唐山7.8级地震地电阻率临震功率谱异常

POWER SPECTRUM ANOMALY OF EARTHRESISTIVITY IMMEDIATELY BEFORE TANGSHAN EARTH-QUAKE M7.8

对昌黎地电阻率台1973—1978年的资料进行了功率谱分析,发现在1976年7月28日唐山7.8级大地震的前后二个多月,特别是临震前半月,该台地电阻率连续出现了半日周期的幅度异常和频次异常,其幅值超出平时观测误差5—20倍,临震前脉冲月频次异常较平时背景高出3—4倍。分析得出,此种地电阻率半日周期功率谱异常的出现是震中附近的地质体本构关系曲线斜率变小趋近于零的具体表现。因此,地电阻率半日周期功率谱异常是大地震临震阶段的电学标志。

The power spectrum analysis of data observed at Changli earthresistivity station during 1973-1978 was carried out and found that the earthresistivity of this station successively occurred amplitude and frequency anomalies of semidiurnal period two months around the Tangshan strong earthquake M 7.8 on July 28, 1976, especially half a month immediately before the earthquake, its amplitude value exceed the observed error in normal times 5-20 folds and the monthly frequency anomaly of impulse immediately before the earthquake was 3-4 times higher than the usual background value. Analysis shows that the appearance of such semidiurnal power spectrum anomaly of earthresistivity is the concrete expression of the reduction and tendency to zero of the curve gradient of the eigen relation of the geologic body in the vicinity of the epicentre. So, the power spectrum anomaly of semidiurnal period of earthresistivity is the electricity mark in the impending stage of large earthquakes.