ИСТИНА

The Ossetia part of the Great Caucasus is located within the Trans-Caucasian uplift. According to modern understanding this large structure is the northern ending of the planetary-scale structure - the East-African Trans-Caucasus rift zone. This region, being one of the most tectonically active regions of the Caucasus, was not covered by satellite geodetic measurements made in the Caucasus and surrounding areas since the early 1990s [Shevchenko, V.I. et al., 1999; Reilinger, R. S. et al., 2006]. The network of survey-mode sites was established in this area during the campaigns of 2010-2011. This network crosses from north to south the main tectonic structures of the Ossetia part of the Great Caucasus: the northern and southern slopes of the Great Caucasus ridge, the Tibskii thrust fault, the Northern Caucasian step, the Orkhevskii thrust fault, the Georgian block. The main profile of the network is oriented from north-east to south-west. The other two profiles are transverse to the main one and are oriented from west to east. The first of them is located along the southern and northern borders of the Orkhevskii thrust fault, covering the area of the Racha 1991 earthquake, with release to the Gagra-Dzhava zone. The second of them passes along the northern slope of Great Caucasus Ridge, its new sites will cross a series of thrusts of the Rocky Ridge. The GPS data measured during two-years campaigns were processed using the GAMIT/GLOBK software. As the reference sites we use the permanent GPS stations of the Northern Caucasus deformation array [Milyukov et al., 2010]. The GPS-derived velocities provide some constrains on the geodynamical motion of the study area and complement the velocity field obtained for the surrounding areas. The resulting velocities will provide the first relatively complete and detailed pattern of modern horizontal displacements of some elements within the Caucasian mountain structure.