北天山东段阜康断裂吉木萨尔段古地震事件研究

Research on Paleoearthquake Events of the Jimusaer Segment of the Fukang Fault Belt,in Xinjiang

阜康断裂带是北天山东段博格达弧形推覆构造一条重要的地质地貌构造分界线,吉木萨尔段位于阜康断裂带最东部,晚第四纪以来断裂活动性明显,地表形成一系列的地质地貌现象。通过在吉木萨尔段开展详细的地质地貌调查、断裂陡坎测量以及探槽剖面分析等工作,从探槽发现8次古地震事件,由老到新发生年代分别为:E1(257±24~376±22)ka B.P.;E2(2271±193~257±24)ka B.P.;E3(155±04~227±09)ka B.P.;E4(133±04~1359±116)ka B.P.;E5(87±05~133±04)ka B.P.;E6(65±15~675±057)ka B.P.;E7(20±10~35±08)ka B.P.;E8(?~20±10)ka B.P.。最新一次古地震为距今约(20±10)ka,古地震事件复发周期为(24-745)ka。吉木萨尔东南探槽有两条平行断层陡坎F1-7-1及F1-7-2。根据测年结果显示:最新活动时代分别为(87±05)ka和(20±10)ka,F_(1-7-1)早于F_(1-7-2)形成。

Fukang fault zone in Xinjiang is one of the most important geological-landscape boundaries of the Bogeda nappe tectonics in the east rim of North Tianshan Mountain. Jimusar Segment as the eastest part of Fukang fault zone, has had very obvious activities since late Quaternary, generating a series of apparent geomorphic traces on the surface. In this paper, the Late- Quaternary characteristics of Jimusar Segment were studied by geology investigation, fracture deformation measurement and large exploratory trench profile analysis. The trench exposes 8 paleoearthquake events. The occurrence time of 8 events were about E1 （25.7 ± 2.4 ~ 37.6 ± 2. 2 ） ka B. P. ; E2 （ 22.71 ± 1.93 ~25.7 ±2.4）ka B. P. ;E3（15.5 ±0.4 -22. 7 ±0. 9）ka B. P. ;E4（13.3 ±0.4 - 13.59 ± 1.16）ka B. P. ;E5（8. 7 ± 0.5 -13.3 ±0.4）ka B.P. ;FA（6. 5 ±1.5 -6.75 ±0. 57）ka B.P. ;E7（2.0 ±1.0 -3.5 ±0. 8）ka B.P. ;E8（？ - 2.0 ± 1. 0）ka B. P. The latest Paleo earthquake is about （2.0 ± 1. 0） ka and the recurrence cycle of these events were about（2.4 -7.45）ka. There are two parallel fault sacrps, F1-7-1 and F1-7-2, in the Southeast Jimusaer trench. According to the dating results, the latest activity periods of F1-7-1 was （8. 7 ± 0. 5 ）ka B.P. and the latest activity periods of F1-7-2was （2.0 ± 1. 0）ka B.P. So the fault saerp F1-7-1 was formed early than the fault sacrps F1-7-2.