Ventura, Guido

In this study we analyse two recent low energy (Mdmax = 4.1) seismic sequences (1990-1997) that affected the northern sector (Sannio-Benevento area) of the Southern Apennines chain. We applied the Best Estimate Method to earthquake locations in order to constrain the position and geometry of the seismogenic structures. The most striking features of the obtained fault geometries indicate that earthquakes of the 1990 Benevento sequence align along a NW-SE striking structure, while the earthquakes of the 1997 Sannio sequence outline a NNE-SSW striking structure. The southernmost NW-SE structure dips towards the NE, is characterized by a conjugate fault arrangement and overlies the fault responsible for a larger historical earthquake (Iomax = XI MCS, 1688 earthquake). Available focal mechanisms from earthquakes that occurred on the recognized NW-SE and NE-SW faults are consistent with dip-slip normal solutions. This suggests the occurrence of coexisting NW-SE and NE-SW extension in the Southern Apennines.