Thrust fault maturity and coseismic behavior. Insights from the 2022 Mw5.8 Adriatic offshore earthquake

Fault maturity has long been recognized as a critical control on coseismic behavior, but its influence remains underexplored in compressional settings, particularly offshore. This study investigates the offshore 2022 Mw5.8 earthquake in the northern Adriatic Sea using an integrated multidisciplinary approach that combines seismic reflection data, well logs, on- and offshore GNSS measurements, and instrumental and historical seismology. We identify the northwestern segment of a regional thrust (the Cornelia thrust) as the seismogenic source, where the thrust geometry, the low cumulative displacement (<0.3 km), and the structural setting suggest limited fault maturity. Our finite-fault model reveals a down-dip propagating rupture and a low rupture velocity (~1.3 km/s), markedly lower than values typical for mature thrusts. The integration of geological and seismological obser- vation, highlights how structural immaturity correlates with seismic behavior. In particular, our analysis con- firms that low rupture velocities are indicative of fault immaturity, also along active thrust fronts. Furthermore, GNSS data constrain a long-term slip rate of ~1 mm/yr for the thrust, consistent with geolog- ically derived longer-period rates. The joint analysis of coseismic slip with long-term strain accumulation and historical seismicity provides significant clues for the seismic cycle. These findings provide new insights into the seismogenic potential of immature thrust systems and emphasize the importance of evaluating fault maturity as part of seismic hazard assessment, particularly in offshore compressional belts where direct observation is limited.