HR: 1340h
AN: U43B-0832    [Abstracts]
TI: Diffuse Intersesimic Deformation Across the North America-Pacific Plate Boundary: Observations and Modeling Results
AU: * Wdowinski, S
EM: shimonw@rsmas.miami.edu
AF: University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149-1098 United States
AU: Smith, B
EM: brsmith@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr. MC 0225, La Jolla, CA 92093 United States
AU: Bock, Y
EM: ybock@igpp.ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr. MC 0225, La Jolla, CA 92093 United States
AU: Sandwell, D
EM: dsandwell@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr. MC 0225, La Jolla, CA 92093 United States
AB: Crustal movements and deformation within the wide diffuse Pacific-North America (Pa-NA) plate boundary are dominated by the right lateral motion between the two plates. Indeed, most of the major fault segments of the San Andreas Fault System (SAFS) and observed velocity vectors are parallel, or sub-parallel, to the direction of relative motion between the plates. Deviation from the Pa-NA relative motion reflects local effects, mainly due to fault geometry and crustal strength heterogeneities. In order to evaluate both the first-order plate motion and second-order local effects, we analyze the SCEC 3.0 interseismic velocity field, consisting of 840 velocity vectors. We transform the velocity vectors into the Pa-NA pole of rotation spherical coordinate system, which decompose the observed crustal movements into parallel and normal components. Analysis of the parallel component shows that equi-velocity contours deviate from the direction of small circles and tend to follow the direction of major faults segment. However the contour spacing varies significantly across the SAFS. Interestingly, the location of the half-plate motion contour follows the trace of San Andreas Fault, except in the southern section, where the contour follows the San Jacinto and the Imperial fault segments. Analysis of the normal component shows a large asymmetric pattern across the big-bend segment, and smaller patterns south of the Parkfield segment and near the intersection of the SAF with the Eastern California Shear Zone. We calculated the expected crustal movements in southern California using elastic and viscoelastic models of locked and creeping fault segments. The models were calculated in the same Pa-NA reference frame, yielding as well the parallel and normal velocity components. A comparison between the observed and calculated velocities shows an overall a good agreement (residuals are in the order of 0-15% of the velocity). The misfit between the model and observations is used to improve the model by accounting for additional unmodeled processes.
DE: 8106 Continental margins: transform
DE: 8118 Dynamics and mechanics of faulting (8004)
DE: 8150 Plate boundary: general (3040)
DE: 8158 Plate motions: present and recent (3040)
SC: Union [U]
MN: Fall Meeting 2005