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本文在近几年用地磁特征线法预报地震的基础上进而探讨了地磁“Z分量和向量T的27日滑动差”异常时间跨越式预报地震的两种方法及相应的预报指标。在一般情况下,地磁Z分量和向量T的27日滑动差△Z与△T在基线值附近无规则地跳动。但在南北地震带的南坪至吴忠地段的中强地震前,兰州地磁台的△Z与△T出现异常,其异常幅度分别为,△Z>0.2NT;△T<=0.1。异常时间△t≥14天。据此可按异常时间跨越式法预测未来4.5级以上地震的发震日期;t=n×△t±1天,(n=1,2)。在近两年地震监视预报中应用上述方法的预报指标对1984年灵武5.2级地震和1985年宕昌5.0级地震作了较好的短临预报。
Based on the prediction of the earthquakes using the geomagnetic characteristic line method in recent years, the paper discusses two methods of earthquake prediction of the terrestrial time-lapse by using the 27-day slip difference between the Z component and the vector T and corresponding forecasting indicators. In general, the 27-day slip differences ΔZ and ΔT of the geomagnetic Z component and the vector T irregularly beat around the baseline value. However, before the moderate-strong earthquakes from Nanping to Wuzhong in the North-South Seismic Belt, the anomaly of △ Z and △ T of Lanzhou geomagnetic observatory were abnormal. The abnormal amplitudes were △ Z> 0.2NT and △ T <= 0.1 respectively. Abnormal time △ t ≥ 14 days. According to this, the onset time of earthquakes with a magnitude 4.5 or above can be predicted by the leap-over method for anomalous time; t = n × Δt ± 1 day, (n = 1,2). In the past two years, the forecast indicators of the above methods are used to make a relatively short-term forecast of the 1984 Lingwu 5.2 earthquake and the 1985 Dangchang M 5.0 earthquake.