Shallow Structure Imaging Using Multi-mode Dispersion Curves Based on Multi-window HLRT in DAS Observation

Distributed acoustic sensing (DAS) is a high-density seismic observation system emerging in recent years. It can achieve low-cost and high-density observation and is one of the important methods for imaging city shallow structure. However, the high-mode dispersion spectrum information recorded by DAS system is difficult to utilize effectively. To solve this problem, we propose to extract multi-mode dispersion curves of active and passive sources through multi-window high-resolution linear Radon transform (HLRT) method and invert multi-mode dispersion curves of active and passive sources to construct shallow surface underground S-wave velocity structure. The research results show that the multi-window HLRT transform method can effectively extract multi-mode dispersion curves from DAS records by adding time windows; the improved objective function further enhances the stability and accuracy of inversion. The development of multi-mode dispersion curves extraction and inversion technology provides a new method for low-cost and high-resolution exploration of underground structures with DAS system.