Deformation of Continental Lithosphere Subject to Asthenospheric Drag Forces

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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.