## 7 Conclusions  
In this study, a two-dimensional finite element model of soil and structure was established using ABAQUS finite element software based on the Daikai subway station. IDA was executed on the structure with pulse-like ground motion records, incorporating 32 ground motion IMs spanning five categories and seven structural DMs covering three categories. Comprehensive analysis led to the identification of optimal IMs and DMs, thereby providing a foundational framework for the performance-based seismic design of underground structures. The principal conclusions can be summarized as follows:  
* According to the seven properties of measure optimization, the optimal selection of DMs should be rigorously assessed based on efficiency, practicality, proficiency, and relativity. The IMs, on the other hand, should fulfill criteria such as scaling robustness, hazard computability, and site-specific sufficiency. In terms of IM optimization, efficiency, practicality, and proficiency stand as the cornerstone criteria, enhanced by relativity and relative sufficiency to validate the selected measures. Figure 20: Sufficiency between IMs. * For the shallow-buried subway station structure investigated in this study, DM optimization was performed using the criteria of efficiency, practicality, proficiency, and relativity. The parameters \(\theta_{\text{max}}\), \(\theta_{\text{c}}\), and \(D_{\text{e}}\) emerge as highly effective in capturing the damage state of underground structures, and their use is thus recommended. * All 32 IMs examined in this study meet the standards of scaling robustness and sufficiency with respect to fault distance. Furthermore, 78% of the selected IMs comply with the criterion of sufficiency to magnitude. However, due to the absence of comprehensive seismic disaster data and probability correction models, the hazard computability of IM could not be definitively established, though specific implementation procedures were proposed. * In the context of the shallow-buried subway station examined, the IMs were optimized using the criteria of efficiency, practicality, and proficiency. The metrics PGA, ASI, and SMA were found to be highly effective in characterizing ground motion intensity and exhibited superior relativity and relative sufficiency. This article presents the optimal selection measures for a subway station structure. Considering the complexity of the pulse-like ground motions [36], future studies should focus on the influence of the pulse period on measure optimization to eliminate these limitations. Moreover, the conclusions drawn here are all based on the Daikai subway station's context. Therefore, subsequent studies should investigate the measure optimization for different structural forms to enhance the universality of IMs and DMs in the seismic analysis of underground structures. Additionally, the seismic hazard of the region is a crucial factor in selecting ground motion records [34]. Due to the lack of geological exploration and earthquake damage data, the selection of seismic ground motions was primarily based on site type, without considering the impact of seismic risk. This issue will be further improved in subsequent studies. Finally, due to limitations in seismic disaster data and the probability correction model, only specific implementation procedures were proposed. The specific calculation of the hazard computability of IMs should be addressed in our future research [42]. Conceptualization, T.L. and Q.W. ; methodology, T.L. and Y.H. ; software, Y.H. ; validation, T.L., Y.H. and Q.W. ; investigation, T.L., Q.W. and Y.Y. ; resources, T.L. and Y.Y. ; writing--original draft preparation, Y.H. ; writing--review and editing, T.L. and Q.W. ; project administration, T.L. and Q.W. All authors have read and agreed to the published version of the manuscript.