Analysis of Seismic Anisotropy in Los Humeros Geothermal Field, Mexico

Abstract

This study presents the results from the analysis of seismic anisotropy in Los Humeros Geothermal Field, Mexico, correlating the parameters of anisotropy: polarization (è) of the fast shear-wave qs1 and time delay (dt) of the shear-waves qS1 and qS2, with the tectonic and horizontal stress state in Los Humeros Field. By correlating and studying the phenomenon of birefringence or double refraction of shear-waves, we managed to watch matches in the directions of polarization (è) and fracturing present in-situ. The analysis includes two study periods: 1997 to 2002 and 2004 to 2008, in which we identified three areas of seismic anisotropy with the same direction of stress, fracturing and/or faulting: zone with efforts in NE-SW 20⁰ direction, mainly due to regional tectonic stresses, zone E-W (NE-SW 85 °), an area with high structural complexity, mainly produced by the variation of the stress in the E-W direction, however most of the faults are inflicted in these directions, and finally the zone NW-SE 45 ⁰, produced by stress with less tectonic influence, according to the associated fractures and polarization analysis in the stations.