An integrated approach of remote sensing and geophysics for investigating geological structure in the East Vietnam Sea

The East Vietnam Sea (South China Sea) is a large area with the diversely complicated conditions of geological structure. In spite of over the past many years of investigation, many marine places have remained poorly understood because of a thick seawater layer as well as of the sensitive conflicts among the countries in the region. Fortunately, satellite altimeter technology is allowing the enhancement of marine investigation in any area. The spatial variation of the ocean surface topography can be measured by a very accurate radar altimeter mounted on a satellite. The ocean surface is an equipotential surface of the Earth's gravity field. Therefore it can be converted into marine satellite-derived gravity by using the mathematical model. The detailed satellite-derived gravity anomaly and its variants are essential for understanding geological structure and marine geophysics. They provide a reliable opportunity to geologists and geophysicists for studying the geological features beneath the oceanfloor. Also satellite altimeter data is perfect for planning the more detailed shipboard surveys. The satellite altimeter data is collected by the Geosat, ERS- 1/2 altimeters. The authors emphasize the application of satellite-derived data for investigating of geological structure in the East Vietnam Sea. The satellite data is compared and combined with the shipboard data and has resulted in a significant improvement on its accuracy and resolution. It is constrained by shipboard data using the finite difference, minimum curvature methods. The satellite-derived gravity along with the geophysical advanced methods such as finite difference, gravity gradient, gravity derivative, residual isostatic gravity etc, have brought out an unambiguous picture on the geological structure in the area. Many geological features, such as seafloor spreading ridges, fault systems, volcanic chains, seamounts and shear zones are revealed on the satellite-derived gravity maps as well as on its variants. Especially, it is more meaningful in the remote or sparsely surveyed areas. The achieved results are checked and confirmed by the shipboard and seismic data.