DYNAMIC INVERSION OF GROUND DEFORMATION DATA FOR MODELING VOLCANIC SOURCES (ETNA 1991-93)

The 1991-93 Etna eruption, that represented the most important recent eruptive event both in terms of duration (472 days) and total volume o f erupted lava (ca. 250(.)10(6) m(3)), caused marked ground deformatio n measured by using different geodetic techniques such as EDM, GPS, le velling, and tiltmetry. An inversion, termed ''dynamic'' because it to ok into account the sequence of events considering both the separate a nd cumulative effects of two sources, (a shallow tensile crack and a d eeper ellipsoidal deflating source), was performed. It was based on 16 3 data collected by the different techniques plus 2 geometrical condit ions for constraining the geometry of the crack on the surface. The fi nal solution furnished a good fit for all measurements, defining a sha llow tensile crack located inside the volcanic edifice, which represen ts the effect of the intrusion, and a depressuring body with centre at ca. 3000 m b.s.l., which could represent the centre of a generalized and more complex deflation of the volcanic edifice during the course o f the eruption.