Recent seismicity in the Messina area, southern Italy, and comparison to the local geology and tectonics

We have investigated the seismicity occurred during 2000-2021 in the area of Messina, the town which suffered greatest loss of human lives over the territory devastated by the magnitude 7.1 earthquake of December 28, 1908. We have found that most of recent activity was located beneath the historical centre of the town, in and near the very peculiar sickle-shaped harbor zone which prompted the Greek colonizers in the VII Century B.C. to give Messina the old name of “Zancle”(“Sickle” in the ancient Greek language). Extracting from the whole dataset (consisting of hundred earthquakes of maximum magnitude 3.8) the data relative to a small sequence of 28 events concentrated in a few days at the end of 2013, and performing high-quality Bayesian hypocenter locations of these events, we have found very clear epi-hypocentral trends suitable for comparison with the local structural scenario. The joint analysis of seismic, geological and geomorphological data including morphobathymetric curves of the sea bottom in the study area, has brought us to propose that the small sequence in question (and probably most of activity recorded during the whole 22-years period) may have been generated by internal dynamics of a local horst/graben system, the position of which (i) appears to correspond to one of the minor horsts documented in the Messina Strait basin area and (ii) is very close to the upper edge of the 1908 earthquake blind source reported in the Database of Individual Seismogenic Sources of the Italian National Institute of Geophysics and Volcanology.