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在1995年兵库县南部地震期间,日本尼崎、高砂和南光3处钻孔场地的地表台站分别观测到了507cm/s2以上、187cm/s2和126cm/s2的水平峰值地面加速度(PGA)的强运动。利用对强弱地震动的互相关和频谱比的分析,我们给出了除南光之外在尼崎、高砂两处强地震动期间土壤非线性响应的定性证据。我们通过对剪切波速和与频率相关的阻尼因子的反演来评估土壤的非线性。反演得到砾石土的剪切模量比的应变依赖性比粘性土的要大,这与实验室试验结果一致。剪应变在10-4～10-3之间时,反演得到的尼崎、高砂两处砾石土和粘性土的剪切模量比的应变依赖性,分别同砾石土和粘性土实验室试验结果的经验关系相一致。这些结果支持了在砾石土和粘性土场地利用实验室试验所得剪切模量比来模拟强地震动。在尼崎,由主震反演得到的砾石土的阻尼因子在3个场地之中是最大的,但是阻尼因子的应变依赖性不如剪切模量比的应变依赖性那样显著。阻尼因子的应变依赖性不太显著的原因可能是由于散射衰减在低应变范围处于相对优势地位所致。
During the southern earthquake in Hyogo in 1995, surface ground stations at three drilling sites in Amagasaki, Takasago and Nanguang in Japan respectively observed strong peak ground acceleration (PGA) of 507cm / s2, 187cm / s2 and 126cm / s2 movement. Using cross-correlation and spectral ratio analysis of strong and weak earthquakes, we present qualitative evidence of soil nonlinear response to strong earthquakes in Amagasaki and Takasago except for the Nanguang wave. We evaluated the soil’s nonlinearity by inverting the shear wave velocity and the frequency-dependent damping factor. The strain dependence of the shear modulus ratio of the gravelly soil obtained by inversion is larger than that of the clayey soil, which agrees with the laboratory test results. The strain dependence of the shear modulus ratio of the two gravelly soils and cohesive soils retrieved from Amagasaki and Gaosha when the shear strain was between 10-4 and 10-3 was compared with the laboratory test results of gravelly soil and cohesive soil respectively Consistent with the empirical relationship. These results support the use of laboratory-derived shear modulus ratios at gravel and clay sites to simulate strong earthquakes. In Amagasaki, the damping factor of the gravelly soil derived from the main shock inversion is the largest among the three sites, but the strain dependence of the damping factor is not as significant as the strain dependence of the shear modulus ratio. The reason why the strain dependence of the damping factor is less pronounced may be due to the fact that the scattering attenuation is in a relatively dominant position in the low strain range.