Abstract: Southwest Yunnan is an earthquake active area. The deep and shallow deformation characteristics of the lithosphere in this area is of great significance to understand its seismogenic environment and mechanism. This study is based on independent observation and collected regional GNSS data, the GNSS velocity field in Southwest Yunnan is studied. Then the multi-scale spherical wavelet method is used to calculate the strain rate tensor, and the spatial distribution characteristics of principal strain rate, surface strain rate and maximum shear strain rate are analyzed. The results show that the southwest of Yunnan is compressed by nearly NNE—SSW, and the surface compressibility is ~10 nstrain/a. The near east-west fault is characterized by left-hand strike slip, and the near north-south fault is characterized by right-hand strike slip. There is an obvious transformation between surface compression and surface expansion in the area between Heihe fault and Wuliangshan fault. Wanding fault, east of Longling-Ruili fault, east of Nantinghefault, Heihe fault, Lancang fault and Xiaojiang fault extend across Honghe fault to Menglian-Mengxing fault area has high shear strain rate, up to 50 nstrain/a. The focal mechanism solutions of the study area from 1976 to 2020 are collected, the regional damping stress inversion method is used to invert the stress tensor, and the R-value distribution reflecting the relative size of the principal stress is attained. The inversion results show that the southwest of Yunnan is affected by the principal compressive stress in the NNE—SSW direction, and the area is in the state of strike slip stress as a whole, The North-south fault near Tengchong volcano in the east of Dayingjiang fault has the characteristics of normal fault and oblique slip. The magnitude of principal stress in Southwest Yunnan is obviously different in space. The south of Nantinghe fault is the area with the largest principal stress, and its strike slip characteristics are more obvious. In addition, this study also collects seismic wave anisotropy data in the study area, compares the angle between the direction of the principal stress axis and the principal strain rate axis, the angle between the direction of the principal stress axis and the polarization direction of Pms fast wave, the angle between the direction of the principal stress axis and the polarization direction of XKS fast wave, the angle between Pms fast wave direction and XKS fast wave polarization direction, we obtains the structural deformation differences between the surface and middle upper crust, middle upper crust and lower crust, lower crust and upper mantle respectively, It is found that the lower crust and upper mantle are decoupled in Southwest Yunnan. At the same time, it is found that the difference in deformation between the lower crust and the middle upper crust near Longling-Ruili fault, Nantinghe fault and Menglian fault, indicating that the lower crust and the middle upper crust are decoupled in this area, and there may be a hot material flow channel in the lower crust, with localized lower crustal flow in partial zones of southwestern Yunnan.

Key words: Southwest Yunnan, Strain rate field, Stress field, Multiscale spherical wavelet, Seismic anisotropy