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为获取城区浅部介质结构,利用台阵微振动观测技术对城区不同环境下的2个场地进行了微振动观测试验。研究设计了嵌套三角形观测系统,采用修正空间自相关法和频率波数法提取Rayleigh波频散曲线,选用邻域算法反演台阵下方各层埋深及其纵、横波速度结构,并对反演结果与现场钻孔勘察结果进行了对比分析。结果表明,台阵微振动观测技术是获取地壳浅部介质结构的一种有效方法,其对主要地层界面的深度解释误差约为3%~8%,该误差大小与界面的波阻抗差异有关,波阻抗越大,其解释精度相对越高;该方法可以直接获取台阵下方S波速度结构,且具有较高的精度。微振动方法不需要专门震源,施工经济方便,结果可靠,可作为复杂地震地质环境下获取城区地壳浅部介质结构的有效方法。
In order to obtain the medium structure in the shallow part of the urban area, micro-vibration observation test was conducted on two sites under different environments in the urban area by using the micro-vibration observation technique of the array. The nested triangulation system is researched and designed. The Rayleigh wave dispersion curve is extracted by modified spatial autocorrelation method and frequency wavenumber method. The neighborhood algorithm is used to inverse the depth of each layer beneath the array and its longitudinal and shear wave velocity structure. A comparison of the results with the results of borehole survey was made. The results show that the array micro-vibration observation technique is an effective method to obtain the crustal shallow medium structure, and the depth interpretation error of the main formation interface is about 3% ~ 8%. The error size is related to the difference of wave impedance of the interface, The higher the wave impedance is, the higher the interpretation accuracy is. This method can directly acquire the S-wave velocity structure under the array and has higher accuracy. Micro-vibration method does not require a special source, the construction economy is convenient and the result is reliable, which can be used as an effective method to obtain the shallow medium structure in urban crust under complex seismic geological environment.