张北-尚义地震前地下流体异常特征分析

THE CHARACTERISTICS OF SUBSURFACE FLUID ANOMALIES BEFORE ZHANGBEI-SHANGYI EARTHQUAKE

分析了华北北部地区（3～42°N，110～120°E）张北-尚义地震前出现的地下流体各测项异常。研究结果表明：异常数量多，可靠异常达36项，且流体物理异常多于化学异常；异常形态复杂，地震地下流体异常各种形态均有所表现，并以水位的趋势上升异常占优势；中长期、中期和短期异常多，临震异常不突出，震时异常显著；异常时空演化过程中，总体上呈现出异常数量由外围向震中区，由中长期向短期逐渐发展的趋势，但同时也表现出空间分布上此起彼伏，时间进程上时起时落的特征。对沿着NW向构造带出现的一批1994年同步转向上升的长趋势水位异常和水氧上升、下降长趋势异常是否完全由本次张北-尚义地震所引起，还有待进一步研究。

The study On the anomalies of subsurface flulds occurred before Zhangbei-Shangyi earthquake in northern part of China (110°～ 12O°E ， 38°～42°N) shows that: ①There are a large number of subsurface fluid anoma1ies before this earthquake, and there are more physical anomalies than chemical anomalies. ②The forms of the subsurface fluid anomalies are very complicate ， and all kinds of anomaly forms before this earthquake have been found. The up-rising water level anomaly is predominant. ③Anomalies appear more in the impending term than that in the long, medium- and short-term ，and the co-seismic anoma-lies are prominent. ④In the process of anomaly development, one anomaly fell while an-other rose. The problem of whether the anomalies of all the long- and medium-term water level and radon are related to Zhangbei-Shangyi earthquake still needs a further research.