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The Fukushima Daiichi nuclear disaster that occurred on March 11, 2011, was caused by the Tōhoku tsunami, which was itself triggered by the devastating 9.0 Mw moment magnitude earthquake. This study investigates spatial and temporal changes of the suspended particulate matter (SPM) content in the North-Eastern part of Japan (Pacific Ocean) using a geostationary ocean color sensor. The Geostationary Ocean Color Imager (GOCI), which is centered on the Korean peninsula but could also observe the Japanese area, is able to acquire eight images per day, thus allowing the analysis of rapid daily changes in water mass. The analysis of GOCI data shows that SPM concentration notably increased both along the coast and within the Bay of Sendaï shortly after the tsunami. Motionless patterns of SPM were observed at 2, 14, 25, and 37 km from the coast. It is shown that SPM concentration rapidly decreased one month later. The SPM concentration did not remain high the following year, contrary to what was observed for the Sumatra Tsunami in 2004. The origin of SPM is also investigated in this study. Our analysis suggests that some of the SPM originates from the resuspension of bottom sediments due to the reflection of the tsunami on the coastline that leads to the migration of marine particles toward the sea surface. The fate of the SPM concentration is then discussed based on the analysis of meteorological conditions, river discharge, and tsunami wave properties. [ABSTRACT FROM AUTHOR]

This study demonstrates the skills of D-FLOW Flexible Mesh (FM) and SFINCS (Super-Fast INundation of CoastS) in combination with the Delft Dashboard Tsunami Toolbox to numerically simulate tsunami offshore propagation and inundation based on the example of the 2011 Tōhoku tsunami in Japan. Caused by a megathrust earthquake, this is one of the most severe tsunami events in recent history, resulting in vast inundation and devastation of the Japanese coast. The comparison of the simulated with the measured offshore water levels at four DART buoys located in the north-western Pacific Ocean shows that especially the FM but also the SFINCS model accurately reproduce the observed tsunami propagation. The inundation observed at the Sendai coast is well reproduced by both models. All in all, the model outcomes are consistent with the findings gained in earlier simulation studies. Depending on the specific needs of future tsunami simulations, different possibilities for the application of both models are conceivable: (i) the exclusive use of FM to achieve high accuracy of the tsunami offshore propagation, with the option to use an all-in-one model domain (no nesting required) and to add tsunami sediment dynamics, (ii) the combined use of FM for the accurate simulation of the tsunami propagation and of SFINCS for the accurate and time efficient simulation of the onshore inundation and (iii) the exclusive use of SFINCS to get a reliable picture of the tsunami propagation and accurate results for the onshore inundation within seconds of computational time. This manuscript demonstrates the suitability of FM and SFINCS for the rapid and reliable assessment of tsunami propagation and inundation and discusses use cases of the three model combinations that form an important base for tsunami risk management.

Abstract We conducted beach-cast debris transect surveys on Triangle Island, British Columbia, Canada in 2012–2017 to (1) establish a baseline against which to track future changes in stranded debris on this small, uninhabited island; and (2) time the arrival in western North America of debris released by the 2011 Tōhoku tsunami. Most (90%) of the six-year total of 6784 debris items tallied was composed of Styrofoam or plastic. The number of debris items peaked in 2014 (waste Styrofoam, rope) and 2015 (waste plastic, wood), and cumulative totals for all debris types were ca. 50% higher in 2014–15 than in 2012–13 and 2016–17. The peaks in 2014–15 probably represented the arrival of the bulk of the tsunami debris, based on close correspondence with forecasting models and debris surveys elsewhere. A fuller understanding of the movement of the Tōhoku tsunami debris will require information from other beach monitoring programs. Highlights • Beach debris surveys were conducted on Triangle Island, British Columbia, in 2012–2017. • Debris composed of Styrofoam and plastic comprised 90% of all items found. • Peaks in 2014–15 probably indicated the arrival of debris from the 2011 Tōhoku tsunami. [ABSTRACT FROM AUTHOR]

This study is the first to systematically quantify, categorize, and map marine macro-debris across the main Hawaiian Islands (MHI), including remote areas (e.g., Niihau, Kahoolawe, and northern Molokai). Aerial surveys were conducted over each island to collect high resolution photos, which were processed into orthorectified imagery and visually analyzed in GIS. The technique provided precise measurements of the quantity, location, type, and size of macro-debris (> 0.05 m 2 ), identifying 20,658 total debris items. Northeastern (windward) shorelines had the highest density of debris. Plastics, including nets, lines, buoys, floats, and foam, comprised 83% of the total count. In addition, the study located six vessels from the 2011 Tōhoku tsunami. These results created a baseline of the location, distribution, and composition of marine macro-debris across the MHI. Resource managers and communities may target high priority areas, particularly along remote coastlines where macro-debris counts were largely undocumented. [ABSTRACT FROM AUTHOR]

The present study focused on tracing tsunami-drifted objects under a real tsunami based on an integrated numerical method. Instead of a solitary wave that is much shorter and steeper than real-world tsunami waves, an extra-long tsunami wave is represented here in a nearshore region using a new approach. To this end, propagation of a seismic tsunami from the source to the nearshore region was simulated using two-dimensional depth-averaged equations. When the waves reached the target coastal area, the time series of the free surface of the tsunami was approximated by a theoretical relation based on a combination of several solitons, which were then used to solve the linearized trajectory equation of the wave-maker to generate the intended time series of the tsunami wave. Finally, in a nearshore model, the movement of drifted bodies under the generated tsunami wave was simulated based on the smoothed-particle hydrodynamics (SPH) method. In order to verify the accuracy of the proposed method in tracing the drifted bodies under a real tsunami, the giant fish-oil tank, which was transported about 300 m during the 2011 Tohoku tsunami of Japan, was selected as the benchmark. The results demonstrate that the time series of the long tsunami wave was successfully generated by the piston wave-maker in the GPU-based SPH model, and the proposed approach can be regarded as a suitable alternative for reproduction of a real tsunami. The results also showed that the simulated fish-oil tank properly followed the estimated trajectory in Ishinomaki but it was transported more than the reported distance, which was expected due to absence of a holding connection between the tank and the ground in the SPH model. It should be emphasized that this study is one of the first studies on three-dimensional tracing of a tsunami-drifted body during a real event, and the tracing can be more accurate in further simulations by applying higher-resolution topography data and faster computation systems that help include more details in the nearshore model. [ABSTRACT FROM AUTHOR]

Abstract: Tsunami waves and the subsequent natural oscillations generated by the 2011 Tohoku earthquake were observed by two high‐frequency (HF) radars and four tidal gauge records in Ise Bay. The radial velocity components of both records increased abruptly at approximately 17:00 (JST) and continued for more than 24 h. This indicated that natural oscillations followed the tsunami in Ise Bay. The spectral analyses showed that the tsunami wave arrivals had periods of 16–19, 30–40, 60–90, and 120–140 min. The three longest periods were remarkably amplified. Time‐frequency analysis also showed the energy increase and duration of these periods. We used an Empirical Orthogonal Function (EOF) to analyze the total velocity of the currents to find the underlying oscillation patterns in the three longest periods. To verify the physical properties of the EOF analysis results, we calculated the oscillation modes in Ise Bay using a numerical model proposed by Loomis. The results of EOF analysis showed that the oscillation modes of 120–140 and 60–90 min period bands were distributed widely, whereas the oscillation mode of the 30–40 min period band was distributed locally. The EOF spatial patterns of each period showed good agreement with the eigenmodes calculated by the method of Loomis (1975). Thus, the HF radars were capable of observing the tsunami arrival and the subsequent oscillations. [ABSTRACT FROM AUTHOR]

The 2011 Great East Japan earthquake triggered powerful tsunami waves, causing disastrous damages in a vast area and took more than 18,000 lives. Despite the unprecedented disaster, some of the buildings and concrete bridges located in tsunami-inundated areas survived and functioned as effective shelters for those who evacuated. It indicates that the disaster could be the product of other factors such as behavioral or environmental factor. In order to study the human impact in the 2011 Tohoku tsunami, it investigates the relationships among evacuation behaviors (i.e., evacuation starting time), preparedness before the disaster, and evacuee’s characteristics and survival rate of the 2011 disaster. Results show that behaviors during the disaster differentiated for the survivors and the dead and missing. A model is developed based on the analysis of each evacuation behavior factors on the fatalities; integrated strategies are proposed and discussed for the reduction of casualties in the future large-scaled natural disasters.

Since the Great East Japan Earthquake and the following Tōhoku Tsunami on March 11th, 2011, Japan has been facing a great challenge of the long-term and costly reconstruction of the impacted Tōhoku Coast, particularly in Iwate, Miyagi and Fukushima Prefectures, where the highest damage ratio was documented. The development of the recovery plans and the new tsunami mitigation strategies, aiming at more efficient protection from such future natural disasters, required in the first step revision of the performance and the efficiency of the tsunami countermeasures employed so far, consideration of the lessons learned from the reconstruction processes after past tsunami disasters as well as adjustment to specific regional conditions (e.g. society aging, diminishing population ratio, land availability, reconstruction visions preferred by local communities). The recovery policies established by the Government of Japan after the 2011 Tōhoku Tsunami promote a combination of three key countermeasures for the reduction of future tsunami risk, namely structural/non-structural coastal protection facilities (under particular consideration of the contribution of green coastal belts), land use regulations and emergency management. The reconstruction policy is presented in this paper with particular attention paid to the planned or already introduced structural/non-structural tsunami countermeasures (such as sea dikes, seawalls, coastal forests, embankments) and land use planning. [ABSTRACT FROM AUTHOR]

Post-tsunami field surveys in the Minami-Soma exclusion zone in the Fukushima Prefecture were delayed for 15 months after the 2011 Tohoku tsunami. The area was subject to access restrictions until June 2012 due to high radiation levels caused by the meltdown at the Fukushima Dai-ichi Nuclear Power Plant. The distribution of the measured tsunami heights is presented in combination with observed infrastructure damage. The enhanced tsunami heights in the areas along the shoreline are attributed to wave reflection, funneling and splash-up at cliffs and seawalls, as well as the increased flow resistance as the tsunami plowed through coastal pine-tree forests. Consequently, large tsunami heights exceeding 10 m were limited to areas within 500 m from the shoreline. Onshore profiles of the maximum inundation levels were dependent on inland topography: tsunami heights increased inland in steep V-shaped valleys, while decaying with inundation distance along flat coastal plains. Tsunami flood levels in the coastal plains are affected by the extent of seawall damage: coastal flood levels are higher behind completely destroyed seawalls than behind partially damaged coastal defenses. Remnant seawalls provided valuable lessons to be implemented in future designs of tenacious structures based on the Japanese concept of 'nebari' representing resiliency to endure tsunami overflow as the original design height is exceeded. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to build a run-up database using an analytical Green's function of 1D fully nonlinear shallow water equations over a uniform constant slope. The total mechanical energy, tsunami run-up height and inundation distance can be quickly derived once a submarine earthquake occurs. Only fast fourier transformation (FFT), multiplication and superposition are employed in the present algorithm. The in situ investigations of the 2004 Indian Ocean Tsunami and 2011 Tohoku Tsunami are used to validate the present methodology. Most calculated run-up heights are on the safe side and the inundation distance is reasonable. The computational procedure can be efficiently finished within a few seconds so that complete tsunami information can be provided after integrating the existing numerical Green's function database. [ABSTRACT FROM AUTHOR]

The observations of the upper atmosphere after the severe Tohoku earthquake of March 11, 2011 are analyzed. The observations cover the Hawaii region and span the time interval from about 7 h after the main shock to about half an hour before the arrival of the tsunami wave generated this earthquake. We explore the factors that are responsible for the emergence of the ionospheric response, which comprises a series of waves propagating ahead of the tsunami. The contribution of the moving tsunami wave into the formation of such a pre-tsunami response is established by the numerical simulation of the equations of geophysical hydrodynamics with two-dimensional geometry. [ABSTRACT FROM AUTHOR]

On the 11th of March, 2011, a subduction earthquake of magnitude Mw9.0 happened at the northeast of Japan, generating a tsunami which resulted in huge damage in Japan. Okada’s elastic fault model is used to generate the deformation of the sea bottom based on USGS sources and UCSB sources respectively. The shallow water equations are solved by the adaptively refined finite volume methods so that it can compute the propagation of tsunami in the Pacific Ocean efficiently. The computed time series of the surface elevation are compared with the measured data from NOAA real-time tsunami monitoring systems for model validation, and UCSB sources derive better results than USGS sources. Furthermore, one nested domain with fine grid and higher topography resolution is combined to compute numerically this tsunami spreading in the Bohai Sea, Yellow Sea, East China Sea, and North of South China Sea. The impacts on China Coast and seas are analyzed and discussed. The results show that the tsunami has almost no impact in the Bohai Sea and Yellow Sea. It has some kind impact on the East China Sea and South China Sea. However, maximum wave height on China Coast is smaller than 0.5 m. It is thus concluded that the 2011 Tohoku tsunami did not generate a significant influence on China Coast. [ABSTRACT FROM AUTHOR]

On 11 March 2011, a moment magnitude M = 9.0 earthquake occurred off the Japan Tohoku coast causing catastrophic damage and loss of human lives. In the immediate aftermath of the earthquake, we conducted the reconnaissance survey in the city of Rikuzentakata, Japan. In comparison with three previous historical tsunamis impacting the same region, the 2011 event presented the largest values with respect to the tsunami height, the inundation area and the inundation distance. A representative tsunami height of 15 m was recorded in Rikuzentakata, with increased heights of 20 m around rocky headlands. In terms of the inundation area, the 2011 Tohoku tsunami exceeded by almost 2.6 times the area flooded by the 1960 Chilean tsunami, which ranks second among the four events compared. The maximum tsunami inundation distance was 8.1 km along the Kesen River, exceeding the 1933 Showa and 1960 Chilean tsunami inundations by factors of 6.2 and 2.7, respectively. The overland tsunami inundation distance was less than 2 km. The tsunami inundation height linearly decreased along the Kesen River at a rate of approximately 1 m/km. Nevertheless, the measured inland tsunami heights exhibit significant variations on local and regional scales. A designated 'tsunami control forest' planted with a cross-shore width of about 200 m along a 2 km stretch of Rikuzentakata coastline was completely overrun and failed to protect the local community during this extreme event. Similarly, many designated tsunami shelters were too low and were overwashed by tsunami waves, thereby failing to provide shelter for evacuees-a risk that had been underestimated. [ABSTRACT FROM AUTHOR]

This study demonstrates the skills of D-FLOW Flexible Mesh (FM) and SFINCS (Super-Fast INundation of CoastS) in combination with the Delft Dashboard Tsunami Toolbox to numerically simulate tsunami offshore propagation and inundation based on the example of the 2011 Tōhoku tsunami in Japan. Caused by a megathrust earthquake, this is one of the most severe tsunami events in recent history, resulting in vast inundation and devastation of the Japanese coast. The comparison of the simulated with the measured offshore water levels at four DART buoys located in the north-western Pacific Ocean shows that especially the FM but also the SFINCS model accurately reproduce the observed tsunami propagation. The inundation observed at the Sendai coast is well reproduced by both models. All in all, the model outcomes are consistent with the findings gained in earlier simulation studies. Depending on the specific needs of future tsunami simulations, different possibilities for the application of both models are conceivable: (i) the exclusive use of FM to achieve high accuracy of the tsunami offshore propagation, with the option to use an all-in-one model domain (no nesting required) and to add tsunami sediment dynamics, (ii) the combined use of FM for the accurate simulation of the tsunami propagation and of SFINCS for the accurate and time efficient simulation of the onshore inundation and (iii) the exclusive use of SFINCS to get a reliable picture of the tsunami propagation and accurate results for the onshore inundation within seconds of computational time. This manuscript demonstrates the suitability of FM and SFINCS for the rapid and reliable assessment of tsunami propagation and inundation and discusses use cases of the three model combinations that form an important base for tsunami risk management. [ABSTRACT FROM AUTHOR]