The estimation of tsunami parameters and the study of coastal effects

Abstract

The preliminary scheme of Kurilo‐Kamchatka region tsunami zonation was made through numerical calculations by means of shallow water equations. The coast considered is 800 km long. The mean increase of the wave height is 2–3 along the coast, and in several places is up to 5–7. In Kamchatsky Bay the tsunami propagation is estimated. Because of refraction and interference of reflected waves, the level oscillations in the northern part of Kamchatsky Bay are determined mainly by the local bottom topography and the coastline features, while their dependence on the initial source orientation is slow. The calculation shows that the effect of both nonlinearity and friction is of weak influence up to the 10‐m bottom contour. The maximum decrease of height may be evaluated as 13%. In addition, the nomogram is constructed, permitting the determination of the inundation of the dry coast slope depending on the bottom slope and the height of the approaching wave. The determination of the distribution of the wave energy loss along wave paths near Shumshu and Paramushir islands is made. The value of the total reflection coefficient (at some distance from the initial source) has been defined by means of summation of partial reflections at different parts of the wave path. It is found that the zones of maximum reflection are situated mainly in the proximity of the coast where the depth is shallow. By the use of the grids with different space size, some numerical estimations of seiche‐like oscillations are performed for the rectangular closed basin. The natural oscillation periods found by calculations agree well with the values given by analytical solutions. The using of grids of mixed type allows the saving of much time when estimating tsunamis arriving from distant sources by means of calculations.