Ground deformation at Mt. Etna: a joint, interpretation of GPS and InSAR data from 1993 to 2000

Combined Global Positioning System (GPS) measurements and Interferometry SAR (InSAR) have been applied on Mt. Etna to study the ground deformation affecting the volcano both over the long (1993-2000) and short-term (1997-2000). From 1993 to 1997, data indicate a re-pressurization of Mt. Etna's plumbing system that i) triggered most of the seismicity, ii) induced the dilatation of the volcano, and iii) produced a series of summit eruptions since 1995. InSAR detected a deep intrusion on the western flank of the volcano, between March and May 1997. In the following months, this intrusion rose leading to a seismic swarm in the western sector occurring in January 1998. The shallow intrusion is confirmed by GPS data. From 1998 to 2000, a general deflation affected the upper part of the volcano. Elastic deformation modelling of GPS data suggests that the active sources of deformation include deep pressure sources located beneath the upper western flank of the volcano, shallow dislocation sources (dikes and faults) located beneath the NE and S rift zones, and a sub-horizontal dislocation plane (dipping about 12 degrees ESE), located beneath the western flank of the volcano at a depth of 1.4 km b.s.l.. InSAR data validated these models.