AN EXAMINATION OF NON-LINEARITY EFFECTS USING OBSERVEDRECORDS BY THE WARNING INFORMATION SYSTEM OFEARTHQUKAKE (WISE) IN HOKKAIDO, JAPAN

摘要

Site effects on peak ground motion, especially non-linearity behaviors on amplification at subsurfacelayers using the strong motion records observed at the Warning Information System of Earthquake(WISE) in Hokkaido, Japan. First the attenuation relation for peak ground velocity (PGV) of the surfaceground of Tertiary deposit and in the engineering bedrocks are developed from records at 146 sites ofWISE observatories. The site amplification factors were derived from the ratio of the maximum observedvalues of PGV to the values from the attenuation relation for the surface ground of the Tertiary deposit.The correlation between the site amplification and the average shear wave velocity in the subsurfacelayers shows almost coincidence with the existing relationship derived from Midorikawa et al. [1] atanother sites of Japan. The amplification factors of the 2003 Tokachi-Oki earthquake records are smallerthan of the observation records from small earthquakes before the 2003 Tokachi-Oki earthquake. Then theaverage shear strain levels of the records are evaluated by the ratio between the PGV at ground surfaceand the average shear wave velocity within the subsurface layers. The shear strain level analysis show theeffect of the nonlinearity on the amplification factors of the peak ground velocity does not becomesignificant within the shear strain level equals to 1×10-3.