Social networks already become emergency communication systems during disasters, with users spreading information and looking for on-the-ground updates. Twitter hopes to optimize this in Japan with Lifeline, a partnership between the company and Japan's local and regional governments. Launched this week, the tool lets users search Twitter for a postal code and see accounts of people tweeting about any disasters in the area, as well as media, utility company, or other accounts that could provide information. Eventually, Twitter says it could be expanded to other countries, though we obviously haven't been able to see it in action yet.

Lifeline is essentially a more sophisticated and curated version of the searches people do now, something Twitter users have certainly suggested before. Twitter isn't the first network to set up disaster services in Japan, either — earlier this year, Facebook introduced a "Disaster Message Board" that lets users mark themselves safe during an emergency.