Seismogenic Fault Model for the 2021 Ms 6.4 Yangbi, China, Earthquake, Constraints from Multisource Data

Abstract

Deciphering a comprehensive 3D fault model for the regions with moderate-to-strong earthquakes is crucial for understanding earthquake triggering mechanisms and assessing future seismic hazards. On 21 May 2021, a massive Ms 6.4 earthquake occurred in Yangbi, Dali City, China, near the northern Red River fault zone. Despite numerous studies conducted over the past two years, the seismogenic fault of this earthquake remains a topic of controversy. In this article, we refine the workflow for 3D construction of fault surfaces from Riesner et al. (2017) and used it for the Yangbi earthquake. We constructed a seismogenic fault model for the Yangbi earthquake and Caoping fault from the collected multisource data. One utilizes a combination of focal mechanisms and relocated hypocenters, whereas the other combines geological and geophysical data from the study area. Upon analyzing these two fault models and the relocated hypocenter data, we propose that the seismogenic fault in the Yangbi earthquake is an undiscovered blind fault or a secondary blind fault of the Weixi–Qiaohou fault, rather than the surface-emerging Caoping fault.