In the months after the disaster, volunteers roamed shelters in hard-hit areas and posted pictures online of handwritten lists with survivors' names and locations, to help family get in touch. Services such as Google's Person Finder, a public database with information on individuals in disaster areas, were widely used by individuals and government organizations to keep track of survivors.
The use of social networks like Twitter jumped in the days after the disasters. A survey by local marketing firm IMJ two weeks later found a surge in new users signing up mainly to get information about their friends and family.
Japan's official government agencies are also increasingly using services such as Twitter to make official announcements. On Wednesday the Tokyo Fire Department started its official account, @Tokyo_Fire_D.
The next meeting on using social networks to make emergency calls is due to take place in November.