Narrow Results

A new analytical solution of tsunami which is obliquely incident on a continental slope is derived based on the linear shallow water wave theory. The model of a continental slope consists of a finite constant slope and a bottom of uniform depth and has a vertical wall at the shoreline. Because of the existence of the vertical wall, another function can be taken as one of the fundamental solutions on a slope in addition to the confluent hypergeometric function M. Based on the solution obtained, the characteristics of tsunami amplification on a continental slope are discussed in terms of the conditions of the incidence. The magnitude of the amplification can be predicted with several parameters of wave incidence, such as, the incident angle and the relative incident-wave length to the topography. Especially, when a tsunami is incident almost parallel to the slope, we found that there exists distinctive amplifications for particular parameters characterizing the incident wave. The effect of the existence of the vertical wall is also discussed. The characteristics of amplification also depend much on the position of the vertical wall.

During their propagation tsunamis often traverse continental slopes that are relatively steep compared to deeper oceans. Further due to the change of bed slope from offshore to near shore, there is every likely possibility that a tsunami might steepen and eventually break, thereby generating large pressure gradients that could enhance the likelihood of liquefaction of the seabed. In the drawdown, high shear stresses could trigger debris flow in submarine canyons and on steep ridges. Therefore estimation of the bed stress is important in estimation of the forces induced during tsunami wave propagation, both on the seabed as well as on the subsurface installations. Bed and shear stresses generated by wave forms that represent tsunami (a solitary wave and broken solitary wave in the form of a bore) are measured using a shear cell. This paper deals with the measurements and modeling of the bed stress under the solitary waves.