Dike emplacement forerunning the Etna July 2001 eruption modeled through continuous tilt and GPS data

[1] Late on the night of July 17, 2001, a lateral eruption started from the slopes of Mt. Etna. A 7 km long field of ground fractures opened between 13 and 20 July. The eruption ended on August 9, 2001 after emitting a lava volume of approximately 48 . 10(6) m(3). A strong seismic swarm earthquake was recorded between July 12 and 17. The evolution leading up to the July crisis was monitored through continuous tilt and GPS measurements, which constrained the intrusion preceding the eruption in time, and inferred the position and geometry of the uprising dike. We modeled the marked ground deformation changes recorded in the days before the eruption onset. The result shows that a tensile crack with an opening dislocation of ca. 3 m, crossing the volcano edifice slightly southeast of the crater area, can explain the recorded deformation pattern. The location of the modeled tensile source fits the zone of the seismic swarm occurring during the magma uprising. The ground deformation pattern associated with the final uprising and its modeling suggest a very fast dike emplacement which appears different, both in terms of rapidity (only a few days) and source position, with respect to the sources modeled for the other lateral eruptions in the last twenty years.