Numerical experiments on the potential hazard of the tsunami merging with winter storm waves after the Noto Peninsula earthquake

The Noto Peninsula Earthquake that occurred on January 1, 2024, triggered tsunamis in the Sea of Japan, creating coastal hazards along the coastline of the Hokuriku region of Japan. On the day of the earthquake, the region was affected by winter storm waves, though the waves were not severe during the tsunami arrival. In this study, numerical experiments were conducted to assess the potential hazards of this tsunami occurring under storm wave conditions using the XBeach non-hydrostatic model. The model was validated against field data measured 150 km southwest of the epicenter. Model results indicate that the combination of the tsunami with wind waves increases the wave runup heights under rough wave conditions, while the contribution of the tsunami to shoreline excursions is strongly affected by the beach topography. The tsunami water level changes shift the swash zone along the concave beach profile, indirectly enhancing or reducing wind wave runup depending on the varying slope in the swash zone. Moreover, the presence of a high beach berm effectively constrains the wave runup, protecting the coastal zone from possible inundation. These findings highlight the importance of interactions among tsunamis, wind waves, and coastal morphology in hazard assessments and disaster mitigation planning.