Abstract
The radiation pattern of the tsunami generated by a broad crustal deformation on or near the continental shelf is examined analytically in the framework of a linear longwave approximation. Detailed discussion, however, is made only for a model of step-type bottom topography.
The proportion of the energy trapped on the shelf as edge wave modes relative to that radiated into deep water increases with the decrease of the long-shore dimension of the source. The nearer is the source to the coastline, the greater is the rate of total edge wave generation. However, the proportion of higher modes increases for the source near the shelf edge.
The proportion of the wave energy radiated in deep water, normal to the coastline, increases with the increase of the long-shore dimension of the source and/or the decrease of the depth difference between the shelf and deep water. Furthermore, this proportion increases with the increased distance of the source location from the coastline and approaches the value for the case without a shelf. For a source of the square shape, the directive difference of energy radiation in deep water is mainly caused by the refractive effect of the shelf edge. For larger long-shore dimension of the source, however, the geometric shape effect of the source is more important to cause the directive difference.
