HR: 09:25h
AN: T31A-06    [Abstracts]
TI: Kinematic Coupling Along the Mexican Subduction Zone From GPS Data
AU: * Franco, S
EM: ivonne@ollin.igeofcu.unam.mx
AF: Servicio Sismologico Nacional, Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Av Universidad, 3000, Copilco, Coyoacan, Mexico, DF 04510, Mexico
AU: Kostoglodov, V
EM: vladi@servidor.unam.mx
AF: Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Av Universidad, 3000, Copilco, Coyoacan, Mexico, DF 04510, Mexico
AU: Iglesias, A
EM: amg@ollin.igeofcu.unam.mx
AF: Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Av Universidad, 3000, Copilco, Coyoacan, Mexico, DF 04510, Mexico
AU: Singh, S
EM: krishna@ollin.igeofcu.unam.mx
AF: Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Av Universidad, 3000, Copilco, Coyoacan, Mexico, DF 04510, Mexico
AB: Kinematic coupling (α) between the subducting Cocos and Rivera oceanic plates, and the continental North America plate is estimated as a ratio between the back slip on the fault plane and the convergence rate (NUVEL1A model). To obtain a distribution of the back slip ("negative" displacement at the plate interface) along the coast of Jalisco, Guerrero, Oaxaca and Chiapas we performed an inversion of the surface crustal deformation data from the permanent GPS network "SSN-Sismologia-UNAM" and campaign GPS measurements. The displacements for each cell of the plate interface model were calculated using closed form expressions developed by Okada (1992). The inversion based on a simulated annealing algorithm reveals a high coupling ratio, α ~ 1, at the seismogenic zone of 40-50 km width in Guerrero and Oaxaca, just beneath the coast line. Downdip from this area, a transition or partially coupled zone, α ~ 0.28, extends for a distance of about 200 km. For the Isthmus of Tehuantepec zone, at the southeastern Oaxaca, the inversion model shows a very low coupling ratio. In Chiapas, at the southern Mexico Pacific coast, the sparse distribution of GPS stations does not allow us to constrain a satisfactory model. Nevertheless, some preliminary results show a coupled area close to the trench. At the northwest, along the coast of Jalisco, the observed surface crustal deformation is mostly a result of subduction of the Rivera Plate beneath the North America Plate. For this area, the campaign GPS data were obtained from the UNAVCO database. Preliminary results show a highly coupled seismogenic zone. Strongly coupled areas that were determined from the inversion models are in good agreement with the seismogenic zones defined with the rupture areas of large Mexican subduction thrust earthquakes (M > 6.5) occurred last century.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 7240 Subduction zones (1207, 1219, 1240)
SC: Tectonophysics [T]
MN: 2007 Joint Assembly