地震前井水位下降型异常成因的LOCF模式

LOCF" MODEL ON THE FORMATION OF THE SUBSIDENCE TYPE ANOMALY OF WELL-WATER LEVEL PRIOR TO EARTHQUAKES

本文综述了国内外对震前地下水位下降型异常现象研究的现状,指出该异常具有规律性和复杂性的双重表现,提出了“震前应力集中区的‘断层裂隙带裂隙开合的渗漏模式”——LOCF模式。LOCF模式的中心思想是求解平面问题中的变强度线汇的降深场,在观测水层是承压水层的情况下,作者从单井定流量抽水降深的泰斯(Theis)公式出发导出平面连续点汇的微分降深表达式,通过对平面连续点汇微分降深场在时、空上的叠加给出了平面连续线汇降深方程的一般表达式。文中还计算了定流量平面连续线汇条件下,由于裂隙开合而得到的水位下降型理论曲线实例,由此分析出,只有通过变流量平面连续线汇的降深方程才能模拟实际观测到的水位下降型异常曲线。文中最后还对某些有关问题进行了讨论。

In this paper, the studies on the subsidence type anomaly of well - water level prior to earthquakes in various countries are overviewed. It is pointed qut that the anomaly exhibites both regularity and complexity, and any formation, theory for this anomaly should explain the twofold behaviours perfectly.'The leaking flow model on fissures opening - closing of fault fissure zone in stress concentration region prior to earthquakes'(LOCF model)is proposed. The basic idea of the model is to solve drawdown field equation on linear sink with variable strength in planar problem. Under the conditions that the observational water layer is an aquifer,and base on Theis's formula of drawdown used by pumping water with fixed discharge from a single well,the authors have deduced the differential drawdown equation of the plane continuous point sink,and through the integration of which in time and space,obtained a general expression of drawdown equation on the plane continuous linear sink. For the conditions of the plane continuous linear sink with fixed discharge,an example of theoretical curve on the water level lowering type caused by the opening -closing of fissures has been calculated. It follows that only by the drawdown equation of the plane continuous linear sink with variable discharge can we fit the observed abnormal curve of water level lowering type. Finally,the authors also discussed some problems in connection with this subject.