三分量背景噪声成像在当涂某地区浅地表勘探中的应用
Application of Three-Component Background Noise Imaging in Shallow Surface Exploration in a Certain Area of Dangtu

随着我国现代化进程的加快，城市地下空间的合理利用变得尤为重要。然而，传统的工程物探方法诸如重力调查、钻井和电磁探测技术等易受到人口和环境的限制，在城镇地区难以施展。在这种环境下，背景噪声成像作为一种安全、高效、对环境无损的工程物探方法，在浅地表勘探中被广泛应用。由于单分量检波器只能采集垂向分量的地震记录，以往大部分对背景噪声的研究主要集中在利用垂直分量地震数据提取瑞雷波进行频散成像，这容易导致频散成像的频带范围受限且高阶模态下易受到“模式接吻”的干扰进而影响成像精度。本文通过利用三分量检波器布置线性密集阵列采集当涂某地区的背景噪声数据，分析该地区三分量背景噪声的频谱特征。随后使用地震干涉法处理获取高质量的虚拟炮集记录，并进行频散分析提取瑞雷波与勒夫波的频散曲线进行联合反演成像。通过瑞雷波频散曲线单独反演与瑞雷波、勒夫波频散曲线联合反演比较可以看出，联合反演得到的速度剖面与测井结果具有更好的对应关系。这证明了与单一反演瑞雷波频散曲线相比，联合反演瑞雷波频散曲线和勒夫波频散曲线可以有效地提高反演精度并减少非唯一性。
With the speeding up of modernization in China, the rational utilization of urban underground space becomes particularly important. However, traditional engineering geophysical exploration methods such as gravity survey, drilling and electromagnetic detection technology are easy to be limited by population and environment and can not be applied in urban areas. In this environment, background noise imaging is widely used in shallow surface exploration as a safe, efficient and non-destructive engineering geophysical exploration method. Since single-component geophone can only collect vertical seismic records, most previous research on background noise mainly focuses on extracting Rayleigh waves from vertical seismic data for dispersion imaging, which is easy to lead to the limited frequency band of dispersion imaging and the interference of “mode kissing” in high-order modes, thus affecting the imaging accuracy. In this paper, a linear dense array of three-component detector is used to collect the background noise data of a certain area in Dangtu, and the spectral characteristics of the three-component background noise in this area are analyzed. Then, the high-quality virtual gun set records are obtained by seismic interferometry, and the dispersion curves of Rayleigh wave and Love wave are extracted by parallel dispersion analysis for joint inversion imaging. By comparing the Rayleigh wave dispersion curve inversion with the Rayleigh wave and Love wave dispersion curve inversion, it can be seen that the velocity profile obtained by the joint inversion has a better correspondence with the logging results. It is proved that, compared with single inversion of Rayleigh wave dispersion curve, the joint inversion of Rayleigh wave dispersion curve and Love wave dispersion curve can effectively improve the inversion accuracy and reduce the non-uniqueness.