DEVELOPMENT OF REAL-TIME GEOPHYSICAL EXPLORATION SYSTEM BASED ON ARRAY OBSERVATION OF THREE-COMPONENT MICROTREMORS

除了适用于评估土壤剖面和地面运动特征的空间变化外，还介绍了利用微震三分量地面运动进行岩土工程场地表征的现场技术和分析程序。该系统可以很容易地提供微震三分量地震动谱分析的瑞利波和洛夫波色散曲线以及H/V谱。从理论上推导了考虑高模效应的表面波色散曲线和H/V谱。利用瑞利波频散曲线和洛夫波频散曲线或H/V谱进行逆分析，确定剪切波速剖面。结果表明：(1)在任何情况下，瑞利波的理论频散曲线与微震垂直运动的F-k谱分析结果吻合较好。(2)当微震从一个方向传播时，更洛夫波的理论频散曲线与微震横向水平运动的F-k谱分析结果吻合较好。(3)提出的表面波H/V谱与实测微震H/V谱吻合较好，证明了其有效性。(4)采用瑞利波频散曲线和love波频散曲线或H/V谱的反演过程比只采用瑞利波频散曲线反演得到的横波速度曲线更可靠。为了证明所提出方法的有效性，在钏路和神户进行了阵列微震测量，并分别估计了这些地区的剪切结构深度约为50 m和1.5 km。计算得到的剪力结构与常规方法计算得到的剪力结构吻合较好，表明了该方法的有效性。然后利用估算的土壤剖面进行有效应力响应分析。计算得到的峰值地速度和加速度的分布以及台站间的传递函数与地震时的观测结果一致，表明所提出的方法是有前途的。少

Field techniques and analytical procedures have been presented for geotechnical site characterization using microtremor three-component ground motions, in addition to their applicability for evaluating spatial variation of soil profiles and ground motion characteristics. The present system can readily provide Rayleigh- and Love-wave dispersion curves as well as H/V spectra from spectrum analyzes of microtremor three-component ground motions. The dispersion curves and H/V spectra of surface waves have been theoretically derived in which the effects of higher-modes can be taken into account. Inverse analyzes using both Rayleigh-wave dispersion curve and Love-wave dispersion curve or H/V spectra have been presented for determining shear wave velocity profiles.It is shown that :(1) The theoretical dispersion curve of Rayleigh waves shows a good agreement with those determined by te F-k spectrum analysis of the microtremor vertical motions in any case.(2) The theoretical dispersion curve of … More Love waves shows a good agreement with those determined by the F-k spectrum analysis of the microtremor transverse horizontal motions, if microtremors propagate from one direction.(3) The proposed H/V spectrum of surface waves shows a good agreement with observed microtremor H/V spectrum, claiming its validity.(4) The proposed inversion process using both Rayleigh-wave dispersion curve and Love-wave dispersion curve or H/V spectra can yield more reliable shear wave velocity profiles than that using Rayleigh-wave dispersion curve only.To demonstrate the effectiveness of the proposed methods, microtremor measurements using arrays are conducted in Kushiro and Kobe and the shear structures in those areas are estimated down to depths of about 50 m and 1.5 km, respectively. The estimated shear structures are in good agreement with those determined by the conventional methods, indicating the effectiveness of the proposed method. Effective stress response analysis is then made using the estimated soil profiles. The computed distribution of the peak ground velocity and acceleration as well as the transfer funcion between stations are consistent with those observed during the earthquakes, suggesting that the proposed methods are promising. Less