Resistivity Structure of Newberry Volcano Region Based on Magnetotellurics Study

Abstract

Newberry Volcano, located in central Oregon, is an active geothermal region with complex subsurface structures influenced by volcanism and tectonics. This study aims to characterize the resistivity structure beneath the southern flank of the vol-cano using standalone Magnetotellurics (MT) data from the NV22 dataset with coverage about 25 km2, downloaded from Geothermal Data Repository (GDR). The analysis began with quality control and dimensionality assessments through MT response curves, polar diagrams, phase tensors, and tipper vectors to deter-mine the dominant geoelectrical strike direction. The data were then rotated and sliced accordingly, and 2D inversion modeling was applied to three profiles using both TE and TM modes. The inversions reveal a layered subsurface structure: very resistive zone 250 – 1000 Ωm near the surface down to 200 – 500 m associated with young volcanic rocks, conductive zone 1 to 30 Ωm interpreted as hydrother-mally altered formations or fluid-saturated layers at the depth of 1 – 2 km, and underlying resistive zone 50 to 100 Ωm corresponding to compact basement rocks or high-temperature regions. These findings provide evidence for a hosted geo-thermal system beneath the southern part of Newberry Volcano. The results also confirm the value of standalone MT methods in resolving detailed geoelectrical structures in volcanic settings, contributing to both geothermal resource assess-ment and geological understanding.