Abstract: In marine areas, the study of gravity field is of great significance for understanding marine dynamic processes, submarine geological structure and global climate change. High-precision marine gravity exploration technology has become the current development trend of marine gravity field investigation. The R/V Shiyan 6 of the South China Sea Institute of Oceanography, Chinese Academy of Sciences, is equipped with a DGS AT1M-11 marine gravimeter, which is characterized by high precision, high reliability, and the ability to conduct global dynamic measurements. Before the gravimeter was put into use, the accuracy was evaluated, including static tests and internal conformity accuracy tests, all of which resulted in compliance with the Marine Survey Measurement Specification. Using the measured data collected in the Northeast Indian Ocean in 2022 to compare with the gravity field data from the Gravity Recovery and Climate Experiment (GRACE), the results show a basically consistent trend, and the results of the pre- and post-cruise benchmark tests of the voyage and the gravity intersection point difference are -0.73mGal and 1.15mGal respectively, indicating that the data of this instrument has high accuracy and can be used for high-precision marine gravity measurements. The gravitational field of the 90°E ridge north of 10°S is not proportional to the water depth, indicating that there are differences in equilibrium compensation for crustal thickness and that the ridge consists of non-homogeneous material. Gravity modeling of the free-space gravity anomalies obtained from the measured data suggests that there is a thickened crust beneath the 90°E Ridge associated with compensation for topographic relief loads.

Key words: DGS AT1M-11 marine gravimeter, 90°E ridge, Northeast Indian Ocean, Gravity modeling, R/V Shiyan 6