Seismic Discrimination at Regional Distance.
Abstract
The research supported by this grant is directed towards the general problems of discrimination and yield estimation. During the past year has evolved along two lines: 1) analysis of stress variation within the crust and its possible effects on tectonic release; and 2) effects of large scale mantle structure and crustal focusing/defocusing on parameters such as m, trace amplitude, period and t over short distances near the Faultless shot point. In section I and appendix A, the effects of stress distribution within the Great Basin crust are examined. Detailed studies of focal mechanisms for several areas in the western Great Basin show a systematic change from strike-slip motion at shallow depths to oblique or normal slip at depth. Explosions detonated in Nevada show asymmetric Rayleigh wave radiation and significant Love wave excitation, usually consistent with a strike-slip mechanism. This has been puzzling in an extensional tectonic environment, where major earthquakes are known to have primarily dip-slip motion. However, it is entirely consistent with our observation that small-to-moderate earthquakes at shallow depth in the western Great Basin are predominantly strike-slip. An explanation for this behavior is provided in terms of rotation of the axis of maximum compressive stress due to increasing overburden pressure with depth.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 21, 1983
- Accession Number
- ADA127430
Entities
People
- Alan S. Ryall
- Keith F. Priestley