2001年施甸M_S5.9地震序列的震源参数研究  

A STUDY ON THE FOCAL PARAMETERS OF SHIDIAN M_S=5.9 EARTHQUAKE SEQUENCES IN 2001

作　　者：秦嘉政[1] 钱晓东[1] 叶建庆[1] 

机构地区：[1]云南省地震局,中国昆明650224

出　　处：《地震学报》2005年第3期250-259,共10页Acta Seismologica Sinica

基　　金：云南省科技攻关项目<云南强震中短期预测研究>(2001NG46);<西南地区数字地震资料在短临预测中的应用方法研究>(2001BA601B010201)资助.

摘　　要：以昆明数字地震台网对2001年4月12日施甸MS5.9地震序列观测的近300次地震事件的波形数据资料为基础,用横波波谱资料估算了该次地震序列的震源参数.结果表明,震级在1.5～5.3的范围内,地震矩范围为1010～1016N·m,拐角频率的范围为0.2～8.0Hz,震源破裂半径a的范围为200～2500m,地震应力降的范围为0.1×105～20×105Pa.通过对地震震源拐角频率fc及地震应力降Δσ随时间变化的统计分析,本文研究结果发现,施甸5.9级主震前的前震序列地震的平均拐角频率明显低于主震后余震序列的平均拐角频率.与之相反,地震平均应力降Δσ则是前震序列明显高于余震序列.分析认为,主震前后平均拐角频率和应力降的这种随时间变化特征,具有强震前的前兆信息指示意义.主震的前震序列具有高应力降显示出主震区储存了较高的剪应力;主震后,由于释放了绝大部分应力,余震序列则表现为低应力破裂过程.On the basis of about 300 earthquake wave forms observed in the Shidian M_S=5.9 sequences on April 12, 2001 recorded in Kunming Digital Seismic Network, the spectra of shear wave have been used to estimate the focal parameters of these earthquake sequences. The results show that within the magnitude range of 1.5~5.3, the seismic moments are 10 10~10 16 N·m, the corner frequencies are 0.2~0.8 Hz, radii of the focal rupture are 200~2 500 m and the stress drops are 0.1×105~20×105 Pa. Through the statistical analyses of variation of corner frequency f_c and stress drop Δσ with time, it is discovered that the average corner frequency of the foreshock sequences is obviously lower than that of the aftershock sequences. Contrary, the average stress drops Δσ of the foreshock sequences are clearly higher than that of the aftershocks. It is considered that these variation characteristics of average corner frequency and stress drops before and after the main shock have index significance to the precursory information before a strong earthquake. The higher stress drops for the foreshock sequences show that the higher shear stresses have been stored in the area of main shock. After the main shock, most of the stresses have been released, so the aftershock sequences show a rupture process of lower stresses.

关 键 词：数字地震观测 震源参数 地震序列 云南地区 

分 类 号：P315.33[天文地球—地震学]