Tsunami Modelling with Static and Dynamic Tides in Drowned River Valleys with Morphological Constrictions

Wilson, Kaya M.; Power, Hannah E.

doi:10.1007/s00024-019-02411-0

Cited by 8 publications

(7 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This tool is based on the ANUDEM program developed by Hutchinson (1989) and generates a continuous digital elevation model based on point data that takes into account the hydrological correctness of the resulting raster. While this method was developed on the basis of subaerial water flow, it has also been used to effectively generate bathymetries for tsunami studies in other regions (Fraser et al, 2014;Darmawan et al, 2020;Wilson and Power, 2020). We note that the shallow shelf regions of the Lombok Strait were likely incised subaerially during the Late Holocene sea-level drop (Boekschoten et al, 2000), and their morphologies therefore likely reflect subaerial water flow processes.…”

Section: Bathymetrymentioning

confidence: 95%

Tsunami hazard in Lombok and Bali, Indonesia, due to the Flores back-arc thrust

Felix

Hubbard

Bradley

et al. 2022

Nat. Hazards Earth Syst. Sci.

View full text Add to dashboard Cite

Abstract. The tsunami hazard posed by the Flores back-arc thrust, which runs along the northern coast of the islands of Bali and Lombok, Indonesia, is poorly studied compared to the Sunda Megathrust, situated ∼250 km to the south of the islands. However, the 2018 Lombok earthquake sequence demonstrated the seismic potential of the western Flores Thrust when a fault ramp beneath the island of Lombok ruptured in two Mw 6.9 earthquakes. Although the uplift in these events mostly occurred below land, the sequence still generated local tsunamis along the northern coast of Lombok. Historical records show that the Flores fault system in the Lombok and Bali region has generated at least six ≥Ms 6.5 tsunamigenic earthquakes since 1800 CE. Hence, it is important to assess the possible tsunami hazard represented by this fault system. Here, we focus on the submarine fault segment located between the islands of Lombok and Bali (below the Lombok Strait). We assess modeled tsunami patterns generated by fault slip in six earthquake scenarios (slip of 1–5 m, representing Mw 7.2–7.9+) using deterministic modeling, with a focus on impacts on the capital cities of Mataram, Lombok, and Denpasar, Bali, which lie on the coasts facing the strait. We use a geologically constrained earthquake model informed by the Lombok earthquake sequence, together with a high-resolution bathymetry dataset developed by combining direct measurements from the General Bathymetric Chart of the Oceans (GEBCO) with sounding measurements from the official nautical charts for Indonesia. Our results show that fault rupture in this region could trigger a tsunami reaching Mataram in <9 min and Denpasar in ∼ 23–27 min, with multiple waves. For an earthquake with 3–5 m of coseismic slip, Mataram and Denpasar experience maximum wave heights of ∼ 1.6–2.7 and ∼ 0.6–1.4 m, respectively. Furthermore, our earthquake models indicate that both cities would experience coseismic subsidence of 20–40 cm, exacerbating their exposure to both the tsunami and other coastal hazards. Overall, Mataram is more exposed than Denpasar to high tsunami waves arriving quickly from the fault source. To understand how a tsunami would affect Mataram, we model the associated inundation using the 5 m slip model and show that Mataram is inundated ∼ 55–140 m inland along the northern coast and ∼230 m along the southern coast, with maximum flow depths of ∼ 2–3 m. Our study highlights that the early tsunami arrival in Mataram, Lombok, gives little time for residents to evacuate. Raising their awareness about the potential for locally generated tsunamis and the need for evacuation plans is important to help them respond immediately after experiencing strong ground shaking.

show abstract

Section: Bathymetrymentioning

confidence: 95%

Tsunami hazard in Lombok and Bali, Indonesia, due to the Flores back-arc thrust

Felix

Hubbard

Bradley

et al. 2022

Nat. Hazards Earth Syst. Sci.

View full text Add to dashboard Cite

show abstract

“…Although our techniques are general, the probabilistic inundation hazard results presented here only reflect PTHA18 thrust scenarios on the Kermadec-Tonga source zone, and neglect outer-rise earthquakes, more distant earthquake sources, and other sources such as landslides or volcanoes. The model does not account for dynamic tides (Wilson & Power, 2020), future mean-sea-level changes (Sepúlveda et al, 2021), or other sources of prediction errors in nonlinear shallow water models (Bosserelle et al, 2020;Tonini et al, 2021). While sufficient to demonstrate the performance of our offshore-to-onshore Monte-Carlo techniques, the probabilistic inundation results imply large uncertainties in the thrust sources.…”

Section: Discussionmentioning

confidence: 99%

“…Scenarios were run with an initial (preearthquake) sea-level of 0 m, and separately 0.8 m, to approximate the mean-sea-level and monthly tidal maxima at Tongatapu. This gives some insight into the importance of tides; a more comprehensive treatment of tides is beyond the scope of this study (Lane et al, 2012;Adams et al, 2015;Wilson & Power, 2020;González et al, 2021).…”

Section: Application To Probabilistic Inundation Computa-tion 41 Tsunami Scenarios and Inundation Computationmentioning

confidence: 99%

From offshore to onshore probabilistic tsunami hazard assessment via efficient Monte-Carlo sampling

Davies¹,

Weber²,

Wilson³

et al. 2022

Preprint

View full text Add to dashboard Cite

Offshore Probabilistic Tsunami Hazard Assessments (offshore PTHAs) provide large-scale analyses of earthquake-tsunami frequencies and uncertainties in the deep ocean, but do not provide high-resolution onshore tsunami hazard information as required for many risk-management applications. To understand the implications of an offshore PTHA for the onshore hazard at any site, in principle the tsunami inundation should be simulated locally for every scenario in the offshore PTHA. In practice this is rarely feasible due to the computational expense of inundation models, and the large number of scenarios in offshore PTHAs. Monte-Carlo methods offer a practical and rigorous alternative for approximating the onshore hazard, using a random subset of scenarios. The resulting Monte-Carlo errors can be quantified and controlled, enabling high-resolution onshore PTHAs to be implemented at a fraction of the computational cost. This study develops novel Monte-Carlo sampling approaches for offshore-to-onshore PTHA. Modelled offshore PTHA wave heights are used to preferentially sample scenarios that have large offshore waves near an onshore site of interest. By appropriately weighting the scenarios, the Monte-Carlo errors are reduced without introducing any bias. The techniques are applied to a high-resolution onshore PTHA for the island of Tongatapu in Tonga. In this region, the new approaches lead to efficiency improvements equivalent to using 4-18 times more random scenarios, as compared with stratified-sampling by magnitude, which is commonly used for onshore PTHA. The greatest efficiency improvements are for rare, large tsunamis, and for calculations that represent epistemic uncertainties in the tsunami hazard. To facilitate the control of Monte-Carlo errors in practical applications, this study also provides analytical techniques for estimating the errors both before and after inundation simulations are conducted. Before inundation simulation, this enables a proposed Monte-Carlo sampling scheme to be checked, and potentially improved, at minimal computational cost. After inundation simulation, it enables the remaining Monte-Carlo errors to be quantified at onshore sites, without additional inundation simulations. In combination these techniques enable offshore PTHAs to be rigorously transformed into onshore PTHAs, with full characterisation of epistemic uncertainties, while controlling Monte-Carlo errors.

show abstract

“…All the points are then interpolated using the 'Topo to Raster' tool in ArcGIS which is based on the ANUDEM model 24 designed to generate elevation models with hydrologically correct morphology. Although this method was developed for subaerial water flow, it has been effectively used in recent tsunami numerical modeling studies [25][26][27] . The geoprocessing workflow of the whole interpolation process, from the random point extraction to the bathymetry interpolation, is semi-automated using the visual programming language ModelBuilder in ArcGIS.…”

Section: Bathymetric Data Points For Interpolationmentioning

confidence: 99%

Sensitivity Analysis of Tsunami Heights to Shallow Bathymetric Resolution

Felix

Hubbard

Wilson

et al. 2023

Preprint

View full text Add to dashboard Cite

We examined how variations in bathymetric resolution affect simulated coastal tsunamis. We used 1-m resolution LiDAR datasets to generate resampled bathymetries with 5, 10, 20, 30, 40, 50, 100, 200, and 300 m resolutions, and added GEBCO data in the comparison. Tsunami waves offshore were generated by setting up an instantaneous rupture sourced from a hypothetical fault model. We used the COMCOT software to model tsunami propagation towards the coas. Using the 5 m bathymetry as the reference model, we observed that datasets with 10 – 50 m resolutions can reproduce tsunamis reasonably well. The maximum heights are overestimated by ≤5% or underestimated by ≤10%, and the first wave arrival time is ∼10%earlier than expected. Coarser bathymetries show an increasing trend of height underestimation, with the GEBCO model underestimating it by as much as 70%. Coarser bathymetries have more variable first wave arrival time, either ≤20% later or ≤10% earlier. Overall, a reasonably accurate result can be achieved using a bathymetric resolution in the 10 m – 50 m range, and is achievable with reasonable computational efficiency. This study highlights the importance of shallow bathymetry in the numerical modeling of tsunami propagation.

show abstract

Tsunami Modelling with Static and Dynamic Tides in Drowned River Valleys with Morphological Constrictions

Cited by 8 publications

References 33 publications

Tsunami hazard in Lombok and Bali, Indonesia, due to the Flores back-arc thrust

Tsunami hazard in Lombok and Bali, Indonesia, due to the Flores back-arc thrust

From offshore to onshore probabilistic tsunami hazard assessment via efficient Monte-Carlo sampling

Sensitivity Analysis of Tsunami Heights to Shallow Bathymetric Resolution

Contact Info

Product

Resources

About