Impulsive tilt variations on Mount Etna volcano (1990-1993)

This study was focussed on the analysis of the fast ground deformations (impulsive anomalies) recorded at the Mt. Etna tilt array from 1990 to 1993, a period that preceded, accompanied and followed the 1991-1993 eruption. These fast deformations were recorded as transient anomalies ranging from a few hours to days (1-2), observed contemporaneously at several tilt stations, and characterized by variations ranging from one to tens of microradians. The signals evidenced volcanic dynamics characterized by tilt anomalies during the non-eruptive periods (1990, 1993), the pre-eruptive period (November-December 1991), the beginning of the eruption (14-15 December 1991) and the eruption course (1992). In particular, pre-seismic, co-eruptive and co-seismic anomalies were recorded during the pre-eruptive period and the eruption onset. In these cases, interpretations of the phenomena and comparison to modelling studies are provided. Furthermore tilt variations affecting the global volcanic edifice were also observed one year before the eruption, when they were followed by seismicity, and during the eruption course without seismicity. We interpreted this last class of tilt variations as due to the push of the magma uprising along the main NNW-SSE structure crossing Mt. Etna.