Abstract
Seismicity at Mt. Etna, as in other volcanic areas, is usually defined as seismo-volcanic activity. However, a large class of earthquakes, named volcano-tectonic (VT), shares similar characteristics to those of seismic events acquired in tectonic environments. In the past, most of the ambiguities engendering a general mistrust in using simple source models originated from poor constraints on foci or unsatisfactory coverage of the focal sphere. Recently, after the Mt. Etna seismic network was boosted, more detailed analyses have been performed, allowing to verify that most of the earthquakes can be interpreted in terms of shear failure and their mechanisms can be considered to derive from the classical double-couple system of forces. This is supported by structural and geological evidences, as well as by the space-time features of seismicity and focal mechanism results, which confirm the important role played by regional tectonics at Mt. Etna. In this work we will present the state of the art of the source mechanism studies performed on Etnean VT earthquakes and discuss the role of attenuation effects and site response which strongly contribute to determine the appearance of seismograms. The results of the evaluation of the seismic moments and fault dimensions will be also discussed in order to compare Mt. Etna source scaling with those of other volcanic and non-volcanic areas in the world. Finally, some considerations on faulting processes, on the directivity effects and on the presence in the first P-pulse of a nucleation phase preceding a phase of high-speed rupture propagation will be provided.
Published Version
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