河北平原地震带地裂缝与地震活动

３０年来在河北平原地震带出现地裂缝４０２条处，其中至少有７１．５％是构造地裂缝。调查发现，它们和现代中小地震都存在着长４—５年的活动小周期，直接受地应力活动支配，两者有成生联系。此外，本区地应力、地下水位、地震和地裂的活动高潮依次滞后几月至２年，先后出现组成系列，四者都是区域地应力增强的反应。

GROUND FISSURES AND SEISMICITY OF THE HEBEI PLAIN SEISMIC BELT

In the recent 30 years ground fissures have developed at 402 sites in Hebei Plain,among which at least 71. 5% of them resulted from tectonic ground fissures. It has been found out that they are related with the medium-sized and micro-earthquakes in recent years and controled directly by the activities of crustal stress,Both the fissures and the earthquakes could be active for as long as 4 to 5 years. Furthermore,the maximum crustal stress,the high level of ground water,the earthquakes as well as the activity of ground fissures inthe area were delayed form several months to two years respondingly,and they,occutred as a series of events. all the four factors mentioned were influenced by the increase of the crustal stress in the area.