HR: 1330h
AN: T52C-0285    [PDF]
TI: Finite Element Modeling of Subduction Zone Stresses in the Wake of Bathymetric Feature Subduction Offshore Costa Rica
AU: * Bilek, S L
EM: sbilek@ees.nmt.edu
AF: Earth and Environmental Science Dept., New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AU: Lithgow-Bertelloni, C
EM: crlb@umich.edu
AF: Dept. Geological Sciences, University of Michigan 425 E. University Ave., Ann Arbor, MI 48109 United States
AB: There are several cases of interaction between subducting bathymetric features and large subduction zone earthquakes. For large earthquakes in the Nankai subduction zone, it appears that subducted features have acted as barriers to rupture along the plate boundary. In other regions, such as Costa Rica and Java, subducted seamounts appear to be in regions of high slip during large plate boundary earthquakes. Subducting seamounts and ridges also impact upper plate structure and seismicity. Margin wedge slumps and landslides have been imaged along several margins where seamounts enter the subduction zone. Subducting seamounts also lead to uplifted coastal marine terraces, noted in several upper plate regions. Heterogeneous plate coupling in areas of seamount subduction has been shown to influence seismicity patterns in the upper plate. In order to explore the role of subducting features on the stresses and seismicity along the Costa Rica margin, we have developed a 3D finite element model for this region. In the simplest case, we use the geometry consistent with the Costa Rica subduction zone, but prescribe a smooth subducting Cocos plate to verify that the stresses predicted for the plate interface and upper plate environments are reasonable. To simulate conditions for the 1990 and 1999 large underthrusting earthquakes, we then allow for spatially variable slip along the plate interface, with greater slip at prescribed subducted "asperities" representing the Fisher seamount and Quepos Plateau. We model the effects of this variable slip on stress changes in the upper plate and along the plate interface. Modeled stress changes will then be compared to patterns of local seismicity and focal mechanism solutions.
DE: 7215 Earthquake parameters
DE: 7230 Seismicity and seismotectonics
DE: 8164 Stresses--crust and lithosphere
SC: Tectonophysics [T]
MN: 2003 Fall Meeting