Ambient Seismic Noise Image of the Structurally Controlled Heat and Fluid Feeder Pathway at Campi Flegrei Caldera

Earthquakes at Campi Flegrei have been low-magnitude and sparse since 1985, denying on-shore monitoring observations of their usual source for structural constraint: seismic tomography. Here, we used continuous seismic records
from 2011-13 to reconstruct period-dependent Rayleigh-wave group-velocity maps of the volcano. The Neapolitan Yellow Tuff rim faults bound high-velocity intra-crater products of historical eruptions, which act as a barrier for deep fluid migration. The anomaly with lowest group velocity is aseismic and corresponds
to the portion of a fluid-storage zone that was fractured during the 1984 volcanic unrest under Pozzuoli town. Earthquake locations show that fluids migrate from this area towards the Solfatara and Pisciarelli fumaroles along shallower low-velocity fractures. The aseismic anomaly is likely fed by a deep-seated offshore magmatic source. Its spatial relation with regional dynamics and observations from historical unrests mark the area as the most likely feeder
pathway for fluid and magmatic inputs from depth.