Spatiotemporal variations in vertical gravity gradients at the Campi Flegrei caldera (Italy): a case for source multiplicity during unrest?

SUMMARY We present an evaluation of residual vertical gravity‐height change gradients obtained from gravimetric and elevation data between 1982 and 2000 at the Campi Flegrei caldera (CFc) in Italy. Spatial and temporal variations in the gradients are indicative of multiple causative sources during unrest, in particular for ground subsidence from 1988 onwards. Supported by results obtained from time-series inversion for the period 1988‐2000 using a random search approach of a purely elastic earth model and a genetic algorithm accounting for elastic-gravitational effects, we propose a centre of dilatation undergoing predominantly pressure changes yet negligible mass changes as the dominant cause for caldera deflation. Mass fluctuations in randomly active secondary sources along the periphery of the CFc can be best explained by dynamic changes along the caldera boundary (ring) faults.

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