Seismic source identification of the 9 November 2022 Mw 5.5 offshore Adriatic sea (Italy) earthquake from GNSS data and aftershock relocation

The fast individuation and modeling of faults responsible for large earthquakes are fundamental for understanding the evolution of potentially destructive seismic sequences. This is even more challenging in case of buried thrusts located in offshore areas, like those hosting the 9 November 2022 Ml 5.7 (M-w 5.5) and M-L 5.2 earthquakes that nucleated along the Apennines compressional front, offshore the northern Adriatic Sea. Available on- and offshore (from hydrocarbon platforms) geodetic observations and seismological data provide robust constraints on the rupture of a 15 km long, ca. 24 & DEG; SSW-dipping fault patch, consistent with seismic reflection data. Stress increase along unruptured portion of the activated thrust front suggests the potential activation of longer portions of the thrust with higher magnitude earthquake and larger surface faulting. This unpleasant scenario needs to be further investigated, also considering their tsunamigenic potential and possible impact on onshore and offshore human communities and infrastructures.

Automated summary

The rapid identification and modeling of faults responsible for major earthquakes plays a crucial role in understanding the evolution of potentially destructive seismic events. This becomes even more challenging when dealing with buried thrust faults located in offshore areas. In the case of the Ml 5.7 and M-L 5.2 earthquakes that occurred along the Apennines compressional front offshore the northern Adriatic Sea, geodetic observations and seismological data provide valuable insights into the rupture characteristics of a 15 km long fault. The potential activation of longer fault segments with higher magnitudes and larger surface faults is a concerning scenario that requires further investigation, considering the tsunamigenic potential and possible impact on human communities and infrastructure.