| E. Kazakh-AEDS t*. General Linear Model Magnitude Studies. Dynamic (Amplitude) Criteria for Automatic Association. Synthetic Data for Evaluation of Automatic Association |
30 APR 1983 |
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| Authors:
R. R. Blandford; Z. A. Der; J. Goncz; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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 | Several short studies were undertaken to investigate questions of interest in magnitude:yield and automatic association. Approximately 150 t values were computed for AEDS-E. Kazakh paths, and t corrections for the AEDS stations were obtained. Application of the general linear model to shots in granite and sandstone-shale in the United States showed that a single hard-rock curve was inadequate for these two different media. New methods were developed for making use ... |
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| Yield Estimation and Mantle Q |
29 APR 83 |
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| Authors:
Zoltan A. Der; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Spectral analysis of P waves crossing the mantle under various test sites has revealed considerable variations in the attenuative properties of the mantle which must be considered when computing yields of nuclear explosions. The t* bias between the NTS and Kazakh test sites must be in the range 0.2 to .3 sec. There are indications of anomalous zones of attenuation under the French test sites in the Sahara and near ... |
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| Seismic Data Analysis Center |
10 JAN 1983 |
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| Authors:
Paul Kovacs; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| The effort required to operate and maintain the Seismic Data Analysis Center during the fiscal year of 1981 is described in this report. Statistics concerning the operational effectiveness and the utilization of the systems at the Center are also given. The major activities associated with maintaining the operating systems, providing data services, and performing maintenance are discussed. The development effort and improvements made to the stystems supporting the geophysical research ... |
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| Magnitude: Yield for Nuclear Explosions in Granite at the Nevada Test Site and Algeria: Joint Determination with Station Effects and with Data Containing Clipped and Low-Amplitude Signals |
23 FEB 1982 |
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| Authors:
Robert R. Blandford; R. H. Shumway; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| A systematic approach to short-period magnitude estimation has been developed and applied. The approach uses newly developed statistical techniques in the general linear model (GLM) which allow for the problems of clipping and of signals hidden by noise. Measurement procedures are outlined and the overall approach is first applied to four events in granite; PILEDRIVER, SHOAL, SAPHIRE, and RUBIS. The WWSSN short-period network film recordings, with the application of this ... |
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| Seismic Source Identification Research |
09 FEB 1982 |
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| Authors:
D. W. Rivers; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| This report summarizes work performed on seismic source identification research during the contract period 1 May 1980 through 31 March 1981. The work was performed under contract F08606-80-C-0017. The report contains abstracts from the technical reports which summarize the research performed on seismic event identification and the design of an event identification package. (Author) |
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| A Study of Seismic Wave Propagation at Regional Distances in Five Areas of the World |
08 FEB 1982 |
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| Authors:
Z. A. Der; A. O'Donnell; T. W. McElfresh; R. Jutila; J. A. Burnetti; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Propagation and excitation of regional phases in southern Africa, the southwestern United States, the Pakistan-India region, South America, and the Kamchatka-Kuriles region were studied. Comparison of the shield areas of South America, Pakistan and southern Africa reveals no appreciable differences in the excitation and attenuation of regional phases in these areas. On the other hand, excitation and attenuation rates for all regional phases are markedly different in the southwestern United ... |
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| Definition of Seismic Signal Parameters by Particle-Motion Processing |
22 JAN 1982 |
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| Authors:
D. H. von Seggern; M. E. Marshall; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Theoretical and observed particle motion of P and Lg waves indicates that a successful definition of signal parameters can be made by particle-motion algorithms. Tests on many Pn, Pg, and P phases recorded at OB2NV and RKON reveal that back azimuths can be estimated almost always to within + or - 20 deg at S/N > 5 and quite often to this precision at S/N < 5. Incidence angles are ... |
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| DISE, an Interactive Discrimination Program for Seismic Events |
18 DEC 1981 |
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| Authors:
D. VON Seggern; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| DISE (Discrimination and Identification of Seismic Events) is an interactive computer program with graphics support and currently runs on a VAX- 11/780 computer at the SDAC. Using various commands which are available, the seismic analyst may employ location data or waveform measurements to identify unknown events. Groups of epicenters may be formed, and a lower level of subgroups is formed when particular stations or variables are selected for discrimination purposes. ... |
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| Single Channel Seismic Event Detection on Alaskan Short-Period Data |
11 DEC 1981 |
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| Authors:
Robert R. Blandford; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Three advanced detectors and a standard detector were tested on 15 of the weakest 40 teleseismic signals associated to events and received at an array in Alaska in the time interval 1-6 November 1980. The signals were originally detected on array beams and the detectors were given the task of detecting the signals on data from a single instrument. The false alarm rate was set at 3 to 4 per ... |
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| Evaluation of Seismic Event Location Methods on the Regional Event Location System (RELS) |
26 NOV 1981 |
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| Authors:
A. C. Chang; D. W. Rivers; J. H. Goncz; J. A. Burnetti; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Several location methods developed at SDAC are evaluated by comparing location errors of these methods against errors computed with the standard method. The new methods include: Using P travel times in laterally heterogeneous media: A station travel time residual correlation matrix in the normal equations; Location with simultaneous determination of Pn, Pg, and Lg velocities; Combination of the correlation matrix method and the simultaneous determination method. All the methods evaluated ... |
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| Analysis of Techniques for Application of Magnitude Corrections Developed by Marshall, Springer, and Rodean |
12 NOV 1981 |
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| Authors:
Robert R. Blandford; Zoltan A. Der; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Analysis of the procedures recommended by Marshall, Springer an Rodean (1979) for correction of explosion magnitude due to pP and absorption shows that the techniques are needed and are generally satisfactory. However, the pP correction could be made more accurate and operationally applicable, and the absorption correction needs further checking and perhaps a different approach. A new attack on the general problem is recommended in order to properly treat problems ... |
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| Results of the SDCS (Special Data Collection System) Attenuation Experiment |
30 OCT 1981 |
277 pages |
| Authors:
Z. A. Der; T. W. McElfresh; A. O'Donnell; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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 | Investigation of teleseismic arrivals at test sites in the western United States (WUS), a site on the Canadian shield and two sites in the northeastern United States revealed marked differences in mantle attenuation among these sites. All sites in the WUS show high attenuation in the underlying mantle, the sites in the northeastern U.S. appear to be intermediate between the WUS and the shield sites. This pattern fits well into ... |
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| Q of the Earth in the 0.5-10Hz Band |
16 OCT 1981 |
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| Authors:
Z. A. Der; D. W. Rivers; T. W. McElfresh; A. O'Donnell; P. J. Klouda; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| The study of spectral characteristics of short period body waves using a worldwide data set indicates that the high frequency fall-off rates of body wave spectra correlate with the tectonic regime of the upper mantle structures traversed. The study also shows, in a consistent manner, that this is due to lateral variations of omega in the mantle. The magnitude of the worldwide omega variations in the mantle is of the ... |
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| Single Channel Seismic Event Detection |
07 OCT 1981 |
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| Authors:
Robert R. Blandford; David Racine; Raleigh Romine; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Several types of seismic signal detectors have been tested on NORSAR and Pinedale, Wyoming signals buried every ten minutes in approximately 22 hours of phase-scrambled noise. All plausible detectors including human analysts operate within 0.1 mb of the mean value including the present on-line 'IBM' STA/ LTA detector, a 'Z' detector, detectors with fixed or optimum filters, a 'deflection' detector, the MARS detector, a detector which cascades a recursive digital ... |
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| Regional Phase Processors |
07 OCT 1981 |
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| Authors:
Eugene Smart; Helene Sproules; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| The purpose of this study is to evaluate the principle of the technique known as the Smart processor, developed at the SDAC (Smart, 1977) and to determine the propagation direction of regional seismic phases by operating on a comprehensive data set. The Smart single-station maximum-likelihood surface-wave processor and variants thereof, all relying on three-component particle-motion analysis, demonstrated in this study their utility for automatic signal azimuth determination. In this study ... |
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| Regional Amplitude-Distance Relations, Discrimination and Detection |
13 JUL 1981 |
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| Authors:
Robert Blandford; R. Hartenberger; R. Naylor; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| This paper begins with a review of the literature on propagation of Pn, Pg, Sn, Lg, and Rg and continues with the history of discrimination at regional distances up to 1978. New work performed especially for this report is discussed next; distance amplitude relations for Pn, Pg, Lg and for the maximum amplitude observed before and after Sn are presented for earthquakes and explosions in both the Eastern United States ... |
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| Seismic Data Analysis Center |
22 JUN 1981 |
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| Authors:
Paul Kovacs; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| The operation and maintenance of the Seismic Data Analysis Center (SDAC) are summarized for the contract year beginning 1 October 1978 and ending 30 September 1979. Reported are the statistics relating to computer usage; information relating to the maintenance, programming, data services, data availability; and the effort to expand the research systems at the facility. This final report summarizes the operation and maintenance of the computer systems at the Seismic ... |
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| Evaluation of the Communications Control Processor. |
07 MAY 1981 |
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| Authors:
W. C. Dean; d. m. miller; R. P. Colella; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| This report evaluates the role of the pluribus, a multiprocessor/multibus system, in its role as the communications control processor (CCP) at the Seismic Data Analysis Center (SDAC) over the 26 months from its installation in April 1977 through May 1979. In capacity the six processor Pluribus at the SDAC provides a bandwidth somewhat greater than 750,000 instructions per second, equivalent to three processors working full time. For the 16.8 KB/sec ... |
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| I. The Detectability of High Frequency Energy at Teleseismic and Regional Distances. II. Studies of Radiation from High-Explosive and Nuclear Cratering Events |
04 MAR 1981 |
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| Authors:
Zoltan A. Der; R. R. Blandford; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| A survey of the literature on short-period seismic studies shows that seismic waves of high frequency in the 3-10 Hz range, can be observed regularly at both regional and teleseismic distances. These observations show that the low Q values proposed for the long-period seismic waves cannot be valid in the short-period band. The data indicate that, in the mantle, Q increases with frequency and may be as much as five ... |
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| Use of Back Azimuth Measurements in Seismic Event Location with Regional Data |
09 JAN 1981 |
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| Authors:
D. W. Rivers; J. A. Burnetti; A. C. Chang; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Conventional methods for seismic event location, which are based on measurements of signal arrival times, may be inadequate for events detected at only regional distances, because there may be an insufficient number of observations. This shortcoming can be alleviated by supplementing the measurements of P-wave arrival times with measurements of the event's back azimuth made by applying Smart's (1978) three-component processor to the regional phase Lg. Back azimuth measurements can ... |
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| Improved Location with Regional Events |
DEC 1980 |
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| Authors:
A. C. Chang; D. W. Rivers; J. A. Burnetti; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Three methods of locating events with regional phases were tested and compared for accuracy of hypocenter determination. A modified HYLO method was found to be slightly less accurate than a standard location algorithm using a Herrin 68 earth model. In addition, we found that the modified HYLO method requires a much more detailed knowledge of the earth's crust and upper mantle than is generally available. Two methods which do not ... |
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| SDAC Final Report, 1 October 1979-30 September 1980 |
NOV 1980 |
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| Authors:
Paul Kovacs; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| The effort required to operate and maintain the Seismic Data Analysis Center for the contract period beginning 1 October 1979 and ending 30 September 1980 is summarized in this report. Statistics on the use of the computer systems and the seismic data received, stored and maintained at the center are also tabulated. Tasks performed under this contract included the operation of digital computers and analog systems, the programming to maintain ... |
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| Effect of Crustal Structure on Lg |
09 OCT 80 |
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| Authors:
D. W. Rivers; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| The transverse component of the regional phase L sub g was synthesized by the superposition of higher-order Love-wave modes at frequencies of up to 2.5 Hz. The synthetic seismograms represent the signals which would be generated by earthquakes at various depths in a tectonic shield. Two alternative earth models were also used: one in which the shield structure was overlain by 2 km of low-velocity sediments, and another in which ... |
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| A Statistical Discrimination Experiment for Eurasian Events Using a Twenty-Seven-Station Network |
08 JUL 1980 |
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| Authors:
D. W. Rivers; D. H. von Seggern; B. L. Elkins; H. S. Sproules; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| An experiment was performed to test the effectiveness of a multivariate method of analysis for distinguishing earthquakes from explosions. The data base for the experiment consisted of digital recordings made at twenty- seven stations, including four large arrays, of one hundred thirty-three Eurasian events. Spectral magnitudes were measured in three frequency bands of the six phases P, Lg, long-period P, long-period S, LR, and LQ. Complexities of the P-waves were ... |
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| Digital Seismic Data Representations: Gain-Ranging, Precision, System Response, Seismic and Computer Considerations |
31 MAR 1980 |
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| Authors:
Robert Blandford; Paul Kovacs; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Because of trends toward increasingly precise analog-to-digital converters, we recommend that the data storage standard for the Seismic Data Analysis Center be a 16-bit word that is gain-ranged or becomes a 32-bit word only when necessary. There is no problem in converting any existing input format to this format. The amount of additional archival storage media used will be insignificant and rapid access can be assured. The primary disadvantage is ... |
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| Seismic Data Analysis Center. Final Report |
11 DEC 1979 |
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| Authors:
Robert R. Blandford; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| This report provides information and statistics concerning the operation and maintenance of the computer systems at the SDAC, a consideration of the abstracts from the technical reports resulting from studies and seismic research, and a summary of the work accomplished to expand the computer systems and programs used for the VELA Network. |
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| Seismic Discrimination of Earthquakes and Explosions, with Application to the Southwestern United States. |
22 MAR 1979 |
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| Authors:
D. H. von Seggern; D. W. Rivers; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| This study examines seismic discrimination between underground nuclear explosions and earthquakes in the Southwestern United States. A thorough review of theoretical and applied research on this problem, especially as it relates to that region, is presented first, followed by a presentation of the seismic discrimination parameters computed for a suite of events in the Southwest and a series of experiments with multi-dimensional discrimination. Review of past work finds some theoretical ... |
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| Detection of Depth Phases Using Computer Graphics. |
05 DEC 1978 |
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| Authors:
John H. Goncz; Brian W. Barker; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| From a dataset of 116 earthquakes, all available SRO (Special Research Observatory) and PSWF (Preliminary Signal Waveform File) waveforms were presented on an interactive computer graphics screen and then examined for presence of depth phases pP, sP and PcP. Using the results, a focal depth for 66% of the total was postulated. About half of these, or 37%, agreed with depths published by NEP (Network Event Processor) or PDE (Preliminary ... |
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| PKP Travel Times and B Factors. |
24 OCT 1978 |
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| Authors:
Andre C. Chang; John W. Lambert; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Using Jordan and Anderson's earth model B1, we calculated theoretical travel times, depth allowance tables, branch interval times, and B factors for all PKP phases; the results are in tabular form. Travel times are calculated with polynomial approximations, and those coefficients are also computed. New additions to those tables are the data for the CD branch, which are the PKiKP arrivals in the distance range of 109 to 158 deg. ... |
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| Analysis of Selected Seismic Events from Asia in a Seismic Discrimination Context. |
21 SEP 1978 |
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| Authors:
P. A. Sobel; D. H. von Seggern; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| This study examines earthquakes in Kamchatka, the Tien Shan, the Pamirs, the Baikal rift zone, and the Caucasus and explosions in the Aleutians, East Kazakh, West Kazakh, Southwest Russia, Lop Nor, and Baikal in a seismic discrimination context. Because of their low magnitudes (m sub b from 4.2 to 6.0 and M sub s from 3.2 to 5.8) and their varying propagation effects, it was impossible on the basis of ... |
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| A Three-Component, Single-Station, Maximum-Likelihood Surface Wave Processor. |
21 JUL 1978 |
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| Authors:
Eugene Smart; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| An entirely analytic single-station surface-wave processor is developed that analyzes long-period seismic records two orders of magnitude faster than real tme on an IBM 360/44 computer. In processing four days of continuous synthetic data the algorithm detected 85% of the 170 signals of S/N = 1/2, with false alarm rate of one per day. A novel detection theory is introduced that exploits the consistency of the azimuthal estimates associated with ... |
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| Seismic Data Analysis Center Final Report. |
17 JUL 1978 |
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| Authors:
Robert R. Blandford; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| The objectives of this work were to: (1) operate, program, and maintain real time and batch processors; (2) provide services to other government agencies and VELA participants; (3) conduct research in seismology; and (4) develop systems to control and process seismic information generated by remote stations in the Expanded VELA Seismic Network. Network development tasks included refining and developing the Detection Processing System (DPS) and completing efforts to make the ... |
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| A Comparison of Teleseismic P Wave Amplitudes and Spectra Observed at Selected Basin and Range Sites and in Eastern North America. Phase 1. Volume 1. |
30 MAY 1978 |
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| Authors:
Z. A. Der; M. S. Dawkins; T. W. McElfresh; J. H. Goncz; C. E. Gray; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Three Seismic Data Collection System (SDCS) stations were deployed at the Nevada Test Site (NTS) and two in the Eastern United States (EUS) to measure magnitude residuals and spectral differences between NTS and EUS stations. The deployment was intended to determine the degree of anelastic attnuation under NTS. At the Climax Stock (OB2NV) station, the teleseismic body-wave magnitudes are .17 magnitude units (m.u.) lower than at the EUS stations. The ... |
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| A Comparison of Teleseismic P Wave Amplitudes and Spectra Observed at Selected Basin and Range Sites and in Eastern North America. Phase 1. Volume 2. |
30 MAY 1978 |
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| Authors:
Z. A. Der; M. S. Dawkins; T. W. McElfresh; J. H. Goncz; C. E. Gray; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Three Seismic Data Collection System (SDCS) stations were deployed at the Nevada Test Site (NTS) and two in the Eastern United States (EUS) to measure magnitude residuals and spectral differences between NTS and EUS stations. The deployment was intended to determine the degree of anelastic attenuation under NTS. At the Climax Stock (OB2NV) station, the teleseismic body-wave magnitudes are .17 magnitude units (m.u.) lower than at the EUS stations. The ... |
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| On Detecting and Estimating Multiple Arrivals from Underground Nuclear Explosions. |
25 MAY 1978 |
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| Authors:
R. H. Shumway; R. R. Blandford; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Nine explosions were used to study the problem of specifying the number and characteristics of the arrival phases of nuclear explosion. Tentative identification of the amplitudes and time delays of the multiple arrivals are given. The method used is to scan the likelihood (L) for a single reflection model over amplitude (a) and time delay (tau). The likelihood is constructed in the frequency domain using von Seggern and Blandford's (1972) ... |
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| Intersite Magnitude-Yield Bias Exemplified by the Underground Nuclear Explosions MILROW, BOXCAR and HANDLEY. |
05 MAY 1978 |
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| Authors:
D. H. von Seggern; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Estimates of surface-wave and body-wave magnitude were made from all available teleseismic WWSSN recordings of the Nevada Test Site shots BOXCAR and the Amchitka Test Site shot MILROW, in the megaton range of yield. These shots had very closely matched medium properties at the shot point. Tectonic strain release is not a significant factor in the amplitudes of either set of waves for these two shots. When averaged over common ... |
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| A study of Amplitude Variations and m sub b Bias at LASA Subarrays. |
01 MAY 1978 |
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| Authors:
A. C. Chang; D. H. von Seggern; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| LASA subarray amplitude anomalies are investigated using 395 medium-sized events, distributed in ten azimuthally divided sectors. Although LASA magnitudes, when averaged over all azimuths, are only slightly biased relative to NEIS magnitudes, the amount of bias varies with azimuth and subarray, suggesting that a simple station correction for m sub b bias is not adequate. In addition, fluctuations among LASA subarrays are about 0.15 in standard deviation, even when these ... |
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| The Effects of Spall on m(b) and M(s). |
04 APR 1978 |
64 pages |
| Authors:
P. A. Sobel; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| This study examines near-field observations of spalling, a phenomenon associated with most underground nuclear explosions, and attempts to estimate its effects on m sub b and M sub s. Observations of spall on near-field accelerometers and partical velocity records were used to examine possible relationships between radius of spallation, estimated spall thickness, maximum height attained by spall at the surface, shot depth of burial and yield. |
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| Methods of Automating Routine Analysis Tasks in Preparing a Global Seismic Bulletin. |
13 DEC 1977 |
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| Authors:
D. H. von Seggern; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Although it permits more rapid seismic data processing than before being implemented, the Network Event Processing (NEP) system at the Seismic Data Analysis Center could still perform more routine analysis tasks automatically. This report discusses these tasks, including: identification of false alarms in detection lists, timing of P and LR/LQ arrivals, associating seismic arrivals to events, depth-of-focus estimation, and measurement of magnitude. Approaches to automating these tasks are presented, tested, ... |
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| Study of Selected Events in the Caucasus in a Seismic Discrimination Context. |
07 NOV 1977 |
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| Authors:
P. A. Sobel; D. H. von Seggern; E. I. Sweetser; D. W. Rivers; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Eight earthquakes from the Caucasus occurring from 1971 to 1975 were examined in a seismic discrimination context. Seismograms from ALPA, LASA, NORSAR, and the HGLP and the WWSSN stations were studied for source mechanism, (M sub s - M sub b), corner frequency, pP, complexity, and spectral ratio. All the Caucasus events can be identified as earthquakes by means of pP and M sub s:M sub b when compared to ... |
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| Study of Selected Events in the Baikal Rift Zone in a Seismic Discrimination Context. |
17 OCT 1977 |
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| Authors:
P. A. Sobel ; D. H. von Seggern; E. I. Sweetser; D. W. Rivers; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Six events from the Baikal rift zone occurring from 1971 to 1975 were examined in a seismic discrimination context. Seismograms from ALPA, LASA, NORSAR, the HGLP, the WWSSN, and the SRO stations were studied for source mechanism, Ms-mb, corner frequency, pP, complexity, and spectral ratio. All the Baikal events can be identified as earthquakes except the November 5, 1976, event which shows explosion characteristics. The characteristics of the Baikal events ... |
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| Study of Selected Events in the Pamirs in a Seismic Discrimination Context. |
10 OCT 1977 |
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| Authors:
P. A. Sobel; D. H. von Seggern; E. I. Sweetser; D. W. Rivers; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Eleven earthquakes with low reported M sub s for their m sub b from the Northern Pamirs were examined in a seismic discrimination context. Seismograms from ALPA, LASA, NORSAR, the HGLP and the WWSSN stations were studied for source mechanism, M sub s-m sub b, corner frequency, pP, complexity, and spectral ratio. All the Parmir events can be identified as earthquakes when their characteristics are compared to those of Kazakh ... |
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| Summary of Short-Period Explosion and Earthquake Coda Shapes with Implications for Regional Discrimination. |
26 SEP 1977 |
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| Authors:
Robert Blandford; M. F. Tillman; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| This report presents a collection of small and large earthquake short-period coda shapes as a function of distance. It is summarized from previous studies by Cohen, Sweetser, and others. New results include coda shapes for delta < 20 deg. The report is intended to serve as a reference for workers who investigate problems related to hiding an explosion in an earthquake. A detailed examination of earthquake and explosion coda also ... |
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| Observed Variation in the Spectral Ratio Discriminant from Short-Period P Waves. |
19 SEP 1977 |
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| Authors:
D. H. von Seggern; R. R. Blandford; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Short-period P-wave first arrivals recorded at the Large Aperture Seismic Array in Montana from a large number of teleseismic events were filtered in the bands of 0.4-3.0, 0.4-0.8, 1.4-1.8, and 1.8-4.0 Hz. Estimates of signal amplitude in each band were used to form spectral ratios similar to those which have been proposed as discriminants between earthquakes and underground nuclear explosions. Values for the ratios scattered over nearly two orders of ... |
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| Teleseismic P-Wave Amplitudes and Spectra at NTS and at the Shoal Site as Compared to those Observed in Eastern North America. |
02 SEP 1977 |
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| Authors:
Z. A. Der; M. S. Dawkins; T. W. McElfresh; J. H. Goncz; C. E. Gray; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
|
| Three Special Data Collection System (SDCS) stations were deployed at NTS to Measure magnitude residuals and spectral differences relative to two Eastern United States (EUS) stations in order to determine the degree of anelastic attenuation under NTS. At the NTS station located on the Climax stock (OB2NV), the average teleseismic body-wave magnitude is .13 magnitude units (m.u.) lower than at HNME and .19 m.u. lower than at RKON. The magnitudes ... |
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| Study of Selected Kamchatka Earthquakes in a Seismic Discrimination Context. |
16 AUG 1977 |
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| Authors:
D. H. von Seggern; P. A. Sobel; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Seismic discrimination in the Kamchatka source region is studied using data from earthquakes, inferences from measurements of teleseismic explosions, and results from the Amchitka tests. On the basis of several parameters taken together, such as M sub s - m sub b, spectral ratio, corner frequency, complexity, long-period body-wave excitation, and shear-wave excitation, discrimination of events of this type in the Kamchatka region poses no special problems so long as ... |
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| The Effect of Crustal Structure on Station Magnitude Anomalies (Magnitude Bias). |
02 AUG 1977 |
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| Authors:
Zoltan A. Der; Thomas W. McElfresh; Charmaine P. Mrazek; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| The amplification of P wave amplitudes by the receiver crustal structure was modelled for 34 LRSM stations by using crustal structures derived from geological and geophysical information in the literature. Crustal amplification was found to be linearly related to the acoustical impedance in near surface materials at each site. Correlation of the crustal amplification, expressed in magnitude units, with the magnitude residuals of Booth, Marshall and Young (1974) is statistically ... |
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| On the Existence, Magnitudes and Causes of Broad Regional Variations in Body-Wave Amplitude. |
19 MAY 1977 |
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| Authors:
Zoltan A. Der; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| This report is a review of evidence for anomalous attenuation of short-period seismic body-waves in the upper mantle under the Western United States. The attenuation reduces the amplitudes of these waves by a factor of about two relative to those observed in stable, continental shield type areas. The magnitude of this amplitude anomaly is consistent with spectral differences of body-waves observed in the same region, assuming a simple exponential attenuation ... |
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| Empirical m sub b:M sub s Relations at the Nevada Test Site with Applications to m sub b-Yield Relations. |
20 APR 1977 |
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| Authors:
R. R. Blandford; M. F. Tillman; D. P. Racine; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| Measurements have been made of first-motion amplitude and of the period and amplitude of the second peak-to-trough excursion (termed the c phase) for short-period vertical P-wave signals from approximately 60 Nevada Test Site (NTS) explosions. They were recorded at the Long-Range Seismic Measurement (LSRM) and Seismic Data Collection System (SDCS) stations in Houlton, Maine (HNME), and Red Lake, Ontario (RKON). Almost all events selected were detonated in saturated tuff or ... |
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| Seismic Data Analysis Center. |
01 NOV 1976 |
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| Authors:
Royal A. Hartenberger; TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA ANALYSIS CENTER
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| The Alexandria Laboratories Division of Teledyne Geotech operated the Seismic Data Analysis Center (SDAC) during the fifteen (15) month period beginning 1 July 1975 and ending 30 September 1976. The objectives of the work were (1) to operate, program, and maintain real-time and batch processors; (2) to provide services to other government agencies and VELA participants; (3) to conduct research in seismology; and (4) to develop systems to control and ... |
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Reports by Corporate Author
