A comparison of tectonic deformation styles with Gutenberg-Richter b-values in the Italian and Mediterranean areas

Some recent analyses, using available CMT catalogs, evidenced the existence of a relation between the Gutenberg-Richter b-value and the tectonic style of seismic release, both at a global (Harvard CMT) and a regional scale (California and Japan). In particular extensional mechanisms would correspond to higher b-values than compressive ones. In this work we attempted to verify such findings for the Italian and Mediterranean areas using a slightly different procedure. We performed our analysis subdividing the areas according to different criteria (regular grids of various shape and size, available seismotectonic zonations, etc.) and assuming different seismogenic thicknesses. In each subdivision, we compare the tectonic style inferred from the moment tensor sum of all available mechanisms with the b-value computed from hypocentral catalogs. To characterize the style of seismic release we take advantage of some regional MT catalogs (INGV and ETH) and of an upgraded implementation of EMMA database, including more than 8000 focal solutions taken from the literature, in addition to Harvard CMT. To compute the b-value for the Mediterranean region we use the ISC catalog with the moment magnitude consistently recomputed from available magnitude estimates. For Italy we use instead a combination of CSTI and CSI catalog which both report compatible estimates of local magnitude.