On December 30th 2002 the inhabited coastal areas of Stromboli Island were hit by a series of tsunami waves up to 10 metre high. Tsunami waves were the effect of at least two destructive landslides which involved the submarine and subaerial Sciara del Fuoco slope, respectively. Sciara del Fuoco is the NW flank of the Stromboli volcano, where the products of the volcanic activity accumulate. At present the NW flank looks like a regular slope above and below the sea level. Actually it is the result of a progressive infilling by volcanic products, of a large depression produced by a number of lateral collapses occurred until early historic times.
The landslides which induced the tsunami waves are the final result of a sequences of deep-seated slope-movements (at least down to a depth of 70 m)that involved the NE sector of the subaerial and submarine Sciara slope soon after the beginning of the eruption (e.g. December 28th). The complex evolution that resulted in the December 30th destructive landslides was reconstructed by a group of researchers belonging to the University of Rome "La Sapienza", Bologna University, Institute for Geophysics and Volcanology (Catania Section) and CNR Institute for Environmental Geology and Geo-engineering. Soon after the landslide events, this research group started, for the Dept. for Civil Defence, a specific study aimed also at evaluating the progressive evolution of the stability conditions resulting from the deep changes in morphology produced by an intense erosion and a huge volcanic activity of the Stromboli volcano.
A fundamental basis for the analysis of the instability phenomena and their interaction with volcanic activity, was represented by the studies that had been conducted by the same researchers for a long period preceding the events, within two research projects funded by the National Group of Volcanology. This previous research activity included high-resolution surveys of both submerged and subaerial slope morphology before the landslides as well as studies on the stability conditions of the slope.
These surveys were compared with those carried out few days after the slides (marine and aerial surveys were made extremely difficult by severe meteo-marine conditions) and couupled to the analysis of aerophoto stereo pairs and oblique photographs taken from the elicopter during the sequence of instability phenomena. Data were finally used for preliminar slope stability analyses in different loading conditions. This activity yielded a reconstruction of the sequence of slope instabilities and a first insight in the instability mechanisms.
A fundamental role was played both by intrusion within the slope of magma coming from the magmatic conduit (that triggered the initial deep-seated movements occurred at least one day before the 30th Dec. destructive landslides) and by the instability of the submarine slope, which initiated the general failure of the slope. At present the study is focused on the comprehension of the mechanisms which controlled the different slope instabilities. It is worth noting that the enormous difficulties deriving from the highly unfavourable logistics and continuous sliding/volcanic activity on the volcano slope that avoided direct (geotechnical/geophysical) investigations (only "remote" investigations were possible).
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