This paper reports on the content analysis of tweet data tagged with “# Rescue” in the 2017 North Kyushu Heavy Rain disaster. The results are summarizeol as follows. 1) There were no more than 7.6 % tweets which were described place name, number of people and their situation etc. of 1,058 tweets tagged with “# Rescue”. 2) Almost of the tagged tweets consisted of news articles and messages about introduction how to the “# Rescue” and encouragement to survivors sent from news media companies and Twitter users out of heavy rainy areas. In conclusion, the literacy of writing tweet text by affected people is improving in disaster occurring situation. On the other hand, Twitter users outside of affected areas should restrict sending tweets.
If a big earthquake occurs, the associated tsunami will strike shore and cause tremendous damage to towns and people near the coast. But, it is afraid that the construction of a huge breakwater to mitigate tsunami damage have an adverse effect on aquaculture industry and inshore fishery.
The purpose of this study is to estimate the effect of multiple breakwaters installed offshore in parallel by applying a three dimensional numerical simulation model for the water behavior.
The placement of the multiple breakwaters permits that ships can go in and out, and daily life has little inconvenience, and marine products can increase under natural environments.
As a result, it is found that the energy of tsunami decays as the wave is divided into right and left by the first breakwater and hits the next breakwater.
Discussions on intangible disaster treatment from a view of inhabitants has got more lively. However, most of them tend to improve the present actions based on the top-down approach such as more information contents or more convenient tools, these improvements are short of bottom-up approach. This study researched inhabitants’ local expressions on disaster risk.
From 20 to 29 in February, 2016, we had the web survey. This survey checked how inhabitants express local situations and dangers based on weather warning levels about river flood, inside water inundation, sediment disaster, heavy snow.
The survey data was analyzed on the expressions of geography, action and treatment, situation and influence, and past disaster. In the result, there were some characteristic points on each expression and the tendency of expressions and some issues were found.
High possibility of occurrence of earthquake with M9 or lager in the Nankai subduction zone was pointed out by Cabinet Office of Japanese government. Local governments along the area revised estimation of tsunami damages and attempt to reconstruct action plans for the disaster prevention. However, according to Cabinet office of Japanese government, the coastal area near the rupture zone receives huge tsunami within a few minutes after the earthquake happens. To take actions against the severe situation, we need a high-speed, and high-accurate tsunami prediction system. Baba et al. (2014) investigated the possibility for use of a concept of tsunami amplification in the early tsunami prediction. They computed tsunami waveforms at the twenty pressure gauges of dense ocean floor network system for earthquakes and tsunamis (DONET) and at prediction points near shore. They found clear correlations between them because tsunami height basically depends on the topography (bathymetry) during its propagation. In this study, an early tsunami prediction system using the concept of tsunami amplification was societally implemented in 6 regional areas in Wakayama Prefecture. We constructed a tsunami database that contains pre-computed tsunamis offshore and nearshore from 1506 earthquake scenarios may occur in the Nankai subduction zones. The new system detects first arrivals of earthquake and tsunami from DONET data in real time, and calculate average value of absolute observed pressure values among twenty DONET stations. The value is used to select an appropriate scenario from the tsunami database. Prediction accuracy of the system was also investigated by using cases of the 1944 Tonankai earthquake and the scenario earthquake provided by the Cabinet office. As a result, we found that predicted inundation area to be overestimated as the safety of the prediction.