Numerical Test for the 2D Q Tomography Inversion Based on the Stochastic Ground-motion Model

추계학적 지진동모델에 기반한 2D Q 토모그래피 수치모델 역산

  • Yun, Kwan-Hee (Environmental & Structural Lab., Korea Electric Power Research Institute) ;
  • Suh, Jung-Hee (School of Civil, Urban & Geosystem Engineering, Seoul National University)
  • 연관희 (한전전력연구원 환경구조연구소) ;
  • 서정희 (서울대학교 지구환경시스템공학부)
  • Published : 2007.08.31

Abstract

To identify the detailed attenuation structure in the southern Korean Peninsula, a numerical test was conducted for the Q tomography inversion to be applied to the accumulated dataset until 2005. In particular, the stochastic pointsource ground-motion model (STGM model; Boore, 2003) was adopted for the 2D Q tomography inversion for direct application to simulating the strong ground-motion. Simultaneous inversion of the STGM model parameters with a regional single Q model was performed to evaluate the source and site effects which were necessary to generate an artificial dataset for the numerical test. The artificial dataset consists of simulated Fourier spectra that resemble the real data in the magnitude-distance-frequency-error distribution except replacement of the regional single Q model with a checkerboard type of high and low values of laterally varying Q models. The total number of Q blocks used for the checkerboard test was 75 (grid size of $35{\times}44km^2$ for Q blocks); Q functional form of $Q_0f^{\eta}$ ($Q_0$=100 or 500, 0.0 < ${\eta}$ < 1.0) was assigned to each Q block for the checkerboard test. The checkerboard test has been implemented in three steps. At the first step, the initial values of Q-values for 75 blocks were estimated. At the second step, the site amplification function was estimated by using the initial guess of A(f) which is the mean site amplification functions (Yun and Suh, 2007) for the site class. The last step is to invert the tomographic Q-values of 75 blocks based on the results of the first and second steps. As a result of the checkerboard test, it was demonstrated that Q-values could be robustly estimated by using the 2D Q tomography inversion method even in the presence of perturbed source and site effects from the true input model.

References

  1. 김성균, 김수경, 지헌철, 2002, 한반도 남부에서의 주파수별 가속 도 최대진폭의 감쇠, 지질학회지, 38, 237-250
  2. 연관희, 서정희, 2007, 지진동모델 파라미터 동시역산 결과를 이 용한 지진관측소 분류, 물리탐사지, 10(3), 183-190
  3. 연관희, Walter Silva, 박동희, 장천중, 2002, 수정된 Levenberg- Marquardt 역산방법에 의한 한반도 남부의 추계학적 지진 요 소 평가, 한국지진공학회 춘계학술발표회 논문집, 한국지진공 학회, 20-28
  4. Adams, D. A., and Abercrombie, R. E., 1998, Seismic attenuation above 10Hz in southern California from coda waves recorded in the Cajon pass borehole, Journal of Geophysical Research, 103, 24257-24270 https://doi.org/10.1029/98JB01757
  5. Aki, K., 1967, Scaling law of seismic spectrum, Journal of Geophysical Research, 72, 1217-1231 https://doi.org/10.1029/JZ072i004p01217
  6. Aki, K., and Richards, P. G., 2002, Quantitative seismology (2nd Edition), University Science Books
  7. Anderson, J. G., and Hough, S. E., 1984, A model for the shape of the fourier amplitude spectrum of acceleration at high frequencies, Bulletin of Seismological Society of America, 74, 1969-1993
  8. Boore, D. M., 2003, Simulation of ground motion using the stochastic method, Pure and Applied Geophysics, 160, 635-676 https://doi.org/10.1007/PL00012553
  9. Bowman, J. R., and Kennett, B. N. L., 1991, Propagation of Lg waves in the north Australian craton: Influence of crustal velocity gradients, Bulletin of the Seismological Society of America, 81, 592-610
  10. Brune, J. N., 1970, Tectonic stress and the spectra of seismic shear waves from earthquakes, Journal of Geophysical Research, 75, 4997-5009 https://doi.org/10.1029/JB075i026p04997
  11. Brune, J. N., 1971, Correction, Journal of Geophysical Research, 76, 5002 https://doi.org/10.1029/JB076i020p05002
  12. Hank, T. C., and Kanamori, H., 1979, A moment magnitude scale, Journal of Geophysical Research, 84, 2981-2987
  13. Kang, I. B., and McMechan, G. A., 1994, Separation of intrinsic and scattering Q based on frequency-dependent amplitude ratios of transmitted waves, Journal of Geophysical Research, 99, 23875-23885 https://doi.org/10.1029/94JB02472
  14. Kennett, B. L. N., 1986, Lg waves and structural boundaries, Bulletin of the Seismological Society of America, 76, 1133- 1141
  15. Kennett, B. L. N., 1989, Lg-wave propagation in heterogeneous media, Bulletin of the Seismological Society of America, 79, 860-872
  16. Marquardt, D. W., 1963, An algorithm for least-squares estimation of nonlinear parameters, Journal of the Society for Industrial and Applied Mathematics, 11, 431-441 https://doi.org/10.1137/0111030
  17. Matthew, D. P., and Anderson, J. G., 2003, A comprehensive study of the observed spectral decay in strong-motion accelerations recorded in Guerrero, Mexico, Bulletin of the Seismological Society of America, 93, 600-611 https://doi.org/10.1785/0120020065
  18. Papageorgiou, A. S., and Aki, K., 1983, A specific barrier model for the quantitative description of inhomogeneous faulting and the prediction of strong ground motion, Part II. Applications of the model, Bulletin of Seismological Society of America, 73, 953-978
  19. Press, W., Flannery, B., Teukolsky, S., and Vetterling, W., 1987, Numerical Recipes, Cambridge University Press, Cambridge, United Kingdom
  20. Sato, H., and Fehler, M. C., 1998, Seismic wave propagation and wcattering in the heterogeneous earth, Springer/AIP Press
  21. Shih, X. R., Chun, K. Y., and Zhu, T., 1994, Attenuation of 1-6s Lg waves in Eurasia, Journal of Geophysical Research, 99, 23859-23874 https://doi.org/10.1029/94JB02163
  22. Wu, R., 1985, Multiple scattering and energy transfer of seismic waves: separation of scattering effect from intrinsic attenuation, I. Theoretical modelling, Geophysical Journal of the Royal Astronomical Society, 82, 57-80 https://doi.org/10.1111/j.1365-246X.1985.tb05128.x