Experiments on generation of surface waves by an underwater moving bottom

T. Jamin1, L. Gordillo1, G. Ruiz-Chavarría2, M. Berhanu1 & E. Falcon1
1 Univ Paris Diderot, Sorbonne Cité, MSC, CNRS, UMR 7057, F-75 013 Paris, France
2 Facultad de Ciencias, Universidad Nacional Autónoma de México, 04510 México D. F., México

Reference:  Proceedings of the Royal Society A 471, 20150069 (2015)

URL:  http://rspa.royalsocietypublishing.org/content/471/2178/20150069


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. 

Keywords : tsunami generation, gravity surface waves

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