Seismic attenuation in the Gargano Promontory (Southern Italy).

Since 2013 UniBa and INGV have been collaborating for the operation of the OT seismic network which has significantly improved the seismic monitoring of Southern Italy and Gargano Promontory (GP). The seismic monitoring revealed an intense activity of micro-earthquakes with magnitude less than 2.8 and hypocenters clustered at different depths down to 30 km. Recent 2D and 3D seismic attenuation imaging revealed the trend of coda quality factor $Q_c$ that can be correlated with other geophysical observations in the area. To understand whether $Q_c$ is related to anelasticity or to heterogeneities of the GP crust, the separation of the contribution of intrinsic and scattering quality factors to $Q_c$ is essential. Here we present the quality factors of the $P$ and $S$ waves, $Q_{\alpha}$ and $Q_{\beta}$, obtained from the coda normalization method. $Q_{\alpha} > Q_{\beta}$ can be related to the presence of crustal fluids under conditions of partial saturation for the crustal rock volumes under seismic sampling. The backprojection of $Q_{\alpha}$ and $Q_{\beta}$ along seismic rays allowed to get a 3D image of $\frac{Q_{\alpha}}{Q_{\beta}}$ to be related to fluid percolation and low/high attenuating bodies.