Accession Number : ADP204459

Title :   Regional Seismic Wavefield Modeling with a Generalized Pseudospectral Method,

Corporate Author : COLORADO UNIV AT BOULDER DEPT OF PHYSICS

Personal Author(s) : Orrey, Jeffrey ; Archambeau, Charles

PDF Url : ADP204459

Report Date : 14 AUG 1995

Pagination or Media Count : 9

Abstract : In this study we apply a numerical modeling method to predict and analyze discriminatory seismic signals in realistic models of the crust and to characterize wave propagation effects as fluctuations of source and medium characteristics. The numerical method we use is the recently-developed generalized Fourier method (GFM). Based on the standard Fourier pseudospectral method, the generalized method exhibits optimal gridpoint-per-minimum-wavelength sampling and no numerical dispersion from spatial approximations. In addition, the highly accurate interface boundary condition approximations in GFM makes the method very useful for the study of the regional propagation of the discriminatory phase Lg and the effects of source and structure characteristics on the relative strengths of Lg and Rg, as well as crustal body wave phases. Furthermore, the method's computational efficiency, from the standpoint of machine storage requirements, makes possible relatively broadband simulations, relative to lower-order finite difference and finite element simulations, in both two and three dimensions. Numerical simulations are performed to systematically determine the effects of random (small scale) and coherent (large scale) heterogeneities, anelasticity (without a weak attenuation limitation), and irregular layer topography on the energy partitioning between important seismic phases, such as Pg, Lg, and Rg. We find that Rg scattering to Lg is the dominant mechanism determining the relative amplitudes of these phases, and our results suggest the necessity of using fully-heterogeneous 3-D simulations to quantitatively assess the causes and effects of scattering in the crust.

Descriptors :   *SEISMIC DETECTION, *SEISMIC WAVES, *ARMS CONTROL, *NUCLEAR EXPLOSION DETECTION, *SEISMIC DISCRIMINATION, MATHEMATICAL MODELS, SCATTERING, SYMPOSIA, SURFACE WAVES, MONITORING, TOPOGRAPHY, WAVE PROPAGATION, APPROXIMATION(MATHEMATICS), EARTH CRUST, TREATIES, SEISMIC VELOCITY, FOURIER ANALYSIS, PRIMARY WAVES(SEISMIC WAVES), SECONDARY WAVES, SEISMOGRAPHS.

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

Distribution Statement : APPROVED FOR PUBLIC RELEASE