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Paper reference: C. Wicks, W. Thatcher, F. Monastero and M. Hasting, 2000 submitted, Steady-State Deformation of the Coso Range, East-Central California, Inferred from Satellite Radar Interferometry, Journal of Geophysical Research

Observations of deformation from 1992-1997 in the southern Coso Range using satellite radar interferometry show deformation rates of up to 35 mm/yr in an area ~10 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 ~4 km depth. The source depth is near the brittle-ductile transition depth (inferred from seismicity) and ~1.5 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 crystalizing rhyolite magma body.