Distribution functions of the tsunami run-up heights (from the data of international expeditions of 1992-1998)

The data on the run-up heights obtained from expeditionary examinations of a series of tsunamis over the past decade are used in order to calculate th eir distribution functions. The lognormal distribution is shown to represen t the best fit of the data observed; hence, the principal factor controllin g the wave height distribution along the coast is the inhomogeneity of the bottom topography and the coastline. The power-law distribution, mostly rel ated to the geometrical attenuation of a wave during its propagation, descr ibes the wave height distribution of a single event only (Sulawesi, January 1, 1996). The influence of the finiteness of the number of measurements on the possibility of the estimation of the maximum run-up height from the me asured values of the average height and dispersion is assessed. It is shown that, in the coastal zone, 30-40 measurements are sufficient to obtain rel iable results.