A gravity gradiometer to search for submarine ore deposits

Gravity surveys are useful in profiling the underground density structure. We propose a hybrid gravity survey method using gravimeters and gravity gradiometers to detect submarine ore deposits. This paper describes the development of a gravity gradiometer for this purpose. The required resolution is estimated to be finer than approximately 10 E (= 1 × 10
^-8
/s
²
), considering typical dimensions of submarine ore deposits and survey altitude from the seafloor. To attain the required resolution, we newly developed a gravity gradiometer comprising two vertically-separated accelerometers with astatic reference pendulums. Laboratory measurements showed that the gravity gradiometer attained the required resolution. Its design, performance, and future tasks are described.