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On reducing the amplitude of surface waves by source arrays

Description: The Geneva conference of experts stated that surface waves help define the nature of a seismic perturbation. A `phase equalization` method has been proposed by several seismologists to determine the polarity of the source using crustal surface waves. In this report a horizontal source array is designed which will reduce the amplitude of the crustal surface waves by a factor of five. Experimental data from Geophysical Prospecting is cited to support the effectiveness of such arrays. It is thought that phase shifts will accompany this amplitude reduction. It is concluded that these amplitude and phase changes will make the phase equalization method unreliable. The significance of the report is that the Geneva negotiations must take into account the possibility of horizontal as well as vertical arrays.
Date: November 23, 1959
Creator: Werth, G. C.
Partner: UNT Libraries Government Documents Department

Building on and spinning off: Sandia National Labs` creation of sensors for Vietnam

Description: This paper discusses Sandia National Laboratories` development of new technologies for use in the Vietnam War - specifically the seismic sensors deployed to detect troop and vehicle movement - first along the Ho Chi Minh Trail and later in perimeter defense for American military encampments in South Vietnam. Although the sensor story is a small one, it is interesting because it dovetails nicely with our understanding of the war in Vietnam and its frustrations; of the creation of new technologies for war and American enthusiasm for that technology; and of a technological military and the organizational research and a m am development structure created to support it. Within the defense establishment, the sensors were proposed within the context of a larger concept - that of a barrier to prevent the infiltration of troops and supplies from North Vietnam to the South. All of the discussion of the best way to fight in Vietnam is couched in the perception that this was a different kind of war than America was used to fighting. The emphasis was on countering the problems posed by guerrilla/revolutionary warfare and eventually by the apparent constraints of being involved in a military action, not an outright war. The American response was to find the right technology to do the job - to control the war by applying a technological tincture to its wounds and to make the war familiar and fightable on American terms. And, when doubts were raised about the effectiveness of applying existing technologies (namely, the bombing of North Vietnam and Laos), the doubters turned to new technologies. The sensors that were developed for use in Vietnam were a direct product of this sort of thinking - on the part of the engineers at Sandia who created the sensors, the civilian scientific advisors who recommended ...
Date: December 31, 1996
Creator: Ullrich, R.
Partner: UNT Libraries Government Documents Department

Regional observations of mining blasts by the GSETT-3 seismic monitoring system

Description: The cessation of testing of any nuclear explosive devices in all environments is the goal of the Comprehensive Test Ban Treaty. In order to assure compliance with such a treaty, an international monitoring system has been proposed. This system will include seismic, infrasound, hydroacoustic and radionuclide monitors located throughout the world. The goal of this system is the detection of any nuclear test. In preparation for this treaty, a series of monitoring system tests, focusing primarily on seismic observations, have been undertaken. The most recent of these tests, Group of Scientific Experts Technical Test Three (GSETT-3), provides valuable data for assessing future monitoring systems. During the course of this experiment, seismic events associated with earthquakes, nuclear explosions and mining explosions have been recorded. This presentation will discuss the numbers and types of mining explosions triggering the system, in a particular area. Possible implications for the mining industry will be explored.
Date: December 31, 1996
Creator: Stump, B.W. & Pearson, D.C.
Partner: UNT Libraries Government Documents Department

Infrasound workshop for CTBT monitoring: Proceedings

Description: It is expected that the establishment of new infrasound stations in the global IMS network by the Provisional Technical Secretariat of the CTBTO in Vienna will commence in the middle of 1998. Thus, decisions on the final operational design for IMS infrasound stations will have to be made within the next 12 months. Though many of the basic design problems have been resolved, it is clear that further work needs to be carried out during the coming year to ensure that IMS infrasound stations will operate with maximum capability in accord with the specifications determined during the May 1997 PrepCom Meeting. Some of the papers presented at the Workshop suggest that it may be difficult to design a four-element infrasound array station that will reliably detect and locate infrasound signals at all frequencies in the specified range from 0.02 to 4.0 Hz in all noise environments. Hence, if the basic design of an infrasound array is restricted to four array elements, the final optimized design may be suited only to the detection and location of signals in a more limited pass-band. Several participants have also noted that the reliable discrimination of infrasound signals could be quite difficult if the detection system leads to signal distortion. Thus, it has been emphasized that the detection system should not, if possible, compromise signal fidelity. This report contains the workshop agenda, a list of participants, and abstracts and viewgraphs from each presentation.
Date: November 1, 1998
Creator: Christie, D. & Whitaker, R.
Partner: UNT Libraries Government Documents Department

Regional seismic discrimination in central Asia with emphasis on western China

Description: In support of an anticipated Comprehensive Test Ban Treaty, the authors have started to evaluate regional seismic event discrimination capabilities for central Asia, emphasizing western China. The authors have measured noise and seismic phase amplitudes of over 250 earthquakes and 18 underground nuclear explosions recorded at the broadband, digital station WMQ in western China and over 100 earthquakes and 5 nuclear explosions at station AAK in Kyrgyzstan. The explosions are from the Kazakh Test Site (KTS) and Lop Nor, China. The earthquakes are mostly from northwest China. They have also evaluated a single suspected chemical explosion. Event magnitudes (m{sub b}) range between 2.5 and 6.5 and maximum event-station distance is about 1,700 km. Using these measurements the authors formed phase, spectral, cross-spectral, short-period/long-period, and long-period ratios to test many possible event discriminants. All ratios were corrected for distance effects before forming ratio-versus-magnitude discrimination plots. The authors found that all five classes of these discriminants are useful for separating earthquakes from explosions in central Asia, provided the right combinations of frequency bands and phases are selected. Results are described.
Date: September 1, 1996
Creator: Hartse, H.E.; Taylor, S.R.; Phillips, W.S. & Randall, G.E.
Partner: UNT Libraries Government Documents Department

Statistical classification methods applied to seismic discrimination

Description: To verify compliance with a Comprehensive Test Ban Treaty (CTBT), low energy seismic activity must be detected and discriminated. Monitoring small-scale activity will require regional (within {approx}2000 km) monitoring capabilities. This report provides background information on various statistical classification methods and discusses the relevance of each method in the CTBT seismic discrimination setting. Criteria for classification method selection are explained and examples are given to illustrate several key issues. This report describes in more detail the issues and analyses that were initially outlined in a poster presentation at a recent American Geophysical Union (AGU) meeting. Section 2 of this report describes both the CTBT seismic discrimination setting and the general statistical classification approach to this setting. Seismic data examples illustrate the importance of synergistically using multivariate data as well as the difficulties due to missing observations. Classification method selection criteria are presented and discussed in Section 3. These criteria are grouped into the broad classes of simplicity, robustness, applicability, and performance. Section 4 follows with a description of several statistical classification methods: linear discriminant analysis, quadratic discriminant analysis, variably regularized discriminant analysis, flexible discriminant analysis, logistic discriminant analysis, K-th Nearest Neighbor discrimination, kernel discrimination, and classification and regression tree discrimination. The advantages and disadvantages of these methods are summarized in Section 5.
Date: June 11, 1996
Creator: Ryan, F.M.; Anderson, D.N.; Anderson, K.K.; Hagedorn, D.N.; Higbee, K.T.; Miller, N.E. et al.
Partner: UNT Libraries Government Documents Department

Regional location in western China

Description: Accurately locating seismic events in western China using only regional seismic stations is a challenge. Not only is the number of seismic stations available for locating events small, but most stations available to researchers are often over 10{degree} distant. Here the authors describe the relocation, using regional stations, of both nuclear and earthquake sources near the Lop Nor test site in western China. For such relocations, they used the Earthquake Data Reports provided by the US Geological Survey (USGS) for the reported travel times. Such reports provide a listing of all phases reported to the USGS from stations throughout the world, including many stations in the People`s Republic of China. LocSAT was used as the location code. The authors systematically relocated each event int his study several times, using fewer and fewer stations at reach relocation, with the farther stations being eliminated at each step. They found that location accuracy, judged by comparing solutions from few stations to the solution provided using all available stations, remained good typically until fewer than seven stations remained.With a good station distribution, location accuracy remained surprisingly good (within 7 km) using as few as 3 stations. Because these relocations were computed without good station corrections and without source-specific station corrections (that is, path corrections), they believe that such regional locations can be substantially improved, largely using static station corrections and source-specific station corrections, at least in the Lop nor area, where sources have known locations. Elsewhere in China, one must rely upon known locations of regionally-recorded explosions. Locating such sources is clearly one of the major problems to be overcome before one can provide event locations with any assurance from regional stations.
Date: October 1, 1996
Creator: Cogbill, A.H. & Steck, L.K.
Partner: UNT Libraries Government Documents Department

Regional characterization of Western China-II

Description: As part of the CTBT Research and Development regional characterization effort, geological, geophysical, and seismic data are being assembled and organized for inclusion in a knowledge base for China. The authors have continued their analysis using data form the station WMQ of the Chinese Digital Seismic Network (CDSN) and the IRIS station AAK. They are also acquiring and analyzing data from stations that are designated as (or near a designated) primary or secondary CTBT monitoring station. Regional seismograms are being analyzed to construct travel time curves, velocity models, attenuation characteristics, and to quantify regional propagation effects such as phase blockages. Using locations from the USGS Preliminary Determination of Epicenters (PDE) they have identified Pn, Pg, Sn, and Lg phases, constructed travel time curves, and estimated apparent velocities using linear regression. Amplitudes for the seismic phases have been measured using bandpassed waveforms and a series of magnitude relations have been determined for Western China. Studies of path specific propagation efficiency of the seismic phases have mapped blockages and also identified a possible set of observations that can be used to identify intermediate depth (> 100 im) seismic events in the Pamir-Hindu Kush seismic zone. Chinese seismicity catalogs from the USGS and Chinese State Seismological Bureau (SSB) are being used to identify and obtain seismic data (including mine seismicity) and information for lower magnitude events. Clustering analysis has been used to identify seismicity clusters in space with origin times that are distributed during daylight hours which suggest mining operations. These clusters are being investigated with imagery to attempt to identify precise mine locations.
Date: October 1, 1996
Creator: Randall, G.E.; Hartse, H.E.; Phillips, W.S. & Taylor, S.R.
Partner: UNT Libraries Government Documents Department

Mining industry and US government cooperative research: Lessons learned and benefits to mining industry

Description: Since 1994, various mines in the US have cooperated with research scientists at the Los Alamos and Lawrence Livermore National Laboratories to address issues related to verification of the Comprehensive Test Ban Treaty (CTBT). The CTBT requires that no country may conduct any nuclear explosion in the future. While the CTBT is a significant step toward reducing the global nuclear danger, verifying compliance with the treat requires that the monitoring system be able to detect, locate and identify much larger numbers of smaller amplitude seismic events than had been required previously. Large mining blasts conducted world-wide will be of sufficient amplitude to trigger the monitoring system at the lower threshold. It is therefore imperative that research into the range various blasting practices employed, the relationship of yield to seismic magnitude, and identification of anomalous blasting results be performed. This paper will describe a suite of experiments funded by the Department of Energy and conducted by the Los Alamos and Lawrence Livermore National Laboratories in cooperation with the US mining industry. Observations of cast blasting, underground long wall generated coal bumps, stoping, and explosively induced collapse of room and pillar panels will be presented. Results of these dual use experiments which are of interest to the mining community will be discussed. These include (1) variation of amplitude of seismic energy at various azimuths from cast blasts, (2) identification of the extent of back failure following explosive removal of pillars, and (3) the use of single fired shots for calibration of the monitoring system. The wealth of information and discovery described in this paper is a direct result of mutual cooperation between the US Government and the US Mining Industry.
Date: September 1, 1997
Creator: Pearson, D.C.; Stump, B.W.; Phillips, W.S.; Martin, R. & Anderson, D.P.
Partner: UNT Libraries Government Documents Department

Robust bearing estimation for 3-component stations

Description: A robust bearing estimation process for 3-component stations has been developed and explored. The method, called SEEC for Search, Estimate, Evaluate and Correct, intelligently exploits the inherent information in the arrival at every step of the process to achieve near-optimal results. In particular the approach uses a consistent framework to define the optimal time-frequency windows on which to make estimates, to make the bearing estimates themselves, to construct metrics helpful in choosing the better estimates or admitting that the bearing is immeasurable, and finally to apply bias corrections when calibration information is available to yield a single final estimate. The algorithm was applied to a small but challenging set of events in a seismically active region. It demonstrated remarkable utility by providing better estimates and insights than previously available. Various monitoring implications are noted from these findings.
Date: February 1, 2000
Partner: UNT Libraries Government Documents Department

Savannah River Plant seismograph network

Description: The network consists of three field seismometer sites (SRPN, SRPW, SRPD) and one central recording station. The seismic activity at each field site is detected by a seismometer, which is a movable coil that induces a series of electric impulses when vibrated. These electrical impulses are amplified and sent over telephone lines to a central recording site, where the signals are again amplified and then recorded by a heated stylus on heat-sensitive paper. The signals from sites SRPN and SRPW are fed directly to telephone lines, but the signal for SRPD is first transmitted by radio to the D-area powerhouse and then fed into a telephone line for transmission to the recording station. The signals from seismometer site SRPN are recorded at two different gains (high and medium) to permit different resolutions for earthquakes of different magnitudes. Performance of the system is described.
Date: January 1, 1980
Creator: Krapp, C W
Partner: UNT Libraries Government Documents Department

Los Alamos National Laboratory Northern New Mexico Seismic Network and seismicity

Description: The Northern New Mexico Seismic Network (NNMSN) is described and the research conducted there briefly discussed. Its purpose is to: (1) monitor seismic activity that can pose a risk to the Los Alamos National Laboratory; (2) monitor induced seismicity that might result from the Laboratory's experimental activities, such as the Hot Dry Rock project; (3) provide data for research in test ban verification; and (4) provide data for fundamental research in seismology, tectonics, and geologic structure of the Rio Grande Rift and the Jemez Mountains. (ACR)
Date: January 1, 1981
Creator: Cash, D.J.
Partner: UNT Libraries Government Documents Department

Operation of a telemetered seismic network on the Alaska Peninsula. Annual report

Description: A large aperture network of eleven short period seismic stations is being operated on the Alaska Peninsula and several offshore islands to acquire data for the study of the seismotectonics of a part of the Alaska-Aleutian arc-trench structure. The system operated satisfactorily during the past year and continued to provide seismic coverage at a low magnitude threshold level (M/sub L/ = 2.0). An event detection system, developed under this contract over the past years, has been field installed and is undergoing fine tuning. Focal mechanism studies of intermediate depths Benioff zone earthquakes were continued. Like a previous, smaller set, these mechanisms show predominantly down-dip extension, indicating gravitational sinking of the subducting lithosphere. Analysis of the combined data from our network and a temporary array of Ocean Bottom Seismometers, deployed under a related study, indicate that epicenters of earthquakes in the continental shelf area off Kodiak Island are shifted landward by about 15 km with respect to the epicenters determined from the combined data set. Clusters of shallow seismic activity associated with certain Alaska Peninsula volcanoes, observed over the past years, had previously been interpreted as related to shallow magmatic-geothermal reservoirs. Volcanologic-petrologic field studies conducted last year show that volcanic centers associated with such swarms do indeed have surface manifestations of hydrothermal activity.
Date: February 1, 1981
Partner: UNT Libraries Government Documents Department

National Seismic Stations transducers and filters

Description: The National Seismic Stations (NSS) instruments are being developed for seismic monitoring of regional and teleseismic events. They consist of two 3-component, broadband, borehole seismometers: the KS-36000 and the S-700, which is the backup for the KS-36000. Output is divided into frequency bands to reduce data loss due to saturation. Complete block diagrams of the KS-36000 and S-700 NSS seismometers and filters are presented. Both open-loop and closed-loop steady-state amplitude and phase curves are given. Without band-pass filters (but with shaping filters) the KS-36000 has a flat (i.e., between the -3dB points) velocity sensitivity from 0.03 to 23 Hz. With its shaping filters, the S-700 is flat from 0.2 to 40 Hz. The structure of the three band-pass filters (LP, MP, and SP) is superimposed on these velocity sensitivities. Passbands of the resulting overall velocity sensitivity for the KS-36000 are as follows: LP band = 0.01-0.05 Hz, MP band = 0.02-1.3 Hz, and SP band = 1-10 Hz. Step-function responses and phase and group delays are given for each of the bands. The MP-band step response is oscillatory due to its sharp, high-frequency cutoff, but an MP-band filter with a less abrupt cutoff eliminates the oscillation. To generate typical NSS output seismograms, velocity inputs from four representative seismic events were used: an underground nuclear test (..delta.. approx. = 3.6/sup 0/), a regional earthquake (..delta.. approx. = 20/sup 0/), a local earthquake (..delta.. approx. = 1.5/sup 0/), and a teleseismic earthquake (..delta.. approx. = 123/sup 0/). The velocity inputs for these events were obtained from the LLNL digital seismic network (DSS) around the Nevada Test Site (NTS). The seismograms resulting from each of the bands were satisfactory, although the low-frequency corner of the MP band should be increased in frequency to 0.08 Hz.
Date: January 13, 1981
Creator: Rodgers, P.W. & Hummell, M.
Partner: UNT Libraries Government Documents Department

Microseismic monitoring of Chocolate Bayou, Texas: the Pleasant Bayou No. 2 geopressured/geothermal energy test well program

Description: The Brazoria seismic network, instrumentation, design, and specifications are described. The data analysis procedures are presented. Seismicity is described in relation to the Pleasant Bayou production history. Seismicity originating near the chemical plant east of the geopressured/geothermal well is discussed. (MHR)
Date: January 1, 1984
Creator: Mauk, F.J.; Kimball, B. & Davis, R.A.
Partner: UNT Libraries Government Documents Department

Compensated intruder-detection systems

Description: The invention is an improvement to an intruder-detection system of the kind where intruder-induced signals are transmitted through a medium whose conductance varies with certain climatic conditions. The improved system includes means coupled to the medium for converting the intruder-induced signals received therefrom to a first electrical signal. Means also are provided for generating a reference signal proportional to the climate-induced changes in the signal-conductance of the medium. Means are provided for generating, from the first electrical signal and the reference signal, an electrical output signal which is unaffected by the changes in signal-conductance. Means are provided to give warning when the output signal exceeds a selected value. In another aspect, the invention is a method for operating an intruder-detection system of the kind wherein an intrusion-generated signal transmitted through a detection medium is converted to a first electrical signal. The first electrical signal contains variations resulting from climate-induced changes in the medium. The method of the invention comprises generating an electrical reference signal proportional to the climate-induced changes in the medium; conditioning the first signal with the reference signal to produce an electrical output signal which is unaffected by the climate-induced changes in the medium; and impressing the resulting output signal across an alarm circuit to actuate the same when the output signal exceeds a selected value.
Date: January 20, 1982
Creator: McNeilly, D.R. & Miller, W.R.
Partner: UNT Libraries Government Documents Department

Three-dimensional inversion of travel time data for structurally complex geology

Description: Modeling and inversion techniques for the seismic prospecting problem are described. A concisely-parametrized geological model of the site under study is constructed, and the forward problem'' of simulating the effects of shots on this model is solved by ray-tracing. We then use constrained optimization techniques to choose values for the model parameters so that the predicted response to the shots matches the observed response in either the least-squares or least {ell}{sub 1} sense. Numerical experience is reported. 14 refs., 2 figs., 8 tabs.
Date: August 1, 1990
Creator: Pereyra, V. (Weidlinger Associates, Los Altos, CA (USA)) & Wright, S.J. (Argonne National Lab., IL (USA))
Partner: UNT Libraries Government Documents Department

High resolution seismic survey, Pen Branch Fault, Savannah River Site, South Carolina

Description: An investigation of the Pen Branch Fault at the Savannah River Site by a series of short, high resolution seismic reflection lines was conducted. The purpose was to acquire, process, and interpret 19.9 miles of data, optimized for the upper 300 ft of geologic strata, in sufficient density such that processing performed in the conventional stepwise approach, followed by detailed interpretation, would define small scale spatial variability and structural features in the vicinity of the fault leading to definition of the location of the fault, the shallowest extent of the fault, and the quantification of the sense and magnitude of motion. The depth of optimization for the last two lines was modified to the 300 ft of geologic strata immediately above basement. Three older seismic surveys, other geophysical data, and associated borehole and geologic data were reviewed. The equipment and the acquisition, processing, and interpretation procedures are discussed in the report. The report includes a detailed line by line description and discussion of the interpretation. Figures include reference maps, contour displays of the stacking and interval velocities, diagrammatic references sketches of the interpreted layering and sedimentary features, index sketches, and specific color prints made on the workstation during the course of the interpretation. A volume of manuals on seismic devices and related equipment is included.
Date: April 1, 1991
Creator: Berkman, E. (Emerald Exploration Consultants, Inc., Austin, TX (United States))
Partner: UNT Libraries Government Documents Department

Technical manual: operation and equipment instructions for in situ impulse test

Description: This manual describes the test equipment and procedures for a new field test which determines the shear modulus of a soil deposit at strain levels equivalent to those experienced during actual earthquakes. Results from this test are typically used as input parameters to response analyses for evaluating local soil effects during earthquake shaking. The test employs a cross-hole wave propagation procedure with velocity transducers located in closely spaced adjacent borings. Clear, consistent, and repeatable data in all types of soil and a method of data reduction different from conventional geophysical first arrival techniques are unique aspects of this new test. In addition to describing the principles of the test and data reduction procedures, major discussions of the field procedures are also included. Detailed drilling and testing information is provided both for planning and executing a test program.
Date: November 1, 1979
Partner: UNT Libraries Government Documents Department

CSDP: The seismology of continental thermal regimes

Description: This is a progress report for the past one year of research (year 3 of 5-year project) under the project titled CSDP: Seismology of Continental Thermal Regime'', in which we proposed to develop seismological interpretation theory and methods applicable to complex structures encountered in continental geothermal areas and apply them to several candidate sites for the Continental Scientific Drilling Project. The past year has been extremely productive especially in the area of interpretation theory, including the following two major break-throughs. One is the derivation of an integral equation for time-dependent power spectra, which unified all the existing theories on seismic scattering (including the radiative transfer theory for total energy and single and multiple scattering theories based on the ray approach) and offers more complete and economical solutions to the problems of seismic scattering and attenuation. The other is the new formula for synthetic seismograms for layered media with irregular interfaces, combining the T-matrix method for an arbitrary shaped inclusion and the method of global generalized reflection/transmission coefficients for layered media. Both breakthroughs will enable us to deal with seismic observations in complex earth structures more efficiently and accurately. In the area of experimental studies, we discovered seismic guided waves trapped in the San Andreas fault near Parkfield, California. 54 refs., 14 figs.
Date: May 1, 1990
Creator: Aki, K.
Partner: UNT Libraries Government Documents Department

CTBT integrated verification system evaluation model supplement

Description: Sandia National Laboratories has developed a computer based model called IVSEM (Integrated Verification System Evaluation Model) to estimate the performance of a nuclear detonation monitoring system. The IVSEM project was initiated in June 1994, by Sandia's Monitoring Systems and Technology Center and has been funded by the U.S. Department of Energy's Office of Nonproliferation and National Security (DOE/NN). IVSEM is a simple, ''top-level,'' modeling tool which estimates the performance of a Comprehensive Nuclear Test Ban Treaty (CTBT) monitoring system and can help explore the impact of various sensor system concepts and technology advancements on CTBT monitoring. One of IVSEM's unique features is that it integrates results from the various CTBT sensor technologies (seismic, in sound, radionuclide, and hydroacoustic) and allows the user to investigate synergy among the technologies. Specifically, IVSEM estimates the detection effectiveness (probability of detection), location accuracy, and identification capability of the integrated system and of each technology subsystem individually. The model attempts to accurately estimate the monitoring system's performance at medium interfaces (air-land, air-water) and for some evasive testing methods such as seismic decoupling. The original IVSEM report, CTBT Integrated Verification System Evaluation Model, SAND97-25 18, described version 1.2 of IVSEM. This report describes the changes made to IVSEM version 1.2 and the addition of identification capability estimates that have been incorporated into IVSEM version 2.0.
Date: March 2, 2000
Partner: UNT Libraries Government Documents Department

Seismic monitoring of a flow test in the Salton Sea Geothermal Field

Description: The purpose of this seismic monitoring project was to characterize in detail the micro-seismic activity related to the flow-injection test in the Salton Sea Geothermal Field. Our goal was to determine if any sources of seismic energy related to the test were observable at the surface, using both conventional seismic network techniques and relatively newer array techniques. These methods allowed us to detect and locate both impulsive microearthquakes and continuous sources of seismic energy. Our network, which was sensitive enough to be triggered by magnitude 0.0 or larger events, found no impulsive microearthquakes in the vicinity of the flow test in the 8 month period before the test and only one event during the flow test. We have observed some continuous seismic noise sources that may be attributed to the flow test. 4 refs., 4 figs.
Date: June 1, 1989
Creator: Jarpe, S.P.; Kasameyer, P.W. & Johnston, C.
Partner: UNT Libraries Government Documents Department

Variability of relative site response at Los Alamos, NM

Description: To estimate the range of seismic response at low strain of sites within Los Alamos National Laboratory, ground motion recordings were obtained at 13 sites from nuclear tests carried out in Nevada. The sites are distributed within a 10 X 10 km area. The ground motions recorded at each site were conceptually modelled as the result of source, path, and site contributions. Because almost all of the paths are in common, the variations seen for each source can be attributed to site response. The sites were monitored in various combinations with seven nuclear tests; each site recorded only a few of the tests. Because horizontal ground motion is more important for structural engineering and was larger than the vertical, we focused on horizontal site response. The range of relative site response seen is about a factor of 5 to 6 at 1.5 Hz. Topography has a strong effect on response, with sites in canyons being a factor of 3 to 4 lower than nearby sites on mesas. Increased depth to seismic basement beneath some stations also correlates with higher relative site response. Relative site response does not obviously correlate with variation of seismic velocities in the near surface (e.g. upper few meters). 5 refs., 4 figs.
Date: January 1, 1989
Creator: House, L. & Phillips, W.S. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Ground motion analyses: OSSY (a high explosive experiment) and MERLIN (a nuclear event)

Description: We have analyzed recorded data and conducted numerical simulations of the seismic-calibration high explosive experiment OSSY and of the underground nuclear event MERLIN to determine if there is any physical correlation in their ground motion response. Waveforms recorded on OSSY and MERLIN show a distinct similarity in the form of a dual-pulse structure, with the second pulse as large or larger than the first pulse. Results with 1D and 2D simulations show that there is no correlation. The dual-pulse structure for OSSY can best be accounted for by a dilatancy feature resulting from pore recovery during unloading. There is also a notable influence on the pulse shape caused by the large length-to-diameter ratio of the high explosive charge. The dual-pulse structure recorded in MERLIN is most likely due to refraction from a higher-impedance layer about 60 m below the workout. 15 refs., 26 figs.
Date: October 1, 1991
Creator: Swift, R.P.
Partner: UNT Libraries Government Documents Department