HR: 1340h
AN: T13C-1385    [Abstracts]
TI: Investigating Lateral Variations of Interseismic Strain along the Sumatran Subduction Zone
AU: * Chlieh, M
EM: chlieh@gps.caltech.edu
AF: California Institute of Technology, Tectonic Observatory, 1200E. California Blvd, Mail Code 100-23, Pasadena, CA 91125 United States
AU: Avouac, J
EM: avouac@gps.caltech.edu
AF: California Institute of Technology, Tectonic Observatory, 1200E. California Blvd, Mail Code 100-23, Pasadena, CA 91125 United States
AU: Sieh, K
EM: sieh@gps.caltech.edu
AF: California Institute of Technology, Tectonic Observatory, 1200E. California Blvd, Mail Code 100-23, Pasadena, CA 91125 United States
AU: Natawidjaja, D H
EM: danny@gps.caltech.edu
AF: California Institute of Technology, Tectonic Observatory, 1200E. California Blvd, Mail Code 100-23, Pasadena, CA 91125 United States
AU: Galetzka, J
EM: galetzka@gps.caltech.edu
AF: California Institute of Technology, Tectonic Observatory, 1200E. California Blvd, Mail Code 100-23, Pasadena, CA 91125 United States
AB: Paleoseismic, paleogeodetic and GPS data from the Sumatran subduction zone provide an unusual opportunity to understand the physical parameters that control the behavior of a subduction interface. Interseismic strains recorded over the last several decades by coral growth rings and GPS instruments allow us to model subduction zone behavior using a three-dimensional dislocation back-slip model. The kinematic model takes into account the partitioning of slip between the subducting Australian plate and Sunda into dominantly dip-slip motion along the subduction interface and strike-slip faulting along the Great Sumatran fault (GFZ). The sliver between the trench and the GFZ is assumed to behave, in the long term, as a rigid microplate. Given the northward secular motion of the Sumatra forearc, the normal convergence across the subduction zone is 40-46 mm/yr. Our modeling shows that the GPS and coral data are well fit by a simple model that assumes full locking of the subduction interface with lateral variations in the depth of the downdip end of the locked interface. The width of the locked interface is at a minimum value of ~135 km near the Equator and increases to about ~190 km farther south (This corresponds to a variation in depth from ~35 to 50 km). We note that over the past 250 years the subduction interface near the Equator has produced smaller earthquakes ( Mw = 7.7 in 1935 and 7.2 in 1984) than the area farther south, which has produced giant earthquakes in 1797 and 1833 (Mw = 8.4 to 8.7+). This difference in both the seismic behavior and width of the locked fault zone may be related to the structural irregularities associated with subduction of the Investigator Fracture Zone or to lateral variations in the age of the subducting plate and/or the rate of convergence. We investigate these possibilities by modeling the effect of thermal structure on the behavior of the subduction zone.
DE: 7221 Paleoseismology
DE: 7260 Theory and modeling
DE: 8150 Plate boundary--general (3040)
DE: 1204 Control surveys
DE: 1206 Crustal movements--interplate (8155)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting