青海东北部中强地震序列类型及特征研究

STUDY ON THE TYPES AND CHARACTERISTICS OF MODERATELY STRONG EARTHQUAKE SEQUEN- CES IN NORTHEASTERN QINGHA

1970～ 1999年青海东北部发生 MS≥ 5.0地震序列 2 2个。通过分析发现 ,主—余型地震序列9个 ,约占序列总数的 4 1% ;孤立型序列 8个 ,约占序列总数的 36% ;前—主—余型序列 3个 ,约占序列总数的 13% ;双震 (前—双主—余 )型序列 2个 ,约占序列总数的 10 %。这些序列分属 3个不同的地震带 ,地震的频度、强度及序列类型在各个地震带表现不一 ,各具特色。此外还分析了序列早期( 0 .5、1、2、3、4、5、7天 )及全序列的特征参数 b值、u值、h值、ρ值的变化过程 ,认为 b值和 u值的变化对该区地震序列类型的早期判断有一定参考价值。

sequences of M\-S≥5.0 earthquakes had occurred in the northeastern Qinghai in 1970～1999. After sorting out and studying them, we thought 9 of them belong to mainshock aftershock type, accounting for 41% of the total; 8 are isolated type, about 36% of the total; 3 are foreshock mainshock aftershock type, about 10% of the total. All these sequences distributed in three different seismic belts, and their frequency, intensity and type in each belt are different. We also studied such characteristic parameters as value b,u,h,ρ in early days of the sequence and in the whole sequence. We found value b and u had reference value to the early determination of earthquake sequence types.