<p>To investigate the impact of irregular topography on the seismic response of nearby structures. This study presents an analytical solution using the wave function expansion method. This analysis focuses on the dynamic interaction between a semicircular canyon and an adjacent building under SH waves. The dynamic interaction involving canyon-soil-structure is separated into scattering and radiation problems. The building is modeled as a shear wall supported by a semicircular rigid foundation surrounded by flexible bearing layers. The validity of the model is confirmed through compressions with established solutions. Parametric analyses are conducted in both the frequency and time domains to quantify the influence of canyon geometry, wave incidence angle, foundation-canyon distance, and bearing layer properties on the seismic response of the foundation and superstructure. Time-domain analyses using recorded earthquake motions indicate that, for an incident angle of 45°, the presence of the canyon reduces the peak ground acceleration (PGA) of the foundation and the shear wall top by 30.53% and 34.73%, respectively, demonstrating a pronounced shielding effect. In contrast, for incident angles of 90°, the canyon amplifies the foundation PGA by 27.91% and the superstructure PGA by 46.39%. For 135° incidence, the focusing effect becomes dominant, leading to PGA amplification of 40.09% at the foundation and 24.12% at the shear wall top. The results further reveal that canyon topography primarily modifies the seismic input motion at the foundation level, while the relative displacement of the superstructure is comparatively less sensitive to canyon effects under identical structural properties. These findings provide quantitative insight into canyon-soil-structure interaction mechanisms and highlight the importance of explicitly accounting for topographic effects in seismic design of structures located in complex geological environments.</p>