Analysis of the migration of crust material using gravity anomaly and space-time variation of the gravity field: A case study of the eastern Qinghai-Tibet Plateau

摘要

The current study analyzed a deep environment of material flow of the lower crust and the tectonic movement caused by the flow, taking the eastern Qinghai-Tibet Plateau as an example. The depth of Moho varies from more than 70 km beneath the eastern Yushu-Qiangtang block to approximately 35 km below the Sichuan Basin. There are clear regional differences in the balanced state. Region around the Sichuan Basin is quite balanced (coefficient correlation, -1-0.8), whereas the boundary of the Sichuan-Yunnan rhombic block is relative unbalanced (-0.5) or extremely unbalanced (-0.4-0). Space-time variation of the gravity field, which uses the Jinsha River suture zone as its boundary, shows positive and negative difference characteristics from east to west. Using the Wenchuan earthquake as the time node, two stages are present: 1998-2007 and 1998-2010. The space-time variation is between -7-7x10(-8) ms(-2). These results provide an important basis for the background of lower crust material flow and the tectonic activities caused by the flow in the eastern Qinghai-Tibet Plateau.