Numerical modeling of the subaerial landslide source of the 22 December 2018 Anak Krakatoa volcanic tsunami, Indonesia

Heinrich

et al. 2019

Pure Appl. Geophys.

On the evening of December 22, 2018, the coasts of the Sunda Strait, Indonesia, were hit by a tsunami generated by the collapse of a part of the Anak Krakatau volcano. Hundreds of people were killed, thousands were injured and displaced. This paper presents a preliminary modeling of the volcano flank collapse and the tsunami generated based on the results of a 2D depth-averaged coupled model involving a granular rheology and a Coulomb friction for the slide description and dispersive effects for the water flow part.With a reconstructed total volume (subaerial and submarine) of the landslide of 150 million m 3 inferred from pre and post-collapse satellite and aerial images, the comparison of the simulated water waves with the observations (tide gauges located all around the strait, photographs and field surveys) is satisfactory. Due to the lack of information for the submarine part of the landslide, 2 Alexandre Paris et al. the reconstructed submarine slope is assumed to be approximately constant. A significant time delay on the results and particularly in the Bandar Lampung Bay could be attributed to imprecisions of bathymetric data. The sensitivity to the basal friction and to dispersive effects is analyzed through numerical tests. Results show that the influence of the basal friction angle on the simulated wave heights decreases with distance and that a value of 2°gives consistent results with the observations. The dispersive effects are assessed by comparing water waves simulated by a shallow water model and a Boussinesq model. Simulations with frequency dispersion produce longer wave periods and smaller wave amplitudes in the Sunda Strait and particularly in deep waters.

Section: Discussionsupporting

confidence: 90%

Section: Resultssupporting

confidence: 79%

Section: Discussionsupporting

confidence: 84%

Section: Until Now One Of the Deadliest Recent Landslide Tsunamis Ismentioning

confidence: 99%

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The December 22, 2018 Anak Krakatau, Indonesia, Landslide and Tsunami: Preliminary Modeling Results

Heinrich

et al. 2019

Pure Appl. Geophys.

Nat. Hazards Earth Syst. Sci.

“…The actual area affected by the 22 December event is consistent with their model but different in magnitude due to the use of the worstcase scenario in the simulation. The numerical modeling of the December 2018 Anak Krakatau tsunami was performed by Heidarzadeh et al (2020), while Muhari et al (2019) conducted field surveys of this event to record tsunami run-up along the coasts of the Sunda Strait.…”

Section: Introductionmentioning

confidence: 99%

Run-up, inundation, and sediment characteristics of the 22 December 2018 Sunda Strait tsunami, Indonesia

Widiyanto

Hsiao

Chen

et al. 2020

Abstract. A tsunami caused by a flank collapse of the southwest part of the Anak Krakatau volcano occurred on 22 December 2018. The tsunami affected the coastal areas located at the edge of the Sunda Strait, Indonesia. To gain an understanding of the tsunami event, field surveys were conducted a month after the incident. The surveys included measurements of run-up height, inundation distance, tsunami direction, and sediment characteristics at 20 selected sites. The survey results revealed that the run-up height reached 9.2 m in Tanjungjaya and an inundation distance of 286.8 m was found at Cagar Alam, part of Ujung Kulon National Park. The tsunami propagated radially from Anak Krakatau and reached the coastal zone with a direction between 25 and 350∘ from the north. Sediment samples were collected at 27 points in tsunami deposits with a sediment thickness of 1.5–12.7 cm. The average distance from the coast of the area with significant sediment deposits and the deposit limit are 45 % and 73 % of the inundation distance, respectively. Sand sheets were sporadic, highly variable, and highly influenced by topography. Grain sizes in the deposit area were finer than those at their sources. The sizes ranged from fine sand to boulders, with medium sand and coarse sand being dominant. All sediment samples had a well-sorted distribution. An assessment of the boulder movements indicates that the tsunami run-up had minimum velocities of 4.0–4.5 m s−1.

A Tsunami Warning System based on Offshore Bottom Pressure Gauges and Data Assimilation for Crete Island in the Eastern Mediterranean Basin

Wang

Heidarzadeh

Satake

et al. 2020

Preprint

Self Cite

The Eastern Mediterranean Basin (EMB) is under the threat of tsunami events triggered by various causes including earthquakes and landslides. We propose a deployment of Offshore Bottom Pressure Gauges (OBPGs) around Crete Island, which would enable tsunami early warning by data assimilation for disaster mitigation. Our OBPG network consists of 12 gauges distributed around Crete Island, with a 100-km interval, based on three criteria to select the locations. The station network must have a good azimuthal coverage and have enough (>50 km) distance from the coast, and the OBPGs are placed at the locations where the most energetic wave dynamics occur, which is confirmed by Empirical Orthogonal Function (EOF) analysis of pre-calculated tsunami scenarios. We demonstrate three test cases comprising a hypothetical seismogenic tsunami in east Sicily, a hypothetical landslide tsunami in the Aegean Sea, and the real tsunami event of the May 2020 off the Crete earthquake. Our designed OBPG network achieves an accuracy of 88.5% for the hypothetical seismogenic tsunami and 87.3% for the hypothetical landslide tsunami with regard to the forecasting of first tsunami peak. For the real event of May 2020, it predicts the tsunami arrival at tide gauge NOA-04 accurately; the observed and forecasted amplitudes of the first wave are 5.0 cm and 4.5 cm, respectively. The warning lead time for the May 2020 event was ~10 min. Therefore, our results reveal that the assimilation of OBPG data can satisfactorily forecast the amplitudes and arrival times for tsunamis in the EMB.