A comparative analysis between transient electromagnetic soundings and resistivity soundings in the Tres Virgenes geothermal zone, Mexico

Abstract

Geothermal zones in volcanic areas are characterized by rough topographic relief and variable shallow resistivities represented by hotsprings, modern and fossil hydrothermally altered zones, and by the presence of different episodes of lavic and explosive volcanism. We examine the performance of in-loop transient electromagnetic (TEM) and vertical electric soundings (VES) in a geothermal area with these characteristics. The inversion of 62 VES and 55 TEM soundings results in similar average stratified models. However, model assessment using the singular value decomposition method show that the TEM soundings possess a higher resolving power. Higher data redundancy, better data quality, less sensitivity to topographic and near-surface inhomogene- ities, and less sensitivity to equivalence problems associated with thin conductive layers are contributing factors to the superior performance of the TEM method.