HUANG Zi-xuan, QIAO Xue-jun, YU Peng-fei, ZHAO Bin, CHEN Zheng-song, SHI Hong-bo
Zemuhe fault zone, serving as a common boundary between the Daliangshan sub-block and the Chuan-dian rhombohedral block, connects the active southeastern Tibetan Plateau with the stable Southern China block, and recent research indicates an increasing risk of strong earthquakes along this fault zone. The seismic deformation characteristics and stress distribution state of the southern section of the Zemuhe fault zone are quantitatively analyzed in this paper, utilizing newly established continuous GNSS observation data in the near field along with published regional GNSS observation data since 2017. By obtaining the interseismic motion field, we invert kinematic parameters of faults based on a double fault dislocation model. The results reveal that slip rates of the southern Zemuhe fault zone is 3.57±0.47 mm/yr and of the southern Daliangshan fault zone is 5.05±0.47 mm/yr. The near-field data of the newly constructed Zemuhe fault zone exerts a significant influence on the precision of model estimation, thereby substantially enhancing the resolution of the double-fault dislocation model. The strain rate results show that the principal strain rate direction of the eastern boundary of the Sichuan-Yunnan block is characterized by SW-NE stretching and NW-SE squeezing. The southern section of the Zemuhe fault zone presents a higher stress state, with the tensile strain rate being higher than the compressive strain rate, with the average magnitude of 41 nstrain/yr and 27 nstrain/yr, respectively, and is in the high gradient zone of the maximum shear strain rate, with the average magnitude of 28~40 nstrain/yr, indicating significant stress and energy accumulation.
