EFFECTS OF NONLINEAR PROPERTIES OF SURFACE SOILS ON STRONG GROUND MOTIONS RECORDED IN OJIYA DURING 2004 MID NIIGATA PREFECTURE EARTHQUAKE(<Special Issue>Geotechnical Disasters in 2004 and 2005)
スポンサーリンク
概要
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The peak ground acceleration (PGA) of 13.08m/s^2 recorded at K-NET station in Ojiya city during the 2004 Mid Niigata Prefecture earthquake was 1.5-2 times greater than either of the other nearby stations on a similar soft soil (JMA) and on the outcrop rock (SSI). Those at K-NET during earthquakes with less intensity, however, tended to be smaller than those at JMA. The variation in relative magnitude of PGA with earthquake intensity is probably due to the difference in site conditions between K-NET and JMA. Field investigation including boring, PS logging, and spectral analysis of surface wave methods as well as laboratory tests on undisturbed samples obtained from the sites from this and previous studies reveal near-surface soil profiles and their nonlinear dynamic soil properties at both stations. Equivalent linear dynamic analysis is then performed using the detected soil profiles and properties for the two sites with the motions recorded at SSI as input outcrop motions. It is shown that, despite its very low shear wave velocity of about 50m/s, the near-surface peat at K-NET exhibits weaker nonlinearity with larger damping at small strains but with smaller damping at large strains than does the near-surface silt at JMA. This might have had strong effects on the extremely large peak acceleration at K-NET during the main shock as well as on the variation in relative magnitude of PGA between K-NET and JMA during earthquakes of different intensity.
- 社団法人地盤工学会の論文
著者
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Tokimatsu Kohji
Tokyo Inst. Of Technology Dept. Of Architecture And Building Engineering
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Tokimatsu Kohji
Tokyo Institute Of Technology
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SEKIGUCHI TORU
Tokyo Institute of Technology