precursor 復習

　気象庁は、最大マグニチュードの南海トラフ地震に備えて、臨時警戒情報を発表しました。
Nankai Trough quake early warnings planned

TOKYO (Jiji Press) — The Japan Meteorological Agency said Thursday it will work to disclose its assessment of abnormal phenomena that could possibly lead to a massive earthquake along the Nankai Trough off the Pacific coast from central to southwestern Japan as early as two hours after observing such precursors.

The agency plans to initiate the scheme on a provisional basis at noon Wednesday.

The new program comes after the government last month decided to review its disaster management measures for the so-called Tokai earthquake, a possible powerful temblor focused on Shizuoka Prefecture based on the special law on responses to large-scale earthquakes.

Among the three major scenarios the agency assumes is that a magnitude-8 level earthquake that occurs on the east side of the Nankai Trough may trigger an earthquake on the west side.

The other two scenarios are that a magnitude-8 level main temblor may occur after a magnitude-7 level foreshock and that the agency observes an abnormal slide of oceanic and continental plates there.

http://the-japan-news.com/news/article/0004028254

　取り上げる単語は"precursor" /prɪkˈɚːsɚ/ です。"pre"が語頭に付いているので、「以前の、あらかじめ」という意味がある単語だと予想できます。『ジーニアス英和辞典』第４版（大修館）で調べてみると、「先駆者、前任者、前兆」という意味があることが分かりました。ここでは、地震の予測なので、「前兆」という意味で使われています。LDOCEでは、"something that happened or existed before something else and influenced its development"と定義されています。(Akim)