Cenozoic deformation phases in the Huimilpan region, Querétaro, and its relation with local seismicity

Abstract

The region of Huimilpan is located in the north-central boundary of the Trans-Mexican Volcanic Belt. Based on the stratigaphy and the documented faults in the study area, four Cenozoic extensional deformation phases are proposed, which mainly occurred during the Neogene. The first deformation phase took place between the Oligocene and the middle Miocene; in this period the Chapala–Tula fault system was active. The second phase is of late Miocene age (Tortonian), corresponding with the Taxco–San Miguel de Allende fault system activity. The third phase occurred in the early Pliocene, with the reactivation of the Chapala–Tula fault system. The fourth phase of deformation, with activity between the late Pliocene and Quaternary, is associated with the Taxco–San Miguel de Allende fault system. Recent seismic record in the region of Huimilpan indicates a microseismicity greater than the average regional level. The documented microseismicity, the scarce historical seismic events and the youngest faults mapped in the study area indicate that it is an active tectonic zone. The fourth deformation phase documented in the study area is closely related with the microseismicity. The activity of the Taxco–San Miguel de Allende fault system shows a migration towards the south-southeast, which in the study area is evident throughout the Lagunillas–Huimilpan fault (second and fourth phases). The youngest activity in the region is documented in the southern segment of the Lagunillas–Huimilpan fault; its age and the seismic data permit to consider this segment as the probable source of the local seismicity.