Today, there are many different social communication platforms (eg. Facebook,Twitter, LinkedIn Google+,mixi and so forth).Internet users are spending more time on social media. Twitter which is a kind of microbloglaunched in October 2006, hasbecome one of the most popular social communication tool in Japan. Because of Twitter's characteristic features such asimmediacy, easiness and bi-directionality, Twitter's timeline instantly reflects the real world. Once a major event happens,thenumber of tweets rapidly increases. In this article, this phenomenon is defined as 'burst'. The authors gathered Japanese tweetson public timeline from Twitter API over a period of four months starting from March 14, 2012 to July 13, 2012. We collected atotal of 1,379,844,343 posts from 58,866,923 distinct users. This study shows that tweets in bursty term are more retweet, lessreply and less charcters than usual. We have detected four types of bursts by cluster analysis. And the Japanese scale ofearthquake and the distance from epicentre to Tokyo have significantly affected occurrance of burst on Twitter.