HR: 17:30h
AN: G14A-07    [Abstracts]
TI: Effects of Material Heterogeneity on Interseismic and Geologic Deformation Southern California Sedimentary Basins
AU: * Marshall, S T
EM: marshall@geo.umass.edu
AF: Geosciences Department, University of Massachusetts, 611 N. Pleasant St., Amherst, MA 01003, United States
AU: Cooke, M L
EM: cooke@geo.umass.edu
AF: Geosciences Department, University of Massachusetts, 611 N. Pleasant St., Amherst, MA 01003, United States
AU: Owen, S E
EM: Susan.E.Owen@jpl.nasa.gov
AF: Department of Earth Science, University of Southern California, 3651 Trousdale Parkway, Los Angeles, CA 90089, United States
AU: Owen, S E
EM: Susan.E.Owen@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109, United States
AB: Conventional methods involving the inversion of geodetic data for fault slip can become cumbersome in structurally complex regions such as the Los Angeles and Ventura basins. To incorporate any number fault intersections at depth along dipping faults, we develop a technique that allows for faults of finite height. We show that the analytical solution for a semi-infinite vertical strike-slip fault is identical to that of a vertical fault of finite height that soles into two horizontal detachments with opposite senses of slip. Based on this analytical solution, we formulate a two-step numerical simulation of the earthquake cycle that allows complex fault surfaces to interact and accumulate slip. In the first step, we solve for the distribution of total geologic fault slip (i.e. entire earthquake cycle) at all crustal levels along multiple, non-planar, three-dimensional faults. Then, to simulate interseismic deformation, slip from the geologic model below the seismogenic locking depth is mapped onto fault surfaces; above the locking depth slip is zero. We apply this technique to the greater Los Angeles and Ventura regions of southern California and find that geologic model results driven by geodetic shortening rates match well geologic slip rate data. Interseismic model results match well the heterogeneous GPS velocity pattern in both regions; however, analysis of model residuals indicates that localized convergence in the San Gabriel and Ventura sedimentary basins is under-predicted by these homogeneous models. To explore the effects of large sedimentary basins in southern California, we create a second set of models that simulate sedimentary basin compliance by populating basin regions with arrays of randomly-oriented micro-cracks. We find that incorporation of the effects of large sedimentary basins into interseismic models of southern California reduces the model-GPS residuals at sites within sedimentary basins. Our results indicate that in southern California, long-term geologic deformation rates are compatible with short-term GPS rates and that models that approach geologic realism best match geodetic data.
UR: http://www.people.umass.edu/stmarsha/la_basin.html
DE: 1209 Tectonic deformation (6924)
DE: 1243 Space geodetic surveys
DE: 1295 Integrations of techniques
DE: 8110 Continental tectonics: general (0905)
DE: 8158 Plate motions: present and recent (3040)
SC: Geodesy [G]
MN: 2007 Fall Meeting