Elastic and inelastic properties of the Pollino (Italy) seismogenic volume

Abstract

The Pollino area, one of the largest seismic gaps in Italy, was struck between 2010 and 2014 by a long-lasting seismic sequence. More than 10,000 small-to-medium earthquakes occurred as a swarm-like sequence and, to a lesser extent, as  aftershocks following the two largest events: a ML 4.3 on 28 May 2012 and a ML 5.0 on 25 October 2012. A slow slip event began about three months before the strongest earthquake.  Our study focuses on this complex sequence and the recent advancements obtained by our group in terms of crustal structure characterization and fault imaging. We integrate the most recent findings in terms of 3D scattering and absorption imaging, high sensitivity to fluid content, deformed fractured structures, and impermeable layers, with already achieved seismic and focal mechanism tomographic results and available geological information for the area.  High absorption topping the western Pollino seismic volume appears pressurized between the low-Vp/Vs and low-scattering San Donato metamorphic core and a deep basement. This high absorption volume is also characterized, at the same depth, by an excess of fluid pressure, mapped by applying the focal mechanism tomography, where clusters of events of similar waveforms occurred. These events were caused by a slow slip event, similar to the transient deformation event, and favored by pore-pressure increases in fluid-saturated fault networks.  This work was supported by the PRIN-2017 MATISSE project (no. 20177EPPN2), funded by the Ministry of Education and Research.