华北北部地区3次强震前地下流体异常场及其形成与演化机理

Anomalous Field of Underground Fluids and Its Mechanism of Formation and Evoluti on Before Three Strong Earthquakes in the Northern Region,North China

通过系统地收集与整理１９８９年１０月１９日大同－阳高ＭＳ６１、１９９６年５月３日包头西ＭＳ６４与１９９８年１月１０日张北－尚义ＭＳ６２地震前地下流体异常资料，对比与综合分析了异常的形态特征、空间展布特征、时间变化特征与时空演化特征，进而提出华北北部地区地下流体中短期异常场的形成与演化机理。研究结果表明，中期异常场是区域构造活动的结果，区域构造活动同时激发了局部构造活动的强化与震源体的生成与发展，局部构造活动的强化产生了地下流体的短期异常场，震源体发展到临震阶段时在震中区生成了地下流体的源兆异常场。

In this paper,some anomalies of underground fluids before the Datong Yanggao ea rthquake with M S6.1,October 19,1989,the western Baotou earthquake with M S6.4,May 3,1996,and the Zhangbei Shangyi earthquake with M S6.2,Janua ry 10, 1988,are collected and arranged in a systematic way,and some features of anomalo us form,spatical distribution,time change and time space evolution are analyzed by contrasting and synthesizing.On the base of those mentioned above,a mechani sm of formation and evolution of an anomalous field of underground fluids in the middle short stages in the no rthern region,North China is presented.It is result of that the anomalous field in the mid stage is formed by a regional tectonic activity,the regional tectoni c activity arouses and strengthens partinal tectonic activity,forms and grows a s eismic source,the strengthening of partinal tectonic activity forms an anomalous fi eld in the short stage,and when a seismic source is growed to impending stage,th e source anomalous field of underground fluids is formed in the epicentral area.