SUMARRY

Determination of the Moho surface depth

in the area of the Vietnam Central continental shelf -Hoàng Sa

based on seismic data and three-dimension gravitational inverse

Trần Văn Khá, Đỗ Đức Thanh, Hoàng Văn Vượng

The Moho structure of the Vietnam Central continental shelf - Hoàng Sa has been studied by numerous Vietnamese and foreign geologist based on geophysical data. In these studies, the depth of Moho surface of the central continental shelf-Hoàng Sa was constructed from Moho surface-depth calculations for the entire East Sea using reference Moho surface depth values of seismic data. However, no reference Moho surface depths was determined for the continental shelf of the study area. Since that, the accuracy of these previous calculations is limited. In this paper, two reference depth values of the Moho surface calculated from deep seismic data were added to solve the gravitational inversion and elucidate the structre of the Moho suface in the study area. The results indicated that the depth of the Moho surface ranges from 12 km to 18 km in the Phú Khánh basin, from 22 km to 30 km in the South of Sông Hồng basin, and from 18 km to 22 km in Hoàng Sa archipelago.

Keywords: Moho structure, gravity anomaly, 3D gravity inversion, Vietnam Central continental shelf - Hoang Sa.