Abstract:
We report laboratory
experiments on surface waves generated in a uniform fluid layer
whose bottom undergoes an upward motion. Simultaneous
measurements of the free-surface deformation and the fluid
velocity field are focused on the role of the bottom kinematics
(i.e. its spatiotemporal features) 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
lowpass filter. Both filter effects are often neglected in
tsunami warning systems, particularly in real-time forecast. Our
results display good agreement with a prevailing linear theory
without any parameter fitting. Based on our experimental
findings, we provide a simple theoretical approach for modelling
the rapid kinematics limit and that is applicable even for
initially non-flat bottoms: this may be a key step for more
realistic varying bathymetry in tsunami scenarios.