Abstract
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 1.5–2.5 km and 100–150 m, respectively. Our best source model involves potential energy of 7.14 × 1013–1.05 × 1014 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.
Highlights
A large tsunami reaching a maximum runup height of 13 m (Muhari et al, 2019) was generated in the Sunda Strait, Indonesia due to volcanic activities of the Anak Krakatoa Volcano in the evening of 22 December 2018 (Fig. 1)
Satellite images from the Sunda Strait before and after the event revealed that a large portion of the middle Krakatoa volcano island collapsed into the sea as a result of the volcanic eruption (Fig. 1b)
The Krakatoa volcano tsunami occurred approximately three months after another destructive tsunami in east Indonesia, the 2018 Sulawesi tsunami, claiming around 2000 lives, which was partially attributed to subaerial/submarine landslides (Heidarzadeh et al, 2018; Takagi et al, 2019)
Summary
A large tsunami reaching a maximum runup height of 13 m (Muhari et al, 2019) was generated in the Sunda Strait, Indonesia due to volcanic activities of the Anak Krakatoa Volcano in the evening of 22 December 2018 (Fig. 1). A): The observed tide gauge records of the 22 December 2018 Anak Krakatoa volcanic tsunami. Satake (2007) modelled the 1741 Oshima-Oshima volcanic tsunami in the Japan Sea whose landslide volume was estimated to be approximately 2.5 km. The December 2018 Krakatoa volcanic tsunami is among a few ex amples of relatively well-recorded volcanic tsunamis worldwide as the tsunami was recorded by several tide gauges It is, an important event whose study will contribute to better understanding of coastal hazards from volcanic tsunamis. We propose a static source model which fairly re produces the observed tide gauge data
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