Geoelectrical characterization of non-filled active faults in Jaral de Berrios, Guanajuato, México

Abstract

Electromagnetic and electrical methods have a great number of applications and have become a commonly used tool for the study of active geological faults, where they are usually detected as low resistivity anomalies. However, this is not always the case. We used both Electromagnetic Profiling (EMP) and Electrical Resistivity Tomography (ERT) methods with the aim of mapping active geological faults which affect agricultural plots and a former quarry near the town of Jaral de Berrios, State of Guanajuato. The apparent resistivity map derived from EMP survey shows how NW-SE on site measured faults (which reach at least 400 m in length and 0.4 m in width) match with high apparent resistivity anomalies. Two ERT profiles reveal the subsurface continuity of the main fault zones, as well as the main high apparent resistivity lineaments, for at least 40 m below the surface. The resistive lineaments in the apparent resistivity map showed a coincidence with the faults modeled in the geoelectric section of the ERT1 profile; this result gives reliability to the methodology used in the study site. All of this means that faulting presently evident on the surface continues at depth and has a wider extension than previously thought, and that since the fractures are non-filled with minerals and/or moisture the preponderance of high resistivity anomalies make sense. The results of this work provide the basis for future studies that help in determining the type of faulting affecting our study area, so long term urban planning and development in the area may be possible.