青藏高原东北缘大陆岩石圈现今变形和位移
Recent deformation and displacement of continental lithosphere in the northeastern margin of Qinghai - Tibet Plateau
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摘要: 川青地块在地貌上为川西高原，亦是青藏高原东北边缘最重要的构造单元。新的GPS监测资料表明，在欧亚框架内，川青地块及其邻近的龙门山带和华南地块西缘的地壳运动水平速度，具有自西向东由25．66mm／a递变下降到6．99mm／a的总趋势。速度矢量表现出顺时针涡旋转动。川青地块内具有局部应变积累的非均一的区域剪切。横切鲜水河断裂带中段新的GPS量结果揭示，两侧地块间的平均左旋滑动速率约8mm／a；由于局部应变积累，断裂系南西侧的主断裂的移动速率为9．3mm／a，其间为拉分盆地和小的横向伸展断裂。鲜水河断裂系的左旋断裂滑动作用，调节了川青地块与／11滇地块之间的相对运动。Abstract: The Sichuan-Qinghai block, which is geomorphologicaUy the Westem Sichuan Plateau, is the most important tectonic unit on the northeastern margin of the Qinghai-Tibet Plateau. New GPS monitoring data indicate that in the Eurasian flame, the horizontal velocity of the crustal movement in the Sichuan-Qinghai block and its adjacent Longmen Mountain belt and the western margin of the South China block shows a general trend of decreasing progressively from 25.66 to 6.99 mm/a from west to east. The velocity vector shows a clockwise vortex rotation. A regional inhomogeneous shear field with local accumulation of strains occurs within the Sichuan-Qinghai block. The new GPS data along a profile across the central segment of the Xianshuihe fault belt reveal that the average left-lateral slip rate between blocks on both sides of the segment is -8 mm/a. The GPS data also indicate that owing to local accumulation of strains the left-lateral slip motion rate of the main fault along the southwestern margin of the fault system is 9.3 mm/a. Between the two faults, there are a pull-apart basin and a minor transverse extensional fault. The left-lateral slip motion of the Xianshuihe fault system accommodates the relative motion between the Sichuan-Qinghai block and the Sichuan-Yunnan block.
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