Time Correlation Analysis of the Microseismicity of the Low Eastern Flank of Mt. Etna Volcano (Italy)

—An analysis in terms of time correlation functions has been applied to the time distribution of microseismicity. We considered the single station detections (M < 2) recorded by each one of the four working stations of the network of the Osservatorio Sismologico di Protezione Civile, Acireale (Catania), located on the active faults systems (Timpe) of the low eastern flank of Mt. Etna. Information obtained on the time regularity of seismic crisis and on the time correlation between the activities recorded by different stations allowed a better understanding of the role of the two main structures. The Timpa di Santa Tecla is the most seismogenic structure in the area and probably played a role in the magma transfer process for the 1989 eruption. Modifications of the local stress field by actions of this feature may have produced gravitational instability along a second structural system (the Timpa di S. Leonardello) with a time delay of about 100 days. By contrast, magma penetration associated with the larger eruption of 1991–1993 had a deeper rise system and had no effect on local stress conditions, consequently there was no correlation between volcanism and seismicity.