Accession Number : ADA195468

Title :   Discrimination Studies Using Short-Period P Waves at Upper Mantle Distances.

Descriptive Note : Annual rept. Jan 86-Jan 87,

Corporate Author : SIERRA GEOPHYSICS INC KIRKLAND WA

Personal Author(s) : Given, J W ; Ihnen, S M ; Mellman, G R ; Tucker, W C

PDF Url : ADA195468

Report Date : Jan 1988

Pagination or Media Count : 82

Abstract : This report reviews the properties of seismograms recorded at upper mantle distances in stable continental region such as northwest Eurasia in order to examine how well current models predict the general behavior of the observations and to see how much unmodeled energy, or noise, is present. In general The proposed models for the region predict the major arrivals observed in the data. For explosions, there are few distinct arrivals that are not associated with some predicted upper mantle phase. However, noise levels (or code amplitudes), are large, since each arrival has a code associated with it that adds constructively at the receiver. Use predicted coda amplitudes, in a Pearce algorithm to discriminate on the basis of focal mechanism. Given good azimuthal coverage of an event (e.g., 3 of 4 quadrants), the observed complexity of the explosion seismograms is incompatible with that predicted for earthquakes at depth using simple models for the reflection of the depth phases pP and sP. These results are similar to previous findings that considered teleseismic data.

Descriptors :   *DISCRIMINATION, *EARTH MANTLE, *PRIMARY WAVES(SEISMIC WAVES), *SEISMIC DATA, AMPLITUDE, AZIMUTH, CODING, DEPTH, EARTHQUAKES, EXPLOSIONS, LEVEL(QUANTITY), LONG RANGE(DISTANCE), MATHEMATICAL MODELS, NOISE, PHASE, REGIONS, REPORTS, SHORT RANGE(TIME), STABILITY, ALGORITHMS, ARRIVAL, RANGE(DISTANCE), AUTOCORRELATION, FOCUSING, NUCLEAR EXPLOSION TESTING, MONITORING, STRUCTURAL PROPERTIES, VELOCITY

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE