Lucy Marie Flesch

Gravitational potential energy of the Tibetan Plateau and the forces driving the Indian plate

We present a study of the vertically integrated deviatoric stress field for the Indian plate and the Tibetan Plateau associated with gravitational potential energy (GPE) differences. Although the driving forces for the Indian plate have been attributed solely to the mid-oceanic ridges that surround the entire southern boundary of the plate, previous estimates of vertically integrated stress magnitudes of ~6–7 x 1012 N/m in Tibet far exceed those of ~3 x 1012 N/m associated with GPE at mid-oceanic ridges, calling for an additional force to satisfy the stress magnitudes in Tibet. We use the Crust 2.0 data set to infer gravitational potential energy differences in the lithosphere. We then apply the thin sheet approach in order to obtain a global solution of vertically integrated deviatoric stresses associated only with GPE differences. Our results show large N-S extensional deviatoric stresses in Tibet that the ridge-push force fails to cancel. Our results calibrate the magnitude of the basal tractions, associated with density buoyancy driven mantle flow, that are applied at the base of the lithosphere in order to drive India into Tibet and cancel the N-S extensional stresses within Tibet. Moreover, our deviatoric stress field solution indicates that both the ridge-push influence (~1 x 1012 N/m) and the vertically integrated deviatoric stresses associated with GPE differences around the Tibetan Plateau (~3 x 1012 N/m) have previously been overestimated by a factor of two or more. These overestimates have resulted from either simplified two-dimensional approximations of the thin sheet equations, or from an assumption about the mean stress that is unlikely to be correct.