New borehole strain system detects uplift at Campi Flegrei

Abstract

Campi Flegrei and Mount Vesuvius are active Italian volcanoes though presently in aquiescent stage. The last eruption of Mount Vesuvius occurred during the spring of 1944. Campi Flegrei last erupted in 1538 but experienced a subsidence trend from the early 1900s to 1970, which was followed by episodes of ground uplift accompanied by seismic swarms [see, e.g., Aster et al., 1992].Over the past 37 years at Campi Flegrei, about 4 meters of maximum ground uplift has occurred followed by about 1 meter of subsidence, as measured near the center of the caldera in two episodes during 1970–1972 and 1982–1984. This deformation has occurred close to the harbor of the town of Pozzuoli, putting about 400,000 people at heightened risk. From 1985 to 2004, Campi Flegrei's caldera showed gradual subsidencethat was interrupted by five mini‐uplift episodesin 1976, 1989, 1995, 2000, and, most recently, 2004–2006, each amounting to a few centimeters of uplift [Pingue et al., 2006]. The caldera is generally aseismic during gradual subsidence, but small swarms of microearthquakes are produced during periods of elevated strain rates associated with the mini‐uplift episodes [Saccorotti et al., 2001 ].