Faulting induced by underground magma migration: new insights from detailed field analysis (Campi Flegrei, Italy)

Faulting triggered by magma migration at depth is a not-rare phenomenon in volcanic areas, where they can be found at very different scales. By analogue and numerical models, it has been shown that these types of faults can display a complex structure that often comprises an array of fault segments with both normal and reverse senses of movement. In this work, we analyzed in detail, and for the first time using field data, a fault array associated with the collapse induced by underground magma migration. The fault array crops out in cross-section within a recent volcanic succession in the Campi Flegrei caldera (southern Italy). Analyses focused on defining the spatial and temporal relationships between the normal and reverse fault segments of the fault array to provide insights into the process of collapse development. Based on geometric and displacement data, we propose that normal and reverse faults likely acted simultaneously to accommodate the collapse after a rapid phase of fault propagation.