关键词: 地下流体, 前兆异常, 渗入, 混合, 诱发机理, 构造活动

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