Identification and analysis of crustal motion and deformation models in the Sichuan-Yunnan region

Abstract

The Sichuan-Yunnan region is located in the southeast of the Tibetan Plateau. The pattern of its crustal motion and deformation plays an impor- tant role in understanding the continental tectonic deformation. In this paper, 249 high precision GPS velocities are used to estimate the crustal motion and deformation in the region by employing the rigid block motion model and the strain rate model, re- spectively. On the basis of the inversion results, we form statistic tests to identify the two crustal move- ment models. As a result, the strain-rate model is more suitable for describing the crustal movement model in the region. The Qiangtang block, the north-western Sichuan sub-block, the middle Yunnan sub-block, the Baoshan sub-block and the Jinggu sub-block show a clockwise rotation, and their veloc- ities are from high to low. With respect to the Eura- sia plate, the Qiantang block moves N114.6e 1.3 � E at a rate of 17.0e 0.6 mm/yr; the north-western Sichuan sub-block moves N134.2e 1.8 � E at a rate of 15.9e 0.7 mm/yr; the middle Yunnan sub-block moves N157.1e 1.7 � E at a rate of 13.1e 0.6 mm/ yr, the Baoshan sub-block moves N193.4e 5.1 � Ea t a rate of 9.0e 1.1 mm/yr and the Jinggu sub-block moves to N182.2e 3.7 � E at a rate of 7.7e 0.7 mm/ yr. The Sichuan-Yunnan rhombic sub-block in the region is of high shearing strain rate and surface dilatation rate, which are up to 25:5e 7:6 � 10 � 9 / yr and 7:5e 7:6 � 10 � 9 /yr in the north-western Sichuan sub-block and 37:1e 4:8 � 10 � 9 /yr and 12:8e 4:8 � 10 � 9 /yr in the middle Yunnan sub- block, respectively. The main fault velocities in the Sichuan-Yunnan region are about 10 mm/yr. The characteristics of the Sichuan-Yunnan crustal mo- tion and deformation do not support the hypothesis of ''the continental deformation as discontinuous deformation''.