Seismicity in northeast edge of the Mexican Volcanic Belt (MVB), activation of an undocumented fault: the Peñamiller earthquake sequence of 2011, Queretaro, Mexico

Abstract

Abstract. The Peñamiller town, in the Queretaro state, Mexico is located at the northeast border of the seismogenic zone known as the Mexican Volcanic Belt (MVB), which covers a central fringe of Mexico with east-west orientation. In this town, a sequence of small earthquakes occurred during the end of 2010 and beginning of 2011. Seismicity frequent in of the continental regimen of central Mexico are not common, however, it is known that there are precedents of large earthquakes (Mw magnitude greater than 6.0) occurring in this zone. In order to enrich seismic information, which has not been analyzed nor documented until this moment, is presented this work. This will contribute to gain more insight into the tectonic situation of the central Mexico region. Twenty-four shallow earthquakes records of the Peñamiller, Queretaro seismic sequence of 2011 were recorded by a provisional accelerograph network from the Universidad Autonoma de Queretaro (UAQ). The data were analysed in order to determine the source locations and for the estimation of the source parameters. The study was carried out through an inversion process and by spectral analysis. The results show that the largest earthquake, occurred on 8 February 2011 at 19:53:48.6 UTC, had a moment magnitude Mw = 3.5, and was located at latitude 21.039° and longitude −99.752°, at a depth of 5.6 km. This zone is located less than 7 km away in south-east direction from downtown Peñamiller. The focal mechanisms are mostly normal faults with a small lateral component. This feature is consistent with the extensional regimen of the southern extension of the Basin and Range (BR) province. The source area of the largest event was estimated to have a radius of 0.5 km, which corresponds to a normal fault with azimuth of 174° and an almost pure dip slip; this caused Peak Ground Acceleration (PGA) of up to 100 cm s−2 in the horizontal direction. It is evident that the shallow earthquakes induced by crustal faulting can present a potential seismic risk and hazard within the MVB and considering the population growth, the necessity to enrich seismic information in this zone is very important; which at most urban sites in the region might even be greater than the risk posed by subduction earthquakes.

Evidence for quaternary seismic activity of the La Alberca-Teremendo fault, Morelia region, Trans-Mexican Volcanic Belt

“…SRL = Surface rupture length. Data marked with (*) were obtained from Clemente-Chávez et al (2013) and Singh et al (2011Singh et al ( , 2012.…”