Abrupt magma chamber contraction and microseismicity at Campi Flegrei, Italy: Cause and effect determined from strainmeters and tiltmeters

摘要: In March 2010 two borehole strainmeters and three Michelson tiltmeters within the Campi Flegrei volcanic system, Italy, registered an abrupt deformation signal that was followed 20 min later by seismic slip on a pair of onshore normal faults. We demonstrate observed strain changes were caused small but rapid volume decrease in previously identified offshore ellipsoidal magma source or part it. Although total deflation below detectability interferometric synthetic aperture radar GPS, rates briefly 2 orders magnitude more than decadal inflation rates. conclude this high dilatational contraction rate responsible for triggering seismicity process may be faulting often region. Our study quantifies crucial role played transient, minor reduction stress, fault near critical failure. subsurface measurements tilt anomalous sigma above background noise levels 17 min before onset microseismicity suggesting have potential utility as early warning system city Naples.