Morphostructure and faulting in the source area of the April 29, 1991, Racha, Georgia earthquake

The main morphostructural features of the Kazbek, Greater Caucasus area and the adjacent eastern part of the Central Caucasus are analyzed in order to gain insights into the morphostructural position of the Racha earthquake s ource area. The comparison of focal mechanisms of 56 aftershocks with the f ault-block morphostructure of this area revealed different styles of block movements. On the basis of the wave pattern and a new approach to the inter pretation of seismograms, a complicated faulting process in the Racha earth quake source is shown. The space-time analysis of the aftershock process is performed.