Evaluating the seismic activity of the Adriatic Sea region

The seismic activity occurred in the last decades in the Adriatic Sea region has been investigated by means of new hypocenter locations, waveform inversion focal mechanisms and seismogenic stress fields. After a preliminary evaluation of seismic distribution, the Bayloc non-linear probabilistic algorithm has been used to compute hypocenter locations for the most relevant seismic sequences and to carefully evaluate location quality and seismolineaments reliability. We also provided an updated database of waveform inversion focal mechanisms integrating data available from official catalogs with original solutions we properly estimated by applying the waveform inversion method Cut And Paste. This database has been used to compute seismogenic stress fields through different inversion algorithms. The seismic activity, mainly concentrated in the Central Adriatic region, indicates high fragmentation and different patterns of deformation. In particular, our results highlighted the presence of two NW-SE oriented, adjacent volumes: (i) the northeastern one, characterized by pure compressive domain with NNE-trending axis of maximum compression, and mainly W-to-NW oriented seismic sources; (ii) the southwestern one, characterized by a transpressive domain with NW-trending axis of maximum compression, where thrust faulting preferentially occurs on ENE-to-NE oriented planes and strike-slip faulting on E-W ones. We jointly evaluated seismic findings of the present study and kinematic models proposed in the literature for the Central Adriatic region. The present analysis, furnishing new seismological results provide additional constraints useful for better understanding and modeling the seismotectonic processes occurring in the Adriatic Sea region.