The Campi Flegrei Nested Caldera (Italy): A Restless, Resurgent Structure in A Densely Populated Area

The Campi Flegrei caldera is a resurgent, nested structure formed mainly after two collapses related to the Campanian Ignimbrite (37 ka) and the Neapolitan Yellow Tuff (12 ka) eruptions. The structural boundaries of both calderas are partly controlled by reactivation of earlier regional fault systems. There has been ongoing resurgence inside the youngest caldera since its collapse, through a complex simple-shear mechanism. This resurgence has disjointed the caldera floor in blocks through long-term deformations over the past 12 ka. During this period volcanism occurred along the marginal faults of the youngest caldera and in the northeastern part of the resurgent block. Although large part of the caldera floor is deformed, the conditions for magmas to rise to surface were not established in the southwestern sector of the resurgent block. The caldera has shown signs of unrest in the last 27 years with short-term deformations that have generated a maximum net uplift of 3.5 m. The short-term deformations are interpreted as the result of a brittle and a ductile component. The long-term deformations likely represent the summation of the permanent, mostly brittle component of each short-term deformational event.