Soon after the April 14th earthquake hit, the JMA (Japan Meteorological Agency) issued warnings about possible “aftershocks of 6-lower or greater.” This was technically correct but the word “aftershock” may have caused people to assume that the worst was over. Of course, we know now that the worst was yet to come and that some people lost their lives because they returned to their damaged homes. After considering the issue, the JMA has decided to avoid using the word “aftershock” in similar situations in the future and to warn about more quakes “of similar or greater intensity” instead.
As far as I can see, this change in policy has not yet been reported in English-language media. The image you see is a page from a pdf issued by the JMA:
http://www.jishin.go.jp/main/yosoku_info/gaiyo.pdf
– Kirk