河北文安5．1级地震前天津地区地下流体异常特征

Anomaly characteristics of subsurface fluid in Tianjin region before Wen′an earthquake with M_S5.1

分析了2006年7月4日河北文安MS5.1地震前,天津地区王3井、王4井水汞及潘庄井、高村井水位出现的前兆异常。研究结果表明,震前在震中区周边,流体观测前兆异常表现明显,但在空间分布上呈现出不均一、不连续的特征;位于不同构造位置井孔的相同观测项目,异常形态却不尽相同;从异常出现的时间上看,异常主要集中在短临阶段,并且有随着发震时间的临近而不断增多的趋势;热水井观测异常出现的时间要早于冷水井观测,尤其是处在地热异常区的观测点对异常反映更为灵敏。

This paper studied wen＇an earthquake with Ms5.1, occurred in Hebei Province on July 4, 2006. Before the earthquake occurrence, the precursory anomalies, such as water mercury of Wang3 well and Wang4 and groundwater level of Panzhuang and Gaocun wells, all showed irregular manifestation. The study results show that the subsurface fluid around the epicenter area has obvious precursory anomalies before earthquakes, but they are not uniform and continuous in space. The same observed item of wells situated in different tectonic location has different anomaly patterns of the subsurface fluid. From the appearing time of those anomalies, the anomalies are mainly concentrated on short-impending stage. The nearer the earthquake occurred, the more anomaly amount was. The anomalies appear earlier in hot water well than the cold one, especially for those wells, situated in geothermal anomalous region. They are more sensitive to the precursory anomalies.