Predicting Near-Field Strong Ground Motion of the Huaxian Ms8.5 Earthquake Based on Uncertainty Factors of Asperities

Abstract

The Weihe Plain is at high risk of disastrous earthquakes, such as the Huaxian Ms8.5 earthquake, which caused enormous casualties and economic losses. Therefore, reproducing the strong ground motion characteristics of the Huaxian earthquake is important for seismic design and disaster mitigation. The empirical Green’s function method is used to predict the ground motion characteristics of the Huaxian Ms8.5 earthquake by considering the uncertainty factors of asperities, considering the limited observations in the Weihe Plain and the inaccessibility of the Earth’s interior. The uncertainty asperity factors can be studied by the logic tree method, and source models considering these factors are constructed here. The uncertainty factors include the seismic moment M0, number of subfaults N, stress drop of an asperity Δσ, and asperity area Sa. The asperity area is assigned values of 19%, 22%, and 25% of the fault rupture area; the M0 values of the corresponding asperities account for 40%, 44%, and 48% of the entire M0; and there are two to four asperities. The permutations are combined into multiple-asperity source models. The two-asperity source models reflect the Huaxian earthquake characteristics better than the three- or four-asperity models. The asperity area accounts for approximately 22–25% of the fault rupture area, while the M0 of the corresponding asperities accounts for 44% and 48% of the entire M0. The long-axis direction of the ground motion distribution is the same as that of the mountains southeast of the Weihe Plain. The azimuth angle of the elliptical long axis is approximately 40–60° northeast. The greater the magnitude is, the more complex the number, location, and area of the asperities. This research extends the application of the empirical Green’s function method and can numerically simulate seismic intensity characteristics in areas with destructive earthquakes but few seismic records.