大震前地震活动图像演变及中期向短期过渡的地震活动性标志

EVOLUTION OF SEISMICITY PATTERNS BEFORE STRONG EARTHQUAKES AND SHORT-TERM INDICATOR OF SEISMIC PRECURSORS

通过多震例分析，表明大震前地震活动图像具有类似的演变形式，即空段—背景空区—增强活动—条带—平静。地震平静可以看作是中期向短期过渡的地震活动性标志，从图像演变角度有助于识别异常平静，并有可能把震前平静的时间尺度缩短至几个月量级。

By analysing a number of earthquake cases, it is shown that seismic patterns beforestrong earthquakes have a similar evolutional stage: seismic gap (gap segment - back-ground gap) - incremental activity - seismic band - quiescence. From the view of theevolution of seismicity patterns, the abnormal quiescence can be well identified. Thetime scale of preseismic quiescence can be shortened to months, so that it may be usedas a short -term seismic precursor.