HR: 0800h
AN: G51B-0830    [Abstracts]
TI: Episodic Tremor in the Alaska/Aleutian Subduction Zone
AU: * Peterson, C
EM: chloe@giseis.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, P.O. Box 757320 , Fairbanks, AK 99775 United States
AU: Christensen, D
EM: doug@giseis.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, P.O. Box 757320 , Fairbanks, AK 99775 United States
AU: McNutt, S
EM: steve@giseis.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, P.O. Box 757320 , Fairbanks, AK 99775 United States
AB: Episodic tremor and slip (ETS) has been observed in the Cascadia subduction zone and in the Nankai trough. Low frequency tremorlike seismic signals, which are located at depths of 25-40 km, are often associated with slow slip events on the downdip edge of the interplate coupled zone. These slow slip events have been recognized in data from continuously recording Global Positioning System (GPS) networks. Here we present evidence for similar seismic signals in the Alaska/Aleutian subduction zone. Broadband seismic stations located in southcentral Alaska between 1999-2001 (BEAAR Passcal experiment) were used to identify several instances of seismic tremor. The seismic signals observed consist of a series of bursts lasting between 10 and 15 minutes with frequencies ranging from 1-6 Hz. These signals were recorded over a broad area (>100km) roughly centered above the 50-70 km contour of the subducting Pacific plate. This region was the site of a slow slip event which lasted for several years (1999-2001) and may be related to the tremor episodes. Several possible tremor episodes have also been recorded in the eastern Aleutians on stations of the Makushin and Akutan volcanic networks. These events were identified on spectrograms used to monitor volcanic activity, however, the geographic distribution of stations suggest that the source of these signals does not stem from the volcanoes themselves. Similar to the previously observed tremor episodes, the tremor episodes recorded on the volcanic networks consist of a series of bursts with energy concentrated in the band 1-6 Hz. These episodes last up to six minutes. Although the episodic tremors observed in the Alaska/Aleutian subduction zone are similar to the ETS observed in the Cascadia subduction zone and the Nanakai trough, identifying slow slip associated with tremor in the Alaska/Aleutian subduction zone is difficult because there is no continuously recording GPS network in the region.
DE: 1207 Transient deformation (6924, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7200 SEISMOLOGY
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Geodesy [G]
MN: Fall Meeting 2005