Comparison of Shear-Wave Slowness Profiles at 10 Strong-Motion Sites from Noninvasive SASW Measurements and Measurements Made in Boreholes
Comparison of Shear-Wave Slowness Profiles at 10 Strong-Motion Sites from Noninvasive SASW Measurements and Measurements Made in Boreholes
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DOI：
10.1785/0120020030
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发表时间：
2002-12
影响因子：
3
通讯作者：
L. Brown;D. Boore;K. Stokoe
中科院分区：
文献类型：
--
作者：
L. Brown;D. Boore;K. Stokoe
表面波谱分析(SASW)方法是一种相对较新的原位确定横波慢度的方法。所有的测量都是在地面上进行的，这使得它比需要钻孔的方法成本低得多。SASW方法使用多个有源震源(从商用可控震源卡车到这里进行的研究的小型手持锤子)和不同的接收器间距来绘制视在相速度与频率之间的曲线。利用相速度对应于基模表面波的简化假设，正演模拟得到了地下剪切波慢度的估计。为了确定这一间接技术的可靠性，我们对SASW方法进行了盲法评估。在10个以前或后来进行过钻孔地震测量的强震台上进行了SASW测试；如果以前进行了钻孔地震测量，则不使用钻孔结果来解释SASW数据，反之亦然。从SASW和钻孔测量得到的横波慢度的比较通常是非常好的。对于大多数频率，预测的地震动放大系数的差异不到15%。此外，两种方法对其中7个站点给出了相同的NEHRP站点分类。对于其他三个地点，井下测量的平均速度仅比确定C/D级边界的速度大5-13米/秒。这项研究表明，在许多情况下，SASW方法可以提供适合于现场响应预测的地下信息。2002年1月18日收到手稿。
The spectral-analysis-of-surface-waves (SASW) method is a relatively new in situ method for determining shear-wave slownesses. All measurements are made on the ground surface, making it much less costly than methods that require boreholes. The SASW method uses a number of active sources (ranging from a commercial Vibroseis truck to a small handheld hammer for the study conducted here) and different receiver spacings to map a curve of apparent phase velocity versus frequency. With the simplifying assumption that the phase velocities correspond to fundamental mode surface waves, forward modeling yields an estimate of the subsurface shear-wave slownesses. To establish the reliability of this indirect technique, we conducted a blind evaluation of the SASW method. SASW testing was performed at 10 strong-motion stations at which borehole seismic measurements were previously or subsequently made; if previously made, the borehole results were not used for the interpretation of the SASW data, and vice-versa. Comparisons of the shear-wave slownesses from the SASW and borehole measurements are generally very good. The differences in predicted ground-motion amplifications are less than about 15% for most frequencies. In addition, both methods gave the same NEHRP site classification for seven of the sites. For the other three sites the average velocities from the downhole measurements were only 5-13 m/sec larger than the velocity defining the class C/D boundary. This study demonstrates that in many situations the SASW method can provide subsurface information suitable for site response predictions. Manuscript received 18 January 2002.