滇西南地震活动特征分析

ANALYSIS OF SEISMIC CHARACTERISTICS IN SOUTHWEST OF YUNNAN

对滇西南1970年以来所有M≥4.6级地震前的空间活动图像进行研究,用地震频度作为参数描述地震前区域的地震活动增强与平静现象,用空区、条带描述地震的孕震过程,得到以下认识：①地震频度增加是滇西南地区5级以上地震前的共性特征;②滇西南地区M≥4.6级地震前出现空区的比例随着地震震级的增加而有所增加,4.6-4.9级地震前只有60%的地震出现空区,5.0-5.9级地震前有90.9%的地震出现空区,而6.0级以上地震前全部出现空区;③空区平均持续时间也随着震级的加大而增加,空区平均持续时间为13.58个月,最短为3个月,最长为37个月;④主震位置（27/33）多发生在空区边缘（含长轴端12次、短轴端8次）。震前出现条带的规律则不明显。

The spatial patterns of M≥4.6 earthquakes in southwest of Yunnan province since 1970 are studied by using the earthquake frequency parameters to describe the increase and quiet phenomena before earthquakes in the region,and using gaps and belts to describe the process of earthquakes,then got the following results：①The increase in frequency is the common characteristics before M≥5 earthquakes in southwest of Yunnan province;②The gap ratio increases with the earthquake magnitude,and the gap ratio is 60% of 4.6~ 4.9 earthquakes,90.9% of 5.0 ~ 5.9 earthquakes,100% of 6.0 -6.9 and 7.0- 7.9 earthquakes;③The average duration of gaps is also increased with the magnitude,which is 13.58 months,the minimum is 3 months,the maximum is 37 months;④The main shocks＇ locations（27/33） occurred within the edge of gaps（including the long axis side 12 times,short axis side 8 times）.Belts before earthquakes are not significant.