【摘要】 新疆博格达山北缘阜康南断裂带古牧地断裂段是发育在古牧地背斜北翼的逆冲断裂,由南倾的主干断裂和南侧的反冲断裂组成,晚第四纪以来断裂新活动性明显,地表形成一系列的地质地貌现象。文章在大红沟附近通过变形阶地测量、探槽开挖和热释光(TL)年代测定,获得古牧地断裂晚更新世末期以来的平均垂直滑动速率为0.27mm/a左右,全新世以来的平均垂直滑动速率为0.13～0.18mm/a,速率明显变小。古地震研究表明,古牧地断裂晚第四纪以来有过多次活动,最新一次古地震事件的垂直错距在1.4m左右,离逝时间已达8ka以上。古牧地断裂全新世以来的运动速率偏低,很可能意味着该断裂需要一次强震来释放存储的弹性应变,表明古牧地断裂具有很大的地震危险性。更多还原

【Abstract】 The Gumudi fault is located on the northwest margin of the Bogda arcuate nappe structure and is a westward ending part of the South Fukang fault belt. It is about 15km long,comprising a main fault dipping to the south and a secondary recoil fault dipping to the north. The fault has had very obvious activities since late Quaternary, generating a series of apparent geomorphic traces on the surface. In this paper, its Late-Quaternary deformaion characteristics were studied by detailed analyses of offset terraces and deformed alluvial fans and by thermoluminescence dating. Displacements of river terraces and alluvial fans widely occurred along the Gumudi fault segment. At Dahonggou,the second-level terrace was offset across the fault,with a vertical distance of 6m, but the first-level terrace is very flat without any deformation. However, the sandy gravel at the bottom of the first-level terrace was dislocated about 1.4m. According to the vertical offsets and related TL dating results, the average vertical slip rate of the Gumudi fault was calculated to be about 0.27mm/a since Late Pleistocene and 0.13～0. 18mm/a since Holocene. It is obvious that the slip rate of the fault since Holocene is smaller than that since Pleistocene. According to studies of paleoearthquakes,the vertical displacement caused by the last paleoearthquake along the Gumudi fault was about 1.4m and the elapsed time was more than 8ka. If the fault once initiated a strong earthquake with a vertical displacement of about 1.5m in the short term, its slip rate since Holocene will be close to that since Late Pleistocene. The low slip rate since Holocene is likely to mean that the fault would need a strong earthquake to release the stored elastic strain. Therefore,it is suggested that the Gumudi fault would have great seismic hazard.更多还原