Quantitative estimation of the effective elastic thickness around the Burma Plate and correlation analysis of its influencing factors

Abstract

The Burma Plate is a microplate that extends along the boundary between the Indian and Eurasian plates. It is characterized by an extraordinarily complex lithospheric tectonic setting, resulting from the continental collision in the north, the oceanic crustal subduction in the south, and the large amount of sediment from the Tibetan Plateau. The lithospheric strength is a key to understanding the tectonic evolution of the Burma Plate. In this study, we use topography and gravity disturbance data to estimate the spatial distribution of effective elastic thickness $\mathrm{Te},$ which is a measure of lithospheric strength. The $\mathrm{Te}$values range from $\sim$10 km to 80 km, with higher values in the Indian Plate than those in the other regions. The non-isostatic flexural effects of sediment loading and subducting slab pull can bias the $\mathrm{Te}$ estimation, with maximum reductions of $\sim$50 km and $\sim$10 km, respectively. The consistent distributions of the $\mathrm{Te}$ and the shear wave velocity anomaly $\Delta \mathrm{Vs}$at 100 km depth suggest that the lithospheric strength is generally controlled by the thermal structure of the upper mantle. Meanwhile, the $\mathrm{Te}$ variations are highly related to the geometry of the subducting Indian Plate along the collision and subduction zones, indicating that the plate tectonics play a dominant role in determining the lithospheric strength of the Burma Plate.