Study of seismicity in the region of Guadalajara, Jalisco, Mexico

Abstract

The tectonic regime northeast of Jalisco Block consists mainly of extensive processes that result in rift zones, such as Tepic-Zacualco Rift and Chapala Rift. Also, there are several fault systems, many of them still unknown, which are responsible of the earthquake occurrences in this region. Studies of seismic hazard are particularly interesting, due to the existence of important urban areas in this seismogenic region, such as Guadalajara Metropolitan Zone (GMZ). Historical data report the occurrence of several significant events (M>7) in the Jalisco Block region. Particularly, during December 2015 and May 2016, earthquake swarms were registered with epicenters in the WNW of the GMZ, and from the analysis of these seismic activities, recent studies have observed evidences of active faults in this area, which constitute a rift zone not previously identified.

In this study, we analyzed seismic events that were registered by a temporal network of 25 seismic stations of short period, which were installed in La Primavera area and its surroundings, in the west of GMZ, from September 2017 to April 2018, in the framework of CeMIEGeo project P24 “Passive seismic and magnetotelluric exploration of the volcanic fields of The Ceboruco and La Primavera Caldera”.

Results obtained from the data analysis of the first four months (September-December 2017), suggest that the most seismicity is located in the Zapopan area and part of the Tesistán Valley, and in the La Primavera Caldera, in the WNW of GMZ. Almost 200 events were located in this area, the most of them at less than 40 km of depth, with magnitude up to ML=3.8. The spacial and temporal analyses, and the focal mechanism estimations, were used to improve the identification and characterization of fault systems in the area, and these observations are useful background information for seismic hazard studies. Only two of the earthquakes analyzed appears in the regional catalogs, so that it is very important the seismic monitoring with a local network that allows future studies in this region.