HR: 0830h
AN: S41C-0106    [PDF]
TI: Seismicity Surveying in Central and North Mexico Regions
AU: Nieto-Samaniego, A
EM: afns@geociencias.unam.mx
AF: Centro de Geociencias, Campus Juriquilla-UNAM Blvd. Villas del Meson s/n Provincia Juriquilla, Queretaro, Qro 76230 Mexico
AU: * Gomez-Gonzalez, J M
EM: gomez@geociencias.unam.mx
AF: Centro de Geociencias, Campus Juriquilla-UNAM Blvd. Villas del Meson s/n Provincia Juriquilla, Queretaro, Qro 76230 Mexico
AU: Guzman-Speziale, M
EM: marco@geociencias.unam.mx
AF: Centro de Geociencias, Campus Juriquilla-UNAM Blvd. Villas del Meson s/n Provincia Juriquilla, Queretaro, Qro 76230 Mexico
AU: Zuniga, R
EM: ramon@geociencias.unam.mx
AF: Centro de Geociencias, Campus Juriquilla-UNAM Blvd. Villas del Meson s/n Provincia Juriquilla, Queretaro, Qro 76230 Mexico
AU: Alaniz-Alvarez, S
EM: alaniz@geociencias.unam.mx
AF: Centro de Geociencias, Campus Juriquilla-UNAM Blvd. Villas del Meson s/n Provincia Juriquilla, Queretaro, Qro 76230 Mexico
AU: Barboza, R
EM: rbarboza@uaslp.mx
AF: Instituto de Geologia, UASLP, Av. Dr. Manuel Nava No. 5, San Luis Potosi, SLP 78240 Mexico
AU: Davalos, O
EM: odavalos@geociencias.unam.mx
AF: Centro de Geociencias, Campus Juriquilla-UNAM Blvd. Villas del Meson s/n Provincia Juriquilla, Queretaro, Qro 76230 Mexico
AB: The seismic nature of Central Mexico is poorly understood due to insufficient sampling. We carried out a seismic survey in part of the TransMexican Volcanic Belt (TMVB) and the Central Altiplano. These regions are characterized by a very low deformation rates. Seismic activity is variable and ranges from microseismicity to large earthquakes, but no large historic earthquake has been instrumentally recorded. Only few direct observations such as intensity reconstructions and recent paleoseismic studies (e.g. the Acambay-Tixmadej‚ earthquake of 1912) are available. Large earthquakes have occurred but their recurrence period is unknown; structural studies show this recurrence could range from hundreds to thousands of years. In order to understand the regional seismic behavior, we installed a temporal network. This network consists of 3-5 short period instruments, consisting of 16-bits triaxial digital velocity recorders (0.01-4.5 Hz). We registered several seismic sequences over a period of several months. One of them took place in Guanajuato within a graben structure in the TMVB and lasted for 2 weeks. Another sequence occurred at the northern limit of the TMVB in the Sierra Gorda. Over five weeks, several micro-earthquakes M $<$ 2 were felt with anomaously high intensity. Relocated seismicity shows very shallow ($<$ 10km) activity. Even though the seismicity varied significantly, the regional crustal conditions appear to be roughly uniform. In some areas like Arroyo Seco, in the Sierra Gorda, the event distribution is aligned along a small valley, but perpendicular to the main structural grain imposed by the Sierra Madre Oriental range. In no instances have surface ruptures been observed; those seismogenic structures could be blind ones. A challenge is to locate this structures which are may be too old to be still active. Increased seismotectonic knowledge of this region will yield further insight into the details of the interaction between surface structures driven by the regional stress field. Our results provide evidence that the region requires more intensive seismic surveying, and in some cases that some structures have been reactivated recently.
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
DE: 8010 Fractures and faults
DE: 8020 Mechanics
DE: 8107 Continental neotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting