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青藏高原东缘新构造及其对汶川地震的控制作用
引用本文:张岳桥,杨农,施炜,董树文.青藏高原东缘新构造及其对汶川地震的控制作用[J].地质学报,2008,82(12):1668-1678.
作者姓名:张岳桥  杨农  施炜  董树文
作者单位:1. 国土资源部新构造运动与地质灾害重点实验室,北京,100081;中国地质科学院地质力学研究所,北京,100081
2. 中国地质科学院,北京,100037
基金项目:国家重点基础研究发展计划“973”项目(编号2008CB425702)和中国地质调查局地质调查项目(编号1212010670104)联合资助成果
摘    要:基于卫星遥感图像解译、地形起伏度分析和地面调查资料,论述了青藏高原东缘构造地貌格局、新构造演化阶段和活动断裂特征,提出青藏高原东缘不同地块在晚新生代时期有序的向东挤出过程,并划分为4个阶段:中新世早期川滇地块向北东挤出、中新世晚期川滇地块的再次强烈向东挤出、上新世至早中更新世时期川青地块的向东挤出、晚更新世以来最新构造变动阶段,青藏高原东缘地貌边界带也经历了由西向东、由南向北的有规律的迁移过程。基于活动构造的最新研究成果和现今GPS测量成果,阐述了东昆仑岷山龙门山走滑逆冲断裂系统的运动学特征。根据地震破裂构造的实地调查,分析了汶川地震的地表破裂行为,提出了汶川地震的发震构造模型。研究认为,青藏高原东部地区NW向楔状条块向东运动速度的一半被鲜水河断裂及其北西延伸的构造带所吸收,而龙门山构造带向东运动受阻于四川盆地之下扬子刚性地块,使得龙门山断裂带处在低应变、高应力环境下,因长期应力应变累积而导致向西陡倾的断裂带突然向东逆冲运动而释放能量。汶川强震发生的深部机理值得深入研究。

关 键 词:青藏高原东缘  构造地貌格局  新构造  龙门山断裂  汶川地震
收稿时间:2008/10/28 0:00:00
修稿时间:2008/11/12 0:00:00

Neotectonics of Eastern Tibet and Its Control on the Wenchuan Earthquake
ZHANG Yueqiao,YANG Nong,SHI Wei and DONG Shuwen.Neotectonics of Eastern Tibet and Its Control on the Wenchuan Earthquake[J].Acta Geologica Sinica,2008,82(12):1668-1678.
Authors:ZHANG Yueqiao  YANG Nong  SHI Wei and DONG Shuwen
Institution:Key Laboratory of Neotectonic Movement & Geohazard, Ministry of Land and Resources, Beijing, 100081; Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijijng, 100081;Key Laboratory of Neotectonic Movement & Geohazard, Ministry of Land and Resources, Beijing, 100081; Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijijng, 100081;Key Laboratory of Neotectonic Movement & Geohazard, Ministry of Land and Resources, Beijing, 100081; Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijijng, 100081;Chinese Academy of Geological Sciences, Beijijng, 100037
Abstract:Based on satellite imagery interpretation, land relief amplitude analysis, and field observations, this paper discusses the tectono-morphologic background, neotectonics evolution history and active fault characteristics of eastern Tibet. It is proposed that different blocks in the eastern margin of Tibet-Qinghai Plateau successively extruded eastward during later Cenozoic and the extrusion can be divided into four stages: extrusion of the Chuan-Dian block eastward in early Miocene; intense extrusion of the Chuan-Dian block eastward again in late Miocene; eastward extrusion of the Qing-Chuan block from early Pliocene to early-middle Pleistocene; and tectonic change stage since late Pleistocene to Holocene. Accordingly, morphological boundary of east Tibet underwent change from west to east and from south to north. Latest research results on the active faults and GPS measurements display the kinematic features of East Kunlun-Mingshan-Longmen Mountain strike-slip system. Based on the field survey of earthquake rupture, combined with analysis of ground rupture features in the Wenchuan area, the study proposes a model for seismogenic structure of the Wenchuan earthquake. This study also indicates that almost half speed of movement of an NW-trending wedge-like block toward east was absorbed by the Xianshuihe fault and its westward extension structure. However, the motion of Longmenshan structural belt toward east was likely stopped by the rigid block beneath the Yangtze plate, resulting in that the Longmenshan rapture occurred in a setting of low strain and high stress; thus long-term strain-stress accumulation triggered energy releasing by abrupt thrusting of the steeply west dipping rapture eastward. Therefore, the focal mechanism for the Wenchuan catastrophic earthquake is worth further studying.
Keywords:East Tibet  tectono-morphology  Neotectonics  Longmenshan faults  Wenchuan earthquake
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