Abstract: On the basis of the hydrogeologic setting and atmospheric rainfall of the observation well,the direct causes of medium-term and broken line-type short-term anomalies of groundwater level and radon in North China are analyzed in this paper.It is suggested that the occurrence of water level anomalies might be attributed to the increase and decrease of rainfall amount,and the formation mechanism of these anomalies depends mainly on rainfall infiltration supply.The direct cause of radon anomalies is rainfall infiltration and mixing.It is proposed,therefore,that the relation between fluid anomalies and earthquakes can be explained by the mutual action of deep and shallow structures.The main arguments are as follows: the rainfall and the change of groundwater level may induce tectonic deformation of the shallow structures,which may activate the deep structures and hence cause the occurrence of earthquake;conversely,the activities of deep structures and the generation of earthquake may cause the increase of stress in shallow structures,while the effect of rainfall and groundwater may induce the activities of shallow structures.Therefore,groundwater anomaly induced by rainfall can be assigned to a kind of earthquake precursor in a broad sense.

Key words: underground fluid, precursory anomaly, infiltration, mixing, inducement mechanism, tectonic activity

摘要： 结合观测井孔的水文地质条件、大气降水资料,深入剖析了华北地区水位、水氡的中期和转折型短期异常变化的直接原因,认为水位异常是由于降水量的增大与减少造成的,其形成机制主要为降水渗入补给;水氡异常的形成原因主要为降水渗入-混合机制。进而提出“深浅构造的互动作用”,用以解释流体异常与地震的关系,其论点是:降水、地下水变化可诱发(活化)浅层的构造变动,而浅层构造活动又引发深部构造活动和地震的发生;反之,深部构造的活动和地震的孕育,使浅层岩石的应力增强,在降水、地下水的诱发作用下,可导致浅层的构造活动。降水引起的地下水异常是一种广义的地震前兆。

关键词: 地下流体, 前兆异常, 渗入, 混合, 诱发机理, 构造活动