Abstract
Based on the three component accelerograms, recorded at near-field distance by a temporary seismic network consisting of digital cassette tape recording accelerographs, the focal mechanisms of three aftershocks of the April 18, 1985, Luquan, Yunnan Province, China, earthquake ofM S=6.1, are calculated using seismic moment tensor inversion technique. The phases of direct P, S and converted SP waves in the displacement seismograms, produced by twice integrations 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 (M L=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 seismogenic 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 medium 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.
Similar content being viewed by others
References
Aki, K. and Patton, H., 1978. Determination of seismic moment tensor using surface waves.Tectonophysics,49, 213–222.
Barker, J. S. and Longston, C. A., 1982. Moment tensor inversion of complex earthquakes.Geophys. J. R. astr. Soc.,68, 777–803.
Cagniard, L., 1962.Reflection and Refraction of Progressive Seismic Waves. Translated and revised by Flinn, E. A. and Dix, C. H., McGraw-Hill, New York.
De Hoop, A. T., 1960. A modification of Cagniard’s method for solving seismic pulse problems.Appl. Sci. Res., B8, 349–356.
Dix, C. H., 1954. The method of Cagniard in seismic pulse problem.Geophysics,19, 722–738.
Doornbos, D. J., 1982. Seismic moment tensors and kinematic source parameters.Geophys. J. R. astr. Soc.,69, 235–251.
Fitch, T. J., McCowan, D. W. and Shields, M. W., 1980. Estimation of the seismic moment tensor from teleseismic body wave data with applications to intraplate and mantle earthquakes.J. Geophys. Res.,85, 3817–3828.
Gilbert, F. and Dziewonski, A. M., 1975. An application of normal mode theory to the retrieval of structural parameters and source mechanisms from seismic spectra.Phil. Trans, Roy. Soc. London,A278, 187–269.
Johnson, J. R., 1974. Green’s function for Lamb’s problem.Geophys. J. R. astr. Soc.,37, 99–131.
Kanamori, H. and Given, J. W., 1981. Use of long-period surface waves for rapid determination of earthquake source parameters.Phys. Earth Planet. Int.,27, 8–31.
Lamb, H., 1904. On the propagation of tremors over the surface of an elastic solid.Phil. Trans. Roy. Soc., London,A203, 1–42.
Lanczos, C., 1961.Linear Differential Operators. Van Nostrand, London, 564pp.
Lay, T., Given, J. W. and Kanamori, H., 1982. Long-period mechanism of the 8 November 1980 Eureka, California, earthquake.Bull. Seism. Soc. Amer.,72, 439–456.
Longston, C. A., 1981. Source inversion of seismic waveforms: the Koyna, India, earthquakes of 13 September 1967.Bull. Seism. Soc. Amer.,71, 1–24.
Mendiguren, J. A., 1977. Inversion of surface wave data in source mechanism studies.J. Geophys. Res.,82, 889–894.
McCowan, D. W., 1976. Moment tensor representation of surface wave sources.Geophys. J. R. astr. Soc.,44, 595–599.
Romanowicz, B., 1982. Moment tensor inversion of long-period Rayleigh waves: A new approach.J. Geophys. Res.,87, 5395–5407.
Stump, B. W. and Johnson, L. R., 1977. The determination of source properties by the linear inversion of seismograms.Bull. Seism. Soc. Amer.,67, 1489–1502.
Stump, B. W. and Johnson, L. R., 1984. Near-field source characterization of contained nuclear explosion in tuff.Bull. Seism. Soc. Amer.,74, 1–26.
Wu, M. X., Wang, M., Sun, C. C., Ke, Z. M., Wang, P. D., Chen, Y. T. and Wu, F. T., 1991. Accurate hypocenter determination of aftershocks of the 1985 Luquan earthquake.Acta Seismologica Sinica. 4, 181–191.
Author information
Authors and Affiliations
Additional information
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 412–419, 1991.
This work is supported by the Chinese Joint Seismological Sciences Foundation and the Western Yunnan Earthquake Prediction Test Site (WYEPTS), State Seismological Bureau.
About this article
Cite this article
Ni, J., Chen, Y., Wang, M. et al. Moment tensor inversion of some aftershocks of the April 18, 1985 Luquan earthquake of Yunnan Province, China. Acta Seismologica Sinica 5, 459–467 (1992). https://doi.org/10.1007/BF02650541
Issue Date:
DOI: https://doi.org/10.1007/BF02650541