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Investigating the point seismic array concept with seismic rotation measurements.

Description: Spatially-distributed arrays of seismometers are often utilized to infer the speed and direction of incident seismic waves. Conventionally, individual seismometers of the array measure one or more orthogonal components of rectilinear particle motion (displacement, velocity, or acceleration). The present work demonstrates that measure of both the particle velocity vector and the particle rotation vector at a single point receiver yields sufficient information to discern the type (compressional or shear), speed, and direction of an incident plane seismic wave. Hence, the approach offers the intriguing possibility of dispensing with spatially-extended received arrays, with their many problematic deployment, maintenance, relocation, and post-acquisition data processing issues. This study outlines straightforward mathematical theory underlying the point seismic array concept, and implements a simple cross-correlation scanning algorithm for determining the azimuth of incident seismic waves from measured acceleration and rotation rate data. The algorithm is successfully applied to synthetic seismic data generated by an advanced finite-difference seismic wave propagation modeling algorithm. Application of the same azimuth scanning approach to data acquired at a site near Yucca Mountain, Nevada yields ambiguous, albeit encouraging, results. Practical issues associated with rotational seismometry are recognized as important, but are not addressed in this investigation.
Date: February 1, 2009
Creator: Abbott, Robert E. & Aldridge, David Franklin
Partner: UNT Libraries Government Documents Department

Integrated Reflection Seismic Monitoring and Reservoir Modeling for Geologic CO2 Sequestration

Description: The US DOE/NETL CCS MVA program funded a project with Fusion Petroleum Technologies Inc. (now SIGMA) to model the proof of concept of using sparse seismic data in the monitoring of CO{sub 2} injected into saline aquifers. The goal of the project was to develop and demonstrate an active source reflection seismic imaging strategy based on deployment of spatially sparse surface seismic arrays. The primary objective was to test the feasibility of sparse seismic array systems to monitor the CO{sub 2} plume migration injected into deep saline aquifers. The USDOE/RMOTC Teapot Dome (Wyoming) 3D seismic and reservoir data targeting the Crow Mountain formation was used as a realistic proxy to evaluate the feasibility of the proposed methodology. Though the RMOTC field has been well studied, the Crow Mountain as a saline aquifer has not been studied previously as a CO{sub 2} sequestration (storage) candidate reservoir. A full reprocessing of the seismic data from field tapes that included prestack time migration (PSTM) followed by prestack depth migration (PSDM) was performed. A baseline reservoir model was generated from the new imaging results that characterized the faults and horizon surfaces of the Crow Mountain reservoir. The 3D interpretation was integrated with the petrophysical data from available wells and incorporated into a geocellular model. The reservoir structure used in the geocellular model was developed using advanced inversion technologies including Fusion's ThinMAN{trademark} broadband spectral inversion. Seal failure risk was assessed using Fusion's proprietary GEOPRESS{trademark} pore pressure and fracture pressure prediction technology. CO{sub 2} injection was simulated into the Crow Mountain with a commercial reservoir simulator. Approximately 1.2MM tons of CO{sub 2} was simulated to be injected into the Crow Mountain reservoir over 30 years and subsequently let 'soak' in the reservoir for 970 years. The relatively small plume developed from this injection was observed migrating ...
Date: December 31, 2011
Creator: Rogers, John
Partner: UNT Libraries Government Documents Department

Operations plan for the Regional Seismic Test Network

Description: The Regional Seismic Test Network program was established to provide a capability for detection of extremely sensitive earth movements. Seismic signals from both natural and man-made earth motions will be analyzed with the ultimate objective of accurately locating underground nuclear explosions. The Sandia National Laboratories, Albuquerque, has designed an unattended seismic station capable of recording seismic information received at the location of the seismometers installed as part of that specific station. A network of stations is required to increase the capability of determining the source of the seismic signal and the location of the source. Current plans are to establish a five-station seismic network in the United States and Canada. The Department of Energy, Nevada Operations Office, has been assigned the responsibility for deploying, installing, and operating these remote stations. This Operation Plan provides the basic information and tasking to accomplish this assignment.
Date: May 15, 1981
Partner: UNT Libraries Government Documents Department

Detection and location of multiple events by MARS. Final report. [Multiple Arrival Recognition System]

Description: Seismic data from two explosions was processed using the Systems Science and Software MARS (Multiple Arrival Recognition System) seismic event detector in an effort to determine their relative spatial and temporal separation on the basis of seismic data alone. The explosions were less than 1.0 kilometer apart and were separated by less than 0.5 sec in origin times. The seismic data consisted of nine local accelerograms (r < 1.0 km) and four regional (240 through 400 km) seismograms. The MARS processing clearly indicates the presence of multiple explosions, but the restricted frequency range of the data inhibits accurate time picks and hence limits the precision of the event location.
Date: September 1, 1980
Creator: Wang, J.; Masso, J.F.; Archambeau, C.B. & Savino, J.M.
Partner: UNT Libraries Government Documents Department

Investigation of MAGMA chambers in the Western Great Basin. Final report, 9 June 1982-31 October 1985

Description: This report summarizes efforts made by the Seismological Laboratory toward the detection and delineation of shallow crustal zones in the western Great Basin, and toward the development of methods to accomplish such detection. The work centers around the recently-active volcanic center near Long Valley, California. The work effort is broken down into three tasks: (1) network operations, (2) data analysis and interpretation, and (3) the study of shallow crustal amomalies (magma bodies). Section (1) describes the efforts made to record thousand of earthquakes near the Long Valley caldera, and focusses on the results obtained for the November 1984 round Valley earthquake. Section (2) describes the major effort of this contract, which was to quantify the large volume of seismic data being recorded as it pertains to the goals of this contract. Efforts described herein include (1) analysis of earthquake focal mechanisms, and (2) the classification, categorization, and interpretation of unusual seismic phases in terms of reflections and refractions from shallow-crustal anomalous zones. Section (3) summarizes the status of our research to date on the locations of magma bodies, with particular emphasis on a location corresponding to the map location of the south end of Hilton Creek fault. Five lines of independent evidence suggest that magma might be associated with this spot. Finally, new evidence on the large magma bodies within the Long Valley caldera, of interest to the DOE deep drilling project, is presented.
Date: February 10, 1986
Creator: Peppin, W.A.
Partner: UNT Libraries Government Documents Department

Geothermal ground noise measurements at Roosevelt Hot Springs and Cove Fort, Utah. Final report

Description: The present study was basically aimed at determining the type of noise found around a geothermal reservoir. Six element arrays were used to determine the structure of the noise field and the types of waves present. Arrays were used at both the Roosevelt Hot Springs and Cove Fort areas. The arrays consisted of six seismometers, one in the center and the others evenly spaced on a circle. The interelement array spacing varied from 50 m to 300 m depending on the experiment. The instrumentation and the arrays are discussed in some detail. The theory required to gain an understanding of the results is briefly discussed. (MHR)
Date: September 1, 1978
Creator: Laster, S.J. & Douze, E.J.
Partner: UNT Libraries Government Documents Department

Louisiana Gulf Coast seismicity induced by geopressured-geothermal well development

Description: Continuous microseismic monitoring networks have been established around three US Department of Energy geopressured-geothermal design wells in southwestern Louisiana since summer 1980 to assess the effects well development may have on subsidence and growth fault activation. The results obtained from this monitoring have shown several unusual characteristics associated with Gulf Coast seismic activity. The observed activity is classified into two dominant types, one with identifiable body phases and the other with only surface wave signatures. The latter type comprises over 99% of the reported 1000+ microseismic event locations. The problem with the slow-moving surface-wave signature events is that rainfall and weather-associated frontal passages seem closely related to these periods of seismic activity at all three wells. After relatively short periods and low levels of flow testing at the Parcperdue and Sweet Lake prospects, seismic monitoring has shown little credible correlation to inferred growth fault locations during periods of flow testing. Longer periods and higher volumes of flow testing at the Rockefeller Refuge prospect should provide a truer indication of induced seismicity attributable to geopressured-geothermal development. 4 refs., 5 figs.
Date: January 1, 1985
Creator: Stevenson, D.
Partner: UNT Libraries Government Documents Department

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

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

Southern Appalachian Regional Seismic Network

Description: The seismic activity in the southern Appalachian area was monitored by the Southern Appalachian Regional Seismic Network (SARSN) since late 1979 by the Center for Earthquake Research and Information (CERI) at Memphis State University. This network provides good spatial coverage for earthquake locations especially in east Tennessee. The level of activity concentrates more heavily in the Valley and Ridge province of eastern Tennessee, as opposed to the Blue Ridge or Inner Piedmont. The large majority of these events lie between New York - Alabama lineament and the Clingman/Ocoee lineament, magnetic anomalies produced by deep-seated basement structures. Therefore SARSN, even with its wide station spacing, has been able to define the essential first-order seismological characteristics of the Southern Appalachian seismic zone. The focal depths of the southeastern U.S. earthquakes concentrate between 8 and 16 km, occurring principally beneath the Appalachian overthrust. In cross-sectional views, the average seismicity is shallower to the east beneath the Blue Ridge and Piedmont provinces and deeper to the west beneath the Valley and Ridge and the North American craton. Results of recent focal mechanism studies by using the CERI digital earthquake catalog between October, 1986 and December, 1991, indicate that the basement of the Valley and Ridge province is under a horizontal, NE-SW compressive stress. Right-lateral strike-slip faulting on nearly north-south fault planes is preferred because it agrees with the trend of the regional magnetic anomaly pattern.
Date: August 1, 1994
Creator: Chiu, S. C. C.; Johnston, A. C. & Chiu, J. M.
Partner: UNT Libraries Government Documents Department

United States National Seismographic Network

Description: The concept of a United States National Seismograph Network (USNSN) dates back nearly 30 years. The idea was revived several times over the decades. but never funded. For, example, a national network was proposed and discussed at great length in the so called Bolt Report (U. S. Earthquake Observatories: Recommendations for a New National Network, National Academy Press, Washington, D.C., 1980, 122 pp). From the beginning, a national network was viewed as augmenting and complementing the relatively dense, predominantly short-period vertical coverage of selected areas provided by the Regional Seismograph Networks (RSN`s) with a sparse, well-distributed network of three-component, observatory quality, permanent stations. The opportunity finally to begin developing a national network arose in 1986 with discussions between the US Geological Survey (USGS) and the Nuclear Regulatory Commission (NRC). Under the agreement signed in 1987, the NRC has provided $5 M in new funding for capital equipment (over the period 1987-1992) and the USGS has provided personnel and facilities to develop. deploy, and operate the network. Because the NRC funding was earmarked for the eastern United States, new USNSN station deployments are mostly east of 105{degree}W longitude while the network in the western United States is mostly made up of cooperating stations (stations meeting USNSN design goals, but deployed and operated by other institutions which provide a logical extension to the USNSN).
Date: September 1, 1993
Creator: Buland, R.
Partner: UNT Libraries Government Documents Department