华东地区近期强震前地电阻率的前兆信息

讨论了自1976年唐山地震后,在华东地区地电阻观测台网范围内发生6级强震前ρ_s异常的时空分布特征。对观测值ρ_s的异常变化与地震活动性、岩石体积应变以及应力降等的关系作了对比。指出它们之间在空间上存在有一致性,且在时间上有同步性。研究结果表明:中强地震前,ρ_s的异常变化与地震活动性有关。这说明在某种程度上,ρ_s异常可视为异常信息。ρ_s异常持续时间较短,幅度较小,异常数目也相对较少,空间分布呈散射状,且异常形态的叠加小于唐山大震前的ρ_s异常叠加值。表明使用ρ_s观测方法预测中强地震比预测强震要困难得多,因此目前最根本的是要提高观测台网的监测能力,增大台网的密度,并通过深入研究震源区周围异常特征、改善观测台站条件来完善地震预报研究。

STUDY ON PRECURSORY INFORMATION OF EARTH RESISTIVITY BEFORE MODERATE EARTHQUAKES OCCURRED RECENTLY IN THE EAST OF CHINA

This paper discusses some space-time characteristics of p, anomalies before moderate earthquakes MQ which have occurred within the controlling range of earth resistivity network in the east of China after 1976 Tangshan earthquake.The paper makes some comparisons between anomalous variations of observation data p, and seismicity, rock volume strain as well as stress drop in the corresponding regions.It points out that there are coincidence in space and synchronization at time among these parameters. The results show that some p, anomalous variations are related to seismicity before moderate earthquake and indicate that there probably are precursory information at a certain degree. The duration time of the p, anomalies is shorter, the amplitude is smaller, the anomaly number is relatively less, the space distribution is scattering as well as the coincidence of anomaly pattern is inferior than that of p, precursor of the Tangshan great earthquake. It indicates that there are more difficulties in predicting the moderate earthquake than the strong one by using p, method. It is essential to raise monitoring capacity of network and accumulate more examples of moderate earthquake by a dense network with proper station site and improve observation conditions for studying deeply anomaly characteristics near and far from the source regions.