In the recent years,on the basis of earthquake prediction by means of geomagnetic method of characteristic,two methods and their indexes of prediction have been dealt with.They are the methods of the anomalous time of crossover of "27 days of slipping error for Z component and vector T".In the normal case,the average slipping error of 27 days of Z component and vactor T of geomagnetism ΔZ_i ang ΔT_i can skip irregularly.But in this region,before the middle and strong earthquakes,ΔZ_i>0.2 NT,positive anomaly is shown continuously;ΔT_i<-0.1,negative anomaly is shown.If the anomalous days of ΔZ_i and ΔT_i are Δt ≥ 14 days,the occurrence day of the middle and strong earthquakes in coming days,according to the anomalous time of crossover method,are t₀=nΔt±1day,in the monitoring region of this province.In the formula,n=1,2.
In the past two years of earthquake monitoring and prediction,the three methods,as are mentioned above,were used to make a good prediction both of Wuzhong earthquake of M=5.1 in 1984 and Tanchang earthquake of M=5.0 in 1985.So a comprehensive analysis of the three methods mentioned above can not only help decrease the pseudoprediction and improve the ability of judging anomalies and predicting earthquake but also can shorten the earthquake occurrence day,from month's predictionto day's.
K,the slope of geomagnetic characteristics is considered to reflect the physical process of the changes of underground medium structure and electrical conductivity.The average error of slipping of 27 days for Z component and vector T can eliminate the solar cycle impact and give a prominent plaee at depth.As for the method of crossover,there may exist some.rhyme to work together,which is still in the course of research.