TECTONIC POSITION, SISMOLOGICAL AND GEOLOGICAL MANIFESTATION OF 7 SEPTEMBER 2009 ONI-II EARTHQUAKE FOCUS ON THE SOUTHERN SLOPES OF THE GREAT CAUCASUS

Abstract

The article provides seismological and seismotectonic materials about the main shock and aftershocks of the Oni-II earthquake of 7 September 2009, with MS = 5,8 on the South slope of the Greater Caucasus. The position of the cloud of epicenters of the main shock and aftershocks coincides with the northern branch of the focal zone of 29.04.1991 Racha earthquake, MS = 7,0, I0 = 7-8. The focal depth of the main shock is 8 to 15 km. As the active in the focus adopted the sloping plane, plunging to the North - North-East direction. Type progress on such a plane - thrust with component of right-lateral strike-slip. Seismodislocationswere of secondary gravitational nature. The results of paleoseismological studies conducted in the Eastern part of the epicentral area of the Racha earthquake, showed that this seismic source the strong seismic shocks happened before. According to the obtained data, the age of the previous strong earthquake in the Racha - Dzhava zone (i.e., before 1991) - about 2000 years ago. Another, more ancient event occurred about 6,000 years ago. The recurrence period of strong earthquakes, similar to the disaster of 1991, thus, is an average of 2000-3000 years.