HR: 1330h
AN: T52A-0240    [PDF]
TI: Interplate Coupling and a Recent Aseismic Slow Slip Event in the Guerrero Seismic gap of the Mexican Subduction Zone, as Deduced From GPS Data Inversion Using ABIC
AU: Yoshioka, S
EM: yoshioka@geo.kyushu-u.ac.jp
AF: Dept. of Earth and Planetary Sciences, Kyushu Univ., Hakozaki 6-10-1, Higashi ward, Fukuoka, 812-8581 Japan
AU: * Mikumo, T
EM: mikumo@ollin.igeofcu.unam.mx
AF: Institudo de Geofisica, UNAM, Ciudad Universitaria, Del. Coyoacan, Mexico City, D.F 04510 Mexico
AU: Kostoglodov, V
EM: vladi@servidor.unam.mx
AF: Institudo de Geofisica, UNAM, Ciudad Universitaria, Del. Coyoacan, Mexico City, D.F 04510 Mexico
AU: Larson, K M
EM: kristine.larson@colorado.edu
AF: Dept. of Aerospace Engineering Science, Univ. of Colorado, Campus Box 429, Boulder, CO 80309-0429 United States
AU: Lowry, A R
EM: arlowry@himalaya.colorado.edu
AF: Dept. of Physics, Univ. of Colorado, 4222 Monroe Dr #C, Boulder, CO 80303 United States
AU: Singh, S K
EM: krishna@ollin.igeofcu.unam.mx
AF: Institudo de Geofisica, UNAM, Ciudad Universitaria, Del. Coyoacan, Mexico City, D.F 04510 Mexico
AB: Displacements associated with a large-scale aseismic slow slip event have been detected at seven continuous GPS stations located in the Guerrero region, southern Mexico for several months during late 2001 to early 2002. We re-analyzed the observed GPS time series data to estimate the displacements and the displacement rates during the interseismic period prior to the slow slip event, by applying an inversion technique using a Bayesian information criterion (ABIC). We then carried out inversion of the re-analyzed data again with ABIC to estimate spatial distributions of the drag rates and the slow slip on a 3-D curved plate interface between the subducting Cocos and the overriding North American plates. The inversion results show that the average direction of the drag rates is N31.$3\deg$E$\pm$5.$6\deg$, which almost coincides with that of plate convergence in this region. Interplate coupling is found to be very strong down to a depth of about 45 km, indicating a coupling ratio of 0.83 to 0.86 except for a few segments on the model region, and decreases dramatically down below. The drag rates at middle-depth segments increase southeastward, being consistent with the increase in the rate of plate convergence and in the distance to the volcanic front from the Middle America trench. The slow slip detected at the middle-depth and even on the shallowest segment reached about 10 cm in the landward region of the Guerrero seismic gap. We also estimate stress change due to the slow slip event. From these results, we conclude that the slow slip may have invaded a deeper part of the strongly coupled, seismogenic zone at least up to a depth of 24 km. If such slow slip events occurred episodically, it would be possible to delay the time of occurrence of a future large subduction earthquake in the Guerrero gap.
DE: 1206 Crustal movements--interplate (8155)
DE: 1709 Geodesy
DE: 7209 Earthquake dynamics and mechanics
DE: 7260 Theory and modeling
DE: 8123 Dynamics, seismotectonics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting