Investigation of the Active Deformation in the Caucasus Region from Seismic and Geodetic Observations

Abstract

The deformation and shortening in the Caucasus region are predominantly driven by the collision of Arabian and Eurasian plates with a possible contribution of the lithospheric deformation beneath the Caucasus.  The tectonic uplift/inversion, along with the formation of the Greater and Lesser Caucasus fold and thrust belts, is driven and maintained by the continental collision of the Arabian and Eurasian plates. However, the dominant factor for the regional variations of surface deformation and sub-crustal seismic activity, whether lithospheric delamination or slab detachment beneath the Caucasus region, is not well understood. Moreover, the variations in shortening along the Caucasus cannot be solely explained by plate boundary forces without constraints from lithospheric dynamics. The large uncertainties of the models lead to limited understanding of the formation and active deformation of this fold and thrust belt. The main reason for this shortcoming is the limited access to the seismic and geodetic data in the region. In this study, we merged seismic and geodetic data from Russia and surrounding countries.  We constructed a joint database for the period between 2007 and 2010 and updated 1D crustal velocity models for four sub-regions. We obtained the relocated seismicity within each region using the local velocity models. In addition, we updated the earthquake source mechanisms catalog in the Caucasus region.  A new Pn tomography model is computed using the new catalog. The crustal thickness variations are recomputed from receiver function analysis using the broad-band stations of Russia. We also update block boundaries and corresponding slip rates in the study region using both seismicity and geodetic data.