HR: 1340h
AN: T33B-0540    [Abstracts]
TI: Characterization of Seismicity of Alaska/Aleutian Subduction Zone
AU: * Dejtrakulwong, P
EM: p-dejtrakulwong@northwestern.edu
AF: Northwestern University, Dept. Geological Science 1850 Campus Dr., Evanston, IL 60208-2150 United States
AU: Montesi, L
EM: montesi@whoi.edu
AF: Woods Hole Oceanographic Institution, Dept. Geology and Geophysics WHOI MS24, Woods Hole, MA 02543 United States
AU: Rondenay, S
EM: rondenay@mit.edu
AF: Massachusetts Institute of Technology, Dept. Earth Atmospheric and Planetary Sciences MIT 54-512, Cambridge, MA 02139 United States
AB: Seismicity of the main thrust of subduction zones presents much evidence of lateral heterogeneities. By contrast, deeper seismicity is less well understood. Most studies have focused on across-strike variations of seismicity such as double seismic zones. In this project, we characterize along-strike variations of intermediate depth seismicity in the Alaska/Aleutian subduction zone using cluster analyses to improve our understanding of stress sources and slab mechanics. Our dataset is limited to earthquakes of magnitude larger than 4.0 and focal point deeper than 50 km. The two most successful methods are the Gath-Geva algorithm, a fuzzy clustering technique, and the Gaussian mixture model. To a large extent, the two methods agree with each other. The two most robust clusters are located near the eastern end of Alaska subduction zone. By comparing our results to the study of Ratchkovski and Hansen (2002), the easternmost cluster corresponds to their segment C of the subducting plate. This suggests that this cluster may be related to a material heterogeneity in the subducting plate or increased stress due to the differential motion of the neighboring segment. The second easternmost cluster does not correspond to a previously identified feature of the subduction zone. Two to four additional clusters are located near 180° longitude. The rupture zones of the 1957 great Aleutian and 1965 Rat Islands earthquakes abut at the same longitude. The anomalous seismicity of this area may be related to a slab tear, possibly due to the collision between the Bowers ridge and the subduction zone. The anomalous focal mechanism of the 1906 Aleutian earthquake that occurred in that area is an additional evidence for this tear.
DE: 3235 Persistence, memory, correlations, clustering (3265, 7857)
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 8166 Stresses: deep-seated
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
SC: Tectonophysics [T]
MN: Fall Meeting 2005