谢辉, 马禾青, 马小军, 张楠, 罗恒之, 李青梅. 2018: 基于谱元法数值模拟研究地震判定准则. 地震学报, 40(5): 609-619. DOI: 10.11939/jass.20170162
引用本文: 谢辉, 马禾青, 马小军, 张楠, 罗恒之, 李青梅. 2018: 基于谱元法数值模拟研究地震判定准则. 地震学报, 40(5): 609-619. DOI: 10.11939/jass.20170162
Xie Hui, Ma Heqing, Ma Xiaojun, Zhang Nan, Luo Hengzhi, Li Qingmei. 2018: Determination criteria of repeating earthquakes based on spectral element modeling. Acta Seismologica Sinica, 40(5): 609-619. DOI: 10.11939/jass.20170162
Citation: Xie Hui, Ma Heqing, Ma Xiaojun, Zhang Nan, Luo Hengzhi, Li Qingmei. 2018: Determination criteria of repeating earthquakes based on spectral element modeling. Acta Seismologica Sinica, 40(5): 609-619. DOI: 10.11939/jass.20170162

基于谱元法数值模拟研究地震判定准则

Determination criteria of repeating earthquakes based on spectral element modeling

  • 摘要: 本文以宁夏区域地震台网为例,分析了波形互相关法在判定重复地震中可能存在的问题并讨论了相应的处理方法,通过构建三维非均匀体模型并利用谱元法数值模拟地震波的传播,统计了不同台站观测到的地震对波形互相关系数的分布,进一步研究了互相关系数与非均匀体性质及震源机制解之间的关系。结果表明:针对宁夏区域地震台网,利用波形互相关法判定重复地震比地震定位方法更有效;互相关系数在不同台站的取值与震源附近三维非均匀体强度和直达波与尾波的振幅比有关,对于相同的震源间距,较弱震源、较弱非均匀体或者较强振幅的直达波均会导致波形互相关系数变高,因此应选取更高的互相关系数阀值来判定重复地震。宁夏区域地震台网平均台间距为30—50 km,通过选取直达波较弱的台站或只截取尾波窗口计算互相关系数并设定较高的阀值,利用波形互相关法可有效地判定ML1.0—3.0重复地震,进而为重复地震的监测与研究提供依据。

     

    Abstract: Taking Ningxia regional seismic network for an example, we discussed the problems or difficulties in detecting repeating earthquakes via the waveform cross-correlation method and provided the corresponding solutions. We first created statistical models of 3D volumetric heterogeneities and then incorporated them into spectral element method to simulate 3D seismic wave propagation, so investigate the spatial distribution of the cross-correlation coefficients between earthquake pairs observed by different seismic stations, we found strong impacts of the volumetric heterogeneities and focal mechanism solution on the cross-correlation coefficients. The results show that the waveform cross-correlation method is more reliable and therefore practically useful in identify repeating earthquakes than the earthquake relocation method for the Ningxia regional seismic network. The cross-correlation coefficients are affected by the intensity of 3D heterogeneities near the hypocenter and the amplitude ratio of direct waves to coda waves. Given the same distance between two earthquakes, the stronger heterogeneities near earthquake source or stronger amplitude direct waves will result in higher waveform correlation coefficients. Thus, a higher threshold of cross-correlation coefficient is needed to reliably detecting repeating earthquakes. In summary, based on the data of Ningxia regional seismic network with an average station spacing of 30−50 km, choosing a proper threshold value of cross-correlation coefficient by only taking the time window of coda waves or data with weak direct P-waves, waveform cross-correlation method could reliably identify repeating earthquakes with a magnitude range ofML1.0−3.0, thus providing basis for the surveillance of repeating earthquakes.

     

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