# Utilization of ICT as a Digital Infrastructure Concerning Disaster Countermeasures in Japan
## 6 Utilization Potential of Social Media Mapping as a Digital Infrastructure
### Utilization of Twitter during the Heavy-Rain Disaster in Western Japan in 2018  
As the situation during disaster constantly changes, Twitter, which is a platform where users can submit short texts, images and videos, was the most used platform in Japan and was used for various purposes. Additionally, referring to [PERSON] et al. (2018) [33] and [PERSON] et al. (2019a, 2019b) [34; 35]. Twitter was used as the most powerful tool for information communication during the heavy-rain disaster in Western Japan in 2018. Therefore, the present study focuses on the use of Twitter among social media. Twitter, released in the U.S. in 2006 and in Japan in 2008, is a blog service in which users can submit what they are currently doing or feeling as well send short messages in the form of texts within 280 words (140 letters in Japanese) called \"tweets\". A big feature of Twitter is the hashtag function which serves as a symbol used to group tweets that can be searched and displayed. Hashtag is a word or phrase with the # symbol in front, and users can see a list of tweets with the same hashtag like a bulletin board. Adding a hashtag makes it easier for others to see \"what the tweet is about\". The used hashtags in tweets related to the heavy-rain disaster in Western Japan in 2018 can be organized as shown in Table 1. Table 1 clearly indicates that the attached hashtags changed with the passing of time. In terms of the characteristics of hashtags, (1) multiple different hashtags indicating the same content were created, (2) almost all tweets had hashtags and many had multiple hashtags, (3) most tweets contained hashtags of specific local governments affected by the disaster in addition to hashtags related to the disaster situation and calls for help, and (4) there were many tweets with hashtags of specific areas within Mabi-cho, Kurashiki City, Okayama Prefecture, which suffered severe damages and was frequently covered by media. Additionally, there were many cases where users with good intentions voluntarily organized rescue request information and retweeted such information even without hashtags to be spread. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**Hashtags during and Immediately after the Disaster**} \\ \hline \hline \multirow{7}{*}{Disaster situation} & \#disaster \#landslidedisaster \#landslides \#mudslides \#pouringrain \\  & \#heavydownpour \#Hiroshimalandslides \#dissisterHiroshima \\  & \#flooddamage \#fiverflooding \#tronentialair \#heavyrainfall \\  & \#raindamage \#heavyraindisaster \#heavyriamdamage \#flooding \\  & \#heavyrain \#submergence \#tonthevergeofsubmergence \#submergedcar \\  & \#house \\  & \#evacuation \\ \multirow{2}{*}{Evacuation} & \#(affectedlocalgovernment(preference/city/town))evacuation \\  & \#evacuationcall \#evacuationonder \#emergencywarning \\  & \#heavyrainfallwarning \#heavyrainfallemergencywarning \\  & (Including tweets obviously on someone’s behalf based on the context) \\ \multirow{2}{*}{Rescue requests and cooperation} & \#rescuerequestsforHiroshima \#rescuerequestsforEhime \\  & \#rescuerequestsforMabicho \#(disaster)rescue \#(disaster)relief \#SOS \\ \multirow{2}{*}{\#Pleasehelp \#HELP \#Landslideshelp \#helplandslides \#helpheavyrain} \\  & \#missing(person) \#safetyunknown \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Utilization of hashtags in tweets related to the heavy-rain disaster in Western Japan in 2018. Rescue Requests Using Twitter during the Disaster of the Heavy-Rain Disaster in Western Japan in 2018  
Regarding the heavy-rain disaster in Western Japan in 2018, the utilization of rescue request tweets was proposed by Twitter right after the disaster on July 10 th. An example of a rescue request tweet was shown to clearly explain the items that must be included in the tweets. The examples indicated that users must enter specific rescue requests, their address, the hashtag \"#rescue\", and (if possible) an attachment of images. Additionally, there was a cautionary note to immediately delete the tweet after being rescued.