The Song Ma Fault zone (SMFZ) is crucial for understanding the collision mechanism and evolution of the Indian and Eurasian Plates. A three-year research plan was proposed to investigate the seismotectonic structure of the SMFZ more comprehensively. The main objective of the program was to deploy temporary broadband seismic stations around the shear zone to record high-quality microearthquakes. By using the data recorded at these stations, combined with the data obtained from local seismic networks, we conducted seismological analyses, including waveform inversion, to obtain accurate fault plane solutions, velocity models, and fault zone characteristics of microearthquakes. Furthermore, by using the high-quality waveform data recorded by the monitoring network, we obtained more precise fault plane solutions and insights into the seismogenic process of the SMFZ. The results were highly consistent with the local geological structure, indicating the presence of complex crustal fractures in the SMFZ. Our analyses of earthquake relocation and focal mechanisms revealed that the spatial distribution of earthquake events in the SMFZ yielded several distinct earthquake clusters, which were strongly correlated to the local geological structure and provided further insights into tectonic evolution. Examining the SMFZ, which is located in northern Vietnam, is critical for understanding the mechanism and evolution of the collision zone between the Indian and Eurasian Plates. According to the H-κ and common conversion point (CCP) stacking methods, the crustal thickness ranges from 26.0 to 29.3 km, and the average Vp/Vs ratio is approximately 1.77. The CCP results indicate crustal heterogeneity within the SMFZ, confirming that the SMFZ is a suture zone between the South China Plate and Indochina Plate. To study these mechanisms and their evolution, we performed body wave tomography to obtain the velocity structure. The results indicate that changes in the velocity structure beneath the fault zone are influenced by local geological structures, and the earthquake swarm is located between the SMFZ and Song La Fault. This study demonstrated the transition in the velocity structure of the region from a collision zone to a strike-slip fault zone, reflecting the geological and geophysical evolution of the Song Ma area.