Accession Number : ADP204468

Title :   Synthetic Seismograms in Heterogeneous Media and Study of Formation and Propagation of Regional Phases,

Corporate Author : CALIFORNIA UNIV SANTA CRUZ

Personal Author(s) : Wu, Ru-Shan ; Lay, Thorne ; Xie, Xiao-Bi ; Huang, Lian-Jie

PDF Url : ADP204468

Report Date : 14 AUG 1995

Pagination or Media Count : 8

Abstract : The object of this project is aimed at development and application of a new 3D wave propagation and modeling method in complex heterogeneous media using one-way wave approximation to study many outstanding problems of regional wave propagation in the context of nuclear test monitoring. The great advantages of one-way propagation methods are the fast speed of computation, often by several orders of magnitudes faster than finite difference and finite element methods, and the huge saving in internal memory. The first year's effort is concentrated on developing theory and techniques for fast calculation of reflected or backscattered waves, namely methods of synthetic seismograms using the concept of one-way wave propagation and single interaction. The research effort supported by this contract has produced the following results regarding the backscattered field modeling. Wu and Huang (1995a, b) has introduced a wide-angle modeling method for acoustic waves using the De Wolf approximation and phase-screen propagator. Xie and Wu (1995) introduced a complex screen method for the calculation of backscattered elastic waves under small-angle approximation. Wu (1995) extended the wide-angle method to the case of elastic waves, and derived the relation between the wide-angle method and the screen approximation for the acoustic case. Numerical examples showed excellent results of the method. Comparison of angular dependence of reflection coefficients calculated from synthetic seismograms by this method with the theoretical curves showed good agreement between theory and synthetics. The wide-angle version of the method can even model the critical and post-critical reflections. From the comparison of synthetic seismograms made by this fast method and by finite difference calculations the validly and applicability of the method has been demonstrated.

Descriptors :   *SEISMIC DETECTION, *SEISMIC WAVES, *ARMS CONTROL, *NUCLEAR EXPLOSION DETECTION, *SEISMOGRAPHS, SYMPOSIA, VERIFICATION, MONITORING, ACOUSTIC WAVES, FINITE ELEMENT ANALYSIS, UNDERGROUND EXPLOSIONS, BACKSCATTERING, NUCLEAR EXPLOSION TESTING, FINITE DIFFERENCE THEORY, SEISMIC DATA, WAVE PROPAGATION, EARTH CRUST, HETEROGENEITY, SEISMIC DISCRIMINATION, TREATIES, SEISMIC VELOCITY, ELASTIC WAVES, BORN APPROXIMATIONS.

Subject Categories : Government and Political Science
      Seismology
      Seismic Detection and Detectors
      Nuclear Weapons

Distribution Statement : APPROVED FOR PUBLIC RELEASE