Crustal thickness, VP/VS ratio, and shear wave velocity structures beneath Myanmar and their tectonic implications

Abstract

The crustal structure in Myanmar can provide valuable information for the eastern margin of the ongoing Indo-Eurasian collision system. We successively performed H–k stacking of the receiver function and joint inversion of the receiver function and surface wave dispersion to invert the crustal thickness (H), shear wave velocity (VS), and the VP/VS ratio (k) beneath nine permanent seismic stations in Myanmar. H was found to increase from 26 ​km in the south and east of the study area to 51 ​km in the north and west, and the VP/VS ratio was complex and high. Striking differences in the crust were observed for different tectonic areas. In the Indo-Burma Range, the thick crust (H ​∼ ​51 ​km) and lower velocities may be related to the accretionary wedge from the Indian Plate. In the Central Myanmar Basin, the thin crust (H ​= ​26.9–35.5 ​km) and complex VP/VS ratio and VS suggest extensional tectonics. In the Eastern Shan Plateau, the relatively thick crust and normal VP/VS ratio are consistent with its location along the western edge of the rigid Sunda Block.