Numerical modeling of the subaerial landslide source of the 22 December 2018 Anak Krakatoa volcanic tsunami, Indonesia

The eruption of the Anak Krakatoa volcano (Indonesia) in December 2018 produced a destructive tsunami with maximum runup of 13 m killing 437 people. Since the occurrence of this rare tsunami, it has been a challenge as how to model this tsunami and to reconstruct the network of coastal observations. Here, we apply a combination of qualitative physical modeling and wavelet analyses of the tsunami as well as numerical modeling to propose a source model. Physical modeling of a volcano flank collapse showed that the initial tsunami wave mostly involves a pure-elevation wave. We identified initial tsunami period of 6.3-8.9 min through Wavelet analysis, leading to an initial tsunami dimension of 1.8-7.4 km. Twelve source models were numerically modelled with source dimensions of 1.5-4 km and initial tsunami amplitudes of 10-200 m. Based on the qualities of spectral and amplitude fits between observations and simulations, we constrained the tsunami source dimension and initial amplitude in the ranges of 1.5-2.5km and 100-150m, respectively. Our best source model involves potential energy of 7.14 x 10(13) -1.05 x 10(14) J equivalent to an earthquake of magnitude 6.0-6.1. The amplitude of the final source model is consistent with the predictions obtained from published empirical equations.