用基于构造应力场资料的加卸载响应比方法 ,通过应力场参数、最少样本量等多种参数的分区全时空扫描对比 ,全面总结了大华北地区 1 970～ 1 999年 5级以上地震前的中期和短期时间演化特征 :在最少样本为 1 5时 ,震前 2年左右在震中附近出现 Y3 ≥ 2的高值异常区 ,于震前 1年收缩、甚至消失 ,并常常在震前 6个月左右时在震中处出现小范围的高值异常。预报效能 R评分为 0 .3～ 0 .5,P评分为 0 .4～ 0 .6。研究结果还显示 ,4级左右的中等地震前也存在 Y3 的高值异常 Based on the comparison of full-space and time-space scanning of multiple parameters such as stress field parameters and minimum sample size, the loading / unloading response ratio method based on the tectonic stress field data is used to comprehensively summarize the data before the earthquakes of magnitude 5 above 1,970-7,999 in the North China area Mid- and short-term evolution characteristics: At a minimum sample of 15, a high-value anomalous zone of Y3 ≥ 2 occurred near the epicenter about 2 years before the earthquake and contracted or even disappeared 1 year before the earthquake, and often 6 A small range of high-value anomalies appeared at the epicenter in the middle of the month. Prediction efficacy R score was 0 .3 ~ 0 .5, P score was 0 .4 ~ 0 .6. The results also show that there is also a high Y3 anomaly before the moderate earthquakes of about grade 4