Risk Evaluation and Disaster Mitigation Research Division
Subduction Earthquake Lab
Research Subject(s)
Investigation of interplate earthquakes in subduction zones using GNSS-Acoustic seafloor geodetic observations
Development and improvement of faults slip inversion techniques
Key Words
Solid Earth Geophysics / Seafloor Geodesy / Inversion Analysis / Giant Subduction Earthquakes
Research Activities

We have conducted GNSS-Acoustic seafloor geodetic observations close to the huge earthquake source region to understand mechanism of subduction earthquakes and to evaluate their risks. It is known that a characteristic deformation is caused in each seismic period: before, during, after an earthquake. Through precisely detecting these deformations on seafloor, we aim to attain the above objectives. We successfully detected the postseismic deformation of the 2011 Tohoku-oki earthquake and contributed to understanding the details of the earthquake.

On a plate boundary of a subduction zone, various fault slip behaviors are caused: strain accumulation before an earthquake, rapid slip during the earthquake, and slow slip after the earthquake. These slip behaviors can be estimated by geodetic observational data. However, it is difficult to accurately estimate them due to insufficiency of observational data and complexity of geophysical models. Hence, we work on development of fault slip inversion techniques. We have developed an inversion technique using MCMC method that enables us to easily interpret the estimation errors and an inversion technique considering the viscoelastic structure of Earth.

Selected Works
  • Tomita, F. et Al. (2021). Development of a Trans‐Dimensional Fault Slip Inversion for Geodetic Data. Journal of Geophysical Research: Solid Earth, 126(5), doi:10.1029/2020jb020991
  • Tomita, F. et al. (2020). Improvement on spatial resolution of a coseismic slip distribution using postseismic geodetic data through a viscoelastic inversion. Earth, Planets and Space, 72(1), 84, doi:10.1186/s40623-020-01207-0
  • Tomita, F. et al. (2019). Development of a kinematic GNSS-Acoustic positioning method based on a state-space model. Earth, Planets and Space, 71, 102, doi:10.1186/s40623-019-1082-y
  • Tomita, F. et al. (2017). Along-trench variation in seafloor displacements after the 2011 Tohoku earthquake. Science Advances, 3, e1700113, doi:10.1126/sciadv.1700113
  • Tomita, F. et al. (2015). First measurement of the displacement rate of the Pacific Plate near the Japan Trench after the 2011 Tohoku-Oki earthquake using GPS/acoustic technique. Geophysical Research Letters, 42(20), 8391–8397, doi:10.1002/2015GL065746
Selected Memberships
  • The Seismological Society of Japan
  • The Geodetic Society of Japan
  • Japan Geoscience Union
  • American Geophysical Union