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 usi ng 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 th e result of subsidence in an area around the Coso geothermal field. The def ormation signal has a short-wavelength component, related to production in the field, and a long-wavelength component, deforming at a constant rate, t hat may represent a source of deformation deeper than the geothermal reserv oir. We have modeled the long-wavelength component of deformation and infer red 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 th e most recent volcanic eruption in the Coso volcanic field [Manley and Baco n, 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.