Seismic activity and stress tensor inversion at Las Tres Virgenes Volcanic and Geothermal Field (Mexico)

摘要

We analyze local earthquakes occurring between 2003 and 2012 at the Las Tres Virgenes Volcanic and Geothermal Field (TVVGF) to establish their temporal and spatial distribution, and relationships with local and regional fault systems, water injection, acid stimulation and steam production tests. We obtained focal mechanisms and inverted data for the stress tensor to understand the local and regional stress fields. We analyzed 423 local earthquakes with magnitudes between 0.1 and 2.9 Mc and hypocentral depths from 0.2 to 7.4 km b.s.l. The cutoff depth at similar to 7.4 km possibly delineates the brittle-ductile transition zone. We identified seven swarms (from 1 to 7). Swarms 1 (December 2009), 2 (May 2010), 3 (June-July 2010) and 7 (December 2012) are strongly correlated with injection processes; whereas swarms 5 (April 2012) and 6 (September 2012) are correlated with local tectonic faults. Stress inversion showed NW-SE, E-W and NE-SW extensional orientations (S-hmin), in agreement with the local tectonic stress field; while NE-SW compressional orientations (S-Hmax) are correlated with the regional tectonic stress field. (C) 2015 Published by Elsevier B.V.