Palaeoseismological and archaeoseismological studies in the Kurai fault zone, along which the Kurai Range is thrust onto Cenozoic deposits of the Chuya intramontane basin, led to the identification of a long reverse fault scarp 8.0 m high. The scarp segments are primary seismic deformations of large ancient earthquakes. The scarp's morphology, results of trenching investigations, and deformations of Neogene deposits indicate a thrusting of the piedmont plain onto the Kurai Range, which is unique for the Gorny Altai. Similarly for Northern Tien Shan, we explain this by the formation of both a thrust transporting the mountain range onto the depression and a branching thrust dislocation that forms the detected fault scarp. In a trench made in one of the scarp segments, we identified the parameters of the seismogenic fault-a thrust with a 30° dipping plane. The reconstructed displacement along the fault plane is 4.8 m and the vertical displacement is 2.4 m, which indicates a 7.2-7.6 magnitude of the ancient earthquake. The 14C age of the humus-rich loamy sand from the lower part of the colluvial wedge constrains the age of the earthquake at 3403-3059 years BP.
