When the earthquake hit northern Japan on Friday, voice calls from mobile phones became immediately unavailable in order to leave room for emergency calls. However, in the Kanto area, mobile Internet connection was mostly kept on, and many people turned to the Web to exchange information.
On Japan's main social networking site, mixi, some communities were set up soon after the quake to keep people informed. The largest one now has over 300,000 members and it has guides to communities by region and purpose.
Mixi also has a function that displays how recently your friends logged in, so you can check if your friends have accessed mixi after the quake. Another feature, ashiato (footprints) — which was once one of the key attractions to mixi — shows when another user viewed your page (profile/diary/message/etc). While it is possible to send messages to your most important family and friends, features that do not require any direct interaction meant that even those who are not close friends can see who is OK.