[S-GD01] Geodesy and Global Geodetic Observing System

[SGD01-P06] Geoid changes in and around Japan

*Koji Matsuo¹ (1.Geospatial Information Authority of Japan)

Keywords:Geoid, Gravity, Height Reference Frame, GRACE

The Geospatial Information Authority of Japan (GSI) is planning to shift the Japanese height reference system from a spirit leveling-based system to a GNSS and geoid-based system. To this end, GSI has conducted a nationwide airborne gravity survey over Japan from 2019 to 2023 to develop a highly accurate gravimetric geoid model for Japan. It is known that the geoid is extremely stable compared to the geometry of the Earth, however, it changes from time to time due to mass redistributions associated with recent climate change and massive earthquakes. In particular, Japan is experiencing one of the largest geoid changes in the world due to large-scale mantle flow associated with viscoelastic response after the 2011 Tohoku-Oki earthquake. This study aims to evaluate geoid changes in and around Japan and perform their geophysical interpretations for efficient maintenance of a new height reference system for Japan. The geoid changes will be evaluated by using gravity data from the GRACE/GRACE-FO satellites. Interpretation of the observed geoid changes will be performed using various geodetic satellite data and geophysical models.