Abstract
During the Great East Japan Earthquake, communication via Twitter attracted a great deal of attention. The aim of this paper is to quantify the actual level of Twitter-based communications related to the earthquake from data for 77 hashtags that was collected during a three-month period following the Great East Japan Earthquake. From some basic statistical analyses of the data, it is clear that, although there were a few earthquake-related peaks during April and May, the use of most hashtags gradually decreased following the earthquake. Utilizing NLP technology, differences in topic across the various hashtags were analyzed. Moreover, employing methods of social network analysis, the monthly changes in the relationships between the hashtags were analyzed and the organizational trends for each hashtag and the shifts in major topics were also extracted. Based on those analyses, some proposals are stated for the use of hashtags at the time of natural disasters.
