지구물리와물리탐사 (Geophysics and Geophysical Exploration)

  • 제15권1호
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  • Pages.1-7
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  • 2012
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  • 1229-1064(pISSN)
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  • 2384-051X(eISSN)
한국지구물리·물리탐사학회 (Korean Society of Earth and Exploration Geophysicists)
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춘천지역의 천부 횡파속도를 구하기 위한 레일리파 분산곡선 역산

Inversion of Rayleigh-wave Dispersion Curves for Near-surface Shear-wave Velocities in Chuncheon Area

  • 투고 : 2011.09.27
  • 심사 : 2011.12.02
  • 발행 : 2012.02.29
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초록

천부 횡파속도(${\nu}_s$)를 구하기 위한 효율적 방법을 모색하기 위하여, 수동적 및 능동적 방법으로 발생된 레일리파의 분산곡선 특성을 분석하였다. 춘천지역에서 반경 5 ~ 40 m인 4개 삼각형 배열을 이용하여 5분간 감지한 상시미동을 확장된 공간자기상관법으로 분석하였다. 동일한 지역에서 해머로 발생시키고 4.5 Hz 지오폰 24개로 2초간 기록한 인공적 레일리파는 다중채널 표면파 분석법으로 처리하였다. 7 ~ 19 Hz와 11 ~ 50 Hz 구간에서 상대적으로 높은 신호/잡음비를 보이는 상시미동과 인공적 레일리파의 분산곡선을 병합하고 역산한 결과를 시추공 주상도와 비교하였다. 토사층 및 연암층의 ${\nu}_s$는 각각 221 m/s와 846 m/s 정도로 비교적 일정하나, 사력-혼전층 및 풍화암층 구간에서는 깊이에 따라 선형으로 증가하는 양상을 보인다. 횡파속도에 의한 지반분류를 적용할 경우, 풍화암/연암의 경계는 시추주상도에 표시된 깊이보다 5 m 깊은 것으로 분석된다.

To evaluate methods of determining near-surface shear-wave velocities (${\nu}_s$), we derived dispersion curves of Rayleigh waves generated by both passive and active sources in Chuncheon, Korea. Microtremors were recorded for 5 minutes in each of four triangular arrays with radii of 5 ~ 40 m. Those data were analyzed using the Spatial Autocorrelation method. Rayleigh waves were also generated by a hammer source and recorded in the same area for 2 s using 24 4.5-Hz geophones. Multichannel Analysis of Surface Waves was applied to those data. Velocity spectra were derived with relatively high signal-to-noise ratios in the frequency ranges of 7 ~ 19 and 11 ~ 50 Hz for the microtremors and synthetically generated Rayleigh waves, respectively. The resultant dispersion curves were combined as one and then input to inversion to derive shear wave velocities that were compared with a lithology log from a nearby well. Shearwave velocities in the top soil and soft-rock layers are almost constant with values of 221 and 846 m/s, respectively; while the inverse-modeled ${\nu}_s$ increases linearly in the gravelly sand, cobbles, and weathered-rock layers. If rock type is classified based on shear-wave velocity, the inversion-derived boundary between weathered-rock and soft rock may be about 5 m deeper than in the well log.

키워드

참고문헌

  1. 건설교통부, 2004, 지하공동구 내진설계기준, 49p.
  2. Aki, K., 1957, Space and time spectra of stationary stochastic waves, with special reference to microtremors, Bull. Earthq. Res. Inst., 35, 415-456.
  3. Arai, H. and Tokimatsu, K., 2004, S-wave velocity profiling by inversion of microtremor H/V spectrum, Bull. Seism. Soc. Amer., 94(1), 53-63. https://doi.org/10.1785/0120030028
  4. Asten, M. W. and Henstridge, J. D., 1984, Array estimator and the use of microseisms for reconnaissance of sedimentary basin, Geophysics, 49(11), 1828-1837. https://doi.org/10.1190/1.1441596
  5. Butler, D. K., 2005, What is near-surface geophysics? In: D.K. Butler (Ed.), Nera-surface Geophysics, Investigation in Geophysics, No 13., Society of Exploration Geophysicists, Tulsa, 1-6.
  6. Capon, J., 1969, High-resolution frequency-wavenumber spectrum analysis: Proc. IEEE, 57, 1408-1418. https://doi.org/10.1109/PROC.1969.7278
  7. Eurocode 8, 2003, Design of structures for earthquake resistance. Part 1: General rules, seismic actions and rules for buildings. European Committe for Standardization.
  8. Haskell, N. A., 1953, The dispersion of surface waves in multilayered media, Bulletin of the Seismological Society of America, 43, 17-34.
  9. Kitsunezaki, C., Goto, N., Kobayashi, Y., Ikawa, T., Horike, M., Saito, T., Kurota, T., Yamane, K., and Okuzumi, K., 1990, Estimation of P- and S-wave velocities in deep soil deposits for evaluating vibrations in earthquakes, SINEN-SAIGAIKAGAKU, 9-3, 1-17.
  10. Lee, V. W. and Trifunac, M. D., 2010, Should average shearwave velocity in the top 30 m of soil be used to describe seismic amplification?, Soil Dynamics and Earthquake Engineering, 30(11), 1250-1258. https://doi.org/10.1016/j.soildyn.2010.05.007
  11. Ludwig, W. J., Nafe, J. E., and Drake, C. L., 1970, Seismic refraction in the Sea, vol. 4, part 1, Wiley-interscience, 74.
  12. Marquardt, C. W., 1963, An algorithm for least square estimation of nonlinear parameters, Journal of the Society for Industrial and Applied Mathematics, 11, 431-441. https://doi.org/10.1137/0111030
  13. Mucciarlli, M. and Gallipoli, M. R., 2006, Comparison between VS30 and other estimations of site amplification in Italy, First European Conference on Earthquake and Engineering and Seismology held in Geneva during Sept. 3-6 2006, Paper Num. 270.
  14. NEHRP, 1994. Recommended provisions for seismic regulations of new buildings: Part 1, provisions. FEMA 222A. National Earthquake Hazards Reduction Program (NEHRP), Federal Emergency Management Agency, Washington, D.C.
  15. Okada, H., 2003, The microtremor survey method, Society of Exploration Geophysicists, 127p.
  16. Park, C. B., Miller, R. D., Ryden, N., Xia, J., and Ivanov, J., 2005, Combined use of active and passive surface waves, JEEG, 10(3), 323-334. https://doi.org/10.2113/JEEG10.3.323
  17. Park, C. B., Miller, R. D., and Xia, J., 1998a, Ground roll as a tool to image near-surface anomaly, 68th Ann. Internat. Mtg, Soc. Expl. Geophys., Expanded Abstracts, 874-877.
  18. Park, C. B., Miller, R. D., and Xia, J., 1998b, Imaging dispersion curves of surface waves on multichannel record, 68th Ann. Internat. Mtg, Soc. Expl. Geophys., Expanded Abstracts, 1377- 1380.
  19. Park, C. B., Miller, R. D., and Xia, J., 1999, Multichannel analysis of surface waves. Geophysics 64, 800-808. https://doi.org/10.1190/1.1444590
  20. Rix, G. J. and Leipski, E. A., 1991, Accuracy and resolution of surface wave inversion. In Bhatia, S.K. and Blaney, G.W. (Eds.): Recent advances in instrumentation, data acquisition and testing in soil dynamics. Am. Soc. Civil Eng., 17-32.
  21. Schwab, F. A. and Knopoff, L., 1972, Fast Surface Wave and Free Mode Computations. In: B.A. Bolt (Ed.), Methods in Computational Physics, Vol.11, Academic Press, New York and London, 87-180.
  22. Thomson, W. T., 1950, Transmission of elastic waves through a stratified solid, Journal of Applied Physics, 21, 89-93. https://doi.org/10.1063/1.1699629
  23. Toksz, M. N., 1964, Microseisms and an attempted application to exploration, Geophysics, 29, 154-177. https://doi.org/10.1190/1.1439344
  24. Xia, J., Miller, R. D. and Park, C. B., 1999, Estimation of nearsurface shear-wave velocity by inversion of Rayleigh waves, Geophysics, 64, 691-700. https://doi.org/10.1190/1.1444578

피인용 문헌

  1. Site Characterization using Shear-Wave Velocities Inverted from Rayleigh-Wave Dispersion in Chuncheon, Korea vol.17, pp.1, 2014, https://doi.org/10.7582/GGE.2014.17.1.001