Simulation of the 2018 Tsunami Due to the Flank Failure of Anak Krakatau Volcano and Implication for Future Observing Systems

Abstract

Motivated by the unwarned tsunami disaster caused by the flank collapse of the Anak Krakatau volcano on 22 December 2018, we used a landslide tsunami model to explore potential tsunami observing and warning systems for the region. With the estimated volume of 0.24 km3 and the relatively short duration (~3 to 5 min), the landslide of the volcanic edifice in the southwest sector triggered a tsunami of higher than 40 m in the vicinity. The tsunami, however, attenuated rapidly as it propagated away from the generation area, resulting in lower than 2 m wave heights at tide gauges around the Sunda Strait. Using the tsunami model, we demonstrated the capability of a ship height positioning method to detect the tsunami of amplitude ~20 cm associated with the event. Furthermore, assimilating the tsunami current velocity observed by high‐frequency oceanographic radars can produce accurate forecasts of coastal tsunami heights.

Submarine landslide megablocks show half of Anak Krakatau island failed on December 22nd, 2018

“…Our new volume calculation is close to the lowest end of this volume range, similar to the authors’ revised model. The landslide volume presented here is also supported by tsunami modelling estimates in other studies 24 – 27 , 34 – 37 ; thus, indicating that our mapped landslide volume can explain the recorded tsunami without the need to invoke any additional source mechanisms.…”

“…Although a superficially similar edifice, the pattern of disintegration at Anak Krakatau is in strong contrast to Ritter, suggesting that the bulk properties, fragmentation and pre-collapse pattern of deformation preconditioning failure, may not be easily predictable. Nevertheless, for Anak Krakatau, assuming either a simple dense Newtonian fluid or homogeneous granular slide rheology, numerical models can reproduce, the near-and far-field tsunami observations from our estimated failure volume 14,[24][25][26][27][33][34][35][36][37]45,46 . While translational subaerial landslides are reported at other volcanic island sites, the detailed pre-and post-event surveys at Anak Krakatau and direct monitoring of the tsunami makes this an important benchmark event.…”

Landslide triggered tsunami modelling: A study in Anak Krakatoa collapse

“…Numerical modeling is a fit approach to forecast wave propagation and inundation on land [10]. Different approaches of modeling have been presented for the 2018 Sunda Strait tsunami [8], [5].…”

Review on Recent Progress in Near-Field Tsunami Forecasting Using Offshore Tsunami Measurements: Source Inversion and Data Assimilation

“…High-frequency radar has also been proposed for tsunami data assimilation (Kimura et al, 2018). Unlike OBPGs or GPS buoys, high-frequency radars monitor the radial flow velocity distribution and assimilate velocity data for tsunami early warning (Mulia et al, 2020b). Synthetic experiments have been successfully conducted on tsunamis in the vicinity of the Kashiwazaki-Kariwa Nuclear Power Station, Japan, and the volcanic tsunamis of the Anak Krakatau collapse (Kimura et al, 2018;Mulia et al, 2020b).…”

“…Unlike OBPGs or GPS buoys, high-frequency radars monitor the radial flow velocity distribution and assimilate velocity data for tsunami early warning (Mulia et al, 2020b). Synthetic experiments have been successfully conducted on tsunamis in the vicinity of the Kashiwazaki-Kariwa Nuclear Power Station, Japan, and the volcanic tsunamis of the Anak Krakatau collapse (Kimura et al, 2018;Mulia et al, 2020b). Mulia et al (2020a) proposed a moving platform for tsunami monitoring and data assimilation, which consisted of a radar altimeter, GNSS receiver, and an adequate communication link on Step 1: Green's functions are calculated in advance.…”