SEISMOLOGY AND GEOLOGY ›› 2007, Vol. 29 ›› Issue (2): 201-217.

• Brief Report • Previous Articles     Next Articles

NEAR-SURFACE CHARACTER OF PERMANENT GEOLOGIC DEFORMATION ACROSS THE MEGA-STRIKE-SLIP FAULTS IN THE NORTHERN TIBETAN PLATEAU

XU Xi-wei1, YU Gui-hua1, CHEN Gui-hua1, LI Chen-xia1, ZHANG Lan-feng1, Yann Klinger2, Paul Tapponnier2, LIU Jing3   

  1. 1. Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    2. Institut de Physique du Globe, 75005 Paris, France;
    3. Institute of Tibet Plateau Research, Chinese Academy of Sciences, Beijing 100085, China
  • Received:2007-05-09 Revised:2007-06-07 Online:2007-06-09 Published:2009-08-27

青藏高原北部大型走滑断裂带近地表地质变形带特征分析

徐锡伟1, 于贵华1, 陈桂华1, 李陈侠1, 张兰凤1, Yann Klinger2, Paul Tapponnier2, 刘静3   

  1. 1. 中国地震局地质研究所,北京 100029;
    2. Institut de Physique du Globe, 75005 Paris, France;
    3. 中国科学院青藏高原研究所,北京 100085
  • 作者简介:徐锡伟,男,1962年生,1983年毕业于成都地质学院放射性矿产地质专业,1989年毕业于中国科技大学研究生院(国家地震局地质研究所),获博士学位,现主要从事活动构造学及其在减轻地震灾害中的应用研究,电话:010-62009025,E-mail:xiweixu@vip.sina.com.
  • 基金资助:
    国家发展与改革委员会发改投资"城市活断层试验探测"项目(20041138)资助

Abstract: The Altyn Tagh,Kunlun and Haiyuan Faults are three major left-lateral strike-slip faults with high geologic and GPS-derived horizontal slip rates as well as frequent surface-rupturing earthquakes in the northern Tibetan Plateau.There exist local structures,such as pull-apart basins in stepovers and sag ponds,where fine-grained and/or organic interfaulting sediments have been continuously filled and co-seismic faulting traces have been well preserved in those sediments.Trenching across the strike-slip faults and those local structures,stratum-logging of the trench walls and structural-stratigraphic examination can uncover basic features of the permanent and cumulative geologic deformation zone of a strike-slip fault that has experienced several surface-rupturing earthquake cycles.The geologic section of the Banguoba trench 9km east of Old A'kesai Town across the recent traces of the Altyn Tagh Fault records 7 paleoearthquake events with a co-seismic left-lateral slip of 7±1m for the latest event and its cumulative geologic deformation zone is only 8m in width.The geologic section of the western Old A'kesai trench across a pull-apart basin of the Altyn Tagh Fault records at least 4 paleoearthquake events and its permanent and cumulative geologic deformation zone is only 13m in width.The geologic section of the Xidatan trench across the Kunlun Fault reveals 5 paleoearthquake events and their cumulative geologic deformation zones are 12~13m in width.The Maqin trench across a pull-apart of the Kunlun Fault also reveals 5 paleo-earthquake events and most of the structural deformation,about 15m wide,is concentrated in the pull-apart,while the widest structural deformation,including the associated distortion nearby the boundary fault of the pull-apart,is less than 35m.Two trenches excavated across the southern and northern boundary faults of the Songshan pull-apart basin along the Maomaoshan-Laohuashan segment of the Haiyuan Fault show up 6 paleoevents and their permanent geologic deformation zones are less than 10m wide for single boundary fault.Of course,as a extensional jog,the pull-apart basin over a hundred meters wide will experience severe tensional and transtensional surface ruptures during an earthquake,and the pull-apart basin itself may be taken as one part of the permanent geologic deformation zone.Thus,the repeatedly faulting of the Altyn Tagh,Kunlun,and Haiyuan Faults during the past several surface-rupturing earthquake cycles is localized along their strike and the width of their permanent geologic deformation zone for a single strike-slip fault is over 10 meters,but less than 30 meters in general.

Key words: Geologic deformation zone, strike-slip fault, Altyn Tagh Fault, Kunlun Fault, Haiyuan Fault, Qinghai-Tibetan Plateau

摘要: 阿尔金断裂带、东昆仑断裂带和海原断裂带是青藏高原北部的大型左旋走滑断裂带,具有相对高的地质和GPS滑动速率,地表破裂型地震频发。在阿尔金断裂带阿克塞老城西和半果巴、东昆仑断裂带西大滩和玛沁、海原断裂带松山等地点的探槽地质剖面揭露了这些走滑断裂带累积地质变形带的基本特征。阿尔金断裂带半果巴探槽和阿克塞老城西探槽、东昆仑断裂带西大滩探槽和玛沁探槽揭露出的地质变形带宽度约12m左右;海原断裂带松山拉分盆地边界单条走滑断层地质变形带宽度不足10m,考虑到地震期间拉分盆地可能会出现较严重的变形,则拉分盆地本身也应作为强变形带处理。由此可见,经历过多个地震地表破裂循环的东昆仑断裂带、海原断裂带和阿尔金断裂带其地质变形带的宽度是有限的,具有变形局部化特征。单条走滑断层的地质变形带宽度一般为10余米,比较保守地估计应<30m,走滑断层斜列阶区的地质变形带宽度取决于阶区本身的宽度。

关键词: 地质变形带, 走滑断层, 阿尔金断裂带, 东昆仑断裂带, 海原断裂带, 青藏高原

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