巽他弧北部掸邦高原地壳变形、长期块体运动和发震过程:来自大地测量研究结果的约束

Crustal deformation,long-term plate motion and earthquake occurrence process of the Shan Plateau region,Northern Sunda Arc:Constraints from geo-detic measurement

本文通过约束大地测量研究来探索掸邦高原及其周围地区现今的地壳变形和长期块体运动,以期提供该地区地球动力学和相关地震危险状况的最新状态。掸邦高原在横向上由西侧的萨干(Sagaing)断裂和东侧的红河断裂这两条主要断裂包围。其中,青藏高原地壳的韧性流挤压被认为是该夹层变形单元变形的主要因素。大地测量清楚地表明,萨干断裂和红河断裂段分别具有约18 mm/a和约4~5 mm/a右旋运动走滑速率。此外,掸邦高原内部断层体系大地滑移累积表现为12~13 mm/a的整体左旋运动速率。我们认为相对于刚性巽他古陆,研究区域的形变分布和长期块体运动主要受区域书架型断层作用控制,其原因是掸邦高原两侧的主断裂(萨干断裂和红河断裂)存在差异性断裂活动。

In the present article,we explore the present day crustal deformation and long-term plate motion of the Shan Plateau and surrounding region by constraining geodetic measurements to provide an updated status of geodynamics and associated seismic hazard of this region.The Shan Plateau is laterally bounded by two prominent master faults on either sides(i.e.,Sagaing fault in the western side and Red River fault in the eastern side),where extrusion of the ductile flow the Tibetan crust has been considered to be a predominant factor of the deformation in this sandwiched deformable unit.Geodetic measurements clearly indicate a dextral motion of~18 mm/yr and~45 mm/yr across the Sagaing fault and Red River fault segments,respectively.Moreover,the cumulative geodetic slip-rate across the networks of faults within the Shan Plateau indicates an overall sinistral motion of~1213 mm/yr.We argue that the distributed deformation and long-term plate motion of the Shan Plateau region,with respect to the rigid(undeformed)Sundaland block,is primarily controlled by the regional bookshelf faulting,which is evident by the differential fault motion along the two master faults on the either sides(i.e.,the Sagaing fault and Red River fault).