Active structures in the Rioni foreland basin, Georgia

The Rioni foreland basin system lies between the Greater and Lesser Caucasus orogens and is located in the far-field part of the Arabia-Eurasia collision zone. Deformation of the Rioni double flexural foreland basin was controlled by the action of two opposing orogenic fronts, the Lesser Caucasus retro-wedge to the south and the Greater Caucasus pro-wedge to the north (e.g., Alania et al., 2022; Banks et al., 1997; Tibaldi et al., 2017).  Recent GPS and earthquake data indicate that the Rioni foreland basin is still tectonically active (e.g., Sokhadze et al., 2018; Tibaldi et al., 2020). Historical and instrumental seismic activity is concentrated along the frontal thrusts located along the northern and southern borders of the Greater and Lesser Caucasus orogens, and in the core of this foreland basin. All the focal mechanism solutions within the study area have a reverse and thrust fault kinematics (Tibaldi et al., 2020; Tsereteli et al., 2016). Fault-related folding and wedge thrust folding theories (Shaw et al., 2005) were employed in the interpretation of seismic reflection profiles and the construction of regional structural cross-sections across the Rioni foreland basin. Seismic profiles and structural cross-sections show that most earthquakes in the Rioni foreland basin occur at depths of 5-10 km.  In the Rioni foreland basin, fault planes do not necessarily reach the surface, and some active structures can be regarded as blind thrust faults, fault-bend and fault-propagation folds, duplexes, and these structures are mainly located at the frontal part of the Lesser Caucasus retro-wedge and the Greater Caucasus pro-wedge.