Integrated tsunami intensity scale based on maxima of tsunami amplitude and induced current

As with earthquakes, river floods, water waves, and wind intensities, a tsunami intensity has to be synthetic and comprehensive to be efficient. Tsunami impact is complex because the effects can be felt on the beach, on inundated areas and also at berths and anchors. Within the same local area, a tsunami may severely impact the population on the coast, while its effects may be negligible on marine bodies (boats). Most existing tsunami intensity scales are based either on water elevation or on induced currents. However, it is commonly admitted that both variables should be considered simultaneously. Several existing intensity scales were integrated and were made consistent with each other. An original intensity scale is then derived based on analysis of the interdependency between the maxima of tsunami amplitude and induced current: The dimension of the couple composed by two variables is analyzed, in particular through the derivation of a linear relationship using the long wave theory and the use of a fully nonlinear numerical experiment. Our intensity scale is particularly well adapted to numerical studies, for which the two variables are naturally derived within an entire computational grid. Once the tsunami intensity scale was set up, it was briefly applied to a particular case study: the impact of the Sumatra tsunami, dated December 26, 2004, on the coast of Sri Lanka. Indeed, the tsunami scales proposed herein represent an initial framework of study and can be further improved through new or revisited tsunami observations.