Accession Number : ADP204514

Title :   Determination of Near-Station Crustal Structure and the Regional Seismic Event Location Problem,

Corporate Author : TEXAS UNIV AT AUSTIN INST FOR GEOPHYSICS

Personal Author(s) : Zhao, Lian-She ; Frohlich, Cliff

PDF Url : ADP204514

Report Date : 14 AUG 1995

Pagination or Media Count : 10

Abstract : Since crustal structure strongly influences the character of regional seismic waveforms, a knowledge of near-station crustal structure is necessary for obtaining single-station event locations of small (M-3) seismic events. In this study we demonstrate that it is practical to use a receiver-function method for determining near-station crustal structure; then, we then use this structure as a basis for constructing synthetic waveforms, and determine single-station regional event locations by comparing the synthetic and observed waveforms. Our receiver-function approach for determining crustal structure utilizes vertical-component P-group waveforms from teleseismic events as input for synthesizing a radial-component waveform for a trial, layered, near-station crustal model. Then, we compare the synthetic and observed radial-component waveforms, and change the crustal model until they are sufficiently similar. To improve efficiency we have implemented several features in our software: For synthesizing radial-component waveforms from vertical-component data we employ a theoretical approximation which is exact to second order in the reflection and transmission coefficients; thus, we call this second-order, radial-vertical comparison the SORVEC method; For synthesizing reverberation waveforms for a n-layer-over-a-halfspace crustal model we show it is generally sufficient to calculate amplitudes for only (6n+l) carefully selected rays; To determine crustal structure we have developed an inversion scheme which utilizes a very fast simulated annealing (VFSA) algorithm which is much faster than grid-search methods, Monte-Carlo methods, or ordinary simulated annealing methods. Using the SORVEC-VFSA algorithm we have determined flat-layered crustal models beneath 12 seismic stations, one (PAS) in California and 11 in Tibet.

Descriptors :   *SEISMIC DETECTION, *EARTH CRUST, *SEISMIC WAVES, *ARMS CONTROL, *NUCLEAR EXPLOSION DETECTION, COMPUTER PROGRAMS, ALGORITHMS, POSITION(LOCATION), SYMPOSIA, SURFACE WAVES, VERIFICATION, MONITORING, UNDERGROUND EXPLOSIONS, MONTE CARLO METHOD, NUCLEAR EXPLOSION TESTING, CALIFORNIA, SEISMIC DISCRIMINATION, EARTHQUAKES, REVERBERATION, CHINA, PRIMARY WAVES(SEISMIC WAVES), SEISMOLOGICAL STATIONS, SECONDARY WAVES.

Subject Categories : Government and Political Science
      Seismology
      Seismic Detection and Detectors
      Nuclear Weapons
      Geology, Geochemistry and Mineralogy
      Computer Programming and Software

Distribution Statement : APPROVED FOR PUBLIC RELEASE