SLOPE MOVEMENT CRISIS ON THE EAST FLANK OF MT ETNA VOLCANO - MODELS FOR ERUPTION TRIGGERING AND FORECASTING

Benchmarks installed on the upper eastern flank of Mt. Etna in 1982 ha ve subsided continually since then, with the rate of subsidence twice accelerating prior to eruptions. The first of these eruptions was in D ecember 1985, and the second in September 1989. This pattern of accele rating downslope movement has also been observed prior to landslides, and recent work applying knowledge of the failure of materials has sho wn that analysis of the inverse rate of these movements can be used to predict the time of failure. Post-eruption analyses of geodetic or se ismic data from volcanoes has shown that in several cases, this approa ch could have been used to forecast eruptions weeks in advance. Applyi ng the same principles to the accelerating subsidence on Mt. Etna's ea stern flank prior to the eruptions of 1985 and 1989 shows that rough e stimates of eruption dates could have been obtained several months in advance. These observations also suggest a speculative eruption-trigge ring mechanism involving an interplay between slope creep deformation and extensional weakening over the zone of intrusion.