THE GLOBAL POSITIONING SYSTEM AS A USEFUL TECHNIQUE FOR MEASURING GROUND DEFORMATIONS IN VOLCANIC AREAS

In this paper the Global Positioning System technique for measuring ground deformations in volcanic areas is presented. After an outline of the mathematical background, the results of three years' experience regarding the use of this technique on Mt. Etna are reported. The ground deformation patterns recorded between 1989 and 1991 are shown and discussed in the geodynamic framework which characterized Mt. Etna in the time interval considered. Attention is focused on modeling a ground deformation episode which occurred on Mt. Etna between 1990 and 1991 which contributed to characterizing the dynamic framework where the 1991-1992 eruptive event took place. The deformation pattern mentioned has been interpreted by using a dislocation model. The optimal solution for the inversion problem has been found by using an optimization approach based on the simplex method. This solution agrees with the regional stress field whose compressive direction is NNE-SSW oriented.