Fluids Triggered the 2021 Mw 6.1 Yangbi Earthquake at an Unmapped Fault: Implications for the Tectonics at the Northern End of the Red River Fault

Sun, Quan1; Guo, Zhen1,2; Pei, Shunping3; Fu, Yuanyuan, V4; Chen, Yongshun John1,5

2022-03-01

10.1785/0220210227

SEISMOLOGICAL RESEARCH LETTERS   影响因子和分区

0895-0695

1938-2057

On 21 May 2021 a magnitude Mw 6.1 earthquake occurred in Yangbi region, Yunan, China, which was widely felt and caused heavy casualties. Imaging of the source region was conducted using our improved double-difference tomography method on the huge data set recorded by 107 temporary stations of ChinArray-I and 62 permanent stations. Pronounced structural heterogeneities across the rupture source region are discovered and locations of the hypocenters of the Yangbi earthquake sequence are significantly improved as the output of the inversion. The relocated Yangbi earthquake sequence is distributed at an unmapped fault that is almost parallel and adjacent ( similar to 15 km distance) to the Tongdian-Weishan fault (TWF) at the northern end of the Red River fault zone. Our high-resolution 3D velocity models show significant high-velocity and low-VP/ VS ratios in the upper crust of the rupture zone, suggesting the existence of an asperity for the event. More importantly, low-VS and high-VP/ VS anomalies below 10 km depth are imaged underlying the source region, indicating the existence of fluids and potential melts at those depths. Upward migration of the fluids and potential melts into the rupture zone could have weakened the locked asperity and triggered the occurrence of the Yangbi earthquake. The triggering effect by upflow fluids could explain why the Yangbi earthquake did not occur at the adjacent TWF where a high-stress accumulation was expected. We speculate that the fluids and potential melts in the mid-to-lower crust might have originated either from crustal channel flow from the southeast Tibet or from local upwelling related to subduction of the Indian slab to the west.

SCI ; EI

英语

第一 ; 通讯

National Science Foundation of China[41974052,42122027,41890814,"U1901602",41774052,"U2039203"] ; National Natural Science Foundation for Young Scientists of China[42104050] ; China Postdoctoral Science Foundation[2021M701559]

Geochemistry & Geophysics

Geochemistry & Geophysics

WOS:000762027700004

SEISMOLOGICAL SOC AMER

20221211814785

Faulting

Seismology:484 ; Earthquake Measurements and Analysis:484.1

GEOSCIENCES

Web of Science

1.Southern Univ Sci & Technol, Dept Ocean Sci & Engn, Shenzhen, Peoples R China
2.Shanghai Sheshan Natl Geophys Observ, Shanghai, Peoples R China
3.Chinese Acad Sci, Inst Tibetan Plateau Res, State Key Lab Tibetan Plateau Earth Syst & Resour, Beijing, Peoples R China
4.China Earthquake Adm, Key Lab Earthquake Predict, Inst Earthquake Sci, Beijing, Peoples R China
5.Southern Marine Sci & Engn Guangdong Lab Guangzho, Shenzhen, Peoples R China

Sun, Quan,Guo, Zhen,Pei, Shunping,et al. Fluids Triggered the 2021 Mw 6.1 Yangbi Earthquake at an Unmapped Fault: Implications for the Tectonics at the Northern End of the Red River Fault[J]. SEISMOLOGICAL RESEARCH LETTERS,2022,93(2A):666-679.

Sun, Quan,Guo, Zhen,Pei, Shunping,Fu, Yuanyuan, V,&Chen, Yongshun John.(2022).Fluids Triggered the 2021 Mw 6.1 Yangbi Earthquake at an Unmapped Fault: Implications for the Tectonics at the Northern End of the Red River Fault.SEISMOLOGICAL RESEARCH LETTERS,93(2A),666-679.

Sun, Quan,et al."Fluids Triggered the 2021 Mw 6.1 Yangbi Earthquake at an Unmapped Fault: Implications for the Tectonics at the Northern End of the Red River Fault".SEISMOLOGICAL RESEARCH LETTERS 93.2A(2022):666-679.