foreshock sequence前震序列
foreshock series前震序列
earthquake foreshock前震
foreshock k前震
foreshock activities前震
foreshock activity前震活动性
quiescent foreshock寂静的前震
foreshock wave前震波
direct foreshock直接前震
N（名词） a relatively small earthquake heralding the arrival of a much larger one. Some large earthquakes are preceded by a series of foreshocks 前震 → compare aftershock