Kinematic reconstruction of active tectonic and halokinetic structures in the 2021 NW Palagruža earthquake area (Central Adriatic)

Abstract

In March 2021, a compressional earthquake sequence (mainshock M_w 5.2) occurred in the Central Adriatic Sea, offshore Croatia. The struck area is characterized by a complex tectonic settings due to due interaction between tectonic and halokinetic structures. Former studies in this region, mostly based on geophysical and seismological data, do not provide a comprehensive description of the geological complexities of the area, caused by the presence of different types of active structures. Following the interpretation and depth conversion of a set of seismic reflection profiles, we present a kinematic restoration to obtain the shortening rates for the last 6 Myr. We highlight the presence of three main types of active structures: i) shallow thrusts and related folds deforming the seafloor, ii) deep thrusts promoting large-scale deformation, iii) halokinetic structures deforming, at least, the Messinian. We highlight how the structural setting of the area is more complex than previously interpreted, with a possible decoupling of shallow and deep structures and an interaction between tectonic and halokinetic structures. This work opens new perspectives about the role of halokinetic processes in active seismogenic areas.