In the context of offshore structure design, the consideration of earthquake and wave loadings is paramount due to their pivotal role as natural dynamic forces. These dynamic forces can induce vibrations in the pore water pressure, thereby precipitating seabed instability. However, the investigations of the earthquake-induced seabed behaviour are limited. Furthermore, contemporary studies on seismic seabed response often neglect the concurrent impact of ocean waves. Previous research predominantly relies on conventional mesh-based methods, such as the finite element method. To address the limitations inherent in such methods, such as computational time and mathematical complexity, this study employs a meshfree method based on the u - p approximation. The research assesses soil response under the Japan 311 earthquake and random wave loading in both time and frequency domains. Numerical findings indicate that earthquake-induced acceleration is notably amplified by the seabed foundation, particularly in the horizontal direction. The presence of wave loading significantly alters the development of pore pressure, yet it exerts no discernible impact on earthquake-induced acceleration in the seabed. Consequently, the contribution of random waves to seismic-induced seabed response analysis cannot be disregarded.