Seismic Risk Analysis of High Earth-Rock Dam under Mainshock-Aftershock Sequence

Against the backdrop of increasing construction of high earth-rock dams in seismically active southwest China, conducting scientific seismic risk analysis is crucial for engineering safety and social stability. Traditional methods overlooked the impact of aftershocks. This study proposed a comprehensive risk analysis framework for high earth-rock dams under mainshock-aftershock sequences, integrating both seismic hazard and structural vulnerability. The research incorporated an improved indirect method for the joint hazard analysis of mainshocks and aftershocks, and utilized Copula functions to characterize the correlation between their intensities. Researchers established seismic vulnerability curves and surfaces for dam bodies based on main-aftershock sequences using a multi-strip analysis method. The analysis utilized the dam crest seismic collapse rate as the performance indicator to quantify the amplification effect of aftershocks on failure probability. The Zipingpu Dam served as a case study to test the framework. The results indicated that under the given conditions, the annual failure probability considering mainshock-aftershock effects was 6.05 × 10⁻⁸, which fell within an acceptable risk level. This study quantified the influence of aftershocks on dam seismic risk and provided a standardized quantitative method for mainshock-aftershock risk assessment, offering practical support for seismic design, risk management, and emergency planning.