Differential GPS Monitoring to Know the Relationship Between the Current Stress Field, the Active Tectonic Structures and the Fluids Circulation in the Geothermal Zones of Acoculco and Los Humeros, Puebla, Mexico

Abstract

As part of one of several studies carried out within the framework of the GEMex project, differential GPS monitoring has been carried out since April 2017. The measurements are carried out in the geothermal zones of Los Humero and Acoculco. These two geothermal zones are considered volcanic craters with active geothermal and tectonic manifestations, and are located in the eastern sector of the Transmexican Volcanic Belt (TMVB). Measurements are taken every 6 months to describe the regional and local stress field. The method used is a measurement procedure called DGPS (Differential GPS) in which two or more GPS receivers are used. In this mode, there is a reference receiver called a base station, which occupies a point and of which the precise coordinates are known which would allow you to calculate the errors with reference to this and one or more mobile receivers called "rovers" that are located on the point or points we want to obtain the coordinates. The great advantage of this method is that the positioning errors, very similar in both points, are eliminated for the most part. The monitoring network consists of 18 control points, strategically distributed along the fault structures that affect the boilers of Acoculco and Los Humeros. Preliminary results show that horizontal displacement vectors have movements between 2 mm and 50 mm, most of these vectors have a preferential NW-SE displacement orientation. The secondary or local NW-SE, NE-SW and E-W structures present in the study area could respond to the regional stress field, which according to the orientation of the vectors seems to have a NW-SE extension and to be controlling the current circulation of groundwater and hydrothermal fluids. Some hydrothermal alterations in Acoculco are found in structures that fit this field of endeavor.