Steady state deformation of the Coso Range, east central California, inferred from satellite radar interferometry

Observations of deformation from 1992 to1997 in the southern Coso Range using satellite radar interferometry show deformation rates of up to 35 mm yr(-1) in an area similar to 10 km by 15 km. The deformation is most likely the result of subsidence in an area around the Coso geothermal field. The deformation signal has a short-wavelength component, related to production in the field, and a long-wavelength component, deforming at a constant rate, that may represent a source of deformation deeper than the geothermal reservoir. We have modeled the long-wavelength component of deformation and inferred a deformation source at similar to4 km depth. The source depth is near the brittle-ductile transition depth (inferred from seismicity) and similar to1.5 km above the top of the rhyolite magma body that was a source for the most recent volcanic eruption in the Coso volcanic field [Manley and Bacon, 2000]. From this evidence and results of other studies in the Coso Range, we interpret the source to be a leaking deep reservoir of magmatic fluids derived from a crystallizing rhyolite magma body.