Active faulting in the Maiella massif (central Apennines, Italy)

Abstract

The Maiella Massif is the outermost carbonate anticline of the central Apennines, and it is considered as the epicentral area of two major historical earthquakes: the 1706 (Maw = 6.60) and 1933 (Maw = 5.7) events. Geological and geomorphological surveys have defined the geometry and kinematics of the Late Pleistocene-Holocene faults in the Maiella area. These faults show mainly normal kinematics and are organised as a complex dextral en-echelon fault system. The north-eastern fault (the Palena fault) trends N110°-120° and cuts the southern sector of the Maiella Massif transversally, displacing debris deposits that have been radiocarbon dated to 36,300 ±1,300 yr BP. The southwestern fault affects the western slope of Mt. Porrara and is composed of three NNW-SS-oriented en-echelon segments, placing the Mesozoic-Cenozoic carbonate bedrock in contact with Late Pleistocene continental deposits. These normal faults of the Maiella area represent the eastern-most extensional structures of the chain. Geomorphic evidence suggests that the onset of the fault activity probably occurred more recently than along other central Apennine Quaternary faults. This supports the traditional view of an outward (eastward) propagating extensional deformation during the Pliocene-Quaternary. Moreover, the evidence of re-use of pre-existing faults in the cases investigated indicates that this migration of the extensional domain generally occurs through the reactivation of faults inherited from previous tectonic phases, the geometry for which is consistent with the present (N)NE-(S)SW direction of extension. Moreover, the structural framework appears to have been conditioned by the NNE-SSW crustal Ortona-Roccamonfina Line, the present expression of which is seen in a complex dextral oblique fault zone of Late Pliocene age (i.e., the Sangro-Volturno thrust zone). Finally, the integration of our field structural data with the subsurface data available for the on-shore Periadriatic area have allowed the identification of a more external zone (Apulian foreland) that is deformed by lateral and extensional active structures, and an inner zone east of the Maiella Massif that is affected only by the most recent buried thrusts of the chain. This evidence suggests no kinematic interactions at the upper crustal level between the active oblique faulting of the Apulian foreland and the extensional structures of the Apennine chain.