Gravity Measurements to Bound Instrusive Density at Long Valley Caldera

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9902799Zumberge The Long Valley, California, caldera is the site of a resurgent volcanic dome which is experiencing significant deformation. Gravity is sensitive to both mass and coordinates of the observations; repeated measurements will provide information on changes in those parameters. These observations will bound the rates of subsurface mass change and may also assist in hazard assessment and warning. Gravity at a small number of sites in Long Valley will be observed with an absolute gravimeter. High precision relative gravimeter ties to numerous other sites will expand the spatial coverage. Water table variation effects will be minimized by site selection on impermeable rock where possible, and by analysis of hydrological data collected by the USGS. Models incorporating the gravity with GPS data will be generated; from these, one can infer details of the underlying deformation dynamics. This project is a collaboration with Stanford University researchers Paul Segall and Maurizio Battaglia (who are funded under a grant from DOE).