HR: 08:00h
AN: S21C-01    [PDF]
TI: Imaging the Transition From Aleutian Subduction to Yakutat Collision in Central Alaska, With Local Earthquakes and Active Source Data
AU: * Eberhart-Phillips, D
EM: deberhart@usgs.gov
AF: U. S. Geological Survey, 4200 University Dr., Anchorage, AK 99508 United States
AU: Christensen, D H
EM: doug@giseis.alaska.edu
AF: Geophysical Institute, Univ. of Alaska Fairbanks P. O. Box 757320, Fairbanks, AK 99775 United States
AU: Brocher, T M
EM: brocher@usgs.gov
AF: U. S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Dutta, U
EM: ffud@uaf.edu
AF: Env. and Natural Resources Inst., Univ. of Alaska Anchorage 707 A Street, Anchorage, AK 99501 United States
AU: Hansen, R
EM: roger@giseis.alaska.edu
AF: Geophysical Institute, Univ. of Alaska Fairbanks P. O. Box 757320, Fairbanks, AK 99775 United States
AU: Ratchkovski, N A
EM: natasha@giseis.alaska.edu
AF: Geophysical Institute, Univ. of Alaska Fairbanks P. O. Box 757320, Fairbanks, AK 99775 United States
AB: In central Alaska, the rapid subduction and active volcanism of the Aleutian subduction zone gives way to a broad plate boundary zone with mountain building and strike-slip faulting, where the Yakutat terrane joins the subducting Pacific plate. We are imaging the 3-D velocity structure using the abundant local earthquakes, which occur to 200-km depth, supplemented by active source data. Both permanent AEIC (Alaska Earthquake Information Center) stations and temporary BEAAR (Broadband Experiment Across Alaska Range) stations are included. Low velocity in the upper crust correlates with the Cook Inlet and Copper River basins. The relatively high-velocity slab and low-velocity mantle wedge are readily observed. Lower velocity mantle underlies the active volcanism in contrast to higher velocity mantle of the relatively undeformed southwestern Alaska area further inboard of the arc. In the region north of Cook Inlet, a low-velocity zone overlies the shallow slab to about 80-km depth and may represent the underthrust Yakutat terrane, consistent with BEAAR receiver function and attenuation results. The subduction of thick crust in central Alaska at the end of a subduction zone is similar to the northern South Island of New Zealand.
DE: 7218 Lithosphere and upper mantle
DE: 8102 Continental contractional orogenic belts
DE: 8150 Plate boundary--general (3040)
DE: 8159 Rheology--crust and lithosphere
DE: 8180 Tomography
SC: Seismology [S]
MN: 2003 Fall Meeting