Active Faulting Pattern, Present‐day Tectonic Stress Field and Block Kinematics in the East Tibetan Plateau
Active Faulting Pattern, Present‐day Tectonic Stress Field and Block Kinematics in the East Tibetan Plateau
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DOI：
10.1111/j.1755-6724.2009.00093.x
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发表时间：
2009-08
期刊：
影响因子：
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通讯作者：
Yueqiao Zhang;S. Dong;Nong Yang
中科院分区：
文献类型：
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作者：
Yueqiao Zhang;S. Dong;Nong Yang
本文通过综合现有文献资料，研究了青藏高原东部主要活动断裂和现今构造应力场，并提出了该地区的块体运动学模型。结果表明，青藏高原东部主要为走滑和逆断层应力状态，最大水平应力与现今速度场基本一致，但西秦岭与主要走滑断层走向平行。青藏高原东部活动构造以三大断裂系统为特征。昆仑-秦岭左旋走滑断裂系统由东昆仑断裂带、沿着岷山山脉的左旋斜向逆断层和两条切割西秦岭山脉的NEE向大断层组成，可容纳川青地块以10-14 mm/a的速率向东运动。鲜水河断裂带的左行活动适应了川滇地块的顺时针旋转。龙门山逆冲断裂系形成于青藏高原东缘，并向四川盆地西南部扩展。龙门山山脉的地壳缩短量似乎较低（2-4 mm/a），仅吸收了川青地块向东运动的一小部分。大部分的东向运动已经传递到华南，华南正以7-9 mm/a的速度向东南方向移动。地球物理资料解释表明，青藏高原东部地壳和岩石圈具有明显的增厚和流变分层特征。上地壳与下地壳通过一条15-20 km深的滑脱带分离，该滑脱带涉及龙门山断裂带，并向东扩展至四川盆地西南部。汶川地震正是在这个滑脱系统的分叉点上形成的。在龙门山断裂带之下，青藏高原东部下地壳与扬子地块岩石圈地幔并置的部位，应存在一个流变边界。
This paper examines major active faults and the present‐day tectonic stress field in the East Tibetan Plateau by integrating available data from published literature and proposes a block kinematics model of the region. It shows that the East Tibetan Plateau is dominated by strike‐slip and reverse faulting stress regimes and that the maximum horizontal stress is roughly consistent with the contemporary velocity field, except for the west Qinling range where it parallels the striking of the major strike‐slip faults. Active tectonics in the East Tibetan Plateau is characterized by three faulting systems. The left‐slip Kunlun‐Qinling faulting system combines the east Kunlun fault zone, sinistral oblique reverse faults along the Minshan range and two major NEE‐striking faults cutting the west Qinling range, which accommodates eastward motion, at 10–14 mm/a, of the Chuan‐Qing block. The left‐slip Xianshuihe faulting system accommodated clockwise rotation of the Chuan‐Dian block. The Longmenshan thrust faulting system forms the eastern margin of the East Tibetan Plateau and has been propagated to the SW of the Sichuan basin. Crustal shortening across the Longmenshan range seems low (2–4 mm/a) and absorbed only a small part of the eastward motion of the Chuan‐Qing block. Most of this eastward motion has been transmitted to South China, which is moving SEE‐ward at 7–9 mm/a. It is suggested from geophysical data interpretation that the crust and lithosphere of the East Tibetan Plateau is considerably thickened and rheologically layered. The upper crust seems to be decoupled from the lower crust through a décollement zone at a depth of 15–20 km, which involved the Longmenshan fault belt and propagated eastward to the SW of the Sichuan basin. The Wenchuan earthquake was just formed at the bifurcated point of this décollement system. A rheological boundary should exist beneath the Longmenshan fault belt where the lower crust of the East Tibetan Plateau and the lithospheric mantle of the Yangze block are juxtaposed.