical Representative and Alan Rohay serving as the Technical Administrator for Pacific Northwest National Laboratory (PNNL). This report describes the field measurements, data analysis, and results of this work.

  9. Final Data Report: P- and S-Wave Velocity Logging Borings C4993, C4996, and C4997 Part B: Overall Logs

    SciTech Connect

    Diehl, John; Steller, Robert

    2007-03-20

    Insitu borehole P- and S-wave velocity measurements were collected in three borings located within the Waste Treatment Plant (WTP) boundaries at the Hanford Site, southeastern Washington. Geophysical data acquisition was performed between August and October of 2006 by Rob Steller, Charles Carter, Antony Martin and John Diehl of GEOVision. Data analysis was performed by Rob Steller and John Diehl, and reviewed by Antony Martin of GEOVision, and report preparation was performed by John Diehl and reviewed by Rob Steller. The work was performed under subcontract with Battelle, Pacific Northwest Division with Marty Gardner as Battelle’s Technical Representative and Alan Rohay serving as the Technical Administrator for Pacific Northwest National Laboratory (PNNL). This report describes the field measurements, data analysis, and results of this work.

  10. Meteoroid flux from passive seismic experiment data

    NASA Technical Reports Server (NTRS)

    Duennebier, F.; Dorman, J.; Lammlein, D.; Latham, G.; Nakamura, Y.

    1975-01-01

    The meteoroid flux hitting the moon is recomputed using new information on the decrease of seismic signal amplitude with range. The new data are principally 17 large meteoroid impacts whose locations have been computed from recordings at all four of the operating Passive Seismic Experiment stations. These data suggest a rapid decrease in amplitudes beyond about 2200 km (chord range) which was not suspected earlier. The new estimate predicts the abundance of meteoroids with masses between 500 and 50,000 g. The result is considerably lower than estimates from earth-based observations, and close to our previous estimate from long-period lunar seismic data.

  11. Seismic augmentation of acoustic monitoring of mortar fire

    NASA Astrophysics Data System (ADS)

    Anderson, Thomas S.

    2007-10-01

    The US Army Corps of Engineers Research and Development Center participated in a joint ARL-NATO TG-53 field experiment and data collect at Yuma Proving Ground, AZ in early November 2005. Seismic and acoustic signatures from both muzzle blasts and impacts of small arms fire and artillery were recorded using 7 seismic arrays and 3 acoustic arrays. Arrays comprised of 12 seismic and 12 acoustic sensors each were located from 700 m to 18 km from gun positions. Preliminary analysis of signatures attributed to 60mm, 81mm, 120 mm mortars recorded at a seismic-acoustic array 1.1 km from gun position are presented. Seismic and acoustic array f-k analysis is performed to detect and characterize the source signature. Horizontal seismic data are analyzed to determine efficacy of a seismic discriminant for mortar and artillery sources. Rotation of North and East seismic components to radial and transverse components relative to the source-receiver path provide maximum surface wave amplitude on the transverse component. Angles of rotation agree well with f-k analysis of both seismic and acoustic signals. The spectral energy of the rotated transverse surface wave is observable on the all caliber of mortars at a distance of 1.1 km and is a reliable source discriminant for mortar sources at this distance. In a step towards automation, travel time stencils using local seismic and acoustic velocities are applied to seismic data for analysis and determination of source characteristics.

  12. Seismic sources

    DOEpatents

    Green, M.A.; Cook, N.G.W.; McEvilly, T.V.; Majer, E.L.; Witherspoon, P.A.

    1987-04-20

    Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Longitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements for more than about one minute. 9 figs.

  13. Seismic Monitoring for the United Arab Emirates

    SciTech Connect

    Rodgers, A; Nakanishi, K

    2005-04-11

    There is potential for earthquakes in the United Arab Emirates and in the Zagros mountains to cause structural damage and pose a threat to safety of people. Damaging effects from earthquakes can be mitigated by knowledge of the location and size of earthquakes, effects on construction, and monitoring these effects over time. Although a general idea of seismicity in the UAE may be determined with data from global seismic networks, these global networks do not have the sensitivity to record smaller seismic events and do not have the necessary accuracy to locate the events. A National Seismic Monitoring Observatory is needed for the UAE that consists of a modern seismic network and a multidisciplinary staff that can analyze and interpret the data from the network. A seismic network is essential to locate earthquakes, determine event magnitudes, identify active faults and measure ground motions from earthquakes. Such a network can provide the data necessary for a reliable seismic hazard assessment in the UAE. The National Seismic Monitoring Observatory would ideally be situated at a university that would provide access to the wide range of disciplines needed in operating the network and providing expertise in analysis and interpretation.

  14. Seismic refraction exploration

    SciTech Connect

    Ruehle, W.H.

    1980-12-30

    In seismic exploration, refracted seismic energy is detected by seismic receivers to produce seismograms of subsurface formations. The seismograms are produced by directing seismic energy from an array of sources at an angle to be refracted by the subsurface formations and detected by the receivers. The directivity of the array is obtained by delaying the seismic pulses produced by each source in the source array.

  15. Fluid injection and induced seismicity

    NASA Astrophysics Data System (ADS)

    Kendall, Michael; Verdon, James

    2016-04-01

    The link between fluid injection, or extraction, and induced seismicity has been observed in reservoirs for many decades. In fact spatial mapping of low magnitude events is routinely used to estimate a stimulated reservoir volume. However, the link between subsurface fluid injection and larger felt seismicity is less clear and has attracted recent interest with a dramatic increase in earthquakes associated with the disposal of oilfield waste fluids. In a few cases, hydraulic fracturing has also been linked to induced seismicity. Much can be learned from past case-studies of induced seismicity so that we can better understand the risks posed. Here we examine 12 case examples and consider in particular controls on maximum event size, lateral event distributions, and event depths. Our results suggest that injection volume is a better control on maximum magnitude than past, natural seismicity in a region. This might, however, simply reflect the lack of baseline monitoring and/or long-term seismic records in certain regions. To address this in the UK, the British Geological Survey is leading the deployment of monitoring arrays in prospective shale gas areas in Lancashire and Yorkshire. In most cases, seismicity is generally located in close vicinity to the injection site. However, in some cases, the nearest events are up to 5km from the injection point. This gives an indication of the minimum radius of influence of such fluid injection projects. The most distant events are never more than 20km from the injection point, perhaps implying a maximum radius of influence. Some events are located in the target reservoir, but most occur below the injection depth. In fact, most events lie in the crystalline basement underlying the sedimentary rocks. This suggests that induced seismicity may not pose a leakage risk for fluid migration back to the surface, as it does not impact caprock integrity. A useful application for microseismic data is to try and forecast induced seismicity

  16. Synthesis of artificial spectrum-compatible seismic accelerograms

    NASA Astrophysics Data System (ADS)

    Vrochidou, E.; Alvanitopoulos, P. F.; Andreadis, I.; Elenas, A.; Mallousi, K.

    2014-08-01

    The Hilbert-Huang transform is used to generate artificial seismic signals compatible with the acceleration spectra of natural seismic records. Artificial spectrum-compatible accelerograms are utilized instead of natural earthquake records for the dynamic response analysis of many critical structures such as hospitals, bridges, and power plants. The realistic estimation of the seismic response of structures involves nonlinear dynamic analysis. Moreover, it requires seismic accelerograms representative of the actual ground acceleration time histories expected at the site of interest. Unfortunately, not many actual records of different seismic intensities are available for many regions. In addition, a large number of seismic accelerograms are required to perform a series of nonlinear dynamic analyses for a reliable statistical investigation of the structural behavior under earthquake excitation. These are the main motivations for generating artificial spectrum-compatible seismic accelerograms and could be useful in earthquake engineering for dynamic analysis and design of buildings. According to the proposed method, a single natural earthquake record is deconstructed into amplitude and frequency components using the Hilbert-Huang transform. The proposed method is illustrated by studying 20 natural seismic records with different characteristics such as different frequency content, amplitude, and duration. Experimental results reveal the efficiency of the proposed method in comparison with well-established and industrial methods in the literature.

  17. Historical Seismicity of Central Panama

    NASA Astrophysics Data System (ADS)

    Camacho, E.

    2013-05-01

    Central Panama lies in the Panama microplate, neighboring seismically active regions of Costa Rica and Colombia. This region, crossed by the Panama Canal, concentrates most of the population and economic activity of the Republic of Panama. Instrumental observation of earthquakes in Panama began on 1882 by the Compagnie Universelle du Canal Interocéanique de Panama and continued from 1904 to 1977 by the Panama Canal Company. From October 1997 to March 1998 the USGS deployed a temporary digital seismic network. Since 2003 this region is monitored by a digital seismic network operated by the Panama Canal Authority and I complemented by the broad band stations of the University of Panama seismic network. The seismicity in this region is very diffuse and the few events which are recorded have magnitudes less than 3.0. Historical archives and antique newspapers from Spain, Colombia, Panama and the United Sates have been searched looking for historical earthquake information which could provide a better estimate of the seismicity in this region. We find that Panama City has been shaken by two destructive earthquakes in historical times. One by a local fault (i.e. Pedro Miguel fault) on May 2, 1621 (I=Vlll MM), and a subduction event from the North Panama Deformed Belt (NPDB) on September 7, 1882 (I=Vll MM). To test these findings two earthquakes scenarios were generated, using SELENA, for Panama City Old Quarter. Panama City was rebuilt on January 21, 1673, on a rocky point facing the Pacific Ocean after the sack by pirate Morgan on January 28, 1671. The pattern of damage to calicanto (unreinforced colonial masonry) and wood structures for a crustal local event are higher than those for an event from the NPDB and seem to confirm that the city has not been shaken by a major local event since May 2, 1621 and a subduction event since September 7, 1882

  18. Monitoring gas reservoirs by seismic interferometry

    NASA Astrophysics Data System (ADS)

    Grigoli, Francesco; Cesca, Simone; Sens-Schoenfelder, Christoph; Priolo, Enrico

    2014-05-01

    Ambient seismic noise can be used to image spatial anomalies in the subsurface, without the need of recordings from seismic sources, such as earthquakes or explosions. Furthermore, the temporal variation of ambient seismic noise's can be used to infer temporal changes of the seismic velocities in the investigated medium. Such temporal variations can reflect changes of several physical properties/conditions in the medium. For example, they may be consequence of stress changes, variation of hydrogeological parameters, pore pressure and saturation changes due to fluid injection or extraction. Passive image interferometry allows to continuously monitor small temporal changes of seismic velocities in the subsurface, making it a suitable tool to monitor time-variant systems such as oil and gas reservoirs or volcanic environments. The technique does not require recordings from seismic sources in the classical sense, but is based on the processing of noise records. Moreover, it requires only data from one or two seismic stations, their locations constraining the sampled target area. Here we apply passive image interferometry to monitor a gas storage reservoir in northern Italy. The Collalto field (Northern Italy) is a depleted gas reservoir located at 1500 m depth, now used as a gas storage facility. The reservoir experience a significant temporal variation in the amount of stored gas: the injection phases mainly occur in the summer, while the extraction take place mostly in winter. In order to monitor induced seismicity related to gas storage operations, a seismic network (the Collalto Seismic Network) has been deployed in 2011. The Collalto Seismic Network is composed by 10 broadband stations, deployed within an area of about 20 km x 20 km, and provides high-quality continuous data since January 1st, 2012. In this work we present preliminary results from ambient noise interferometry using a two-months sample of continuous seismic data, i.e. from October 1st, 2012, to the

  19. Seismic Noise Analysis and Reduction through Utilization of Collocated Seismic and Atmospheric Sensors at the GRO Chile Seismic Network

    NASA Astrophysics Data System (ADS)

    Farrell, M. E.; Russo, R. M.

    2013-12-01

    The installation of Earthscope Transportable Array-style geophysical observatories in Chile expands open data seismic recording capabilities in the southern hemisphere by nearly 30%, and has nearly tripled the number of seismic stations providing freely-available data in southern South America. Through the use of collocated seismic and atmospheric sensors at these stations we are able to analyze how local atmospheric conditions generate seismic noise, which can degrade data in seismic frequency bands at stations in the ';roaring forties' (S latitudes). Seismic vaults that are climate-controlled and insulated from the local environment are now employed throughout the world in an attempt to isolate seismometers from as many noise sources as possible. However, this is an expensive solution that is neither practical nor possible for all seismic deployments; and also, the increasing number and scope of temporary seismic deployments has resulted in the collection and archiving of terabytes of seismic data that is affected to some degree by natural seismic noise sources such as wind and atmospheric pressure changes. Changing air pressure can result in a depression and subsequent rebound of Earth's surface - which generates low frequency noise in seismic frequency bands - and even moderate winds can apply enough force to ground-coupled structures or to the surface above the seismometers themselves, resulting in significant noise. The 10 stations of the permanent Geophysical Reporting Observatories (GRO Chile), jointly installed during 2011-12 by IRIS and the Chilean Servicio Sismológico, include instrumentation in addition to the standard three seismic components. These stations, spaced approximately 300 km apart along the length of the country, continuously record a variety of atmospheric data including infrasound, air pressure, wind speed, and wind direction. The collocated seismic and atmospheric sensors at each station allow us to analyze both datasets together, to

  20. Seismic sources

    DOEpatents

    Green, Michael A.; Cook, Neville G. W.; McEvilly, Thomas V.; Majer, Ernest L.; Witherspoon, Paul A.

    1992-01-01

    Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Logitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole relative to a stator that is clamped to the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements at a power level that causes heating to over 150.degree. C. within one minute of operation, but energizing the elements for no more than about one minute.

  1. Seismic interferometry for temporal monitoring

    NASA Astrophysics Data System (ADS)

    Nakata, Norimitsu

    Seismic interferometry, where one computes coherency of waves between two or more receivers and averages over many sources, is a technique of signal processing to reconstruct wavefields. This technique is used in geophysics, especially exploration geophysics and seismology. After more than a half century from the first study related to seismic interferometry (although the name of seismic interferometry has been used for approximately the last 15 years), researchers have developed this technique for many aspects: using multiples for increasing illuminations, enhancement of survey areas, ambient-noise analysis, and removal of the imprint of a complicated overburden. In this dissertation, I focus on the advantages of seismic interferometry for time-lapse measurements. Measurements of temporal changes yield beneficial information of fluid flow, crustal deformation, temperature, and/or stress. Estimation of temporal changes using active sources is, however, technically and economically challenging. Because seismic interferometry reconstruct waves that would have been recorded with a repeatable active sources using only receivers, this technique is appropriate for temporal monitoring. With seismic interferometry, one obtains some advantages that include canceling the complexity of wave propagation to a virtual source, creating virtual shear-wave (S-wave) sources (active S sources are expensive), and using waves that are not usable for active sources (e.g., ambient noise and multiples). I seek applications of seismic interferometry in a variety of topics (i.e., seismology, structural engineering, and exploration geophysics), and develop and/or modify several techniques of seismic interferometry for each application. Some chapters focus on developing techniques of seismic interferometry, and other chapters aim to estimate and interpret temporal changes with the developed techniques. For passive seismic sources, deconvolution-based seismic interferometry has better

  2. A new wrinkle in seismic filtering aids interpretation

    SciTech Connect

    Lindsey, P.

    1984-11-01

    Application of continuous time-variant deconvolution on a seismic record provides for improvement in resolution, suppression of residual ground roll, elimination of spurious geophone resonances and reduction of moderate power line interference. The overall benefit, of course, is improved interpretability of a seismic section, which allows for the identification of more subtle, often overlooked, geologic features.

  3. Natural fracture characterization using passive seismic illumination

    SciTech Connect

    Nihei, K.T.

    2003-01-08

    The presence of natural fractures in reservoir rock can significantly enhance gas production, especially in tight gas formations. Any general knowledge of the existence, location, orientation, spatial density, and connectivity of natural fractures, as well as general reservoir structure, that can be obtained prior to active seismic acquisition and drilling can be exploited to identify key areas for subsequent higher resolution active seismic imaging. Current practices for estimating fracture properties before the acquisition of surface seismic data are usually based on the assumed geology and tectonics of the region, and empirical or fracture mechanics-based relationships between stratigraphic curvature and fracturing. The objective of this research is to investigate the potential of multicomponent surface sensor arrays, and passive seismic sources in the form of local earthquakes to identify and characterize potential fractured gas reservoirs located near seismically active regions. To assess the feasibility of passive seismic fracture detection and characterization, we have developed numerical codes for modeling elastic wave propagation in reservoir structures containing multiple, finite-length fractures. This article describes our efforts to determine the conditions for favorable excitation of fracture converted waves, and to develop an imaging method that can be used to locate and characterize fractures using multicomponent, passive seismic data recorded on a surface array.

  4. Q analysis on reflection seismic data

    NASA Astrophysics Data System (ADS)

    Wang, Yanghua

    2004-09-01

    Q analysis refers to the procedure for estimating Q directly from a reflection seismic trace. Conventional Q analysis method compares two seismic wavelets selected from different depth (or time) levels, but picking ``clean'' wavelets without interferences from other wavelet and noise from a reflection seismic trace is really a problem. Therefore, instead of analysing individual wavelets, I perform Q analysis using the Gabor transform spectrum which reveals the frequency content changing with time in a seismic trace. I propose two Q analysis methods based on the attenuation function and compensation function, respectively, each of which may produce a series of average values of Q-1 (inverse Q), averaging between the recording surface (or the water bottom) and the subsurface time samples. But the latter is much more stable than the former one. I then calculate the interval or layered values of Q-1 by a constrained linear inversion, which produces a stable estimation of the interval-Q series.

  5. Earthquake Data Recorded by the MEMS Accelerometer

    SciTech Connect

    Holland, Austin Adams

    2003-01-01

    The Idaho National Engineering and Environmental Laboratory (INEEL) operates 26 seismic stations remotely located in southeastern Idaho and 25 strong-motion accelerographs located at critical facilities at the INEEL Site. The INEEL seismic network has upgraded standard analog instrumentation at all of its seismic station to digital recording systems. Seismic data are transmitted to a central recording laboratory in Idaho Falls, Idaho using 900 MHz wireless modems. The INEEL has also chosen digital recording systems to replace the 25 analog film-recording strong-motion accelerographs. The INEEL chose to field test the Applied MEMS Inc., model SF1500A tri-axial accelerometeri with the digital recording system for suitability in earthquake ground motion recording.

  6. The Configurable Seismic Monitoring System (CSMS): Local Seismic Network (LSN) data acquisition user's manual: Version 1. 0

    SciTech Connect

    Peterson, S.J.; Zucca, J.J.; Ewert, D.W.; Moccia, D.J.; Rock, D.W.; Stager, R.K.

    1988-09-01

    The Configurable Seismic Monitoring System (CSMS) is a portable seismograph system that can be used for a variety of applications. In its primary format, the CSMS is the Local Seismic Network (LSN); however, the CSMS could be used for site surveys in advance of installing permanent single stations and arrays. It could also be used for special experiments requiring portable recording equipment. 4 figs.

  7. Seismic intrusion detector system

    DOEpatents

    Hawk, Hervey L.; Hawley, James G.; Portlock, John M.; Scheibner, James E.

    1976-01-01

    A system for monitoring man-associated seismic movements within a control area including a geophone for generating an electrical signal in response to seismic movement, a bandpass amplifier and threshold detector for eliminating unwanted signals, pulse counting system for counting and storing the number of seismic movements within the area, and a monitoring system operable on command having a variable frequency oscillator generating an audio frequency signal proportional to the number of said seismic movements.

  8. Using GPU for Seismic Emission Tomography processing

    NASA Astrophysics Data System (ADS)

    Dricker, I. G.; Cooke, A. J.; Friberg, P. A.; Hellman, S. B.

    2010-12-01

    Seismic Emission Tomography (SET) is an emerging technique which is rapidly gaining popularity in both earthquake seismology and the oil and gas industry. Stacking seismic records from multiple channels of a surface seismic array with moveout correction dramatically increases the signal-to-noise ratio and allows monitoring of fine-scale microseismicity. Using SET to detect active seismic locations within the study volume requires time-shifting and stacking the trace for each seismic recording channel and node in the 3D Earth grid. Algorithmically, this implies five nested loops over space coordinates, channel lists and time. Even the most powerful PC CPUs proved impractical for this task; only rough models could be built in a reasonable period of time. Fortunately the SET computational kernel is easy to parallelize, because computations for each grid node and recording channel are independent, so we could achieve significant (of order x100) speedups on Nvidia GPUs with OpenCL. In this case study we show how progressive optimization, from Matlab to C, and on to OpenCL, improved performance. We discuss various problems encountered, give practical guidance on refactoring, and include benchmarks on several GPUs.

  9. The development of the Moldova digital seismic network

    NASA Astrophysics Data System (ADS)

    Ilies, I.; Ionescu, C.; Grigore, A. G.

    2009-04-01

    The Republic of Moldova is located in the seismically active region, about 70% of its area is predisposed to shaking intensity 7 - 8 points MSK. Focal zones of the primary seismic danger to the territory of the Republic of Moldova are: Vrancea zone - for the whole of its territory and Dobrogea zone - for the southern part. Monitoring of seismic instrumentation in the republic is provided by the Center of Experimental Seismology, Institute of Geology and Seismology, Academy of Sciences of Moldova. According to the seismic zoning map of the Republic of Moldova, seismic stations "Cahul, Leova" and "Giurgiulesti" located in 8 - degree zone, the central regional station "Chisinau" - in 7 - degree, a station "Soroca" - in 6 - degree zone MSK scale. The development of seismic network since 2004, going through a transition to a modern digital recording, improving working conditions for staff and the construction of new buildings for seismic stations, equipping the new network equipment and improve the methods of collecting and processing seismic data. The works to modernize the network of seismic stations in Moldova were initiated in 2003 with the acquisition of the first three axial digital accelerometer. The device was installed initially in Chisinau, and from it we received the first digital recordings of earthquakes from September 27 and October 27, 2004. In joint efforts with National Institute of Research and Development for Earth Physics from Bucharest, Romania, four seismic stations from Republic of Moldavia was upgraded by broadband and strong motion sensors connected at Q 330 digital recorders that issue continuous recording and real time data stream. Starting from spring of 2008, real time seismic data exchange between IGG Republic of Moldavia and NIEP Romania is running using internet connection.

  10. Introduction about Seismic array Laboratory, IGGCAS

    NASA Astrophysics Data System (ADS)

    Ai, Y.; Xu, W.

    2007-12-01

    Seismic Array Laboratory (SAL, IGGCAS) was built up in 2000, whose initiative was to study the earth structures through portable seismic observation and it has been operating for about 7 years till now. Totally, the lab have 272 sets of seismographs, including 152 CMG-3ESP seismometers, 18 CMG-3T seismometers, 2 STS-2 seismometers, 100 domestic seismometers, 172 Reftek recording system and 100 domestic recording system, respectively. The seismographs in IGGCAS are only used for temporary seismic observations and are open to users who aim at seismic observation based research and, in principle, are able to afford instrument rental. For the past seven years, more than 10 scientific research groups have used these seismographs and set up more than 470 portable stations in Chinese mainland. Up to now, IGGCAS has carried out 15 temporary seismic station arrays which are mainly distributed in North and Southwest China. The data collected at these seismic stations are currently managed by the SAL of IGGCAS and some regulations have been set down for data usage. Users who implement seismic observations with the seismographs in IGGCAS have three years priority to use the corresponding seismic data after field operation. Then, those data should be released by the SAL of IGGCAS. Now, parts of the data have been open to public through the website http://www.seislab.cn/data, and currently, only some event data in SAC format are released due to the lack of high-level technicians dealing with data pre- processing and quality control. In the near future, the lab will release more data in multiple formats to facilitate researchers in relative area via internet connection.

  11. Probabilistic seismic demand analysis of nonlinear structures

    NASA Astrophysics Data System (ADS)

    Shome, Nilesh

    Recent earthquakes in California have initiated improvement in current design philosophy and at present the civil engineering community is working towards development of performance-based earthquake engineering of structures. The objective of this study is to develop efficient, but accurate procedures for probabilistic analysis of nonlinear seismic behavior of structures. The proposed procedures help the near-term development of seismic-building assessments which require an estimation of seismic demand at a given intensity level. We also develop procedures to estimate the probability of exceedance of any specified nonlinear response level due to future ground motions at a specific site. This is referred as Probabilistic Seismic Demand Analysis (PSDA). The latter procedure prepares the way for the next stage development of seismic assessment that consider the uncertainties in nonlinear response and capacity. The proposed procedures require structure-specific nonlinear analyses for a relatively small set of recorded accelerograms and (site-specific or USGS-map-like) seismic hazard analyses. We have addressed some of the important issues of nonlinear seismic demand analysis, which are selection of records for structural analysis, the number of records to be used, scaling of records, etc. Initially these issues are studied through nonlinear analysis of structures for a number of magnitude-distance bins of records. Subsequently we introduce regression analysis of response results against spectral acceleration, magnitude, duration, etc., which helps to resolve these issues more systematically. We illustrate the demand-hazard calculations through two major example problems: a 5story and a 20-story SMRF building. Several simple, but quite accurate closed-form solutions have also been proposed to expedite the demand-hazard calculations. We find that vector-valued (e.g., 2-D) PSDA estimates demand hazard more accurately. This procedure, however, requires information about 2

  12. Expanding Conventional Seismic Stratigrphy into the Multicomponent Seismic Domain

    SciTech Connect

    Innocent Aluka

    2008-08-31

    Multicomponent seismic data are composed of three independent vector-based seismic wave modes. These wave modes are, compressional mode (P), and shear modes SV and SH. The three modes are generated using three orthogonal source-displacement vectors and then recorded using three orthogonal vector sensors. The components travel through the earth at differing velocities and directions. The velocities of SH and SV as they travel through the subsurface differ by only a few percent, but the velocities of SV and SH (Vs) are appreciably lower than the P-wave velocity (Vp). The velocity ratio Vp/Vs varies by an order of magnitude in the earth from a value of 15 to 1.5 depending on the degree of sedimentary lithification. The data used in this study were acquired by nine-component (9C) vertical seismic profile (VSP), using three orthogonal vector sources. The 9C vertical seismic profile is capable of generating P-wave mode and the fundamental S-wave mode (SH-SH and SV-SV) directly at the source station and permits the basic components of elastic wavefield (P, SH-SH and SV-SV) to be separated from one another for the purposes of imaging. Analysis and interpretations of data from the study area show that incident full-elastic seismic wavefield is capable of reflecting four different wave modes, P, SH , SV and C which can be utilized to fully understand the architecture and heterogeneities of geologic sequences. The conventional seismic stratigraphy utilizes only reflected P-wave modes. The notation SH mode is the same as SH-SH; SV mode means SV-SV and C mode which is a converted shear wave is a special SV mode and is the same as P-SV. These four wave modes image unique geologic stratigraphy and facies and at the same time reflect independent stratal surfaces because of the unique orientation of their particle-displacement vectors. As a result of the distinct orientation of individual mode's particle-displacement vector, one mode may react to a critical subsurface sequence more

  13. Short-Period Seismic Noise in Vorkuta (Russia)

    SciTech Connect

    Kishkina, S B; Spivak, A A; Sweeney, J J

    2008-05-15

    Cultural development of new subpolar areas of Russia is associated with a need for detailed seismic research, including both mapping of regional seismicity and seismic monitoring of specific mining enterprises. Of special interest are the northern territories of European Russia, including shelves of the Kara and Barents Seas, Yamal Peninsula, and the Timan-Pechora region. Continuous seismic studies of these territories are important now because there is insufficient seismological knowledge of the area and an absence of systematic data on the seismicity of the region. Another task of current interest is the necessity to consider the seismic environment in the design, construction, and operation of natural gas extracting enterprises such as the construction of the North European Gas Pipeline. Issues of scientific importance for seismic studies in the region are the complex geodynamical setting, the presence of permafrost, and the complex tectonic structure. In particular, the Uralian Orogene (Fig. 1) strongly affects the propagation of seismic waves. The existing subpolar seismic stations [APA (67,57{sup o}N; 33,40{sup o}E), LVZ (67,90{sup o}N; 34,65{sup o}E), and NRIL (69,50{sup o}N; 88,40{sup o}E)] do not cover the extensive area between the Pechora and Ob Rivers (Fig. 1). Thus seismic observations in the Vorkuta area, which lies within the area of concern, represent a special interest. Continuous recording at a seismic station near the city of Vorkuta (67,50{sup o}N; 64,11{sup o}E) [1] has been conducted since 2005 for the purpose of regional seismic monitoring and, more specifically, detection of seismic signals caused by local mining enterprises. Current surveys of local seismic noise [7,8,9,11], are particularly aimed at a technical survey for the suitability of the site for installation of a small-aperture seismic array, which would include 10-12 recording instruments, with the Vorkuta seismic station as the central element. When constructed, this seismic

  14. Tube-wave seismic imaging

    DOEpatents

    Korneev, Valeri A [LaFayette, CA

    2009-05-05

    The detailed analysis of cross well seismic data for a gas reservoir in Texas revealed two newly detected seismic wave effects, recorded approximately 2000 feet above the reservoir. A tube-wave (150) is initiated in a source well (110) by a source (111), travels in the source well (110), is coupled to a geological feature (140), propagates (151) through the geological feature (140), is coupled back to a tube-wave (152) at a receiver well (120), and is and received by receiver(s) (121) in either the same (110) or a different receiving well (120). The tube-wave has been shown to be extremely sensitive to changes in reservoir characteristics. Tube-waves appear to couple most effectively to reservoirs where the well casing is perforated, allowing direct fluid contact from the interior of a well case to the reservoir.

  15. Seismic detection of sonic booms.

    PubMed

    Cates, Joseph E; Sturtevant, Bradford

    2002-01-01

    The pressure signals from a sonic boom will produce a small, but detectable, ground motion. The extensive seismic network in southern California, consisting of over 200 sites covering over 50000 square kilometers, is used to map primary and secondary sonic boom carpets. Data from the network is used to analyze three supersonic overflights in the western United States. The results are compared to ray-tracing computations using a realistic model of the stratified atmospheric at the time of the measurements. The results show sonic boom ground exposure under the real atmosphere is much larger than previously expected or predicted by ray tracing alone. Finally, seismic observations are used to draw some inferences on the origin of a set of "mystery booms" recorded in 1992-1993 in southern California. PMID:11837967

  16. Tube-wave seismic imaging

    DOEpatents

    Korneev, Valeri A.; Bakulin, Andrey

    2009-10-13

    The detailed analysis of cross well seismic data for a gas reservoir in Texas revealed two newly detected seismic wave effects, recorded approximately 2000 feet above the reservoir. A tube-wave (150) is initiated in a source well (110) by a source (111), travels in the source well (110), is coupled to a geological feature (140), propagates (151) through the geological feature (140), is coupled back to a tube-wave (152) at a receiver well (120), and is and received by receiver(s) (121) in either the same (110) or a different receiving well (120). The tube-wave has been shown to be extremely sensitive to changes in reservoir characteristics. Tube-waves appear to couple most effectively to reservoirs where the well casing is perforated, allowing direct fluid contact from the interior of a well case to the reservoir.

  17. An economical educational seismic system

    USGS Publications Warehouse

    Lehman, J. D.

    1980-01-01

    There is a considerable interest in seismology from the nonprofessional or amateur standpoint. The operation of a seismic system can be satisfying and educational, especially when you have built and operated the system yourself. A long-period indoor-type sensor and recording system that works extremely well has been developed in the James Madison University Physics Deparment. The system can be built quite economically, and any educational institution that cannot commit themselves to a professional installation need not be without first-hand seismic information. The system design approach has been selected by college students working a project or senior thesis, several elementary and secondary science teachers, as well as the more ambitious tinkerer or hobbyist at home 

  18. The ISC Seismic Event Bibliography

    NASA Astrophysics Data System (ADS)

    Di Giacomo, Domenico; Storchak, Dmitry

    2015-04-01

    The International Seismological Centre (ISC) is a not-for-profit organization operating in the UK for the last 50 years and producing the ISC Bulletin - the definitive worldwide summary of seismic events, both natural and anthropogenic - starting from the beginning of 20th century. Often researchers need to gather information related to specific seismic events for various reasons. To facilitate such task, in 2012 we set up a new database linking earthquakes and other seismic events in the ISC Bulletin to bibliographic records of scientific articles (mostly peer-reviewed journals) that describe those events. Such association allows users of the ISC Event Bibliography (www.isc.ac.uk/event_bibliography/index.php) to run searches for publications via a map-based web interface and, optionally, selecting scientific publications related to either specific events or events in the area of interest. Some of the greatest earthquakes were described in several hundreds of articles published over a period of few years. The journals included in our database are not limited to seismology but bring together a variety of fields in geosciences (e.g., engineering seismology, geodesy and remote sensing, tectonophysics, monitoring research, tsunami, geology, geochemistry, hydrogeology, atmospheric sciences, etc.) making this service useful in multidisciplinary studies. Usually papers dealing with large data set are not included (e.g., papers describing a seismic catalogue). Currently the ISC Event Bibliography includes over 17,000 individual publications from about 500 titles related to over 14,000 events that occurred in last 100+ years. The bibliographic records in the Event Bibliography start in the 1950s, and it is updated as new publications become available.

  19. Seismic Imaging from a TBM

    NASA Astrophysics Data System (ADS)

    Swinnen, G.; Thorbecke, J. W.; Drijkoningen, G. G.

    2007-12-01

    Seismic monitoring from the head of a tunnel-boring machine (TBM) enables improved assessment of the risks associated with the tunnel-boring process. The monitoring system provides a live image of ground conditions along the trajectory followed by the TBM and detects local heterogeneities such as boulders, foundations, and other obstacles that commonly pass undetected using local geotechnical techniques. From a seismic perspective, the underground setting of tunnelling projects places limitations on imaging capability. The principal limiting factor is the size of the area upon which transducers can be installed. This limitation requires adjustments to traditional seismic imaging techniques in which a large area is assumed to be available for attaching the transducers. Recently developed short imaging operators take this limitation into account and are used in the examples described herein. The unique conditions of tunnelling yield two advantages over traditional settings in terms of imaging: rotation of the cutter wheel and the lateral progression of the TBM. Rotation of the cutter wheel, upon which the transducers are installed, provides the opportunity to illuminate obstacles from different angles in different recordings. Spatial progression of the TBM enables improvement in the illumination of obstacles and the signal-to-noise ratio by combining recordings from different lateral positions. In this paper, these specific aspects of seismic imaging during tunnelling are discussed via models that represent different cases encountered in actual tunnelling projects. These case studies demonstrate the way in which image quality along the trajectory of the TBM is improved over that in traditional settings. In this way, the risks associated with the tunnelling process can be more accurately assured.

  20. Statistical Seismology and Induced Seismicity

    NASA Astrophysics Data System (ADS)

    Tiampo, K. F.; González, P. J.; Kazemian, J.

    2014-12-01

    While seismicity triggered or induced by natural resources production such as mining or water impoundment in large dams has long been recognized, the recent increase in the unconventional production of oil and gas has been linked to rapid rise in seismicity in many places, including central North America (Ellsworth et al., 2012; Ellsworth, 2013). Worldwide, induced events of M~5 have occurred and, although rare, have resulted in both damage and public concern (Horton, 2012; Keranen et al., 2013). In addition, over the past twenty years, the increase in both number and coverage of seismic stations has resulted in an unprecedented ability to precisely record the magnitude and location of large numbers of small magnitude events. The increase in the number and type of seismic sequences available for detailed study has revealed differences in their statistics that previously difficult to quantify. For example, seismic swarms that produce significant numbers of foreshocks as well as aftershocks have been observed in different tectonic settings, including California, Iceland, and the East Pacific Rise (McGuire et al., 2005; Shearer, 2012; Kazemian et al., 2014). Similarly, smaller events have been observed prior to larger induced events in several occurrences from energy production. The field of statistical seismology has long focused on the question of triggering and the mechanisms responsible (Stein et al., 1992; Hill et al., 1993; Steacy et al., 2005; Parsons, 2005; Main et al., 2006). For example, in most cases the associated stress perturbations are much smaller than the earthquake stress drop, suggesting an inherent sensitivity to relatively small stress changes (Nalbant et al., 2005). Induced seismicity provides the opportunity to investigate triggering and, in particular, the differences between long- and short-range triggering. Here we investigate the statistics of induced seismicity sequences from around the world, including central North America and Spain, and

  1. Annual Hanford Seismic Report for Fiscal Year 2007

    SciTech Connect

    Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E.; Devary, Joseph L.

    2007-12-27

    This annual report documents the locations, magnitudes, and geologic interpretations of earthquakes recorded for the Hanford monitoring region of south-central Washington in fiscal year 2007 (October 2006 through September 2007). The report provides summaries of seismic events recorded during the first three quarters of fiscal year 2007 and contains a more comprehensive discussion of seismic events for the fourth quarter of the fiscal year.

  2. 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.

  3. Seismic structure of the moon - A summary of current status

    NASA Technical Reports Server (NTRS)

    Nakamura, Y.; Latham, G. V.; Dorman, H. J.; Duennebier, F. K.

    1976-01-01

    A seismic model of the moon, refined from previous models with the aid of new data and analyses for seismic events recorded by four Apollo lunar seismic stations and a gravimeter, is outlined. The current model has five zones. The crust is 55-60 km thick. The surface is covered by regolith of varying thicknesses and low seismic velocity. The seismic Q's are extremely high. The upper mantle, 250 km thick, is characterized by seismic velocities close to those of the earth's upper mantle, and shear wave Q of about 4000. Tidally controlled deep moonquakes are concentrated near the boundary of the middle mantle, 600-700 km thick. A lower mantle extending to an undetermined depth is characterized by high attenuation of shear waves. The existence of a low-velocity core is only tentatively proposed.

  4. Stochastic seismic analysis in the Messina strait area

    SciTech Connect

    Cacciola, P.; Maugeri, N.; Muscolino, G.

    2008-07-08

    After 1908 Messina earthquake significant progresses have been carried out in the field of earthquake engineering. Usually seismic action is represented via the so called elastic response spectrum or alternatively by time histories of ground motion acceleration. Due the random nature of the seismic action, alternative representations assume the seismic action as zero-mean Gaussian process fully defined by the so-called Power Spectral Density function. Aim of this paper is the comparative study of the response of linear behaving structures adopting the above representation of the seismic action using recorded earthquakes in the Messina strait area. In this regard, a handy method for determining the power spectral density function of recorded earthquakes is proposed. Numerical examples conducted on the existing space truss located in Torre Faro (Messina) will show the effectiveness of stochastic approach for coping with the seismic analysis of structures.

  5. 2013 East Bay Seismic Experiment (EBSE): implosion data, Hayward, Calif

    USGS Publications Warehouse

    Catchings, Rufus D.; Strayer, Luther M.; Goldman, Mark R.; Criley, Coyn J.; Garcia, Susan; Sickler, Robert R.; Catchings, Marisol K.; Chan, Joanne; Gordon, Leslie C.; Haefner, Scott; Blair, James Luke; Gandhok, Gini; Johnson, Michaela R.

    2015-01-01

    In August 2013, the California State University, East Bay (CSUEB) in Hayward, California imploded a 13-story building (Warren Hall) that was deemed unsafe because of its immediate proximity to the active trace of the Hayward Fault. The U.S. Geological Survey (USGS) and the CSUEB collaborated on a program to record the seismic waves generated by the collapse of the building. We refer to this collaboration as the East Bay Seismic Experiment (EBSE). The principal objective of recording the seismic energy was to observe ground shaking as it radiated from the source, but the data also may be useful for other purposes. For example, the seismic data may be useful in evaluating the implosion process as it relates to structural engineering purposes. This report provides the metadata needed to utilize the seismic data.

  6. Man-induced low-frequency seismic events in Italy

    NASA Astrophysics Data System (ADS)

    Latorre, Diana; Amato, Alessandro; Cattaneo, Marco; Carannante, Simona; Michelini, Alberto

    2014-12-01

    Unconventional seismic events in Italy are detected by scanning three years of continuous waveforms recorded by the Italian National Seismic Network. Cross correlation of signal templates with continuous seismic records has evidenced unusual events with similar low-frequency characteristics in several Italian regions. Spectral analysis and spatiotemporal distribution of these events, some of which are previously interpreted as tectonic long-period transients, suggest that they are not natural, but produced by huge cement factories. Since there are at least 57 full-cycle cement plants operating in Italy, each affecting areas of about 1250 to 2800 km2, we argue that significant portions of the Italian territory (23% to 51%) can be affected by this man-made noise. Seismic noise analyses, such as those used for microzonation or crustal structure investigations, as well as data mining techniques used to retrieve anomalous transient signals, should thus take into account this peculiar and pervasive source of seismic waves.

  7. Missile impacts as sources of seismic energy on the moon

    USGS Publications Warehouse

    Latham, G.V.; McDonald, W.G.; Moore, H.J.

    1970-01-01

    Seismic signals recorded from impacts of missiles at the White Sands Missile Range are radically different from the signal recorded from the Apollo 12 lunar module impact. This implies that lunar structure to depths of at least 10 to 20 kilometers is quite different from the typical structure of the earth's crust. Results obtained from this study can be used to predict seismic wave amplitudes from future man-made lunar impacts. Seismic energy and crater dimensions from impacts are compared with measurements from chemical explosions.

  8. Man-caused seismicity of Kuzbass

    NASA Astrophysics Data System (ADS)

    Emanov, Alexandr; Emanov, Alexey; Leskova, Ekaterina; Fateyev, Alexandr

    2010-05-01

    A natural seismicity of Kuznetsk Basin is confined in the main to mountain frame of Kuznetsk hollow. In this paper materials of experimental work with local station networks within sediment basin are presented. Two types of seismicity display within Kuznetsk hollow have been understood: first, man-caused seismic processes, confined to mine working and concentrated on depths up to one and a half of km; secondly, seismic activations on depths of 2-56 km, not coordinated in plan with coal mines. Every of studied seismic activations consists of large quantity of earthquakes of small powers (Ms=1-3). From one to first tens of earthquakes were recorded in a day. The earthquakes near mine working shift in space along with mine working, and seismic process become stronger at the instant a coal-plough machine is operated, and slacken at the instant the preventive works are executed. The seismic processes near three lavas in Kuznetsk Basin have been studied in detail. Uplift is the most typical focal mechanism. Activated zone near mine working reach in diameter 1-1,5 km. Seismic activations not linked with mine working testify that the subsoil of Kuznetsk hollow remain in stress state in whole. The most probable causes of man-caused action on hollow are processes, coupled with change of physical state of rocks at loss of methane from large volume or change by mine working of rock watering in large volume. In this case condensed rocks, lost gas and water, can press out upwards, realizing the reverse fault mechanism of earthquakes. A combination of stress state of hollow with man-caused action at deep mining may account for incipient activations in Kuznetsk Basin. Today earthquakes happen mainly under mine workings, though damages of workings themselves do not happen, but intensive shaking on surface calls for intent study of so dangerous phenomena. In 2009 replicates of the experiment on research of seismic activations in area of before investigated lavas have been conducted

  9. Seismic slip deficit along Nepal Himalayas: implications for seismic hazard

    NASA Astrophysics Data System (ADS)

    Bollinger, Laurent; Tapponnier, Paul; Nath Sapkota, Soma; Klinger, Yann

    2016-04-01

    In 1255, 1344 and 1408 AD, then again in 1833, 1934 and 2015, large earthquakes, devastated Kathmandu. The 1255 and 1934 surface ruptures have been identified east of the city, along comparable segments of the Main Frontal Thrust (MFT). Whether the other two pairs of events were similar, is unclear. Taking into account charcoal's "Inbuilt-ages", we revisit the timing of terrace offsets at key sites, to compare them with the seismic record since 1200 AD. The location, extent, and seismic moment of the 1833 and 2015 events imply that they released only a small part of the regional slip deficit, on a deep thrust segment that stopped north of the Siwaliks. By contrast, the 1344 or 1408 AD earthquake may have ruptured the MFT up to the surface in central Nepal between Kathmandu and Pokhara, East of the surface trace of the great 1505 AD earthquake which affected Western Nepal. If so, the whole megathrust system in Nepal ruptured during a sequence of earthquakes that lasted less than three centuries and propagated the rupture up to the surface from East to West. Today's situation in the himalayan seismic sequence might be close to that of the 14th century.

  10. Experimental seismic investigations for porous media characterization

    NASA Astrophysics Data System (ADS)

    Senechal, P.; Bordes, C.; Barrière, J.; Garambois, S.; Brito, D.

    2009-12-01

    During decades, seismic investigations were based on the hypothesis of elastic media which is generally appropriate for geological imaging. Nevertheless, the necessity to improve non destructive geophysical methods for reservoir characterization implies to take into account the role of pore fluids for the seismic propagation. On the one hand, the water saturation modifies porous media bulk moduli and density and implies strong phase velocity variations. On the other hand, mechanical couplings between solid and fluid phases which can have inertial or viscous origin, generates attenuation and dispersion phenomena. In order to study these phenomena, we develop laboratory experiments for the measurement of seismic propagation in controlled porous media. We choose to work in a broad band [100-10 000 Hz] which includes Biot's frequency by using different seismic source (launched ball, pendulum, piezoelectric spherical source). These investigations are performed on various media from suspension (fresh concrete) to continuous framework (sand). Seismic propagation is recorded by accelerometers, discussed in term of frequency content, velocity analyses, attenuation and dispersion and compared to theoretical models. Moreover, seismoelectric measurements are used to study fluid displacements (filtration) associated to the seismic propagation.

  11. Angola Seismicity MAP

    NASA Astrophysics Data System (ADS)

    Neto, F. A. P.; Franca, G.

    2014-12-01

    The purpose of this job was to study and document the Angola natural seismicity, establishment of the first database seismic data to facilitate consultation and search for information on seismic activity in the country. The study was conducted based on query reports produced by National Institute of Meteorology and Geophysics (INAMET) 1968 to 2014 with emphasis to the work presented by Moreira (1968), that defined six seismogenic zones from macro seismic data, with highlighting is Zone of Sá da Bandeira (Lubango)-Chibemba-Oncócua-Iona. This is the most important of Angola seismic zone, covering the epicentral Quihita and Iona regions, geologically characterized by transcontinental structure tectono-magmatic activation of the Mesozoic with the installation of a wide variety of intrusive rocks of ultrabasic-alkaline composition, basic and alkaline, kimberlites and carbonatites, strongly marked by intense tectonism, presenting with several faults and fractures (locally called corredor de Lucapa). The earthquake of May 9, 1948 reached intensity VI on the Mercalli-Sieberg scale (MCS) in the locality of Quihita, and seismic active of Iona January 15, 1964, the main shock hit the grade VI-VII. Although not having significant seismicity rate can not be neglected, the other five zone are: Cassongue-Ganda-Massano de Amorim; Lola-Quilengues-Caluquembe; Gago Coutinho-zone; Cuima-Cachingues-Cambândua; The Upper Zambezi zone. We also analyzed technical reports on the seismicity of the middle Kwanza produced by Hidroproekt (GAMEK) region as well as international seismic bulletins of the International Seismological Centre (ISC), United States Geological Survey (USGS), and these data served for instrumental location of the epicenters. All compiled information made possible the creation of the First datbase of seismic data for Angola, preparing the map of seismicity with the reconfirmation of the main seismic zones defined by Moreira (1968) and the identification of a new seismic

  12. Vulcanian explosions in the process of building-destruction of the lava dome of andesitic volcano: Insight from the seismic signals recorded at Volcán de Colima, México

    NASA Astrophysics Data System (ADS)

    Zobin, Vyacheslav M.; Peral, Juan J.; Nava, Fernando; Bretón, Mauricio

    2015-07-01

    The seismic signals associated with the Vulcanian explosive events at Volcán de Colima, México during its 1998-2014 eruption were discriminated into three types according the waveforms of their initial phases. This classification includes about 85-90% of all seismic signals associated with explosive events. It was shown that the classification of the explosive seismic signals gave a useful tool for analysis of the eruption development. Analysis was performed for two 6-month stages of the eruption, the 2003 post-effusive stage culminated with large explosions and the 2007 co-effusive stage during the beginning of new lava dome growth in the crater of the volcano. The predominance (95%) of the type 1 and 3 events with low-frequency (LF) and high + low frequency (HF + LF) initial phases in the sample of the 2003 post-effusive stage explosive events identifies the termination of the lava effusion and preparation to the stage of large explosions. The high participation (37%) of the type 2 events with high-frequency (HF) initial phases in the sample of the 2007 co-effusive stage explosive events indicates the process of the lava dome growth beginning. The introduction of multi-stage conceptual model of explosive process allows the interpretation of peculiarities of the seismic signals associated with explosive activity. Analysis of the spectral content of the initial LF phases of the seismic signals associated with the explosions showed that the sources of LF initial phases, corresponding to the ascent of magma within the volcanic conduit above the fragmentation zone, were common for post-effusive and co-effusive stages. The source of events with the HF initial phases differed from the source of events with the LF first phases. The sources of explosions at explosion level were situated at different sites during post-effusive and co-effusive stages.

  13. High-resolution seismic array imaging based on numerical seismic wave simulations

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Tong, P.; Chen, C.

    2012-12-01

    Adjoint tomography, i.e., seismic tomography based on full numerical simulations and adjoint methods, is a powerful tool for high-resolution imaging in heterogeneous media. It resolves large velocity contrasts through the use of 3D initial models and exploits more quantitative information from observed seismograms. However, for regions with limited local seismicity, seismic imaging relies more on teleseismic records. In particular coda and converted waves of main teleseismic arrivals used in scattering imaging are vital in resolving subsurface interfaces and velocity anomalies beneath seismic arrays. It remains numerically challenging to accurately and efficiently simulate the full propagation of seismic waves at the frequencies relevant to scattering imaging. In this work, to simulate the propagation of teleseismic planes waves into localized heterogeneous structures, we apply a hybrid method that interacts a spectral-element solver within the domain with a semi-analytical solution for 1D background medium at the absorbing boundaries. This technique will be implemented in both SPECFEM2D and SPECFEM3D packages and make it possible to invert both regional and teleseismic recordings in the framework of adjoint tomography. Synthetic tests will be performed to show the feasibility of high-resolution seismic array imaging of coda and converted waves based on adjoint techniques.

  14. Seismic directional beamforming using cosine amplitude distribution

    NASA Astrophysics Data System (ADS)

    Jiang, T.; Xu, X.; Song, J.; Jia, H.; Ge, L.

    2013-12-01

    o improve the signal-to-noise ratio in seismic exploration, we studied the method of time domain seismic beam-forming based on receiver array (TSBBRA). TSBBRA is useful to extract reflected waves from some target layers and decrease noise from other direction. When noise is strong enough, the control parameter of the method of TSBBRA need to be increased. It means that we have to use more raw records to form a directional seismic record. Therefore, the signal energy in beam is much denser, and the beam becomes narrower accordingly. When the beam can not cover the receiver array, the signal-to-noise ratios in different traces are quite unbalanced and average quality of data probably is still quite low. Therefore, this paper proposes seismic directional beamforming using the cosine amplitude distribution (SDBCAD). SDBCAD can adjust seismic beam shape by introducing cosine amplitude distribution, an amplitude weighting method, in the procedure of beamforming. We studied cosine amplitude weighting function, analyzed the characteristics of uniform and cosine amplitude distribution in beamforming, and compared directivity of beams from the two kind of amplitude pattern. It shows that the main beam of cosine-weighted amplitude is different from uniform distribution. The coverage of main beam from SDBCAD is wider than uniform amplitude, and the width of beam is varied with different number of cosine order. So we simulated the seismic raw record, and used TSBBRA and SDBCAD to process simulated data at the receiving array. The results show that SDBCAD can broaden directional beam, and the main beam from SDBCAD can cover the entire traces instead of partial coverage in TSBBRA. The average signal-to-noise ratio increased 0.2~4.5dB. It concludes that SDBCAD is competent to stretch beam reasonable, and it is useful to boost signal-to-noise ratio when beam from TSBBRA is too narrow to illuminate receiver array properly. Updated results will be presented at the meeting.

  15. Seismicity at Baru Volcano, Western Panama, Panama

    NASA Astrophysics Data System (ADS)

    Camacho, E.; Novelo-Casanova, D. A.; Tapia, A.; Rodriguez, A.

    2008-12-01

    The Baru volcano in Western Panama (8.808°N, 82.543°W) is a 3,475 m high strato volcano that lies at about 50 km from the Costa Rican border. The last major eruptive event at this volcano occurred c.1550 AD and no further eruptive activity from that time is known. Since the 1930´s, approximately every 30 years a series of seismic swarms take place in the surroundings of the volcanic edifice. Theses swarms last several weeks alarming the population who lives near the volcano. The last of these episodes occurred on May 2006 and lasted one and a half months. More than 20,000 people live adjacent to the volcano and any future eruption has the potential to be very dangerous. In June 2007, a digital seismic monitoring network of ten stations, linked via internet, was installed around the volcano in a collaborative project between the University of Panama and the Panamanian Government. The seismic data acquisition at the sites is performed using LINUX-SEISLOG and the events are recorded by four servers at different locations using the Earth Worm system. In this work we analyze the characteristics of the volcano seismicity recorded from May 4th, 2006 to July 31st, 2008 by at least 4 stations and located at about 15 km from the summit. To determine the seismic parameters, we tested several crustal velocity models and used the seismic analysis software package SEISAN. Our final velocity model was determined using seismic data for the first four km obtained from a temporal seismic network deployed in 1981 by the British Geological Survey (BGS) as part of geothermal studies conducted at Cerro Pando, Western Panama Highlands. Our results indicate that all the events recorded in the quadrant 8.6-9.0°N and 82.2-82.7°W are located in the depth range of 0.1 to 8 km. Cross sections show vertical alignments of hypocenters below the summit although most of the seismicity is concentrated in its eastern flank reaching the town of Boquete. All the calculated focal mechanisms are of

  16. 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

  17. Studies of digital seismic data obtained in geothermal and volcanic regions. Progress report

    SciTech Connect

    Fehler, M.

    1982-08-10

    Progress is reported in the following research areas: (1) study of tremor waveforms recorded at Mount St. Helens during 1980; (2) study of seismicity recorded during 1981 at Mount St. Helens; and (3) the monitoring of seismicity accompanying hydrofracturing experiments carried out in the Jemez Mountains of New Mexico. (ACR)

  18. Coherent Waves in Seismic Researches

    NASA Astrophysics Data System (ADS)

    Emanov, A.; Seleznev, V. S.

    2013-05-01

    Development of digital processing algorithms of seismic wave fields for the purpose of useful event picking to study environment and other objects is the basis for the establishment of new seismic techniques. In the submitted paper a fundamental property of seismic wave field coherence is used. The authors extended conception of coherence types of observed wave fields and devised a technique of coherent component selection from observed wave field. Time coherence and space coherence are widely known. In this paper conception "parameter coherence" has been added. The parameter by which wave field is coherent can be the most manifold. The reason is that the wave field is a multivariate process described by a set of parameters. Coherence in the first place means independence of linear connection in wave field of parameter. In seismic wave fields, recorded in confined space, in building-blocks and stratified mediums time coherent standing waves are formed. In prospecting seismology at observation systems with multiple overlapping head waves are coherent by parallel correlation course or, in other words, by one measurement on generalized plane of observation system. For detail prospecting seismology at observation systems with multiple overlapping on basis of coherence property by one measurement of area algorithms have been developed, permitting seismic records to be converted to head wave time sections which have neither reflected nor other types of waves. Conversion in time section is executed on any specified observation base. Energy storage of head waves relative to noise on basis of multiplicity of observation system is realized within area of head wave recording. Conversion on base below the area of wave tracking is performed with lack of signal/noise ratio relative to maximum of this ratio, fit to observation system. Construction of head wave time section and dynamic plots a basis of automatic processing have been developed, similar to CDP procedure in method of

  19. Mapping Europe's Seismic Hazard

    NASA Astrophysics Data System (ADS)

    Giardini, Domenico; Wössner, Jochen; Danciu, Laurentiu

    2014-07-01

    From the rift that cuts through the heart of Iceland to the complex tectonic convergence that causes frequent and often deadly earthquakes in Italy, Greece, and Turkey to the volcanic tremors that rattle the Mediterranean, seismic activity is a prevalent and often life-threatening reality across Europe. Any attempt to mitigate the seismic risk faced by society requires an accurate estimate of the seismic hazard.

  20. Nonlinear Seismic Response Of Single Piles

    SciTech Connect

    Cairo, R.; Conte, E.; Dente, G.

    2008-07-08

    In this paper, a method is proposed to analyse the seismic response of single piles under nonlinear soil condition. It is based on the Winkler foundation model formulated in the time domain, which makes use of p-y curves described by the Ramberg-Osgood relationship. The analyses are performed referring to a pile embedded in two-layer soil profiles with different sharp stiffness contrast. Italian seismic records are used as input motion. The calculated bending moments in the pile are compared to those obtained using other theoretical solutions.

  1. Oklahoma seismic network. Final report

    SciTech Connect

    Luza, K.V.; Lawson, J.E. Jr. |

    1993-07-01

    The US Nuclear Regulatory Commission has established rigorous guidelines that must be adhered to before a permit to construct a nuclear-power plant is granted to an applicant. Local as well as regional seismicity and structural relationships play an integral role in the final design criteria for nuclear power plants. The existing historical record of seismicity is inadequate in a number of areas of the Midcontinent region because of the lack of instrumentation and (or) the sensitivity of the instruments deployed to monitor earthquake events. The Nemaha Uplift/Midcontinent Geophysical Anomaly is one of five principal areas east of the Rocky Mountain front that has a moderately high seismic-risk classification. The Nemaha uplift, which is common to the states of Oklahoma, Kansas, and Nebraska, is approximately 415 miles long and 12-14 miles wide. The Midcontinent Geophysical Anomaly extends southward from Minnesota across Iowa and the southeastern corner of Nebraska and probably terminates in central Kansas. A number of moderate-sized earthquakes--magnitude 5 or greater--have occurred along or west of the Nemaha uplift. The Oklahoma Geological Survey, in cooperation with the geological surveys of Kansas, Nebraska, and Iowa, conducted a 5-year investigation of the seismicity and tectonic relationships of the Nemaha uplift and associated geologic features in the Midcontinent. This investigation was intended to provide data to be used to design nuclear-power plants. However, the information is also being used to design better large-scale structures, such as dams and high-use buildings, and to provide the necessary data to evaluate earthquake-insurance rates in the Midcontinent.

  2. "Interactive Seismics", Aki & Richards, Chapter 16

    NASA Astrophysics Data System (ADS)

    Leary, P. C.; Walter, L.; Crampin, S.

    2004-12-01

    The defining physical character of cold brittle crustal rock hosting geofluid reservoirs and earthquake instabilities is '1/f-noise' spatially-correlated fluctuations in fracture-density. Evidence for 1/f-noise fracture-density fluctuations is manifest in power-law-scaling well-log spectra from <1/km to >1/cm, spatial correlation of well-core porosity and log(permeability), and the Gutenberg-Richter relation. Unlike spatially-uncorrelated randomness, power-law-scaling spatially-correlated randomness provides no reliable spatio-predictive relation between a sample and the whole. In particular, no point-measurement sequence in a crustal reservoir -- static well-log, temporal pressure-log or strain-log, or earthquake locations - accurately samples a reservoir state. Rather, useful knowledge of a reservoir state requires broadband observation of the whole reservoir as it is perturbed. Such observations could be called 'interactive seismics'. 'Interactive seismics' reservoir monitoring is becoming routine in the oil and gas industry, as embedded sensors record time-lapse source signals to determine where water replaces produced oil and gas. Interactive seismics is feasible with CO2 injection, and may become feasible for active fault zones. Interactive seismics benefits from stable downhole sources and sensors. Imperatives for better hydrocarbon reservoir observation are providing compact, robust, stable seismic sources and vector-sensors, and the means to deploy them downhole. Extensive crosswell seismic data, including monitored travel-times in a tectonically active crust, establish useful performance levels for downhole seismic sourcing at wavelengths 5-50m: crosswell transmission scale ˜1km, single-well back-scattering scale ˜200m, source wavelet stability \\delta S/S ˜ 0.03%, and travel-time resolution \\delta\\tau/\\tau ˜ 0.03%. Using the attested downhole source parameters, we simulate interactive seismic observation of a 1/f-noise fracture volume undergoing

  3. Seismic Imaging and Monitoring

    SciTech Connect

    Huang, Lianjie

    2012-07-09

    I give an overview of LANL's capability in seismic imaging and monitoring. I present some seismic imaging and monitoring results, including imaging of complex structures, subsalt imaging of Gulf of Mexico, fault/fracture zone imaging for geothermal exploration at the Jemez pueblo, time-lapse imaging of a walkway vertical seismic profiling data for monitoring CO{sub 2} inject at SACROC, and microseismic event locations for monitoring CO{sub 2} injection at Aneth. These examples demonstrate LANL's high-resolution and high-fidelity seismic imaging and monitoring capabilities.

  4. Time-lapse seismic imaging of the Reykjanes geothermal reservoir

    NASA Astrophysics Data System (ADS)

    Weemstra, Cornelis; Obermann, Anne; Blanck, Hanna; Verdel, Arie; Paap, Bob; Árni Guðnason, Egill; Páll Hersir, Gylfi; Jousset, Philippe; Sigurðsson, Ómar

    2016-04-01

    We report on the results obtained from a dense seismic deployment over a geothermal reservoir. The reservoir has been producing continuously for almost a decade and is located on the tip of the Reykjanes peninsula, SW Iceland. The seismic stations on top of the reservoir have continuously recorded the ambient seismic wavefield between April 2014 and September 2015. The density of the seismic network makes the data well suited for time-lapse seismic imaging of the reservoir. To that end we compute time-lapse responses through the application of seismic interferometry. These interferometric lapse responses are obtained by simple crosscorrelation of the seismic noise recorded by the different seismic stations. We subsequently evaluate the temporal variation of the coda of these crosscorrelations. The term coda refers to the later arriving, multiple scattered waves. The multiple scattering implies that these waves have sampled the subsurface very densely and hence become highly sensitive to tiny mechanical and structural changes in that subsurface. This sensitivity allows one, in principle at least, to monitor the geothermal reservoir. Preliminary results indeed suggest a relation between the temporal variation of the coda waves and the reservoir. Ultimately, this method may lead to a means to monitor a geothermal reservoir in both space and time.

  5. First Quarter Hanford Seismic Report for Fiscal Year 2011

    SciTech Connect

    Rohay, Alan C.; Sweeney, Mark D.; Clayton, Ray E.; Devary, Joseph L.

    2011-03-31

    The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The HSAP is responsible for locating and identifying sources of seismic activity and monitoring changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the HSAP works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 44 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. The Hanford Seismic Network recorded 16 local earthquakes during the first quarter of FY 2011. Six earthquakes were located at shallow depths (less than 4 km), seven earthquakes at intermediate depths (between 4 and 9 km), most likely in the pre-basalt sediments, and three earthquakes were located at depths greater than 9 km, within the basement. Geographically, thirteen earthquakes were located in known swarm areas and three earthquakes were classified as random events. The highest magnitude event (1.8 Mc) was recorded on October 19, 2010 at depth 17.5 km with epicenter located near the Yakima River between the Rattlesnake Mountain and Horse Heaven Hills swarm areas.

  6. First Quarter Hanford Seismic Report for Fiscal Year 2008

    SciTech Connect

    Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E.; Devary, Joseph L.

    2008-03-21

    The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The Hanford Seismic Assessment Team locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 41 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. For the Hanford Seismic Network, forty-four local earthquakes were recorded during the first quarter of fiscal year 2008. A total of thirty-one micro earthquakes were recorded within the Rattlesnake Mountain swarm area at depths in the 5-8 km range, most likely within the pre-basalt sediments. The largest event recorded by the network during the first quarter (November 25, 2007 - magnitude 1.5 Mc) was located within this swarm area at a depth of 4.3 km. With regard to the depth distribution, three earthquakes occurred at shallow depths (less than 4 km, most likely in the Columbia River basalts), thirty-six earthquakes at intermediate depths (between 4 and 9 km, most likely in the pre-basalt sediments), and five earthquakes were located at depths greater than 9 km, within the crystalline basement. Geographically, thirty-eight earthquakes occurred in swarm areas and six earth¬quakes were classified as random events.

  7. Background noise model development for seismic stations of KMA

    NASA Astrophysics Data System (ADS)

    Jeon, Youngsoo

    2010-05-01

    The background noise recorded at seismometer is exist at any seismic signal due to the natural phenomena of the medium which the signal passed through. Reducing the seismic noise is very important to improve the data quality in seismic studies. But, the most important aspect of reducing seismic noise is to find the appropriate place before installing the seismometer. For this reason, NIMR(National Institution of Meteorological Researches) starts to develop a model of standard background noise for the broadband seismic stations of the KMA(Korea Meteorological Administration) using a continuous data set obtained from 13 broadband stations during the period of 2007 and 2008. We also developed the model using short period seismic data from 10 stations at the year of 2009. The method of Mcmara and Buland(2004) is applied to analyse background noise of Korean Peninsula. The fact that borehole seismometer records show low noise level at frequency range greater than 1 Hz compared with that of records at the surface indicate that the cultural noise of inland Korean Peninsula should be considered to process the seismic data set. Reducing Double Frequency peak also should be regarded because the Korean Peninsula surrounded by the seas from eastern, western and southern part. The development of KMA background model shows that the Peterson model(1993) is not applicable to fit the background noise signal generated from Korean Peninsula.

  8. Application of the Neo-Deterministic Seismic Microzonation Procedure in Bulgaria and Validation of the Seismic Input Against Eurocode 8

    SciTech Connect

    Ivanka, Paskaleva; Mihaela, Kouteva; Franco, Vaccari; Panza, Giuliano F.

    2008-07-08

    The earthquake record and the Code for design and construction in seismic regions in Bulgaria have shown that the territory of the Republic of Bulgaria is exposed to a high seismic risk due to local shallow and regional strong intermediate-depth seismic sources. The available strong motion database is quite limited, and therefore not representative at all of the real hazard. The application of the neo-deterministic seismic hazard assessment procedure for two main Bulgarian cities has been capable to supply a significant database of synthetic strong motions for the target sites, applicable for earthquake engineering purposes. The main advantage of the applied deterministic procedure is the possibility to take simultaneously and correctly into consideration the contribution to the earthquake ground motion at the target sites of the seismic source and of the seismic wave propagation in the crossed media. We discuss in this study the result of some recent applications of the neo-deterministic seismic microzonation procedure to the cities of Sofia and Russe. The validation of the theoretically modeled seismic input against Eurocode 8 and the few available records at these sites is discussed.

  9. Seismic Forecasting of Eruptions at Dormant StratoVolcanoes

    NASA Astrophysics Data System (ADS)

    White, R. A.

    2015-12-01

    Seismic monitoring data provide important constraints on tracking magmatic ascent and eruption. Based on direct experience with over 25 and review of over 10 additional eruption sequences at 24 volcanoes, we have identified 4 phases of precursory seismicity. 1) Deep (>20 km) low frequency (DLF) earthquakes occur near the base of the crust as magma rises toward crustal reservoirs. This seismicity is the most difficult to observe, owing to generally small magnitudes (M<2.5) the significant depth. 2) Distal volcano-tectonic (DVT) earthquakes occur on tectonic faults from a 2 to 30+ km distance laterally from (not beneath) the eventual eruption site as magma intrudes into and rises out of upper crustal reservoirs to depths of 2-3 km. A survey of 111 eruptions of 83 previously dormant volcanoes, (including all eruptions of VEI >4 since 1955) shows they were all preceded by significant DVT seismicity, usually felt. This DVT seismicity is easily observed owing to magnitudes generally reaching M>3.5. The cumulative DVT energy correlates to the intruding magma volume. 3) Low frequency (LF) earthquakes, LF tremor and contained explosions occur as magma interacts with the shallow hydrothermal system (<2 km depth), while the distal seismicity dies off.4) Shortly after this, repetitive self-similar proximal seismicity may occur and may dominate the seismic records as magma rises to the surface. We present some examples of this seismic progression to demonstrate that data from a single short-period vertical station are often sufficient to forecast eruption onsets.

  10. Separation of site effects and structural focusing in Santa Monica, California: A study of high-frequency weak motions from earthquakes and blasts recorded during the Los Angeles Region Seismic Experiment

    USGS Publications Warehouse

    Baher, S.; Davis, P.M.; Fuis, G.

    2002-01-01

    Near-surface site factors and the effects of deep structural focusing were estimated in the Santa Monica Mountains and Santa Monica, California, from a portable array of 75 seismic stations deployed during the Los Angeles Region Seismic Experiment, Phase II (LARSE II). The objective was to examine further the origin of seismic wave amplification in the region of intense damage south of the Santa Monica Fault from the Northridge earthquake. The analysis used normalized spectral amplitudes in the 4- to 8- and 8- to 12-Hz range in direct and coda waves from local earthquakes in Santa Paula, Northridge, Redlands, and Hector Mine. Coda waves indicated that site factor amplifications are larger south of the Santa Monica fault relative to the north. Spectral ratios of direct S waves, corrected for site effects, show additional amplificaton south of, and adjacent to, the Santa Monica fault, attributable to focusing by a deeper structure. Gao et al. (1996) concluded that localized focusing effects contributed to anomalous P- and S-wave amplification in the Santa Monica damage zone for Northridge aftershocks within a specified range of azimuths. In an attempt to reproduce the hypothesized focusing from the Northridge earthquake, two shots (4000 and 3750 lb.) were detonated, one at Pyramid Lake, a distance of about 69 km to the north-northwest of central Santa Monica, and the other near Fort Tejon, a distance of 91 km. The azimuth of the shots was chosen to be that expected to give anomalous amplification. At these distance steeply incident seismic energy from Pg/PmP waves are expected to pass through the underground focusing structure and be selectively amplified. After the local site factors are removed, the waveforms from the Fort Tejon shot exhibited localized amplification adjacent to and south of the fault, 2-3 times larger than that of the surrounding area. The effect is less for waves from the Pyramid Lake shot, which could be due to their higher angle of incidence

  11. The seismic noise wavefield is not diffuse.

    PubMed

    Mulargia, Francesco

    2012-04-01

    Passive seismology is burgeoning under the apparent theoretical support of diffuse acoustics. However, basic physical arguments suggest that this theory may not be applicable to seismic noise. A procedure is developed to establish the applicability of the diffuse field paradigm to a wavefield, based on testing the latter for azimuthal isotropy and spatial homogeneity. This procedure is then applied to the seismic noise recorded at 65 sites covering a wide variety of environmental and subsoil conditions. Considering the instantaneous oscillation vector measured at single triaxial stations, the hypothesis of azimuthal isotropy is rejected in all cases with high confidence, which makes the spatial homogeneity test unnecessary and leads directly to conclude that the seismic noise wavefield is not diffuse. However, such a conclusion has no practical effect on passive imaging, which is also possible in non-diffuse wavefields. PMID:22501063

  12. Intraplate seismicity across the Cape Verde swell: A contribution from a temporary seismic network

    NASA Astrophysics Data System (ADS)

    Vales, Dina; Dias, Nuno A.; Rio, Inês; Matias, Luís; Silveira, Graça; Madeira, José; Weber, Michael; Carrilho, Fernando; Haberland, Christian

    2014-12-01

    We present an analysis and characterization of the regional seismicity recorded by a temporary broadband seismic network deployed in the Cape Verde archipelago between November 2007 and September 2008. The detection of earthquakes was based on spectrograms, allowing the discrimination from low-frequency volcanic signals, resulting in 358 events of which 265 were located, the magnitudes usually being smaller than 3. For the location, a new 1-D P-velocity model was derived for the region showing a crust consistent with an oceanic crustal structure. The seismicity is located mostly offshore the westernmost and geologically youngest areas of the archipelago, near the islands of Santo Antão and São Vicente in the NW and Brava and Fogo in the SW. The SW cluster has a lower occurrence rate and corresponds to seismicity concentrated mainly along an alignment between Brava and the Cadamosto seamount presenting normal faulting mechanisms. The existence of the NW cluster, located offshore SW of Santo Antão, was so far unknown and concentrates around a recently recognized submarine cone field; this cluster presents focal depths extending from the crust to the upper mantle and suggests volcanic unrest. No evident temporal behaviour could be perceived, although the events tend to occur in bursts of activity lasting a few days. In this recording period, no significant activity was detected at Fogo volcano, the most active volcanic edifice in Cape Verde. The seismicity characteristics point mainly to a volcanic origin. The correlation of the recorded seismicity with active volcanic structures agrees with the tendency for a westward migration of volcanic activity in the archipelago as indicated by the geologic record.

  13. Seismic Computerized Alert Network

    USGS Publications Warehouse

    1986-01-01

    In 1985 the USGS devised a model for a Seismic Computerized Alert Network (SCAN) that would use continuous monitoring of seismic data from existing types of instruments to provide automatic, highly-reliable early warnings of earthquake shaking. In a large earthquake, substantial damaging ground motions may occur at great distances from the earthquake's epicenter.

  14. Regional variations in seismic boundaries

    NASA Astrophysics Data System (ADS)

    Shumlyanska, Ludmila

    2010-05-01

    Dividing of the Earth into zones in the frame one-dimensional velocity model was proposed Jeffreys and Gutenberg is the first half of XX century. They recovered the following zones: A - the crust; B - zone in the depth interval 33-413 km, C - zone 413-984 km, D - zone 984-2898 km, E - 2898-4982 km, F - 4982-5121 km, G - 5121-6371 km (centre of the Earth). These zones differ in their seismic properties. Later, zone D was divided to the areas D' (984-2700 km) and D" (2700-2900 km). At present, this scheme is significantly modified and only the layer D" is in wide use. The more seismological studies are carried out, the more seismic boundaries appear. Boundaries at 410, 520, 670, and 2900 km, at which increase in the velocity of the seismic waves is particularly noticeable are considered as having global significance. Moreover, there are indications of the existence of geophysical boundaries at 800, 1200-1300, 1700, 1900-2000 km. Using 3D P-velocity model of the mantle based on Taylor approximation method for solving of the inverse kinematics multi-dimensional seismic task we have obtained seismic boundaries for the area covering 20-55° E × 40-55° N. Data on the time of first arrivals of P waves from earthquakes and nuclear explosions recorded at ISC stations during 1964-2002 were used as input to construct a 3-D model. The model has two a priori limits: 1) the velocity is a continuous function of spatial coordinates, 2) the function v(r)/r where r is a radius in the spherical coordinate system r, φ, λ decreases with depth. The first limitation is forced since velocity leaps can not be sustainably restored from the times of first arrival; the second one follows from the nature of the observed data. Results presented as horizontal sections of the actual velocity every 25 km in the depth interval 850-2850 km, and as the longitudinal and latitudinal sections of the discrepancy on the 1-D reference model, obtained as a result of solving of the inversion task at 1

  15. Seismic Imaging of Open Subsurface Fractures

    NASA Astrophysics Data System (ADS)

    Myers, S. C.; Pitarka, A.; Matzel, E.; Aguiar, A. C.

    2015-12-01

    Injection of high-pressure fluid into the subsurface is proven to stimulate geothermal, oil, and gas production by opening cracks that increase permeability. The effectiveness of increasing permeability by high-pressure injection has been revolutionized by the introduction of "proppants" into the injected fluid to keep cracks open after the pressure of the stimulation activity ends. The network of fractures produced during stimulation is most commonly inferred by the location of micro-earthquakes. However, existing (closed) fractures may open aseismically, so the whole fracture network may not be imaged by micro-seismic locations alone. Further, whether all new fractures remain open and for how long remains unclear. Open cracks, even fluid-filled cracks, scatter seismic waves because traction forces are not transmitted across the gap. Numerical simulation confirms that an open crack with dimensions on the order of 10 meters can scatter enough seismic energy to change the coda of seismic signals. Our simulations show that changes in seismic coda due to newly opened fractures are only a few percent of peak seismogram amplitudes, making signals from open cracks difficult to identify. We are developing advanced signal processing methods to identify candidate signals that originate from open cracks. These methods are based on differencing seismograms that are recorded before and after high-pressure fluid injection events to identify changes in the coda. The origins of candidate signals are located using time-reversal techniques to determine if the signals are indeed associated with a coherent structure. The source of scattered energy is compared to micro-seismic event locations to determine whether cracks opened seismically or aseismically. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675612.

  16. Astor Pass Seismic Surveys Preliminary Report

    SciTech Connect

    Louie, John; Pullammanappallil, Satish; Faulds, James; Eisses, Amy; Kell, Annie; Frary, Roxanna; Kent, Graham

    2011-08-05

    In collaboration with the Pyramid Lake Paiute Tribe (PLPT), the University of Nevada, Reno (UNR) and Optim re-processed, or collected and processed, over 24 miles of 2d seismic-reflection data near the northwest corner of Pyramid Lake, Nevada. The network of 2d land surveys achieved a near-3d density at the Astor Pass geothermal prospect that the PLPT drilled during Nov. 2010 to Feb. 2011. The Bureau of Indian Affairs funded additional seismic work around the Lake, and an extensive, detailed single-channel marine survey producing more than 300 miles of section, imaging more than 120 ft below the Lake bottom. Optim’s land data collection utilized multiple heavy vibrators and recorded over 200 channels live, providing a state-of-the-art reflection-refraction data set. After advanced seismic analysis including first-arrival velocity optimization and prestack depth migration, the 2d sections show clear fault-plane reflections, in some areas as deep as 4000 ft, tying to distinct terminations of the mostly volcanic stratigraphy. Some lines achieved velocity control to 3000 ft depth; all lines show reflections and terminations to 5000 ft depth. Three separate sets of normal faults appear in an initial interpretation of fault reflections and stratigraphic terminations, after loading the data into the OpendTect 3d seismic visualization system. Each preliminary fault set includes a continuous trace more than 3000 ft long, and a swarm of short fault strands. The three preliminary normal-fault sets strike northerly with westward dip, northwesterly with northeast dip, and easterly with north dip. An intersection of all three fault systems documented in the seismic sections at the end of Phase I helped to locate the APS-2 and APS-3 slimholes. The seismic sections do not show the faults connected to the Astor Pass tufa spire, suggesting that we have imaged mostly Tertiary-aged faults. We hypothesize that the Recent, active faults that produced the tufa through hotspring

  17. Seismicity anomalies of the 2003 Bam, Iran earthquake

    NASA Astrophysics Data System (ADS)

    Ashtari Jafari, Mohammad

    2012-08-01

    The Bam earthquake occurred in an area without any historically recorded major earthquake. Based on active tectonics and CMT solutions the area is under the influence of shortening and right-lateral strike-slip faulting. Seismicity is of a shallow crustal type which is mainly distributed within the Koohbanan-Golbaf, Lakarkooh-Shahdad-Gowk fault systems and the terminal sections of Zagros. In order to detect temporal seismicity anomalies before this earthquake we compiled a catalog from the ISC events and then analyzed it for the magnitude of completeness. After declustering this catalog, changes in seismicity were assessed by the z-value test. The temporal variations indicate a relative decrease in z-value before the Bam earthquake. Additional to seismic quiescence and decrease in b-value before the main shock there are pieces of evidence corresponding to increase in triggered background seismicity after this earthquake.

  18. 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.

  19. Propagation of seismic waves in tall buildings

    USGS Publications Warehouse

    Safak, E.

    1998-01-01

    A discrete-time wave propagation formulation of the seismic response of tall buildings is introduced. The building is modeled as a layered medium, similar to a layered soil medium, and is subjected to vertically propagating seismic shear waves. Soil layers and the bedrock under the foundation are incorporated in the formulation as additional layers. Seismic response is expressed in terms of the wave travel times between the layers, and the wave reflection and transmission coefficients at the layer interfaces. The equations account for the frequency-dependent filtering effects of the foundation and floor masses. The calculation of seismic response is reduced to a pair of simple finite-difference equations for each layer, which can be solved recursively starting from the bedrock. Compared to the commonly used vibration formulation, the wave propagation formulation provides several advantages, including simplified calculations, better representation of damping, ability to account for the effects of the soil layers under the foundation, and better tools for identification and damage detection from seismic records. Examples presented show the versatility of the method. ?? 1998 John Wiley & Sons, Ltd.

  20. Improved characterization of local seismicity using the Dubai Seismic Network, United Arab Emirates

    NASA Astrophysics Data System (ADS)

    Al Khatibi, Eman; Abou Elenean, K. M.; Megahed, A. S.; El-Hussain, I.

    2014-08-01

    In April 2006, Dubai Municipality established a broadband seismological network in Dubai Emirate, United Arab Emirates (UAE). This network was the first seismic network in UAE and consists of four remote seismic stations to observe local and regional seismic activity that may have an effect on Dubai Emirate and the surrounding areas. The network exchanges real-time data with the National Center of Meteorology and Seismology in Abu Dhabi, the Earthquake Monitoring Center in Oman and imports in real-time data from few Global Seismic Network stations, which increases the aperture of the network. In April 2012, Dubai Municipality installed an additional five free-field strong motion stations inside the urban area to estimate and publish real-time ShakeMaps for public and decision makers. Although the local seismic activity from April 2006 to June 2013 reflects low seismic activity with the Emirate, it indicates active tectonics in the relatively aseismic northern Oman Mountains region. A few inland clusters of micro-to-small earthquakes have been identified with the new network. A clear cluster of small-to-moderate earthquakes took place in the eastern part of UAE to the east of Masafi, while two clusters of micro-to-small earthquakes took place at Wadi Nazwa and northern Huwaylat. Focal mechanisms of few well recorded earthquakes in this region indicate normal faulting, generally trending NE in parallel to the transition shear zone between the collision at Zagros and the subduction at the Makran zone.

  1. Bighorns Arch Seismic Experiment (BASE): Amplitude Response to Different Seismic Charge Configurations

    SciTech Connect

    Harder, S. H., Killer, K. C., Worthington, L. L., Snelson, C. M.

    2010-09-02

    Contrary to popular belief, charge weight is not the most important engineering parameter determining the seismic amplitudes generated by a shot. The scientific literature has long claimed that the relationship, A ~R2L1/2, where A is the seismic amplitude generated by a shot, R is the radius of the seismic charge and L is the length of that charge, holds. Assuming the coupling to the formation and the pressure generated by the explosive are constants, this relationship implies that the one should be able to increase the charge radius while decreasing the charge length and obtain more seismic amplitude with less charge weight. This has significant implications for the economics of lithospheric seismic shots, because shallower holes and small charge sizes decrease cost. During the Bighorns Array Seismic Experiment (BASE) conducted in the summer of 2010, 24 shots with charge sizes ranging from 110 to 900 kg and drill hole diameters of 300 and 450 mm were detonated and recorded by an array of up to 2000 single-channel Texan seismographs. Maximum source-receiver offset of 300 km. Five of these shots were located within a one-acre square in an effort to eliminate coupling effects due to differing geological formations. We present a quantitative comparison of the data from these five shots to experimentally test the equation above.

  2. Two applications of time reversal mirrors: seismic radio and seismic radar.

    PubMed

    Hanafy, Sherif M; Schuster, Gerard T

    2011-10-01

    Two seismic applications of time reversal mirrors (TRMs) are introduced and tested with field experiments. The first one is sending, receiving, and decoding coded messages similar to a radio except seismic waves are used. The second one is, similar to radar surveillance, detecting and tracking a moving object(s) in a remote area, including the determination of the objects speed of movement. Both applications require the prior recording of calibration Green's functions in the area of interest. This reference Green's function will be used as a codebook to decrypt the coded message in the first application and as a moving sensor for the second application. Field tests show that seismic radar can detect the moving coordinates (x(t), y(t), z(t)) of a person running through a calibration site. This information also allows for a calculation of his velocity as a function of location. Results with the seismic radio are successful in seismically detecting and decoding coded pulses produced by a hammer. Both seismic radio and radar are highly robust to signals in high noise environments due to the super-stacking property of TRMs. PMID:21973353

  3. Seismic damage to pipeline; Case study

    SciTech Connect

    O'Rourke, M.J.; Ayala, G. . Dept. of Civil Engineering)

    1990-03-01

    A case study of damage to a welded steel pipeline in Mexico City, caused by the 1985 Michoacan earthquake, is presented. Seismic damage to pipelines in past earthquakes is briefly reviewed. The damage has typically been due to seismic wave propagation or permanent ground deformations, such as faulting, landslides, or lateral spreads. Physical characteristics of the case study pipeline, pertinent soil conditions, recorded ground motion, and observed seismic damage in Mexico City are then presented. The recorded ground motion in the lake zone of Mexico City suggests a significant contribution from Rayleigh waves. A previously developed analysis procedure is used to estimate stress induced by seismic wave propagation in the case study pipeline. The pipeline stress is a function of the amplitude and wavelength of the ground strain, maximum friction forces at the soil-pipe interface, and the stress-strain characteristics of the pipeline material. It is shown that the estimated stress is only slightly less than the local compressional buckling stress for the case history pipeline.

  4. Seismically observed seiching in the Panama Canal

    NASA Astrophysics Data System (ADS)

    McNamara, D. E.; Ringler, A. T.; Hutt, C. R.; Gee, L. S.

    2011-04-01

    A large portion of the seismic noise spectrum is dominated by water wave energy coupled into the solid Earth. Distinct mechanisms of water wave induced ground motions are distinguished by their spectral content. For example, cultural noise is generally <1 s period, microseisms dominate the seismic spectrum from periods of 2 to 20 s, and the Earth's "hum" is in the range of 50 to 600 s. We show that in a large lake in the Panama Canal there is an additional source of long-period noise generated by standing water waves, seiches, induced by disturbances such as passing ships and wind pressure. We compare seismic waveforms to water level records and relate these observations to changes in local tilt and gravity due to an oscillating seiche. The methods and observations discussed in this paper provide a first step toward quantifying the impact of water inundation as recorded by seismometers. This type of quantified understanding of water inundation will help in future estimates of similar phenomena such as the seismic observations of tsunami impact.

  5. Seismically observed seiching in the Panama Canal

    USGS Publications Warehouse

    McNamara, D.E.; Ringler, A.T.; Hutt, C.R.; Gee, L.S.

    2011-01-01

    A large portion of the seismic noise spectrum is dominated by water wave energy coupled into the solid Earth. Distinct mechanisms of water wave induced ground motions are distinguished by their spectral content. For example, cultural noise is generally <1 s period, microseisms dominate the seismic spectrum from periods of 2 to 20 s, and the Earth's "hum" is in the range of 50 to 600 s. We show that in a large lake in the Panama Canal there is an additional source of long-period noise generated by standing water waves, seiches, induced by disturbances such as passing ships and wind pressure. We compare seismic waveforms to water level records and relate these observations to changes in local tilt and gravity due to an oscillating seiche. The methods and observations discussed in this paper provide a first step toward quantifying the impact of water inundation as recorded by seismometers. This type of quantified understanding of water inundation will help in future estimates of similar phenomena such as the seismic observations of tsunami impact. Copyright 2011 by the American Geophysical Union.

  6. Second Quarter Hanford Seismic Report for Fiscal Year 2008

    SciTech Connect

    Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E.; Devary, Joseph L.

    2008-06-26

    The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The Hanford Seismic Assessment Team locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 44 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. For the Hanford Seismic Network, seven local earthquakes were recorded during the second quarter of fiscal year 2008. The largest event recorded by the network during the second quarter (February 3, 2008 - magnitude 2.3 Mc) was located northeast of Richland in Franklin County at a depth of 22.5 km. With regard to the depth distribution, two earthquakes occurred at shallow depths (less than 4 km, most likely in the Columbia River basalts), three earthquakes at intermediate depths (between 4 and 9 km, most likely in the pre-basalt sediments), and two earthquakes were located at depths greater than 9 km, within the crystalline basement. Geographically, five earthquakes occurred in swarm areas and two earthquakes were classified as random events.

  7. Second Quarter Hanford Seismic Report for Fiscal Year 2000

    SciTech Connect

    DC Hartshorn; SP Reidel; AC Rohay

    2000-07-17

    Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the US Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (EWRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EWRN uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 506 triggers on two parallel detection and recording systems during the second quarter of fiscal year (FY) 2000. Twenty-seven seismic events were located by the Hanford Seismic Network within the reporting region of 46--47{degree} N latitude and 119--120{degree} W longitude; 12 were earthquakes in the Columbia River Basalt Group, 2 were earthquakes in the pre-basalt sediments, 9 were earthquakes in the crystalline basement, and 5 were quarry blasts. Three earthquakes appear to be related to geologic structures, eleven earthquakes occurred in known swarm areas, and seven earthquakes were random occurrences. No earthquakes triggered the Hanford Strong Motion

  8. Third Quarter Hanford Seismic Report for Fiscal Year 2000

    SciTech Connect

    DC Hartshorn; SP Reidel; AC Rohay

    2000-09-01

    Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the U.S. Department of Energy and its con-tractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (E WRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EWRN uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 818 triggers on two parallel detection and recording systems during the third quarter of fiscal year (FY) 2000. Thirteen seismic events were located by the Hanford Seismic Network within the reporting region of 46-47{degree} N latitude and 119-120{degree} W longitude; 7 were earthquakes in the Columbia River Basalt Group, 1 was an earthquake in the pre-basalt sediments, and 5 were earthquakes in the crystalline basement. Three earthquakes occurred in known swarm areas, and 10 earthquakes were random occurrences. No earthquakes triggered the Hanford Strong Motion Accelerometers during the third quarter of FY 2000.

  9. First quarter Hanford seismic report for fiscal year 2000

    SciTech Connect

    DC Hartshorn; SP Reidel; AC Rohay

    2000-02-23

    Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the US Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (EWRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EW uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 311 triggers on two parallel detection and recording systems during the first quarter of fiscal year (FY) 2000. Twelve seismic events were located by the Hanford Seismic Network within the reporting region of 46--47{degree}N latitude and 119--120{degree}W longitude; 2 were earthquakes in the Columbia River Basalt Group, 3 were earthquakes in the pre-basalt sediments, 9 were earthquakes in the crystalline basement, and 1 was a quarry blast. Two earthquakes appear to be related to a major geologic structure, no earthquakes occurred in known swarm areas, and 9 earthquakes were random occurrences. No earthquakes triggered the Hanford Strong Motion Accelerometers

  10. Second Quarter Hanford Seismic Report for Fiscal Year 2000

    SciTech Connect

    Hartshorn, Donald C.; Reidel, Stephen P.; Rohay, Alan C.

    2000-07-17

    Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the U.S. Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (EWRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EWRN uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 506 triggers on two parallel detection and recording systems during the second quarter of fiscal year (FY) 2000. Twenty-seven seismic events were located by the Hanford Seismic Network within the reporting region of 46-47 N latitude and 119-120 W longitude; 12 were earthquakes in the Columbia River Basalt Group, 2 were earthquakes in the pre-basalt sediments, 9 were earthquakes in the crystalline basement, and 5 were quarry blasts. Three earthquakes appear to be related to geologic structures, eleven earthquakes occurred in known swarm areas, and seven earthquakes were random occurrences.

  11. 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.

  12. 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.

  13. 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.

  14. Seismic data from man-made impacts on the moon.

    PubMed

    Latham, G; Ewing, M; Dorman, J; Press, F; Toksoz, N; Sutton, G; Meissner, R; Duennebier, F; Nakamura, Y; Kovach, R; Yates, M

    1970-11-01

    Unusually long reverberations were recorded from two lunar impacts by a seismic station installed on the lunar surface by the Apollo 12 astronauts. Seismic data from these impacts suggest that the lunar mare in the region of the Apollo 12 landing site consists of material with very low seismic velocities near the surface, with velocity increasing with depth to 5 to 6 kilometers per second (for compressional waves) at a depth of 20 kilometers. Absorption of seismic waves in this structure is extremely low relative to typical continental crustal materials on earth. It is unlikely that a major boundary similar to the crustmantle interface on earth exists in the outer 20 kilometers of the moon. A combination of dispersion and scattering of surface waves probably explains the lunar seismic reverberation. Scattering of these waves implies the presence of heterogeneity within the outer zone of the mare on a scale of from several hundred meters (or less) to several kilometers. Seismic signals from 160 events of natural origin have been recorded during the first 7 months of operation of the Apollo 12 seismic station. At least 26 of the natural events are small moonquakes. Many of the natural events are thought to be meteoroid impacts. PMID:17799298

  15. Radiative transfer theory for estimation of the seismic moment

    NASA Astrophysics Data System (ADS)

    Sens-Schönfelder, C.; Wegler, U.

    2006-12-01

    We propose a new technique to obtain source spectra and seismic moments of regional earthquakes from envelopes of seismic coda. As compared to existing methods, our approach is based on a physical model of the scattering process that produces the seismic coda. This allows the direct estimation of source parameters, without the necessity to fix proportionality coefficients with reference events. We see an appreciable advantage because the method is independent of the output from other techniques, such as reference events provided by moment inversions. The main component of our method is a joint inversion of the seismic records for source and site parameters, as well as for medium parameters assuming isotropic sources and isotropic, acoustic scattering in a half-space. The method is tested with recordings of 11 earthquakes (4 <= Ml <= 6) by the German Regional Seismic Network at epicentral distances less than 1000 km. We invert the traces in eight frequency bands between 0.2 and 24 Hz and demonstrate that our estimates of the seismic moment are in good agreement with values obtained in independent studies using waveform inversion techniques. In fact our estimates of the seismic moment are better than approximations obtained from local magnitudes using empirical relations specifically derived for the region under study. The parameters that describe the scattering medium are mean free path that we found to average around 690 km and the intrinsic quality factor for which we obtain IQ = 500 below 3 Hz.

  16. Joint analysis of the seismic data and velocity gravity model

    NASA Astrophysics Data System (ADS)

    Belyakov, A. S.; Lavrov, V. S.; Muchamedov, V. A.; Nikolaev, A. V.

    2016-03-01

    We performed joint analysis of the seismic noises recorded at the Japanese Ogasawara station located on Titijima Island in the Philippine Sea using the STS-2 seismograph at the OSW station in the winter period of January 1-15, 2015, over the background of a velocity gravity model. The graphs prove the existence of a cause-and-effect relation between the seismic noise and gravity and allow us to consider it as a desired signal.

  17. Seismic Moment Tensor Report for the 06 Aug 2007, M3.9 Seismic Event in Central Utah

    SciTech Connect

    Ford, S R; Dreger, D S; Walter, W R; Hellweg, M; Urhammer, R

    2007-08-15

    We have performed a complete moment tensor analysis (Minson and Dreger, 2007) of the seismic event, which occurred on Monday August 6, 2007 at 08:48:40 UTC, 21 km from Mount Pleasant, Utah. The purpose of this report is to present our scientific results, making them available to other researchers working on seismic source determination problems, and source type identification. In our analysis we used complete, three-component seismic records recorded by stations operated by the USGS, the University of Utah and EarthScope. The results of our analysis show that most of the seismic wave energy is consistent with an underground collapse, however the cause of the mine collapse is still unknown.

  18. Seismic monitoring of Central Asia territory in KNDC.

    NASA Astrophysics Data System (ADS)

    Mukambayev, Aidyn; Mikhailova, Natalia

    2015-04-01

    The Central Asia territory includes the territory of five post-Soviet countries: Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. Every country has its own independent network of seismic observations and Data Processing Center aimed at every day seismic monitoring of one country territory. However, seismic hazard of Central Asia territory is stipulated by one geodynamic system that generates simultaneous large earthquakes on the territory of different countries. Thus, it is necessary to observe seismic situation for the whole region for emergency situations and for compilation of joint seismic bulletins of Central Asia region. A new contemporary network of seismic observations operated by the Institute of Geophysical Researches has been installed in Kazakhstan during last 15 years. Mainly, these are seismic arrays located throughout the country perimeter. The arrays were constructed under support of the CTBTO, and AFTAC. There are also IRIS and CAREMON stations. All data arrive to KNDC (Kazakhstan National Data Center) in real time mode. In addition, KNDC receives data in real time from stations Zalesovo (Russia), Alibek (Turkmenistan), Ala-Archa and Tokmak (Kyrgyzstan). Arrival times in the form of tables are received with 24-hours delay from almost 20 Kazakhstan stations belonging to SEME MES RK. This observation system allows monitoring the Central Asian seismicity by earthquakes with representative magnitude more than 3.5. In some regions, the events with magnitude 1.5 are recorded. As result, different products with different operativity are created for Central Asia territory: -bulletin of urgent alerts; -automatic seismic bulletin; -interactive seismic bulletin; -joint seismic operative bulletin by data arrived on-line and in table form. After that, in retrospective mode, the events nature is identified to discriminate mining explosions (up to 4000 per year) and natural earthquakes (up to 15000 per year). The results are available at KNDC web

  19. Seismic Techniques for Subsurface Voids Detection

    NASA Astrophysics Data System (ADS)

    Gritto, Roland; Korneev, Valeri; Elobaid Elnaiem, Ali; Mohamed, Fathelrahman; Sadooni, Fadhil

    2016-04-01

    orthogonal transmission surveys to detect and locate the object. Furthermore, we showed that ambient noise recordings may generate data with sufficient signal-to-noise ratio to successfully detect and locate subsurface voids. Being able to use ambient noise recordings would eliminate the need to employ active seismic sources that are time consuming and more expensive to operate.

  20. Development of a wireless seismic array for volcano monitoring

    NASA Astrophysics Data System (ADS)

    Moure, David; Toma, Daniel; Lázaro, Antoni Manuel; Del Río, Joaquín; Carreras, Normandino; José Blanco, María

    2014-05-01

    Volcano monitoring is mainly based on three sciences: seismology, geodesy and geochemistry. Seismic arrays are used to locate the seismic source, based on analysis of signals recorded by each seismometer. The most important advantages of arrays over classical seismic networks are: painless deployment, no major infrastructures needed, able to provide an approximate location of a signal that is not feasible by a seismic network. In this paper the design of a low-power wireless array is presented. All sensors transmit acquired data to a central node which is capable to calculate the possible location of the seismic source in real-time. The reliability of those locations depends, among other parameters (number of sensors and geometrical distribution), on precision of time synchronization between the nodes. To achieve the necessary precision, the wireless seismic array implements a time synchronization protocol based on the IEEE1588 protocol, which ensures clock synchronization between nodes better than a microsecond, therefore, signal correlation between sensors is achieved correlating the signals from all the sensors. The ultimate challenge would be that the central node receives data from all the seismometers locating the seismic source, only transmitting the result, which dramatically reduces data traffic. Often, active volcano areas are located far from inhabited areas and data transmission options are limited. In situ calculation is crucial in order to reduce data volume transmission generated by the seismic array.

  1. Local seismic effects in Swedish underground mines (Zinkgruvan, Garpenberg, Kiruna)

    NASA Astrophysics Data System (ADS)

    Dineva, Savka; Mihaylov, Dimitar; Hansen-Haug, Jouni; Woldemehdin, BIruk; Marklund, Per-Ivar; Mozaffari, Shahram

    2016-04-01

    Three local seismic systems from Institute of Mine Seismology (IMS) were installed by August 2015 in deep underground mines in Sweden - Zinkgruvan Mine (Lundin Mining AB), Garpenberg Mine (Boliden Mines), and Kiirunavaara Mine (LKAB). The areas of installation are chosen within the volumes where large rockbursts are expected. One of the systems is deployed at depth around 700 m and the other two around 1100 m. The horizontal extent of the instrumented volumes is between 65 and 115 m. Each system consists of 16 to 18 sensors. A combination of uni-axial and three-axial 4.5 Hz geophones is installed on the wall and roof surfaces of the drifts, in shallow (~0.5 m) and deeper (6-9 m) boreholes. Extensometers and instrumented bolts are installed in close proximity to the profiles with seismic sensors. Data acquisition systems run mostly in triggered mode, with remote access to the data. Very small to larger seismic events (local magnitudes from ~ -4.5 to 2.0) are recorded during the time of operation. The aim of the seismic systems is to provide data about the seismic waveforms recorded as they approach the underground openings. Data is used to evaluate: 1) the site effect on the amplitudes, frequency content, and duration of the seismic signals, 2) the attenuation/amplification of the seismic waves. The seismic data is correlated with the records from the extensometers and instrumented bolts in case of larger seismic events, rockbursts, and blasting in the surrounding area. The final goal is to obtain new information for improvement of the requirements for the rock support in rockburst prone areas. The results show large variations of the amplitudes and frequencies of the recorded seismic waves within small distances, as well as between the walls and the roof. Data recorded by the local systems in the near-field are used for estimation of the attenuation and for comparison with the far-field attenuation derived from mine-wide data. Results are obtained also on the

  2. Development of Vertical Cable Seismic System

    NASA Astrophysics Data System (ADS)

    Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

    2011-12-01

    In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. (1) VCS is an efficient high-resolution 3D seismic survey in limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Because of autonomous recording system on sea floor, various types of marine source are applicable with VCS such as sea-surface source (GI gun etc.) , deep-towed or ocean bottom source. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN, in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. Seismic Interferometry technique is also applied. The results give much clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Seismic Interferometry technique is applied to obtain the high resolution image in the very shallow zone. Based on the feasibility study, we have developed the autonomous recording VCS system and carried out the trial experiment in actual ocean at the water depth of about 400m to establish the procedures of deployment/recovery and to examine the VC position or fluctuation at seabottom. The result shows that the VC position is estimated with sufficient accuracy and very little fluctuation is observed. Institute of Industrial Science, the University of Tokyo took the research cruise NT11-02 on JAMSTEC R/V Natsushima in February, 2011. In the cruise NT11-02, JGI carried out the second VCS survey using the autonomous VCS recording system with the deep towed source provided by

  3. Phase Statistics of Seismic Coda Waves

    SciTech Connect

    Anache-Menier, D.; Tiggelen, B. A. van; Margerin, L.

    2009-06-19

    We report the analysis of the statistics of the phase fluctuations in the coda of earthquakes recorded during a temporary experiment deployed at Pinyon Flats Observatory, California. The observed distributions of the spatial derivatives of the phase in the seismic coda exhibit universal power-law decays whose exponents agree accurately with circular Gaussian statistics. The correlation function of the phase derivative is measured and used to estimate the mean free path of Rayleigh waves.

  4. Phase statistics of seismic coda waves.

    PubMed

    Anache-Ménier, D; van Tiggelen, B A; Margerin, L

    2009-06-19

    We report the analysis of the statistics of the phase fluctuations in the coda of earthquakes recorded during a temporary experiment deployed at Pinyon Flats Observatory, California. The observed distributions of the spatial derivatives of the phase in the seismic coda exhibit universal power-law decays whose exponents agree accurately with circular Gaussian statistics. The correlation function of the phase derivative is measured and used to estimate the mean free path of Rayleigh waves. PMID:19659054

  5. Seismic sequences in the Sombrero Seismic Zone

    NASA Astrophysics Data System (ADS)

    Pulliam, J.; Huerfano, V. A.; ten Brink, U.; von Hillebrandt, C.

    2007-05-01

    The northeastern Caribbean, in the vicinity of Puerto Rico and the Virgin Islands, has a long and well-documented history of devastating earthquakes and tsunamis, including major events in 1670, 1787, 1867, 1916, 1918, and 1943. Recently, seismicity has been concentrated to the north and west of the British Virgin Islands, in the region referred to as the Sombrero Seismic Zone by the Puerto Rico Seismic Network (PRSN). In the combined seismicity catalog maintained by the PRSN, several hundred small to moderate magnitude events can be found in this region prior to 2006. However, beginning in 2006 and continuing to the present, the rate of seismicity in the Sombrero suddenly increased, and a new locus of activity developed to the east of the previous location. Accurate estimates of seismic hazard, and the tsunamigenic potential of seismic events, depend on an accurate and comprehensive understanding of how strain is being accommodated in this corner region. Are faults locked and accumulating strain for release in a major event? Or is strain being released via slip over a diffuse system of faults? A careful analysis of seismicity patterns in the Sombrero region has the potential to both identify faults and modes of failure, provided the aggregation scheme is tuned to properly identify related events. To this end, we experimented with a scheme to identify seismic sequences based on physical and temporal proximity, under the assumptions that (a) events occur on related fault systems as stress is refocused by immediately previous events and (b) such 'stress waves' die out with time, so that two events that occur on the same system within a relatively short time window can be said to have a similar 'trigger' in ways that two nearby events that occurred years apart cannot. Patterns that emerge from the identification, temporal sequence, and refined locations of such sequences of events carry information about stress accommodation that is obscured by large clouds of

  6. Seismicity of the eastern Hellenic Subduction Zone

    NASA Astrophysics Data System (ADS)

    Bruestle, A.; Kueperkoch, L.; Rische, M.; Meier, T.; Friederich, W.; Egelados Working Group

    2012-04-01

    The Hellenic Subduction Zone (HSZ) is the seismically most active region of Europe. The African plate is subducting beneath the Aegean lithosphere with a relative velocity of 4 cm per year. A detailed picture of the microseismicity of the eastern HSZ was obtained by the recordings of the temporary networks CYCNET (September 2002 - September 2005) and EGELADOS (October 2005 - March 2007). In total, nearly 7000 earthquakes were located with a location uncertainty of less than 20 km. The SE Aegean is dominated by (1) shallow intraplate seismicity within the Aegean plate, by (2) interplate seismicity at the plate contact and by (3) intermediate deep seismicity along the subducting African slab. Strong shallow seismicity in the upper plate is observed along the Ptolemy graben south of Crete extending towards the Karpathos Basin, indicating intense recent deformation of the forearc. In contrary, low shallow seismicity around Rhodes indicates only minor seismic crustal deformation of the upper plate. An almost NS-striking zone of microseismicity has been located, running from the Karpathos basin via the Nisyros volcanic complex towards the EW striking Gökova graben. In the SE Aegean the geometry of the Wadati-Benioff-Zone (WBZ) within the subducting African plate is revealed in detail by the observed microseismicity. Between about 50 to 100 km depth a continuous band of intermediate deep seismicity describes the strongly curved geometry of the slab. From the central to the eastern margin of the HSZ, the dip direction of the WBZ changes from N to NW with a strong increase of the dip angle beneath the eastern Cretan Sea. The margin of the dipping African slab is marked by an abrupt end of the observed WBZ beneath SW Anatolia. Below 100 km depth, the WBZ of the eastern HSZ is dominated by an isolated cluster of intense intermediate deep seismicity (at 100-180 km depth) beneath the Nisyros volcanic complex. It has an extension of about 100x80 km and is build up of 3 parallel

  7. Seismic monitoring with a shallow borehole-geophone array at the COSC-1 drilling site

    NASA Astrophysics Data System (ADS)

    Schmelzbach, Cedric; Juhlin, Christopher; Giese, Rüdiger; Malin, Peter; Maurer, Hansruedi; Robertsson, Johan; Reiser, Fabienne; Greenhalgh, Stewart; Bärlocher, Christoph

    2015-04-01

    An array of borehole geophones was installed at the COSC-1 drilling site with the aim to continuously monitor seismic signals originating from controlled source experiments, ambient and drill-bit noise as well as natural seismicity. These seismic data can provide detailed information on the structure of the elastic parameter distribution around the COSC-1 borehole at the 10's to 100's of meter scale. For this monitoring experiment, nine three-component seismic sensors were deployed in the depth interval from 20 to 100 m below the surface in two shallow boreholes next to the COSC-1 main borehole and the output signals were continuously recorded over five months from late April to late September 2014. This time period includes a short 'quiet' time interval just before the start of the drilling in May, the entire drilling activities until August, and the subsequent vertical-seismic profiling (VSP) experiment in September. In total, around 2.6 terabytes of seismic data were recorded and will be jointly analyzed with other seismic data and supporting geological information. The seismic-data analysis of the five-month records will focus on several aspects. For example, we will explore, what information on the geological structure along the main borehole can be extracted by continuously listening to the drill-bit noise. The data acquired with the shallow monitoring array during the VSP experiments complements the VSP recordings with a geophone chain located at greater depths in the main borehole. The VSP data recorded with the monitoring array can aid in, for example, the seismic-reflection and seismic-refraction processing to image the shallow structure around the borehole (top most few 100's of meters). In addition, recordings of ambient noise from the borehole array may provide information on the shallow subsurface structure at the COSC-1 drilling site. Finally, signals from local earthquakes may be identified, providing information on the natural seismicity of the

  8. BUILDING 341 Seismic Evaluation

    SciTech Connect

    Halle, J.

    2015-06-15

    The Seismic Evaluation of Building 341 located at Lawrence Livermore National Laboratory in Livermore, California has been completed. The subject building consists of a main building, Increment 1, and two smaller additions; Increments 2 and 3.

  9. Seismicity, 1980-86

    SciTech Connect

    Hill, D.P.; Eaton, J.P.; Jones, L.M.

    1990-01-01

    Tens of thousands of small earthquakes occur in California each year, reflecting brittle deformation of the margins of the Pacific and North American plates as they grind inexorably past one another along the San Andreas fault system. The deformational patterns revealed by this ongoing earthquake activity provide a wealth of information on the tectonic processes along this major transform boundary that, every few hundred years, culminate in rupture of the San Andreas fault in a great (M {approx} 8) earthquake. This chapter describes the regional seismicity and the San Andreas transform boundary; seismicity along the San Andreas Fault system; and focal mechanisms and transform-boundary kinematics. Seismicity patterns and the earthquake cycle and distributed seismicity and deformation of the plate margins are discussed.

  10. Seismic Ray Theory

    NASA Astrophysics Data System (ADS)

    Cerveny, V.

    2001-07-01

    The seismic ray method plays an important role in seismology, seismic exploration, and in the interpretation of seismic measurements. Seismic Ray Theory presents the most comprehensive treatment of the method available. Many new concepts that extend the possibilities and increase the method's efficiency are included. The book has a tutorial character: derivations start with a relatively simple problem, in which the main ideas are easier to explain, and then advance to more complex problems. Most of the derived equations are expressed in algorithmic form and may be used directly for computer programming. This book will prove to be an invaluable advanced text and reference in all academic institutions in which seismology is taught or researched.

  11. Seismic excitation by the space shuttle Columbia

    USGS Publications Warehouse

    Kanamori, H.; Mori, J.; Anderson, D.L.; Heaton, T.H.

    1991-01-01

    SEISMIC stations in southern California recorded the atmospheric shock waves generated by the space shuttle Columbia on its return to the Edwards Air Force base on 13 August 1989 (Fig. 1). In addition to the shock wave, the broad-band IRIS-TERRAscope station at Pasadena recorded a distinct pulse with a period of ???2-3 seconds, which arrived 12.5 seconds before the shock wave (Fig. 2). This pulse was also recorded at the University of Southern California, near downtown Los Angeles, where it arrived 3 seconds after the shock wave. The origin of this pulse could not be readily identified. We show here that it was a seismic P wave excited by the motion of high-rise buildings in downtown Los Angeles, which were hit by the shock wave. The proximity of the natural period of the high-rise buildings to that of the Los Angeles basin enabled efficient energy transfer from shock wave to seismic wave.

  12. Passive seismic experiment

    NASA Technical Reports Server (NTRS)

    Latham, G. V.; Ewing, M.; Press, F.; Sutton, G.; Dorman, J.; Nakamura, Y.; Toksoz, N.; Lammlein, D.; Duennebier, F.

    1972-01-01

    The establishment of a network of seismic stations on the lunar surface as a result of equipment installed by Apollo 12, 14, and 15 flights is described. Four major discoveries obtained by analyzing seismic data from the network are discussed. The use of the system to detect vibrations of the lunar surface and the use of the data to determine the internal structure, physical state, and tectonic activity of the moon are examined.

  13. AUTOMATING SHALLOW SEISMIC IMAGING

    SciTech Connect

    Steeples, Don W.

    2003-09-14

    The current project is a continuation of an effort to develop ultrashallow seismic imaging as a cost-effective method potentially applicable to DOE facilities. The objective of the present research is to develop and demonstrate the use of a cost-effective, automated method of conducting shallow seismic surveys, an approach that represents a significant departure from conventional seismic-survey field procedures. Initial testing of a mechanical geophone-planting device suggests that large numbers of geophones can be placed both quickly and automatically. The development of such a device could make the application of SSR considerably more efficient and less expensive. The imaging results obtained using automated seismic methods will be compared with results obtained using classical seismic techniques. Although this research falls primarily into the field of seismology, for comparison and quality-control purposes, some GPR data will be collected as well. In the final year of th e research, demonstration surveys at one or more DOE facilities will be performed. An automated geophone-planting device of the type under development would not necessarily be limited to the use of shallow seismic reflection methods; it also would be capable of collecting data for seismic-refraction and possibly for surface-wave studies. Another element of our research plan involves monitoring the cone of depression of a pumping well that is being used as a proxy site for fluid-flow at a contaminated site. Our next data set will be collected at a well site where drawdown equilibrium has been reached. Noninvasive, in-situ methods such as placing geophones automatically and using near-surface seismic methods to identify and characterize the hydrologic flow regimes at contaminated sites support the prospect of developing effective, cost-conscious cleanup strategies for DOE and others.

  14. Seismic transducer modeling using ABAQUS

    SciTech Connect

    Stephen R. Novascone

    2004-05-01

    A seismic transducer, known as an orbital vibrator, consists of a rotating imbalance driven by an electric motor. When suspended in a liquid-filled wellbore, vibrations of the device are coupled to the surrounding geologic media. In this mode, an orbital vibrator can be used as an efficient rotating dipole source for seismic imaging. Alternately, the motion of an orbital vibrator is affected by the physical properties of the surrounding media. From this point of view, an orbital vibrator can be used as a stand-alone sensor. The reaction to the surroundings can be sensed and recorded by geophones inside the orbital vibrator. These reactions are a function of the media’s physical properties such as modulus, damping, and density, thereby identifying the rock type. This presentation shows how the orbital vibrator and surroundings were modeled with an ABAQUS acoustic FEM. The FEM is found to compare favorably with theoretical predictions. A 2D FEM and analytical model are compared to an experimental data set. Each model compares favorably with the data set.

  15. The Plate Boundary Observatory Borehole Seismic Network

    NASA Astrophysics Data System (ADS)

    Hasting, M.; Eakins, J.; Anderson, G.; Hodgkinson, K.; Johnson, W.; Mencin, D.; Smith, S.; Jackson, M.; Prescott, W.

    2006-12-01

    As part of the NSF-funded EarthScope Plate Boundary Observatory, UNAVCO will install and operate 103 borehole seismic stations throughout the western United States. These stations continuously record three- component seismic data at 100 samples per second, using Geo-Space HS-1-LT 2-HZ geophones in a sonde developed by SONDI and Consultants (Duke University). Each seismic package is connected to an uphole Quanterra Q330 data logger and Marmot external buffer, from which UNAVCO retrieves data in real time. UNAVCO uses the Antelope software suite from Boulder Real-Time Technologies (BRTT) for all data collection and transfer, metadata generation and distribution, and monitoring of the network. The first stations were installed in summer 2005, with 19 stations installed by September 2006, and a total of 28 stations expected by December 2006. In a prime example of cooperation between the PBO and USArray components of EarthScope, the USArray Array Network Facility (ANF), operated by UC San Diego, handled data flow and network monitoring for the PBO seismic stations in the initial stages of network operations. We thank the ANF staff for their gracious assistance over the last several months. Data flow in real time from the remote stations to the UNAVCO Boulder Network Operations Center, from which UNAVCO provides station command and control; verification and distribution of metadata; and basic quality control for all data. From Boulder, data flow in real time to the IRIS DMC for final quality checks, archiving, and distribution. Historic data are available from June 2005 to the present, and are updated in real time with typical latencies of less than ten seconds. As of 1 September 2006, the PBO seismic network had returned 60 GB of raw data. Please visit http://pboweb.unavco.org for additional information on the PBO seismic network.

  16. Tracking glaciers with the Alaska seismic network

    NASA Astrophysics Data System (ADS)

    West, M. E.

    2015-12-01

    More than 40 years ago it was known that calving glaciers in Alaska created unmistakable seismic signals that could be recorded tens and hundreds of kilometers away. Their long monochromatic signals invited studies that foreshadowed the more recent surge in glacier seismology. Beyond a handful of targeted studies, these signals have remained a seismic novelty. No systematic attempt has been made to catalog and track glacier seismicity across the years. Recent advances in understanding glacier sources, combined with the climate significance of tidewater glaciers, have renewed calls for comprehensive tracking of glacier seismicity in coastal Alaska. The Alaska Earthquake Center has included glacier events in its production earthquake catalog for decades. Until recently, these were best thought of as bycatch—accidental finds in the process of tracking earthquakes. Processing improvements a decade ago, combined with network improvements in the past five years, have turned this into a rich data stream capturing hundreds of events per year across 600 km of the coastal mountain range. Though the source of these signals is generally found to be iceberg calving, there are vast differences in behavior between different glacier termini. Some glaciers have strong peaks in activity during the spring, while others peak in the late summer or fall. These patterns are consistent over years pointing to fundamental differences in calving behavior. In several cases, changes in seismic activity correspond to specific process changes observed through other means at particular glacier. These observations demonstrate that the current network is providing a faithful record of the dynamic behavior of several glaciers in coastal Alaska. With this as a starting point, we examine what is possible (and not possible) going forward with dedicated detection schemes.

  17. The Algerian Seismic Network: Performance from data quality analysis

    NASA Astrophysics Data System (ADS)

    Yelles, Abdelkarim; Allili, Toufik; Alili, Azouaou

    2013-04-01

    Seismic monitoring in Algeria has seen a great change after the Boumerdes earthquake of May 21st, 2003. Indeed the installation of a New Digital seismic network (ADSN) upgrade drastically the previous analog telemetry network. During the last four years, the number of stations in operation has greatly increased to 66 stations with 15 Broad Band, 02 Very Broad band, 47 Short period and 21 accelerometers connected in real time using various mode of transmission ( VSAT, ADSL, GSM, ...) and managed by Antelope software. The spatial distribution of these stations covers most of northern Algeria from east to west. Since the operation of the network, significant number of local, regional and tele-seismic events was located by the automatic processing, revised and archived in databases. This new set of data is characterized by the accuracy of the automatic location of local seismicity and the ability to determine its focal mechanisms. Periodically, data recorded including earthquakes, calibration pulse and cultural noise are checked using PSD (Power Spectral Density) analysis to determine the noise level. ADSN Broadband stations data quality is controlled in quasi real time using the "PQLX" software by computing PDFs and PSDs of the recordings. Some other tools and programs allow the monitoring and the maintenance of the entire electronic system for example to check the power state of the system, the mass position of the sensors and the environment conditions (Temperature, Humidity, Air Pressure) inside the vaults. The new design of the network allows management of many aspects of real time seismology: seismic monitoring, rapid determination of earthquake, message alert, moment tensor estimation, seismic source determination, shakemaps calculation, etc. The international standards permit to contribute in regional seismic monitoring and the Mediterranean warning system. The next two years with the acquisition of new seismic equipment to reach 50 new BB stations led to

  18. Third Quarter Hanford Seismic Report for Fiscal Year 2008

    SciTech Connect

    Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E.; Devary, Joseph L.

    2008-09-01

    The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The Hanford Seismic Assessment Team locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 44 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. For the Hanford Seismic Network, fourteen local earthquakes were recorded during the third quarter of fiscal year 2008. The largest event recorded by the network during the third quarter (May 18, 2008 - magnitude 3.7 Mc) was located approximately 17 km east of Prosser at a depth of 20.5 km. With regard to the depth distribution, five earthquakes occurred at shallow depths (less than 4 km, most likely in the Columbia River basalts), six earthquakes at intermediate depths (between 4 and 9 km, most likely in the pre-basalt sediments), and three earthquakes were located at depths greater than 9 km, within the crystalline basement. Geographically, eight earthquakes occurred in swarm areas and six earthquakes were classified as random events. The largest event recorded by the network during the third quarter occurred on May 18 (magnitude 3.7 Mc) and was located approximately 17 km east of Prosser at a depth of 20.5 km. This earthquake was the highest magnitude event recorded in the 46-47 N. latitude / 119-120 W. longitude sector since 1975

  19. MyShake: Building a smartphone seismic network

    NASA Astrophysics Data System (ADS)

    Kong, Q.; Allen, R. M.; Schreier, L.

    2014-12-01

    We are in the process of building up a smartphone seismic network. In order to build this network, we did shake table tests to evaluate the performance of the smartphones as seismic recording instruments. We also conducted noise floor test to find the minimum earthquake signal we can record using smartphones. We added phone noises to the strong motion data from past earthquakes, and used these as an analogy dataset to test algorithms and to understand the difference of using the smartphone network and the traditional seismic network. We also built a prototype system to trigger the smartphones from our server to record signals which can be sent back to the server in near real time. The phones can also be triggered by our developed algorithm running locally on the phone, if there's an earthquake occur to trigger the phones, the signal recorded by the phones will be sent back to the server. We expect to turn the prototype system into a real smartphone seismic network to work as a supplementary network to the existing traditional seismic network.

  20. Pulling the rug out from under California: seismic images of the Mendocino Triple Junction region

    USGS Publications Warehouse

    Trehu, Anne M.

    1995-01-01

    In 1993 and 1994 a network of large-aperture seismic profiles was collected to image the crustal and upper-mantle structure beneath northern California and the adjacent continental margin. The data include approximately 650 km of onshore seismic refraction/reflection data, 2000 km of off-shore multichannel seismic (MCS) reflection data, and simultaneous onshore and offshore recording of the MCS airgun source to yield large-aperture data. Scientists from more than 12 institutions were involved in data acquisition.

  1. Seismic Hazard Analysis as a Controlling Technique of Induced Seismicity in Geothermal Systems

    NASA Astrophysics Data System (ADS)

    Convertito, V.; Sharma, N.; Maercklin, N.; Emolo, A.; Zollo, A.

    2011-12-01

    The effect of induced seismicity of geothermal systems during stimulation and fluid circulation can cover a wide range of values from light and unfelt to severe and damaging. If the design of a modern geothermal system requires the largest efficiency to be obtained from the social point of view it is required that the system could be managed in order to reduce possible impact in advance. In this framework, automatic control of the seismic response of the stimulated reservoir is nowadays mandatory, particularly in proximity of densely populated areas. Recently, techniques have been proposed for this purpose mainly based on the concept of the traffic light. This system provides a tool to decide the level of stimulation rate based on the real-time analysis of the induced seismicity and the ongoing ground motion values. However, in some cases the induced effect can be delayed with respect to the time when the reservoir is stimulated. Thus, a controlling system technique able to estimate the ground motion levels for different time scales can help to better control the geothermal system. Here we present an adaptation of the classical probabilistic seismic hazard analysis to the case where the seismicity rate as well as the propagation medium properties are not constant with time. We use a non-homogeneous seismicity model for modeling purposes, in which the seismicity rate and b-value of the recurrence relationship change with time. Additionally, as a further controlling procedure, we propose a moving time window analysis of the recorded peak ground-motion values aimed at monitoring the changes in the propagation medium. In fact, for the same set of magnitude values recorded at the same stations, we expect that on average peak ground motion values attenuate in same way. As a consequence, the residual differences can be reasonably ascribed to changes in medium properties. These changes can be modeled and directly introduced in the hazard integral. We applied the proposed

  2. Global climate imprint on seismic noise

    NASA Astrophysics Data System (ADS)

    Stutzmann, EléOnore; Schimmel, Martin; Patau, GenevièVe; Maggi, Alessia

    2009-11-01

    In the absence of earthquakes, oceanic microseisms are the strongest signals recorded by seismic stations. Using the GEOSCOPE global seismic network, we show that the secondary microseism spectra have global characteristics that depend on the station latitude and on the season. In both hemispheres, noise amplitude is larger during local winter, and close to the equator, noise amplitude is stable over the year. There is an excellent correlation between microseism amplitude variations over the year and changes in the highest wave areas. Considering the polarization of the secondary microseisms, we show that stations in the Northern Hemisphere and close to the equator record significant changes of the secondary microseism source azimuth over the year. During Northern Hemisphere summer, part or all of the sources are systematically located farther toward the south than during winter. Stations in French Guyana (MPG) and in Algeria (TAM) record microseisms generated several thousand kilometers away in the South Pacific Ocean and in the Indian Ocean, respectively. Thus, secondary microseism sources generated by ocean waves which originate in the Southern Hemisphere can be recorded by Northern Hemisphere stations when local sources are weak. We also show, considering a station close to Antarctica, that primary and secondary microseism noise amplitudes are strongly affected by changes of the sea ice floe and that sources of these microseisms are in different areas. Microseism recording can therefore be used to monitor climate changes.

  3. Seismic Safety Study

    SciTech Connect

    Tokarz, F J; Coats, D W

    2006-05-16

    During the past three decades, the Laboratory has been proactive in providing a seismically safe working environment for its employees and the general public. Completed seismic upgrades during this period have exceeded $30M with over 24 buildings structurally upgraded. Nevertheless, seismic questions still frequently arise regarding the safety of existing buildings. To address these issues, a comprehensive study was undertaken to develop an improved understanding of the seismic integrity of the Laboratory's entire building inventory at the Livermore Main Site and Site 300. The completed study of February 2005 extended the results from the 1998 seismic safety study per Presidential Executive Order 12941, which required each federal agency to develop an inventory of its buildings and to estimate the cost of mitigating unacceptable seismic risks. Degenkolb Engineers, who performed the first study, was recontracted to perform structural evaluations, rank order the buildings based on their level of seismic deficiencies, and to develop conceptual rehabilitation schemes for the most seriously deficient buildings. Their evaluation is based on screening procedures and guidelines as established by the Interagency Committee on Seismic Safety in Construction (ICSSC). Currently, there is an inventory of 635 buildings in the Laboratory's Facility Information Management System's (FIMS's) database, out of which 58 buildings were identified by Degenkolb Engineers that require seismic rehabilitation. The remaining 577 buildings were judged to be adequate from a seismic safety viewpoint. The basis for these evaluations followed the seismic safety performance objectives of DOE standard (DOE STD 1020) Performance Category 1 (PC1). The 58 buildings were ranked according to three risk-based priority classifications (A, B, and C) as shown in Figure 1-1 (all 58 buildings have structural deficiencies). Table 1-1 provides a brief description of their expected performance and damage state

  4. Characterization of Intraplate Seismicity in the Mid-Atlantic US

    NASA Astrophysics Data System (ADS)

    Soto-Cordero, L.; Meltzer, A.; Stachnik, J. C.

    2015-12-01

    Using data from the USArray TA and permanent seismic stations we explore the relationship between seismicity and lithospheric structure in the Mid-Atlantic US where previous studies suggest the clustering of seismicity within several seismic zones. Given low strain rates, creating a robust catalog of tectonic events with a low magnitude threshold is essential. Analysis of events in our study region with hypocenters determined by the Array Network Facility (ANF) during the last 2 years shows that 51% have a depth equal to zero. To assess whether the events are of natural or anthropogenic origin we apply a series of discriminants, such as, geographic correlation to known mining sites, temporal clustering and waveform characteristics. Using West Virginia as a test, we found 100% of events with zero depth are associated with mining operations. Interesting patterns emerge when comparing ANF locations of depths greater than zero with historic seismicity and events instrumentally recorded by permanent stations. Seismicity occurs in some regions where no seismic activity had been previously observed but events along the boundary between the Piedmont and Coastal Plain appear as a continuous band of seismicity making it more difficult to identify discrete seismic zones. Earthquake magnitude threshold is also examined in preparation for high-precision relocation of the events to better address the spatio-temporal nature of seismicity in the region. The ANF catalog shows a magnitude of completeness to 2.2 in the region. However, the ANSS catalog shows 58 events M≤2.2 in the last 2 years while the ANF catalog provides location for only 12 of those events (21%). Continued efforts to calibrate the detection and association algorithms will help lower the magnitude threshold and complete the catalog.

  5. Seismic Swarms at Paricutin Volcano Area. Magmatic Intrusion or Tectonic Seismicity?

    NASA Astrophysics Data System (ADS)

    Pinzon, J. I.; Nunez-Cornu, F. J.; Escudero, C. R.; Rowe, C. A.

    2014-12-01

    We relocate a seismic swarm with more than 700 earthquakes that took place between May and June 2006 in the Paricutin volcano area, Mexico inside of the Michoacan monogenetic volcanic field. This seismic swarm was recorded by the project "Mapping the Riviera Subduction Zone" (MARS), a temporary seismic network that was installed in the states of Jalisco, Colima and Michoacán between January 2006 and June 2007. Previously seismic swarms in the area were reported in the years of 1997, 1999 and 2000. For one that took place in the year of 1997 the Servicio Sismologico Nacional deployed a local network in the area, they conclude that the source of the seismicity was tectonic with depths between 18 and 12 km. The episodes of 1999 and 2000 were reported as similar to the 1997 swarm. A previous analysis of the 2006 swarm concludes that the depth of seismicity migrates from 9 to 5 km and was originated by a magmatic intrusion. We did a relocation of this swarm reading all the events and using Hypo71 and the P-wave velocity model used by the Jalisco Seismic and Acelerometric Network; a waveform analysis using cross-correlation method was also carried out. We obtained 15 earthquakes families with a correlation factor equal or greater than 0.79 and composed focal mechanism for each family. These families present a migration in depth beginning at 16 km and ended at 9 km. Our results agrees with a magmatic intrusion, but not so shallow as the previous study of the 2006 swarm.

  6. Stress-Release Seismic Source for Seismic Velocity Measurement in Mines

    NASA Astrophysics Data System (ADS)

    Swanson, P. L.; Clark, C.; Richardson, J.; Martin, L.; Zahl, E.; Etter, A.

    2014-12-01

    Accurate seismic event locations are needed to delineate roles of mine geometry, stress and geologic structures in developing rockburst conditions. Accurate absolute locations are challenging in mine environments with rapid changes in seismic velocity due to sharp contrasts between individual layers and large time-dependent velocity gradients attending excavations. Periodic use of controlled seismic sources can help constrain the velocity in this continually evolving propagation medium comprising the miners' workplace. With a view to constructing realistic velocity models in environments in which use of explosives is problematic, a seismic source was developed subject to the following design constraints: (i) suitable for use in highly disturbed zones surrounding mine openings, (ii) able to produce usable signals over km-scale distances in the frequency range of typical coal mine seismic events (~10-100 Hz), (iii) repeatable, (iv) portable, (v) non-disruptive to mining operations, and (vi) safe for use in potentially explosive gaseous environments. Designs of the compressed load column seismic source (CLCSS), which generates a stress, or load, drop normal to the surface of mine openings, and the fiber-optic based source-initiation timer are presented. Tests were conducted in a coal mine at a depth of 500 m (1700 ft) and signals were recorded on the surface with a 72-ch (14 Hz) exploration seismograph for load drops of 150-470 kN (16-48 tons). Signal-to-noise ratios of unfiltered signals ranged from ~200 immediately above the source (500 m (1700 ft)) to ~8 at the farthest extent of the array (slant distance of ~800 m (2600 ft)), suggesting the potential for use over longer range. Results are compared with signals produced by weight drop and sledge hammer sources, indicating the superior waveform quality for first-arrival measurements with the CLCSS seismic source.

  7. Inter- and Post-Seismic Ground Deformation of the 2012 Emilia Seismic Sequence By Means of COSMO-Skymed and Ers-Envisat InSAR Time Series

    NASA Astrophysics Data System (ADS)

    Pezzo, G.; Tolomei, C.; Salvi, S.; Atzori, S.; Merryman Boncori, J. P.

    2014-12-01

    On May 20, 2012, a moderate earthquake of local magnitude, M 5.9 started a seismic sequence in the central Po Plain of Northern Italy. The mainshock occurred in an area where seismicity of comparable magnitude has neither been recorded nor reported in the historical record over the last 1,000 years. On May 29, 2012 a second large earthquake of M 5.8 occurred 12 km WSW of the mainshock, starting a new seismic sequence in the western area; a total of seven earthquakes with M >5 occurred in the area between May 20 and June 3, 2012. After the first mainshock, a COSMO-SkyMed acquisition plan was going to provide data over a wide area of the Emilia Region covering both the epicentral region and the adjacent West and East areas, and was later extended up to December 31th, 2013 to monitor the post-seismic deformation. Using multitemporal SBAS InSAR technique we measured co and post-seismic deformations; . we used COSMO-SkyMed image datasets spanning the time period 2012-2013, along both ascending and descending orbit. Moreover we studied the pre-seismic (inter-seismic) phase by means of ERS1/2 and ASAR-Envisat data covering the 1992-2010 temporal interval. In this framework the Emilia seismic sequence represents a very interesting case for the study of the complete seismic cycle.

  8. Studies of infrasound propagation using the USArray seismic network (Invited)

    NASA Astrophysics Data System (ADS)

    Hedlin, M. A.; Degroot-Hedlin, C. D.; Walker, K. T.

    2010-12-01

    Although there are currently ~ 100 infrasound arrays worldwide, more than ever before, the station density is still insufficient to provide validation for detailed propagation modeling. Much structure in the atmosphere is short-lived and occurs at spatial scales much smaller than the average distance between infrasound stations. Relatively large infrasound signals can be observed on seismic channels due to coupling at the Earth's surface. Recent research, using data from the 70-km spaced 400-station USArray and other seismic network deployments, has shown the value of dense seismic network data for filling in the gaps between infrasound arrays. The dense sampling of the infrasound wavefield has allowed us to observe complete travel-time branches of infrasound signals and shed more light on the nature of infrasound propagation. We present early results from our studies of impulsive atmospheric sources, such as series of UTTR rocket motor detonations in Utah. The Utah blasts have been well recorded by USArray seismic stations and infrasound arrays in Nevada and Washington State. Recordings of seismic signals from a series of six events in 2007 are used to pinpoint the shot times to < 1 second. Variations in the acoustic branches and signal arrival times at the arrays are used to probe variations in atmospheric structure. Although we currently use coupled signals we anticipate studying dense acoustic network recordings as the USArray is currently being upgraded with infrasound microphones. These new sensors will allow us to make semi-continental scale network recordings of infrasound signals free of concerns about how the signals observed on seismic channels were modified when being coupled to seismic.

  9. Cruise report for a seismic investigation of gas hydrates in the Mississippi Canyon region, northern Gulf of Mexico; cruise M1-98-GM

    USGS Publications Warehouse

    Cooper, Alan K.; Hart, Patrick E.; Pecher, Ingo

    1998-01-01

    During the cruise about 850 km of multichannel and single-channel seismic data were recorded. Seismic measurements at nine ocean-bottom seismometer (OBS) stations were recorded for several of the multichannel tracklines (see Fig. 3 in report). The following report describes the field operations and equipment systems employed, gives two examples of ship-board seismic records, and outlines a few preliminary results.

  10. 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.

  11. Nevada Test Site seismic: telemetry measurements

    SciTech Connect

    Albright, J N; Parker, L E; Horton, E H

    1983-08-01

    The feasibility and limitations of surface-to-tunnel seismic telemetry at the Nevada Test Site were explored through field measurements using current technology. Range functions for signaling were determined through analysis of monofrequency seismic signals injected into the earth at various sites as far as 70 km (43 mi) from installations of seismometers in the G-Tunnel complex of Rainier Mesa. Transmitted signal power at 16, 24, and 32 Hz was measured at two locations in G-Tunnel separated by 670 m (2200 ft). Transmissions from 58 surface sites distributed primarily along three azimuths from G-Tunnel were studied. The G-Tunnel noise environment was monitored over the 20-day duration of the field tests. Noise-power probability functions were calculated for 20-s and 280-s seismic-record populations. Signaling rates were calculated for signals transmitted from superior transmitter sites to G-Tunnel. A detection threshold of 13 dB re 1 nm/sup 2/ displacement power at 95% reliability was demanded. Consideration of field results suggests that even for the frequency range used in this study, substantially higher signaling rates are likely to be obtained in future work in view of the present lack of information relevant to hardware-siting criteria and the seismic propagation paths at the Nevada Test Site. 12 references.

  12. Application of seismic tomography in underground mining

    SciTech Connect

    Scott, D.F.; Williams, T.J.; Friedel, M.J.

    1996-12-01

    Seismic tomography, as used in mining, is based on the principle that highly stressed rock will demonstrate relatively higher P-wave velocities than rock under less stress. A decrease or increase in stress over time can be verified by comparing successive tomograms. Personnel at the Spokane Research Center have been investigating the use of seismic tomography to identify stress in remnant ore pillars in deep (greater than 1220 in) underground mines. In this process, three-dimensional seismic surveys are conducted in a pillar between mine levels. A sledgehammer is used to generate P-waves, which are recorded by geophones connected to a stacking signal seismograph capable of collecting and storing the P-wave data. Travel times are input into a spreadsheet, and apparent velocities are then generated and merged into imaging software. Mine workings are superimposed over apparent P-wave velocity contours to generate a final tomographic image. Results of a seismic tomographic survey at the Sunshine Mine, Kellogg, ED, indicate that low-velocity areas (low stress) are associated with mine workings and high-velocity areas (higher stress) are associated with areas where no mining has taken place. A high stress gradient was identified in an area where ground failed. From this tomographic survey, as well, as four earlier surveys at other deep underground mines, a method was developed to identify relative stress in remnant ore pillars. This information is useful in making decisions about miner safety when mining such ore pillars.

  13. Generalised receiver functions and seismic interferometry

    NASA Astrophysics Data System (ADS)

    Galetti, Erica; Curtis, Andrew

    2012-04-01

    Classical seismological receiver functions are correlational or deconvolutional combinations of vertical and horizontal component seismometer recordings of earthquake waves that focus information on near-receiver subsurface Earth structure and properties. We show that seismic interferometry can be thought of as a generalisation of receiver functions analysis to cases where recordings at pairs of receivers are considered simultaneously, and where either the same or different component recordings are combined. Further, seismic interferometry uses any of deconvolution, convolution and cross-correlation, and energy from either impulsive or random noise sources. We show both how receiver functions can logically be extended to a new, convolutional form, and that the now little-used correlational form of receiver functions contains more intuitive information than previously realised. Seismic interferometry has provided other extraordinary extensions to seismologists' arsenal. Passive noise recordings can be converted into seismograms from virtual (imagined) earthquakes that in turn can be used to image the real Earth. Active sources (e.g., earthquakes or man-made sources) can be redatumed into new, virtual sources elsewhere, or can be converted into virtual sensors (seismometers) that record seismograms from other real earthquakes, man-made sources or noise sources that occur either in the future or in the past. And the ability to construct virtual sources and sensors at desired times and locations (rather than having to wait for earthquake sources that occur at uncontrollable locations) promises more repeatable monitoring of changes in Earth subsurface properties over time. Indeed, so-called coda wave interferometry offers unprecedented accuracy in detecting such changes. Finally, existing theoretical extensions to other regimes such as electromagnetic, electrokinetic and diffusive energy propagation may lead to future revolutions in other domains of science.

  14. 50 years of Global Seismic Observations

    NASA Astrophysics Data System (ADS)

    Anderson, K. R.; Butler, R.; Berger, J.; Davis, P.; Derr, J.; Gee, L.; Hutt, C. R.; Leith, W. S.; Park, J. J.

    2007-12-01

    Seismological recordings have been made on Earth for hundreds of years in some form or another, however, global monitoring of earthquakes only began in the 1890's when John Milne created 40 seismic observatories to measure the waves from these events. Shortly after the International Geophysical Year (IGY), a concerted effort was made to establish and maintain a more modern standardized seismic network on the global scale. In the early 1960's, the World-Wide Standardized Seismograph Network (WWSSN) was established through funding from the Advanced Research Projects Agency (ARPA) and was installed and maintained by the USGS's Albuquerque Seismological Laboratory (then a part of the US Coast and Geodetic Survey). This network of identical seismic instruments consisted of 120 stations in 60 countries. Although the network was motivated by nuclear test monitoring, the WWSSN facilitated numerous advances in observational seismology. From the IGY to the present, the network has been upgraded (High-Gain Long-Period Seismograph Network, Seismic Research Observatories, Digital WWSSN, Global Telemetered Seismograph Network, etc.) and expanded (International Deployment of Accelerometers, US National Seismic Network, China Digital Seismograph Network, Joint Seismic Project, etc.), bringing the modern day Global Seismographic Network (GSN) to a current state of approximately 150 stations. The GSN consists of state-of-the-art very broadband seismic transducers, continuous power and communications, and ancillary sensors including geodetic, geomagnetic, microbarographic, meteorological and other related instrumentation. Beyond the GSN, the system of global network observatories includes contributions from other international partners (e.g., GEOSCOPE, GEOFON, MEDNET, F-Net, CTBTO), forming an even larger backbone of permanent seismological observatories as a part of the International Federation of Digital Seismograph Networks. 50 years of seismic network operations have provided

  15. Mammoth Mountain, California broadband seismic experiment

    NASA Astrophysics Data System (ADS)

    Dawson, P. B.; Pitt, A. M.; Wilkinson, S. K.; Chouet, B. A.; Hill, D. P.; Mangan, M.; Prejean, S. G.; Read, C.; Shelly, D. R.

    2013-12-01

    Mammoth Mountain is a young cumulo-volcano located on the southwest rim of Long Valley caldera, California. Current volcanic processes beneath Mammoth Mountain are manifested in a wide range of seismic signals, including swarms of shallow volcano-tectonic earthquakes, upper and mid-crustal long-period earthquakes, swarms of brittle-failure earthquakes in the lower crust, and shallow (3-km depth) very-long-period earthquakes. Diffuse emissions of C02 began after a magmatic dike injection beneath the volcano in 1989, and continue to present time. These indications of volcanic unrest drive an extensive monitoring effort of the volcano by the USGS Volcano Hazards Program. As part of this effort, eleven broadband seismometers were deployed on Mammoth Mountain in November 2011. This temporary deployment is expected to run through the fall of 2013. These stations supplement the local short-period and broadband seismic stations of the Northern California Seismic Network (NCSN) and provide a combined network of eighteen broadband stations operating within 4 km of the summit of Mammoth Mountain. Data from the temporary stations are not available in real-time, requiring the merging of the data from the temporary and permanent networks, timing of phases, and relocation of seismic events to be accomplished outside of the standard NCSN processing scheme. The timing of phases is accomplished through an interactive Java-based phase-picking routine, and the relocation of seismicity is achieved using the probabilistic non-linear software package NonLinLoc, distributed under the GNU General Public License by Alomax Scientific. Several swarms of shallow volcano-tectonic earthquakes, spasmodic bursts of high-frequency earthquakes, a few long-period events located within or below the edifice of Mammoth Mountain and numerous mid-crustal long-period events have been recorded by the network. To date, about 900 of the ~2400 events occurring beneath Mammoth Mountain since November 2011 have

  16. Community Seismic Network (CSN)

    NASA Astrophysics Data System (ADS)

    Clayton, R. W.; Heaton, T. H.; Kohler, M. D.; Cheng, M.; Guy, R.; Chandy, M.; Krause, A.; Bunn, J.; Olson, M.; Faulkner, M.; Liu, A.; Strand, L.

    2012-12-01

    We report on developments in sensor connectivity, architecture, and data fusion algorithms executed in Cloud computing systems in the Community Seismic Network (CSN), a network of low-cost sensors housed in homes and offices by volunteers in the Pasadena, CA area. The network has over 200 sensors continuously reporting anomalies in local acceleration through the Internet to a Cloud computing service (the Google App Engine) that continually fuses sensor data to rapidly detect shaking from earthquakes. The Cloud computing system consists of data centers geographically distributed across the continent and is likely to be resilient even during earthquakes and other local disasters. The region of Southern California is partitioned in a multi-grid style into sets of telescoping cells called geocells. Data streams from sensors within a geocell are fused to detect anomalous shaking across the geocell. Temporal spatial patterns across geocells are used to detect anomalies across regions. The challenge is to detect earthquakes rapidly with an extremely low false positive rate. We report on two data fusion algorithms, one that tessellates the surface so as to fuse data from a large region around Pasadena and the other, which uses a standard tessellation of equal-sized cells. Since September 2011, the network has successfully detected earthquakes of magnitude 2.5 or higher within 40 Km of Pasadena. In addition to the standard USB device, which connects to the host's computer, we have developed a stand-alone sensor that directly connects to the internet via Ethernet or wifi. This bypasses security concerns that some companies have with the USB-connected devices, and allows for 24/7 monitoring at sites that would otherwise shut down their computers after working hours. In buildings we use the sensors to model the behavior of the structures during weak events in order to understand how they will perform during strong events. Visualization models of instrumented buildings ranging

  17. Bandung seismic experiment: Towards tomographic imaging by using ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Pranata, Bayu; Yudistira, Tedy; Saygin, Erdinc; Cummins, Phil R.; Widiyantoro, Sri; Zulfakriza, Nugraha, Andri D.

    2016-05-01

    Bandung is one of the most densely populated cities in Indonesia with vital infrastructures. On the other hand, this area is surrounded by potential sources of earthquakes that make Bandung vulnerable to earthquakes. Structure of seismic velocity and sediment thickness are crucially needed in the earthquake hazard reduction program for Bandung. Based on this consideration, we deployed 64 seismic stations over the Bandung basin to record seismic ambient noise. In this study, we employed a cross-correlation method to the simultaneously recorded data to retrieve interstation Green's functions. We measured group velocity of the retrieved Green's functions by using frequency-time analysis technique. By the end of this project, the set of interstation group velocity will be inverted to image the shallow seismic velocity structure of the Bandung basin and its surrounding areas including Mt. Tangkuban Parahu and Lembang fault. As the first stage of this work, currently we focus on Green ' s function calculation as well as the interstation group velocity measurements. The general characteristics of group velocity can be evaluated from the plot of cross-correlation function as a function of its interstation distance.

  18. An analysis of a seismic reflection from the base of a gas hydrate zone, offshore Peru

    USGS Publications Warehouse

    Miller, J.J.; Lee, M.W.; Von Huene, R.

    1991-01-01

    Seismic reflection data recorded near ODP Site 688, offshore Peru, exhibit a persistent bottom-simulating reflector (BSR) from a depth corresponding to the theoretical base of the gas hdyrate stability field. To carry out a quantitative analysis of the BSR, the seismic data were reprocessed using signature deconvolution and true amplitude recovery techniques. Results indicate the BSR is discontinuous laterally. -from Authors

  19. The Chelyabinsk Meteorite as a multiple source of acoustic and seismic waves

    NASA Astrophysics Data System (ADS)

    Kitov, I. O.; Bobrov, D. I.; Ovchinnikov, V. M.; Rozhkov, M. V.

    2016-05-01

    Shock waves and impact of the Chelyabinsk Meteorite fragments on the ground initiated various waves in the atmosphere and the earth. Three different sources of seismic and infrasound waves were found by arrival time and azimuth of seismic and infrasound waves recorded by the International Monitoring System.

  20. Adjustment of minimum seismic shear coefficient considering site effects for long-period structures

    NASA Astrophysics Data System (ADS)

    Guan, Minsheng; Du, Hongbiao; Cui, Jie; Zeng, Qingli; Jiang, Haibo

    2016-06-01

    Minimum seismic base shear is a key factor employed in the seismic design of long-period structures, which is specified in some of the major national seismic building codes viz. ASCE7-10, NZS1170.5 and GB50011-2010. In current Chinese seismic design code GB50011-2010, however, effects of soil types on the minimum seismic shear coefficient are not considered, which causes problems for long-period structures sited in hard or rock soil to meet the minimum base shear requirement. This paper aims to modify the current minimum seismic shear coefficient by taking into account site effects. For this purpose, effective peak acceleration (EPA) is used as a representation for the ordinate value of the design response spectrum at the plateau. A large amount of earthquake records, for which EPAs are calculated, are examined through the statistical analysis by considering soil conditions as well as the seismic fortification intensities. The study indicates that soil types have a significant effect on the spectral ordinates at the plateau as well as the minimum seismic shear coefficient. Modified factors related to the current minimum seismic shear coefficient are preliminarily suggested for each site class. It is shown that the modified seismic shear coefficients are more effective to the determination of minimum seismic base shear of long-period structures.

  1. 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

  2. Magnitude correlations in global seismicity

    SciTech Connect

    Sarlis, N. V.

    2011-08-15

    By employing natural time analysis, we analyze the worldwide seismicity and study the existence of correlations between earthquake magnitudes. We find that global seismicity exhibits nontrivial magnitude correlations for earthquake magnitudes greater than M{sub w}6.5.

  3. SEISMIC DATA FOR NUCLEAR EXPLOSION MONITORING IN THE ARABIAN PENINSULA

    SciTech Connect

    Rodgers, A; Al-Amri, A

    2004-07-08

    We report results from the third and final year of our project (ROA0101-35) to collect seismic event and waveform data recorded in and around the Arabian Peninsula. This effort involves several elements. We are working with King Abdulaziz City for Science and Technology to collect data from the Saudi National Seismic Network, that consists of 38 digital three-component stations (27 broadband and 11 short-period). We have an ongoing collaboration with the Kuwait Institute for Scientific Research, which runs the eight station Kuwait National Seismic Network. We installed two temporary broadband stations in the United Arab Emirates (funded by NNSA NA-24 Office of Non-Proliferation & International Security). In this paper we present a summary of data collected under these efforts including integration of the raw data into LLNL's Seismic Research Database and preliminary analysis of souce parameters and earth structure.

  4. Advanced Seismic Probabilistic Risk Assessment Demonstration Project Plan

    SciTech Connect

    Justin Coleman

    2014-09-01

    Idaho National Laboratories (INL) has an ongoing research and development (R&D) project to remove excess conservatism from seismic probabilistic risk assessments (SPRA) calculations. These risk calculations should focus on providing best estimate results, and associated insights, for evaluation and decision-making. This report presents a plan for improving our current traditional SPRA process using a seismic event recorded at a nuclear power plant site, with known outcomes, to improve the decision making process. SPRAs are intended to provide best estimates of the various combinations of structural and equipment failures that can lead to a seismic induced core damage event. However, in general this approach has been conservative, and potentially masks other important events (for instance, it was not the seismic motions that caused the Fukushima core melt events, but the tsunami ingress into the facility).

  5. Seismic ruggedness of relays

    SciTech Connect

    Merz, K.L. )

    1991-08-01

    This report complements EPRI report NP-5223 Revision 1, February 1991, and presents additional information and analyses concerning generic seismic ruggedness of power plant relays. Existing and new test data have been used to construct Generic Equipment Ruggedness Spectra (GERS) which can be used in identifying rugged relays during seismic re-evaluation of nuclear power plants. This document is an EPRI tier 1 report. The results of relay fragility tests for both old and new relays are included in an EPRI tier 2 report with the same title. In addition to the presentation of relay GERS, the tier 2 report addresses the applicability of GERS to relays of older vintage, discusses the important identifying nomenclature for each relay type, and examines relay adjustment effects on seismic ruggedness. 9 refs., 3 figs, 1 tab.

  6. Downhole seismic array system

    SciTech Connect

    Petermann, S.G.

    1992-03-03

    This patent describes an apparatus of receiving seismic signals from an earth formation at least at one or more points in a wellbore penetrating the formation. It comprises a sonde including extensible and retractable support means thereon for supporting seismic signal receiver means, hydraulic actuator means for extending and reacting the support means, body means for supporting the actuator means and the support means and signal transmitting means for transmitting electrical signals related to seismic signals received by the receiver means; tubing means connected to the sonde for deploying the sonde in the wellbore, the tubing means including electrical conductor means disposed therein for conducting electrical signals between means on the surface of the formation and the sonde and the tubing means comprising means for conducting hydraulic fluid to the sonde for operation of the actuator means; and means for supplying hydraulic fluid from the surface of the formation through the tubing means to the sonde for operating the actuator means.

  7. Induced seismicity. Final report

    SciTech Connect

    Segall, P.

    1997-09-18

    The objective of this project has been to develop a fundamental understanding of seismicity associated with energy production. Earthquakes are known to be associated with oil, gas, and geothermal energy production. The intent is to develop physical models that predict when seismicity is likely to occur, and to determine to what extent these earthquakes can be used to infer conditions within energy reservoirs. Early work focused on earthquakes induced by oil and gas extraction. Just completed research has addressed earthquakes within geothermal fields, such as The Geysers in northern California, as well as the interactions of dilatancy, friction, and shear heating, on the generation of earthquakes. The former has involved modeling thermo- and poro-elastic effects of geothermal production and water injection. Global Positioning System (GPS) receivers are used to measure deformation associated with geothermal activity, and these measurements along with seismic data are used to test and constrain thermo-mechanical models.

  8. Canadian Seismic Agreement

    SciTech Connect

    Wetmiller, R.J.; Lyons, J.A.; Shannon, W.E.; Munro, P.S.; Thomas, J.T.; Andrew, M.D.; Lapointe, S.P.; Lamontagne, M.; Wong, C.; Anglin, F.M.; Adams, J.; Cajka, M.G.; McNeil, W.; Drysdale, J.A. )

    1992-05-01

    This is a progress report of work carried out under the terms of a research agreement entitled the Canadian Seismic Agreement'' between the US Nuclear Regulatory Commission (USNRC), the Canadian Commercial Corporation and the Geophysics Division of the Geological Survey of Canada (GD/GSC) during the period from July 01, 1989 to June 30, 1990. The Canadian Seismic Agreement'' supports generally the operation of various seismograph stations in eastern Canada and the collection and analysis of earthquake data for the purpose of mitigating seismic hazards in eastern Canada and the northeastern US. The specific activities carried out in this one-year period are summarized below under four headings; Eastern Canada Telemetred Network and local network developments, Datalab developments, strong-motion network developments and earthquake activity. During this period the first surface fault unequivocably determined to have accompanied a historic earthquake in eastern North America, occurred in northern Quebec.

  9. Controllable seismic source

    SciTech Connect

    Gomez, Antonio; DeRego, Paul Jeffrey; Ferrell, Patrick Andrew; Thom, Robert Anthony; Trujillo, Joshua J.; Herridge, Brian

    2015-09-29

    An apparatus for generating seismic waves includes a housing, a strike surface within the housing, and a hammer movably disposed within the housing. An actuator induces a striking motion in the hammer such that the hammer impacts the strike surface as part of the striking motion. The actuator is selectively adjustable to change characteristics of the striking motion and characteristics of seismic waves generated by the impact. The hammer may be modified to change the physical characteristics of the hammer, thereby changing characteristics of seismic waves generated by the hammer. The hammer may be disposed within a removable shock cavity, and the apparatus may include two hammers and two shock cavities positioned symmetrically about a center of the apparatus.

  10. Controllable seismic source

    SciTech Connect

    Gomez, Antonio; DeRego, Paul Jeffrey; Ferrel, Patrick Andrew; Thom, Robert Anthony; Trujillo, Joshua J.; Herridge, Brian

    2014-08-19

    An apparatus for generating seismic waves includes a housing, a strike surface within the housing, and a hammer movably disposed within the housing. An actuator induces a striking motion in the hammer such that the hammer impacts the strike surface as part of the striking motion. The actuator is selectively adjustable to change characteristics of the striking motion and characteristics of seismic waves generated by the impact. The hammer may be modified to change the physical characteristics of the hammer, thereby changing characteristics of seismic waves generated by the hammer. The hammer may be disposed within a removable shock cavity, and the apparatus may include two hammers and two shock cavities positioned symmetrically about a center of the apparatus.

  11. Specification goals for a Mars seismic network

    NASA Technical Reports Server (NTRS)

    Davis, Paul M.

    1990-01-01

    A seismic network on Mars should have enough stations (e.g., 24) to characterize the seismicity of the planet for comparison with a diversity of structural features; be comprised of low noise stations, preferably underground, 3 to 4 orders of magnitude more sensitive than those used on Viking; record over a sufficient band-width (DC-30 Hz) to detect micro-earthquakes to normal modes; and record for a sufficient duration (10 years) and data rate (10(exp 8) Mb/day/station) to obtain a data set comparable to that from the Apollo mission to the Moon so that locations of major internal boundaries can be inferred, such as those in the Earth, i.e., crust - lithosphere - asthenosphere - upper - lower phase transitions - outer - inner core. The proposed Mars Global Network Mission provides an opportunity to sense the dynamics and probe the interior of the planet. The seismic objectives, the availability of the instrumentation and trade-offs to meet them are discussed.

  12. 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.

  13. CD Recorders.

    ERIC Educational Resources Information Center

    Falk, Howard

    1998-01-01

    Discussion of CD (compact disc) recorders describes recording applications, including storing large graphic files, creating audio CDs, and storing material downloaded from the Internet; backing up files; lifespan; CD recording formats; continuous recording; recording software; recorder media; vulnerability of CDs; basic computer requirements; and…

  14. Results from the apollo-12 passive seismic experiment

    USGS Publications Warehouse

    Latham, G.

    1971-01-01

    The objective of the passive seismic experiment is to measure vibrations of the lunar surface produced by all natural and artificial sources of seismic energy and to use these data to deduce the internal structure and composition of the moon, the nature of forces which may cause deformation of the moon and moonquakes, and the numbers and masses of meteoroids striking the lunar surface. The ALSEP* seismometers can magnify lunar surface vibrations 10 million times. No instrument can operate on earth with this sensitivity, because weather and man produce too much seismic noise. To obtain answers to the above questions, seismic data must be combined with data from laboratory measurements of the physical and chemical properties of surface rocks, and many other geophyiscal and geochemical measurements. Thus far, we have had the opportunity to record data from two lunar seismic stations which were installed by the astronauts during Apollo misions  and 12. The combined recording time from the stations is presently over 12 months, but there was no overlap to permit recording of the same event at two stations. 

  15. 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.

  16. Investigations of acoustic-seismic effects at long range - Early-arriving seismic waves from Apollo 16

    NASA Technical Reports Server (NTRS)

    Dalins, I.; Mccarty, V. M.; Kaschak, G.; Donn, W. L.

    1974-01-01

    A reasonably comprehensive technical effort is described dealing with the investigations of acoustically generated seismic waves of Apollo 16 and Apollo 17 origin along the eastern seabord of the United States. This expanded effort is a continuation of earlier, rather successful detections of rocket-generated seismic disturbances on Skidaway Island, Georgia. The more recent effort has yielded few positive results other than a recording of an early-arriving seismic wave from Apollo 16 that was detected in Jacksonville. Evaluation of the negative results obtained in the Fort Monmouth area, with earlier studies of infrasound, local weather conditions, and geology, could be advantageous in the process of trying to gain a better insight into the acoustic-seismic resonance mechanism requiring phase-velocity matching at the atmosphere-ground interface.

  17. Use of an Educational Seismic Network for Monitoring Intraplate Seismicity in the Central United States

    NASA Astrophysics Data System (ADS)

    Webb, S. M.; Bailey, L.; Lindsey, J.; Pavlis, G. L.; Hamburger, M. W.; Bauer, M.

    2006-12-01

    The Indiana PEPP seismic network is a 21-station broadband, digital seismic network operated as a collaboration between Indiana University and area high schools, colleges, and museums. Since 1999 the network has used internet data transmission to provide real-time network recording and archiving at the IRIS Data Management Center. The network provides expanded coverage of intraplate seismicity, quarry and mining explosion, and teleseismic earthquakes. We analyzed the signal-to-noise ratio for 11 local events tabulated in the ANSS catalog and used this to project the detection threshold for the network. We define a detection threshold for these events as the minimum projected equivalent event with 5 phases having a signal to noise ration of 3 or larger. We found that the detection threshold for events in southern Indiana, which is the approximate center of the network, varied from 1.7 to 2.3. For events outside this area the estimated detection floor ranges from 2.5 to 3.3. We also examined 264 regional earthquakes (300 to 1500 km) tabulated in the ANSS catalog during 2002. We found events larger than approximately 2.5 in the New Madrid region were consistently detectable. Regional events larger than 3.0 in the 700 to 1500 km distance range were consistently recorded. To further clarify detection capabilities we carefully scanned all data from a 114- day period, from day 51 through 164 of 2002. During this test period we observed 3520 mining explosions (29 events/day), all teleseismic events larger than about 5.0, and only 2 unambiguous earthquakes (the June 18, M_L = 5.0, Evansville (Caborn) mainshock and a single aftershock). This result illustrates an important practical issue in appraising seismicity levels in this area: less than 0.1% of the detected signals were local earthquakes. We extended this review period to include the remaining 251 days of 2002, but examining only the nighttime hours (0000-1200 UTC), when the levels of noise and blasting are minimal

  18. The reliability of radon as seismic precursor

    NASA Astrophysics Data System (ADS)

    Emilian Toader, Victorin; Moldovan, Iren Adelina; Ionescu, Constantin; Marmureanu, Alexandru

    2016-04-01

    Our multidisciplinary network (AeroSolSys) located in Vrancea (Curvature Carpathian Mountains) includes radon concentration monitoring in five stations. We focus on lithosphere and near surface low atmosphere phenomena using real-time information about seismicity, + / - ions, clouds, solar radiation, temperature (air, ground), humidity, atmospheric pressure, wind speed and direction, telluric currents, variations of the local magnetic field, infrasound, variations of the atmospheric electrostatic field, variations in the earth crust with inclinometers, electromagnetic activity, CO2 concentration, ULF radio wave propagation, seismo-acoustic emission, animal behavior. The main purpose is to inform the authorities about risk situation and update hazard scenarios. The radon concentration monitoring is continuously with 1 hour or 3 hours sample rate in locations near to faults in an active seismic zone characterized by intermediate depth earthquakes. Trigger algorithms include standard deviation, mean and derivative methods. We correlate radon concentration measurements with humidity, temperature and atmospheric pressure from the same equipment. In few stations we have meteorological information, too. Sometime the radon concentration has very high variations (maxim 4535 Bq/m3 from 106 Bq/m3) in short time (1 - 2 days) without being accompanied by an important earthquake. Generally the cause is the high humidity that could be generated by tectonic stress. Correlation with seismicity needs information from minimum 6 month in our case. For 10605 hours, 618 earthquakes with maxim magnitude 4.9 R, we have got radon average 38 Bq/m3 and exposure 408111 Bqh/m3 in one station. In two cases we have correlation between seismicity and radon concentration. In other one we recorded high variation because the location was in an area with multiple faults and a river. Radon can be a seismic precursor but only in a multidisciplinary network. The anomalies for short or long period of

  19. Detecting seismic events using Benford's Law

    NASA Astrophysics Data System (ADS)

    Diaz, Jordi; Gallart, Josep; Ruiz, Mario

    2015-04-01

    The Benford's Law (BL) states that the distribution of first significant digits is not uniform but follows a logarithmic frequency distribution. Even if a remarkable wide range of natural and socioeconomical data sets, from stock market values to quantum phase transitions, fit this peculiar law, the conformity to it has deserved few scientific applications, being used mainly as a test to pinpoint anomalous or fraudulent data. We developed a procedure to detect the arrival of seismic waves based on the degree of conformity of the amplitude values in the raw seismic trace to the BL. The signal is divided in time windows of appropriate length and the fitting of the first digits distribution to BL is checked in each time window using a conformity estimator. We document that both teleseismic and local earthquakes can be clearly identified in this procedure and we compare its performance with respect to the classical STA/LTA approach. Moreover, we show that the conformity of the seismic record to the BL does not depend on the amplitude of the incoming series, as the occurrence of events with very different amplitudes result in quite similar degree of BL fitting. On the other hand, we show that natural or man-made quasi-monochromatic seismic signals, surface wave trains or engine-generated vibrations can be identified through their very low BL estimator values, when appropriate interval lengths are used. Therefore, we conclude that the degree of conformity of a seismic signal with the BL is primarily dependent on the frequency content of that signal.

  20. Broadband Seismic Study of the Dominican Republic

    NASA Astrophysics Data System (ADS)

    Pulliam, J.; Polanco Rivera, E.; Pujols Guridy, R.; Huerfano Moreno, V. A.; Lopez, A. M.

    2014-12-01

    The Northeast Caribbean Plate Boundary Zone (NCPBZ) is characterized by oblique subduction of oceanic crust belonging to the North American Plate, a broad zone of deformation to accommodate strain, and the development of transform and normal faults on and around the island of Hispaniola. Other features may include the formation of a new microplates, rearrangement and aggregation of crustal fragments into new islands, and rotations of the microplates. Numerous issues regarding the nature and timing of formation of the features described above, their roles in regional tectonics and even whether they exist at all, remain unresolved. Our short-term goal is to better constraint lithospheric structure and identify active earthquake faults with a temporary broadband seismic network in the Dominican Republic. The oblique-subduction-to-strike-slip transition found in the NCPBZ is representative of numerous locales around the world, so lessons learned here may inform our understanding of plate tectonics broadly. In 2013-2014 we installed sixteen broadband seismic stations in the Dominican Republic. The temporary network will remain in place for two years. Data acquired by the temporary network will be integrated with data recorded by existing seismic facilities in the region and the combined dataset will be used for a series of analyses that will, collectively, allow us to image lithospheric structure and aid seismic hazard assessment for the island of Hispaniola. Preliminary results will be presented from the deployment, including regional earthquake locations and improved 1D Earth structure as well as plans for collaborations between regional seismic networks and local capacity-building.

  1. Seismic monitoring of an Alpine mountain river

    NASA Astrophysics Data System (ADS)

    Díaz, J.; Ruíz, M.; Crescentini, L.; Amoruso, A.; Gallart, J.

    2014-04-01

    The Canfranc underground laboratory (LSC), excavated under the Central Pyrenees, is mainly devoted to the study of phenomena which needs "cosmic silence." It also hosts a geodynamical facility, named Geodyn, which holds an accelerometer, a broadband seismometer, and two high-resolution laser strainmeters. During the routine processing of the seismic data, we detected an unusual spectral signature in the 2-10 Hz frequency band, which does not correspond to the typical sources of seismic noise and which can also be recognized in the strain records. After checking against meteorological and hydrological data, we can relate those signals to variations in the discharge by the Aragon River, an Alpine-style river in the southern Pyrenees, located about 400 m from the LSC Geodyn facility. Four main episodes have been identified since early 2011, each lasting 1-2 to 6-8 days. Additionally, a limited number of shorter episodes have also been detected. Three types of river-generated seismic events have been identified, related respectively to moderate rainfall, snowmelt, and flooding events associated to severe storms. Each of those types has distinctive characteristics which allow monitoring the hydrological events from the analysis of seismic and deformation data. A few previous studies have already described the seismic noise close to rivers with larger discharge or in small-scale experimental settings, and we are showing here that the so-called "fluvial seismology" can be useful to study the hydrological evolution of Alpine style streams and may have a potential interest for the civil authorities in charge of the management of hydrological basins.

  2. Monitoring hydraulic fracturing with seismic emission volume

    NASA Astrophysics Data System (ADS)

    Niu, F.; Tang, Y.; Chen, H.; TAO, K.; Levander, A.

    2014-12-01

    Recent developments in horizontal drilling and hydraulic fracturing have made it possible to access the reservoirs that are not available for massive production in the past. Hydraulic fracturing is designed to enhance rock permeability and reservoir drainage through the creation of fracture networks. Microseismic monitoring has been proven to be an effective and valuable technology to image hydraulic fracture geometry. Based on data acquisition, seismic monitoring techniques have been divided into two categories: downhole and surface monitoring. Surface monitoring is challenging because of the extremely low signal-to-noise ratio of the raw data. We applied the techniques used in earthquake seismology and developed an integrated monitoring system for mapping hydraulic fractures. The system consists of 20 to 30 state-of-the-art broadband seismographs, which are generally about hundreds times more sensible than regular geophones. We have conducted two experiments in two basins with very different geology and formation mechanism in China. In each case, we observed clear microseismic events, which may correspond to the induced seismicity directly associated with fracturing and the triggered ones at pre-existing faults. However, the magnitude of these events is generally larger than magnitude -1, approximately one to two magnitudes larger than those detected by downhole instruments. Spectrum-frequency analysis of the continuous surface recordings indicated high seismic energy associated with injection stages. The seismic energy can be back-projected to a volume that surrounds each injection stage. Imaging seismic emission volume (SEV) appears to be an effective way to map the stimulated reservior volume, as well as natural fractures.

  3. Investigating the Salton Sea geothermal region using seismic interferometry

    NASA Astrophysics Data System (ADS)

    Matzel, E.

    2011-12-01

    Seismic interferometry has proven to be a powerful method for imaging the Earth's interior. To date, much of the work in seismic interferometry has used ambient noise correlation, which isolates the seismic energy between pairs of seismometers. This has resulted in sharp images of the crust and upper mantle, particularly in areas with dense seismic networks. Curtis et al. (2009) demonstrated that we can reverse the geometry of the problem to focus instead on the energy between pairs of earthquakes. The Virtual Seismometer method (VSM) involves correlating the coda of pairs of events recorded at individual stations and then stacking the results over all stations to obtain an estimate of the Green's function between the sources. By effectively replacing each earthquake with a "virtual station" recording all the others, VSM isolates the portion of the data that is sensitive to the source region and significantly improves our ability to see into tectonically active features. VSM is proving to be a powerful method for studying individual earthquakes and the source region. Using this technique, we are able to recover the expected Green's function between pairs of earthquakes, relocate the earthquakes in time and space, measure the source-time function and source magnitude, and finally image the structure along the path between them. Here we investigate the capability of seismic interferometry for geothermal studies. First, we apply ambient noise correlation to dozens of vertical component seismic stations in Southern California with a particular focus on the Salton Sea geothermal fields. We use these correlations to create a 3 dimensional model of the crust in the region. We then apply VSM to well located earthquakes and explosions in the region to determine the scalability of that technique to very small magnitude events recorded by nearby seismic networks. Of particular interest are the highest frequencies and smallest magnitudes the VSM can resolve.

  4. Seismic switch for strong motion measurement

    DOEpatents

    Harben, P.E.; Rodgers, P.W.; Ewert, D.W.

    1995-05-30

    A seismic switching device is described that has an input signal from an existing microseismic station seismometer and a signal from a strong motion measuring instrument. The seismic switch monitors the signal level of the strong motion instrument and passes the seismometer signal to the station data telemetry and recording systems. When the strong motion instrument signal level exceeds a user set threshold level, the seismometer signal is switched out and the strong motion signal is passed to the telemetry system. The amount of time the strong motion signal is passed before switching back to the seismometer signal is user controlled between 1 and 15 seconds. If the threshold level is exceeded during a switch time period, the length of time is extended from that instant by one user set time period. 11 figs.

  5. Seismic switch for strong motion measurement

    DOEpatents

    Harben, Philip E.; Rodgers, Peter W.; Ewert, Daniel W.

    1995-01-01

    A seismic switching device that has an input signal from an existing microseismic station seismometer and a signal from a strong motion measuring instrument. The seismic switch monitors the signal level of the strong motion instrument and passes the seismometer signal to the station data telemetry and recording systems. When the strong motion instrument signal level exceeds a user set threshold level, the seismometer signal is switched out and the strong motion signal is passed to the telemetry system. The amount of time the strong motion signal is passed before switching back to the seismometer signal is user controlled between 1 and 15 seconds. If the threshold level is exceeded during a switch time period, the length of time is extended from that instant by one user set time period.

  6. Gran Canaria temporary broadband seismic network: an study of the seismicity and Earth structure

    NASA Astrophysics Data System (ADS)

    Almendros, Javier; de Lis Mancilla, Flor; Martinez-Arevalo, Carmen; Carmona, Enrique; Sanchez, Nieves; Heit, Benjamin; Garcia, Alicia; Martin-Leon, Rosa; Buontempo, Luisa; Yuan, Xiahoui

    2010-05-01

    The present project is a joint effort between different institutions to deploy a dense seismic network at Gran Canaria island (Canary Islands, Spain). The interstation distance is around 20 km. The broadband seismic network is composed of one permanent (Guralp CMG-3T 120 s) and five temporary stations (Guralp CMG-3ESP 60 s). The permanent station is a 120 s Guralp CMG-3T and belongs to the Canary Island Seismic Network, run by the Instituto Geográfico Nacional (IGN) of Spain. The temporary stations are 60 s Guralp CMG-3ESP, provided by the GFZ seismic pool. The deployment was carried out in December 2009. The stations will be recording during two years. The improvement of the seismic network allow us to tackle the following issues: the detection and analysis of any local seismicity of tectonic and/or volcanic origin at Gran Canaria island; to contribute to the understanding of the regional seismicity with special interest in the oceanic channel between Tenerife and Gran Canaria Island in collaboration with a project running a dense temporary seismic network in Tenerife; to study the crustal and upper mantle structure, under Gran Canaria to constrain the crustal structure, the source of the volcanism, and better sample the mantle discontinuities and anisotropy. To study the Earth structure, we use receiver function analysis, ambient seismic noise and SKS anisotropy techniques, This project is part of a long-term research of the crustal and the mantle structure of the Canary Islands, which has started with Gran Canaria and Tenerife Islands and will eventually continue with the rest of the archipelago. The origin of the Canary Islands is generally attributed to a broad mantle upwelling under a slow moving plate, resulting in spatially and temporally distributed volcanic activity and a large number of seamounts and islands. A controversial discussion has been going on about the factors that control the evolution of the volcanic edifices, the type of the melting

  7. 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

  8. Small Arrays for Seismic Intruder Detections: A Simulation Based Experiment

    NASA Astrophysics Data System (ADS)

    Pitarka, A.

    2014-12-01

    Seismic sensors such as geophones and fiber optic have been increasingly recognized as promising technologies for intelligence surveillance, including intruder detection and perimeter defense systems. Geophone arrays have the capability to provide cost effective intruder detection in protecting assets with large perimeters. A seismic intruder detection system uses one or multiple arrays of geophones design to record seismic signals from footsteps and ground vehicles. Using a series of real-time signal processing algorithms the system detects, classify and monitors the intruder's movement. We have carried out numerical experiments to demonstrate the capability of a seismic array to detect moving targets that generate seismic signals. The seismic source is modeled as a vertical force acting on the ground that generates continuous impulsive seismic signals with different predominant frequencies. Frequency-wave number analysis of the synthetic array data was used to demonstrate the array's capability at accurately determining intruder's movement direction. The performance of the array was also analyzed in detecting two or more objects moving at the same time. One of the drawbacks of using a single array system is its inefficiency at detecting seismic signals deflected by large underground objects. We will show simulation results of the effect of an underground concrete block at shielding the seismic signal coming from an intruder. Based on simulations we found that multiple small arrays can greatly improve the system's detection capability in the presence of underground structures. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

  9. High-Resolution Analysis of Seismic Air Gun Impulses and Their Reverberant Field as Contributors to an Acoustic Environment.

    PubMed

    Guerra, Melania; Dugan, Peter J; Ponirakis, Dimitri W; Popescu, Marian; Shiu, Yu; Rice, Aaron N; Clark, Christopher W

    2016-01-01

    In September and October 2011, a seismic survey took place in Baffin Bay, Western Greenland, in close proximity to a marine protected area (MPA). As part of the mitigation effort, five bottom-mounted marine acoustic recording units (MARUs) collected data that were used for the purpose of measuring temporal and spectral features from each impulsive event, providing a high-resolution record of seismic reverberation persistent after the direct impulse. Results were compared with ambient-noise levels as computed after the seismic survey to evidence that as a consequence of a series of repeating seismic impulses, sustained elevated levels create the potential for masking. PMID:26610981

  10. Seismic unrest at Katla Volcano- southern Iceland

    NASA Astrophysics Data System (ADS)

    jeddi, zeinab; Tryggvason, Ari; Gudmundsson, Olafur; Bödvarsson, Reynir; SIL Seismology Group

    2014-05-01

    Katla volcano is located on the propagating Eastern Volcanic Zone (EVZ) in South Iceland. It is located beneath Mýrdalsjökull ice-cap which covers an area of almost 600 km2, comprising the summit caldera and the eruption vents. 20 eruptions between 930 and 1918 with intervals of 13-95 years are documented at Katla which is one of the most active subglacial volcanoes in Iceland. Eruptions at Katla are mainly explosive due to the subglacial mode of extrusion and produce high eruption columns and catastrophic melt water floods (jökulhlaups). The present long Volcanic repose (almost 96 years) at Katla, the general unrest since 1955, and the 2010 eruption of the neighbouring Eyjafjallajökull volcano has prompted concerns among geoscientists about an imminent eruption. Thus, the volcano has been densely monitored by seismologists and volcanologists. The seismology group of Uppsala University as a partner in the Volcano Anatomy (VA) project in collaboration with the University of Iceland and the Icelandic Meteorological Office (IMO) installed 9 temporary seismic stations on and around the Mýrdalsjökull glacier in 2011. Another 10 permanent seismic stations are operated by IMO around Katla. The project's data collection is now finished and temporary stations were pulled down in August 2013. According to seismicity maps of the whole recording period, thousands of microearthquakes have occurred within the caldera region. At least three different source areas are active in Katla: the caldera region, the western Godaland region and a small cluster at the southern rim of Mýrdalsjökull near the glacial stream of Hafursarjökull. Seismicity in the southern flank has basically started after June 2011. The caldera events are mainly volcano-tectonic, while western and southern events are mostly long period (lp) and can be related to glacial or magmatic movement. One motivation of the VA Katla project is to better understand the physical mechanism of these lp events. Changes

  11. Mobile seismic exploration

    NASA Astrophysics Data System (ADS)

    Dräbenstedt, A.; Cao, X.; Polom, U.; Pätzold, F.; Zeller, T.; Hecker, P.; Seyfried, V.; Rembe, C.

    2016-06-01

    Laser-Doppler-Vibrometry (LDV) is an established technique to measure vibrations in technical systems with picometer vibration-amplitude resolution. Especially good sensitivity and resolution can be achieved at an infrared wavelength of 1550 nm. High-resolution vibration measurements are possible over more than 100 m distance. This advancement of the LDV technique enables new applications. The detection of seismic waves is an application which has not been investigated so far because seismic waves outside laboratory scales are usually analyzed at low frequencies between approximately 1 Hz and 250 Hz and require velocity resolutions in the range below 1 nm/s/√Hz. Thermal displacements and air turbulence have critical influences to LDV measurements at this low-frequency range leading to noise levels of several 100 nm/√Hz. Commonly seismic waves are measured with highly sensitive inertial sensors (geophones or Micro Electro-Mechanical Sensors (MEMS)). Approaching a laser geophone based on LDV technique is the topic of this paper. We have assembled an actively vibration-isolated optical table in a minivan which provides a hole in its underbody. The laser-beam of an infrared LDV assembled on the optical table impinges the ground below the car through the hole. A reference geophone has detected remaining vibrations on the table. We present the results from the first successful experimental demonstration of contactless detection of seismic waves from a movable vehicle with a LDV as laser geophone.

  12. Nonstructural seismic restraint guidelines

    SciTech Connect

    Butler, D.M.; Czapinski, R.H.; Firneno, M.J.; Feemster, H.C.; Fornaciari, N.R.; Hillaire, R.G.; Kinzel, R.L.; Kirk, D.; McMahon, T.T.

    1993-08-01

    The Nonstructural Seismic Restraint Guidelines provide general information about how to secure or restrain items (such as material, equipment, furniture, and tools) in order to prevent injury and property, environmental, or programmatic damage during or following an earthquake. All SNL sites may experience earthquakes of magnitude 6.0 or higher on the Richter scale. Therefore, these guidelines are written for all SNL sites.

  13. 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.

  14. Geothermal induced seismicity program plan

    SciTech Connect

    Not Available

    1981-03-01

    A plan for a National Geothermal Induced Seismicity Program has been prepared in consultation with a panel of experts from industry, academia, and government. The program calls for baseline seismic monitoring in regions of known future geothermal development, continued seismic monitoring and characterization of earthquakes in zones of geothermal fluid production and injection, modeling of the earthquake-inducing mechanism, and in situ measurement of stresses in the geothermal development. The Geothermal Induced Seismicity Program (GISP) will have as its objectives the evaluation of the seismic hazard, if any, associated with geothermal resource exploitation and the devising of a technology which, when properly utilized, will control or mitigate such hazards.

  15. Short-term seismic quiescence immediately preceding explosions during the 2011 eruption of Telica Volcano, Nicaragua

    NASA Astrophysics Data System (ADS)

    Rodgers, M.; Roman, D. C.; Geirsson, H.; La Femina, P. C.; Muñoz, A.; Tenorio, V.

    2013-12-01

    Telica Volcano, Nicaragua, experienced a VEI 2 eruptive episode from March-June 2011. The eruption consisted of numerous small to moderate ash explosions, many of which were observed visually and recorded by a local broadband seismic network (the TESAND network). Seismicity at Telica during both background and eruptive periods is characterized by generally high and variable rates of low-magnitude volcano-seismic events. Explosions at Telica are also detected seismically and distinguished from volcanic earthquakes by the length of the seismic signal, their emergent nature and 'cigar-shaped' envelope, and broadband spectral content. During the month of May 2011, we identified 16 explosion events on a seismometer located 0.5 km from the crater vent, some of which correlate with visually observed explosions. From May 1-12, ten explosions are apparent in continuous seismic data. During this period, the rate of volcano-seismic events is relatively low (0-20 events/hour with an average of 4 events per hour). Prior to eight of the 10 explosions, there were no detected seismic events within one hour of the explosion. From May 13-31, seven explosions were identified in the continuous seismic data. During this period, the rate of volcano-seismic events is relatively high (0-48 events per hour, with an average of 18 events per hour). In the hour preceding all seven explosions, there were no detected volcano-seismic events. Visual inspection of the continuous seismic data confirms that a strong decrease in the number of volcano-seismic events immediately preceded most of the 2011 explosions at Telica Volcano. We suggest that the apparent short-term decrease in seismicity before explosions at Telica is related to a cycle of pressure buildup and release in the shallow magmatic-hydrothermal system, with an increase in pressure prior to the explosions both resulting from and reflecting constriction of gas pathways.

  16. Annual Hanford Seismic Report for Fiscal Year 2008

    SciTech Connect

    Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E.; Devary, Joseph L.

    2008-12-29

    The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The HSAP is responsible for locating and identifying sources of seismic activity and monitoring changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the HSAP works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 44 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. During fiscal year 2008, the Hanford Seismic Network recorded 1431 triggers on the seismometer system, which included 112 seismic events in the southeast Washington area and an additional 422 regional and teleseismic events. There were 74 events determined to be local earthquakes relevant to the Hanford Site. The highest-magnitude event (3.7 Mc) occurred on May 18, 2008, and was located approximately 17 km east of Prosser at a depth of 20.5 km. With regard to the depth distribution, 13 earthquakes were located at shallow depths (less than 4 km, most likely in the Columbia River basalts), 45 earthquakes were located at intermediate depths (between 4 and 9 km, most likely in the pre-basalt sediments), and 16 earthquakes were located at depths greater than 9 km, within the crystalline basement. Geographically, 54 earthquakes were located in swarm areas and 20 earthquakes were classified as random events. The May 18 earthquake was the highest magnitude event recorded since 1975 in the vicinity of the Hanford Site (between 46 degrees and 47 degrees north latitude and

  17. Advances in Over-Sea-Ice Seismic Reflection Surveys

    NASA Astrophysics Data System (ADS)

    Speece, M. A.; Pekar, S. F.; Williams, B. P.; Sunwall, D. A.; Alesandrini, S. M.; Hein, R. H.

    2009-12-01

    During the austral spring-summers of 2005, 2007, and 2008 a series of over-sea-ice seismic reflection data sets were recorded over McMurdo Sound, Antarctica, in support of the ANtarctic geological DRILLing program (ANDRILL). These surveys incorporated techniques that improved the quality of over-sea-ice seismic data. Prior to this work, over-sea-ice seismic experiments had limited success because of poor source coupling caused by thin sea ice, source bubble-pulse effects caused by explosive seismic sources placed in the water column, and ice flexural-mode noise caused by surface sources. To mitigate these problems, a Generator-Injector (GI) air gun was used as the seismic source. The GI gun was lowered into the water column through holes drilled through the sea ice. The GI gun provided good source coupling and minimized the source bubble effects and flexural mode problems that had plagued previous over-sea-ice experiments. In addition, the GI gun allows for source repetition which is a significant advantage in minimizing wind noise though source summing. A 60-channel seismic snowstreamer consisting of vertically oriented gimbaled geophones with 25-m takeout spacing was employed during these surveys to aid rapid data collection during the normal-incident seismic surveying portions of these projects. A new recording platform and compressor that were added in 2008 have significantly increased production. As experience has been gained, improvements in the recognition of and correction for timing and statics problems, inherent in over-sea-ice seismic data collection, have resulted in better resolution and overall data quality. For instance, thin, soft, low-amplitude pelagic sediment at the ocean bottom have been imaged with high-resolution at a water depth of 900 m. In addition to the surface profiling, a three-component Vertical Seismic Profile (VSP) seismic survey was conducted in 2007 at the newly-drilled ANDRILL Southern McMurdo Sound (SMS) Project borehole. The VSP

  18. Third Quater Seismic Report for Fiscal Year 2007

    SciTech Connect

    Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E.; Devary, Joseph L.

    2007-09-19

    The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The Hanford Seismic Assessment Team locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 41 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. For the Hanford Seismic Network, 16 local earthquakes were recorded during the third quarter of fiscal year 2007. The largest event (magnitude 2.0) occurred on April 16, 2007 and was located 4 km southwest of the 400 Area in the Columbia River basalts at a depth of approximately 3 km. Stratigraphically, 7 earthquakes occurred in the Columbia River basalts (approximately 0-5 km depth), 1 earthquake in the pre-basalt sediments (approximately 5-10 km depth), and 8 earthquakes in the crystalline basement (approximately 10-25 km depth). Geographically, 8 earthquakes occurred in swarm areas, and 8 earthquakes were classified as random events. The Hanford SMA network was triggered on the 300 Area and the 400 Area SMA by the 2.0 Mc seismic event that occurred on April 16, 2007. The maximum vertical acceleration was 0.07 % g and the maximum horizontal acceleration was 0.05% g at the 300 Area SMA, 13.5 km from the event. At the 400 Area SMA, only 5.2 km from the event, the maximum vertical acceleration was 0.25 % g and the maximum horizontal

  19. High Voltage Seismic Generator

    NASA Astrophysics Data System (ADS)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin

    2015-04-01

    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  20. Earthquake dynamics. Mapping pressurized volcanic fluids from induced crustal seismic velocity drops.

    PubMed

    Brenguier, F; Campillo, M; Takeda, T; Aoki, Y; Shapiro, N M; Briand, X; Emoto, K; Miyake, H

    2014-07-01

    Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems. PMID:24994652

  1. Air-coupled seismic waves at long range from Apollo launchings.

    NASA Technical Reports Server (NTRS)

    Donn, W. L.; Dalins, I.; Mccarty, V.; Ewing, M.; Kaschak , G.

    1971-01-01

    Microphones and seismographs were co-located in arrays on Skidaway Island, Georgia, for the launchings of Apollo 13 and 14, 374 km to the south. Simultaneous acoustic and seismic waves were recorded for both events at times appropriate to the arrival of the acoustic waves from the source. The acoustic signal is relatively broadband compared to the nearly monochromatic seismic signal; the seismic signal is much more continuous than the more pulse-like acoustic signal; ground loading from the pressure variations of the acoustic waves is shown to be too small to account for the seismic waves; and the measured phase velocities of both acoustic and seismic waves across the local instrument arrays differ by less than 6 per cent and possibly 3 per cent if experimental error is included. It is concluded that the seismic waves are generated by resonant coupling to the acoustic waves along some 10 km of path on Skidaway Island.

  2. Seismotectonic of Southern Apennines from recent passive seismic experiments

    NASA Astrophysics Data System (ADS)

    Frepoli, A.; Maggi, C.; Cimini, G. B.; Marchetti, A.; Chiappini, M.

    2011-03-01

    We used data of local earthquakes collected during two recent passive seismic experiments carried out in southern Italy in order to study the seismotectonic setting of the Lucanian Apennine and the surrounding areas. Based on continuous recordings of the temporary stations we extracted over 15,600 waveforms, which were hand-picked along with those recorded by the permanent stations of the Italian national seismic network obtaining a dense, high-quality dataset of P- and S-arrival times. We examined the seismicity occurring in the period 2001-2008 by relocating 566 out of 1047 recorded events with magnitudes ML ≥ 1.5 and computing 162 fault-plane solutions. Earthquakes were relocated using a minimum one-dimensional velocity model previously obtained for the region and a Vp/ Vs ratio of 1.83. Background seismicity is concentrated within the upper crust (between 5 and 20 km of depth) and it is mostly clustered along the Lucanian Apennine chain axis. A significant feature extracted from this study relates to the two E-W trending clusters located in the Potentino and in the Abriola-Pietrapertosa sector (central Lucania region). Hypocentral depths in both clusters are slightly deeper than those observed beneath the Lucanian Apennine. We suggest that these two seismic features are representative of the transition from the inner portion of the chain to the external margin characterized by dextral strike-slip kinematics. In the easternmost part of the study area, below the Bradano foredeep and the Apulia foreland, seismicity is generally deeper and more scattered. The sparse seismicity localized in the Sibari Plain, in the offshore area along the northeastern Calabrian coast and in the Taranto Gulf is also investigated thanks to the new recordings. This seismicity shows hypocenters between 12 and 20 km of depth below the Sibari Plain and is deeper (foci between 10 and 35 km of depth) in the offshore area of the Taranto Gulf. 102 well-constrained fault-plane solutions

  3. Intermediate depth seismicity - a reflection seismic approach

    NASA Astrophysics Data System (ADS)

    Haberland, C.; Rietbrock, A.

    2004-12-01

    During subduction the descending oceanic lithosphere is subject to metamorphic reactions, some of them associated with the release of fluids. It is now widely accepted, that these reactions and associated dehydration processes are directly related with the generation of intermediate depth earthquakes (dehydration embrittlement). However, the structure of the layered oceanic plate at depth and the location of the earthquakes relative to structural units of the subducting plate (sources within the oceanic crust and/or in the upper oceanic mantle lithosphere?) are still not resolved yet. This is in mainly due to the fact that the observational resolution needed to address these topics (in the range of only a few kilometers) is hardly achieved in field experiments and related studies. Here we study the wavefields of intermediate depth earthquakes typically observed by temporary networks in order to assess their high-resolution potential in resolving structure of the down going slab and locus of seismicity. In particular we study whether the subducted oceanic Moho can be detected by the analysis of secondary phases of local earthquakes (near vertical reflection). Due to the irregular geometry of sources and receivers we apply an imaging technique similar to diffraction stack migration. The method is tested using synthetic data both based on 2-D finite difference simulations and 3-D kinematic ray tracing. The accuracy of the hypocenter location and onset times crucial for the successful application of stacking techniques (coherency) was achieved by the use of relatively relocated intermediate depth seismicity. Additionally, we simulate the propagation of the wavefields at larger distance (wide angle) indicating the development of guided waves traveling in the low-velocity waveguide associated with the modeled oceanic crust. We also present application on local earthquake data from the South American subduction zone.

  4. Seismic performance of a novel 3D isolation system on continuous bridges

    NASA Astrophysics Data System (ADS)

    Ou, J. P.; Jia, J. F.

    2010-04-01

    Remarkable vertical seismic motion is one of the prominent characteristics of the near-fault earthquake motions, but the traditional and widely used base isolation system only can effectively mitigate horizontal seismic responses and structural damage. A promising three-dimensional (3D) seismic isolation bearing, consisting of laminated rubber bearing with lead core (LRB) and combined coned disc spring with vertical energy dissipation device (e.g., inner fluid viscous cylindric damper or steel damper), was proposed to mitigate horizontal and vertical structural seismic responses simultaneously and separately. Three-group seismic ground motion records were selected to validate the effectiveness of the proposed 3D seismic isolation bearing on a continuous slab bridge. The appropriate damping of the vertical damping device was presented by parametric study. The analyses results showed that the proposed 3D isolation bearing is essentially effective to mitigate vertical and horizontal structural seismic response simultaneously. Near-fault pulse-type seismic motions should be considered in seismic isolation design and evaluation. The proper damping ratio of the vertical damping device should be 20%-30% for favorable vertical isolation effectiveness. The proposed 3D seismic isolation bearing is promising to be applied to the mediate-to-short span bridge and even some building structures.

  5. New seismic events identified in the Apollo lunar data by application of a Hidden Markov Model

    NASA Astrophysics Data System (ADS)

    Knapmeyer-Endrun, B.; Hammer, C.

    2015-10-01

    The Apollo astronauts installed seismic stations on the Moon during Apollo missions 11, 12, 14, 15 and 16. The stations consisted of a three-component long- period seismometer (eigenperiod 15 s) and a vertical short-period sensor (eigenperiod 1 s). Until today, the Apollo seismic network provides the only confirmed recordings of seismic events from any extrater-restrial. The recorded event waveforms differ significantly from what had been expected based on Earth data, mainly by their long duration body wave codas caused by strong near-surface scattering and weak attenuation due to lack of fluids. The main lunar event types are deep moonquakes, impacts, and the rare shallow moonquakes.

  6. Calibration of Seismic Attributes for Reservoir Characterization

    SciTech Connect

    Wayne D. Pennington

    2002-09-29

    The project, "Calibration of Seismic Attributes for Reservoir Characterization," is now complete. Our original proposed scope of work included detailed analysis of seismic and other data from two to three hydrocarbon fields; we have analyzed data from four fields at this level of detail, two additional fields with less detail, and one other 2D seismic line used for experimentation. We also included time-lapse seismic data with ocean-bottom cable recordings in addition to the originally proposed static field data. A large number of publications and presentations have resulted from this work, inlcuding several that are in final stages of preparation or printing; one of these is a chapter on "Reservoir Geophysics" for the new Petroleum Engineering Handbook from the Society of Petroleum Engineers. Major results from this project include a new approach to evaluating seismic attributes in time-lapse monitoring studies, evaluation of pitfalls in the use of point-based measurements and facies classifications, novel applications of inversion results, improved methods of tying seismic data to the wellbore, and a comparison of methods used to detect pressure compartments. Some of the data sets used are in the public domain, allowing other investigators to test our techniques or to improve upon them using the same data. From the public-domain Stratton data set we have demonstrated that an apparent correlation between attributes derived along 'phantom' horizons are artifacts of isopach changes; only if the interpreter understands that the interpretation is based on this correlation with bed thickening or thinning, can reliable interpretations of channel horizons and facies be made. From the public-domain Boonsville data set we developed techniques to use conventional seismic attributes, including seismic facies generated under various neural network procedures, to subdivide regional facies determined from logs into productive and non-productive subfacies, and we developed a

  7. CALIBRATION OF SEISMIC ATTRIBUTES FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Wayne D. Pennington; Horacio Acevedo; Aaron Green; Joshua Haataja; Shawn Len; Anastasia Minaeva; Deyi Xie

    2002-10-01

    The project, ''Calibration of Seismic Attributes for Reservoir Calibration,'' is now complete. Our original proposed scope of work included detailed analysis of seismic and other data from two to three hydrocarbon fields; we have analyzed data from four fields at this level of detail, two additional fields with less detail, and one other 2D seismic line used for experimentation. We also included time-lapse seismic data with ocean-bottom cable recordings in addition to the originally proposed static field data. A large number of publications and presentations have resulted from this work, including several that are in final stages of preparation or printing; one of these is a chapter on ''Reservoir Geophysics'' for the new Petroleum Engineering Handbook from the Society of Petroleum Engineers. Major results from this project include a new approach to evaluating seismic attributes in time-lapse monitoring studies, evaluation of pitfalls in the use of point-based measurements and facies classifications, novel applications of inversion results, improved methods of tying seismic data to the wellbore, and a comparison of methods used to detect pressure compartments. Some of the data sets used are in the public domain, allowing other investigators to test our techniques or to improve upon them using the same data. From the public-domain Stratton data set we have demonstrated that an apparent correlation between attributes derived along ''phantom'' horizons are artifacts of isopach changes; only if the interpreter understands that the interpretation is based on this correlation with bed thickening or thinning, can reliable interpretations of channel horizons and facies be made. From the public-domain Boonsville data set we developed techniques to use conventional seismic attributes, including seismic facies generated under various neural network procedures, to subdivide regional facies determined from logs into productive and non-productive subfacies, and we developed a

  8. 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

  9. 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

  10. Seismic local site effects characterization in the Andarax River Valley (SE Spain) from ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Carmona, Enrique; García-Jerez, Antonio; Luzón, Francisco; Sánchez-Martos, Francisco; Sánchez-Sesma, Francisco J.; Piña, José

    2014-05-01

    This work is focused on the characterization of seismic local effects in the Low Andarax River Valley (SE Spain). The Low Andarax River valley is located in an active seismic region, with the higher seismic hazard values in Spain. The landform is composed mainly by sedimentary materials which increase its seismic hazard due to the amplification of the seismic inputs and spectral resonances. We study seismic local effects in the Low Andarax River by analyzing the Horizontal-to-Vertical Spectral Ratio (HVSR) of ambient noise records. The noise data were recorded during two field campaigns in 2012 and 2013. There have been a total of 374 noise measurements with 15 and 30 minutes duration. The acquisition was performed with a Digital Broadband Seismometer Guralp CMG-6TD. The distance between measurements was about 200 meters, covering an area around 40 km2. There have been 6 significant peak frequencies between 0.3 Hz and 5 Hz. It was possible to find interesting areas with similar spectral peaks that coincide with zones with similar microgravimetric anomalies at the alluvial valley. It is also observed a decrease in the frequency peaks from West to East suggesting increased sediment layer. We also compute the soil models at those sites where geotechnical information is available, assuming that the seismic noise is diffuse. We invert the HVSR for these places using horizontally layered models and in the imaginary part the Green functions at the source. It is observed that the S wave velocity inverted models are consistent with the known geotechnical information obtained from drilled boreholes. We identify the elastodynamic properties of the limestone-dolomite materials with a formation of phyllites and quartzite that form the basement of the depression, and those properties of the Miocene and Pliocene detrital deposits (marls, sandy silts, sands and conglomerates) that fill the valley. These results together with the observed resonant frequencies along the Andarax

  11. Third Quarter Hanford Seismic Report for Fiscal Year 2010

    SciTech Connect

    Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E.; Devary, Joseph L.

    2010-09-29

    The Hanford Seismic Assessment Program (HSAP) provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network for the U.S. Department of Energy and its contractors. The HSAP is responsible for locating and identifying sources of seismic activity and monitoring changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, natural phenomena hazards assessments, and engineering design and construction. In addition, the HSAP works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The Hanford Seismic Network and the Eastern Washington Regional Network consist of 44 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Assessment Team. The Hanford Seismic Network recorded 23 local earthquakes during the third quarter of FY 2010. Sixteen earthquakes were located at shallow depths (less than 4 km), five earthquakes at intermediate depths (between 4 and 9 km), most likely in the pre-basalt sediments, and two earthquakes were located at depths greater than 9 km, within the basement. Geographically, twelve earthquakes were located in known swarm areas, 3 earthquakes occurred near a geologic structure (Saddle Mountain anticline), and eight earthquakes were classified as random events. The highest magnitude event (3.0 Mc) was recorded on May 8, 2010 at depth 3.0 km with epicenter located near the Saddle Mountain anticline. Later in the quarter (May 24 and June 28) two additional earthquakes were also recorded nearly at the same location. These events are not considered unusual in that earthquakes have been previously recorded at this location, for example, in October 2006 (Rohay et al; 2007). Six earthquakes were detected in the vicinity of Wooded Island, located about eight miles north of Richland just

  12. Observations and Modeling of Seismic Background Noise

    USGS Publications Warehouse

    Peterson, Jon R.

    1993-01-01

    INTRODUCTION The preparation of this report had two purposes. One was to present a catalog of seismic background noise spectra obtained from a worldwide network of seismograph stations. The other purpose was to refine and document models of seismic background noise that have been in use for several years. The second objective was, in fact, the principal reason that this study was initiated and influenced the procedures used in collecting and processing the data. With a single exception, all of the data used in this study were extracted from the digital data archive at the U.S. Geological Survey's Albuquerque Seism