Preliminary results from stress tensor inversion of earthquake fault-plane solutions in the southern tyrrhenian region

The method of Gephart and Forsyth (1984) for stress tensor inversion from earthquake faultplane solutions has been applied to 39 crustal seismic events from the region which includes Southern Calabria, Northeastern Sicily and the Aeolian Islands. We conclude that the stress tensor directions are not uniform in the study area because the misfit of the inversion is large if the entire data set is used, but the misfits for inversion of data from sub-regions are small. This result is expected on the basis of the geodynamic information available for the area. Inversion for the stress tensor in separate sub-volumes, defined according to the main structural features of the area, shows that the directions of the greatest principal stress vary from near vertical in Calabria to near horizontal with a strike of N2OE in eastern Sicily. These "best models" agree with geologic and tectonic data. At present, the difference in stress directions between the sub-volumes studied can only be asserted at a confidence level between 50% and 75%. due to the low number of earthquakes suitable far the application of the inversion procedure in each sub-volume. Far this reason, the stress space variation in the Southern Tyrrhenian region needs to be the subject of further investigations with richer data samples, but the present work is a useful basis far them, and far network improvements aimed at a development of this research topic.