b value enlightens different rheological behaviour in Campi Flegrei caldera

Abstract

Abstract The Campi Flegrei caldera is one of the most dangerous volcanoes in the world and since 2005 it is in unrest. Here we evaluate the 3D tomography of the b value at the Campi Flegrei volcanic area revealing a very good correlation with the structure of the hydrothermal system involved in the bradiseismic phenomenon. More precisely, we observe the smallest b-values where we expect the higher stress/strain concentration, namely in the caprock, and for the deepest seismicity. Conversely, the largest b values are observed where the porosity of the medium allows the passage of the volcanic gases toward the surface. Values of b close to typical tectonic ones are observed where the presence of faulting structures is well documented.