Definition of seismogenic sources in poorly known tectonically active regions of the italian peninsula

Abstract

In the present thesis we have analysed some sectors of the central Apennines and of the Calabrian region in order to improve the knowledge about the seismotectoni characteristics of these portions of the National territory. Geological and geomorphological field surveys permitted to provide an updated evaluation of the slip rate of the active normal fault system that affect the SW slopes of Mt. Morrone (central Apennines). Through an accurate analysis of the geometrical characteristics of this fault system we have also provided an evaluation of the maximum expected magnitude of an earthquake that may originate along this tectonic structure, i.e. M 6.6-6.7. Our investigations led us to identify for the first time evidence of active normal faulting in the area comprised between the southern boundary of Mt. Morrone, the western flank of the Maiella Massif and Mt. Porrara. Here, we have detected a complicate fault system made of 3/4 fault branches, mainly en echelon arranged, along which slope derived deposits dated at the Late PleistoceneHolocene have been displaced by the fault activity. Furthermore, we found evidence of a post-4ka activation event of the fault system resulting in a minimum surface displacement in the order of 15 cm. The field analyses performed in the aftermath of the April 6, 2009 L’Aquila earthquake (Mw 6.3) allowed the identification of coseismic surface ruptures along the Paganica fault, an active extensional tectonic structure located E of L’Aquila. These analyses defined this tectonic structure as the causative fault of the seismic event, fitting GPS and InSAR coseismic observations. Moreover, according to our analysis, the Paganica fault may have activated during the 1461 seismic event (Mw 6.4) and, together with other nearby active fault segments, during the seismic shock of the February 2, 1703 (Mw 6.7). Finally, the investigations carried out in the NE sector of the Calabrian region allowed us to identify evidence of Holocene inverse faulting in the area of Rossano Calabro. According to our observations and through a critical review of the available literature, the observed inverse fault planes may represent the surficial expression of a transpressional tectonic structure that may be a candidate as causative fault of the 1836 earthquake (Mw 6.2).