Trenching Study on the Taranay Fault in South Sakhalin, Far Eastern Russia

Abstract

Scarplets and east-dipping steep slopes, both of which form a marked lineament N20°E in direction and 16 km in length, develop on the Pleistocene fluvial surfaces along the geomorphic boundary between the Yuzhno-Kamyshovvy Mts. and the Susunayskaya Lowland in South Sakhalin. These landforms have been created by Quaternary activities of the Taranay fault. Our recent trenching surveys in Taranay (46° 39' N, 142° 24' E) revealed west-dipping thrusts truncating a fluvial gravel layer. Flexure of the fluvial gravel layer with >2 m vertical displacement was also identified. The latest event took place in the period between 42 and 0.1 ka. An average slip rate is estimated geomorphologically to be 0.05 to 0.08 m/ky, or faster. Whereas the Taranay fault can be regarded as a C-class active fault, further investigations to discover the main fault and to obtain other kinds of fault parameter are required.