Source modelling from ground deformation and gravity changes at Campi Flegrei caldera

Abstract

The deformation history of the Campi Flegrei caldera during the last decades consists of two large uplift events in 1970-72 and 1982-84, with ~ 3.5 m cumula-tive uplift, occurring at a rate of ~ 1 m/yr. Both events were accompanied by seismic activity, gravity changes and compositional variations of volcanic gasesbut no eruption took place. During the following decades,the area has been slowly subsiding but minor uplift episodes (~ a few cm), seismic swarms and changes in degassing activitytook place, showing that the area persistedin a near-critical state.Since 2004, ground deformation resumed, although at a slower rate, totaling a displacement of ~ 0.6 m at the time we write(2019). In this chapter,we present a retrospective analysis of ground deformationleading to acritical re-evaluationof the 1982-84 uplift and of the following deflation, employing the most updated modeling techniques. Deformation and gravity data provide important constraints on depth, volume, mass density and dislocation mechanisms accompanying mag-ma emplacement processes but the correct evaluation of these parameters is strongly conditioned by simplifying assumptions built in the different inversion procedures: in particular, the inferred depth ranges from 5.5 km to less than 3 km and the intrusion density ranges from values pertinent to aqueous fluids to typical magmatic values. This review depicts the salient phases of the deformationhistory of this densely populated and high risk volcanic area, helping to address debated issues, such as the role of the magmatic system, and theirinteraction with the shal-lower hydrothermal system.In spite of the mentioned difficulties, the following conclusion may be considered as firmly established: during 1982-84 a magmatic intrusion took place, and the subsequent complex deformation history (1985-2010) was mainly controlled by the exsolution of volatiles withmagmatic origin and their interaction with a shallow hydrothermal system. However, data collected af-ter 2011 were modelled in terms of a deeperinflating source of deformation, pos-sibly resulting froma resumed magmatic recharge at depth.