【摘要】 高精度布格重力异常约束下的三维空间域挠曲形变模拟显示,大约以90°E为界,青藏高原东、西两部分的岩石圈强度存在明显的差异.在90°E以东,岩石圈有效弹性厚度为35~45km,该岩层厚度可使刚性的上地壳与上地幔岩石通过中下地壳柔塑性地层的黏滞流动产生构造解耦;地壳处于区域均衡状态,下地壳热物质的流动膨胀是地壳隆升的主控要素.而在90°E以西,断裂带严重削弱了该区域的岩石圈机械强度,岩石圈有效弹性厚度小于15km,向西逐渐减小,至喀喇昆仑断裂带变为零,断裂切穿莫霍面进入地幔,发生纯剪切构造形变;这里的地壳接近局部均衡,厚皮逆冲是地形隆升的主要因素.震源深度大于80km的地幔地震大多发生在青藏高原西部,其岩石圈深部具有的脆裂特征很好地支持了岩石圈机械强度模拟的结果.更多还原

【Abstract】 Distinct mechanical strength over the eastern and western Tibetan plateau derived from flexural modeling suggests a possible different uplift mechanisms between these two portions of the plateau roughly bounced by 90°E.To the east of this longitude,the mechanical strength of the lithosphere measured by effective elastic thickness(Te)is 35 to 45km which permits the decoupling between the strong upper crust and the strong upper mantle lithosphere by week,viscous and flowing middle and lower crust in the middle.In the crustal regional equilibrium in the eastern plateau,the flow and expansion of hot material in lower crust are the main controlling factors of crustal uplift.However,to the west of the 90°E,the strength of the lithosphere gradually decreases toward west till Te values are close to zero along the Karakorum fault.The nearly strength-less lithosphere to the west implies that the entire lithosphere is significantly faulted from surface to the mantle.The occurrence of the mantle earthquakes with focal depths larger than 80 km in the mantle lithosphere are almost all populated to the western and eastern syntaxes of the Tibetan plateau,particularly in the western end of the Himalayas.In the crustalpartial equilibrium,the thick leather thrusting is the main controlling factor of topographic uplift.This evidence of deep brittle failure in the western lithosphere well supports the results from the mechanical modeling.更多还原