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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

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

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

UNCERTAINTY IN PHASE ARRIVAL TIME PICKS FOR REGIONAL SEISMIC EVENTS: AN EXPERIMENTAL DESIGN

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

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

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

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

PREDICTION OF SURFACE SETTLEMENT DUE TO THE DISPLACEMENT OF SOFT ZONES

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

Berkeley Seismological Laboratory Seismic Moment Tensor Report for the August 6, 2007 M3.9 Seismic event in central Utah

Description: We have performed a complete moment tensor analysis of the seismic event, which occurred on Monday August 6, 2007 at 08:48:40 UTC 21 km from Mt.Pleasant, Utah. In our analysis we utilized complete three-component seismic records recorded by the USArray, University of Utah, and EarthScope seismic arrays. The seismic waveform data was integrated to displacement and filtered between 0.02 to 0.10 Hz following instrument removal. We used the Song et al. (1996) velocity model to compute Green's functions used in the moment tensor inversion. A map of the stations we used and the location of the event is shown in Figure 1. In our moment tensor analysis we assumed a shallow source depth of 1 km consistent with the shallow depth reported for this event. As shown in Figure 2 the results point to a source mechanism with negligible double-couple radiation and is composed of dominant CLVD and implosive isotropic components. The total scalar seismic moment is 2.12e22 dyne cm corresponding to a moment magnitude (Mw) of 4.2. The long-period records are very well matched by the model (Figure 2) with a variance reduction of 73.4%. An all dilational (down) first motion radiation pattern is predicted by the moment tensor solution, and observations of first motions are in agreement.
Date: August 8, 2007
Creator: Ford, S.; Dreger, D. & Hellweg, P.
Partner: UNT Libraries Government Documents Department

An Analysis of the Mt. Meron Seismic Array

Description: We have performed a quick analysis of the Mt. Meron seismic array to monitor regional seismic events in the Middle East. The Meron array is the only current array in the Levant and Arabian Peninsula and, as such, might be useful in contributing to event location, identification, and other analysis. Here, we provide a brief description of the array and a review of the travel time and array analysis done to assess its performance.
Date: January 10, 2008
Creator: Pasyanos, M E & Ryall, F
Partner: UNT Libraries Government Documents Department

Subspace Detectors: Efficient Implementation

Description: The optimum detector for a known signal in white Gaussian background noise is the matched filter, also known as a correlation detector [Van Trees, 1968]. Correlation detectors offer exquisite sensitivity (high probability of detection at a fixed false alarm rate), but require perfect knowledge of the signal. The sensitivity of correlation detectors is increased by the availability of multichannel data, something common in seismic applications due to the prevalence of three-component stations and arrays. When the signal is imperfectly known, an extension of the correlation detector, the subspace detector, may be able to capture much of the performance of a matched filter [Harris, 2006]. In order to apply a subspace detector, the signal to be detected must be known to lie in a signal subspace of dimension d {ge} 1, which is defined by a set of d linearly-independent basis waveforms. The basis is constructed to span the range of signals anticipated to be emitted by a source of interest. Correlation detectors operate by computing a running correlation coefficient between a template waveform (the signal to be detected) and the data from a window sliding continuously along a data stream. The template waveform and the continuous data stream may be multichannel, as would be true for a three-component seismic station or an array. In such cases, the appropriate correlation operation computes the individual correlations channel-for-channel and sums the result (Figure 1). Both the waveform matching that occurs when a target signal is present and the cross-channel stacking provide processing gain. For a three-component station processing gain occurs from matching the time-history of the signals and their polarization structure. The projection operation that is at the heart of the subspace detector can be expensive to compute if implemented in a straightforward manner, i.e. with direct-form convolutions. The purpose of this report ...
Date: July 26, 2006
Creator: Harris, D B & Paik, T
Partner: UNT Libraries Government Documents Department

EVENT TREE ANALYSIS AT THE SAVANNAH RIVER SITE: A CASE HISTORY

Description: At the Savannah River Site (SRS), a Department of Energy (DOE) installation in west-central South Carolina there is a unique geologic stratum that exists at depth that has the potential to cause surface settlement resulting from a seismic event. In the past the particular stratum in question has been remediated via pressure grouting, however the benefits of remediation have always been debatable. Recently the SRS has attempted to frame the issue in terms of risk via an event tree or logic tree analysis. This paper describes that analysis, including the input data required.
Date: May 25, 2009
Creator: Williams, R
Partner: UNT Libraries Government Documents Department

REVIEW OF THE STABILITY ANALYSIS FOR THE LANL BSL-3 BUILDING FOUNDATION

Description: This work was performed upon request from Dr. Richard Thorpe from NNSA after his review of the LANL report on BSL-3 seismic stability [1]. The authors also reviewed report [1] and concluded, as did Dr. Thorpe, that the stability analysis was inappropriate. There are several reasons for that conclusion: (1) the assumption of a circular failure surface through the combined fill-and-rock foundation does not recognize the geologic structure involved. (2) the assumption of an equivalent static force to an earthquake loading does not represent the multiple cycles of shear loads created by a seismic event that can engender a substantial degradation of shear modulus and shear strength of the soil under the building [2]. (3) there was no credible in-situ strength of the foundation materials (fill and rock mass) available for input into the stability analysis. Following that review, on September 26 the authors made a site visit and held discussions with LANL personnel connected to the BSL-3 building project. No information or evidence was presented to the authors indicating that the static stability of BSL-3 could be an issue. Accordingly, this report focuses on the topic of the BSL-3 site stability under seismic loading.
Date: November 30, 2006
Creator: Heuze, F E & Wagoner, J L
Partner: UNT Libraries Government Documents Department

Third Quater Seismic Report for Fiscal Year 2007

Description: 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 ...
Date: September 19, 2007
Creator: Rohay, Alan C.; Sweeney, Mark D.; Hartshorn, Donald C.; Clayton, Ray E. & Devary, Joseph L.
Partner: UNT Libraries Government Documents Department

SRS BEDROCK PROBABILISTIC SEISMIC HAZARD ANALYSIS (PSHA) DESIGN BASIS JUSTIFICATION (U)

Description: This represents an assessment of the available Savannah River Site (SRS) hard-rock probabilistic seismic hazard assessments (PSHAs), including PSHAs recently completed, for incorporation in the SRS seismic hazard update. The prior assessment of the SRS seismic design basis (WSRC, 1997) incorporated the results from two PSHAs that were published in 1988 and 1993. Because of the vintage of these studies, an assessment is necessary to establish the value of these PSHAs considering more recently collected data affecting seismic hazards and the availability of more recent PSHAs. This task is consistent with the Department of Energy (DOE) order, DOE O 420.1B and DOE guidance document DOE G 420.1-2. Following DOE guidance, the National Map Hazard was reviewed and incorporated in this assessment. In addition to the National Map hazard, alternative ground motion attenuation models (GMAMs) are used with the National Map source model to produce alternate hazard assessments for the SRS. These hazard assessments are the basis for the updated hard-rock hazard recommendation made in this report. The development and comparison of hazard based on the National Map models and PSHAs completed using alternate GMAMs provides increased confidence in this hazard recommendation. The alternate GMAMs are the EPRI (2004), USGS (2002) and a regional specific model (Silva et al., 2004). Weights of 0.6, 0.3 and 0.1 are recommended for EPRI (2004), USGS (2002) and Silva et al. (2004) respectively. This weighting gives cluster weights of .39, .29, .15, .17 for the 1-corner, 2-corner, hybrid, and Greens-function models, respectively. This assessment is judged to be conservative as compared to WSRC (1997) and incorporates the range of prevailing expert opinion pertinent to the development of seismic hazard at the SRS. The corresponding SRS hard-rock uniform hazard spectra are greater than the design spectra developed in WSRC (1997) that were based on the LLNL ...
Date: December 14, 2005
Creator: Lee, R. C. & McHood, M. D.
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

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

LANL seismic screening method for existing buildings

Description: The purpose of the Los Alamos National Laboratory (LANL) Seismic Screening Method is to provide a comprehensive, rational, and inexpensive method for evaluating the relative seismic integrity of a large building inventory using substantial life-safety as the minimum goal. The substantial life-safety goal is deemed to be satisfied if the extent of structural damage or nonstructural component damage does not pose a significant risk to human life. The screening is limited to Performance Category (PC) -0, -1, and -2 buildings and structures. Because of their higher performance objectives, PC-3 and PC-4 buildings automatically fail the LANL Seismic Screening Method and will be subject to a more detailed seismic analysis. The Laboratory has also designated that PC-0, PC-1, and PC-2 unreinforced masonry bearing wall and masonry infill shear wall buildings fail the LANL Seismic Screening Method because of their historically poor seismic performance or complex behavior. These building types are also recommended for a more detailed seismic analysis. The results of the LANL Seismic Screening Method are expressed in terms of separate scores for potential configuration or physical hazards (Phase One) and calculated capacity/demand ratios (Phase Two). This two-phase method allows the user to quickly identify buildings that have adequate seismic characteristics and structural capacity and screen them out from further evaluation. The resulting scores also provide a ranking of those buildings found to be inadequate. Thus, buildings not passing the screening can be rationally prioritized for further evaluation. For the purpose of complying with Executive Order 12941, the buildings failing the LANL Seismic Screening Method are deemed to have seismic deficiencies, and cost estimates for mitigation must be prepared. Mitigation techniques and cost-estimate guidelines are not included in the LANL Seismic Screening Method.
Date: January 1, 1997
Creator: Dickson, S.L.; Feller, K.C. & Fritz de la Orta, G.O.
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

Masonry infill performance during the Northridge earthquake

Description: The response of masonry infills during the 1994 Northridge, California earthquake is described in terms of three categories: (1) lowrise and midrise structures experiencing large near field seismic excitations, (2) lowrise and midrise structures experiencing moderate far field excitation, and (3) highrise structures experiencing moderate far field excitation. In general, the infills provided a positive beneficial effect on the performance of the buildings, even those experiencing large peak accelerations near the epicenter. Varying types of masonry infills, structural frames, design conditions, and construction deficiencies were observed and their performance during the earthquake indicated. A summary of observations of the performance of infills in other recent earthquakes is given. Comparison with the Northridge earthquake is made and expected response of infill structures in lower seismic regions of the central and eastern United States is discussed.
Date: March 8, 1996
Creator: Flanagan, R.D.; Bennett, R.M.; Fischer, W.L. & Adham, S.A.
Partner: UNT Libraries Government Documents Department