A gravitational origin for volcano-tectonic faults in the Campi Flegrei caldera (southern Italy) inferred from detailed field observations

Faults in volcanic areas can have different origins and can form due to several volcano-tectonic processes. In this work, by means of detailed field observations, we analysed a fault array cutting through a recent pyroclastic succession in the Campi Flegrei caldera of southern Italy to investigate its origin. Geometric and kinematic data indicate that the fault array consists of steeply dipping faults with both normal and reverse senses of movement. Displacement data suggest that these faults with opposed kinematics acted simultaneously, in agreement with what was previously described from analogue and numerical experiments for faults formed in response to gravitational collapses in volcanic areas. By integrating these results with considerations of the recent volcano-tectonic evolution of the Campi Flegrei caldera, we propose a model in which the studied fault array developed to accommodate a gravitational collapse triggered by an underground magma migration predating the 1538 CE historical Monte Nuovo eruption. This work is, to our knowledge, the first thorough field description of faults developed to accommodate gravitational collapses in volcanic areas.