HR: 1330h
AN: T22A-0498    [PDF]
TI: Active Extensional Faulting at the Southern Half-Graben Belt of the Tepic-Zacoalco Rift, Western Mexico
AU: * Rosas-Elguera, J
EM: jrosas@ccip.udg.mx
AF: CUCEI, Universidad de Guadalajara, Calzada Olimpica y Blvd. Marcellino Garcˇa Barragan, Guadalajara, Jal 44840
AU: Ferrari, L
EM: luca@servidor.unam.mx
AF: Centro de Geociencias, Juriquilla, Queretaro, Qro 76230
AU: Delgado, M
EM:
AF: Depto. Sismotect˘nica, CFE, Rio Ca¤as, Guadalajara, Jal 44840
AU: Uribe, A
EM:
AF: Depto. Sismotect˘nica, CFE, Rio Ca¤as, Guadalajara, Jal 44840
AU: Valdivia, L
EM:
AF: CUCSH, Universidad de Guadalajara, Av. Alcalde y Av. de los Maestros, Guadalajara, Jal 44100
AU: Castillo, R
EM:
AF: CUCSH, Universidad de Guadalajara, Av. Alcalde y Av. de los Maestros, Guadalajara, Jal 44100
AB: In the past decade much debate has centered upon the kinematics and the mechanism of continental deformation in western Mexico and the motion of the Jalisco block relative to North America. Two distinct models have been proposed. The first one suggest a NW-motion of the Jalisco block that would implies a right-lateral faulting along the Tepic-Zacoalco rift (TZR). More recently others authors have documented a N-NE extensional tectonics active since late Miocene and suggested that the continental boundaries of the Jalisco block, are older structures reactivated by plate boundary forces. Studies on the crustal seismicity and the kinematics of Quaternary faults provide another constraint on the direction of motion between the Jalisco block and North America. On November 4, 5, 6, and 7, 1995, one month after the October 09, 1995, Manzanillo earthquake (Mw = 8.0), a swarm of small events was felt in the Amatlan de Ca¤as half-graben and recorded by the regional seismic network of Comision Federal de Electricidad. The coda magnitude of the largest event was Mc = 2.5-3.6 and the events were located depth ranging from 6 to 10 km. This seismic activity provoked that people from Pie de la Cuesta and Yerbabuena villages were evacuated. After that a seismic station equipped with an analogic seismograph MEQ-800 at Pie de la Cuesta was installed for three months. During the same time, October, 1995, some houses distributed along a WNW trend in Ameca city underwent severe damages, they are. The digital elevations model of the Ameca city suggest that several structures tectonics are shorter than 2 km are present in the area. The present direction of motion of the Rivera plate relative to North America plate along Middle America Trench has been estimated between N19$\deg$E to N48$\deg$E (e.g. Bandy et al., 1996). During the October 09, 1995, subduction-related earthquake (Mw = 8.0) a GPS network recorded a SW motion of the Jalisco block which could be associated to an elastic deformation (Melbourne et al., 1996. Our results suggest that (1) the southern half-grabens are the most active structure of the TZR and (2) They are related to a N-NE extensional tectonics as previously reported. We speculate that the seismic activity recorded at the Amatlan de Ca¤as region is related to a long-term deformation associated with the SW motion of the Jalisco block.
DE: 8107 Continental neotectonics
DE: 8109 Continental tectonics--extensional (0905)
SC: Tectonophysics [T]
MN: 2003 Fall Meeting