GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 1.1 GNGTS 2023 focal mechanism tomography for the area and confirmed by preliminary results of absorption maps (Fig. 3). Furthermore, De Matteis et al. (2021) show that the distribution of seismicity was driven by pore fluid pressure diffusion with a relatively low diffusivity value. The latter mechanism could also explain the delayed triggering of the two largest events M L 4.3 and M L 5.0, respectively, which occurred about 150 days apart. Conclusions The elastic and anelastic crustal properties of the seismogenic volume involved in the 2010-2014 seismic sequence that occurred in the Pollino area were investigated by means of different techniques: seismic tomography of P- and S-wave travel times, 3D total attenuation tomography, 2D and 3D scattering and absorption imaging, and tomography of focal mechanisms. In addition, kinematic parameters were also analyzed, such as re-location of the strongest events (ML> 1.7), the location of micro-earthquakes with the master-slave technique and focal mechanisms. The analyses allowed us to obtain increasingly detailed information on seismogenic sources, the properties of the wave propagation medium, and the role of fluids in the evolution of the seismic sequence. In particular, it was possible to highlight the overlap between the Apulian and Apennine platforms, with the latter dipping below the former in the area of the western cluster of the 2010-2014 sequence. It is precisely at the interface between the two tectonic structures that most of the seismicity takes place, with stronger earthquakes and clusters of micro-earthquakes of similar waveforms drawing a structure with an intermediate angle dip towards the SW. The strong influence of fluids is evidenced by high V P /V S values, high attenuation and values showing overpressure of pore fluids. This would explain both the presence of clusters of events with similar waveforms, a peculiarity of areas with a strong predominance of fluids, such as volcanic areas, and the delayed triggering of the M L 4.3 and M L 5.0 events. Acknowledgements. This work was supported by the PRIN-2017 MATISSE project (no. 20177EPPN2), funded by the Ministry of Education and Research. References Amoroso, O., Ascione, A., Mazzoli, S., Virieux, J., & Zollo, A.; 2014: Seismic imaging of a fluid storage in the actively extending Apennine mountain belt, southern Italy. Geophys. Res. Lett., 41(11), 3802-3809. Brozzetti, F., Cirillo, D., de Nardis, R., Cardinali, M., Lavecchia, G., Orecchio, B., ... & Totaro, C.; 2017: Newly identified active faults in the Pollino seismic gap, southern Italy, and their seismotectonic significance. J. Struct. Geol., 94, 13-31.