Seismic Wave Propagation, Attenuation and Scattering over Regional Distances
Abstract
The objective of this project was to conduct basic research on the propagation of seismic energy at regional (100-1000 km) distances for purposes of monitoring underground nuclear explosions. The problems studied were the coherency of the seismic S phases, especially Lg, and the implications in terms of the scattering properties of the earth medium; and scattering from anisotropic inclusions. This Final Report consists of preprints of two papers on these subjects. The first concerns the measurement of coherency of the Sn/Lg phases at distances of 200-400 km for quarry blasts recorded at the Fennoscandian arrays ARCESS, FINESA, and NORESS, and its interpretation. The measurements indicate wavelength scaling of the spatial coherency, i.e., scaling according to the scale of the wave only, in the frequency band 1-10 Hz; the wavelength range is 0.4-2 km. This suggests there is no medium scale in this size range. Numerical experiments with randomized time series demonstrate that spatial coherency is mainly controlled by phase (travel time) variations. Preliminary work with finite difference modelling of these regional phases shows that crustal models with random velocity variations have the potential to explain the observations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 11, 1989
- Accession Number
- ADA219358
Entities
People
- Anton M. Dainty
- Ari Ben-menahem
- Edmond E. Charrette
- Nafi Toksoez
- Richard L. Gibson Jr.
Organizations
- Massachusetts Institute of Technology