HR: 1400h
AN: S43A-05    [Abstracts]
TI: Stress regime from active earthquake faulting in the Basin of Mexico
AU: * Ortega, R
EM: ortega@cicese.mx
AF: Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Miraflores 334. Fracc. Bellavista, La Paz, BCS 23050, Mexico
AU: Quintanar, L
EM: luisq@ollin.igeofcu.unam.mx
AF: Instituo de Geofisica UNAM, Ciudad Universitaria., Mexico City, DF 04510, Mexico
AU: Garcia Palomo, A
EM: apalomo@geol-sun.igeolcu.unam.mx
AF: Instituto de Geologia, Ciudad Universitaria, Mexico CIty, DF 04510, Mexico
AB: The Trans-Mexican Volcanic Belt is characterized by E-W fault systems forming structural features such as graben and semi-grabens. Some of these structures are associated with seismic events, indicating active faulting. In this study earthquake fault parameters have been determined using broad-band (BB) data and first motion polarities in the Basin of Mexico. Simultaneous inversion of P-wave polarities and near-field BB waveform modeling using a grid-search approximation was performed and source parameters of 29 low-to-moderate-size earthquakes located within the Basin of Mexico were estimated. The stress field in the Basin of Mexico is basically defined by the principal stress sigma-3 oriented N346° and the principal stress sigma-1 oriented N140° plunging at 38° and 49° respectively. The stress field along the Central TMVB is continuous with small gradual rotations in the sigma-1. Our results from focal mechanisms associate with E-W fault system confirm that the Basin of Mexico is a transtensional stress regime probably related to slip partition from the Mid American Trench.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8010 Fractures and faults
DE: 8038 Regional crustal structure
DE: 8109 Continental tectonics: extensional (0905)
SC: Seismology [S]
MN: 2007 Joint Assembly