Local seismicity in the Ceboruco Volcano Region, Mexico

Abstract

The Ceboruco volcano is located in the northwestern part of the Tepic-Zacoalco graben, close to the boundary between the Sierra Madre Occidental and the Trans Mexican Volcanic Belt, Mexico. This volcano had effusive-explosive episodes with eight eruptions during the last 1000 years, providing an average of one eruption each 125 years. The last eruption occurred in 1870, 148 years ago, so the likelihood of a new eruption is extremely high and risky due to nearby population centers, important roads and lifelines that traverse the volcano’s slopes. This hazard indicates the importance of studying and monitoring the seismicity associated with this volcano whose ongoing activity is evidenced by fumaroles and earthquakes. As part of CeMIEgeo project, a dense temporal seismic network of 25 stations with 3D sensors was deployed covering an area of 256 km2, with one station every 2.5-3 km. The objective of this project is to carry out a local seismic study to define the volcanic edifice structure. In this work, we present the analysis of the volcano-seismicity data generated by this seismic network in the period between November 2016 and July 2017. This analysis consisted of integrating in a database using Antelope software, where we obtained the P and S arrival times and preliminary locations using IASP91 velocity model. After that, the events were relocated with HYPO71 using an appropriated velocity model and focal mechanisms were calculated. We observed the seismicity is concentrated below the crater and relatively shallow with hypocenter depths between 4 and 8 km. In addition, we were able to identify seismic trace families and some alignments.