倪江川1, 陈运泰1, 王鸣1, 吴明熙1, 周家玉1, 王培德1, 吴大铭2. 1991: 云南禄劝地震部分余震的矩张量反演. 地震学报, 13(4): 412-419.
引用本文: 倪江川1, 陈运泰1, 王鸣1, 吴明熙1, 周家玉1, 王培德1, 吴大铭2. 1991: 云南禄劝地震部分余震的矩张量反演. 地震学报, 13(4): 412-419.
Jiangchuan Niup, Yuntai Chenup, Ming Wangup, Mingxi Wuup, Jiayu Zhouup, Peide Wangup, Francis T. Wuup2styledi. 1991: MOMENT TENSOR INVERSION OF SOME AFTERSHOCKS OF THE APRIL 18, 1985, LUQUAN, YUNNAN, CHINA, EARTHQUAKE. Acta Seismologica Sinica, 13(4): 412-419.
Citation: Jiangchuan Niup, Yuntai Chenup, Ming Wangup, Mingxi Wuup, Jiayu Zhouup, Peide Wangup, Francis T. Wuup2styledi. 1991: MOMENT TENSOR INVERSION OF SOME AFTERSHOCKS OF THE APRIL 18, 1985, LUQUAN, YUNNAN, CHINA, EARTHQUAKE. Acta Seismologica Sinica, 13(4): 412-419.

MOMENT TENSOR INVERSION OF SOME AFTERSHOCKS OF THE APRIL 18, 1985, LUQUAN, YUNNAN, CHINA, EARTHQUAKE

  • 摘要: 利用数字盒式磁带记录加速度仪组成的流动地震台网所记录的三分向近场加速度图,通过矩张量反演确定了1985年4月18日云南禄劝 Ms=6.1地震的部分余震的震源机制.以均匀半无限弹性介质的格林函数解释路径效应,并通过正演计算识别由两次积分得到的位移地震图中的直达 P 波、直达 S 波和 SP 转换波震相,然后用这些震相进行矩张量反演.反演结果表明,在解超定线性方程组时,采用适当的加权系数,可使上述直达波和转换波的理论计算值与观测值拟合得较好.尽管用以反演的三个余震大小不同(震级 ML48,3.2,3.5),震源位置也有差别,但它们的震源机制却非常接近,且与主震的震源机制相当一致.这一特征显示了余震的发生与主震发震构造的内在联系.这些实例说明,由震源球球面上分布适宜的数字地震台网取得的近场加速度资料,借助于即使是简单的介质模型,通过地震矩张量反演,不但可以得出这些地震震源的主要成份————剪切位错源,同时还可得出震源所含的其它成分,如膨胀源和补偿线性向量偶极.

     

    Abstract: Based on the three-component accelerograms, recorded at near-field distance by a temporary seismic network consisting of digital cassette tape reacording accelerographs, the focal mechanisms of three aftershocks of the April 18, 1985, Luquan, Yunnan Province, China, earthquake of magnitude Ms=6.1, are calculated using moment tensor inversion technique. The phases of direct P, S and converted SP waves in the displacement seismograms, produced by twice integration of the observed accelerograms, are identified via forward calculation using Green's functions for homogeneous semi-infinite elastic medium, and used in the inversion. The results of inversion show that a better fit of synthetic to the observed seismograms of direct as well as converted phases can be achieved if appropriate weighting functions are used in solving the over-definite linear equations. While these aftershocks are of different magnitudes (ML=4.8, 3.2 and 3.5, respectively) and hypocentral locations, their focal mechanisms are very similar and consistent with that of the main shock. This feature demonstrates the intrinsic correlation between the occurrence of aftershocks and the seismogeneic fault of main shock. Our experimentations show that using the near-field accelerogram obtained from the digital seismic network with appropriate azimuthal coverage on the focal sphere, with the aid of even simple earth model, not only the shear dislocation source, but also the isotropic part and CLVD (compensated linear vector dipole) can be retrieved by the technique of moment tensor inversion.

     

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