China advances research on South China Sea's deep structure

(Xinhua) -- Researchers from a Chinese university have made breakthroughs in the study of the deep structure of the South China Sea.

Over the past 100 million years, a large number of Earth plates have subducted to the deep part of the South China Sea. However, due to the limitations on seabed observation, the deep structure of the South China Sea has been poorly understood, according to researchers from the Shenzhen-based Southern University of Science and Technology.

A hydronaut unhitches the rope on the crewed submersible Shenhai Yongshi (Deep Sea Warrior) from the scientific research ship Tan Suo Yi Hao (Discovery One) to make preparations for underwater investigation in the South China Sea, May 26, 2023. (Xinhua/Pu Xiaoxu)

The research team from the university used the data from a passive seismic experiment using ocean bottom seismometers, together with the land stations, to determine the high-resolution, three-dimensional seismic structure of the southwest sub-basin of the South China Sea.

The researchers discovered that there is an anomaly area at a depth of 40 to 80 km in the south of the basin with an obvious low seismic shear velocity, and the anomaly is most apparent at a depth of about 50 km, according to a research article published in the journal Nature Communications.

After deep thermodynamic and rock geochemical analysis, they obtained the geophysical evidence that the upper mantle in the southern South China Sea is relatively rich in water, and revealed the north-south asymmetry of the seismic wave velocity structure in the deep South China Sea.

The study is of great significance in revealing the deep structure of subducting plates, the genesis of many volcanoes and reefs in the South China Sea, and the water cycle in the earth subduction zone, according to the researchers.