11:30 AM - 11:45 AM
[SGD02-10] Monte Carlo Simulation of Gravity Gradient for Observing Volcanic Activity
Keywords:gravity gradient, volcano
The instrument we are developing is a new gravity gradiometer. The gravity gradiometer can measure vertical gravity gradients with a resolution of 10-9 1/s2 level at an observation station with seismic vibration. In this gravity gradiometer, two test bodies are thrown upward at different heights in a vacuum tank at the same time, and the difference between the free fall acceleration of the two test bodies is obtained by a Michelson interferometer. Gravity is proportional to 1/r2 and the gravity gradient in the vertical direction is proportional to 1/r3, where r is the distance between the gravitational source and the instrument. Therefore, the gravity gradiometer has a better sensitivity to nearby gravity sources, and is suitable for observation of the environmental disturbances, such as rainfall and groundwater fluctuation. Simultaneous observation of the absolute gravimeter and gravity gradiometer at the same observation station could allow us to estimate the displacement of the magma head more accurately.
Assuming a simple volcano model, we have calculated the gravity change by Monte Carlo simulation for Mt. Asama and Sakurajima volcanos, and examined the usefulness of the simultaneous observation of the absolute gravimeter and gravity gradiometer. In this presentation, I will report the results of the simulation and discuss the optimum observation station for the absolute gravimeter and gravity gradiometer.