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用和达法处理了从1967年至1976年十年内发生在北京区域台网内的千余次地震,求得各次地震的 V_p/V_s.结果表明:(1)在上述时期内发生在台网内的13次 M_L≥3.5的地震前,在主震震中附近地区都有明显的 V_p/V_s 下降而后回升的现象;(2)主震的大小与 V_p/V_s 异常区的面积大致成对数线性关系,而异常持续时间与主震震级之间无明显关系;(3)异常结束后到主震发生之间存在一段“等待时间”,“等待时间”的长短与 V_p/V_s 异常的情况无明显关系.这似乎暗示了本区地震发震机制的复杂性,而且也使得用 V_p/V_s 异常预测发震时间存在困难.
A total of more than one thousand earthquakes occurred in the network of Beijing area from 1967 to 1976 were processed by Tathagata and Tathagata, and the V_p / V_s of each earthquakes was calculated. (1) During the above period, Before the 13 M_L≥3.5 earthquakes within the network, obvious V_p / V_s decreased and then recovered in the vicinity of the epicenter of the main earthquake; (2) The size of the main shock is approximately paired with the area of the V_p / V_s anomaly (3) there is a period of “waiting time”, “waiting time” and V_p / V_s anomaly after the abnormal end to the main shock This seems to imply the complexity of the seismogenic mechanism in this region and also makes it difficult to predict the seismogenic time using the Vp / Vs anomaly.