EGU2020-11838
https://doi.org/10.5194/egusphere-egu2020-11838
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Field Survey of the 2018 Anak Krakatau Tsunami on the Islands in the Sunda Strait

Hermann M. Fritz1, Tubagus Solihuddin2, Costas E. Synolakis3,4, Gegar S. Prasetya5, Jose C. Borrero6, Vassilis Skanavis3,4, Semeidi Husrin2, Widjo Kongko7, Dinar C. Istiyanto7, August Daulat2, Dini Purbani2, Hadiwijaya Salim2, Rahman Hidayat8, Velly Asvaliantina8, Maria Usman5, and Ardito Kodijat9
Hermann M. Fritz et al.
  • 1Georgia Institute of Technology, School of Civil and Environmental Engineering, Atlanta, GA 30332, United States of America (fritz@gatech.edu)
  • 2Marine Research Centre, Ministry of Marine Affairs and Fisheries, Jakarta 14430, Indonesia
  • 3Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089, USA
  • 4Department of Environmental Engineering, Technical University of Crete, Chanea 73100, Greece
  • 5Indonesian Tsunami Scientific Community, Jakarta 12950, Indonesia
  • 6eCoast Ltd., 47 Cliff St., Raglan 3225, New Zealand
  • 7Agency for the Assessment and Application of Technology (BPPT), Yogyakarta 55284, Indonesia
  • 8Coordinating Ministry for Maritime Affairs – Jakarta 10340, Indonesia
  • 9IOC-UNESCO, Indian Ocean Tsunami Information Center (IOTIC), Jakarta 12110, Indonesia

On December 22, 2018, an eruption and partial collapse of the Anak Krakatau volcano generated a tsunami in the Sunda Strait. The tsunami caused catastrophic damage and more than 400 deaths in coastal regions of the Sunda Strait in Lampung (Sumatra) and Banten (Java). An international tsunami survey team (ITST) was deployed 6 weeks after the event to document flow depths, runup heights, inundation distances, sediment deposition, impact on the natural environment and infrastructure. The 4 to 9 February 2019 ITST focused on islands in the Sunda Strait: Rakata, Panjang, Sertung, Sebesi and Panaitan. The survey team logged more than 500 km by small boat. The collected survey data includes almost 100 tsunami runup and flow depth measurements. The tsunami impact peaked along steep slopes facing Anak Krakatau with an 85 m runup on Rakata and an 83 m runup on Sertung. The extreme runup heights were within less than 5 km of Anak Krakatau. Flow depth reached more than 11 m above ground on Sertung where a boat landing was possible and trees remained standing. On Sebesi Island located 15 km northeast of the source tsunami runup heights remained below 10 m. In contrast, tsunami heights exceeding 10 m were observed in the Ujung Kulon National Park located 50 km southwest of Anak Krakatau. The runup distributions on the islands encircling Anak Krakatau highlight the directivity of the tsunami source with the Anak Krakatau collapse towards the southwest. Inundation and damage were mostly limited to within 400 m of the shoreline given the relatively short wavelengths of volcanic tsunamis. Significant variation in tsunami impact was observed along shorelines of the Sunda Strait with tsunami heights rapidly decreasing with distance from the point source. Field observations, drone videos, and satellite imagery are presented. The team interviewed numerous eyewitnesses based on established protocol and educated residents about tsunami hazards. The tsunami caught the locals off guard despite the history and a six-month long eruptive activity in the lead up. Community-based education and awareness programs are essential to save lives in locales at risk from locally generated tsunamis. The 500 m initial height difference between the 1883 Krakatau and 2018 Anak Krakatau collapses provides a perspective on these two tsunamis. Remaining and future tsunami hazards will be affected by volcanic edifice regrowth.

How to cite: Fritz, H. M., Solihuddin, T., Synolakis, C. E., Prasetya, G. S., Borrero, J. C., Skanavis, V., Husrin, S., Kongko, W., Istiyanto, D. C., Daulat, A., Purbani, D., Salim, H., Hidayat, R., Asvaliantina, V., Usman, M., and Kodijat, A.: Field Survey of the 2018 Anak Krakatau Tsunami on the Islands in the Sunda Strait, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11838, https://doi.org/10.5194/egusphere-egu2020-11838, 2020

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Presentation version 1 – uploaded on 06 May 2020
  • CC1: Water depth at the gauge stations, Thomas Zengaffinen, 06 May 2020

    Hi Hermann. Great job and pictures on your field survey. Did you also have a look at the gauge stations? Do you know the water depth where they are stationed?

    Greetings,
    Thomas Zengaffinen

    • AC1: Reply to CC1, Hermann M. Fritz, 06 May 2020

      The permanent Indonesian gauges (data from agency BIG) are in ports and harbors. We focused on the Islands. I did not visit the permanent gauge locations. Some of the Indonesian co-authors may have visited the gauge locations independently. The gauge data, locations and instrument descriptions are available from the Indonesia agency BIG.

      Post event JRC (Alessandro Annunziato) installed some temporary gauges - one on Sebesi that we visited in February 2020 and one near Carita on Banten that Gegar and I visited in September 2020.

      • AC2: Reply to AC1, Hermann M. Fritz, 06 May 2020

        February 2019 and September 2019 ;-)

      • CC2: Reply to AC1, Thomas Zengaffinen, 07 May 2020

        Okay, thanks.