Inferences on the main volcano-tectonic structures at Mt. Etna (Sicily) from a probabilistic seismological approach

We analysed earthquakes at Mt. Etna fur the period 1983-1991 using a method that weights uncertainties in hypocentral location. Three-dimensional dist ributions of 'hypocentral probability and 'energy density' were studied, an d two first-order volcano-tectonic structures identified. The first, on the northern and western sides, is roughly NE-SW oriented, and strongly marks the northernmost limit of earthquake occurrences in the vulcano region; the second, NNW-SSE trending, affects the south-eastern flank of the volcano, and is evidence for an almost aseismic uprise of magma along it. Both struc tures fit well with the geodynamic framework of eastern Sicily. On the cont rary, there is no evidence for a main magma chamber, as postulated in the l iterature.