Ground substrate survey in black soil regions is a national assessment of natural resource conditions and national strength for the protection and utilization of black soil. It represents a new frontier where geological survey work provides support and services for natural resource management and ecological civilization. The high-resolution, cost-effective, and rapid acquisition of S-wave velocities at depths shallower than 50 m remains a critical technical challenge for investigating the structure of ground substrate layers in the black soil region of Northeast China. A mixed source surface wave exploration technique, combining active and passive sources, enables complementary advantages between these two distinct excitation methods. This approach facilitates the acquisition of high-resolution velocity structures and geological stratification of the ground substrate. A linear array with a roll-along geometry based on MASW（multi-channel analysis of surface waves） was used to acquire seismic data from both active and passive sources at identical survey points. Following a computational comparison of several dispersion analysis methods, the ESPAC (extended spatial autocorrelation) method was selected. Subsequently, dispersion energy maps from active and passive sources were merged, dispersion curves were extracted, and the surface wave velocity structure was iteratively inverted using a genetic algorithm. The reliability of the method was verified through calibration against known boreholes. Regionally, a sparse grid deployment with a point spacing of approximately 5 km was implemented, and a depth-to-bedrock map was compiled from the interpretation results. The results demonstrate that the ESPAC method enables the acquisition of passive source data using the observation array intended for active sources. The resulting dispersion spectra exhibit high consistency in the overlapping frequency bands, and survey efficiency was significantly improved. This study provides a technical demonstration for ground substrate surveys and the broader field of shallow geophysical exploration.