Post-Event Field Survey of the 22 December 2018 Anak Krakatau Tsunami

Abstract

On 22 December 2018, volcanic activity of Anak Krakatau, Indonesia, triggered a tsunami that caused more than 437 casualties on surrounding coastlines. Soon after the event, before the physical evidence of the tsunami disappeared, a postevent field survey was carried out. Measurements of tsunami inundation and impact are important to better model and understand the tsunami triggering processes to support future tsunami mitigation efforts. The impacted area on the western coast of Banten, Java Island, was surveyed to acquire tsunami inundation and run-up height data, together with field characteristics of the tsunami deposits. Data were acquired at 36 locations along three transects of tsunami deposits. From these, the maximum tsunami run-up height (up to 13 m) in the surveyed locations was identified on the southern part of the Banten Coast in the Tanjung Lesung area, an area located to the south of Anak Krakatau Volcano. The tsunami deposits were relatively thin along the transect, including a fining upward sequence without any clear evidence of fresh volcanic material, in disagreement with other reported volcano-induced tsunami deposits. Characteristics of the 2018 Anak Krakatau tsunami deposits are more similar to earthquake-induced tsunami deposits, hence complicating the paleotsunami reconstruction in Sunda Strait, where tsunami mechanisms are from both volcano and earthquakes along the Sunda subduction zone.