Decomposition and Evolution of Intracontinental Strike‐Slip Faults in Eastern Tibetan Plateau
Decomposition and Evolution of Intracontinental Strike‐Slip Faults in Eastern Tibetan Plateau
复制标题
DOI：
10.1111/1755-6724.12052
复制
发表时间：
2013-04
期刊：
影响因子：
--
通讯作者：
Yao Qi;Xu Xiwei;Xing Hui-Lin;Xu Chong;Wang Xiaohui
中科院分区：
文献类型：
--
作者：
Yao Qi;Xu Xiwei;Xing Hui-Lin;Xu Chong;Wang Xiaohui
青藏高原的陆内走滑断层很少受到关注。自2003年利用GPS重测数据发现龙日坝断层以来，这条被忽视的断层越来越受到人们的关注。局部地形和横向条带剖面表明，龙日巴断裂是青藏高原高缓断层与造山带高陡断层的分界线。此外，GPS数据显示，龙日巴断裂是巴彦哈尔地块迁移方向由东向向东南转换的分界线。GPS数据显示，龙日坝断裂是巴彦哈尔东块各子块的边界断裂。建立了以龙日坝断裂和龙门山断裂中段为主体，横跨巴彦哈尔块和四川盆地的三维模型。采用非线性有限元方法模拟了青藏高原东部断裂活动和块体变形。结果表明，低阻低速层起着拆离层的作用，使上覆块体向东南方向移动。滑脱层还控制了刚性巴彦哈尔地块的垂直和水平变形，并导致龙门山逆冲断层所在层缘的应变积累。当龙门山断层上积累了足够的应变后，就会发生大地震，比如2008年的汶川地震。位于低阻低速层之上的龙日巴断裂的走滑活动，对巴彦哈尔块体的横向位移进行了分割，调整了巴彦哈尔块体的运动方向，使其由西向东移的阿巴子块体向东向东南移动的龙门山子块体运动。构建了龙日坝断层不同深度的四个模型：（1）深度仅为4 km的浅断层，（2）深度为龙门山断层一半的深断层，（3）比低阻低速层浅2 km的深断层，（4）与低阻低速层一样深的断层。研究表明，龙日坝断裂在该构造体系下不同发育阶段的活动性及其影响：在一个地震复发期内，断裂破裂范围随断裂深度的增加而增大，断裂对侧向滑动的分隔也随断裂深度的变化而变化。龙日坝断裂是沿着这一构造背景在晚新生代快速隆升后，由北西向南东逐渐展布的新生断裂。计算结果给出了青藏高原东缘陆内走滑断层和主要边界逆冲断层的块体变形特征和断层行为。虽然低阻低速层控制了巴彦哈尔地块的变形和龙门山逆冲断层的隆升，但龙日巴断裂的分割对板内变形和现代地貌演化具有重要影响。
Little attention had been paid to the intracontinental strike‐slip faults of the Tibetan Plateau. Since the discovery of the Longriba fault using re‐measured GPS data in 2003, an increasing amount of attention has been paid to this neglected fault. The local relief and transverse swath profile show that the Longriba fault is the boundary line that separates the high and flat tomography of the Tibet plateau from the high and precipitous tomography of Orogen. In addition, GPS data shows that the Longriba fault is the boundary line where the migratory direction of the Bayan Har block changed from eastward to southeastward. The GPS data shows that the Longriba fault is the boundary fault of the sub‐blocks of the eastern Bayan Har block We built three‐dimensional models containing the Longriba fault and the middle segment of the Longmenshan fault, across the Bayan Har block and the Sichuan Basin. A nonlinear finite element method was used to simulate the fault behavior and the block deformation of the Eastern Tibetan Plateau. The results show that the low resistivity and low velocity layer acts as a detachment layer, which causes the overlying blocks to move southeastward. The detachment layer also controls the vertical and horizontal deformation of the rigid Bayan Har block and leads to accumulation strain on the edge of the layer where the Longmenshan thrust is located. After a sufficient amount of strain has been accumulated on the Longmenshan fault, a large earthquake occurs, such as the 2008 Wenchuan earthquake. The strike slip activity of the Longriba fault, which is above the low resistivity and low velocity layer, partitions the lateral displacements of the Bayan Har block and adjusts the direction of motion of the Bayan Har block, from the eastward moving Ahba sub‐block in the west to southeastward moving Longmenshan sub‐block in the east. Four models with different depths to the Longriba fault were constructed: (1) a shallow fault with a depth of only 4 km, (2) a deeper fault that is half as deep as the Longmenshan fault, (3) a deep fault that is 2 km shallower than the low resistivity and low velocity layer, and (4) a fault that is as deep as the low resistivity and low velocity layer. The activity and influence of the Longriba fault with different development stage under this tectonic system were shown: in one Earthquake recurrence period, the rupture region of the fault increases with the depth of the fault, and the lateral slip partition by the fault also changes with the fault depth. It suggests that the Longriba fault is a newly generated fault that developed after the quick uplift in Late Cenozoic along this tectonic setting and gradually extended from the northwest to southeast. The calculations provide the characteristic of block deformation and fault behaviors of intra‐continental strike‐slip fault and major boundary thrust faults in the eastern margin of the Tibet plateau. Although the low resistivity and low velocity layer controls the deformation of the Bayan Har block and the uplift of the Longmenshan thrust, the partition of the Longriba fault has an important influence on the intra‐plate deformation and modern geomorphic evolution.