The interaction of the Indian and Asian plates under the central Tibet: Insights from seismic velocity and gravity data

Abstract:

The ongoing collision between the Indian and Eurasian plate has resulted in the continuous growth of the Tibetan Plateau. The northern part of the Tibetan Plateau is regarded as a key place to understand the interaction between the Indian and Asian plates. Though a large amount of geophysical observations have been carried out to understand the structure of the Tibetan plateau, whether or not the Asian plate is subducting southwards underneath the northern margin of the Tibetan Plateau is still hotly debated. An answer to this the scientific question could provide critical constraints on the thickening of the crust and the origin of the widely distribution of igneous rocks in this region.

In this study, using our previously obtained shear wave velocity model at depths of 0-200 km as a useful constraint we semi-quantitatively derive a density structure in this region from mutual technique. We first obtain an initial theoretical density model of the lithosphere in this region through the empirical scale relationship between velocity and density as well as combining the existing surface heat flow and petrological data. Subsequently, we modify the initial density model to fit the observed Bouguer gravity anomaly data (from the International Gravimetric Bureau) with a trial and error method. After completion of this work, we will obtain the lithospheric density structure along several N-S cross-sections. Combined with other geophysical observations, we expect to distinguish whether or not the Asian plate is subducting southwards underneath the northern margin of the Tibetan Plateau.