Deep seismic data analysis of ridge jumps in the South China Sea

Ridge jumps are a common phenomenon in the seafloor spreading stage due to strong tectonic and magmatic effects, and geophysical data indicates that the ridge jumps exist in the multi-stage seafloor spreading process of the South China Sea (SCS). However, the deep velocity structural characteristics of the ridge jump are still unclear. The deep seismic survey line OBS2021-1 was implemented in 2021 by the National Natural Science Foundation of China (NSFC) shared expedition, which crosses the location of the ridge jump (J3) occurring in the eastern sub -basin of SCS. This paper presents the data acquisition of this survey line and completes preliminary data process work, such as the production of standard air gun navigation file (Ukooa file), the format conversion of the raw data, and the corrections of shooting and Ocean Bottom Seismograph (OBS) positions. The results show that the data quality of the OBS2021-1 survey line is good, and the OBS comprehensive seismic recording profiles can identify several sets of clear P -wave seismic phases, including Pw, Pg, PmP and Pn seismic phases, after the shots and OBSs location correction. The initial velocity model along the survey line is established based on processing interpretation of the Multi -Channel Seismic (MCS) acquired simultaneously and International Ocean Discovery Program (IODP) drilling data. We obtain the preliminary forward velocity model along the OBS2021-1 using the Raylnvr package, and the deep velocity structural characteristics of ridge jump are identified. The result shows the crust thickness is thicken, and Oligocene stratigraphy is missing in the multi -channel profile of ridge jump zone, which provide a deep research foundation for the further study of ridge jump process and for the construction of the formation and evolution history of SCS.