Local earthquake tomography of the Larderello-Travale geothermal field

The Larderello-Travale Geothermal Field in South-West Tuscany (Italy) is the oldest and among the most productive geothermal fields in the world. A new 3D model of seismic P-wave velocity (V-p) of the upper crust beneath the geothermal field is derived by inverting a set of highly consistent travel-times from local-earthquakes. Results document a marked correlation of V-p with previously described, high-reflectivity horizons. We also determined a low velocity body (V-p similar to 5 km s(-1)) culminating at depths of about 7 km, with estimated volume of 35-40 km(3). Such low velocities are consistent with a granite at temperatures above 700 degrees C, thus in a partially-molten status.