Accession Number : ADA317358

Title :   Observations of T-Phase Arrivals at Pt Sur and Wake Island.

Descriptive Note : Scientific rept. no. 1,

Corporate Author : SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA

Personal Author(s) : DE Groot-Hedlin, Catherine

PDF Url : ADA317358

Report Date : 15 MAR 1996

Pagination or Media Count : 17

Abstract : We have assembled a large suite of T-phase observations recorded on hydrophones located at Point Sur and Wake Island, in an attempt to understand how acoustic energy from underwater earthquakes is coupled to the sound channel and bow the sound propagates from source to receiver. The events cover a wide range of locations in the North Pacific. We find that T-phases observable at Point Sur are generated only in a limited number of geographical regions, the Aleutian Islands and Kodiak Island regions, south of Japan, and the southern portion of the Kuril Islands region. Too few records have been assembled to date for Wake Island to discern any pattern in the locations of observable T-phases. A signal to noise (SNR) measure was determined for each event. We found that there was no clear pattern in the SNR vs. magnitude when all the events were examined together. We narrowed the region of study to a small cluster of events in the Andreof Island region of the Aleutian Island chain in order to eliminate variables such as source mechanism, transmission path, and event depth. For this limited data set, we found that the SNR as observed at Pt. Sur was more strongly dependent upon event magnitude, however, there was still a considerable degree of scatter. This scatter is probably due to near source effects, such as the slope of the seafloor in the region of the events.

Descriptors :   *MONITORING, *SEISMIC DETECTION, *GEOACOUSTICS, *HYDROPHONES, ACOUSTIC WAVES, SIGNAL TO NOISE RATIO, PATHS, PATTERNS, CALIFORNIA, RANGE(EXTREMES), EARTHQUAKES, NORTH PACIFIC OCEAN, UNDERWATER, ALEUTIAN ISLANDS, ACOUSTIC CHANNELS, WAKE ISLAND.

Subject Categories : Seismology

Distribution Statement : APPROVED FOR PUBLIC RELEASE