SEISMOLOGY AND GEOLOGY ›› 2016, Vol. 38 ›› Issue (4): 897-910.DOI: 10.3969/j.issn.0253-4967.2016.04.008

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THE SLIP RATE AND PALEOEARTHQUAKES OF THE YUMEN FAULT IN THE NORTHERN QILIAN MOUNTAINS SINCE THE LATE PLEISTOCENE

LI An, WANG Xiao-xian, ZHANG Shi-min, CHEN Zhi-dan, LIU Rui, ZHAO Jun-xiang, LÜ Yan-wu   

  1. The Key Laboratory of Crustal Dynamics, the Institute of Crustal Dynamics, China Earthquake Adiministration, Beijing 100085, China
  • Received:2015-11-11 Revised:2016-03-02 Online:2016-12-20 Published:2017-01-20

祁连山北缘玉门断裂晚更新世以来的活动速率及古地震

李安, 王晓先, 张世民, 陈志丹, 刘睿, 赵俊香, 吕延武   

  1. 中国地震局地壳应力研究所, 地壳动力学重点实验室, 北京 100085
  • 作者简介:李安,男,1983年生,2013年于中国地震局地质研究所获构造地质学博士学位,助理研究员,研究方向为活动构造与古地震、构造地貌研究,电话:010-62846731,E-mail:antares_lee@163.com。
  • 基金资助:

    中国地震局地壳应力研究所基本科研业务专项(ZDJ2014-12);国家青年科学基金(41402185)与中国地震活断层探察:南北地震带北段项目(201408023)共同资助

Abstract:

The Yumen Fault lies on the west segment of the north Qilian Fault belt and adjacent to the Altyn-Tagh Fault,in the north margin of the Tibet Plateau.The tectonic location of the Yumen fault is special,and the fault is the evidence of recent activity of the northward growth of Tibetan plateau.In recent twenty years,many researches show the activity of the Yumen Fault became stronger from the early Pleistocene to the Holocene.Because the Yumen Fault is a new active fault and fold belt in the Qilian orogenic belt in the north margin of the Tibet Plateau,it is important to ascertain its slip rate and the recurrence interval of paleoearthquakes since the Late Pleistocene.Using the satellite image interpretation of the Beida river terrace,the GPS measurement of alluvial fans in front of the Yumen Fault and the trench excavation on the fault scarps,two conclusions are obtained in this paper.(1) The vertical slip rate of the Yumen Fault is about 0.41~0.48mm/a in the Holocene and about 0.24~0.30mm/a in the last stage of the late Pleistocene.(2) Since the Holocene epoch,four paleoearthquakes,which happened respectively in 6.12~10.53ka,3.6~5.38ka,1.64~1.93ka and 0.63~1.64ka,ruptured the surface scarps of the Yumen Fault.Overall,the recurrence interval of the paleoseismic events shortens gradually and the activity of the Yumen Fault becomes stronger since the Holocene.Anther characteristic is that every paleoearthquake probably ruptured multiple fault scarps at the same time.

Key words: Qilian Mountains, Yumen Fault, slip rate, paleoearthquake

摘要:

玉门断裂位于青藏高原东北缘的祁连山造山带西段,与阿尔金断裂相邻,构造位置特殊,是青藏高原北缘向外扩展的最新活动证据。近20a越来越多的研究使得对其认识逐渐从弱活动向强活动转变。因此,玉门断裂作为1条青藏高原北缘祁连山造山带中新生的活动断裂和褶皱带,确定它晚更新世至全新世的活动性和古地震复发周期具有重要的意义。文中通过对玉门断裂山前冲积扇面和北大河阶地的影像解译与断层陡坎的测量,以及对2条不同断层陡坎的探槽开挖工作,获得了以下几点认识:1)玉门断裂全新世以来的垂直活动速率为0.41~0.48mm/a,晚更新世晚期以来的垂直活动速率为0.24~0.30mm/a。2)玉门断裂全新世以来共发生4次古地震事件,这4次古地震分别发生在6.12~10.53ka BP、3.6~5.38ka BP、1.64~1.93ka BP和0.63~1.64ka BP。总体上表现出复发间隔逐渐缩短,活动性增强的趋势,并且每次古地震都可能造成多支断层同时破裂,形成陡坎。

关键词: 祁连山, 玉门断裂, 活动速率, 古地震

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