A multi-method approach to characterize the geometry of the Paganica and Matese seismogenetic faults (Central-Southern Apennines, Italy)

The Abruzzo and Molise regions (Central-Southern Apennines) are characterized by the occurrence of the strongest seismic activity of Italian Apennines. The seismogenetic sources of Abruzzo and Molise, responsible for destructive historical events (Mw>6) are located along the Apennine chain, along NW–SE faults, with hypocenters focused within the upper 10-20 km of the crust. Structural observations on the Pleistocene faults suggest normal to sinistral movements for the NW–SE faults and normal to dextral movements for the NE–SW structures. The focal mechanisms of the largest events show normal solutions consistent with a NE–SW extension of the chain. The last earthquake that struck the Abruzzo region, occurred on April 6, 2009 (Mw=6.3), killing 309 people. The epicenter was located close to the L’Aquila town, along the Paganica fault belonging to the Paganica-San Demetrio fault system. This earthquake was followed by a long seismic crisis including four events with 5.1< 5.6. After the 1980 Irpinia large earthquake, the release of seismic energy in Southern Apennines was characterized by the occurrence of moderate energy sequences (Mw<5) mainly of shock-aftershocks type and with swarm-type activity, along NW–SE and NE–SW systems of fault. A moderate seismic sequence (Mmax=5.1) struck the Molise region, in the Matese area, from December 29, 2013 (Ferranti et al., 2015). Our study consists of a multiparametric analysis carried out by merging tectonic, seismic and gravimetric data in GIS environment, with the aim of constraining the geometry of Paganica and Matese seismogenetic faults, both at the surface and at depth. The Multiscale Derivative Analysis (MDA) data of the gravity field, whose maxima define the structural lineaments characterized by density contrast, were compared with earthquakes epicentral distribution and faults from literature. Moreover, 2D seismic hypocentral distribution was correlated with the DEXP (Depth from Extreme Points; Fedi and Pilkington, 2012) gravity imaging, to estimate the fault systems parameters (strike, dip direction and dip angle) at depth. This multi-parametric approach was already applied to the seismically active region of the Central Apennines (Luiso et al., 2018), hit by the 2016-2017 Amatrice-Visso-Norcia seismic sequence.