Ground deformation patterns at Mt. Etna from 1993 to 2000 from joint use of InSAR and GPS techniques

Combined GPS measurements and radar interferometry (InSAR) have been applied at Mt. Etna to study the ground deformation affecting the volcano both over the long- (1993–2000) and short-term (1997–1998 and 1998–2000). The aim was to better understand the dynamics of the volcano during the magma-recharging phase following the 1991–93 eruption. Since 1993, InSAR and GPS data indicate that Mt. Etna has undergone an inflation. A deep intrusion was detected by InSAR, on the western flank of the volcano, between March and May 1997. In the following months, this intrusion rose up leading to a seismic swarm occurring in January 1998 in the western sector. This now shallow intrusion is confirmed by GPS data. From 1998 to 2000, a general deflation affecting the upper part of the volcano was detected. Over the whole study period, a continuous eastward to south-eastward motion of the eastern sector of the volcano was also evidenced. The analytical inversions of GPS data inferred a plane dipping about 12°ESE, located beneath the eastern flank of the volcano at a depth of 1.4 km b.s.l. The movement along this plane is able to reproduce the observed south-eastward motion of a sector bounded northward by the Pernicana fault, westward by the North–East Rift and the South Rift, and southward by the Mascalucia–Tremestieri–Trecastagni fault system. InSAR data have validated this model.