CHANGES IN THE STRESS REGIME AND DISPLACEMENT FIELD IN THE INTERIOR OF MOUNT ETNA DEDUCED FROM SURFACE OBSERVATIONS

If measurements of all three components of displacement at the surface of a mountain are available, the stress-strain relations of the theor y of linear elasticity can be used as a simple approximation to obtain insight into changes that take place on a relatively short time-scale in its interior. If such a simple elastic model is employed, interpol ated values derived from these data can be used as boundary conditions at the surface of the mountain and then integrated downwards this pro cedure yields values for the internal displacements that take place fr om year to year from which changes in the internal stress distribution s can be calculated. The location of regions in which the solutions ob tained by this approach give inappropriate results indicate where the assumptions of linear elasticity do not hold, and so provide further e vidence in the task of determining internal structure. Measurements ar e available from 1987 to 1992 for all three components of displacement at a substantial number of points on the surface of Mount Etna in int ervals of not more than a year, and the method was applied to them to obtain evidence of regions in the interior of the volcano deserving fu rther study.