The ground-motion simulation of regional-specific earthquake scenarios is crucial for the seismic design of key facilities. Herein, we considered parameter uncertainty in ground-motion simulations and the impact of multiple faults when determining the maximum credible ground-motion parameters of large earthquakes at a near-field dam. The source models of the Daju–Lijiang, Xiaozhongdian–Daju, and Longpan–Qiaohou faults were established based on geological and geophysical data. Although the method for identifying asperity is not yet mature and still faces many difficulties, it provides an opportunity to identify the non-uniform slip distribution on the rupture plane by earthquake scenarios. A multi-scheme stochastic finite-fault simulation method was then used to estimate the minimum; mean; maximum; and 50th-, 84th-, and 95th-percentile values of the peak ground acceleration and pseudo-spectral acceleration response spectra. The results showed that the Longpan–Qiaohou fault can generate the largest ground-motion parameters compared with the other two faults. Moreover, this result was supported by the statistical analysis of the results of twelve thousand simulations of these three faults. Thus, it can be concluded that the maximum credible ground-motion parameters are represented by the 84th-percentile pseudo-spectral acceleration response spectrum of the Longpan–Qiaohou fault. This finding will benefit the seismic safety design of the target dam. More importantly, this multi-scheme method can be applied to other key facilities to obtain reasonable ground-motion parameters.

The middle segment of the Kalawenguquan fault has been active since the Holocene, with a maximum credible earthquake magnitude of M_S 7.5. We established two source models based on empirical relationships, as well as geological, geomorphological, and seismic characteristics. Taking into account the uncertainties of simulation parameters, we adopted the stochastic finite-fault method to calculate all combinations of a multi-scheme simulation. The effects of different source models, initial rupture points, and site locations on the prediction of ground motion parameters were analyzed. The results indicate that when a site is located on a smaller asperity and is a certain distance from the largest asperity, the simulation results are higher. For different sites, when the initial rupture point is located near the smaller rather than the larger asperity, the acceleration response spectra are higher. Our results show that the relationships between the initial rupture points, asperities, and sites have a significant impact on the simulation results. Therefore, our study highlights the relevance of determining the initial rupture point and source model to obtain a reasonable evaluation for near-field strong ground motion simulations at major infrastructures.