Accession Number : ADP204517

Title :   Seismoacoustic Studies of the Norwegian Sea,

Corporate Author : SCRIPPS INSTITUTION OF OCEANOGRAPHY LA JOLLA CA INST OF GEOPHYSICS AND PLANET ARY PHYSICS

Personal Author(s) : Blackman, Donna K. ; Orcutt, John A.

PDF Url : ADP204517

Report Date : 14 AUG 1995

Pagination or Media Count : 6

Abstract : The U.S. Navy hydrophone arrays (SOSUS) record seismoacoustic events in a range of frequencies which includes earthquake and explosive sources as well as those relevant to submarine detection, for which they were designed. In the Norwegian Sea we compare detection of seismoacoustic events on SOSUS with seismic detection by the arrays on land in Norway. We also study seismic activity along the spreading centers between Iceland and Svalbard in an attempt to discern any difference in levels of seismicity associated with different sections of the ridge system. Currently, we have assigned archive channels to focus on activity along the Mohns ridge. During March 1995 we recorded many T-phases whose sources have been located along the Mohns ridge using beam steering. Analysis of beamformed data for this continuous one-month period revealed several dozen acoustic events emanating from the southern Mohns ridge and about one third that number from the northern Mohns ridge. Part of this difference is probably due to the choice of beams for the archived data, which emphasizes the southern Mohns ridge, but some of the difference likely reflects the current level of magmatic/tectonic activity. About 10% of the recorded T-phases for this period are preceded by an arrival with greater low frequency content, most likely the P-phase. Approximately two dozen acoustic events were recorded by all channels during the March 95 period suggesting a more distant or larger source, possibly a regional or even teleseismic earthquake. Two of these events correspond to regional events listed in the Center for Monitoring Research (CMR) bulletin, both for which P- and T-phases are observed.

Descriptors :   *SEISMIC WAVES, *ARMS CONTROL, *NUCLEAR EXPLOSION DETECTION, *UNDERWATER ACOUSTICS, *ACOUSTIC SURVEILLANCE, SYMPOSIA, VERIFICATION, MONITORING, THRESHOLD EFFECTS, ACOUSTIC DETECTION, SEISMIC DETECTION, BEAM FORMING, ACOUSTIC ARRAYS, HYDROPHONES, EARTHQUAKES, SUBMARINE DETECTION, BEAM STEERING, NORWEGIAN SEA, OCEAN BASINS, TECTONICS, ICELAND.

Subject Categories : Government and Political Science
      Seismology
      Acoustic Detection and Detectors
      Nuclear Weapons

Distribution Statement : APPROVED FOR PUBLIC RELEASE