Application and study of the DGS AT1M-11 marine gravimeter in the northeastern Indian Ocean^*

In marine areas, the study of the gravity field is of great significance for understanding marine dynamic processes, submarine geological structures, and global climate change. High-precision marine gravity exploration technology has become the current development trend in 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 met the requirements of the Marine Survey Measurement Specification. The measured data collected in the northeastern Indian Ocean in 2022 was compared with the gravity field data from the Gravity Recovery and Climate Experiment (GRACE), which showed a basically consistent trend. Additionally, the results of the pre- and post-cruise benchmark tests of the voyage and the gravity intersection point difference are −0.73 mGal and 1.15 mGal respectively, indicating that the data of this instrument is highly accurate 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, suggesting differences in equilibrium compensation for crustal thickness and that the ridge consists of non-homogeneous material. Gravity modeling of the free-air gravity anomalies obtained from the measured data indicates the presence of a thickened crust beneath the 90°E Ridge, associated with compensation for topographic relief loads.