Local seismicity analysis in La Primavera Caldera, Jalisco, Mexico.

Abstract

The caldera of La Primavera is located west of Guadalajara, Mexico, at the NE limit of the seismically and volcanically active tectonic region known as the Jalisco Block. Notable crustal earthquakes have occurred in this region, such as the 1568 M=7.2 and 1875 M=7.5 events. In addition, recent earthquake sequences in December 2015 and May 2016, with events up to ML=4.8, occurred in the NW outskirts of Guadalajara, in the Tesistan Valley, with the largest being broadly felt (MMI=V-VI) in most parts of the Guadalajara Metropolitan Area. As part of the P24 CeMIEGeo project, "Passive seismic and magnetotelluric exploration of the Ceboruco and La Primavera volcanic fields", a local seismic station network, consisting of 25 Kinemetrics Obsidian multi-channel recorders and Lennartz-3D short period seismometers, was arranged in a 5 x 5 rectangular grid for a period of 8 months (September 2017-April 2018). Preliminarily, 262 events were located with the Antelope software using data from the September 2017-December 2017 period; 49 of these events occurred within the proposed caldera's limits, and the remaining events were located in nearby structures, mostly to the NE of La Primavera, in the Tesistan valley. The largest of the analyzed events was a ML=3.8 earthquake, on September 3rd, 2017. Furthermore, we used the software HYPO71 to better estimate event locations with higher reliability, using a local crustal velocity model, leading to 235 newly located events. In addition, we obtained focal mechanisms and performed spectral analysis in order to determine the nature of the seismic activity, with the goal of contributing to the ongoing efforts and studies to evaluate potential geothermal energy regions.