Google has previously used the Person Finder tool, for example, during the Christchurch earthquake and the Egypt protests.
The Japan earthquake version of the tool currently lists about 5,500 records, but the number is rising quickly as news about the catastrophe spreads around the world. Although the tool can be useful for finding information about a friend or a loved one, Google warns users that it doesn't review or verify the accuracy of the data. Furthermore, all data entered will be available to the public, as well as viewable and usable by everyone.
Google's Crisis Center also shows a map of the earthquake, the latest related news and lists link to warning centers, disaster bulletin boards, and train and blackout information.
The Google Crisis Center is available here, but it also shows up on top of searches for "Japan earthquake" and similar phrases. During these times of disaster, it's good to see Google taking swift action and leveraging its vastly popular search engine to help people cope and find information.