Tsunami Events Research Articles

Effects of the 2011 Tohoku‐oki tsunami and human activities on long‐term coastal geomorphic development in northeastern Tohoku, Japan

AbstractThe 2011 Tohoku‐oki tsunami caused large‐scale topographic changes along the Pacific coast of northeastern Japan. More than 10 years have passed since the tsunami waves struck the area. Today, because of reconstruction work, very few places exist where natural post‐tsunami topographic changes can be monitored continuously. For this study, the authors investigated topographic changes caused not only by the 2011 tsunami but also by natural and artificial activities during the 50 years before and after the tsunami based on aerial photographs, excavations and subsurface explorations using ground‐penetrating radar at the Osuka coast in Aomori prefecture, Japan. The site is rare because it is a protected area with few and superficial engineering activities, making it suitable for continuous observation of pre‐tsunami, syn‐tsunami and post‐tsunami topographic changes. The findings indicate that the 2011 tsunami waves generated large topographic changes: depositional and erosional features produced by the tsunami can be recognized, respectively, as tsunami deposits and erosional channels across the sand dunes. During the post‐tsunami phase, the sand volume at the coast quickly recovered naturally. Tsunami deposits and the erosional channels were well preserved underground even at 10 years after the event. However, dynamic movement of the dunes started after the tsunami. The shifting was attributable to the artificial clearing of coastal forests rather than the tsunami effects on the coast. Our results first indicate not only that the sedimentary features of paleo‐tsunamis but also the erosional features have some probability of being preserved in the subsurface of the beach and sand dunes at tsunami‐affected areas. Also, artificial activities such as deforestation are much more crucially undermining of the stability of the coastal geomorphology than the tsunami effects: the coast is now reaching a different status from its pre‐tsunami situation.

Variation Parameters of The 2004 Indian Ocean Tsunami Model for Tsunami Prone Area Mapping in The Northern Part of Aceh Province

A total of ten tsunami events occurred in Aceh Province from 1991 to 2012. This condition confirms that AcehProvince is very vulnerable to tsunami hazards. In 2004, a tsunami occurred due to the activity of the subduction zone onthe west coast of Aceh with a magnitude of Mw 9.3. Since the 2004 tsunami, research on tsunamis has increased. The aimof this study is to reconstruct the 2004 tsunami models, to find out which models are suitable for the events of 2004. Thereare at least five models of earthquake source faults used for tsunami modeling in this study. The tsunami modeling wascarried out numerically using the Tohoku University’s Numerical Analysis Model Investigation (TUNAMI) programme.The maximum height obtained from the modeling is 58,05 m at the shoreline. The maximum height obtained from thebest model is 17,73 m on land. The M5 fault model produced a tsunami height model that best matches the observationresults validated by lowest RMS and highest correlation coefficient values Keywords: tsunami height, fault model, correlation coefficient, RMSE

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.

Random forest-based multi-hazard loss estimation using hypothetical data at seismic and tsunami monitoring networks

This article presents a novel approach to estimate multi-hazard loss in a post-event situation, resulting from cascading earthquake and tsunami events with machine learning for the first time. The proposed methodology combines the power of random forest (RF) with data that are simulated at seismic and tsunami monitoring locations. The RF model is well-suited for predicting highly nonlinear multi-hazard loss because of its nonparametric regression and ensemble learning capabilities. The study targets the cities of Iwanuma and Onagawa in Tohoku, Japan, where seismic and tsunami monitoring networks have been deployed. To encompass a diverse range of future multi-hazard loss estimation, an RF model is constructed based on 4000 simulated earthquake events with peak ground velocity and tsunami wave amplitude captured at ground-motion monitoring sites and offshore wave monitoring sensors, respectively. The incorporation of 10 ground-motion monitoring sites and five offshore wave monitoring sensors significantly enhances the model’s forecasting power, leading to a notable 60% decrease in mean squared error and 20% increase in the R 2 value compared to scenarios where no monitoring sensors are utilized. By harnessing the capabilities of RF and leveraging detailed sensing data, RF achieves R 2 values over 90%, which can contribute to enhanced disaster risk management.

Resonance characteristics of tsunami in bay of Japan by the Hunga Tonga-Hunga Ha’apai volcano eruption on 15th January 2022

The massive eruption of the Hunga Tonga-Hunga Ha’apai (HTHH) volcano in Tonga on 15 January 2022 at 04:15 UTC had a global impact and triggered an atmospheric wave and a tsunami. We first analyzed observation data from meteorological stations and tide gauges at 12 locations. Low-frequency trends in the observation data were removed by using a high-pass filter. Fourier and wavelet spectral analyses were applied to determine the frequency characteristics of the filtered data. Modal analysis was developed and used to investigate natural oscillation periods based on bathymetry. The results showed that the Lamb wave generated by the atmospheric pressure wave arrived ~ 7 and ~ 44 h after the eruption. The tsunami arrived ~ 11 and ~ 45 h after the eruption, which corresponded to the arrival time of the Lamb wave. The dominant periods of the Lamb waves were ~ 7.7 and ~ 7.5 min, and for the tsunamis they were ~ 9.9 and ~ 28.7 min. The periods derived from the spectral analysis matched the natural oscillation of the eigenperiod derived from the modal analysis, in eight out of the twelve stations. This study provides valuable insight and information regarding the nonseismic and far-field effects of tsunamis generated by volcanic eruptions.

Tsunami-driven debris hazard assessment at a coastal community: Focusing on shipping container debris hazards at Honolulu Harbor, Hawaii

A framework combining a tsunami flow model and debris (large floating object) transport model was developed to evaluate the kinematics of multiple debris and sequential hazards in a coastal community. We derive the analytic solution of the semi-analytic model of debris transportation, and adapt to evaluate the impact of tsunami-driven debris at Honolulu Harbor, Hawaii as a case study by simulating the motion of 2500 shipping containers under a hypothetical 2500-year tsunami event. The study provides a framework for assessing tsunami-driven debris hazards in a coastal community by introducing new types of intensity measures for tsunami-driven debris hazards. The final debris dislocation in the numerical debris transport model was quantitatively compared with the debris impact hazard region of the ASCE 7–22 method. This study introduces new types of hazard maps showing the intensity ratios of the debris dispersion, maximum impact loading, accumulated impact loading, and 5% exceedance impact loading. These new hazard maps characterize the potential impact loadings from debris dispersion on a community scale and display hotspots that show the strong intensity of the hazards from debris. The sensitivity of the new hazard maps based on the debris model parameters is also discussed.

Sediment analysis and historical context of the 2018 Palu-Donggala tsunami deposit, Indonesia

On 28th September 2018, a magnitude 7.5 earthquake occurred on the Palu-Koro strike slip fault near Palu, Indonesia. Shortly after, large tsunami waves generated by the earthquake and the submarine landslides it triggered, washed into Palu Bay. Here, we describe sediment characteristics of the tsunami deposits and present wave height models to provide a modern analogue for tsunamis occurring on strike slip faults. We analyzed 51 sediment samples from 21 sampling points on two transects at Palu City and one transect at Pantaloan. At Palu City, the tsunami inundated between 250 and 270 m inland. Sediments were massive, with landward fining from coarse sands (φ 0) to fine sands (φ 3.7) and weak upward fining sequences (by up to 1 φ). At Pantaloan the tsunami inundated up to 275 m inland. Sediments were massive, with landward fining from a few grains of gravel (φ −2) and coarse sands (φ 0.5) to fine sands (φ 2.5) and weak upward fining sequences (by up to 1 φ). Based on the sediment data the TSUFLIND model predicted: at Palu city flow depths of 1 to 8 m, and flow velocities up to 3.9 m/s; and at Pantoloan flow depths of 2 to 8 m, and flow velocities up 3.8 m/s. The boulder transport model was applied to data from heavy concrete blocks (0.8 to 4.9 tons) deposited by the tsunami between 46 and 125 m inland, and predicted flow depths of 0.8 to 4.3 m and flow velocities up to 5.6 m/s. The rapid attenuation inland of the tsunami flow depth is consistent with the event being partially generated by landslides caused by the Palu-Donggala earthquake. A study of Dutch colonial archives and historical data reveals at least six tsunami events have occurred in or near Palu Bay since 1920, suggesting a very short return period for such events, and a significant tsunami hazard to the area.

Quantifying surfcam imagery to measure the 2022 Hunga Tonga-Hunga Ha'apai tsunami along the California coast

On January 15, 2022, the eruption of the Hunga Tonga-Hunga Ha'apai volcano created a tsunami that reached a height of 20.5 m in the near field. The tsunami impacted the entire Pacific Ocean basin and was the largest tsunami to impact California since the 2011 Tōhoku tsunami. Videos recorded on surfcams during the event were downloaded from three sites along the California coast (Santa Cruz, Pismo Beach, and Santa Barbara Harbor). Airborne Lidar data, shadow projections, and vessel traffic information was used to rectify imagery instead of traditional field methods. Water level was extracted at 2 Hz based on the change in brightness relative to a fixed background object and filtered to remove swell and tidal influences. Tsunami inundation was captured at all three sites, with image extracted maximum tsunami heights measuring 1.42 m at Santa Cruz, 1.07 m at Pismo Beach, and 0.49 m at Santa Barbara Harbor. Comparisons to nearby in-situ water level measurements were made to calculate the accuracy, with a RMSE of 0.41 m, 0.52 m, and 0.17 m at each site, respectively. Analysis of surfcam extracted water levels measurements show promising results, and in combination with providing holistic monitoring of the scene, suggests an alternative platform for future tsunami events.

Real-time tsunami forecasting system with nonlinear effects using Green’s functions: application to near-shore tsunami behavior in complex bay topography

ABSTRACT In this study, a real-time tsunami estimation method was developed using the linear superposition of Green’s functions, which account for nonlinear tsunami effects around coastal areas. To this end, first, the nonlinear effects associated with the inundation and bottom friction and advection terms in a nonlinear long-wave model were investigated, focusing on large tsunamis around Urado Bay in Kochi Prefecture, Japan, which is at risk of future damage from tsunamis produced by the Nankai Trough earthquake. The results indicate that the effects of advection play a more significant role than those of the inundation and bottom friction in terms of accurately estimating near-shore tsunami propagation. Then, based on these results, Green’s functions were modified to account for the linearly approximated effects of the advection terms. By applying the developed method to tsunamis around Urado Bay, it was demonstrated that accurate estimations of the water surface level and flow velocity changes could be quickly obtained at any location around the bay. The developed method can be applied to real-time tsunami inundation forecasting and off-shore evacuation simulations of vessels to support optimal evacuation decisions.

Tsunami event in Flores: literature review

<p class="Abstract"><span lang="EN-GB">The Flores Sea has experienced devastating earthquakes with magnitudes >7 over the past 30 decades. It can trigger a tsunami and provide important theoretical, experimental, and field information. The seismicity study stated that the island of Flores had experienced tsunamis during the pre-instrumental period (1815, 1818, 1820, and 1836) and the pre-instrumental period in 1992. This study discusses the development of tsunami research in Flores using a literature review approach. The data source comes from the Scopus database, with data analysis using VOSviewer. The search results obtained a total of 22 documents, with the result that the 1992 Flores earthquake became the main research topic and the beginning of the era of modern tsunami science</span><span lang="EN-GB">.</span></p>

Resolving tsunami wave dynamics: Integrating sedimentology and numerical modelling

AbstractTsunamis are a major hazard along many of the world's coastlines. To understand the impact of these events, a sufficiently long record of previous events is needed, which can be provided by their sedimentary deposits. A number of past events have left extensive sedimentary deposits that can be used to understand the hydrodynamics of the tsunami. The ca 8.15 ka Storegga submarine slide was a large, tsunamigenic mass movement off the coast of Norway. The resulting tsunami had estimated run‐up heights of around 10 to 20 m on the Norwegian coast, over 30 m in Shetland and 3 to 6 m on the Scottish mainland coast. New cores were taken from the Ythan Valley in North‐East Scotland, where Storegga tsunami deposits have previously been found. High‐resolution sedimentary analyses of the cores, combined with statistical (changepoint) analysis, shows signatures of multiple waves. Moreover, detailed CT scans of the erosional basal surface reveal sole marks called skim marks. Taken in conjunction with the grain size and sedimentary fabric characteristics of the tsunami deposits, this indicates that the flow exhibited a high‐concentration basal component, with an initial semi‐cohesive phase and that deposition was dominantly capacity driven. A multiple wave hypothesis is tested by creating a high‐resolution numerical model (metre‐scale) of the wave inundation, coupled to a previously published regional model. The inundation model confirms that multiple waves passed over the site in agreement with the sedimentological analysis. The sensitivity of the model to the reconstructed palaeocoastal geomorphology is quantitatively explored. It is concluded that local palaeogeomorphological reconstruction is key to understanding the hydrodynamics of a tsunami wave group in relation to its sedimentary deposit. Combining sedimentological data with high‐resolution inundation modelling is a powerful tool to help interpret the sedimentary record of tsunami events and hence to improve knowledge of their risks.

Development of early warning system for tsunamis accompanied by collapse of Anak Krakatau volcano, Indonesia

Present tsunami warning systems have been specialized for earthquake-generated tsunamis, but rapidly evaluating the tsunamis caused by volcanic eruptions and/or volcanic sector collapses remains a challenge. In this study, we applied a numerical model to the 2018 Anak Krakatau tsunami event, which was generated by the sector collapse, investigated a tsunami prediction skill by the model, and developed a real-time forecasting method based on a pre-computed database for future tsunamis accompanied by such eruption of Anak Krakatau. The database stores spatiotemporal changes in water surface level and flux, which are simulated under various collapse scenarios, for confined areas in the vicinity of potential source. The areas also cover the locations of observation stations that are virtually placed on uninhabited island surrounding the source area. During an actual volcanic tsunami event, a tsunami is expected to be observed at the observation stations. For real-time tsunami forecasting, the most suitable scenarios to reproduce the observed waveforms are searched quickly in the database. The precomputed results under the identified scenarios are further provided as input for rapid tsunami propagation simulation. Therefore, an effective real-time forecasting can be conducted to densely populated coastal areas located at a considerable distance from the source, such as the coasts of Java and Sumatra. The forecasting performance was examined by applying the method for three hypothetical collapse scenarios assuming different sliding directions. We demonstrated that the tsunamis along the coasts were successfully forecasted. Moreover, we showed that the combination of a pre-computed database and the existence of observation stations near the source area was able to produce appropriate tsunami forecasting for the coastal area even in a volcanic event.

Tsunami wave characteristics in Sendai Bay, Japan, following the 2016 Mw 6.9 Fukushima earthquake

On 21 November 2016, a Mw 6.9 intraplate earthquake occurred off the Fukushima coast in Japan, triggering a moderate-size tsunami with amplifications and long oscillations along the Sendai Bay coast. Here, we apply a hybrid approach to hindcast the wave characteristics in the Sendai Bay during the 2016 tsunami event, by analyzing coastal tide records, spectral analyses, and tsunami simulations. Our analysis shows that tsunami wave on tide stations mainly carried wave periods of 3.8–22.5 min, triggered by source periods of 18.5–22.5 min. The long oscillation in Sendai Bay was due to longer period of >28.8 min, affected by the presence of edge waves and oscillation of Sendai Bay. High-energy wave was found to be significant in most oscillation periods inside the Sendai Bay and around the Oshika Peninsula. The spatial distribution of maximum spectral and simulated tsunami amplitudes also reveal that the radiated tsunami energy was entrapped in the nearshore areas, resulting in resonance amplifications in the Sendai Bay.

TURBULENT BORES–INDUCED SCOUR AND PORE PRESSURE VARIATIONS AROUND A VERTICAL STRUCTURE

The scour due to the highly turbulent tsunami inundation is also a major threat to nearshore infrastructure [Nakamura, et al., 2008]. Research on local sediment erosion during tsunami events has shown a correlation between scour formation, pore pressure variations, and soil liquefaction [Mioduszewski and Maeno, 2003]. To understand the structures’ capacity to withstand the tsunami bores, it is critical to assess scour formation and pore pressure variations around their foundations [Macabuag et al., 2018, Nicholas et al., 2020; Mehrzad et at. 2021]. Young et al. (2008) conducted laboratory experiments to study tsunami induced liquefaction failure on a sand bed with two different slopes of 1V:5H and 1V:15H. The correlation between soil liquefaction and scour showed a direct link with bed slope and pore pressure and the peak pressure increased as the bed slope increased. Concerning the hydrodynamic forcing factor, research conducted by [Chanson, 2006] showed that the hydrodynamic characteristics of tsunami inundation can be adequately modeled using dam-break waves. The prime objective of this study was to comprehensively investigate the interaction of a wide range of hydrodynamic conditions and beach slopes on the variation of the pore pressure and associated scour.

TSUNAMI WAVE LOADING ON A STRUCTURAL ARRAY PARTIALLY SHELTERED BY A SEAWALL

In recent years tsunamis have been recognized as one of the most catastrophic natural disasters in the world, highlighted by the 2004 Indian Ocean tsunami and the 2011 Tohoku earthquake and tsunami. These countries affected by tsunamis like Indonesia, Thailand and Japan usually arm their coast with sea walls to provide protection for coastal urban regions; however, surveys have found during both tsunami events, several sections of breached sea walls had led to extensive damage in those coastal regions (Dalrymple and Kriebel, 2005; Sato, 2015). Previous studies have examined the sheltering effect by macroroughness to individual structures, but limited knowledge is available on the sheltering and flow concentration effect by a partially standing wall to a field of structural array. The result from this experiment will serve to provide a better understanding on the tsunami loading variation induced by different length of partial seawalls, and help prepare more accurate hazard maps for tsunami events.

DEVELOPMENT OF SMARTPHONE APPLICATION TO SUPPORT TSUNAMI EVACUATION

Kamakura is a historical city situated along the Japanese coastline, which is at risk of being devastated by a tsunami due to its relatively flat topography and proximity to the Sagami and Nankai Troughs. Evacuation would play an important role to reduce the potential loss of lives resulting from a tsunami event. While carrying out evacuation drills is helpful to enable participants to take appropriate responses during an actual tsunami event, it is not realistic for all the residents to participate in such drills. Furthermore, as some coastal areas are renowned sightseeing spots, there might be many visitors who do not know the area well and struggle to evacuate in the event of a tsunami (Takabatake et al., 2017; 2020). Thus, the authors developed a smartphone application (App) that supports swift tsunami evacuation, which can be especially helpful for those who do not have sufficient knowledge about evacuation routes and refuge places. The present study aimed to investigate the effectiveness of the developed app, and to clarify its impact on people’s decision making with regards to evacuation behavior.

MANGROVE AND ITS IMPACTS ON WATER WAVES: A MODEL-SCALE LABORATORY STUDY USING 3D REPLICAS OF TYPICAL RHIZOPHORA

Mangroves, a major type of nature-based solution in the tropics and subtropics, were evidenced capable of reducing wave energy in tsunami and storm events. The typical species, Rhizophora with its complex root system, was found effective in wave attenuation (Tanaka et al. 2007) and was studied experimentally using artificial tree models (e.g. Maza et al. 2019). To investigate the impacts of mangrove roots on water waves at a finer scale, we conducted experiments using 3D-printed models that replicated the geometry of natural Rhizophora. This study discusses the resistance of mangrove roots and their impacts on fluid velocity and turbulence.

TRANSITION OF TSUNAMI-LIKE LONG WAVES FROM A BASIN INTO A CHANNEL WITH OUTFLOW JET

Intrusion into rivers is an important aspect of the tsunami hazard. Tsunamis change their waveform and amplitude when they pass through a river mouth, and tend to increase the mean water level for a long duration of time once they have intruded the river (Tolkova et al., 2015). Understanding the ocean-to-river transition of a tsunami is crucial for predicting tsunami effects upstream, although the transition processes are complicated by a variety of factors such as bathymetry, river discharge, vegetation, and man-made structures like jetties and seawalls. To identify key fundamental mechanisms for the tsunami intrusion into rivers, we conduct laboratory experiments of tsunami-like long waves transitioning from a wide basin (ocean) into a narrow channel (river).

Precambrian tsunamis in the light of the modern data

Background. In the geological history of the Earth, tsunami events attract particular research attention. Such events are assumed to have taken place already since the Precambrian period. However, the information on Precambrian tsunamis requires systematic generalization. Aim. To generalize the data published on Precambrian tsunamis with a particular focus on their age, distribution, and possible triggers. The character of information about these natural catastrophes also presents interest. Materials and methods. A bibliographical review was conducted based on the developed systematization criteria. The information was collected with the Scopus database. A total of 39 sources (articles in the leading scientific journals) were analyzed. Results. The evidence of tsunami events was obtained for a large part of the Precambrian interval for different regions of the planet. The highest concentrations of the studied catastrophes were established for the end-Early Archean and the Early Proterozoic. Cosmic impacts and earthquakeswere indicated among the triggers. The oldest tsunamis were commonly interpreted by analyzing the composition and textures of rocks. These interpretations frequently proposed no alternative explanations. Discussion. The available information on Precambrian tsunamis lacks completeness. Two hypotheses were formulated, those assuming the influence of the varied frequency of cosmic impacts and the initiation of lithospheric plate tectonics on the occurrence of tsunamis in the Precambrian. Conclusion. Previous studies suggest a wide manifestation of tsunami events in the Precambrian. Further research in this direction seems promising, both for Russian and foreign geologists.

Location Tracking of Drifting Container by Solitary Wave Load Using a Motion Analysis Program

Objects adrift can cause considerable damage to coastal infrastructure and property during tsunami and storm surge events. Despite the potential for harm, the drifting behavior of these objects remains poorly understood, thereby hindering effective prediction and mitigation of collision damage. To address this gap, this study employed a motion analysis program to track a drifting container's location using images from an existing laboratory experiment. The container's trajectory and velocity were calculated based on the positions of five markers strategically placed at its four corners and center. Our findings indicate that the container's maximum drift velocity and distance are directly influenced by the scale of the solitary wave and inversely related to the container's weight. Specifically, heavier containers are less likely to be displaced by solitary waves, while larger waves can damage coastal structures more. This study offers new insights into container drift behavior induced by solitary waves, with implications for enhancing coastal infrastructure design and devising mitigation strategies to minimize the risk of collision damage.