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Real-time earthquake alert system for the greater San Francisco Bay Area: a prototype design to address operational issues

Description: The purpose of the earthquake alert system (EAS) is to outrun the seismic energy released in a large earthquake using a geographically distributed network of strong motion sensors that telemeter data to a rapid CPU-processing station, which then issues an area-wide warning to a region before strong motion will occur. The warning times involved are short, from 0 to 30 seconds or so; consequently, most responses must be automated. The San Francisco Bay Area is particularly well suited for an EAS because (1) large earthquakes have relatively shallow hypocenters (10- to 20-kilometer depth), giving favorable ray-path geometries for larger warning times than deeper from earthquakes, and (2) the active faults are few in number and well characterized, which means far fewer geographically distributed strong motion sensors are (about 50 in this region). An EAS prototype is being implemented in the San Francisco Bay Area. The system consists of four distinct subsystems: (1) a distributed strong motion seismic network, (2) a central processing station, (3) a warning communications system and (4) user receiver and response systems. We have designed a simple, reliable, and inexpensive strong motion monitoring station that consists of a three-component Analog Devices ADXLO5 accelerometer sensing unit, a vertical component weak motion sensor for system testing, a 16-bit digitizer with multiplexing, and communication output ports for RS232 modem or radio telemetry. The unit is battery-powered and will be sited in fire stations. The prototype central computer analysis system consists of a PC dam-acquisition platform that pipes the incoming strong motion data via Ethernet to Unix-based workstations for dam processing. Simple real-time algorithms, particularly for magnitude estimation, are implemented to give estimates of the time since the earthquake`s onset its hypocenter location, its magnitude, and the reliability of the estimate. These parameters are calculated and transmitted with frequent updates as ...
Date: December 10, 1996
Creator: Harben, P.E.; Jarpe, S. & Hunter, S.
Partner: UNT Libraries Government Documents Department

Seismic-source corner frequencies from the depth of burial experiment

Description: The results from the depth of burial experiment (DOB) are consistent with cube-root scaling and with previous observations that the source corner frequency for underground explosions increases with depth. The corner frequencies, however, were overpredicted by Mueller and Murphy (1971) and underpredicted by Denny and Johnson (1991).
Date: November 23, 1998
Creator: Denny, M.D.
Partner: UNT Libraries Government Documents Department

Preliminary regional magnitude in the Middle East Region using narrowband Lg coda envelopes

Description: Because many regional seismic discriminants are functions of magnitude, it is important to obtain a stable measurement especially for smaller events that will likely have very limited station coverage. We have collected and analyzed regional broad band waveforms from stations in the middle east region for the purpose of calibrating a stable regional magnitude scale that can be applied to events that are too small to detect teleseismically. Our approach is to obtain frequency-dependent empirical Greens function coda envelopes for narrow frequency bands that can be used to correct for gross path effects. We make the assumption that the moment-rate spectra are generally flat below{approximately}2 Hz for these events smaller than Mw{approximately}3.5. In a least squares sense, we obtain frequency-dependent corrections to the Lg coda measurements to fit the scalar moment estimates. These frequency-dependent corrections remove the effects of the S-to-Lg coda transfer function, thus correcting back to the S-wave source spectra. Due to the averaging nature of Lg coda waves we are then able to obtain a stable single-station estimate of the source spectra.To avoid regional biases we tie our coda envelope amplitude measurements to seismic moments obtained from long period 1-D waveform modeling for moderate sized earthquakes (A4w-3.5.- 4.5). Most importantly, we can now apply the same corrections to significantly smaller events that cannot be observed teleseismically. Our empirical approach takes into account scattering,absorption, and waveguide losses as well as frequency-dependent site effects.Moreover, the use of the coda envelope mitigates the undesirable effects of source anisotropy, random site interference, path variability, and directivity that plague direct wave measurements. This approach was successfully applied to other regions where it was observed that the coda-derived Mw estimates showed significantly smaller dependence on lateral path variation and source radiation anisotropy than the more conventional approaches such as mb(Pg),mb(Lg),and teleseismic mb.
Date: July 1, 1997
Creator: Mayeda, K. & Walter, W.R.
Partner: UNT Libraries Government Documents Department

Hanford Seismic Network

Description: This report describes the Hanford Seismic Network. The network consists of two instrument arrays: seismometers and strong motion accelerometers. The seismometers determine the location and magnitude of earthquakes, and the strong motion accelerometers determine ground motion. Together these instruments arrays comply with the intent of DOE Order 5480.20, Natural Phenomena Hazards Mitigation.
Date: May 1, 1997
Creator: Reidel, S.P. & Hartshorn, D.C.
Partner: UNT Libraries Government Documents Department


Description: This annual technical progress report is for part of Task 4 (site evaluation), Task 5 (2D seismic design, acquisition, and processing), and Task 6 (2D seismic reflection, interpretation, and AVO analysis) on DOE contact number DE-AR26-98FT40369. The project had planned one additional deployment to another site other than Savannah River Site (SRS) or DOE Hanford Site. After the SUBCON midyear review in Albuquerque, NM, it was decided that two additional deployments would be performed. The first deployment is to test the feasibility of using non-invasive seismic reflection and AVO analysis as a monitoring tool to assist in determining the effectiveness of Dynamic Underground Stripping (DUS) in removal of DNAPL. The second deployment is to the Department of Defense (DOD) Charleston Naval Weapons Station Solid Waste Management Unit 12 (SWMU-12), Charleston, SC to further test the technique to detect high concentrations of DNAPL. The Charleston Naval Weapons Station SWMU-12 site was selected in consultation with National Energy Technology Laboratory (NETL) and DOD Naval Facilities Engineering Command Southern Division (NAVFAC) personnel. Based upon the review of existing data and due to the shallow target depth, the project team collected three Vertical Seismic Profiles (VSP) and an experimental P-wave seismic reflection line. After preliminary data analysis of the VSP data and the experimental reflection line data, it was decided to proceed with Task 5 and Task 6. Three high resolution P-wave reflection profiles were collected with two objectives; (1) design the reflection survey to image a target depth of 20 feet below land surface to assist in determining the geologic controls on the DNAPL plume geometry, and (2) apply AVO analysis to the seismic data to locate the zone of high concentration of DNAPL. Based upon the results of the data processing and interpretation of the seismic data, the project team was able ...
Date: December 1, 2001
Creator: Waddell, Michael G.; Domoracki, William J. & Temples, Tom J.
Partner: UNT Libraries Government Documents Department

Asynchronous global optimization techniques for medium and large inversion problems

Description: We discuss global optimization procedures adequate for seismic inversion problems. We explain how to save function evaluations (which may involve large scale ray tracing or other expensive operations) by creating a data base of information on what parts of parameter space have already been inspected. It is also shown how a correct parallel implementation using PVM speeds up the process almost linearly with respect to the number of processors, provided that the function evaluations are expensive enough to offset the communication overhead.
Date: April 1, 1995
Creator: Pereyra, V.; Koshy, M. & Meza, J.C.
Partner: UNT Libraries Government Documents Department

The influence of rock material models on seismic discrimination of underground nuclear explosions

Description: We found that the spectral characteristics of the seismic signal from underground explosions were mainly determined by the rock material strength and the gas porosity. Both the unloading characteristics and the amplitude of the ``elastic toe`` are important parameters in the porous model.
Date: June 1, 1995
Creator: Glenn, L.A.
Partner: UNT Libraries Government Documents Department

Characteristics of seismic waves from Soviet peaceful nuclear explosions in salt

Description: The report is carried out by the Institute for Dynamics of the Geospheres, Russian Academy of Sciences under contract NB280344 with Lawrence Livermore National Laboratory, University of California. The work includes investigation of seismic waves generation and propagation from Soviet peaceful underground nuclear explosions in salt based on the data from temporary and permanent seismic stations. The explosions were conducted at the sites Azgir and Vega within the territory of the Caspian depression of the Russian platform. The data used were obtained in the following conditions of conduction: epicentral distance range from 0 to 60 degrees, yields from 1 to 65 kt and depths of burial from 160 to 1500 m.
Date: April 1, 1995
Creator: Adushkin, V.V.; Kaazik, P.B.; Kostyuchenko, V.N.; Kuznetsov, O.P.; Nedoshivin, N.I.; Rubinshtein, K.D. et al.
Partner: UNT Libraries Government Documents Department

Comprehensive study of the seismotectonics of the Aleutian Arc. Annual progress report, March 1, 1973--February 28, 1974

Description: Basic research is carried out to derive a coherent theory for the tectonic structure and geological history of the Alaska-Aleutian island arc in the framework of recent advancements of plate tectonics. An important part of this study is the evaluation of the seismic risk particularly in the eastern Aleutian arc which forms a major section of the active boundary between the North American and Pacific plates. The main effort during the current research term was concentrated on installation of a sufficiently dense and modern seismic station network. Two independent, telemetered networks were installed. One covers the Shumagin Islands region, a section of the eastern Aleutian Arc which was identified from earlier research as a region of susaected high risk for a possible major earthquakes in the not too distant future. Another less concentrated and rather elongated network was installed jointly with the University of Alaska along a roughly 1000 km long section of the eastern Aleutian arc east of longitude 168 deg W including the Alaskan Peninsula. It monitors the regional seismic background activity. Seismic data from these two networks provide the basis for testing physical models which were recently developed in an effort to advance systematic methods for earthquake prediction. (auth)
Date: January 1, 1974
Creator: Jacob, K.H.
Partner: UNT Libraries Government Documents Department

Borehole Seismic Monitoring of Injected CO2 at the Frio Site

Description: As part of a small scale sequestration test (about 1500 tonsof CO2) in a saline aquifer, time-lapse borehole seismic surveys wereconducted to aid in characterization of subsurface CO2 distribution andmaterial property changes induced by the injected CO2. A VSP surveydemonstrated a large increase (about 75 percent) in seismic reflectivitydue to CO2 injection and allowed estimation of the spatial extent of CO2induced changes. A crosswell survey imaged a large seismic velocitydecrease (up to 500 m/s) within the injection interval and provided ahigh resolution image of this velocity change which maps the subsurfacedistribution of CO2 between two wells. Numerical modeling of the seismicresponse uses the crosswell measurements to show that this small CO2volume causes a large response in the seismic reflectivity. This resultdemonstrates that seismic detection of small CO2 volumes in salineaquifers is feasible and realistic.
Date: April 21, 2006
Creator: Daley, Thomas M.; Myer, Larry R.; Hoversten, G.M.; Peterson, JohnE. & Korneev, Valeri A.
Partner: UNT Libraries Government Documents Department

Velocity analysis for transversely isotropic media

Description: The main difficulty in extending seismic processing to anisotropic media is the recovery of anisotropic velocity fields from surface reflection data. Velocity analysis for transversely isotropic (TI) media can be done by inverting the dependence of P-wave moveout velocities on the ray parameter. P-wave NMO velocity in homogeneous TI media with a vertical symmetry axis depends just on the zero-dip value V{sub nmo} and a new effective parameter {eta} that reduces to the difference between Thomsen parameters {epsilon} and {delta} in the limit of weak anisotropy. It is possible to obtain {eta} and reconstruct the NMO velocity as a function of ray parameter using moveout velocities for two different dips. Moreover, V{sub nmo}(0) and {eta} determine not only the NMO velocity, but also also long-spread (nonhyperbollic) P-wave moveout for horizontal reflectors and time-migration impulse response. Inversion of dip-moveout information allows performance of all time-processing steps in TI media using only surface P-wave data. Isotropic time-processing methods remain entirely valid for elliptical anisotropy ({epsilon} = {delta}). Accurate time-to-depth conversion, however, requires the vertical velocity V{sub P0} be resolved independently. If I-P0 is known, then allisotropies {epsilon} and {delta} can be found by inverting two P-wave NMO velocities corresponding to a horizontal and a dipping reflector. If no information is available, all three parameters (V {sub P0}, {epsilon}, and {delta}) can be obtained by combining inversion results with shear-wave information. such as the P-SV or SV-SV wave NMO velocities for a horizontal reflector. Generalization of Tsvankin`s single-layer NMO equation for layered anisotropic media with a dipping reflector provides a basis for extending anisotropic velocity analysis to vertically inhomogeneous media. The influence of a stratified overburden on moveout velocity can be stripped through a Dix-type differentiation procedure.
Date: August 1, 1994
Creator: Alkhalifah, T. & Tsvankin, I.
Partner: UNT Libraries Government Documents Department

Trip Report United Arab Emirates

Description: Keith Nakanishi and Arthur Rodgers traveled to the United Arab Emirates in February, 2004 to continue an on-going technical collaboration with UAE University and to service the two temporary LLNL seismic stations. Nakanishi and Rodgers then participated in the Gulf Seismic Forum, which was organized by LLNL and sponsored by the University of Sharjah.
Date: October 6, 2004
Creator: Nakanishi, K & Rodgers, A
Partner: UNT Libraries Government Documents Department

Preliminary analysis of the International Data Centre pipeline.

Description: The International Data Centre of the Comprehensive Nuclear-Test-Ban Treaty Organization relies on automatic data processing as the first step in identifying seismic events from seismic waveform data. However, more than half of the automatically identified seismic events are eliminated by IDC analysts. Here, an IDC dataset is analyzed to determine if the number of automatically generated false positives could be reduced. Data that could be used to distinguish false positives from analyst-accepted seismic events includes the number of stations, the number of phases, the signal-to-noise ratio, and the pick error. An empirical method is devised to determine whether an automatically identified seismic event is acceptable, and the method is found to identify a significant number of the false positives in IDC data. This work could help reduce seismic analyst workload and could help improve the calibration of seismic monitoring stations. This work could also be extended to address identification of seismic events missed by automatic processing.
Date: July 1, 2009
Creator: Gauthier, John Henry
Partner: UNT Libraries Government Documents Department

Fast 3-D prestack depth migration with a parallel PSPI algorithm. Final report

Description: There was the need for general expertise in the porting of serial seismic reflection code to a parallel processing environment. The project was a continuation of Task Order 38 involving the improvement of existing parallel models developed for that task and to provide support in parallelizing other similar seismic codes to a miasively parallel processor environment.
Date: June 1, 1997
Creator: Roberts, P.M.; Alde, D.M. & House, L.S.
Partner: UNT Libraries Government Documents Department

The Waveform Correlation Event Detection System project, Phase II: Testing with the IDC primary network

Description: Further improvements to the Waveform Correlation Event Detection System (WCEDS) developed by Sandia Laboratory have made it possible to test the system on the accepted Comprehensive Test Ban Treaty (CTBT) seismic monitoring network. For our test interval we selected a 24-hour period from December 1996, and chose to use the Reviewed Event Bulletin (REB) produced by the Prototype International Data Center (PIDC) as ground truth for evaluating the results. The network is heterogeneous, consisting of array and three-component sites, and as a result requires more flexible waveform processing algorithms than were available in the first version of the system. For simplicity and superior performance, we opted to use the spatial coherency algorithm of Wagner and Owens (1996) for both types of sites. Preliminary tests indicated that the existing version of WCEDS, which ignored directional information, could not achieve satisfactory detection or location performance for many of the smaller events in the REB, particularly those in the south Pacific where the network coverage is unusually sparse. To achieve an acceptable level of performance, we made modifications to include directional consistency checks for the correlations, making the regions of high correlation much less ambiguous. These checks require the production of continuous azimuth and slowness streams for each station, which is accomplished by means of FK processing for the arrays and power polarization processing for the three-component sites. In addition, we added the capability to use multiple frequency-banded data streams for each site to increase sensitivity to phases whose frequency content changes as a function of distance.
Date: April 1, 1998
Creator: Young, C.J.; Beiriger, J.I. & Moore, S.G.
Partner: UNT Libraries Government Documents Department

Evaluation of national seismograph network detection capabilities: Final report. Volume 2

Description: This final report presents detection thresholds, detection probabilities, and location error ellipse projections for the US National Seismic Network (USNSN) with and without real-time cooperative stations in the eastern US. Network simulation methods are used with spectral noise levels at stations in the USNSN and other stations to simulate the processes of excitation, propagation, detection, and processing of seismic phases. The USNSN alone should be capable of detecting 4 or more P waves for shallow crustal earthquakes in nearly all of the eastern and central US at the magnitude 3.8 level. When real-time cooperative stations are used in conjunction with the USNSN, the network should be capable of detecting 4 or more P waves from events 0.2 to 0.3 magnitude units lower. The planned expansion of the USNSN and cooperative stations should improve detection levels by an additional 0.2 to 0.3 magnitudes units in many areas. Location uncertainties for the USNSN should be significantly improved by addition of real-time cooperative stations. Median error ellipses for magnitude 4.5 earthquakes in the eastern and central US depend strongly upon location, but uncertainties should be less than 100 square km in the central US and degrade to 200 square km or more offshore and to the south and north of the international boundaries. Close cooperation with the Canadian National Network should substantially improve detection thresholds and location uncertainties along the Canadian border.
Date: October 1, 1997
Creator: McLaughlin, K.L.; Barker, T.G. & Bennett, T.J.
Partner: UNT Libraries Government Documents Department

Seismic signals from underground cavity collapses and other mining-related failures

Description: The sudden collapse of man-made underground cavities have generated seismic signals as large as magnitude 5.4. Collapses are just one of the many types of mining associated seismicity including coalbumps and rockbursts which need to be identified and distinguished from potential clandestine nuclear explosions under the recently signed Comprehensive Test Ban Treaty (CTBT). Collapses, coalbumps and rockbursts are of concern for seismically monitoring a CTBT for a number of reasons. First, they can look like explosions when using some seismic discriminant measures, such M{sub s}:m{sub b}, M{sub o}: m{sub b}, regional P/S ratios and depth. Second, underground nuclear explosions themselves produce cavities that might collapse, possibly aiding in the detection of a clandestine event. Finally, because all mine-related events occur in the vicinity of underground cavities, they may come under special scrutiny because of the concern that very large, specially constructed cavities could be used to evasively decouple a clandestine test. For these reasons mine-related seismicity in both active and former mining regions have the potential to be false alarms under a CTBT. We are investigating techniques to identify collapses, either directly via waveform modeling, or indirectly by combining several seismic discriminants. We are also investigating the source mechanisms of coalbumps and collapses to better understand the performance of seismic discriminants for these events. In particular we have found similarities in point source models of some longwall coalbumps, room- and-pillar mine collapses and NTS nuclear explosion cavity collapses. In order to understand coalbumps we are analyzing events from central Utah recorded at regional distances in Utah and Nevada including at the auxiliary station ELK. Some of these have anomalous, explosion- like high frequency P/S ratios. We are combining this new study with results from previous field work done in 1995 at a Colorado long-wall coal mining operation. Similarly to longwall ...
Date: July 1, 1997
Creator: Walter, W.R.; Heuze, F. & Dodge, D.
Partner: UNT Libraries Government Documents Department

Energy Partitioning of Seismic Waves in Fractured Rocks

Description: Advances in locating and characterizes fractures in oil and gas reservoirs, and at waste isolation sites from seismic surveys requires improved interpretation methods. Experimental and theoretical results from this work have lead to an understanding of diagnostic signatures of energy that is partitioned into body waves and guided modes by fractures. Compressional waves and shear waves (i.e., shear waves with particle motion perpendicular to the fracture plane) are sensitive to changes in shear stress on a pre-existing fracture and to the formation of a fracture in a previously intact specimen. Both types of waves exhibit a shift in frequency content and a change in the amplitude of the wave as a fracture is formed or a pre-existing fracture is closed. The dispersion characteristics of interfact waves that propagate along a fracture enable quantification of fracture specific stiffness. A new compressional-mode interface wave was measured that has the potential for becoming a diagnostic tool for changes in stress in a fracture. The results of this research provide the basis for the development of seismic imaging techniques and analyses tools for locating and characterizing fractures on the field scale.
Date: August 31, 1997
Partner: UNT Libraries Government Documents Department