Deformation of Continental Lithosphere Subject to Asthenospheric Drag Forces

PI将研究软流圈流动对大陆变形的影响。所使用的模型是以前用于研究西藏大陆挤压和增厚以及爱琴海地壳伸展的粘性薄片模型的扩展，现在包括了软流层流动可能产生的岩石圈底部剪切力的影响。这些效应已被一些简单的南美洲俯冲分析模型所说明，其中，下降板块在岩石圈底部产生流，施加牵引力；这些结果表明，这种影响可能是重要的，并可能提供一种机制，可能导致海岸线(如秘鲁)和广泛的地壳增厚带(高原)的形成，正如所观察到的，两者都与更陡峭的俯冲角度有关。这项工作将使用一个更完整的模型来研究这一点，使用与以前工作中使用的有限元程序类似的有限元程序。PIS还将研究西藏的形变，并调查与大规模板块运动有关的软流层流动是否可以解释所观察到的地壳增厚和向东北延伸的不对称性。这项工作将为理解亚层牵引力在其他环境中大陆变形中的作用提供基础。

The PIs will study the effects of asthenospheric flow on continental deformation. The models to be used are extensions of thin viscous sheet models that have been used before to study continental compression and thickening in Tibet and crustal extension in the Aegean, which now include the effects of shear tractions on the base of the lithosphere that may arise from flow in the asthenosphere. The effects of these has been illustrated by some simple analytical models of subduction under S. America, shere the descending plate induces flow that exerts tractions on the base of the lithosphere; these results indicate that the effect may be important, and may provide a mechanism that could lead to embayments of the coastline (as in Peru) and a broad zone of crustal thickening (the Altiplano), both associated with a steeper angle of subduction, as is observed. The work will use a more complete model to investigate this, utilizing a finite element code similar that used in previous work. The PIs will also study the deformation of Tibet, and investigate whether asthenospheric flow associated with large scale plate motions can account for the asymmetry of the crustal thickening and the extension towards the northeast that is observed. The work will provide a foundation for understanding the role of sublithospheric tractions in continental deformation in other environments.