Talas-Fergana Fault

a large tectonic fracture of the earth’s crust that crosses the Tien-Shan. The fault is more than 800 km long, running along the Fergana, Talas, and Karatau ranges. The displacement is vertical.

The Talas-Fergana fault appeared at the end of the epoch of Hercynian orogenesis. In the Permian and Triassic periods the western wall of the fault was shifted more than 100 km northwestward relative to the eastern side (right fault). In the Jurassic period, grabens were formed along certain segments of the fault, and terrigenous and coal-bearing deposits accumulated in them. Movement on the Talas-Fergana fault continued at later times. The total horizontal displacement from the Late Paleozoic to the Holocene period reached 180 km (if plastic deformation of the walls of the fault is taken into consideration, 250 km), whereas the vertical displacements were several kilometers. In more recent times, a horizontal shift of 30–50 m in stream channels and other modern morphostructures has occurred along the fault. The fault zone is seismic; earthquake foci reach depths of 50 km.