GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 2007). High peak-delay anomalies compared to the mean value at a certain hypocentral distance indicate more fractured areas. The Q c -1 parameter representing the attenuation of the coda wave is theoretically equal to the absorption at late lapse-time (time range between the origin time of the event and the beginning of the coda window, Shapiro et al., 2000) and thus very sensitive to the possible presence of fluids. The 2D analysis, however, limits the interpretation of the main anomalies. By using the new 3D velocity model specific for the study area, a larger number of accurate earthquake locations (Napolitano et al., 2021a) and an updated software (MuRAT3, https://github.com/LucaDeSiena/MuRAT ), we have produced the first 3D separated scattering and absorption model of the Pollino area. We show the preliminary results of our study. The peak delay model highlights a low scattering anomaly at a depth of 2 km, coinciding with the strongest low V P and low V P /V S anomaly obtained in Napolitano et al. (2021a) (Fig. 2). Fig 2. Comparison at 2 km depth between peak delay anomalies at 3 Hz and 6 Hz (upper panels) and V P /V S and V P velocities obtained in Napolitano et al. (2021a). The pink rectangle shows the low V P and low V P /V S well resolved by the tomographic images, which corresponds to a low scattering value, also highlighted by a pink rectangle in the upper two panels. The 3Hz and 6 Hz coda-wave attenuation maps (Fig. 3) show that the highest absorption anomaly is 5-km deep, located in the seismogenic volume of both the M L 5.0 event and hundreds of micro-earthquakes having similar waveforms. The high-absorption anomalies coincide with the excess pore pressure shown in De Matteis et al. (2021) at the same depth with an independent focal mechanism dataset (Figure 3).