Analytical investigation on tsunamis generated by submarine slides

Abstract

Tsunamis induced by landslides are a topic on which growing attention is being paid especially under the pressure of recent events in which movement of underwater masses have been recognised to be the certain or likely cause of the observed tsunami. Here analytical methods and idealised cases are used to investigate tsunami generation by submarine slides that undergo negligible deformation during their motion, such as slumps. The general solution of the 1D Cauchy linear problem for long water waves is specialised to deal with rigid bodies and is used systematically to explore the main characteristics of the generated waves. Relationships between body motion, that is prescribed in terms of the slide Froude number, and wave pattern, wave amplitude and wave energy are studied in dimensionless space. Wave generation in various flow conditions (from subcritical to supercritical) is handled, though most attention is given to analysing tsunamis induced by submarine slides at subcritical speed which are by far the most common cases. From numerical experiments it is found that good estimates of the tsunami wave amplitude can be calculated by means of simple expressions based on the maximum value and on the average value of the Froude number during the main generation phase.