Analysis of Shear Wave Splitting Parameters in Los Humeros Geothermal Field, Puebla, Mexico

Session: Crustal Stress and Strain and Implications for Fault Interaction and Slip [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

A study of anisotropic characteristics based on shear wave splitting parameters (fast shear wave polarization and delay time) was carried out from microearthquakes recorded by seismic arrays installed in Los Humeros Volcanic Complex, Puebla, Mexico from 2011 to 2016. This analysis determined the effects on seismic activity caused by fluid injection, as well as possible variations of the tectonic stress regime. The fast shear wave polarizations remained mostly constant for the analyzed period, with a preferential direction of NW – SE, which closely follows the orientation of the most faults in the area. In some cases, it is possible to see secondary polarizations WNW - ESE and ENE – WSW related to minor local faults and by changes in the tectonic ambient and effects generated by variations in pore pressure. The annual tendency shows a significant change from July 2014 to June 2016, based on a t-test that indicates that possible changes in the stress level are due to an increase in fluid injection.

Observations of time delays show a range between 0.025 s to 0.07 s for all seismic stations, with some individual values reaching 0.15 s. Nonetheless, graphs of the annual averages from 2014 to 2016, indicate a change in the stress level (decrement), similar to our results of fast shear-wave polarizations, also confirmed by a t-test. The delays results have allowed characterizing the main routes of permeability in the geothermal field, indicating the Los Humeros, Antigua and Malpaís faults as the main permeability routes.

Presenting Author: Francisco Chacon

Authors