2D MAGNETOTELLURICS INVERSION AND IMPEDANCE PARAMETER ANALYSIS FOR GEOTHERMAL SYSTEM CHARACTERIZATION IN THE SAN EMIDIO AREA, NEVADA.

Abstract

Geothermal energy is a sustainable and reliable energy source, often associated with tectoni-cally active regions where geological structures, particularly faults, enhance subsurface per-meability. The San Emidio geothermal field, located within the Basin and Range province of Nevada, represents a structurally controlled geothermal system characterized by normal faulting. This study aims to delineate key conductive and resistive zones while interpreting their spatial association with known fault structures for identifying regions with geothermal potential. Data for this study were obtained from Geothermal Data Resources, total of 47 MT stations were evaluated through quality control to ensure the use of only high-quality data. Phase tensor and polar diagram interpretations were conducted to determine the dominant geoelectrical strike direction, which was consistently found to be approximately N5°E. The data were then oriented accordingly, and 2D inversions were also conducted on five survey lines oriented perpendicular to the strike direction. The inversions results revealed a shallow conductive layer with resistivity values ranging from 1 - 10 ohm.m, interpreted as a clay cap formed by hydrothermal alteration down to around 0.5 km. Beneath this layer lies a zone of moderate to high resistivity 16 - 44 ohm.m (down to 1.5 km), interpreted as a geothermal res-ervoir. This reservoir is directly associated with production wells reporting temperatures up to 162°C. Beyond these resistivity regions, resistivity value of 30 – 1000 ohm.m is observed, interpreted as the background of geothermal system. The conceptual model also indicates the existence of fluid upflow zones migrating through fault structures from the southwest toward the reservoir, with a highly resistive basaltic unit acting as a lateral seal