Active tectonics and paleoseismicity of a transverse lineament in the Fabriano valley, Umbria-Marche Apennine (central Italy)

Structural elements, transversal to the Apennine chain, display various problematic aspects connected, above all, with their origin tectonogenetic role. From a seismic point of view, they may act as a structural barrier to the propagation of the Apennine normal faults or behave as transfer zones, thus activating neighboring segments belonging to the same fault system; the largest ones can also host significant earthquakes with the hypocenters located in the basement, below the Apennine thrust belt. This paper describes a case of recurrent surface faulting that reactivates a sector of a relevant transverse feature, the "." (FV-VE), near the city of Fabriano (Marche, Italy). Detailed geomorphological observations connect it with past earthquakes, including the disastrous event (I0 = IX MCS, about 6.2 Mw) of 24 April 1741 that struck the area with a wide distribution of damages extending along the Esino River Valley to the Adriatic coast over a distance of more than 50 km. Furthermore, paleoseismological analysis and radiocarbon datings of faulted river terraces and slope deposits, ranging in age from the end of the Middle Pleistocene to the recent Holocene, allowed us to define the evolutionary steps of the fault and estimate a slip rate of about 0.3 mm/year.