From laboratory experiments to geophysical tsunamis generated by subaerial landslides

Abstract

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.

From granular collapses to shallow water waves: A predictive model for tsunami generation

“…Using this result, it is possible to compare A m /h 0 to ∆V ∞ /(W h 0 2 ) for all experiments and to draw the corresponding model curves, as shown in figure 6(d). The agreement between the experiments and the predictions allows one to explain the strong link existing between ∆V ∞ /(W h 0 2 ) and the generated wave, which was previously reported [43]. This correlation is a striking result, that may appear surprising, but one needs to keep in mind that the final deposit is the result of the gravity-driven collapse and is thus reminiscent of its dynamics.…”

“…This correlation is a striking result, that may appear surprising, but one needs to keep in mind that the final deposit is the result of the gravity-driven collapse and is thus reminiscent of its dynamics. The empirical equation for the wave amplitude given in [43] is also reported in figure 6(d), to highlight that the present model better captures the experimental data in the whole range of shallow water conditions.…”

“…In particular, the wave amplitude was related analytically to Fr f through weakly nonlinear scalings [44], or with the linear approximation A m /h 0 ≃ 1.2 Fr f [42,46]. In addition, the wave amplitude A m was found to be linked to the final immersed volume of grains ∆V ∞ , which can be measured in the field, and allows back-calculations of former events [43]. However, so far a unifying model relating the wave amplitude to the initial geometry of the column and the water depth remains elusive.…”

“…This experimental configuration has also been used recently to generate impulse waves of geophysical interest, by releasing the grains into a water layer of depth h 0 [40][41][42][43][44][45]. Several dimensionless parameters have been observed to be important for the wave generation.…”

“…Let us now explore the prediction of the model for the wave generation as a function of two dimensionless numbers, reflecting either the initial state or the final deposit of the collapse: the global Froude number Fr 0 = H 0 /h 0 [40][41][42]45] and the relative volume ∆V ∞ /(W h 0 2 ) of the immersed deposit [43]. Using Eq.…”