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通过对1982年4月14日海原5.5级地震的研究表明: 1.地震前ρs趋势异常以下降为主,临震异常则有升有降,表现了幅度大、速率快的特点。ρs在地震前后的演化过程是:下降—转平—临震突跳—(发震)—震后回升。2.地震前ρs的趋势异常有大面积长时间的特征。此外各台最大异常量的方向与当地大断裂(或发震断裂)的展布方向一致。这些特点说明,ρs趋势异常是整个区域应力场急剧增强的反映。3.各台ρs的异常幅度与台址第四纪复盖层关系密切。复盖层越厚其异常量越小。因此预报中强地震对地电台址的要求要更严格一些。
Through the study of the Haiyuan MS 5.5 earthquake on April 14, 1982, it shows that: 1. The anomalous trend of ρs before earthquakes mainly decreases, while the anomalous earthquakes rise or fall, showing the characteristics of large amplitude and fast rate. The evolution of ρs before and after the earthquake is: Decline - Leveling - Seismic sudden jump - (Seismogenic) - Rebound after the earthquake. 2. The tendency of ρs before the earthquake is abnormal. It has the characteristics of large area and long time. In addition, the direction of the maximum anomaly of each station is consistent with the distribution direction of the major faults (or seismogenic faults) in the area. These characteristics show that the ρs trend anomaly is a sharp reflection of the region’s stress field. The anomalous magnitude of each ρs is closely related to Quaternary overburden. The thicker the cover is, the smaller the anomaly is. Therefore, it is necessary to forecast that the requirements of the moderate earthquakes should be more strict on the location of the geo-station.