A computer program for plotting wavefronts and rays from a point source in dispersive mediums

A computer program to plot wavefronts and rays from a point source in a two-dimensional velocity field is discussed. The program is used to plot ‘fan’ refraction diagrams from London for first-mode Rayleigh waves over a selected area of the North Atlantic, the refraction being assumed to be caused by the variation of ocean depth over an infinite elastic solid. Such diagrams are prepared for frequencies 0.4, 02, 0.133, and 0.1 cps and the theoretical ratio of energy observed on land to the energy actually present, when the sources are situated at different points in the region, is computed for each of the frequencies. It is found that the continental shelf has a ‘low-pass’ filter characteristic over the frequency range. The relevance of this effect in the study of microseismic noise in the ocean bottom is discussed.