This paper aims to investigate the wave-induced evolution of small-strain stiffness and its effects on seismic wave propagation. To this end, an advanced numerical framework based on the dynamic porous media theory was developed, in which the Iwan multi-surface constitutive model was adopted to model the soil behavior during cyclic loading. Moreover, the numerical framework integrates key parameters such as ocean wave characteristics and depth-dependence seabed conditions to model the intricate interactions between waves and the seabed. Following model verification via analytical solutions and previous experimental data, comprehensive parameter studies are conducted, from which the effects of different wave conditions and seabed properties on the dynamic response of the seabed were obtained, revealing the wave-induced small- strain stiffness spatial and temporal variation. Subsequently, simulations of geophysical monitoring instants are conducted, assessing the impact of evolving small-strain stiffness on seismic wave propagation. The findings highlight the implications of stiffness changes on seismic wave propagation characteristics. The study provides valuable insights into the challenges and opportunities associated with interpreting geophysical data in dynamic submarine environments, offering implications for subsurface characterization and monitoring applications.

The damage effects of the earthquake on tunnels crossing faults are categorized into two types: inertial forces generated by ground motions and permanent stratigraphic deformations caused by fault dislocations. A seismic dynamic analysis method of tunnel considering coseismic dislocation is proposed by introducing the numerical simulation of seismic wave propagation into the soil-structure dynamic analysis research field. First, seismic waves are simulated according to the finite-difference method. The stress, displacement, and velocity of nodes on the truncated boundary of the soil-structure model can be calculated according to the seismic wave propagation simulation method. Then, the seismic waves and dynamic dislocation load are simulated in the finite element model by the viscous-spring boundary. Based on the free-field model, the reliability of the presented method is validated in simulating coseismic deformation and seismic waves. In the case of the 2022 MS 6.9 Menyuan earthquake and the Daliang tunnel, which was severely damaged by this earthquake, the deformation of the tunnel simulated based on the presented method is consistent with the previous method. The proposed method can offer guidance for the seismic fortification of tunnel engineering.