EGU22-6917, updated on 09 May 2022
https://doi.org/10.5194/egusphere-egu22-6917
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Aseismic slip and cascade triggering process of foreshocks leading to the 2021 Mw 6.1 Yangbi Earthquake

Xiao Ge Liu1, Wen Bin Xu1, Zi Long He1, Li Hua Fang2, and Zhi Dan Chen1
Xiao Ge Liu et al.
  • 1Laboratory of Volcano and Earthquake Research, School of Geosciences and Info-Physics, Central South University, Changsha 410083, Hunan, P.R. China
  • 2Institute of Geophysics, China Earthquake Administration, Beijing 100081, China.

Understanding the nature of foreshock evolution is important for earthquake nucleation and hazard evaluation. Aseismic slip and cascade triggering processes are considered to be two end-member precursors in earthquake nucleation processes. However, to perceive the physical mechanisms of these precursors leading to the occurrence of large events is challenging. In this study, the relocated 2021 Yangbi earthquake sequences are observed to be aligned along the NW-SE direction and exhibit several evident spatial migration fronts towards the hypocenters of large events including the mainshock. An apparent static Coulomb stress increase on the mainshock hypocenter was detected, owing to the precursors. This suggests that the foreshocks are manifestations of aseismic transients that promote the cascade triggering of both the foreshocks and the eventual mainshock. The temporal depth of the brittle-ductile transition exhibit deepening, followed by shallowing during the foreshock-mainshock-aftershock sequence. By jointly inverting both InSAR and GNSS data, we observe that the mainshock ruptured on a blind vertical fault with a peak slip of 0.8 m. Our results demonstrate that the lateral crustal extrusion and lower crustal flow are probably the major driving  mechanisms of mainshock. Additionally, the potential seismic hazards on the Weixi-Weishan and Red River faults deserve further attention

How to cite: Liu, X. G., Xu, W. B., He, Z. L., Fang, L. H., and Chen, Z. D.: Aseismic slip and cascade triggering process of foreshocks leading to the 2021 Mw 6.1 Yangbi Earthquake, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6917, https://doi.org/10.5194/egusphere-egu22-6917, 2022.

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