近地表速度结构的地脉动探测方法国际盲比检验

International blind test of microtremors method for near-surface velocity structure exploration

本文通过参加ESG2006组织的国际地脉动盲比测验,检验了利用地脉动方法探测近地表速度结构的精度和可信度.在对多个不同测试模型频散曲线的提取精度、速度结构平均速度相对偏差和场地放大效应估计等方面的比较中,本文方法在参加盲比测验的19个国际研究组中均处于前列.同时盲比测验结果表明,不论人工合成记录还是实际观测记录、速度还是加速度记录,地脉动空间自相关方法得到的场地瑞利波频散曲线,均能够为后续反演研究提供可靠的目标曲线;可以根据仪器实际情况自由选择观测加速度或速度.人工合成数据分析中,有两例频散曲线受到了高阶振型影响,在实际观测数据中影响不明显.结合盲比测验结果指出,空间自相关方法的最大可探测波长一般达不到通常认为的15.7倍的最大半径,大多情况小于10倍;而最小波长要小于2倍的最小半径,可以到1倍的最小半径.

In this paper, the microtremors method for site near-surface S-wave velocity structure exploration is validated by international blind test. In the comparison of precision of dispersion curves, the relative deviation of average velocity and site amplification effects, all the results from this paper are among the best results of the 19 research groups involved. And the results show that the method obtains reliable results either from artificial records or in-situ observation records in acceleration or velocity. Either of them can be chosen in observation contingent on the capability of instruments. Although higher modes of dispersion curves are observed in 2 cases in artificial records analysis, but in microtremors records observed in-situ it is not notable. Based on the above results, it＇s pointed out that in most cases the largest reliable wave length of SPAC can only reach to 10R can not reach to usually considered 15.7Rmax, and the shortest reliable wave length is less than 2Rmin and can reach to Rmin.