Tsunami Hazard Assessment Research Articles

Characterizing the spatial correlation of coseismic slip distributions: A data driven Bayesian approach

Summary The spatial correlation of coseismic slip is a necessary input for generating stochastic seismic rupture models, which are commonly employed in seismic and tsunami hazard assessments. To date, the spatial correlation of individual earthquakes is characterized using finite fault models by finding the combination of parameters of a von Kármán autocorrelation function that best fits the observed autocorrelation function of the finite fault model. However, because a priori spatial correlation conditions (i.e., not in the data) are generally applied in finite fault model generation, the results obtained using this method may be biased. Additionally, robust uncertainty estimates for spatial correlations of coseismic slip are generally not performed. Considering these limitations in the classic method, here, a method is developed based on a Bayesian formulation of Finite Fault Inversion (FFI) with positivity constraints. This method allows for characterizing the spatial correlation of coseismic slip and its uncertainties for an earthquake by using samples of coseismic slip from a posterior probability density function (PDF). Furthermore, a Bayesian model selection criterion called Akaike Bayesian Information Criterion (ABIC) is applied to objectively choose between different prior spatial correlation schemes before computing the posterior, to reduce subjectivity due to this prior condition. The ABIC is calculated using an approximate analytical expression of Bayesian evidence. The method is applied to simulated P-waves, demonstrating that model selection allows for objectively estimating the most suitable prior spatial correlation scheme in FFI. Additionally, the target spatial correlation of coseismic slip is accurately recovered using samples from the posterior PDF, as well as their uncertainties. Moreover, in the simulated experiment, it is shown that a non-robust choice of the prior spatial correlation scheme can significantly bias the estimated spatial correlations of coseismic slip. We apply our method to observed P-waves from the 2015, Illapel earthquake (Mw = 8.3), finding that the spatial correlation of coseismic slip of this earthquake is better described by a von Kármán ACF, with mean correlation lengths of around 47 km and Hurst parameter of 0.58. We conclude that using our method reduces biases associated with prior spatial correlation conditions and allows for robust estimation of spatial correlations of coseismic slip and their uncertainties.

Dynamic Rupture Modeling of Large Earthquake Scenarios at the Hellenic Arc Toward Physics‐Based Seismic and Tsunami Hazard Assessment

AbstractThe Mediterranean Hellenic Arc subduction zone (HASZ) has generated several 8 earthquakes and tsunamis. Seismic‐probabilistic tsunami hazard assessment typically utilizes uniform or stochastic earthquake models, which may not represent dynamic rupture and tsunami generation complexity. We present an ensemble of ten 3D dynamic rupture earthquake scenarios for the HASZ, utilizing a realistic slab geometry. Our simplest models use uniform along‐arc pre‐stresses or a single circular initial stress asperity. We then introduce progressively more complex models varying initial shear stress along‐arc, multiple asperities based on scale‐dependent critical slip weakening distance, and a most complex model blending all aforementioned heterogeneities. Thereby, regional initial conditions are constrained without relying on detailed geodetic locking models. Varying epicentral locations in the simplest, homogeneous model leads to different rupture speeds and moment magnitudes. We observe dynamic fault slip penetrating the shallow slip‐strengthening region and affecting seafloor uplift. Off‐fault plastic deformation can double vertical seafloor uplift. A single‐asperity model generates a 8 scenario resembling the 1303 Crete earthquake. Using along‐strike varying initial stresses results in 8.0–8.5 dynamic rupture scenarios with diverse slip rates and uplift patterns. The model with the most heterogeneous initial conditions yields a 7.5 scenario. Dynamic rupture complexity in prestress and fracture energy tends to lower earthquake magnitude but enhances tsunamigenic displacements. Our results offer insights into the dynamics of potential large Hellenic Arc megathrust earthquakes and may inform future physics‐based joint seismic and tsunami hazard assessments.

A novel back analysis framework for the probabilistic risk assessment of subaerial landslide-induced tsunami hazard

A novel back analysis framework for the probabilistic risk assessment of subaerial landslide-induced tsunami hazard

Assessment of Tsunami Hazard for the Coast of Oktyabrsky Spit, Western Kamchatka Based on Results of Numerical Modeling

Assessment of Tsunami Hazard for the Coast of Oktyabrsky Spit, Western Kamchatka Based on Results of Numerical Modeling

Physical Modeling of Tsunamis Generated by Submarine Volcanic Eruptions

AbstractSubmarine volcanic eruptions can induce major local and regional tsunami hazards through varied source mechanisms. Large‐scale experiments of tsunamis generated by submarine volcanic eruptions are conducted to study the cylindrical wave generation and propagation in a three‐dimensional wave basin. A unique volcanic tsunami generator (VTG) was deployed at the bottom of the wave basin to generate volcanic tsunamis with repeatable and controlled source parameters. The physical modeling is based on the generalized Froude number defined with the VTG velocity and the near source water depth. The pneumatically driven vertical stroke motion generates leading elevation waves in the wave basin. The tsunami waves generated by the VTG are measured with a wave gauge array. The wave maker performance is characterized by the dimensionless leading wave amplitudes and periods. The experimental data show the variations of the leading wave amplitude, period, and celerity along the radial propagation distance. The generated cylindrical waves belong to the weakly nonlinear wave regime in the near field with decaying wave amplitude along radial propagation. The attenuation rate of the leading wave exceeds the range from the linear wave theory in runs with higher Froude numbers. The dimensionless leading wave period increases with the dimensionless propagation distance due to the dispersion relation. Empirical equations for the characteristic wave parameters such as amplitudes and periods are derived. The experimental results contribute to the understanding of volcanic tsunami generation processes and may serve rapid volcanic tsunami hazard assessments as well as the advancement and validation of numerical models.

Tsunami hazard assessment in the South China Sea based on geodetic locking of the Manila subduction zone

Abstract. This study provides a dataset and shows the spatial distribution of tsunami hazard in the South China Sea sourced from the Manila subduction zone. The plate motion data around the Manila subduction zone are used to invert the geodetic locking of the Manila subduction zone, further used to estimate the maximum possible magnitude and applied to obtain a more reliable tsunami hazard assessment. The spatial distribution of tsunami wave height with a 1000-year return period is shown, and several high-hazard areas in the South China Sea are pointed out. Uncertainties in the seismic source are explored, including the slip heterogeneity, the upper limit of seismic magnitude and segmentation. The impact of the locking distribution and randomness of slip on tsunami hazard assessment demonstrates that the traditional uniform slip assumption significantly underestimates the tsunami hazard. Moreover, the assessment results involving the effect of the locking distribution should be more realistic and show a larger tsunami height than when only considering the stochastic slip in most areas, which should prompt coastal management agencies to enhance tsunami prevention awareness.

Lacustrine mass movements in active tectonic settings: Lake tsunami sources in New Zealand's South Island

Lake tsunamis generated from subaerial and subaqueous mass movements can pose a significant hazard to lakeshore communities. However, current knowledge of lake tsunamis is derived from a limited number of studies, primarily in low-seismicity settings such as Switzerland and Norway. Underrepresented are studies from active tectonic settings, characterised by high relief, high sediment yields, and frequent seismic shaking that is likely to produce episodic subaerial and subaqueous mass movements with the potential to produce lake tsunamis. This study seeks to address this gap in our understanding through an examination of four lakes in the active tectonic region of New Zealand's South Island (Lake Rotoiti, Lake Rotoroa, Lake Brunner, and Lake Mapourika). High-resolution multibeam bathymetry and high-resolution seismic reflection data were used to identify and characterize the landforms and sediment associations of large and potentially tsunamigenic mass movements. A qualitative evaluation of the tsunamigenic capacity of the identified mass movements was undertaken using established empirical relationships between mass movement volumes and run-up heights. The bathymetric and seismic surveys have revealed 16 previously undocumented mass movements capable of generating lake tsunami. Fluvial deltas and bedrock slopes proximal to active faults were the most prevalent mass movement source areas, with the largest mass movements identified being a 49 Mm3 delta collapse and a 110 Mm3 subaerial mass movement in Lake Rotoroa. The findings suggest the origin and characteristics of the potentially tsunamigenic mass movements identified were strongly influenced by the high rates of delta progradation, frequent seismic activity, and the preconditioning and displacement by active faults, typical of active tectonic settings. Our results provide new insights into the heterogeneity of lacustrine mass movements and the drivers of lake tsunami hazards in underrepresented high-seismicity regions. The findings illustrate the importance of developing regionally specific insights into lake tsunami susceptibility and may inform the direction of more detailed lake tsunami hazard assessment in New Zealand.

A novel multiple-expert protocol to manage uncertainty and subjective choices in probabilistic single and multi-hazard risk analyses

Integrating diverse expert opinions in hazard and risk projects is essential to managing subjective decisions and quantifying uncertainty to produce stable and trustworthy results. A structured procedure is necessary to organize the gathering of experts' opinions while ensuring transparency, accountability, and independence in judgements. We propose a novel Multiple-Expert management Protocol (MEP) to address this challenge, providing procedural guidelines for conducting single to multi-hazard risk analyses. MEP establishes a workflow to manage subjectivity rooted in (i) moderated and staged group interactions, (ii) trackable blind advice through written elicitations with mathematical aggregation, (iii) participatory independent review, (iv) close cooperation between scientific and managerial coordination, and (v) proper and comprehensive documentation. Originally developed for stress testing critical infrastructure, MEP is designed as a single, flexible, technology-neutral procedural workflow applicable to various sectors. Moreover, its scalability allows it to adapt from high to low-budget projects and from complex probabilistic multi-hazard risk assessments to standard single-hazard analyses, with different experts' degree and type of involvement depending on available funding and emerging controversies. We present two compelling case studies to showcase MEP's practical applicability: a multi-hazard risk analysis for a port infrastructure and a single-hazard regional tsunami hazard assessment.

High-resolution tsunami hazard assessment for the Guangdong-Hong Kong-Macao Greater Bay Area based on a non-hydrostatic tsunami model

High-resolution tsunami hazard assessment for the Guangdong-Hong Kong-Macao Greater Bay Area based on a non-hydrostatic tsunami model

A Review of Tsunamis Generated by Volcanoes (TGV) Source Mechanism, Modelling, Monitoring and Warning Systems

Tsunamis generated by volcanic eruptions have risen to prominence since the December 2018 tsunami generated by the flank collapse of Anak Krakatau during a moderate eruption and then the global tsunami generated by the explosive eruption of the Hunga volcano in the Tongan Archipelago in January 2022. Both events cause fatalities and highlight the lack in tsunami warning systems to detect and warn for tsunamis induced by volcanic mechanisms. Following the Hunga Tonga—Hunga Ha’apai eruption and tsunami, an ad hoc working group on Tsunamis Generated by Volcanoes was formed by the Intergovernmental Oceanographic Commission of UNESCO. Volcanic tsunamis differ from seismic tsunamis in that there are a wide range of source mechanisms that can generate the tsunamis waves and this makes understanding, modelling and monitoring volcanic tsunamis much more difficult than seismic tsunamis. This paper provides a review of both the mechanisms behind volcanic tsunamis and the variety of modelling techniques that can be used to simulate their effects for tsunami hazard assessment and forecasting. It gives an example of a volcanic tsunami risk assessment undertaken for Stromboli, outlines the requirement of volcanic monitoring to warn for tsunami hazard and provides examples of volcanic tsunami warning systems in Italy, the Hawaiian Island (USA), Tonga and Indonesia. The paper finishes by highlighting the need for implementing monitoring and warning systems for volcanic tsunamis for locations with submarine volcanoes or near-shore volcanoes which could potentially generate tsunamis.

Volcanic Flank Collapse, Secondary Sediment Failure and Flow‐Transition: Multi‐Stage Landslide Emplacement Offshore Montserrat, Lesser Antilles

AbstractVolcanic flank collapses, especially those in island settings, have generated some of the most voluminous mass transport deposits on Earth and can trigger devastating tsunamis. Reliable tsunami hazard assessments for flank collapse‐driven tsunamis require an understanding of the complex emplacement processes involved. The seafloor sequence southeast of Montserrat (Lesser Antilles) is a key site for the study of volcanic flank collapse emplacement processes that span subaerial to submarine environments. Here, we present new 2D and 3D seismic data as well as MeBo drill core data from one of the most extensive mass transport deposits offshore Montserrat, which exemplifies multi‐phase landslide deposition from volcanic islands. The deposits reveal emplacement in multiple stages including two blocky volcanic debris avalanches, secondary seafloor failure and a late‐stage erosive density current that carved channel‐like incisions into the hummocky surface of the deposit about 15 km from the source region. The highly erosive density current potentially originated from downslope‐acceleration of fine‐grained material that was suspended in the water column earlier during the slide. Late‐stage erosive turbidity currents may be a more common process following volcanic sector collapse than has been previously recognized, exerting a potentially important control on the observed deposit morphology as well as on the runout and the overall shape of the deposit.

Testing Megathrust Rupture Models Using Tsunami Deposits

AbstractThe 26 January 1700 CE Cascadia subduction zone earthquake ruptured much of the plate boundary and generated a tsunami that deposited sand in coastal marshes from northern California to Vancouver Island. Although the depositional record of tsunami inundation is extensive in some of these marshes, few sites have been investigated in enough detail to map the inland extent of sand deposition and depict variability in tsunami deposit thickness and grain size. We collected 129 cores in marshes of the Salmon River estuary in Oregon and reanalyzed 114 core logs from a 1987–88 study that mapped the inland extent of circa 1700 CE sandy tsunami deposits. The ca. 1700 CE tsunami deposit in the Salmon River estuary is easily recognized in cores ≤1 m deep in which a buried marsh peat is overlain by a well sorted sand bed with a sharp lower contact that thins and fines inland. We use tsunami deposit data and models of sandy tsunami sediment transport (using Delft3D‐FLOW) to test 15 rupture models that could represent a ca. 1700 CE earthquake. At least 12–16 m of slip offshore of the Salmon River, which results in 0.8–1.0 m of coastal coseismic subsidence, is required to match the ca. 1700 CE sand deposit's inland extent, which is consistent with models of heterogeneous megathrust slip in ca. 1700 CE. Our methods of detailed tsunami deposit mapping, combined with sediment transport modeling, can be used to test models of megathrust ruptures and their tsunamis to potentially improve earthquake and tsunami hazard assessments.

Tsunami hazard evaluation of river embankment structures incorporating their vulnerability to seismic strong motion

Development of coastal areas in Japan for various land uses since the 1960s has contributed to industrial upgrades and improved the efficiency of transportation networks. However, there are concerns about the vulnerability of developments on alluvial plains and reclaimed lands to geological events, like ground subsidence due to liquefaction during large earthquakes. Realistic assessment of earthquake and tsunami hazards and evaluation of possible countermeasures require accurate estimation of the amount of subsidence that can be expected from liquefaction at coastal and riverside sites supporting various structures. In this study, to evaluate the amount a river embankment structure might be expected to settle as a result of strong motion from an assumed Nankai Trough great earthquake, we conducted a numerical simulation using the soil–water coupled finite deformation analysis code GEOASIA. We then investigated the effect of the estimated embankment subsidence on tsunami inundation, which was simulated by using nonlinear shallow-water equations and a grid spacing as fine as 3.3 m. The influence of urban structures on the inundated area was taken into account by using a structure-embedded elevation model (SEM). The results showed that subsidence of river embankments and the collapse of parapet walls on top of them would increase both the depth and area of inundation caused by a tsunami triggered by a Nankai Trough scenario earthquake. Our findings underscore the importance of evaluating not only earthquake resistance but also vulnerability of coastal and riverside structures to strong motion in tsunami hazard analyses. Furthermore, the importance of tsunami inundation analysis using a SEM for predicting the behavior of tsunami flotsam in urban areas was demonstrated.

Scenario-based tsunami hazard assessment for Northeastern Adriatic coasts

Significant tsunamis in the Northern Adriatic are rare, and only a few historical events have been reported in the literature, with sources mostly located along central and southern parts of the Adriatic coasts. Recently, a tsunami alert system has been established for the whole Mediterranean area; however, a detailed description of the potential impact of tsunami waves on coastal areas is still missing for several sites. This study aims to model the hazard associated with possible tsunamis generated by offshore earthquakes, with the purpose of contributing to tsunami risk assessment for selected urban areas along the Northeastern Adriatic coasts. Tsunami modelling is performed by the NAMI DANCE software, which allows accounting for seismic source properties, variable bathymetry, and nonlinear effects in wave propagation. Hazard scenarios at the shoreline are developed for the coastal areas of Northeastern Italy and at selected cities (namely, Trieste, Monfalcone, Lignano and Grado). An extensive set of potential tsunamigenic sources of tectonic origin located in three distance ranges (namely at Adriatic-wide, regional and local scales) are considered for the modelling. Sources are defined according to available literature, which includes catalogues of historical tsunamis and existing active faults databases. Accordingly, a set of tsunami-related parameters and maps are obtained (e.g. maximum run-up, arrival times, synthetic mareograms) that are relevant to planning mitigation actions at the selected sites.

Probabilistic tsunami hazard assessment for the makran subduction zone using logic tree and stochastic rupture sources

ABSTRACT The Makran Subduction Zone (MSZ) in the northwestern Indian Ocean can generate large tsunamigenic thrust earthquakes affecting the coastal regions of Pakistan, Iran, Oman, and western India. In this paper, a probabilistic tsunami hazard assessment is conducted for the MSZ using stochastic tsunami simulations of moment magnitude (Mw) of 7.7–9.1 earthquake scenarios. This study investigates uncertainties associated with earthquake occurrence rate, single-segment (eastern and western MSZ) or two-segment (full MSZ) rupture scenarios, source geometry, and slip heterogeneity. The total number of simulated source models is 15,000. This study presents two major categories of results: stochastic source models and ranges of 475, 975, and 2475-year tsunami heights. For instance, tsunami heights generated by Mw 8.5‒8.7 stochastic sources of western MSZ vary between 1 m and 10 m with a mean of ~ 4.5 m in the affected areas. The tsunami heights are sensitive to the source models’ characteristics, such as location of the large slip areas, bathymetry of the nearshore area, and the location of bays. Considering different occurrence rates results in significant variability in the estimated 475, 975, and 2475-year tsunami heights. For example, 2475-year tsunami height in Chabahar is in the range of 3‒7.4 m at 10 m water depth.

The 2020 Mw 7.0 Samos (Eastern Aegean Sea) Earthquake: joint source inversion of multitype data, and tsunami modelling

SUMMARY We present a kinematic slip model and a simulation of the ensuing tsunami for the 2020 Mw 7.0 Néon Karlovásion (Samos, Eastern Aegean Sea) earthquake, generated from a joint inversion of high-rate GNSS, strong ground motion and InSAR data. From the inversion, we find that the source time function has a total duration of ∼20 s with three peaks at ∼4, 7.5 and 15 s corresponding to the development of three asperities. Most of the slip occurs at the west of the hypocentre and ends at the northwest downdip edge. The peak slip is ∼3.3 m, and the inverted rake angles indicate predominantly normal faulting motion. Compared with previous studies, these slip patterns have essentially similar asperity location, rupture dimension and anticorrelation with aftershocks. Consistent with our study, most published papers show the source duration of ∼20 s with three episodes of increased moment releases. For the ensuing tsunami, the eight available gauge records indicate that the tsunami waves last ∼18–30 hr depending on location, and the response period of tsunami is ∼10–35 min. The initial waves in the observed records and synthetic simulations show good agreement, which indirectly validates the performance of the inverted slip model. However, the synthetic waveforms struggle to generate long-duration tsunami behaviour in simulations. Our tests suggest that the resolution of the bathymetry may be a potential factor affecting the simulated tsunami duration and amplitude. It should be noted that the maximum wave height in the records may occur after the decay of synthetic wave amplitudes. This implies that the inability to model long-duration tsunamis could result in underestimation in future tsunami hazard assessments.

Nearshore tsunami amplitudes across the Maldives archipelago due to worst-case seismic scenarios in the Indian Ocean

Abstract. The Maldives face the threat of tsunamis from a multitude of sources. However, the limited availability of critical data, such as bathymetry (a recurrent problem for many island nations), has meant that the impact of these threats has not been studied at an island scale. Conducting studies of tsunami propagation at the island scale but across multiple atolls is also a challenging task due to the large domain and high resolution required for modelling. Here we use a high-resolution bathymetry dataset of the Maldives archipelago, as well as corresponding high numerical model resolution, to carry out a scenario-based tsunami hazard assessment for the entire Maldives archipelago to investigate the potential impact of plausible far-field tsunamis across the Indian Ocean at the nearshore island scales across the atolls. The results indicate that the bathymetry of the atolls, which are characterized by very steep boundaries offshore, is extremely efficient in absorbing and redirecting incoming tsunami waves. Results also highlight the importance that local effects have in modulating tsunami amplitude nearshore, including the location of the atoll in question, the location of a given island within the atoll, and the distance of that island to the reef, as well as a variety of other factors. We also find that the refraction and diffraction of tsunami waves within individual atolls contribute to the maximum tsunami amplitude patterns observed across the islands in the atolls. The findings from this study contribute to a better understanding of tsunamis across complex atoll systems and will help decision and policy makers in the Maldives assess the potential impact of tsunamis across individual islands. An online tool is provided which presents users with a simple interface, allowing the wider community to browse the simulation results presented here and assess the potential impact of tsunamis at the local scale.

Linked and fully coupled 3D earthquake dynamic rupture and tsunami modeling for the Húsavík–Flatey Fault Zone in North Iceland

Abstract. Tsunamigenic earthquakes pose considerable risks, both economically and socially, yet earthquake and tsunami hazard assessments are typically conducted separately. Earthquakes associated with unexpected tsunamis, such as the 2018 Mw 7.5 strike-slip Sulawesi earthquake, emphasize the need to study the tsunami potential of active submarine faults in different tectonic settings. Here, we investigate physics-based scenarios combining simulations of 3D earthquake dynamic rupture and seismic wave propagation with tsunami generation and propagation. We present time-dependent modeling of one-way linked and 3D fully coupled earthquakes and tsunamis for the ∼ 100 km long Húsavík–Flatey Fault Zone (HFFZ) in North Iceland. Our analysis shows that the HFFZ has the potential to generate sizable tsunamis. The six dynamic rupture models sourcing our tsunami scenarios vary regarding hypocenter location, spatiotemporal evolution, fault slip, and fault structure complexity but coincide with historical earthquake magnitudes. Earthquake dynamic rupture scenarios on a less segmented fault system, particularly with a hypocenter location in the eastern part of the fault system, have a larger potential for local tsunami generation. Here, dynamically evolving large shallow fault slip (∼ 8 m), near-surface rake rotation (± 20∘), and significant coseismic vertical displacements of the local bathymetry (± 1 m) facilitate strike-slip faulting tsunami generation. We model tsunami crest to trough differences (total wave heights) of up to ∼ 0.9 m near the town Ólafsfjörður. In contrast, none of our scenarios endanger the town of Akureyri, which is shielded by multiple reflections within the narrow Eyjafjörður bay and by Hrísey island. We compare the modeled one-way linked tsunami waveforms with simulation results using a 3D fully coupled approach. We find good agreement in the tsunami arrival times and location of maximum tsunami heights. While seismic waves result in transient motions of the sea surface and affect the ocean response, they do not appear to contribute to tsunami generation. However, complex source effects arise in the fully coupled simulations, such as tsunami dispersion effects and the complex superposition of seismic and acoustic waves within the shallow continental shelf of North Iceland. We find that the vertical velocity amplitudes of near-source acoustic waves are unexpectedly high – larger than those corresponding to the actual tsunami – which may serve as a rapid indicator of surface dynamic rupture. Our results have important implications for understanding the tsunamigenic potential of strike-slip fault systems worldwide and the coseismic acoustic wave excitation during tsunami generation and may help to inform future tsunami early warning systems.

Probabilistic Tsunami Hazard Assessment Considering the Sequence of the First and Second Earthquakes Along the Nankai Trough

The Earthquake Research Committee (ERC) of the Headquarters for Earthquake Research Promotion conducted a probabilistic tsunami hazard assessment due to large earthquakes along the Nankai Trough for the next 30 years. Utilizing the basic data of earthquake source models and calculated maximum tsunami heights, the authors propose a method to evaluate the hazard curves of the first and second earthquakes separately, considering the sequence of earthquake occurrence in one cycle of large earthquake activities along the Nankai Trough. First, based on the relative weights allocated to the 176 occurrence patterns of 79 earthquake source regions, the weights for the 2,720 characterized earthquake fault models (CEFMs) are calculated. The hazard curve of the first earthquake is evaluated using the 2,720 sets of maximum tsunami heights and weights under the condition that one of the CEFMs causes an earthquake. Next, the conditional hazard curves for the possible second earthquakes conditional on each individual first earthquake are calculated. Finally, the hazard curve for the second earthquake is evaluated as a weighted average of the conditional hazard curves. Numerical examples are shown for 15 sites. The first earthquake accounts for about 60% or more of the total hazard evaluated by ERC, and its contribution increases with increasing maximum tsunami height. The first and second earthquakes account for 80%–90% of the total hazard.

Methodology for probabilistic tsunami-triggered oil spill fire hazard assessment based on Natech cascading disaster modeling

A novel modeling methodology is presented for cascading disasters triggered by tsunami hazards considering uncertainties. The proposed methodology focuses on tsunami-triggered oil spills and subsequent fires, a type of natural hazard-triggered technological (Natech) event. The methodology numerically simulates the time-varying behavior of tsunami-triggered oil spill fires for numerous stochastically generated scenarios and performs a probabilistic mapping of the maximum radiative heat flux as a quantitative measure of the fire hazard. To enable these assessments, probabilistic tsunami hazard assessments are extended to include the tsunami-induced movement of oil storage tanks, resulting oil spills, tsunami-driven oil fire spread, and thermal radiation from fires. The uncertainty of the earthquake fault slip distribution, oil filling level of storage tanks, and fire starting time and position is incorporated into the new assessments. To demonstrate the methodology, a realistic case study is conducted for a coastal petrochemical industrial park in Japan conditioned on possible offshore moment magnitude 9.1 earthquakes. Contrary to typical tsunami direct impact assessments, the results highlight the cascading effects of tsunamis and large variability in key output variables concerning oil spills and fires. This indicates that the methodology is useful for deepening stakeholders’ understanding of tsunami-triggered cascading disasters and improving risk reduction plans.