Probabilistic Tsunami Hazard Assessment Research Articles

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.

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.

FROM OFFSHORE TO ONSHORE PROBABILISTIC TSUNAMI HAZARD ASSESSMENT WITH QUANTIFIED UNCERTAINTY: EFFICIENT MONTE CARLO TECHNIQUES

Offshore probabilistic tsunami hazard assessments (PTHAs) are increasingly available for earthquake generated tsunamis. They provide standardized representations of tsunami scenarios, their uncertain occurrence-rates, and models of the deep ocean waveforms. To quantify onshore hazards it is natural to combine this information with a site-specific inundation model, but this is computationally challenging to do accurately, especially if accounting for uncertainties in the offshore PTHA. This study reviews an efficient Monte Carlo method recently proposed to solve this problem. The efficiency comes from preferential sampling of scenarios that are likely important near the site of interest, using a user-defined importance measure derived from the offshore PTHA. The theory of importance sampling enables this to be done without biasing the final results. Techniques are presented to help design and test Monte Carlo schemes for a site of interest (before inundation modelling) and to quantify errors in the final results (after inundation modelling). The methods are illustrated with examples from studies in Tongatapu and Western Australia.

NON-STATIONARY PROBABILISTIC TSUNAMI HAZARD ASSESSMENTS INCORPORATING TIDES AND SEA LEVEL RISE

Tides and climate driven sea level rise (SLR) contribute significantly to water level changes in the short and long term, respectively. In terms of magnitude, they could be comparable to tsunamis of interest at certain coasts. New non-stationary probabilistic tsunami hazard assessment (nPTHA) methods that were developed to include the mean sea level changes due to a warming climate are now extended to incorporate the uncertainty of the tidal phase at the moment of tsunami occurrence. Here, a collocation-based model is used in the nPTHA method to render the calculation feasible and efficient.

Optimal probabilistic placement of facilities using a surrogate model for 3D tsunami simulations

Abstract. This study proposes a framework for utilizing results obtained from advanced numerical simulations and performing probabilistic tsunami hazard assessment for investigating optimal facility placement. A set of numerical simulations of the tsunami off the Pacific coast caused by the 2011 Tohoku earthquake are performed considering uncertainties in fault parameters. Both inundation depths and tsunami forces acting on buildings are numerically simulated and defined as tsunami hazard indices. Proper orthogonal decomposition is then applied to numerical results for extracting characteristic spatial modes, which can be used to construct surrogate models. Monte Carlo simulations (MCSs) were performed at a low computational cost using surrogate models. The optimal placement of facilities was probabilistically investigated with the help of genetic algorithms using the MCS results along with the concept of system failure probability. The results indicate that the proposed framework allows determining the optimal placement of facilities by applying different strategies at low computational costs while effectively reflecting the results of advanced tsunami simulations.

A multi-proxy approach to assess tsunami hazard with a preliminary risk assessment: A case study of the Makran Coast, Pakistan

Tsunamis and cyclones are sea-borne hazards capable of inundating vast coastal areas. This study aims at an extreme wave hazard assessment with a preliminary inundation analysis along the Makran Coast, Pakistan. The coastal hazard, particularly tsunamis, is evaluated by integrating five approaches: (i) probabilistic tsunami hazard assessment (PTHA); (ii) deterministic tsunami hazard assessment (DTHA); (iii) geophysical-seismic (2-D thermal modelling), (iv) sedimentary tsunami deposits (tsunamis); and (v) the historical record. The recurrence interval for a mega-tsunami event (≥12 m) is between 500 and 1000 years in the Arabian Sea. Of these mega-tsunamis, about 60% are generated by seismic sources, while the remaining 40% are attributed to secondary (co-seismic submarine landslides) and other non-seismic sources. Based on the above five approaches, the hazard analysis helped to shortlist four wave scenarios (3, 7, 10, and 15 m). Which were further used to demarcate risk areas through static inundation analysis. The results indicated that the damage potential at the coast is minor to negligible with 3 m waves and moderate with 7 m waves. Whereas the 10 m and 15 m waves will severely disrupt the study area. In addition to tsunami risk, cyclone risk is assessed by interpolating storm tracks dating back to 1842 CE. In the last 64 years, cyclone frequency has jumped from 1 cyclone per 10 years to 20 cyclones per 10 years, and the intensity has increased by two levels from Tropical Storm (TS) to Category-3.

Assessing tsunami vertical evacuation processes based on probabilistic tsunami hazard assessment for west coast of Aceh Besar, Indonesia

BackgroundTsunamis are rare events compared to other disasters but have devastating consequences. In the last 100 years, more than 24 tsunamis and more than 235,000 fatalities have occurred globally. Indonesia has a high risk of a tsunami disaster. Since the devastating 2004 tsunami in the Indian Ocean, much research and preparatory work have been done to reduce the impact of future tsunamis in Indonesia, including in the province of Aceh, especially along the western coast where West Aceh is located. This coastal area was destroyed by a tsunami as high as 15–30 m, resulting in the loss of life, housing, tourist areas, industrial areas, and other public facilities. Given that tsunami disasters are rare and sometimes occur long in advance, human memory and awareness are reduced, making research on the level of tsunami awareness of disasters a challenging task.MethodProbabilistic Tsunami Hazard Assessment (PTHA) is a method that has been developed to predict tsunami hazards with a return period of hundreds to thousands of years, beyond the limited availability of historical data. The PTHA method can provide important information that supports tsunami risk management measures. This study aims to estimate recurrence period-based tsunami risk on the west coast of the district of Aceh Besar using the PTHA method. In this study, the source of the tsunami is caused by fault activity at sea. Seven tsunami scenarios based on fault parameters (earthquakes of magnitudes Mw 8.0 to 9.2 with interval 0,2) with the fault location focusing on the Aceh-Andaman Mega Thrust Segment, as applied in this study. This segment was a similar source to the 2004 Indian Ocean tsunami that created a rupture area along a distance of 1155 km, with six parts of the fault.ResultThe maximum inundation distance reached 6 km for the flat area, with a flow depth of 13 m. The site has a cliff that is close to the shoreline, with an inundation distance shorter than the distance across the flat area. With an arrival time of less than 25 min, it is recommended to have an evacuation building and evacuation road in a wide inundated area, and an arrangement of hills close to the beach as an evacuation area, in order to reduce the number of casualties. For 100 years return period or exceedance probability rate 0.01, the average flow depth on the coast may exceed 5 m, and the maximum flow depth for a 1000-year return period or annual probability of 0.001 is 12 m. With the potential tsunami in the future, continuous tsunami drills and tsunami education are needed so that people can maintain an awareness of the threat posed by tsunamis.

Probabilistic Analysis of the Tsunami Disaster on the Vulnerability Level of Buildings in Painan City, West Sumatra based on the Earthquake Ratio with the Logic Tree Method

Indonesia is an archipelagic country stretching from Sabang to Merauke and is located at the convergence of the most complex and active tectonic plates in the world, namely Eurasia, Indo-Australia, and the Pacific. One of the regions with a high probability of earthquakes and high tsunamis is the island of Sumatra, which lies between the Eurasian and Indo-Australian plates. Painan city is located in West Sumatra Province, where it is surrounded by three megathrust zones: the Nias-Simeulue segment, Mentawai-Siberut segment, and Mentawai-Pagai segment. These three megathrust zones, namely Nias-Simeulue with an estimated earthquake magnitude of 8.7 Mw, Mentawai-Siberut with an earthquake magnitude of 8.9 Mw, and Mentawai-Pagai with an earthquake magnitude of 8.9 Mw, can potentially cause tsunamis that may reach Painan city. The aim of this study is to investigate the influence of seismic activity level variables and the ratio between large and small earthquakes on tsunami wave height using the logic tree method, assess the tsunami hazard potential using Probabilistic Tsunami Hazard Assessment (PTHA), and evaluate the vulnerability of existing buildings in Painan city. Tsunami simulations in this study were conducted using the Cornell Multigrid Coupled Tsunami (COMCOT) program, which applies the Shallow Water Equation (SWE). Additionally, the Building Tsunami Vulnerability (BTV) equation was used to calculate the vulnerability index of buildings based on their conditions and tsunami wave heights. The calculation of the BTV value for the tsunami height parameter was modified using fragility curves that depict the relationship between force and the probability of tsunami wave damage. From the simulation results, the tsunami height was obtained, which in turn determines the probability of tsunami hazard on buildings with return periods of 1000 and 4000 years. After the simulations, the Building Tsunami Vulnerability (BTV) calculation was performed to determine the vulnerability level of buildings to tsunamis.

Multi-level emulation of tsunami simulations over Cilacap, South Java, Indonesia

Carrying out a Probabilistic Tsunami Hazard Assessment (PTHA) requires a large number of simulations done at a high resolution. Statistical emulation builds a surrogate to replace the simulator and thus reduces computational costs when propagating uncertainties from the earthquake sources to the tsunami inundations. To reduce further these costs, we propose here to build emulators that exploit multiple levels of resolution and a sequential design of computer experiments. By running a few tsunami simulations at high resolution and many more simulations at lower resolutions we are able to provide realistic assessments whereas, for the same budget, using only the high resolution tsunami simulations do not provide a satisfactory outcome. As a result, PTHA can be considered with higher precision using the highest spatial resolutions, and for impacts over larger regions. We provide an illustration to the city of Cilacap in Indonesia that demonstrates the benefit of our approach.

Non‐Stationary Probabilistic Tsunami Hazard Assessments Compounding Tides and Sea Level Rise

AbstractTides are often the largest source of sea levels fluctuations. Two new probabilistic tsunami hazard assessments (PTHA) methods are proposed to combine the tidal phase uncertainty at the moment of tsunami occurrence with other sources of uncertainty. The first method adopts a Stochastic Reduced Order Model (SROM) producing sets of tidal phase samples to be used in tsunami simulations. The second method uses tsunami simulations with prescribed collocation tidal phases and tide probability distributions to model the uncertainty. The methods are extended to non‐stationary probabilistic tsunami hazard assessment, compounding tsunamis, tides and sea level rise (SLR). As an illustration, these methods are applied for assessing tsunamis generated in the Manila Subduction Zone, on the coasts of Kao Hsiung and Hong Kong. While the SROM‐based method is faster solving for the PTHA if only tides are considered, the collocation‐based method is faster when both SLR and tides are considered. For the illustration case, tides have a relevant impact on PTHA results, however, the SLR within an exposure time of 100 years has stronger impact. PTHA curves of the maximum tsunami elevation are affected by tides and SLR differently. While tides and SLR increase the dispersion of PTHA hazard curve distributions, the latter also produces a translation toward higher elevations. The development of formulations based on SROM or collocation tides is the key to establishing a method which feasibly can be applied to other regions for comprehensive analysis at a global scale.

Probabilistic tsunami hazard assessment based on the Gutenberg–Richter law in eastern Shikoku, Nankai subduction zone, Japan

Earthquake and tsunami predictions comprise huge uncertainties, thus necessitating probabilistic assessments for the design of defense facilities and urban planning. In recent years, computer development has advanced probabilistic tsunami hazard assessments (PTHAs), where hazard curves show the exceedance probability of the maximum tsunami height. However, owing to the lack of historical and geological tsunami records, this method is generally insufficient for validating the estimated hazard curves. The eastern coast of Shikoku in the Nankai subduction zone, Japan, is suitable for validation because tsunami records from historical Nankai Trough earthquakes are available. This study evaluated PTHAs by comparing the tsunami hazard curves and exceedance frequencies of historical Nankai Trough tsunamis. We considered 3480 earthquake scenarios representing the rupture patterns of past Nankai earthquakes and calculated all tsunamis. The probability of earthquake occurrence was based on the Gutenberg–Richter law. We considered uncertainty in tsunami calculations with astronomical tide variations. The estimated tsunami hazard curves are consistent with the exceedance frequencies obtained from historical tsunamis. In addition, sensitivity tests indicate the significance of the earthquake slip heterogeneity and tsunami defense facilities in PTHAs. We also extended the PTHAs to tsunami inundation maps in high resolution and proposed an effective new method for reducing the tsunami computation load.Graphical

Application of external flood probabilistic safety assessment methodology to Prototype Fast Breeder Reactor

ABSTRACT This paper presents the methodology adopted, accident sequence analysis and salient results from the external flood probabilistic safety analysis exercise for Prototype Fast Breeder Reactor. The major steps performed are the probabilistic hazard estimation, fragility computation, system reliability modelling and risk quantification. The hazard analysis has been performed for rainfall, storm surge and tsunami as typically associated with a coastal site, from which correlation function relating flood level to the annual exceedance frequency is estimated. The fragility analysis of different safety systems is estimated by considering submergence mode of failure using step fragility functions. The secondary effects of flood such as debris impact, load falling and flood-induced sodium fires are not considered. The human reliability analysis of manual operations necessary for plant safety is done for the control room as well as onsite actions. The challenges encountered during the analysis, salient results and uncertainties involved are presented with inferences. Abbreviations: AHX: air heat exchanger; CDF: core damage frequency; EFPSA: external flood probabilistic safety assessment; EL: elevation levels; EOP: emergency operation procedure; ET: event tree; FT: fault tree; HRA: human reliability analysis; IE: initiating events; NPP: nuclear power plant; OGDHRS: operation grade decay heat removal system; PFBR: prototype fast breeder reactor; POT: peak over threshold; PSA: probabilistic safety assessment; PTHA: probabilistic tsunami hazard assessment; RY: reactor year; RCB: reactor containment building; RP: return period; SGDHRS: safety grade decay heat removal system; SSC: structures, systems and components

Development of the Japan Tsunami Hazard Information Station (J-THIS)

To promote effective disaster countermeasures against possible tsunamis in the future, an effective application of tsunami hazard information is important. However, there were insufficient systems available for utilizing and applying various tsunami hazard information. Based on this situation, we developed and have been improving the Japan Tsunami Hazard Information Station (J-THIS), an open Web system available as a public portal for providing tsunami hazard information based on the probabilistic tsunami hazard assessment (PTHA). It provides tsunami hazard information through the following services: map services, data download services, and Web application programming interface (API) services. Based on the PTHA along the Nankai Trough, the J-THIS provides distributions of exceedance probability of tsunami heights for 30 years, tsunami hazard curves, earthquake fault models, tsunami heights for each earthquake fault model, and bathymetric charts. To illustrate the use of the J-THIS, understanding how existing coastal structures will protect us against tsunamis while enabling the local governments to set investment priorities in disaster risk reduction and resilience is key.

An approach for quantifying nearshore tsunami height probability and its application to the Pearl River Estuary

This study focuses on the coast around the Pearl River Estuary, and assesses tsunami hazard posed by the earthquakes along the Manila Trench. A probabilistic tsunami hazard assessment (PTHA) has been conducted based on 1,380,000 potential earthquake scenarios, in order to consider the uncertainty of seismic parameters as much as possible. To achieve such a large number of scenario simulations, the tsunami at an offshore position is firstly simulated based on a superposition approach proposed in previous studies, and then the joint probability density of incident tsunami period and height at the offshore position is obtained. After that, an amplification factor is adopted to estimate nearshore tsunami height probability from the offshore position. The amplification factor is the main concern in this study. It is commonly estimated from the Green’ law based on the linear wave shoaling theory, which is a simple and effective way. However, it may loss accuracy in the coast with complicate topography and tortuous shoreline. This study numerically obtained a dataset of wave amplification factors along the concerned coast, using the two-dimensional FUNWAVE-TVD model based on the Boussinesq equations. The results confirm the significance of incident wave period and height on the amplification factor, and suggest a more carefully estimation on the amplification factor should be taken into consideration. Based the newly obtained dataset of wave amplification factors, the quantified tsunami hazard probability along the concerned coast is given.

Probabilistic Tsunami Hazard Assessment of Offshore Wave Heights for Southern Region of Pingtung County in Southern Taiwan

This study applies the unit tsunami method and probabilistic tsunami hazard analysis to investigate the tsunami hazard for the southern region of Pingtung County in southern Taiwan. The FUNWAVE-TVD model is used to calculate the aleatory and epistemic uncertainties. The aleatory uncertainty is analyzed using a comparison of simulated and observed maximum tsunami wave heights and the epistemic uncertainty is evaluated using a scenario caused by earthquakes in the Manila and Ryukyu subduction zones according to probabilistic seismic hazard analysis in Taiwan using Senior Seismic Hazard Analysis Committee Level 3 methodology. A unit tsunami method database is established for the Manila and Ryukyu subduction zones and used to carry out a probability-based offshore tsunami wave height simulation for the southern region of Pingtung County. A hazard map for tsunamis caused by earthquakes in the Manila and Ryukyu subduction zones is also derived.

A heuristic features selection approach for scenario analysis in a regional seismic probabilistic tsunami hazard assessment

Seismic Probabilistic Tsunami Hazard Analysis (SPTHA) is aimed at estimating the annual rate of exceedance of an earthquake-induced tsunami wave of a certain location with reference to a predefined height threshold. The analysis relies on computationally demanding numerical simulations of seismic-induced tsunami wave generation and propagation. A large number of scenarios needs to be simulated to account for uncertainties. However, the exceedance of tsunami wave threshold height is a rare event so that most of the simulated scenarios bring little statistical contribution to the estimation of the annual rate yet increasing the computational burden. To efficiently address this issue, we propose a wrapper-based heuristic approach to select the set of most relevant features of the seismic model, for deciding a priori the seismic scenarios to be simulated. The proposed approach is based on a Multi-Objective Differential Evolution Algorithm (MODEA) and is developed with reference to a case study whose objective is calculating the annual rate of threshold exceedance of the height of tsunami waves caused by subduction earthquakes that might be generated on a section of the Hellenic Arc, and propagated to a set of target sites: Siracusa, on the eastern coast of Sicily, Crotone, on the southern coast of Calabria, and Santa Maria di Leuca, on the southern coast of Puglia. The results show that, in all cases, the proposed approach allows a reduction of 95% of the number of scenarios with half of the features to be considered, and with no appreciable loss of accuracy.

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

SUMMARYOffshore 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 earthquake 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 efficient Monte Carlo 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 bias. The techniques are demonstrated in a high-resolution onshore PTHA for the island of Tongatapu in Tonga, using the 2018 Australian PTHA as the offshore PTHA, while considering only thrust earthquake sources on the Kermadec-Tonga trench. The efficiency improvements are 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 quantification of epistemic uncertainties, while controlling Monte Carlo errors.

Risk Assessment of Tsunamis Along the Chinese Coast Due to Earthquakes

China’s coastal areas are densely populated, economically developed, and located in close proximity to several potential tsunami sources; therefore, tsunami risk cannot be ignored. This study assessed tsunami risk in coastal areas of China by developing a framework for tsunami risk assessment from the perspectives of hazards, vulnerability, and exposure. First, a probabilistic tsunami hazard assessment (PTHA) model was applied to estimate the potential tsunami sources in both local crustal faults and circum-Pacific subduction zones based on numerical simulations. The output of the PTHA includes tsunami wave height distributions along the coast. Then, an indicator system reflecting exposure and vulnerability to tsunamis in the coastal areas of China was established by using the entropy method and analytic hierarchy process. The PTHA findings show that the tsunami wave height is close to 3 m on the southern coast of the Bohai Sea, the Pearl River Estuary, and the Yangtze River Delta and exceeds 2 m near the Taiwan Strait for the 2000-year return period. The results of the tsunami risk assessment show that the cities at the highest risk level (level I) include Tangshan, Yantai, and Hong Kong, while cities at the high risk level (level II) include Fuzhou, Xiamen, and Quanzhou near the Taiwan Strait and many cities on the Yangtze River Delta, the Pearl River Estuary, and the southern coast of the Bohai Sea. Our findings can provide an understanding of differences in tsunami risk between Chinese coastal cities that may be affected by tsunamis in the future.

Parallel density scanned adaptive Kriging to improve local tsunami hazard assessment for coastal infrastructures

Seismic Probabilistic Tsunami Hazard Assessment (SPTHA) is a framework for calculating the probability that seismically induced tsunami waves exceed a specific threshold height, over a given time span and a specific region (i.e. regional SPTHA) or site (i.e. local SPTHA). To account for the uncertainty of the possible sources, SPTHA must integrate the results of a large number of computationally demanding tsunami simulationsIn this work, we innovatively use Parallel density scanned Adaptive Kriging (P-ds AK) to overcome the computational efficiency challenge of local SPTHA within a framework that consists in modeling/retrieving the full spectrum of possible earthquake triggering events at the regional level, filtering sources not relevant for the target, adopting a clustering procedure to select “representative scenarios” for inundation modeling, and, finally, adopt P-ds AK to identify the clusters centroids that most influence the hazard intensity (i.e., wave height) in the areas of interest.This approach is applied in the area of the oil refinery located in Milazzo (Italy). The application shows a consistent reduction of the number of high-resolution tsunami simulations required for the evaluation of the hazard curves over a set of inland Point of Interest (PoIs), either concentrated in one specific area or distributed along the coast.