Ryuta Arai is a marine seismologist investigating how the structure and physical properties of tectonic plates influence earthquakes, slow earthquakes, fluid migration, and magmatic processes. He uses active- and passive-source seismic observations, with a particular emphasis on high-resolution three-dimensional seismic imaging, to reveal the hidden architecture of the Earth beneath the seafloor.
A central theme of his research is the link between geological heterogeneity and geodynamic processes. In subduction zones, he investigates how seamounts, basement highs, crustal structure, and fluids influence megathrust slip and slow earthquakes. For example, seismic imaging in the Hyuga-nada region of southwest Japan has revealed a thickened subducting crust and fluid-related structures above the plate interface, helping to clarify how subducting topography and fluids may influence slow earthquake activity. In the southern Okinawa Trough, his research focuses on the structure of back-arc rifting and the distribution of magmatic intrusions and fluids, providing insights into how continental crust undergoes extension and evolves toward oceanic spreading.
His research has also involved tectonically active regions including the Ryukyu Trench, Izu Collision Zone, Izu-Bonin Arc, Hikurangi Margin, Lau Basin and Mid-Atlantic Ridge. Ryuta Arai has been working at JAMSTEC since 2014 and is currently a Group Leader and Senior Researcher of the Marine Geophysical Research Group (MGG), Research Center for Marine Geodynamics Observations (MGeo), Research Institute for Marine Geodynamics (IMG), JAMSTEC.
November 4–6, 2026 — Seismological Society of Japan Fall Meeting @ Nagoya
December 7–11, 2026 — AGU Fall Meeting @ San Francisco
August 2026 — New Geophysical/Geological cruise in Hyuga-nada
Completed the second leg of the KH-26-5 cruise in Hyuga-nada
July 2026 — New paper on the Okinawa Trough
Our new study of the southern Okinawa Trough was published in Journal of Geophysical Research: Solid Earth. Using seismic reflection imaging, we investigate the relationship between magmatic intrusions, fluid/gas distribution, and crustal rifting in the Yaeyama Rift.