Accession Number:

ADA476024

Title:

The Physical Basis of the Explosion Source and Generation of Regional Seismic Phases

Descriptive Note:

Final rept. 18 Aug 2004-2007

Corporate Author:

SCIENCE APPLICATIONS INTERNATIONAL CORP SAN DIEGO CA

Report Date:

2007-08-31

Pagination or Media Count:

156.0

Abstract:

The goal of this project is to understand explosion generation of shear waves. We quantify contribution of surface reflected pS, S, scattered Rg, and S directly generated by non-spherical source elements to local and regional S-wave phases in high and low velocity source media through simulations and data analysis. Data include a large set of historical local records of Semipalatinsk nuclear explosions digitized for this project by Institute for the Dynamics of the Geospheres IDG in Moscow, Russia, Soviet Deep Seismic Sounding experiments, regional records of NTS explosions, and local and regional Kazakh depth of burial experiment records. Simulations include non-linear, Lagrangian finite-difference calculations to model source generation, 2 and 3D finite-difference calculations to model near source scattering effects, a new modal scattering calculation to estimate the upper on Rg-to-Lg scattering, and wavenumber synthetics for multiple source and propagation effects. We find that source generated S waves dominate the regional S phases for a high velocity source region, and trapped pS dominates Lg for low velocity sources, although direct generation is necessary for Sn. Rg scattering may contribute in both cases, but at lower frequencies 1 Hz.

Subject Categories:

  • Seismology
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE