Magnetotelluric monitoring of the Geysers Steam Field, northern California: Phase 2

An original magnetotelluric (MT) survey collected in 2017 included 42 MT stations mainly in the northwestern part of The Geysers geothermal field in northern California. These data were modeled in 3D and imaged the electrically conductive cover, the electrically resistive steam field, and the electrically resistive Geysers plutonic complex (Peacock et al., 2020; Peacock et al. 2020a). Success of the original survey initiated collaboration between the U.S. Geological Survey and Lawrence Berkeley National Labs to monitor the steam field with MT and passive seismic to create a joint 4D model over the course of three years. This project, funded by the California Energy Commission, began in 2020. Two repeated MT surveys were collected at The Geysers, one in April 2021 (Peacock et al., 2022) and the second in April 2022 that extend further south adding 13 stations to the original 2017 survey. Reported here are observations comparing the 2017 data with the 2022 data. Preliminary results indicate the steam field changed in differently across the steam field, similar to changes observed between the 2017 and 2021 data.