收集河北及邻区1970年1月—2015年11月的地震目录，通过分析张家口—渤海—威海地震构造带和河北平原地震构造带上地震的时空演化图像来研究河北地区中强地震前小震的活动特征。结果表明，张家口—渤海—威海地震构造带的小震在唐山7．8级地震前出现1～2年的稀疏现象，且震源区约50 km范围内出现2～3年的小震空段，该构造带4级以上地震在时间和空间上表现出“收缩—平静—扩张”和“分段活跃”的现象；河北平原地震构造带内的邢台老震区在发生中强地震前，震源区小震时空分布图像存在“密集—稀疏”的异常活动现象；张家口—渤海—威海地震构造带自1999年张北5．6级地震之后，地震的时空分布未出现明显的密集和稀疏现象。自2014年开始，在河北平原地震构造带的邢台老震区，小震出现相对“稀疏”异常，应给予关注。%We analyze the seismic spatial‐temporal evolution characteristic in Hebei and adjacent area by u‐sing the earthquakes catalog from January 1970 to November 2015 recorded by The China earthquake net‐works center .The result shown that prior the 1976 Tangshan earthquake the Zhangjiakou‐Bohai‐Weihai earthquake zones appeared 1-2 year’s sparse distribution of small earthquake and it preparation area had experienced a seismic gap lasted for 2 -3 years .In Zhangjiakou‐Bohai‐Weihaiearthquake zone ,the earth‐quake of magnitude greater than 4 spatial‐temporal distribution map show a “dense‐sparse‐expansion” dis‐tribution and piecewise seismically active features .The small earthquakes distribution do not show any ab‐normal feature in this earthquake zonesafter 1999 Zhangbei M5 .6 earthquake .The small earthquakes ap‐peared“dense‐spare” abnormal distribution phenomenon before the moderately strong earthquakes hap‐pened in Xingtai earthquake zone .Noteworthiness ,in Hebei basin the small earthquakes occurred in Xing‐tai earthquake zone appeared a sparse distribution abnormal since 2014 year .
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