Preliminary Results from Comprehensive Seismic and Geodetic Observations Around the Caucasus Region

The active deformation and shortening in the Caucasus region are predominantly driven by the collision of Arabian and Eurasian plates where significant differences in the surface uplift, large basins, variations on the plate motion rates along the convergence are observed. To the west of the region the lack of sub-crustal seismic activity, low velocity anomalies in tomographic images and the decreased rate of shortening imply that western Caucasus has different kinematics compared to its east. Previous studies suggested that either slab detachment or lithospheric delamination is responsible for the complex deformation beneath the Caucasus. Large uncertainties due to sparse and non-uniform data coverage for local and regional tomography studies, diffuse seismicity, significant crustal thickness variations and strain field lead to poor understanding on the formation and active deformation of this fold and thrust belt. In this study, we aim to obtain a joint database collected from Turkey and Russia between 2007 and 2020. A waveform data base is created from 37 stations in Russia and more than 60 stations in Turkey. An improved seismicity catalog is built including relocated earthquakes with more than 100 stations. The crustal thickness map of the study region is updated by receiver function analysis using stations both from Turkey and Russia covering the Greater Caucasus. A high resolution P_n tomographic model is computed to determine velocity perturbations in uppermost mantle. The data from GNSS (Global Navigation Satellite System) stations both in Turkey and Russia are processed together for the first time and used to map the updated strain field. The new strain field is correlated with the crustal stress orientations from earthquake source mechanisms. New block models are determined for the Caucasus region in order to better estimate the block boundaries and related slip rates. By the improved azimuthal coverage of the seismic and geodetic stations the uncertainties of vertical and horizontal earthquake locations and the velocity field are reduced, thus; a reliable source for the geometry and kinematics of the faults in the Caucasus region is obtained. With the improved seismological and geodetic observations, reliable inferences on the seismic hazard and earthquake potential is expected for the region.