Tables 2 and 3 show the time-lined changes of top 10 characterized keywords of
Asahi-shimbun and Kahoku-Shinpo from first to fourth week. In this tables, Jaccard
index of time-tag (week 1, week 2, etc.) and keywords was used. From the Table 2
of Asahi-shimbun, we can find that keywords related to earthquake and tsunami
were particular in the first week. However, this situation changed after the second
Fig. 2 Time-lined change of keywords appearance of Asahi-Shimbun and Kahoku-Shimpo during
the first months. In these line charts, left axis shows the number of news articles concerning the
3.11, right axis shows the appearance ratio of each keyword
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R. Shineha and M. Tanaka