Integrated MT, Gravity, and Seismic Inversion and Interpretation for Improved Subsurface Imaging

We present a comprehensive geophysical methodology that combines magnetotelluric (MT), gravity and/or seismic data in a joint 3-D inversion framework to reduce interpretational uncertainty and provide a more accurate subsurface image of volcanic and geothermal systems. The methodology leverages the complementary sensitivities of each dataset—electromagnetic data for electrical conductivity, gravity for density contrasts, and seismic for velocity variations—to characterize subsurface structures more robustly than any single method alone.

As a demonstration, we apply this integrated workflow to Newberry Volcano in central Oregon, an important target for geothermal development and Enhanced Geothermal System (EGS) research. Broadband MT and gravity data were inverted jointly and integrated with existing seismic models. The integrated inversion/interpretation confirms a prominent conductive feature beneath the volcano’s southern rim and flank (SRFF), which is also marked by low density and slower seismic velocities. This feature extends from the southern caldera floor near the 1,300-year-old Big Obsidian Flow (BOF) to depths beyond 4 km, yet remains disconnected from the sub-caldera magma body.

Through this Newberry Volcano example, we illustrate how a multi-parameter approach provides improved resolution of the subsurface architecture and fluid flow pathways, highlighting the critical role of joint inversion in unraveling complex volcanic systems. The results not only shed light on Newberry’s hydrothermal alteration and fluid pathways but also underscore the broader applicability of our integrated methodology in guiding geothermal exploration and de-risking subsurface resource assessments.