Deformation-strain field characteristics and fault activities in central Yunnan water diversion project area

Abstract

The movement and deformation characteristics of an active fault zone are an important prerequisite for the stability analysis of cross-fault project sites and breaking resistance design research. Based on the global positioning system (GPS) data of the Crustal Movement Observation Network of China, a GPS velocity clustering algorithm to avoid the uncertainties of block division results from geological data is proposed and applied for velocity field analysis of Yunnan province. Using the data of active faults in the central Yunnan water diversion project area and the clustering results along with a block rotation and uniform strain model, the current slip rates of the main fault were obtained by using the difference between the speeds of the same point at the boundary of neighboring blocks. Furthermore, using the 1999–2007, 2009–2013, and 2013–2015 GPS velocity field data as the constraints, the relation between the spatial points and velocities was established based on the least squares collocation theory. The distribution of strain rates in the central Yunnan water diversion project area were resolved by the spherical strain calculation method, and the dynamic variation characteristics were analyzed using regional historical earthquakes and fault properties. The results of this study show that Xiaojinhe–Lijiang and Xiaojiang faults currently have noticeable strike–slip motion. The southern Xiaojinhe–Lijiang and Xiaojiang faults have always been two strong deformation zones, and the extensional deformations in Longpan–Qiaohou, Lijiang–Jianchuan, and Chenghai–Binchuan regions are being enhanced. Xiaojiang fault is the zone with the maximum shear strain rate. These results indicate that the deformation distribution characteristics are closely related to the characteristics of the activity features of the major faults in the region.