Modern Horizontal Movements in the Zones of Strong and Moderate Earthquakes of the Early 21st Century in the Central Sector of the Greater Caucasus: Characteristics Inferred from GPS Observations and Connection with Neotectonics and Deep Structure of the Earth’s Crust

Analysis of GPS-measurements made for the first time along the geodesic profile crossing all the main geological structures in the Ossetian region of the Greater Caucasus showed that significant jumps in the velocity of horizontal movements are observed in zones where strong earthquakes recently occurred. Interpretation of the measurement data is performed in comparison with the results of neotectonic and seismotectonic studies and data on deep structure of the region. The maximum decrease in the current transverse shortening rates is recorded in the zones of the Vladikavkaz and Kakheti–Lechkhum faults. The zone of the Vladikavkaz Fault hosted the source of the Khataldon earthquake of May 11, 2008, M = 4.5, I = 4 in the epicentral zone. Epicentral zones of earthquakes such as the 1991 Racha with М = 7.0, 1991 Dzhava with М = 6.2, Oni-I of February 6, 2006 with М = 5.0, and Oni-II of September 7, 2009 with М = 6.0 involved the upper crustal blocks within the limits of the Kakheti–Lechkhum suture zone at the base of the southern slope of the Greater Caucasus. The previously predicted significant decrease in the rate of horizontal movements after seismic activations in these areas of catastrophic seismic events of 1991, 2006, and 2009 on the southern slope of the Greater Caucasus is confirmed.