[S-SS10] Strong Ground Motion and Earthquake Disaster

[SSS10-P08] High-probability ground motions simulation at Maduo County during the Maduo M_s7.4 earthquake in 2021: A possible super-shear earthquake

*Zongchao Li¹, Zhiwei Ji², Jize Sun³, Hiroe Miyake⁴, Yanna Zhao⁵, Mengtan Gao¹, Yi Ding⁶, Hongjun Si⁴ (1.Institute of Geophysics, China Earthquake Administration, 2.Institute of Earthquake Forecasting, China Earthquake Administration, 3.Shenzhen Academy of Disaster Prevention and Reduction, 4.Earthquake Research Institute, The University of Tokyo, 5.Geophysical Exploration Center, China Earthquake Administration, 6.Beijing University of Technology)

Keywords:Maduo earthquake, Small earthquake waveform, Source parameter uncertainty, Super-shear rupture, High probability

On May 22, 2021, an Ms7.4 earthquake occurred in Maduo County, Qinghai Province, on the western plateau of China. Seismic monitoring in this area was inadequate, and a few broadband seismometers within 300 km from the epicentre obtained incomplete seismic waveforms. All waveforms showed "cropped" phenomena. Destructive earthquake waveforms can provide guidance for earthquake disaster reduction in near-fault areas. This paper uses the empirical Green's function method to consider the uncertainty of source parameters and source rupture processes and synthesize high-probability and accurate ground motions from Maduo County (MAD station) near the epicenter. First, this paper synthesizes the acceleration waveform at the DAW strong-motion station, 176 km from the epicenter, with an observed waveform of the main earthquake. This step obtains a more accurate source and rupture model of the Maduo earthquake and provides an important reference standard. Second, the inferred models are applied to the acceleration waveform synthesis of MAD stations to ensure the results have high accuracy and probability. The results indicate that (1) the simulated acceleration waveform of the MAD station can better characterize the actual ground motion characteristics of the Ms7.4 earthquake in Maduo County, with high accuracy and probability in PGA ranges of 140.0–240.0 cm/s² and 350.0–390.0 cm/s², respectively, and (2) the Ms7.4 earthquake did not undergo a complete super-shear rupture process. The first asperity on the east side of the epicenter is most likely to undergo super-shear rupture. However, the Maduo earthquake may have been a complete sub-shear rupture. (3) The fault dislocation model of the three-asperity model is more closely matched with the actual source rupture process of the Maduo earthquake. This method can provide relatively accurate acceleration waveforms for areas with weak earthquake monitoring capabilities, serving analysis of building seismic damage, earthquake-induced geological disasters and sand liquefaction, and future earthquake disaster prevention.