A post-event survey of the coastal impacts of Typhoon Hagibis was conducted in the Greater Tokyo and Shizuoka areas. The typhoon's intensive landfall generated the highest-level storm surges recorded ...in the study area with a maximum sea-level anomaly of nearly 2 m at the head of Tokyo Bay. Highly populated coastal areas in the inner sheltered part of Tokyo Bay were subject to only minor damage partially because the peak storm surge occurred during a low spring tide. High water levels along the coastline facing the Pacific Ocean mostly measured 4-8 m above the mean sea level, the exception being the Seisho coast, where extreme wave runup reached over 10 m above the mean sea level. The high water levels predominantly caused by energetic swells were comparable with the crest heights of defense structures in a broad range of the study area. The intensive typhoon did not trigger catastrophic flood damage, but caused minor flooding due to wave overtopping, and there was substantial damage to coastal infrastructures along the coast. This paper presents both an overview of and detailed information regarding the coastal impacts of the intensive typhoon along the highly altered coastline with complex geometry.
Assessing the risk of tsunami-driven debris has increasingly been recognized as an important design consideration. The recent ASCE/SEI7-16 standard Chapter 6 requires all the areas included within a ...22.5° spreading angle from the debris source to consider the debris impact. However, it would be more reasonable to estimate the risks using numerical simulation models. Although a number of simulation models to predict tsunami debris transport have been proposed individually, comparative studies for these simulation models have rarely been conducted. Thus, in the present study, an inter-model comparison for tsunami debris simulation model was performed as a part of the virtual Tsunami Hackathon held in Japan from September 1 to 3 in 2020. The blind benchmarking experiment, which recorded the transport of three container models under a tsunami-like bore, was conducted to generate a unique dataset. Then, four different numerical models were applied to reproduce the experiments. Simulated results demonstrated considerable differences among the simulation models. Essentially, the importance of accurate modelling of a flow field, especially a tsunami front, was confirmed to be important in simulating debris motion. Parametric studies performed in each model and comparisons between different models also confirmed that a drag coefficient and inertia coefficient would influence the simulated debris trajectory and velocity. It was also shown that two-way coupled modelling to express the interaction between debris and a tsunami is important to accurately model the debris motion.
A moment magnitude (
M
w
) 7.5 earthquake occurred on January 1, 2024, at the northern tip of the Noto Peninsula, Central Japan, triggering a large tsunami. Seismological and geodetic observations ...revealed the rupture of mapped submarine active faults. While proximal segment ruptures have been well resolved by previous research, far offshore segments have posed challenges for onshore-based inversions. This emphasizes the necessity for a comprehensive study on the fault through tsunami modeling. Here, we aimed to examine tsunami propagation and inundation using four different fault models to identify the general characteristics of the tsunami source and evaluate the complexities of earthquake- and submarine landslide-induced tsunamis. We identified the simultaneous rupture of two active fault systems as the most suitable model for explaining observed tsunami height and inundation; however, some inconsistencies with observations remained. The propagation process did not follow a concentric pattern but aligned with bathymetric heterogeneity. The findings also suggested potential amplification effects responsible for the devastation of the coast of Iida Bay and indicated a possible submarine landslide in southern Toyama Bay. The findings of the present work could benefit the exploration of a more realistic tsunami source model, considering the differences between observations and simulations. Such efforts, in collaboration with paleotsunami research, can contribute to the improved assessment of hazards from submarine active faults.
We investigated ship navigation records known as Automatic Identification System (AIS) data near the source region of the 2011 Tohoku, Japan, tsunami. The AIS data of 16 ships in the offshore ...navigation could be compiled by about 40 min after the tsunami generation. Most of the AIS data showed notable deviation of the ship heading from the course over ground during the tsunami passage. There was good agreement in terms of amplitude/phase between the ship velocity and the simulated tsunami velocity in the direction normal to the ship heading. An equation of motion due to wave drag and inertia forces was examined for an offshore movable floating body. We explain that the ship movement in the direction normal to the heading immediately responds to the tsunami current, and relative velocity between the ship and the tsunami current asymptotically become zero. This indicates the movement velocity of navigating ships in the direction normal to the heading derived from AIS data will work as an offshore tsunami current meter. We examined the AIS data during the 2011 Tohoku tsunami and showed these data could be useful for tsunami source estimation and forecast. The AIS data in the current framework will possibly be a crowd-sourced tool for monitoring offshore tsunami current and tsunami forecast.
Typhoon Faxai caused severe damages along the western shore of Tokyo Bay, Japan in September 2019. Retaining a relatively small radius of maximum wind, Faxai passed across the center of Tokyo Bay and ...caused intensive wind and waves. While the sea level anomaly recorded at several tide gauge stations along Tokyo Bay were at most 1 m, and no significant surge-induced inundation was found, locally concentrated damages and wave-induced hazards were observed around Yokohama, on the middle-western shore of Tokyo Bay. The observed inundation height around Yokohama was TP (Tokyo Peil) 4.2 m on average, and the highest runup, TP 10.8 m, was observed at a small hill directly behind the seawall in Fukuura, Yokohama. The estimated wave overtopping directions at each location varied from the northeast to southeast, and no clear correlation was found between the wave overtopping directions and the extent of observed coastal hazards. Based on these findings and investigations of recorded data such as wind and waves, it was deduced that locally concentrated damages and hazards around the middle western shore of Tokyo Bay may be explained by the unique features of a relatively compact Faxai and the topographical characteristics of Tokyo Bay.
The detailed understanding of tsunami hazard risk using numerical simulations requires a numerical model that can accurately predict tsunami inundation phenomena on land. In such models, the ...structural effects are indirectly considered using the variation of bottom roughness as a proxy for the differences in building densities. Only a few studies have conducted intermodel tests to investigate tsunami inundation in complex coastal urban cities. During the tsunami analysis hackathon held in September 2020, eight research groups met to have a detailed discussion on the current urban inundation problems. In this study, we conducted an intermodel comparison of the numerical tsunami models, using the data from physical experiments that were performed on a detailed urban model. Our objective was to investigate the necessary conditions of an accurate numerical model based that can ensure high reproducibility and practicality. It was confirmed that the accuracy of topographic data is an important parameter for tsunami inundation simulations in complex urban areas. Based on the computational cost and accuracy, we suggest that a resolution of 1 cm of topographic data is a sufficient condition for tsunami inundation simulations on 1/250 scale model.
In 2019, the Kanto-Koshin area and the Tohoku area suffered devastating damage from floods and sediment disasters caused by the record-breaking heavy rainfall that came with Typhoon No. 19 (Hagibis). ...In the same year, the heavy rainfall caused severe damage in the northern part of Kyushu area, such as Saga Prefecture, as well as the wind and rain disaster caused by Typhoon No. 15 (Faxai) in Chiba Prefecture. These disasters also highlighted the danger posed by a series of disasters that could cause extensive damage in large areas due to combinations of multiple factors. It is one of the missions of JSCE to compile and disseminate lessons learned from disasters in Japan for solving future challenging issues in managing infrastructures and mitigating disaster damage. This special issue on the storm and flood damage in 2019 in Japan includes valuable information on the disasters in 2019 from different disciplinary points of view, aiming to contribute to the growth and development of interdisciplinary academic fields of civil and environmental engineering.
Hydraulic experiments were conducted to estimate tsunami wave force acting on rectangular onshore structures. Used building models placed at several distances from a shoreline. Wave pressure was ...measured at points on exposed structures. Impact and standing-wave pressure at different points peaked at different moments in time, so tsunami force tended to be overestimated by integrating maximum wave-pressure distribution envelope. Measured total force was thus used to formulate tsunami force estimation equations. Hydrostatic formula was successful for structures near a shoreline, despite large scattering for structures far from a shoreline. Hydrodynamic formula was successful in all cases, although inertia was considerable for structures near a shoreline.
A numerical study which takes into account wave dispersion effects has been carried out in the Indian Ocean to reproduce the initial stage of wave propagation of the tsunami event that occurred on ...December 26, 2004. Three different numerical models have been used: the nonlinear shallow water (nondispersive), the nonlinear Boussinesq, and the full Navier-Stokes aided by the volume of fluid method to track the free surface. Numerical model results are compared against each other. General features of the wave propagation agreed very well in all numerical studies. However some important differences are observed in the wave patterns, i.e., the development in time of the wave front is shown to be strongly connected to the dispersion effects. Discussions and conclusions are made about the spatial and temporal distribution of the free surface reaffirming that the dispersion mechanism is important for tsunami hazard mitigation.
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Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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