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The Indian Ocean Tsunami occurred on 26 December 2004, causing serious damage in the Maldives, which is 2,000 km distant from the epicenter. A post-tsunami survey was carried out from 31 January to 4 February 2005. Tsunami height distribution, tsunami behavior in atoll and characteristics of tsunami disaster in atoll island were discussed through survey results. The height of tsunami traces in the Maldives ranged from 0.6 to 3.4 m. The trace height was not small even where there was a developed reef and even at island inside an atoll. The tsunami behavior appeared to be complex in an atoll. Several minutes were necessary for tsunami inflow to an atoll. Inertial force was small in the run-up process in some islands, but was not so in some islands. Because the Maldives consists of low-lying islands, a solid structure and artificial ground is required to improve the safety level of the Maldives.

This paper reports the results of field surveys of the 2004 Indian Ocean Tsunami in Southern Thailand and Northern Sumatra. After outlining the general state of the tsunami strike, tsunami height and distribution in Sec. 3, aspects of inundated flow such as current velocity (water particle velocity), fluid force, relation between inundation depth and the degree of damage to reinforced concrete buildings, shape and height of surge front, inundated flow with floating bodies, effects of coastal forest on reducing tsunami energy and force are discussed. Damage estimation problems are also discussed. A simplified theory for predicting the moving velocity of floating bodies with inundated flow is presented.

The Indian Ocean Tsunami on 26 December 2004 affected Sri Lanka, which is located 1,700 km from the epicenter. A field investigation was conducted along the southwest coast of Sri Lanka to measure tsunami trace heights, investigate the damage, and obtain correct information on the tsunami. The results of the field survey showed that the tsunami arrived on the southwest coasts two and a half hours or more after the earthquake. The average tsunami height was 5 m along the southwest coast and tsunami trace heights of 10 m were found locally. The tsunami destroyed a number of wooden and brick houses, damaged port and harbor facilities and coastal railways, washed away many vessels, and scoured the foundations of coastal structures. The port and harbor facilities such as the breakwaters, and rigid coastal houses continuing along the coast reduced the tsunami and lessened the damage that it caused.

Hydraulic experiments were conducted to investigate the characteristics of tsunami flooding on flat or declining ground, since it was clarified by the field survey that the severer tsunami damage was caused at the place where the coastal land inclines inland. The experimental results show that the pressure acting on the structure on the sloping bottom was at least twice that of the flat bottom under the experimental conditions.

A field survey to document the event that occurred in the coast of the Andaman and Nicobar Islands, India on December 26, 2004 was undertaken along the Tamil Nadu coast to estimate several items, including the wave run-up height, damage assessment and inundation areas in the different parts of the affected regions. The results of this field survey indicate that the tsunami inundation was heavier in the southern region along the Nagapattinam coast than the northern coast near Chennai; this was most likely due to differences in onshore topography. Consequently, the role of the onshore topography and its relationship with near-shore bathymetry needs to be evaluated in detail in order to prevent future catastrophes.

Propagation and inundation characteristics of the 2011 Tohoku tsunami on the central Sanriku coast are investigated through field surveys and numerical simulations using offshore wave recordings as incident wave conditions. The numerical model successfully reproduces the extent of flood areas as well as the distribution of tsunami heights along the intricate coastline except for run-up of extreme heights over steep slopes. The survey and computed results suggest significant variations of tsunami heights along the coastline. Their positive dependency on topographic slopes implies that the incoming tsunami propagates in standing wave mode to precipitous sites while in progressive wave mode accompanied by wave breaking over gentle slopes. Temporal-spatial analysis of wave properties in different bays reveals that the inner bay topography provides a clear contrast to inundation characteristics. The impacting waves have extreme heights due to the funnel effect and local wave resonances causing highly transient flooding in narrow V-shaped bays whereas tsunami surges over longer periods across innermost shores of U-shaped bays to produce large horizontal velocities during both run-up and backwash phases.

On March 11th, 2011, the Pacific coast of Japan was hit by a tsunami generated by the largest earthquake (M9.0) in the history of the country and causing a wide range of devastating damage. Using preliminary reported data from many sources, some topics such as tsunami fatality ratio and tsunami fragility curves for structural damage are discussed and compared with other countries. This paper aims to discuss the damage characteristics of this tsunami as well as its mechanism, as observed through field surveys conducted over the 4 months following the tsunami. The field survey covers 13 areas in the Miyagi prefecture from Kesennuma city in the northernmost region to Yamamoto town in the southernmost region. The arrival time of the first tsunami along the coastal areas in the Miyagi prefecture was confirmed by stopped clocks found during the survey. The damage mechanism of coastal structures such as breakwaters, seawalls, tsunami gates, and evacuation buildings was investigated and discussed. Damage characteristics for each area, i.e., urban areas, port, coastal structures, fisheries, and agricultural areas, were also summarized. The conclusions drawn from the data analysis suggest that experience and education (soft countermeasures) are important to reduce the loss of life, as shown for example in the Sanriku area. The field surveys indicate that wood and reinforced-concrete (RC) structures should be balanced to survive both earthquake and tsunami forces, and the structural design for buildings should be reconsidered after the example in Onagawa town. In addition, coastal structures for tsunami countermeasures (hard countermeasures) should be more properly designed for survival instead of becoming floating debris upon being overturned by a tsunami. The combination of both hard and soft measures is especially necessary for optimizing the outcomes following a great disaster. These recommendations should be taken into consideration in the reconstruction efforts for better tsunami countermeasures in the future.

Japan was hit by the tsunami generated by the greatest earthquake in the history of Japan. The authors conducted the post-tsunami field survey in Miyagi prefecture immediately after the event to measure the inundation depth and investigate damaged buildings. Most of the buildings surveyed were wooden houses and could be classified into 4 damage levels. The primary data of inundation depth and damage levels obtained from the field survey were used to create the tsunami fragility curves, which described the degree of structural damage as a function of the hydrodynamic characteristics of tsunami inundation. The developed fragility curves show that damage with more than a 50% chance of occurring is classified as minor damage, moderate damage, major damage and complete damage when the tsunami inundation depth is between 2.5–3.0 m, 3.0–4.0 m and 4.0–4.5 m and greater than 4.5 m, respectively. By comparing the developed tsunami fragility curves, wooden houses in the studied area have higher structural performance than those obtained from historical events in other areas. The new curves suggest that wooden houses will be severely damaged if the inundation depth is greater than 3 m and collapse if the depth is greater than 4 m while wooden houses from historical data can resist only 1–2 m. Moreover, wooden walls in Japan reduce the overall failure of a structural member because a wooden wall is easier to destroy (compared to brick walls in Thailand and Indonesia) and allows the tsunami to pass through, which reduces the pressure at the attacking front of the tsunami. The fragility curves are very important for the loss estimation and reconstruction plans of the city; they are also crucial for reducing the disaster damage from a future tsunami.

At 14:46 on March 11, 2011 (local time), a large earthquake of magnitude Mw 9.0 took place, generating a tsunami that caused severe damage to the east coast of Japan. To comprehensively record tsunami trace heights and impacts along the coastal region, the Tohoku Earthquake Tsunami Joint Survey Group was organized immediately after the event. As part of this group, the authors conducted a field survey in Miyagi and Fukushima Prefectures. The surveyed area can be divided into 2 parts from the point of view of its geographical features: the northern part (a rias coastal area) and the southern part (a coastal plain area). In this paper, the characteristics of the damage due to the tsunami in each area are analyzed by using both the results of the authors' own field survey and the Joint Survey Group. In the rias coastal area, inundation heights were more than 10 m, which resulted in the flooding of the low-lying grounds located at the inner part of the bays. The tsunami wave caused widespread destruction in this area, and coastal buildings (including reinforced concrete buildings) suffered severe damage. In the southern coastal plains, inundation heights were 5–10 m and the tsunami reached a few kilometers inland, though unfortunately there were not enough high locations or buildings for the residents to evacuate. In addition, an extensive line of coastal dikes and forests, which had been placed to protect the wide plains behind them, also suffered extensive damage. From these geographically dependent inundation and destruction patterns, a number of important lessons on how to modify and improve future risk management strategies can be obtained.

The behavior of the 2011 Tohoku earthquake tsunami in Tokyo Bay and its resultant damage to the coasts are studied using a field survey, an analysis of observed tsunami wave profiles and numerical hindcasting using FVCOM and Delft3D-Flow. The field survey reveals that the tsunami caused several fishery ports to overflow, and unexpectedly large inundation and run-up heights of 2.84 m and 2.91 m were recorded in Funabashi Fishery Port and Shin-Futtsu Fishery Port, respectively. Examining the observed tsunami wave profiles, the tsunami wave entered the bay with a maximum height of approximately 0.9 m for the second wave and a period of approximately 60 min, propagating along the major axis of the bay with almost uniform height. Numerical hindcasting results using both the models are fairly consistent with the measurements, revealing that the tsunami wave heights are locally amplified in ports because of wave reflection, water accumulation due to their narrow and enclosed shape, and, to some extent, the harbor resonance. Heavy damage to seaweed farming was also observed, especially around the Futtsu Cape and the northern part of the Banzu tidal flat, which numerical analysis attributes to the appearance of large hydraulic resistance on seaweed net.

Typhoon Haiyan (Yolanda) struck the islands of Leyte and Samar, the central part of the Philippines, on 8 November 2013, bringing large-scale devastation to coastal areas due to the high winds and large storm surge and waves associated with it. In order to obtain the distribution of storm surge heights and damage covering the wide stretch of affected coastline, the authors carried out a series of field surveys in the aftermath of the typhoon (in December 2013, May 2014, and October 2014). In the present paper, the authors detailed the results of these field surveys and summarized the characteristics of the storm surge and main causes of the damage, especially focusing on the Leyte Gulf coast, which is surrounded by the eastern coast of Leyte and the southern coast of Samar. Finally, the wide range of types of storm surge disasters were also discussed by comparing Typhoon Haiyan with other recent major events.

The 2011 Tōhoku event showed the massive destruction potential of tsunamis. The Euro-Japan “Risk assessment and design of prevention structures for enhanced tsunami disaster resilience (RAPSODI)” project aimed at using data from the event to evaluate tsunami mitigation strategies and to validate a framework for a quantitative tsunami mortality risk analysis. Coastal structures and mitigation strategies against tsunamis in Europe and Japan are compared. Failure mechanisms of coastal protection structures exposed to tsunamis are discussed based on field data. Knowledge gaps on failure modes of different structures under different tsunami loading conditions are identified. Results of the wave-flume laboratory experiments on rubble mound breakwaters are used to assess their resilience against tsunami impact. For the risk analysis, high-resolution digital elevation data are applied for the inundation modeling. The hazard is represented by the maximum flow depth, the exposure is described by the location of the population, and the mortality is a function of flow depth and building vulnerability. A thorough search for appropriate data on the 2011 Tōhoku tsunami was performed. The results of the 2011 Tōhoku tsunami mortality hindcast for the city of Ishinomaki substantiate that the tsunami mortality risk model can help to identify high-mortality risk areas and the main risk drivers.

On October 31 and November 1, 2002, two earthquakes of magnitude 5.4 and 5.3 hit the area at the border between the Molise and Puglia regions in Southern Italy. The damage pattern in the epicentral area qualified the quake as an intensity VII MCS event, although providing a notable exception relevant to the small village of San Giuliano di Puglia. Since the first macroseismic survey, it appeared clear that in S. Giuliano the intensity was two degrees higher with respect to three neighbouring villages located within a radius of 3 km. Soon after the quake, our team started a campaign of microtremor HVSR measurements (Horizontal to Vertical Spectral Ratio), then we installed accelerometers and carried out damage and geological surveys. Finally, we performed a geoelectrical tomography and two profiles of Vs velocity with depth using the NASW technique (Noise Analysis of Surface Waves). The preliminary observations indicate that ground motion amplification is present in S. Giuliano within the frequency band that may affect building. A strong velocity contrast 20 m deep causes the predominant peak. More amplification could be due to more complicated, 2D effects. As regards the damage pattern, it divides S. Giuliano in three zones showing different characteristics and seismic behaviour. A building-by-building survey is still under way to better evaluate vulnerability variations in different zones of the village. However, the acquired data so far is sufficient to propose site amplification as a possible cause of the damage enhancement observed in S. Giuliano.

In order to develop a rational methodology to evaluate building damage caused by tsunamis, first, disaster data collected in Thailand, Sri Lanka, and Japan are introduced as verification data. Next, the applicability of an empirical method of predicting inundation depth ( = the inundation height from ground level) based on analysis of those data and a numerical simulation method of tsunami flood is examined by comparing calculation values with the verification data. Then, the validity of a convenient method of evaluating building strength against the tsunami using the gate-type Rahmen Building Model is checked by comparing calculation results with actual damage and diagrams to get pillar widths or wall thicknesses at the breaking threshold for common sizes of buildings are proposed.

In this study, we investigated the sediment transport due to the 2004 Indian Ocean tsunami along the natural coast at Hambantota, Sri-lanka. Bathymetry and topography surveys before and after the tsunami were conducted and results showed significant erosion by the tsunami, especially around the places where shoreline discontinuations were observed. We conducted a numerical simulation of tsunami propagation as well as the bathymetry change induced by the tsunami. Furthermore, we also estimated the bathymetry change due to the usual sea waves at the coast. Our numerical results suggested that the tsunami has strong bottom shear stress at specific landform such as a river mouth and a cape. We also found that the sediment erosion and accretion due to the tsunami had been mitigated by usual waves after the tsunami.