Vertical ground deformation on vulcano, Aeolian islands, Southern Italy: Observations and interpretations 1976–1986

Abstract

Vertical ground deformation studies have continued on Vulcano (southern Italy) since 1976 as part of a broader geophysical and geochemical program to monitor activity on the island. Following a magnitude 5.5 earthquake on 15th April 1978, located a few kilometers south of Vulcano, the northern part of the island was found to have subsided relative to its southern part. Two further episodes of displacement, the first of inflation and the second of deflation, were recorded before September 1981. These displacements have been interpreted using a model that considers the effect of pressure change at the point source located at a depth centered at 6.5 km in the northern part of the island. Such pressure change, according to other geophysical and geochemical data, is due to increasing and subsequent decreasing pressure connected with the migration of high-temperature fluids through fractures and channels beneath the Fossa area opened as a result of the April 15 earthquake. Subsequent measurements, until November 1986, detected only one additional significant movement, a small inflation between May 1984 and May 1985. This uplift appears to be related to the shallow seismicity recorded beneath the Fossa in this period.