Evidence-Calibrated Numerical Model of December 22, 2018, Anak Krakatau Flank Collapse and Tsunami

Abstract

On December 22, 2018, a sector of the Anak Krakatau volcano edifice collapsed into the sea, generating a tsunami that hit the Sunda Strait coasts in Indonesia. The collapse followed a period of 6 months of volcanic activity that was insufficient to warn the tsunami-threatened coastal population. The Anak Krakatau tsunami resulted in hundreds of casualties, thousands of injured and displaced people, and massive coastal damage. This paper uses the tsunami records, the collected field survey data, and satellite imagery-based interpretations to develop a model of the Anak Krakatau flank failure and tsunami. We address the dynamics of the flank failure, the tsunami generation and propagation, and the coastal impact using evidence-calibrated numerical modelling. An in-house-developed multi-layer viscoplastic shallow-water numerical code is employed to simulate the Anak Krakatau collapse mass movement and the whole source-to-coast tsunami process. Our results suggest that a flank collapse scenario involving a volume of material of 0.135 km3 and occurring as a sequence of two failures fairly reproduces the local and regional tsunami records and survey data.