Strain and rotation rate from GPS in Tibet, Anatolia, and the Altiplano
Strain and rotation rate from GPS in Tibet, Anatolia, and the Altiplano
复制标题
DOI：
10.1029/2006tc002030
复制
发表时间：
2007-06
期刊：
影响因子：
4.2
通讯作者：
R. Allmendinger;R. Reilinger;J. Loveless
中科院分区：
文献类型：
--
作者：
R. Allmendinger;R. Reilinger;J. Loveless
大陆高原地区由区域GPS网络测量到的变形反映了高原的地质和构造变化。对于两个碰撞型高原（青藏高原和安纳托利亚高原）以及一个非碰撞型高原（阿尔蒂普拉诺高原），我们通过反演GPS速度来计算完整的二维速度梯度张量，从而分析区域应变和旋转速率。为了测试该方法，我们使用根据地中海东部/中东地区的弹性块体模型确定的网格化速度，并表明在一阶近似下，直接由GPS矢量计算得到的变形能够准确描述区域变形模式。主缩短和伸展速率轴、垂直轴旋转以及二维（2 - D）体应变（膨胀）与大面积的长期地质特征非常吻合，这表明GPS速度场反映了导致高原近期地质演化的过程。地质描述和GPS描述的变形之间的差异可归因于GPS网络过于稀疏而无法捕捉局部震间变形，或者是强烈地震期间产生的永久变形。阿尔蒂普拉诺高原内部的缩短量比其他两个高原更大，且各处的二维膨胀均为负值。垂直轴旋转在地形对称轴两侧符号改变，这是由于整个高原的分布式变形所致。相比之下，碰撞型高原存在大片准刚体旋转区域，这些区域由走滑断层界定，走滑断层的旋转方向与旋转块体相反。青藏高原和安纳托利亚高原互为镜像；两者在旋转块体的外侧都有正膨胀区域。爱琴海地区的正膨胀与地壳减薄区域相关，而中国青藏高原东部和云南省的正膨胀则与一个垂直隆升区域相关。希腊海沟的后撤显然促进了安纳托利亚高原的旋转；苏门答腊 - 缅甸海沟的后撤可能也使青藏高原东部构造结发生旋转。
Deformation measured by regional GPS networks in continental plateaus reflects the geologic and tectonic variability of the plateaus. For two collisional plateaus (Tibet and Anatolia) and one noncollisional (the Altiplano), we analyze the regional strain and rotation rate by inverting GPS velocities to calculate the full two‐dimensional velocity gradient tensor. To test the method, we use gridded velocities determined from an elastic block model for the eastern Mediterranean/Middle East region and show that to a first order, the deformation calculated directly from the GPS vectors provides an accurate description of regional deformation patterns. Principal shortening and extension rate axes, vertical axis rotation, and two‐dimensional (2‐D) volume strain (dilatation) are very consistent with long‐term geological features over large areas, indicating that the GPS velocity fields reflect processes responsible for the recent geologic evolution of the plateaus. Differences between geological and GPS descriptions of deformation can be attributed either to GPS networks that are too sparse to capture local interseismic deformation, or to permanent deformation that accrues during strong earthquakes. The Altiplano has higher internal shortening magnitudes than the other two plateaus and negative 2‐D dilatation everywhere. Vertical axis rotation changes sign across the topographic symmetry axis and is due to distributed deformation throughout the plateau. In contrast, the collisional plateaus have large regions of quasi‐rigid body rotation bounded by strike‐slip faults with the opposite rotation sense from the rotating blocks. Tibet and Anatolia are the mirror images of each other; both have regions of positive dilatation on the outboard sides of the rotating blocks. Positive dilatation in the Aegean correlates with a region of crustal thinning, whereas that in eastern Tibet and Yunnan province in China is associated with an area of vertical uplift. Rollback of the Hellenic trench clearly facilitates the rotation of Anatolia; rollback of the Sumatra–Burma trench probably also enables rotation about the eastern syntaxis of Tibet.