175 Matching Results

Search Results

Advanced search parameters have been applied.

Source Analysis of the Crandall Canyon, Utah, Mine Collapse

Description: Analysis of seismograms from a magnitude 3.9 seismic event on August 6, 2007 in central Utah reveals an anomalous radiation pattern that is contrary to that expected for a tectonic earthquake, and which is dominated by an implosive component. The results show the seismic event is best modeled as a shallow underground collapse. Interestingly, large transverse surface waves require a smaller additional non-collapse source component that represents either faulting in the rocks above the mine workings or deformation of the medium surrounding the mine.
Date: February 28, 2008
Creator: Dreger, D S; Ford, S R & Walter, W R
Partner: UNT Libraries Government Documents Department


Description: The detection and timing of seismic arrivals play a critical role in the ability to locate seismic events, especially at low magnitude. Errors can occur with the determination of the timing of the arrivals, whether these errors are made by automated processing or by an analyst. One of the major obstacles encountered in properly estimating travel-time picking error is the lack of a clear and comprehensive discussion of all of the factors that influence phase picks. This report discusses possible factors that need to be modeled to properly study phase arrival time picking errors. We have developed a multivariate statistical model, experimental design, and analysis strategy that can be used in this study. We have embedded a general form of the International Data Center(IDC)/U.S. National Data Center (USNDC) phase pick measurement error model into our statistical model. We can use this statistical model to optimally calibrate a picking error model to regional data. A follow-on report will present the results of this analysis plan applied to an implementation of an experiment/data-gathering task.
Date: February 1, 2001
Creator: VELASCO, A. & AL, ET
Partner: UNT Libraries Government Documents Department

Analysis of seismic events in and near Kuwait

Description: Seismic data for events in and around Kuwait were collected and analyzed. The authors estimated event moment, focal mechanism and depth by waveform modeling. Results showed that reliable seismic source parameters for events in and near Kuwait can be estimated from a single broadband three-component seismic station. This analysis will advance understanding of earthquake hazard in Kuwait.
Date: May 11, 1999
Creator: Harris, D B; Mayeda, K M; Rodgers, A J & Ruppert, S D
Partner: UNT Libraries Government Documents Department

Seismic Event Location Using Levenberg-Marquardt Least Squares Inversion

Description: The most widely used algorithm for estimating seismic event hypocenters and origin times is iterative linear least squares inversion. In this paper we review the mathematical basis of the algorithm and discuss the major assumptions made during its derivation. We go on to explore the utility of using Levenberg-Marquardt damping to improve the performance of the algorithm in cases where some of these assumptions are violated. We also describe how location parameter uncertainties are calculated. A technique to estimate an initial seismic event location is described in an appendix.
Date: October 2002
Creator: Ballard, Sanford
Partner: UNT Libraries Government Documents Department

Integrated Seismic Event Detection and Location by Advanced Array Processing

Description: The principal objective of this two-year study is to develop and test a new advanced, automatic approach to seismic detection/location using array processing. We address a strategy to obtain significantly improved precision in the location of low-magnitude events compared with current fully-automatic approaches, combined with a low false alarm rate. We have developed and evaluated a prototype automatic system which uses as a basis regional array processing with fixed, carefully calibrated, site-specific parameters in conjuction with improved automatic phase onset time estimation. We have in parallel developed tools for Matched Field Processing for optimized detection and source-region identification of seismic signals. This narrow-band procedure aims to mitigate some of the causes of difficulty encountered using the standard array processing system, specifically complicated source-time histories of seismic events and shortcomings in the plane-wave approximation for seismic phase arrivals at regional arrays.
Date: February 9, 2007
Creator: Kvaerna, T; Gibbons, S J; Ringdal, F & Harris, D B
Partner: UNT Libraries Government Documents Department

The DOE Model for Improving Seismic Event Locations Using Travel Time Corrections: Description and Demonstration

Description: The U.S. National Laboratories, under the auspices of the Department of Energy, have been tasked with improv- ing the capability of the United States National Data Center (USNDC) to monitor compliance with the Comprehen- sive Test Ban Trea~ (CTBT). One of the most important services which the USNDC must provide is to locate suspicious events, preferably as accurately as possible to help identify their origin and to insure the success of on-site inspections if they are deemed necessary. The seismic location algorithm used by the USNDC has the capability to generate accurate locations by applying geographically dependent travel time corrections, but to date, none of the means, proposed for generating and representing these corrections has proven to be entirely satisfactory. In this presentation, we detail the complete DOE model for how regional calibration travel time information gathered by the National Labs will be used to improve event locations and provide more realistic location error esti- mates. We begin with residual data and error estimates from ground truth events. Our model consists of three parts: data processing, data storage, and data retrieval. The former two are effectively one-time processes, executed in advance before the system is made operational. The last step is required every time an accurate event location is needed. Data processing involves applying non-stationary Bayesian kriging to the residwd data to densifi them, and iterating to find the optimal tessellation representation for the fast interpolation in the data retrieval task. Both the kriging and the iterative re-tessellation are slow, computationally-expensive processes but this is acceptable because they are performed off-line, before any events are to be located. In the data storage task, the densified data set is stored in a database and spatially indexed. Spatial indexing improves the access efficiency of the geographically-ori- ented data requests associated with event ...
Date: October 20, 1998
Creator: Hipp, J.R.; Moore, S.G.; Shepherd, E. & Young, C.J.
Partner: UNT Libraries Government Documents Department

Annual Hanford Seismic Report for Fiscal Year 2007

Description: 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.
Date: December 27, 2007
Creator: Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E. & Devary, Joseph L.
Partner: UNT Libraries Government Documents Department

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

Description: 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.
Date: August 15, 2007
Creator: Ford, S R; Dreger, D S; Walter, W R; Hellweg, M & Urhammer, R
Partner: UNT Libraries Government Documents Department

Development of Simplified Probabilistic Risk Assessment Model for Seismic Initiating Event

Description: ABSTRACT This paper discusses a simplified method to evaluate seismic risk using a methodology built on dividing the seismic intensity spectrum into multiple discrete bins. The seismic probabilistic risk assessment model uses Nuclear Regulatory Commission’s (NRC’s) full power Standardized Plant Analysis Risk (SPAR) model as the starting point for development. The seismic PRA models are integrated with their respective internal events at-power SPAR model. This is accomplished by combining the modified system fault trees from the full power SPAR model with seismic event tree logic. The peak ground acceleration is divided into five bins. The g-value for each bin is estimated using the geometric mean of lower and upper values of that particular bin and the associated frequency for each bin is estimated by taking the difference between upper and lower values of that bin. The component’s fragilities are calculated for each bin using the plant data, if available, or generic values of median peak ground acceleration and uncertainty values for the components. For human reliability analysis (HRA), the SPAR HRA (SPAR-H) method is used which requires the analysts to complete relatively straight forward worksheets that include the performance shaping factors (PSFs). The results are then used to estimate human error probabilities (HEPs) of interest. This work is expected to improve the NRC’s ability to include seismic hazards in risk assessments for operational events in support of the reactor oversight program (e.g., significance determination process).
Date: June 1, 2012
Creator: Khericha, S.; Buell, R.; Sancaktar, S.; Gonzalez, M. & Ferrante, F.
Partner: UNT Libraries Government Documents Department

Mining-induced seismicity at the Lucky Friday Mine: Seismic events of magnitude >2.5, 1989--1994

Description: An understanding of the types of seismic events that occur in a deep mine provides a foundation for assessing the seismic characteristics of these events and the degree to which initiation of these events can be anticipated or controlled. This study is a first step toward developing such an understanding of seismic events generated by mining in the Coeur d`Alene Mining District of northern Idaho. It is based on information developed in the course of a long-standing rock burst research effort undertaken by the U. S. Bureau of Mines in cooperation with Coeur d`Alene Mining District mines and regional universities. This information was collected for 39 seismic events with local magnitudes greater than 2.5 that occurred between 1989 and 1994. One of these events occurred, on average, every 8 weeks during the study period. Five major types of characteristic events were developed from the data; these five types describe all but two of the 39 events that were studied. The most common types of events occurred, on average, once every 30 weeks. The characteristic mechanisms, first-motion patterns, damage patterns, and relationships to mining and major geologic structures were defined for each type of event. These five types of events need to be studied further to assess their ability to camouflage clandestine nuclear tests as well as the degree to which they can be anticipated and controlled.
Date: September 1, 1996
Creator: Whyatt, J.K.; Williams, T.J.; Blake, W.; Sprenke, K. & Wideman, C.
Partner: UNT Libraries Government Documents Department

Institute of Geophyics and Planetary Physics. Annual report for FY 1994

Description: The Institute of Geophysics and Planetary Physics (IGPP) is a Multicampus Research Unit of the University of California (UC). IGPP was founded in 1946 at UC Los Angeles with a charter to further research in the earth and planetary sciences and in related fields. The Institute now has branches at UC campuses in Los Angeles, San Diego, Riverside, and Irvine and at Los Alamos and Lawrence Livermore national laboratories. The University-wide IGPP has played an important role in establishing interdisciplinary research in the earth and planetary sciences. For example, IGPP was instrumental in founding the fields of physical oceanography and space physics, which at the time fell between the cracks of established university departments. Because of its multicampus orientation, IGPP has sponsored important interinstitutional consortia in the earth and planetary sciences. Each of the six branches has a somewhat different intellectual emphasis as a result of the interplay between strengths of campus departments and Laboratory programs. The IGPP branch at Lawrence Livermore National Laboratory (LLNL) was approved by the Regents of the University of California in 1982. IGPP-LLNL emphasizes research in seismology, geochemistry, cosmochemistry, high-pressure sciences, and astrophysics. It provides a venue for studying the fundamental aspects of these fields, thereby complementing LLNL programs that pursue applications of these disciplines in national security and energy research. IGPP-LLNL is directed by Charles Alcock and is structured around three research centers. The Center for Geosciences, headed by George Zandt and Frederick Ryerson, focuses on research in geophysics and geochemistry. The Center for High-Pressure Sciences, headed by William Nellis, sponsors research on the properties of planetary materials and on the synthesis and preparation of new materials using high-pressure processing.
Date: September 29, 1995
Creator: Ryerson, F.J.
Partner: UNT Libraries Government Documents Department

High resolution surface wave dispersion studies in China

Description: The Los Alamos National Laboratory regional calibration project is actively assembling a database of surface-wave dispersion information for China and surrounding areas. As part of the effort to characterize surface wave dispersion in China, we integrate prior long period results from the University of Colorado with our shorter period dispersion measurements in a high resolution survey of key monitoring areas. Focusing on western China initially, we employ broadband data recorded on CDSN stations, and regional events (m{sub b} 4 and above). Our approach is twofold, employing path specific calibration of key stations and well-recorded reference events, and tomographic inference to provide group velocity curves for regions with sparse station distribution and little seismic activity. Initial dispersion studies at Chinese stations WMQ and LZH show substantial azimuthal variation in dispersion, reinforcing the need for careful determination of source regions for path-specific calibration.
Date: November 1, 1997
Creator: Jones, L.E. & Patton, H.J.
Partner: UNT Libraries Government Documents Department

Calibration of the Sonseca array with large magnitude regional and teleseismic events

Description: In order to calibrate the Sonseca station, a 19-element short-period seismic array with a 9 km diameter circular aperture located in central Spain (39.68N, 3.96W), wavefield measurements made on observed seismic phases are compared with expected values. Thirty-five well-recorded regional and teleseismic events are used to study bearing and phase velocity estimation properties. Preliminary results indicate that in general the Sonseca array performs well for both regional and teleseismic events for frequencies less than 5 Hz using standard array signal processing techniques. Main findings of this study are: (1) A systematic bias is observed in bearing estimates; the bias is a function of the true bearing for events from the easterly directions of the array and can be mitigated with a simple bias correction. Using a least-squares quadratic polynomial fit, the bearing estimation error can be reduced to less than two or three degrees. (2) Measured signal and noise coherence functions and beamforming suggest that for regional events improved SNR is obtained by beamforming in the frequency band of 0.5 to 4 Hz with a resulting array gain as high as 10 dB. (3) Because the element spacing of Sonseca array corresponds to that of a sparse regional array, spatial aliasing can be observed in narrowband f-K analysis at the higher frequencies. We compare performance of narrowband and broadband frequency-wavenumber (f-k) analysis and suggest preliminary recipes for f-k and beamforming analysis.
Date: July 1, 1996
Creator: Dowla, F.U.
Partner: UNT Libraries Government Documents Department

Third Quarter Hanford Seismic Report for Fiscal Year 2000

Description: 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 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{degree}-47{degree}N latitude and 119{degree}-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.
Date: September 1, 2000
Creator: Hartshorn, Donald C; Reidel, Steve & Rohay, Alan C
Partner: UNT Libraries Government Documents Department

Quadratic negative evidence discrimination

Description: This paper develops regional discrimination methods which use information inherent in phase magnitudes that are unmeasurable due to small amplitudes and/or high noise levels. The methods are enhancements to teleseismic techniques proposed by, and are extended to regional discrimination. Events observed at teleseismic distances are effectively identified with the M{sub s} vs m{sub b} discriminant because relative to the pressure wave energy (m{sub b}) of an event, an earthquake generates more shear wave energy (M{sub s}) than does an explosion. For some teleseismic events, the M{sub s} magnitude is difficult to measure and is known only to be below a threshold . With M{sub s} unmeasurable, the M{sub s} vs m{sub b} discriminant cannot be formed. However, if the M{sub s} is sufficiently small relative to a measured m{sub b}, then the event is still likely to be an explosion. The methods presented in this report are developed for a single seismic station, and make use of empirical evidence in the regional L{sub g} vs p{sub g} discriminant. The L{sub g} vs p{sub g} discriminant is analogous to the teleseismic M{sub s} vs m{sub b} discriminant.
Date: May 1, 1997
Creator: Anderson, D.N.; Redgate, T.; Anderson, K.K.; Rohay, A.C. & Ryan, F.M.
Partner: UNT Libraries Government Documents Department


Description: In areas composed of coastal plain sediments, soft zones subjected to partial overburden may be present in the subsurface. During or after a seismic event, these soft zones may be compressed. The resulting displacement due to the deformation of the soft zones will propagate to the ground surface and cause the surface to settle. This paper presents a method to predict the settlement at the surface due to the propagation of the displacement from the soft zones. This method is performed by discretizing the soft zones into multiple clusters of finite sub-areas or subspaces. Settlement profile at the ground surface due to the displacement of each sub-area or subspace is computed assuming the shape is a normal distribution function. Settlement due to the displacement of the soft zones can then be approximated by adding the settlements computed for all the sub-areas or subspaces. This method provides a simple and useful tool for the prediction of the settlement profile and the results are consistent with those obtained from the finite difference analysis.
Date: March 3, 2008
Creator: Li, W
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

Probabilistic Assessment of Weld Quality in Steel Piping Under Seismic Conditions

Description: Seismic stress analyses of plant piping systems usually ignore the possibility of reduced joint strength due to weld imperfections. This paper presents a method that might be used to assess the impact of weld imperfections in a piping system, provided that limited destructive examination of welded joints is possible. A probability distribution function of weld quality is developed from the destructive examination, and this is combined with an experimentally determined relationship between weld quality and reduced strength. This latter is the result of uniaxial tensile testing of specimens with controlled imperfections. A seismic stress probability distribution function is determined by conventional seismic analysis. The above quantities are used to quantify the conditional failure probability of the imperfect weld. Effect of imperfection distribution within a given weld on the probability of failure is discussed.
Date: May 29, 2001
Creator: Awadalla, N.G.
Partner: UNT Libraries Government Documents Department

Calibration of seismic wave propagation in Kuwait

Description: The Kuwait Institute of Scientific Research (KISR), the USGS and LLNL are collaborating to calibrate seismic wave propagation in Kuwait and surrounding regions of the northwest Arabian Gulf using data from the Kuwait National Seismic Network (KNSN). Our goals are to develop local and regional propagation models for locating and characterizing seismic events in Kuwait and portions of the Zagros mountains close to Kuwait. The KNSN consists of 7 short-period stations and one broadband (STS-2) station. Constraints on the local velocity structure may be derived from joint inversions for hypocenters of local events and the local velocity model, receiver functions from three-component observations of teleseisms, and surface wave phase velocity estimated from differential dispersion measurements made across the network aperture. Data are being collected to calibrate travel-time curves for the principal regional phases for events in the Zagros mountains. The available event observations span the distance range from approximately 2.5 degrees to almost 9 degrees. Additional constraints on structure across the deep sediments of the Arabian Gulf will be obtained from long-period waveform modeling.
Date: July 23, 1999
Creator: Al-Awadhi, J; Endo, E; Fryall, F; Harris, D; Mayeda, K; Rodgers, A et al.
Partner: UNT Libraries Government Documents Department

Background noise spectra of global seismic stations

Description: Over an extended period of time station noise spectra were collected from various sources for use in estimating the detection and location performance of global networks of seismic stations. As the database of noise spectra enlarged and duplicate entries became available, an effort was mounted to more carefully select station noise spectra while discarding others. This report discusses the methodology and criteria by which the noise spectra were selected. It also identifies and illustrates the station noise spectra which survived the selection process and which currently contribute to the modeling efforts. The resulting catalog of noise statistics not only benefits those who model network performance but also those who wish to select stations on the basis of their noise level as may occur in designing networks or in selecting seismological data for analysis on the basis of station noise level. In view of the various ways by which station noise were estimated by the different contributors, it is advisable that future efforts which predict network performance have available station noise data and spectral estimation methods which are compatible with the statistics underlying seismic noise. This appropriately requires (1) averaging noise over seasonal and/or diurnal cycles, (2) averaging noise over time intervals comparable to those employed by actual detectors, and (3) using logarithmic measures of the noise.
Date: August 1, 1996
Creator: Wada, M.M. & Claassen, J.P.
Partner: UNT Libraries Government Documents Department

MENA 1.1 - An Updated Geophysical Regionalization of the Middle East and North Africa

Description: This short report provides an update to the earlier LLNL paper entitled ''Preliminary Definition of Geophysical Regions for the Middle East and North Africa'' (Sweeney and Walter, 1998). This report is designed to be used in combination with that earlier paper. The reader is referred to Sweeney and Walter (1998) for all details, including definitions, references, uses, shortcomings, etc., of the regionalization process. In this report we will discuss only those regions in which we have changed the boundaries or velocity structure from that given by the original paper. The paper by Sweeney and Walter (1998) drew on a variety of sources to estimate a preliminary, first-order regionalization of the Middle East and North Africa (MENA), providing regional boundaries and velocity models within each region. The model attempts to properly account for major structural discontinuities and significant crustal thickness and velocity variations on a gross scale. The model can be used to extrapolate sparse calibration data within a distinct geophysical region. This model can also serve as a background model in the process of forming station calibration maps using intelligent interpolation techniques such as kriging, extending the calibration into aseismic areas. Such station maps can greatly improve the ability to locate and identify seismic events, which in turn improves the ability to seismically monitor for underground nuclear testing. The original model from Sweeney and Walter (1998) was digitized to a 1{sup o} resolution, for simplicity we will hereafter refer to this model as MENA 1.0. The new model described here has also been digitized to a 1{sup o} resolution and will be referred to as MENA1.1 throughout this report.
Date: March 1, 2000
Creator: Walters, B.; Pasyanos, M.E.; Bhattacharyya, J. & O'Boyle, J.
Partner: UNT Libraries Government Documents Department

Hanford site post NPH building inspection plan

Description: This plan establishes consistent post-NPH building inspection procedures and defines a procedure for prioritization of buildings for inspection to ensure the safety of facilities prior to reentry. Qualification of systems for restart of operation is not included. This plan takes advantage, where possible, of existing national procedures for post-NPH inspection of buildings, of existing structural design and evaluation documentation of Hanford facilities, and current and proposed seismic instrumentation located throughout the Hanford site. A list of buildings, prioritized according to current building safety function and building vulnerability (without regard for or information about a damaging natural forces event) is provided.
Date: September 12, 1996
Creator: Wagenblast, G. R.
Partner: UNT Libraries Government Documents Department