HR: 0800h
AN: T51D-1389    [Abstracts]
TI: Seismic Hazard Estimates of the Los Angeles and Ventura Basins Using Three-Dimensional Mechanical Models of Active Faulting
AU: * Cooke, M L
EM: cooke@geo.umass.edu
AF: University of Massachusetts, Department Geosciences 611 North Pleasant St, Amherst, MA 01003-9297 United States
AU: Marshall, S T
EM: marshall@geo.umass.edu
AF: University of Massachusetts, Department Geosciences 611 North Pleasant St, Amherst, MA 01003-9297 United States
AB: The Los Angeles and Ventura basins of Southern California both contain arrays of complex three-dimensional active faults. To best estimate the seismic hazards of these regions, we examine the interaction of faults within these complex systems using three-dimensional Boundary Element Method (BEM) models, which are adept at simulating the deformation of complex three-dimensional active fault surfaces. Three-dimensional fault surfaces used in our models are based on the Community Fault Model of the Southern California Earthquake Center but have been modified to extend to a depth of 27.5 km, which represents the approximate location for the Mohorovic Discontinuity. Within our BEM models, faults freely slip in response to prescribed tectonic boundary conditions that are determined from geodetic studies. To calculate the seismic hazards on these faults, we determine recurrence rates for and seismic energy released by hypothetical earthquake events within our models. From models with locked fault surfaces, we calculate the stressing rates on each fault segment. From these stressing rates, we calculate a range of recurrence intervals between events by assuming that earthquake stress drops range from 1-3 MPa. The seismic energy released and magnitude (Mw) of the model-predicted rupture events is calculated from the slip rates, recurrence interval and fault surface area. This analysis can be performed for individual fault segments and for various scenarios of rupture across segments. Our models predict moderate to large earthquakes in the Los Angeles and Ventura basins (M 5.5-7.6) with recurrence intervals of ~1000-3000 years and can be useful for seismic risk assessments on poorly constrained and/or blind thrusts.
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 8004 Dynamics and mechanics of faulting (8118)
DE: 8010 Fractures and faults
DE: 8020 Mechanics, theory, and modeling
SC: Tectonophysics [T]
MN: Fall Meeting 2005