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

摘要： 根据详实的野外资料对新疆阜康-吉木萨尔断裂带的构造几何特征和活动性进行了分析与研究,结果表明:断裂带由东、西两大段组成,西段由4条次级S倾逆断裂左行斜列组成,东段由3条次级S倾逆断裂右行斜列组成,总体上呈向北微凸的近EW向展布,长达140km,控制着东天山北缘的第四纪构造演化和地貌发育;组成断裂往往是低角度的逆断层,与褶皱共生,切割深度5～6km,第四纪晚期多期(次)活动,以间歇性稳定滑动为特征;断裂带端部段落倾角较大,活动量较小,全新世平均垂直滑动速率为0.10～0.40mm/a,中部段落以低倾角的推覆为特征,活动强烈,全新世平均垂直滑动速率达0.80～1.00mm/a以上。

关键词: 断裂带, 几何特征, 活动性, 新疆, 阜康-吉木萨尔