Structural analysis of the right-lateral strike-slip Qingchuan fault, northeastern segment of the Longmen Shan thrust belt, central China
Structural analysis of the right-lateral strike-slip Qingchuan fault, northeastern segment of the Longmen Shan thrust belt, central China
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DOI：
10.1016/j.jsg.2014.09.014
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发表时间：
2014-11
影响因子：
3.1
通讯作者：
A. Lin;G. Rao;B. Yan
中科院分区：
文献类型：
--
作者：
A. Lin;G. Rao;B. Yan
龙门山冲断带是青藏高原东缘的一个重要构造带，主要发育逆冲断层和与逆冲断层相关的褶皱构造，是2008年汶川7.9级逆冲型地震的发生地。虽然以往的研究表明，这次地震的发震断层改变了同震滑动方向，由断层中部和东南段的逆冲为主的滑动变为沿青川断层（断层东北段）的右行走滑为主的沿着位移，但青川断层的相关构造和现今活动性仍不清楚。通过对0.5 m分辨率WorldView影像和数字高程模型（DEM）数据的地形分析、野外调查和断裂带构造分析，发现：（1）河道、晚更新世-全新世阶地、冲积扇沿青川断裂系统性地沿着右移，（2）断裂带面理发育，表现出以右行走滑为主的位移;地质证据和地震资料表明，青川断裂是现今活动的主发震断裂，以右行走滑为主，平均滑动速率约为1.5 km。3-5毫米/年研究结果表明，沿沿着大西向断层的滑动方向从中部和西南部的逆冲断层为主到东北部的右旋走滑断层为主的空间变化，主要是由于沿沿着大西向断层的几何方位从NE-SW向ENE-WSW向变化所致。
The eastern margin of the Tibetan Plateau is marked by the Longmen Shan thrust belt (LSTB), which is dominated by thrust faults and thrust-related fold structures that is home to the 2008Mw7.9 thrusting-type Wenchuan earthquake. Although previous works demonstrated that the seismogenic fault for the earthquake changed coseismic slip sense from thrust-dominated slip in the central and southeastern segments of the LSTB to right-lateral strike-slip-dominated displacement along the Qingchuan fault (northeastern segment of the LSTB), the related structures and current activity of the Qingchuan fault remains unclear. Topographic analyses of 0.5-m-resolution WorldView imagery and Digital Elevation Model (DEM) data, field investigations and structural analysis of the fault zone reveal that: i) stream channels and late Pleistocene–Holocene terrace risers and alluvial fans are systematically offset dextrally along the Qingchuan fault; ii) foliations developed in the fault zone indicate a right-lateral strike-slip-dominated displacement; and iii) geological evidence and seismic data show that the Qingchuan fault is currently active as the main seismogenic fault dominated by a right-lateral strike-slip with an average slip rate of ca. 3–5 mm/yr. Our results demonstrate that the spatial change in slip sense along the LSTB from thrust-dominated in the central and southwestern sectors to right-lateral strike-slip-dominated in the northeastern sector is mainly caused by a change in the orientation of fault geometry from NE–SW to ENE-WSW along the LSTB.