Abstract

We consider experimentally the wave generation by the collapse of a dry granular column into water. Our results show that for a given aspect ratio of the initial granular column, the amplitude of the generated wave depends on the column mass and for a given mass of the granular column, two distinct regimes are observed depending on the aspect ratio of the column a: for a < 3.5, the volume of the generated wave is directly proportional to a whereas for thinner column, a > 3.5, there is a saturation of the amplitude of the wave suggesting that the leading wave is generated before the collapse is fully completed.

Modeling of tsunami waves generated by subaerial landslides is important to provide accurate hazard and risk assessments in coastal areas. We perform small-scale laboratory experiments where a tsunami-like wave is generated by the gravity-driven collapse of a subaerial granular column into water. We show that the maximal amplitude reached near-shore by the generated wave in our experiments is linked to the instantaneous immersed volume of grains and to the ultimate immersed deposit. Despite the differences in scale and geometry between our small-scale experiments and the larger-scale geophysical events, a rather good agreement is found between the experimental law and the field data. This approach offers an easy way to estimate the amplitude of paleo-tsunamis.