Estimating Response of Structures to Cascading Earthquake Tsunami Events Considering Directional Effects

The paper presents a straightforward methodology to estimate the response of coastal infrastructure subjected to cascading earthquake‐tsunami hazards. Recognizing the complex interplay between sequential hazard effects and loading orientations, the investigation systematically evaluates structural response to earthquake‐only, tsunami‐only, and combined earthquake–tsunami loadings. Both unidirectional and bidirectional loading conditions are considered, with particular emphasis on the role of incidence angles and prior earthquake‐induced damage. Using a simplified model, ground motion and tsunami data are simulated for a consistent geophysical scenario and used to identify key influences on structural response in the tsunami phase. The results reveal significant amplification in demand due to bidirectional loading for each hazard scenario. Notably, prior earthquake‐induced damage increases tsunami‐induced maximum roof displacements by approximately 60% and 70% in unidirectional and bidirectional loading, respectively. This study also brings out the sensitivity of the structural response to loading orientations. Given the computational challenges in bidirectional analysis across all orientations, a straightforward strategy that includes two simpler unidirectional analyses in surrogate orientations is proposed. These orientations can be determined in advance using the characteristics of ground motion and tsunami only. This approach can estimate the maximum responses under bidirectional loading sequences within a variation limit of approximately 5%, and may be useful in practice.