Seismicity supports the theory of incipient rifting in western Ionian sea, Central Mediterranean

The present work focuses on earthquake locations and seismogenic stress in the eastern offshore of Sicily, a sector of the central Mediterranean region where geophysical information available is not good enough, yet, for proper geodynamic modeling. I have applied to an updated seismic database of the study area a Bayesian non-linear hypocenter location method already proven to be more effective than linear methods when the recording network geometry is poor, like in the present case. Then, I have selected from literature and official catalogs the local earthquake focal mechanisms computed by waveform inversion, and inverted them for stress tensor orientations. The results confirm the main finding of the previous investigations, i.e. that NW-trending convergence between Africa and Eurasia is a main source of tectonic stress in this area, however they also furnish evidence of additional tectonic factors locally acting together with convergence. In particular, extensional dynamics are detected inside the convergence-related compressional domain: These are characterized by a minimum compressive stress oriented SW-NE (perpendicular to convergence) and can be related to the rifting process (opening SW-NE) detected by previous investigators at the southwestern edge of the Ionian subduction slab. The findings of the present study may also concur to answer several open questions left by previous investigators.