HR: 16:00h
AN: G14A-01    [Abstracts]
TI: Evidence for the Existence of the Bering Plate
AU: Cross, R S
EM: fsrsc@uaf.edu
AF: Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775, United States
AU: * Freymueller, J T
EM: jeff.freymueller@gi.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775, United States
AB: GPS measurements are used to examine the hypothesis of a clockwise rotating Bering plate. Originally proposed based on seismicity, the Bering plate encompasses the Bering Sea, western Alaska, and the Aleutian Islands. GPS measurements from the Bering plate's interior show south to southwest motions of 3 to 5 mm/yr. We construct elastic dislocation models to determine the spatial distribution and intensity of locked patches on the Aleutian subduction interface, and use these to remove interseismic strain from the GPS observation and determine an arc translation velocity for each region of the Aleutians. Translation velocity estimates range from 4 to 8 mm/yr mm/yr oriented south to southwest. We combine the arc translation rates with measurements from Bering plate's interior sites and estimate the angular velocity for the Bering plate relative to North America to have an angular speed of 6.0°/my about a pole located at 42.5° N, 121.3° E. The clockwise rotation of the Bering plate causes the Bering Sea crust to override the Aleutian trench, and may drive left lateral faulting in interior Alaska. The Bering plate's interaction with southcentral Alaska may be responsible for the decreased slip-rate on the western Denali fault, and for contraction across the central Alaska Range. We analyze slip partitioning along the Aleutian arc based on both GPS measurements and slip azimuths of thrust earthquakes. We find a systematic discrepancy between plate convergence direction and slip azimuths and find that slip partitioning in the back-arc only develops west of Amchitka Pass, whereas slip partitioning in the forearc is present throughout the arc.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 8158 Plate motions: present and recent (3040)
SC: Geodesy [G]
MN: 2007 Fall Meeting