Structural features of the Neapolitan Yellow Tuff (NYT) collapse caldera-resurgent dome system in the Campi Flegrei offshore sector, Southern Italy.

The present study contributes to understanding the evolution of the Campi Flegrei resurgent caldera in the Pozzuoli Bay (Southern Italy), through the interpretation of high-resolution seismic profiles from several datasets.

The Pozzuoli Bay is floored by a multi-phase resurgent dome system nested in the collapse caldera related to the Neapolitan Yellow Tuff eruption (15 ka BP).

Due to its resteless history, from caldera forming eruptions to small scale explosive eruptions, Campi Flegrei recent and ongoing unrest episodes make the urban area of Naples and Pozzuoli one of the world's highest volcanic risk areas.

Starting from the distribution and stratigraphic position of ash fall tephra deposits, constrained with gravity cores, a seismostratigraphic frame has been reconstructed to define the chronology of collapse-resurgence related faults. Detailed mapping of faults led to propose a new structural map of the offshore sector of the Campi Flegrei caldera, implementing the onshore knowledge. The map features both collapse-faults in the apical area and part of the ring sector related to caldera collapse, where faulting is associated to emplacement of limited intrusive bodies.

The apical faults are arranged in a piece-meal pattern and have been distinguished based on their age and amount of displacement, generally within few meters. The observation that several faults involved in collapse of the dome apical area cut the sea-floor suggest that they could have been active during the last bradyseism crisis in 1983-1984, that led to evacuation of the town of Pozzuoli.

The dome system is bordered to the south by the inner ring faults of the caldera. This Southern border shows a reactivation in the western sector due to a laccolite intrusion (Punta Pennata laccolite). Moreover, has been possible to delineate, on the eastern side of the bay, the Bagnoli laccolite geometry and extension.