芦山余震震源参数及震源区品质因子反演

Estimation of source parameters and quality factor based on generalized inversion method in Lushan earthquake

摘要:

为了确定2013年4月20日芦山地震部分余震的震源参数及传播路径对地震波的衰减特性,选取30次余震中15个强震台站获取的179组加速度记录,选择其中一次余震作为参考事件,基于广义反演方法计算了芦山余震的位移震源谱及品质因子,采用网格搜索方法确定余震震源参数,进一步确定了震源参数的定标关系．结果表明:芦山地震平均应力降略低于汶川余震平均应力降,震级与应力降没有明显相关性,视应力与应力降正相关;该研究区域0.5～20 Hz频段品质因子为Q(f)=31.867f1.037 5,地震波衰减速度较快．

Abstract:

A large number of strong ground motion recordings have been collected by the National Strong-Motion Observation Network System of China in the Lushan earthquake sequences after April 0,4. In order to estimate the source parameters of the Lushan aftershocks and the attenuation characteristic of the seismic waves, this study selected 179 acceleration recordings obtained from 15 strong motion stations in 30 aftershocks to estimate the displacement source spectrum and quality factor, based on the generalized inversion technique of the S-wave Fourier amplitude spectrum with one aftershock as the reference event. Various source parameters are estimated by using grid searching technique for each event on the basis of displacement source spectra. It is shown that the average stress drop is slightly lower in Lushan earthquake than that in Wenchuan earthquake. Stress drop is significantly independent on the magnitude, while the apparent stress and the stress drop have favorable positive correlation. The frequency-dependent quality factor Q(f) in this region is found to be 31.867f1.037 5 with the frequency ranging from 0.5 to 20 Hz, the seismic wave attenuates quite faster in Lushan region.