Induced Seismicity and Deformation at Geothermal Fields in California, USA

Abstract

Understanding natural and anthropogenic sources of strain accumulation and release is critical to the accuracy of hazard assessments at geothermal fields. While the genesis of naturally occurring seismic and geologic hazard potential lies in the balance between gravitational forces, tectonic loading and natural faulting, induced earthquakes and ground deformation are generally understood to be related to reservoir depletion. With the current state-of-the-art in geodesy and seismology, these phenomena can be measured with unprecedented spatial and temporal coverage, illuminating the inherent feedback between production and reinjection, dominant modes of moment release, permeability, and structural complexity. Here I draw comparisons between large, active geothermal fields in California (USA), namely Coso, Salton Sea, North Brawley, and Heber. Seismic and geodetic data collected at the fields, spanning decades, show that steady and time-varying geologic hazards (i.e., earthquakes and ground deformation) are common observations.