[S-GD03] Crustal Deformation

[SGD03-P09] Study on the Crustal Deformation Pattern of the Southern Zemuhe Fault Zone, China by GNSS Observations

Zixuan Huang¹, *Xuejun Qiao¹, Pengfei Yu¹, Hongbo Shi², Zhengsong Chen¹ (1.Institute of Seismology, China Earthquake Administration, 2.China Earthquake Networks Center)

Keywords:Zemuhe fault zone, Crustal deformation monitoring, GNSS, Slip rate, Locking depth, Seismic hazard

The Zemuhe fault zone, which serves as a critical boundary between the Daliangshan sub-block and the Chuan-dian rhombohedral block, connects the seismically active southeastern Tibetan Plateau with the stable Southern China block. Recent studies suggest an escalating risk of strong earthquakes along this fault zone. In this study, we quantitatively analyze the seismic deformation characteristics and stress distribution patterns in the southern section of the Zemuhe fault zone using newly established continuous GNSS observation data from the near field, combined with published regional GNSS data collected since 2017. By deriving the interseismic motion field, we invert kinematic parameters of the faults based on a double-fault dislocation model.
The results indicate slip rates of 3.78 ± 1.01 mm/yr for the southern section of the Zemuhe fault zone and 3.97 ± 0.94 mm/yr for the Daliangshan fault zone. Notably, the Zemuhe fault zone exhibits significant compressional movement near Puge, likely influenced by its strike orientation, geometric characteristics, and regional tectonic variations. Strain rate analysis reveals that the principal strain rate direction along the eastern boundary of the Sichuan-Yunnan block is characterized by SW-NE extension and NW-SE compression. The average compressive magnitude in the southern section of the fault zone reaches 40 nstrain/yr, with the region lying within a high-gradient zone of maximum shear strain rates averaging 28–40 nstrain/yr. These findings suggest substantial stress and energy accumulation, highlighting the seismic potential of the area.