Accession Number:

ADA220117

Title:

Modeling Regional Seismic Waves from Underground Nuclear Explosion

Descriptive Note:

Final rept. 17 Mar 1987-31 May 1989

Corporate Author:

CALIFORNIA INST OF TECH PASADENA SEISMOLOGICAL LAB

Report Date:

1989-05-15

Pagination or Media Count:

196.0

Abstract:

The research is divided into three main topics modeling regional SH waves that propagate across lateral variations in structure, modeling explosions using 2-D numerical methods, and the effect of differing P and SV source time histories on the generation of Rayleigh and Love waves. Intermediate-period seismograms of earthquakes occurring along a profile to Imperial Valley are studied in terms of source phenomena versus path effects. Some of the events have known source parameters, determined by teleseismic or near-field studies, and are used as master events in a forward modeling exercise to derive the Greens functions displacements at Pasadena due to a pure strike-slip or dip- slip mechanism that describe the propagation effects along the profile. Both timing and waveforms of records are matched by synthetics calculated from two- dimensional velocity models. The effect of transition regions between continental and oceanic structure on the propagation of Lg waves from continental sources is examined. In particular, the attenuation due to variations in layer thickness in such transition regions is calculated and explained for a suite of simple models. Methods for representation theorem coupling of finite-element or finite difference calculations and propagator matrix method are demonstrated. The resulting hybrid technique can be used to study the propagation of any phase that can be represented in terms of SH mode sum seismogram, across regional transition zones or other heterogeneities.

Subject Categories:

  • Seismology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE