Field Survey and Numerical Modelling of the December 22, 2018 Anak Krakatau Tsunami

Jose C. Borrero, Tubagus Solihuddin, Hermann M. Fritz, Patrick J. Lynett, Gegar S. Prasetya, Vassilios Skanavis, Semeidi Husrin, Kushendratno, Widjo Kongko, Dinar C. Istiyanto, August Daulat, Dini Purbani, Hadiwijaya L. Salim, Rahman Hidayat, Velly Asvaliantina, Maria Usman, Ardito Kodijat, Sangyoung Son, Costas E. Synolakis

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)

Abstract

On December 22, 2018, the eruption and flank collapse of the Anak Krakatau volcano generated a tsunami in the Sunda Strait causing catastrophic damage to uninhabited coastlines proximal to the source. Along the heavily populated shores of Banten and Lampung provinces in Java and Sumatra, tsunami waves caused severe damage, extensive inundation and more than 430 deaths. An international tsunami survey team (ITST) deployed 6 weeks after the event documented the tsunami effects including runup heights, flow depths and inundation distances, as well as sediment deposition patterns and impacts on infrastructure and the natural environment. The team also interviewed numerous eyewitnesses and educated residents about tsunami hazards. This ITST was the first to visit and document the extreme tsunami effects on the small islands in the Sunda Strait closest to Anak Krakatau (Rakata, Panjang, Sertung, Sebesi and Panaitan). Along the steep slopes of Rakata and Sertung islands, located less than 5 km from and facing directly towards the southwest flank of Anak Krakatau, all of the dense coastal vegetation was stripped to bare earth up to elevations of more than 80 m, while on the northeast tip of Sertung Island, facing away from the source, a single tree remained standing after flow depths of > 11 m above ground struck there. The runup distributions on the islands encircling Anak Krakatau highlight the directivity of the tsunami source suggesting that the collapse occurred towards the southwest. This manifested as tsunami runup of < 10 m on Sebesi Island, located 15 km northeast of the source, contrasting with tsunami flow heights > 10 m that stripped away coastal forests to bare rock for up to 400 m inland in the Ujung Kulon National Park, located 50 km to the south-southwest. Inundation and damage were mostly limited to within 400 m of the shoreline, likely the result of the relatively short wavelengths caused by the landslide generated tsunami. A significant variation in tsunami impact was observed along the shorelines of the Sunda Strait, with runup heights rapidly decreasing with distance from the inferred tsunami source. To model the event we applied a hot-start initial condition that roughly reproduced the measured tsunami runup heights along Rakata and Sertung. The waveforms were then propagated through the Sunda Straight using a Boussinesq-type wave model. The results showed a good fit to the observed heights along the Java and Sumatra coastlines, the northern coast of Panaitan Island and Ujung Kulon Nation Park. The model also produced an acceptable fit to the observed amplitudes at tide gauges. Despite the regional volcanic and tsunamigenic history of the region, and 6-months of eruptive activity prior to the event, the tsunami largely caught the local population off guard. This further highlights the need for community-based education and awareness programs as essential to save lives in locales at risk from locally generated tsunamis.

Original languageEnglish
Pages (from-to)2457-2475
Number of pages19
JournalPure and Applied Geophysics
Volume177
Issue number6
DOIs
Publication statusPublished - 2020 Jun 1

Bibliographical note

Funding Information:
The team would like to acknowledge United States National Science Foundation Award CMMI-1906162 for supporting this work. We also acknowledge the Indonesian Government for granting permission to conduct these important field surveys. This includes the Ministry of Research, Technology and Higher Education (MORTHE), Coordinating Ministry of Maritime Affairs, Ministry of Marine Affairs and Fisheries (MMAF), Center for Volcanology and Geological Hazard Mitigation, Agency for the Assessment and Application of Technology (BPPT) and the Office of Ujung Kulon National Parks. We acknowledge the Indonesian Tsunami Scientific Community (IATsI) and IOTIC/IOC-UNESCO Jakarta for the advice, support, and guide for conducting the field surveys. We are grateful to our guide from BALAWISTA Pantai Carita (Lifeguards Carita Beach), especially Pak Samsul and the boat captains and crew for helping the team access the offshore locations and getting us back home safely. JCB dedicates this paper to CTB. May your fascination with volcanoes and science stay with you always!

Funding Information:
The team would like to acknowledge United States National Science Foundation Award CMMI-1906162 for supporting this work. We also acknowledge the Indonesian Government for granting permission to conduct these important field surveys. This includes the Ministry of Research, Technology and Higher Education (MORTHE), Coordinating Ministry of Maritime Affairs, Ministry of Marine Affairs and Fisheries (MMAF), Center for Volcanology and Geological Hazard Mitigation, Agency for the Assessment and Application of Technology (BPPT) and the Office of Ujung Kulon National Parks. We acknowledge the Indonesian Tsunami Scientific Community (IATsI) and IOTIC/IOC-UNESCO Jakarta for the advice, support, and guide for conducting the field surveys. We are grateful to our guide from BALAWISTA Pantai Carita (Lifeguards Carita Beach), especially Pak Samsul and the boat captains and crew for helping the team access the offshore locations and getting us back home safely. JCB dedicates this paper to CTB. May your fascination with volcanoes and science stay with you always!

Publisher Copyright:
© 2020, Springer Nature Switzerland AG.

Keywords

  • Anak Krakatau
  • field survey
  • landslide
  • tsunami
  • volcano

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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