Subsurface structure assessment for landfill using distributed acoustic sensing: A case study in Qingdao, China

As a rapidly developed seismic observation technology, distributed acoustic sensing (DAS) has shown great potential in many fields such as near surface wave imaging and oil and gas exploration. Taking a landfill site as an example, this research uses DAS seismic data to carry out the study of near surface wave imaging based on DAS. By analyzing the spectral characteristics of DAS ambient noise data, an ambient noise data screening method based on power spectral density (PSD) spectrum is proposed to obtain high-quality virtual shot gather and dispersion spectrum images. A joint active and passive dispersion curve (DC) inversion flow is designed to obtain the shear wave velocity profile. The result indicates the low-velocity layer at the top of the landfill site and the transverse discontinuous interface inside are found. At the same time, the resistivity profile is obtained by inversion of the high-density resistivity data collected from the landfill site, which shows the high-resistivity region on the surface and the transverse discontinuous interface of the internal resistivity. The spatial positions of the abnormal regions in the inversion profiles of the two physical property parameters are very consistent, which proves the effectiveness of the proposed method. Our research can lay a foundation for structural inspection of landfill based on DAS.