Research progress of deep seismic exploration and S-wave velocity structure in the South China Sea

Deep seismic exploration has provided critical velocity structure support for the study of the formation and evolution of the South China Sea (SCS), while research on converted shear-wave (S-wave) velocity structures demonstrates irreplaceable advantages in investigating variations of material properties within the Earth′s interior. This paper reviews the development history of deep seismic exploration in the SCS, introduces the identification and methods of converted S-waves, and summarizes strengths and limitations of the forward modeling and inversion approaches respectively in S-wave velocity structure studies. Special emphasis is placed on the significant progress achieved through joint P- and S-wave investigations. They include: (1) Elucidating the origin of high-velocity lower crust beneath the northern SCS continental margin, (2) Verifying the conjugate positions of the northern and southern continental margins of the SCS, and (3) Revealing the continent-ocean transition process and initial oceanic crust accretion in the southwestern sub-basin of the SCS. Finally, technical breakthroughs are proposed in three aspects: three-dimensional S-wave velocity structure, quantification of water-rock interactions, and artificial intelligence applications, aiming to better serve scientific frontiers and energy development in the SCS. This research not only deepens understanding the theory of formation and evolution of the SCS, but also contributes to promoting the in-depth utilization of ocean bottom seismometer data and the advancement of deep sea exploration.