解孟雨, 史保平. 2018: 对汶川地震余震序列中最大余震事件的讨论. 地震学报, 40(3): 304-315. DOI: 10.11939/jass.20170209
引用本文: 解孟雨, 史保平. 2018: 对汶川地震余震序列中最大余震事件的讨论. 地震学报, 40(3): 304-315. DOI: 10.11939/jass.20170209
Xie Mengyu, Shi Baoping. 2018: Discussion on the largest aftershock of the Wenchuan aftershock sequence. Acta Seismologica Sinica, 40(3): 304-315. DOI: 10.11939/jass.20170209
Citation: Xie Mengyu, Shi Baoping. 2018: Discussion on the largest aftershock of the Wenchuan aftershock sequence. Acta Seismologica Sinica, 40(3): 304-315. DOI: 10.11939/jass.20170209

对汶川地震余震序列中最大余震事件的讨论

Discussion on the largest aftershock of the Wenchuan aftershock sequence

  • 摘要: 本文针对2008年5月12日四川汶川MW7.9地震后的余震目录,采用2004年Shcherbakov和Turcotte提出的最大余震震级推断法,给出了最大余震震级的估计值。结果表明,采用现有的余震数据,在大震级区间可能存在一定数量的余震缺失,这造成了余震数据与Gutenberg-Richter定律曲线在大震级区间的差异,导致推断的最大余震震级与使用目录中的最大余震震级存在明显差异。利用震级与断层长度或地表破裂长度之间的经验关系可以看出,由灌县—江油断裂的破裂尺度得到的震级与推断最大余震震级基本一致。根据前人给出的断层摩擦失稳时间模型和Brune近断层质点运动模型,本文进一步探讨了汶川地震北川—映秀断裂对灌县—江油断裂的触发作用,认为北川—映秀断裂破裂所辐射出的S波可以在短时间内使得灌县—江油断裂发生失稳,进而产生宏观破裂并形成地震,因此由灌县—江油断裂破裂形成的地震可能为汶川地震的最大余震。

     

    Abstract: The 2008 MW7.9 Wenchuan earthquake occurred in Wenchuan, Sichuan Province caused heavy casualties and great economic losses. Using the method proposed by Shcherbakov and Turcotte, we estimate the magnitude of the largest aftershock following the Wenchuan mainshock. The results show that, when aftershock’s magnitude becomes much large, the corresponding aftershocks in the current aftershock catalogue we have used may be missed, which causes the phenomenon that the catalogue deviates from the prediction calculated by the Gutenberg-Richter relationship, and this deviation also causes the big difference between the recorded largest aftershock and inferred largest aftershock. However, using the empirical relationships between the magnitude and surface rupture length or rupture area, we find that the sub-event caused by the Guanxian-Jiangyou fault has a similar magnitude with the inferred largest aftershock. Moreover, based on the model which describes the instability time of fault frictional slip and the Brune’s source model, we demonstrate that the shear seismic wave generated by the earthquake rupture on the Beichuan-Yingxiu fault could trigger the rupture on the Guanxian-Jiangyou fault at a very short time, which finally could lead to an earthquake. Therefore, the triggered event could be considered as one of the largest aftershocks and also be involved in the aftershock’s catalogue.

     

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