During the 2011 East Japan Earthquake and Tsunami, newly popular social media such as Twitter and Facebook served as a lifeline for directly affected individuals, a means of information sharing, and a way for people inside and outside Japan to volunteer and to provide information-based support to affected individuals. Social media was used to perform vital relief functions such as safety identification, displaced-persons locating, damage information provision, support for disabled individuals, volunteer organization, fund-raising, and moral support systems. This study discusses the potential for public, civil society, and government organizations to utilize social media in disaster preparedness and response.

View full abstract

The 2004 Indian Ocean tsunami was one of the world’s worst tsunamis and caused devastating damage in many Asian countries. Then, in 2011, Japan was hit by a tsunami that was generated by the greatest earthquake in the country’s history. This paper discusses the damage caused by these tsunamis and subsequent reconstruction. Introduced first are the experience gained and lessons learned for future tsunami mitigation, such as tsunami awareness, proper evacuation building and the memorial parks created in the countries affected by the 2004 tsunami (Indonesia, Sri Lanka and Thailand). Second, the damage by the 2011 tsunami to structures designed to protect against tsunamis is summarized. Most of these structures could not withstand and protect from the tsunami because they were not designed for such a large tsunami. Human casualties and building damage are discussed using fatality ratios and fragility curves, respectively. These analyses show that experience and awareness help reduce human casualties in the Sanriku area, and wooden houses damaged by the 2011 tsunami fared better than in previous historical events. Finally, examples of ongoing reconstruction in Japan are introduced. Most reconstruction efforts were planned after considering the lessons learned from the tsunami’s impact, and the towns in question are now strengthening their disaster prevention-related plans to be better prepared for future tsunamis.

View full abstract

The 2011 Great East Japan Earthquake/Tsunami was a magnitude 9.0 Mw event that destroyed most structural tsunami countermeasures. However, approximately 90% of the estimated population at risk from the tsunami survived due to rapid evacuation to higher ground or inland. In this paper, we introduce an evacuation model integrated with a numerical simulation of a tsunami and a casualty estimation evaluation. The model was developed in Netlogo, a multi-agent programming language and modeling environment for simulating complex phenomena. GIS data are used as spatial input information for road and shelter locations. Tsunami departure curves are used as the start time for agents deciding to evacuate in the model. Pedestrians and car drivers decide their own goals and search for a suitable route through algorithms that are also used in the video game and artificial intelligence fields. Bottleneck identification, shelter demand, and casualty estimation are some of the applications of the simulator. A case study of the model is presented for the village of Arahama in the Sendai plain area of Miyagi Prefecture in Japan. A stochastic simulation with 1,000 repetitions of evacuation resulted in a mean of 82.1% (SD=3.0%) of the population evacuated, including a total average of 498 agents evacuating to a multi-story shelter. The results agree with the reported outcome of 90% evacuation and 520 sheltered evacuees in the event. The proposed model shows the capability of exploring individual parameters and outcomes. The model allows observation of the behavior of individuals in the complex process of tsunami evacuation. This tool is important for the future evaluation of evacuation feasibility and shelter demand analysis.

View full abstract

  Fragility curves, the relationships between three kinds of building damage ratios, i.e., total collapse ratio (TCR), collapse ratio (CR) and damage ratio (DR), as well as ground motion characteristics, i.e., peak ground acceleration (PGA), peak ground velocity (PGV), Japan Meteorological Agency instrumental seismic intensity (IJMA) and spectral intensity (SI), were studied for the 2011 Tohoku Earthquake. It was found that the DR was related better to ground motion characteristics than the TCR and CR during this earthquake, and the correlation between the DR and any one of the PGV, IJMA or SI indices was almost the same. The DR during the 2011 Tohoku Earthquake reached almost the same level as that during the Kobe Earthquake for the same level of ground motions. There were some districts where the DRs did not always correspond to reasonable levels of ground motion characteristics. One reason for this was considered to be the representativeness of the ground motions over each district. Thus, one method of estimating ground motions at damaged sites was proposed by using the underground velocity structures identified from the H/V spectral ratios of microtremors, after we confirmed the consistency of the H/V spectral ratios between earthquakes and microtremors. It is expected to be used for the construction of fragility curves with greater accuracy.

View full abstract

  We evaluated the performance of pedestrian bridges as vertical evacuation sites during the 2011 Tohoku tsunami in six prefectures in Japan. Evaluation was performed by considering the vulnerability and tsunami hazard characteristics as parameters that influence the damage probability. Vulnerability is represented by the exposure, indicated by the bridge’s position from the shoreline relative to the maximum inundation distance. In contrast, tsunami hazard was identified from the observed flow depths relative to the bridge’s height. We found that pedestrian bridges that were positioned inside an area less than 0.2 times that of the maximum inundation distance (which is 6 km), or where the tsunami flow depth exceeded that of the bridge’s height by more than 1.5 times, have a high probability of being damaged by a tsunami. It is necessary to consider such limitations when determining the placement criteria of pedestrian bridges as evacuation shelters for the above areas. Starting with the concept of sudden expansion phenomenon, a series of numerical exercises was conducted to parameterize hydraulic conditions that affect the sudden drop in water level due to the building configuration at an intersection. We searched the areas where pedestrian bridges could still be used for evacuation with the existing height. Preliminary results indicate that if the sudden expansion ratio (D) > 1.5, and the ratio between the widths of road to the width of residential blocks (β) < 0.1, sudden expansion occurs with hydraulic gradient dependent on the Froude number (Fr). In this condition, the bridges can be used for evacuation as long as they are installed on the side of the road parallel to the coastline, or on the landward side of the road at an intersection. These results provide the opportunity to apply more distributed evacuation shelters to relatively flat and populated areas.

View full abstract

Information on the tsunami arrival time for people located along a coastline is crucial for community-based tsunami preparedness activities. It is also important for tsunami source mechanism studies to support other field observation data such as run-up heights, co-seismic subsidence and eyewitness accounts. In this study, we reconstructed the tsunami arrival times along the east coast of Japan during the 2011 tsunami. As most of the tide gauges were damaged, first we collected and analyzed the arrival time data from equipment that survived the tsunami. The tsunami waveforms offshore were taken from six GPS buoys covering the Fukushima coastline in the south to Aomori in the north. Next, we utilized the records from stopped clocks found in the tsunami affected areas to briefly view the inundation arrival time. In addition to the observed run-up data, we used the above-mentioned arrival time information to propose and validate a new source mechanism for the 2011 Japan tsunami. The well-validated source model was then used to obtain the characteristics of the tsunami arrival time along the east coast of Japan. The results can be used as primary information for designing a community-based evacuation plan and increasing community awareness of tsunamis.

View full abstract

The enormous Mw 9.0 earthquake with a hypocenter off Sanriku-oki that occurred at approximately 14:46 (JST) on March 11, 2011, and the subsequent tsunami, caused serious damage along the Pacific coast of Iwate, Miyagi, and Fukushima. The damage to infrastructure was remarkable, and the damage to the railway caused by the tsunami was the greatest damage ever to occur to the railway. JR-East reported that they checked the damage caused by only the tsunami along seven lines, which had a total distance of 325 km, and the form of damage varied by line.
This paper summarizes the damage to the railway (including damage to vehicles) and the evacuation guidance situation for each line and investigates how the trains were damaged based on the numerical analysis of the 2011 Tohoku Earthquake Tsunami.

View full abstract