Tsunami Inundation Simulation Research Articles

Analysis of the effects of urban micro-scale vulnerabilities on tsunami evacuation using an agent-based model – case study in the city of Iquique, Chile

Abstract. The occurrence of mega-tsunamis over the last couple of decades has greatly increased the efforts of the research community and practitioners to work hand in hand to reduce risks from these highly destructive threats. Protecting the population through evacuation is the best alternative for avoiding loss of life in the wake of the occurrence of a tsunamigenic earthquake. Therefore, guaranteeing the proper state of evacuation routes is very important to ensuring appropriate movement to the safe zones. This study carries out a detailed analysis of possible evacuation scenarios, considering the actual state of the escape routes of Iquique, a Chilean city prone to tsunamis, with a substantial number of urban micro-scale vulnerabilities, i.e., elements that obstruct or complicate pedestrian flow. The quantification of the delay in evacuation processes resulting from the presence of urban micro-vulnerabilities is carried out through micro-scale agent-based model (ABM) simulations. In addition, these results are integrated with high-resolution tsunami inundation simulations, allowing for an estimation of the potential number of people that the tsunami may reach under different scenarios by emulating the dynamics and behavior of the population and the decision-making regarding the starting time of the evacuation.

System Development for Tsunami Evacuation Drill Using ICT and Tsunami Inundation Simulation Data

This study aims to consider the effects and problems of a tsunami evacuation drill support system that visualizes dynamic tsunami data and evacuees’ locations. The system was developed and operated during a tsunami evacuation drill experiment. The location information application transmits evacuees’ locations in real time using the GPS and network functions of a multi-function terminal. The web application visualizes tsunami data and evacuees’ locations with animation on a web map using WebGIS. By operating the system in the tsunami evacuation experiment, the study could immediately evaluate the evacuation drills through real-time visualization of the evacuees’ actions. Feedback, including the results and evaluations of the evacuation drills, was provided to the participants. Before receiving feedback, 50% of the participants positively evaluated the drill results. However, 42.1% of the participants changed their evaluation to negative after receiving feedback. Additionally, by emphasizing the speed of action during evacuation as one of the important factors for quick evacuation, the system helped to alter participants’ disaster prevention awareness.

Integrated tsunami risk framework considering agent-based evacuation modelling: The case of Saga, Kochi Prefecture, Japan

This study develops an integrated tsunami risk framework combining stochastic tsunami hazard and agent-based evacuation modelling. The framework is applied to the case of Saga, Kochi, Japan, with a population of ∼ 2,200 anticipated to experience significant tsunami events (∼ M9.0). First, stochastic earthquake source models are generated for two values of magnitudes (M8.8 and M9.0) and used to carry out stochastic tsunami inundation simulations. Agent-based tsunami evacuation modelling using MATSim is then performed by considering four mode scenarios: single mode (pedestrian and car) and two multimodal scenarios (mix of car and pedestrian). The stochastic tsunami simulations and agent-based evacuation modelling results are integrated to estimate the risk. The effect of existing tsunami evacuation points and tsunami evacuation towers on risk reduction is also assessed. Such an integration framework is finally used to recommend tsunami mitigation strategies in the tsunami-prone regions. Results show that a significant tsunami hazard (i.e., tsunami depth up to 15 m) is expected in the Saga district, with an arrival time between 5 and 30 min. In addition, the evacuation points on higher grounds effectively save local residents' lives, as shown by the small number of affected people, specifically for the pedestrian and multimodal models (i.e. 10-100 people, excluding the car model). However, up to ∼ 1,000 people may get affected if car is the sole mode of evacuation. Therefore, the coastal community is recommended to evacuate on foot. Finally, identifying and securing sufficient higher grounds and vertical evacuation points are essential for risk reduction.

Evaluation of reduced computational approaches to assessment of tsunami hazard and loss using stochastic source models: Case study for Tofino, British Columbia, Canada, subjected to Cascadia megathrust earthquakes

Probabilistic tsunami hazard and risk analyses are important decision support tools in developing tsunami risk reduction strategies and actions for coastal communities. A stochastic source modeling method facilitates the consideration of uncertainties associated with earthquake rupture processes. However, the computational costs are high when inland tsunami inundation and building damage need to be evaluated accurately. To develop a practical solution by keeping the computational requirements at a manageable level, probabilistic tsunami hazard analysis based on low-resolution tsunami simulations but considering a wide range of possible earthquake ruptures can be used to identify smaller sets of stochastic rupture models for target probability levels. These identified stochastic rupture models can be used to obtain the estimates of tsunami building loss by running high-resolution tsunami inundation simulations. A case study is set up for Tofino, British Columbia, Canada, under the potential tsunami threat from the Cascadia megathrust earthquakes to investigate the correlation between the maximum modeled tsunami wave amplitudes at offshore locations and the tsunami building loss. A practical solution is proposed to obtain the tsunami risk estimates based on a limited number of high-resolution tsunami inundation simulations, thus reducing the computational costs for the probabilistic tsunami risk analysis. The effectiveness of the approach is demonstrated by comparing the median value of the tsunami risk estimates from 20 stochastic rupture model simulations that are selected based on probabilistic tsunami hazard analysis for a representative offshore location using the low-resolution tsunami simulations (i.e. 270 m grids) with the full probabilistic tsunami risk analysis of the target building portfolio based on the 1200 high-resolution tsunami simulations (i.e. 5 m grids).

Simulation of Tsunami Inundation for the Island of Martinique to Nearby Large Earthquakes

ABSTRACT In this article, we estimate the tsunami hazard in Martinique due to tsunamis generated by earthquakes associated with the Lesser Antilles subduction zone. Using a deterministic approach based on reliable earthquake scenarios, we use high-resolution bathymetric and topographic data to model tsunami propagation and inundation with Cornell Multi-grid Coupled Tsunami model. An extreme earthquake subduction scenario of magnitude Mw 8.0 is tested, and a further realistic scenario of lower magnitude Mw 7.5, thus of different tsunami frequency content, is also processed to test the possible appearance of bay resonances. We find that the western coast of the island is relatively sheltered, because it represents a shadow area to diffraction, in particular, for the major city of Fort de France. Because of its very gentle slope, the eastern coast is prone to numerous floodings with meter scale wave amplitudes; most of the inundated zones consist of mangroves and geological depressions t are naturally regularly flooded by tides or storm surges. Hence such areas are often not exploited, the mangroves being let in their natural state, enhancing the protection of the surrounding communities. However, some strategic inhabited areas are subject to severe inundation. Finally, comparing our results with studies of the 1755 Lisbon transoceanic tsunami reveals a tsunami hazard close to our local Mw 7.5 scenario. It suggests the possibility to generalize our local tsunami hazard assessment in Martinique to other tsunami contexts and enlarge its validity. This issue is crucial for minimizing the efforts and increasing the efficiency of tsunami preparedness.

Subgrid-scale modeling of tsunami inundation in coastal urban areas

Numerical tsunami inundation simulations using high-resolution (HR) topographical data are important to predict tsunami damage in urban areas at individual building levels accurately but are challenging due to the high computational cost. To address this issue, a subgrid-scale (SGS) model of tsunami inundation, called the individual drag force model (iDFM), is developed. In this model, the sum of the building drag forces in a computational mesh is fed back to the flow field by taking into account spatial information about multiple structures in the mesh. To evaluate the model performance, idealized numerical experiments using simple urban topography with several types of spatial layout patterns and hindcast physical experiments focusing upon Onagawa Town affected by the 2011 Tohoku, Japan tsunami as a historical event are conducted. Results are compared with HR tsunami simulations using building-resolved topographical data, called the structure resolving model (SRM). In general, the iDFM (and other SGS models) characterizes the effects of structures as resistance elements that reduce the fluid velocity in momentum conservation. On the other hand, the SRM evaluates these effects as topography and feeds them back into not only momentum conservation but also mass conservation and wet/dry boundary conditions. Therefore, the iDFM can model the overall inundation characteristics, such as the limits of inundation, more than 10 2 times efficiently compared with the SRM, although it cannot capture local phenomena driven by structures, such as surface rising due to blocking and contracting current between structures. In both numerical and historical tsunami (Onagawa) cases, there were small differences between the modeled inundation characteristics, such as the maximum surface elevation and fluid velocity, and the time series of inundation leading edges determined by the iDFM due to the computational grid cell sizes. The observed differences between the idealized numerical experiment and the historical tsunami case can be affected by the drag coefficient and the Froude number during the tsunami run-up.

Quantifying effects of explicit representation of buildings in tsunami inundation simulations

One of the critical steps in quantifying tsunami hazard is modelling of inundation. There are many factors influencing the complex inundation process, including the role played by features such as buildings affecting flow patterns which, if not simulated well, can affect the accuracy of tsunami intensity measure (IM) estimates (e.g. flow depth) and consequently, the reliability of outputs produced (e.g. economic loss estimates) by other models that utilise the estimated IM. In this paper, the effects of two alternative approaches to represent buildings in inundation modelling are investigated: (a) Equivalent Surface Roughness (ESR) approach, in which buildings and other ground surface features are removed and their effects on tsunami flows are approximated by spatially averaged surface roughness values; and (b) Explicitly Represented Building (ERB) approach, in which buildings are explicitly presented in the simulations to directly influence tsunami inundation. Using comparative simulations, this study quantifies the effects of explicit representation of buildings in inundation modelling on tsunami flow depth estimates and investigate how such effects consequently influence loss modelling results. We assess four plausible major earthquake-triggered tsunami scenarios for Napier, New Zealand. The modelling results suggest that the ERB approach better captures tsunami flow patterns and hence provides more realistic hazard and loss estimates. However, the difference in the estimated loss arising from potential direct damage caused by tsunami inundation (i.e. ERB vs. ESR) is shown to reduce in scenarios causing large-scale inundation, both in terms of severity and spatial extent, over the built-up area in the study region.

Simulated effectiveness of coastal forests on reduction in loss of lives from a tsunami

Although a substantial body of research has investigated the impacts of coastal vegetation on tsunami propagation over land, the effectiveness of coastal forests in reducing the number of expected casualties behind them has rarely been evaluated. Thus, this study investigates the effectiveness of coastal forests in reducing tsunami-related casualties using an agent-based evacuation simulation model. A tsunami propagation and inundation simulation model that considers vegetation-induced resistance to the flow was first developed and used to simulate the inundation observed at Shobutahama Beach in Miyagi Prefecture, Japan, during the 2011 Tohoku Tsunami. The results confirmed that the model is able to simulate the effects of coastal forests with relatively good accuracy. Then, this agent-based tsunami evacuation model was used to simulate evacuation that considers the implementation of coastal forests and other countermeasures (e.g., coastal dykes and evacuation signs) to reduce casualty rates. When coastal forests alone were considered the simulated casualty rates were reduced by a maximum of around 54% (compared with the case when no countermeasures were contemplated). However, a more significant reduction in casualty rates (a maximum of around 97%) was achieved when a coastal dyke capable of withstanding tsunami overflow was constructed. Furthermore, considering a combination of coastal forests and the construction of a dyke was shown to be more effective than either countermeasure alone, indicating the importance of implementing combined strategies to minimize the number of casualties due to a major tsunami event.

Numerical Simulation of Urban Inundation Processes and Their Hydraulic Quantities – Tsunami Analysis Hackathon Theme 1 –

The detailed understanding of tsunami hazard risk using numerical simulations requires a numerical model that can accurately predict tsunami inundation phenomena on land. In such models, the structural effects are indirectly considered using the variation of bottom roughness as a proxy for the differences in building densities. Only a few studies have conducted intermodel tests to investigate tsunami inundation in complex coastal urban cities. During the tsunami analysis hackathon held in September 2020, eight research groups met to have a detailed discussion on the current urban inundation problems. In this study, we conducted an intermodel comparison of the numerical tsunami models, using the data from physical experiments that were performed on a detailed urban model. Our objective was to investigate the necessary conditions of an accurate numerical model based that can ensure high reproducibility and practicality. It was confirmed that the accuracy of topographic data is an important parameter for tsunami inundation simulations in complex urban areas. Based on the computational cost and accuracy, we suggest that a resolution of 1 cm of topographic data is a sufficient condition for tsunami inundation simulations on 1/250 scale model.

Analysis of Tsunami Disaster Risk for a Petroleum Refinery Plant at Tsunami Prone Area

A Petroleum Refinery Plant is located in the tsunami prone area at the southern coast of Central Java, Indonesia. The potential mega thrust earthquake, along subduction zone of southern coast of Java, has been identified to have moment magnitude as maximum as Mw = 8.7. The worst scenario due to this earthquake will potentially generate 5.3m to 8.6m tsunami height along the coast within 30 minutes and will inundate one to two kilometres inland of the refinery complex. In this regard, a comprehensive investigation on potential tsunami hazard, level of vulnerability, and tsunami risk potential were carried out. The investigation includes collection and analysis data of detailed topography, bathymetry, land covering and land use, availability of protective structure as well as disaster contingency plan, field ground check data verification, awareness questionnaire, etc. The investigation output includes numerical tsunami inundation simulation, tsunami hazard index, vulnerability index, capacity index, and tsunami risk index for all area of refinery unit. It is concluded that: 1) the main location of refinery complex with considerable numbers of tanks is vulnerable to high tsunami hazard index, and 2) the capacity index in all area are mostly between low to mid-level.

Multi-hazard earthquake-tsunami loss estimation of Kuroshio Town, Kochi Prefecture, Japan considering the Nankai-Tonankai megathrust rupture scenarios

The Nankai-Tonankai Trough is the primary source of major subduction earthquakes in western and central Japan, and the preparedness against future Nankai-Tonankai megathrust subduction events is of critical importance. This study develops a novel multi-hazard catastrophe model for the future Nankai-Tonankai megathrust subduction earthquake and tsunami based on a stochastic earthquake source modeling approach, and applies it to Kuroshio Town, Kochi Prefecture, Japan, that faces significant seismic-tsunami hazards due to the Nankai-Tonankai subduction earthquakes. The earthquake-tsunami catastrophe model incorporates the stochastic rupture sources, spatially correlated ground motion fields, tsunami inundation simulations, detailed building portfolio data, seismic and tsunami fragility models, and building damage cost estimation. It produces the multi-hazard and single-hazard loss distributions, accompanied by detailed earthquake rupture scenarios, shaking-tsunami hazard intensity distributions, and building damage distributions. The earthquake-tsunami loss estimation results for Kuroshio Town indicate that the tsunami loss tends to increase with the magnitude more significantly than the shaking loss and contributes more towards the increase in the multi-hazard total loss with the earthquake magnitude. Importanly, the new multi-hazard tool facilitates the identification of critical multi-hazard loss scenarios and leads to integrated hazard-risk maps that are particularly useful for disaster risk reduction and management purposes.

A Source Clustering Approach for Efficient Inundation Modeling and Regional Scale Probabilistic Tsunami Hazard Assessment

For coastal regions on the margin of a subduction zone, near-field megathrust earthquakes are the source of the most extreme tsunami hazards, and are important to handle properly as one aspect of any Probabilistic Tsunami Hazard Assessment (PTHA). Typically, great variability in inundation depth at any point is possible due to the extreme variation in extent and pattern of slip over the fault surface. In this context, we present an approach to estimating inundation depth probabilities (in the form of hazard curves at a set of coastal locations) that consists of two components. The first component uses a Karhunen-Loeve expansion to express the probability density function (PDF) for all possible events, with PDF parameters that are geophysically reasonable for the Cascadia Subduction Zone (CSZ). It is then easy and computationally cheap to generate a large $N$ number of samples from this PDF; doing so and performing a full tsunami inundation simulation for each provides a brute force approach to estimating probabilities of inundation. However, to obtain reasonable results, particularly for extreme flooding due to rare events, $N$ would have to be so large as to make the tsunami simulations prohibitively expensive. The second component tackles this difficulty by using importance sampling techniques to adequately sample the tails of the distribution and properly re-weight the probability assigned to the resulting realizations, and by grouping the realizations into a small number of clusters that we believe will give similar inundation patterns in the region of interest. In this approach, only one fine-grid tsunami simulation need be computed from a representative member of each cluster. We discuss clustering based on proxy quantities that are cheap to compute over a large number of realizations, but that can identify a smaller number of clusters of realizations that will have similar inundation depths. The fine-grid simulations for each cluster representative can also be used to develop an improved strategy, in which these are combined with cheaper coarse-grid simulations of other members of the cluster. We illustrate the methodology by considering two coastal locations: Crescent City, CA and Westport, WA.

Combination of school evacuation drill with tsunami inundation simulation: Consensus-making between disaster experts and citizens on an evacuation strategy

This paper aims to introduce an effective methodology for communicating a science-based tsunami risk scenario to non-expert citizens through consensus-making between disaster experts and non-experts, with the aid of four-way split-screen movie clips depicting evacuation scenarios. Action research on tsunami education in Zihuatanejo, Mexico found that a perception of tsunamis as catastrophic together with the one-directional nature of risk communication resulted in inaction on the part of non-experts in disaster preparedness, contrary to the expectations of experts. In other words, non-experts did not think that they could cope with a tsunami disaster and they perceived that as non-experts they themselves could not affect the tsunami risk scenario communicated to them by the experts. In response, movie clips simultaneously displaying a school evacuation drill and tsunami inundation simulation were developed. These movie clips are intended to serve as a tool in the process of establishing a school tsunami evacuation strategy by promoting consensus-making between experts and non-experts about the risk scenario, thereby helping to change the perception of a tsunami from a catastrophe that cannot be dealt with by non-experts to a realistic perception that non-experts can indeed help by engaging in their own tsunami risk preparedness activities. The developed movie clips were used at a workshop for stakeholders, including academics, local government, and teachers, with the aims of establishing scenario-based evacuation strategies and promoting the proactive implementation of preparedness activities by non-expert teachers. The study will contribute to establishing a mechanism for applying scientific knowledge to solving societal issues.

Reciprocal elevation and flow Green's functions and the simulation of nearshore tsunami inundation

In addition to the elevation Green's function which is known as the numerical Green's function in previous tsunami studies, a new type of Green's function for shallow water equations is proposed. This new Green's function is the flow response due to impulsive initial sea surface increase and is dubbed the flow Green's function. Based on the momentum equation, its reciprocity to sea surface response for impulsive initial flow is suggested and is shown numerically. That is, the x- and y-volume fluxes at the vulnerable city (x, y) caused by an impulsive increase of the unit sea surface η at the source point (xs, ys) are exactly the η response at (xs, ys) caused by an impulsive unit x- and y-volume fluxes at (x, y) multiplied by the negative gravitational acceleration and the water depth at (x, y). The later will be called a reciprocal flow Green's function. As reciprocal flow Green's functions include information on wave direction, by combing reciprocal elevation Green's functions (known as reciprocal Green's functions in previous tsunami studies), they can be used as an accurate boundary condition for the simulation of nearshore inundation. This new approach is proposed and compared with direct tsunami simulation for both normally (Case 1) and obliquely (Case 2) incident tsunamis. The accuracy of the new approach is similar to a direct simulation, and is a significant improvement compared with a simplified bell-shaped wave approach. The computer time is significantly reduced compared with direct simulations.

Using Hypothetical Tsunami Scenarios to Analyze Tsunami Inundation Characteristics in the Coastal City of Ulsan, South Korea

Kim, D.-S.; Jeong, Y.-H.; Lee, H.-Y.; Kim, D.-H., and Hong, S.-J., 2020. Using hypothetical tsunami scenarios to analyze tsunami inundation characteristics in the coastal city of Ulsan, South Korea. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1140–1145. Coconut Creek (Florida), ISSN 0749-0208.To establish a tsunami disaster prevention plan, including prior risk assessment and damage reduction for Ulsan in South Korea, a hypothetical scenario-based tsunami inundation simulation for 12 emergency evacuation areas was designed, and the inundation characteristics of the tsunami were analyzed. A hypothetical source 01 tsunami combined with a magnitude 9.0 earthquake affected the evacuation areas most significantly, while a hypothetical source 11 tsunami with a magnitude 7.5 earthquake had a relatively minor impact on the areas. In the Ilsan area of Ulsan, the hypothetical scenarios exhibited minimum and maximum inundation depths of 0.5 m and 6 m, respectively, and a maximum inundation area of about 206 km2. The tsunami inundation characteristics of the Ulsan area analyzed in this study will be useful for establishing an emergency action plan and countermeasures for tsunami situations.

Tsunami evacuation simulation for the District of Tofino, Vancouver Island, Canada

A large earthquake event generated from the nearby Cascadia Subduction Zone would possibly generate a significant tsunami event which could affect the west coast of Canada. In this study, to critically assess the effects of a tsunami on the District of Tofino on Vancouver Island, British Columbia, tsunami simulations were performed. As a result of tsunami propagation and inundation simulations, it was found that for earthquakes Mw9.0 or greater, the central part of the Esowista Peninsula on which Tofino is located will be completely inundated. The authors have also conducted tsunami evacuation simulations using an agent-based model developed by Takabatake et al. (2017). This evacuation model considered Tofino's large fluctuation in residents due to seasonal tourism in a number of selected scenarios. Using the model, the authors also conducted a sensitivity analysis to investigate effects of the change in evacuation behaviour on the mortality rate. The results showed that a significant number of casualties would occur in Tofino, especially if an earthquake was to occur at night. It was also shown to be important to consider the capacity of evacuation buildings when directing evacuees, especially the elderly. In addition, the present study clarified that the effects of evacuation start time and route choices on the mortality rate would vary significantly according to a population distribution scenario even in the same study area. It was thus highlighted that conducting sensitivity analysis under varied population distribution scenarios is important to understand properly the uncertainty associated with tsunami evacuation.

Frequency-dependent amplification of the Sanriku tsunamis in Ryori Bay

In the present study, the local tsunami amplification observed in Ryori Bay, located on the Sanriku coast of Japan, was investigated using numerical simulations. Large-scale tsunami propagation simulations and tsunami inundation simulations for the bay were systematically conducted to estimate and model the 2011, 1933, and 1896 tsunamis that occurred off the Sanriku coast and which resulted in large run-ups. The simulation results, which are moderately consistent with observations, presented larger run-up heights and inundations for the 1933 and 1896 tsunamis (which followed relatively small earthquakes) compared to those of the 2011 tsunami (which followed a larger earthquake). Furthermore, the frequency analysis indicated that the former two tsunamis comprised higher predominant components. A tsunami inundation simulation using parametrized synthetic waveforms was conducted to identify the contributing factors associated with the large amplification and run-ups. The results indicated that the predominant components are significantly amplified in the bay and the initial decrease in the water surface elevation prior to the primary waves of the two tsunamis leads to an increase in their run-up heights. Furthermore, the simulated waveforms of the tsunamis revealed that the 1933 and 1896 tsunamis had their wavefronts changed into a steep wavefront, i.e., a bore-like wave, during their wave developments in the bay, attributed to shoaling, narrowing bay width, and the nonlinear effect of the wave. These results, therefore, indicate that bores which are known to generate large run-up heights were generated in the bay during the two tsunamis.

Cascading Geological Hazards and Risks of the 2018 Sulawesi Indonesia Earthquake and Sensitivity Analysis of Tsunami Inundation Simulations

Multiple cascading hazards triggered by the 2018 Sulawesi, Indonesia, earthquake caused various compounding consequences. A major strike-slip fault movement with along-dip components resulted in intense ground shaking, liquefaction and lateral spreading, large-scale mudflows, and tsunamis. This paper presents observations of such multi-hazard effects on buildings and infrastructure in areas along Palu Bay, based on field reconnaissance work, and discusses the main causes of the disaster by focusing upon the combined effects of the cascading geological hazards. To evaluate the tsunami risk potential of the strike-slip event, tsunami simulations for the 2018 Sulawesi earthquake are performed by considering different model settings for spatial earthquake slip distribution, rake angle, astronomical tidal effect, and co-seismic ground deformation. The numerical results indicate that the co-seismic rupture of a moment magnitude 7.5 strike-slip earthquake, having notable dip components can generate damaging tsunami waves at coastal locations of Palu Bay. The conclusion has important implications for future tsunami hazard assessments in active seismic regions where major fault systems cut across a bay or into the sea.

High-Resolution Digital Elevation and Bathymetry Model for Tsunami Run-Up and Inundation Simulation in Penang

Many beaches in Penang island were severely inundated by the 26 December 2004 Indian Ocean mega tsunami with 57 deaths recorded. It is anticipated that the next big tsunami will cause even more damages to beaches in Penang. Hence, developing community resilience against the risks of the next tsunami is essential. Resilience entails many interlinked components, beginning with a good understanding of the inundation scenarios critical to community evacuation and resilience preparation. Inundation scenarios are developed from tsunami simulations involving all three phases of tsunami generation, propagation and run-up. Accurate and high-resolution bathymetric–topographic maps are essential for simulations of tsunami wave inundation along beaches. Bathymetric maps contain information on the depths of landforms below sea level while topographic maps reveal the elevation of landforms above sea level. Bathymetric and topographic datasets for Malaysia are, however, currently not integrated and are available separately and in different formats, not suitable for inundation simulations. Bathymetric data are controlled by the National Hydrographic Centre (NHC) of the Royal Malaysian Navy while topographic data are serviced by the Department of Survey and Mapping Malaysia (JUPEM). It is highly desirable to have seamless integration of high-resolution bathymetric and topographic data for tsunami simulations and for other scientific studies. In this paper, we develop a robust method for integrating the NHC bathymetric and JUPEM topographic data into a regularly-spaced grid system essential for tsunami simulation. A primary objective of this paper is to develop the best Digital Elevation and Bathymetry Model (DEBM) for Penang based upon the most suitable and accurate interpolation method for integrating bathymetric and topographic data with minimal interpolation errors. We analyze four commonly used interpolation methods for generating gridded topographic and bathymetric surfaces, namely (i) Kriging, (ii) Multiquadric (MQ), (iii) Thin Plate Spline (TPS) and (iv) Inverse Distance to Power (IDP). The study illustrated that the Kriging interpolation method produces an integrated bathymetric and topographic surface that best approximates the admiralty nautical chart of Penang essential for tsunami run-up and inundation simulations. Tsunami inundation scenarios critical to risk analysis and mitigation could then be developed using this DEBM for various earthquake scenarios, as presented in this paper for the 2004 Indian Ocean Tsunami.

Source Model for the Tsunami Inside Palu Bay Following the 2018 Palu Earthquake, Indonesia

AbstractOn 28 September 2018, a strike‐slip earthquake occurred in Palu, Indonesia, and was followed by a series of tsunami waves that devastated the coast of Palu Bay. The tsunami was recorded at the Pantoloan tide gauge station with a peak amplitude of ~2 m above the water level and struck at high tide. We use the Pantoloan tsunami waveform and synthetic aperture rada displacement data in a joint inversion to estimate the vertical displacement around the narrow bay. Our inversion result suggests that the middle of the bay was uplifted up to 0.8 m, while the other parts of the bay subsided by up to 1 m. However, this seafloor displacement model alone cannot fully explain the observed tsunami inundation. The observed tsunami inundation heights and extents could be reproduced by a tsunami inundation simulation with a source model that combined the estimated vertical displacement with multiple subaerial‐submarine landslides.