Skip to main content

Extended time-term method for identifying lateral structural variations from seismic refraction data

Abstract

A time-term method is a simple travel time inversion for seismic refraction crustal studies. Although this method is based on simple travel time calculation, it is robust in determining a basement velocity under the complicated surface structure. In the present paper, this method is extended to detect lateral velocity variation in the crystalline crust. We consider a model where a basement is composed of segments with a different velocity. Defining a likelihood function for unknown time-terms and refractor velocities, their best estimates are obtained by minimizing Akaike’s Bayesian Information Criterion (ABIC). To realize accurate velocity estimation, we also incorporate an effect of vertical velocity gradient within the refractor, which was ignored in the conventional algorithms. Numerical tests undertaken for realistic crustal structures show that our method successfully detects lateral velocity variation in a basement even for a case with undulated surface layers. It is particularly stable and reliable if the surface layers are not thick and their velocities are more than 30—40% smaller than the refractor velocities. Then, the refractor velocities are almost decoupled to the time-terms in the process of inversion. The incorporation of the effect of the velocity gradient is inevitably important when travel time data at far distances are included in the inversion.

References

  • Akaike, H., Likelihood and the Bayes procedure, in Bayesian Statistics, edited by J. M. Bernard, M. H. Degroot, D. V. Lindley, and A. F. M. Smith, pp. 143–166, University Press, Valencia, Spain, 1980.

    Google Scholar 

  • Berry, M. J. and G. F. West, An interpretation of the first arrival data of the Lake Superior experiment by the time-term method, Bull. Seism. Soc. Am., 56, 141–171, 1966.

    Google Scholar 

  • Červeny, V, I. A. Moltkov, and I. Psencik, Ray Method in Seismology, 214 pp., Univerzita, Karlova, Prague, 1977.

    Google Scholar 

  • Hearn, T. M. and R. W. Clayton, Lateral velocity variations in southern California. I., Results for the upper crust from Pg waves, Bull. Seism. Soc. Am., 76, 495–509, 1986.

    Google Scholar 

  • Iwasaki, T., Ray-tracing program for study of velocity structure by ocean bottomseismographic profiling, J. Seismol. Soc. Jpn., 41, 263–266, 1989 (in Japanese).

    Google Scholar 

  • Iwasaki, T., T. Yoshii, T. Moriya, A. Kobayashi, M. Nishiwaki, T. Tsutsui, A. Ikami, and T. Masuda, Precise P and S wave velocity structure in the Kitakami massif, northern Honshu, Japan, from a seismic refraction experiment, J. Geophys. Res., 99, 22187–22204, 1994.

    Article  Google Scholar 

  • Iwasaki, T., O. Ozel, T. Moriya, S. Sakai, S. Suzuki, G. Aoki, T. Maeda, and T. Iidaka, Lateral structural variation across a collision zone in central Hokkaido, Japan, as revealed by wide-angle seismic experiment, Geophys. J. Int., 132, 435–457, 1998.

    Article  Google Scholar 

  • Iwasaki, T., W. Kato, T. Umino, T. Okada, S. Sekine, T. Takeda, A. Hasemi, T. Matsushima, T., Mizogami, K. Miyashita, H. Miyamachi, and T. Moriya, Crustal structure across Northern Honshu arc revealed from wide-angle seismic reflection survey, Chikyu Monthly, 27, 48–55, 1999 (in Japanese).

    Google Scholar 

  • Koketsu, K. and S. Higashi, Three-dimensional topography of the sediment/basement interface in the Tokyo metropolitan area, central Japan, Bull. Seism. Soc. Am., 82, 2328–2349, 1992.

    Google Scholar 

  • Meru, R. F., An iterative method for solving the time-term equations, J. S. Steinhart and T. J. Smith, Ed., Geophys. Monogr., 10, pp. 495–497, Am. Geophys. Union, 1966.

  • Pavlis, G. L., Geotomography using refraction fan shots, J. Geophys. Res., 91, 6522–6543, 1986.

    Article  Google Scholar 

  • Scheidegger, A. and P. L. Willmore, The use of a least square method for the interpretation of data from seismic surveys, Geophysics, 22, 9–22, 1957.

    Article  Google Scholar 

  • Smith, T. J., J. S. Steinhart, and L. J. Aldrich, Lake Superior crustal structure, J. Geophys. Res., 71, 1141–1172, 1966.

    Article  Google Scholar 

  • Willmore, P. L. and A. M. Bancroft, The time-term method approach to refraction seismology, Geophys. J., 3, 419–432, 1960.

    Article  Google Scholar 

  • Yabuki, T. and M. Matsu’ura, Geodetic data inversion using a Bayesian Information Criterion for spatial distribution of fault slip, Geophys. J. Int., 109, 363–375, 1992.

    Article  Google Scholar 

  • Yoshii, T., Crustal structure of the Japanese Islands revealed by explosion seismic observations, Zisin, 46, 479–491, 1994 (in Japanese with English abstract).

    Google Scholar 

  • Yoshii, T. and S. Asano, Time-term analysis of explosion seismic data, J. Phys. Earth, 20, 47–57, 1972.

    Article  Google Scholar 

  • Zhao, D., A. Hasegawa, and S. Horiuchi, Tomographic imaging of P and S wave velocity structure beneath Northern Japan, J. Geophys. Res., 97, 19909–19928, 1992.

    Article  Google Scholar 

  • Zhao, L. S., Lateral variations and azimuthal anisotropy of Pn beneath the Basin and Range province, J. Geophys. Res., 98, 22109–22122, 1993.

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Takaya Iwasaki.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Iwasaki, T. Extended time-term method for identifying lateral structural variations from seismic refraction data. Earth Planet Sp 54, 663–677 (2002). https://doi.org/10.1186/BF03351718

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1186/BF03351718

Keywords