In this paper, dynamic response of a seabed to ocean waves is treated analy
tically on the basis of a pore-elastic theory. The seabed is modelled as an
isotropic homogeneous material of finite thickness. Most previous investig
ations for the wave-seabed interaction problem have treated the problem in
the well-known quasi-static state. However, the dynamic response of the por
ous seabed cannot be predicted in the quasi-static solutions, because the a
cceleration generated by pore fluid and soil particles are excluded in the
previous solutions. This paper proposes a semi-analytical solution for the
dynamic response of seabed to waves. Based on the newly solution, the relat
ive differences between dynamic and quasi-static solutions and the wave dri
ven seepage flux at the water-sediment interface will be examined. The wave
-induced pore fluid displacement is about ten times of soil displacements i
n gravelled seabed. The wave driven seepage flux is important in a coarser
unsaturated seabed of thicker thickness under the action of a longer wave i
n shallow water. (C) 2000 Elsevier Science Ltd. All rights reserved.