Seismically active thrust faults and wedge structures beneath the western Greater Caucasus orogen pro-wedge, Georgia

The Greater Caucasus is a typical active double wedge orogen that accommodates the crustal shortening due to far-field effects of the collision between the Arabian and Eurasian plates. Our study area is the western part of the Greater Caucasus pro-wedge, represented by the central and northern parts of the Rioni Foreland basin and the southern slope of the Greater Caucasus. Here, we present a new structural model based on interpreted seismic profiles, regional structural cross-sections, and earthquake focal mechanisms. From SSW to NNE, serial structural cross-sections reveal: (1) basement-involved thrust faults and thick-skinned fault-bend folds, and (2) thin-skinned structures expressed as duplexes and imbricate fault-propagation folds. The dominant compressional structural styles are controlled by multiple detachment horizons.

According to the presented serial structural cross-sections, the Enguri HPP dam is located on top of the triangle zone. Major basement-involved thrusts produce first-order thick-skinned fault-bend folds, which move southward, creating second-order fault-propagation folds and duplexes in the sedimentary cover. Preexisting, basement-involved extensional faults inverted during compressive deformation produced basement-cored uplifts that transferred thick-skinned shortening southward onto the thin-skinned structures detached above the basement.

The correlation of earthquake hypocenters and focal mechanisms with faults interpreted from 3D structural models enables the identification of active structures. Five potentially active thrust faults are recognized within the study area. Four of these structures are south-vergent thrusts, whereas one corresponds to an out-of-sequence thrust.

Acknowledgments. This work was funded by Shota Rustaveli National Science Foundation (SRNSF) (grant# FR-23-8896).