Accession Number:

ADA248940

Title:

Research in Regional Seismology: The Effect of Anisotropy

Descriptive Note:

Scientific rept.

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE EARTH RESOURCES LAB

Report Date:

1991-11-19

Pagination or Media Count:

83.0

Abstract:

The objective of this study is to examine the influence of fracturing and anisotropy in the source medium or near the source of radiation, especially the generation of SV and SH. One effect is scattering near the source. We present a ray-Born method for the computation of scattered wavefields in a general 3-D, anisotropic medium. This approach applied ray methods to the computation of Greens tensors for a background earth model and uses the Born approximation to determine the scattered wavefield from each volume element within a discretized model of heterogeneity. The application of these two approximate methods requires that the background model be relatively smooth compared to a wavelength for the validity of ray theory, but that the scattering heterogeneity have short characteristic length compared to the propagating wavelength for accurate use of the Born approximation. Comparisons of ray-Born results to the complete solution for scattering from an elastic sphere show that this methods works fairly well for wavelengths on the order of five times larger than the length scales typical of the heterogeneity, but then breaks down due to the failure of the Born approximation. With this restriction in mind, the method is applied to a hypothetical layered earth model containing a thin, laterally extensive fracture zone.

Subject Categories:

  • Geology, Geochemistry and Mineralogy
  • Seismology
  • Seismic Detection and Detectors

Distribution Statement:

APPROVED FOR PUBLIC RELEASE