Delineation and Fine-Scale Structure of Fault Zones Activated During the 2014–2024 Unrest at the Campi Flegrei Caldera (Southern Italy) From High-Precision Earthquake Locations

In the past two decades, the central portion of Campi Flegrei caldera has experienced ground uplift up to 15 mm/month, with an increase of rate, magnitude and extent of the seismicity. In this work, we perform multi-scale precise earthquake relocation of the 2014–2024 seismicity, mapping in detail activated fault zones. We relate the geometry, extent, and depth of these zones with up-to-date structural reconstructions of the caldera. The current seismicity is mainly driven by ground-uplift-induced stress concentration on pre-existing, weaker fault zones, some of which identified for the first time. These structures are not only related to the inner caldera and dome resurgence but also to volcano-tectonic events of the last 10 ka. The extent of imaged fault segments suggests they can accommodate ruptures up to a moment magnitude 5.1, significantly increasing seismic hazard in the area.