Generation of surface waves by an underwater moving bottom: Experiments and application to tsunami modelling

TL;DR

This study experimentally investigates how sudden bottom movements generate surface waves, revealing filtering effects and proposing a new theoretical model applicable to non-uniform bottoms for improved tsunami prediction.

Contribution

It introduces a new theoretical approach for rapid bottom kinematics that accounts for non-flat bottoms, enhancing tsunami modeling accuracy.

Findings

Fluid layer acts as a high-pass temporal filter and a low-pass spatial filter.

Experimental results align well with linear theory without fitting parameters.

New model applicable to arbitrary topography for tsunami simulations.

Abstract

We report laboratory experiments on surface waves generated in a uniform fluid layer whose bottom undergoes a sudden upward motion. Simultaneous measurements of the free-surface deformation and the fluid velocity field are focused on the role of the bottom kinematics in wave generation. We observe that the fluid layer transfers bottom motion to the free surface as a temporal high-pass filter coupled with a spatial low-pass filter. Both filter effects are usually neglected in tsunami warning systems. Our results display good agreement with a prevailing linear theory without fitting parameter. Based on our experimental data, we provide a new theoretical approach for the rapid kinematics limit that is applicable even for non-flat bottoms: a key step since most approaches assume a uniform depth. This approach can be easily appended to tsunami simulations under arbitrary topography.