Effects of Artificial Structures on Grain Size and Characteristics of the 2018 Anak Krakatau Tsunami Deposits

Septriono Hari Nugroho, Purna Sulastya Putra, Amar, Mohammad Heidarzadeh

Research output: Contribution to journalArticlepeer-review

Abstract

This paper presents the first detailed analysis of grain size parameters and tsunami deposit of the 2018 Anak Krakatau tsunami, considering artificial structures such as buildings and roads. The deposition of tsunamis on land is extremely complex, involving contributions from both the hydrodynamics of tsunami flow propagation and the characteristics of the tsunami, as well as topographical conditions. In both local and detailed contexts, artificial structures can affect the formation of tsunami deposits. In this study, we focused on the effect of artificial structures on the characteristics of the 2018 Anak Krakatau tsunami deposits. Field observations showed that the remains of dikes, houses and asphalt roads significantly influenced the source, thickness, structure of tsunami deposits and grain size parameters. Tsunami deposits consisting of fine-grained material originated from the sediment on the seafloor. Tsunami deposits were thicker in areas closer to the part of the sea unaffected by artificial structures and exhibited a thinning trend inland. In general, the grain size of tsunami deposits is coarser than that of pre-tsunami deposits. Tsunami deposits predominantly exhibit an upward fining trend. Our study explains the key role of artificial structures in the formation of tsunami deposits and the sediment structure produced in coastal areas. A drastic change in the characteristics of the grain size parameters results from the presence of artificial structures. Overall, the tsunami deposit layers could have been better sorted. Significantly different sortation values were observed at sites located above the asphalt road. Similarly, kurtosis values showed an anomaly. The skewness value was inversely proportional to the average grain size in areas affected by artificial structures.

Original languageEnglish
JournalPure and Applied Geophysics
Early online date21 Aug 2024
DOIs
Publication statusE-pub ahead of print - 21 Aug 2024

Data Availability Statement

The Anak Krakatau 2018 tsunami deposits were taken using a 60-cm geoslicer along the transect during the field survey carried out on 2–10 January 2020. During the survey, precise measurements of topographic elevation were made using a laser range finder device, and the results were adjusted for tidal height. To produce a clear-resolution display, the map was produced by merging survey data with Landsat and Google Earth Pro imaging data. Meanwhile, we are using Global-Mapper ver.18.1, QGIS 3.18.2. to process data. Research Center for Geological Disaster, The National Research and Innovation Agency provides survey equipment and laboratory instruments such as laser diffraction Mastersizer 2000 (Malvern Panalytical) for grain size analysis. The grain size data is available upon request.

Keywords

  • artificial structure
  • grain size analysis
  • the 2018 Anak Krakatau tsunami
  • Tsunami deposit

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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