The Volcano-Tectonics of the Northern Sector of Ischia Island Caldera (Southern Italy): Resurgence, Subsidence and Earthquakes

The island of Ischia, an active volcanic field emerging in the western sector of the Gulf of
Naples (Southern Italy), represents an archetypal case of caldera that underwent a very
large resurgence related to the intrusion of a shallow magma body. The resurgence
culminated with the formation of a structural high in the central sector of the island, i.e., the
Mt. Epomeo block. This is bordered by a system of faults along which volcanic activity
occurred up to 1302 A.D., and damaging earthquakes were generated in historical and
recent time. The seismicity is located prevalently in the northern sector of the island and
appears to be correlated with the most recent phase (<5 ka) of ground movement
(subsidence), although the mechanism of earthquakes’ generation is still debated. By
jointly analyzing offshore and onshore data (seismic profile and stratigraphy wells,
respectively) and new petrological and geochemical data related to the most recent
phase of volcano-tectonic activity, we develop a geological and structural layout of the
northern sector of the island. In particular, we identify the seismogenic fault associated with
the historical and recent destructive earthquakes of Ischia. This fault formed in the northern
sector of the island during the final stage of the resurgence.We also propose a conceptual
volcano-tectonic model of the northern sector of the Ischia Island, depicting the
displacement of the fault zones in the off-shore area and the possible mechanism of
stress loading and release in the on-shore zone, which is mainly driven by the subsidence
of the Mt. Epomeo block. Our results are crucial for evaluating the dynamics of the
seismogenic structures in the framework