关键词: 断裂带, 几何特征, 活动性, 新疆, 阜康-吉木萨尔

Abstract: Based on detailed field investigations, this paper describes geometrical characteristics and tectonic activities of the Fukang-Jimsar Fault zone in eastern Tianshan, Xinjiang, China. This fault zone strikes nearly in east-west, dipping to south, and extends over a length of 140km. It is a major geological/geomorphological margin controlling the neotectonic movement in this region. On the southern side of the Fukang-Jimsar Fault develop Mesozoic strata, forming low mountains and hills; the northern side of the fault corresponds to a large Quaternary depression plain. The Fukang-Jimsar Fault consists of 7 segments of secondary gently dipping reverse faults with lengths of 12～24km, i.e. the Ganquanpu, Sangonghe, Sigonghe, Ganhezi, Quanquanzi, Dalongkou and Dongfeng Muchang Faults. In seismic profiles these faults make up an anticline thrust structure in the range of 5～6km depth, having dip angles of 20°～30° at the lower part and 40°～50° at the upper part(sometimes nearly 60°～80° at the ground). All these fault segments display the evidence of late Quaternary activities such as fault scarps, offset terraces and young sedimentary deposits etc. The steep dipping distal segments of the fault experienced 7 times of activities in Holocene (with an occurrence interval of 1,500yr), and have relatively small vertical slip-rate (0.10～0.40mm/yr); while the gently dipping middle segments are characterized mainly by strong thrusting, and have relatively high vertical slip-rate in Holocene (0.40～1.43mm/yr).

Key words: fault zone, structural geometry, tectonic activities, Xinjiang, Fukang-Jimsar Fault