摘要
分析了广东及其邻近地区1999至2004年9月间86个ML≥2.0级地震的应力降值,结果表明,应力降随震级的增大而出现不同尺度的变化,lg△σ的分布大致分为两个阶段:①ML≤4.0级地震,随着震级增大,lg△σ呈增大的趋势;②ML≥4.0级地震,lg△σ不随震级的增大而增大,稳定在一范围内。统计结果表明,本区ML2.0～2.9级地震应力降平均值为4.5bar,ML3.0～3.9级地为7.6 bar,ML4.0～4.9级地震为10.7 bar。2004年阳江ML5.2级地震前1年左右,曾发生多次应力降高于阳江地区平均值的地震事件,而在临震前几个月应力降总体水平则是偏低的,这一特征在其他地区的中强地震前亦曾出现。应力降平面等值线分布图显示北部湾地区是广东及其邻区应力降背景最高的地区。
In this paper, we analyzed the 86 stress drop values of the moderate and small earthquakes （ML≥2.0） occurred between 1999 and Sep., 2004 in Guangdong and its adjacent areas. It shows that the stress drop changes in different extent when the earthquake magnitude increases and the lg△σ-ML relation chart could be marked off to two phases. 1.For the earthquakes with ML≤4.0, lg△σ increases when the magnitude rises; 2. For the earthquakes with ML≥4.0, lg△σ does not increase but is in some scale when the magnitude rises. It also shows that the mean value of seismic stress drop for ML2.0-2.9 earthquakes in Guangdong and its adjacent areas is 4.5 bar, the one for ML3.0-3.9 is 7.6 bar, the one for ML4.0-4.9 is 10.7 bar. The plane isogram of seismic stress drop shows that the region with the maximum background value in Guangdong and its adjacent areas is the Beibuwan bay.
出处
《华南地震》
2007年第3期79-86,共8页
South China Journal of Seismology
关键词
应力降
中小地震
广东及其邻近区域
Stress drop, Moderate and small earthquakes, Guangdong and its adjacent areas
