Fig. 3

a Significant wave height of the swell that was generated in the northern part of the Pacific Ocean. The northernmost portion has hit the coast of Canada and it is propagating toward the east. b Dispersive character of the swell is depicted as it is propagating toward the east. The lower frequency energy is at its front (red region). c The wave–wave interactions can occur in the ocean of any depth such as 2 in this figure but the direct interaction can only occur in shallow ocean depths such as 1, usually a location very close to the coast. This is after Gualtieri et al. (2015)