[S-CG50] Earthquakes, Tsunamis, Seismotectonics, and Hazard Potential of the Ryukyu Trench and Okinawa Trough

[SCG50-01] Earthquakes, Tsunamis, Seismotectonics, and Hazard Potential of the Ryukyu Trench and Okinawa Trough - Introduction

*Kenji Satake^1,2, Mamoru Nakamura³, CHANG PINGYU^1,2, J. Bruce H. Shyu⁴ (1.Dept. Earth Sciences, National Central University, Taiwan, 2.University of Tokyo, 3.University of the Ryukyus, 4.National Taiwan University)

Along the Ryukyu trench between Kyushu and Taiwan, the Philippine Sea plate subducts beneath the Eurasian Plate with a rate of approximately 8 cm/year. Unlike the neighboring Nankai Trough, the history of great interplate earthquakes is not well known, except for the enigmatic 1771 Meiwa earthquake, which caused more than 10,000 casualties due to tsunami. The Hualien earthquake on April 3, 2024 (M 7.4) originated from this plate boundary, causing the worst earthquake damage to Taiwan since the 1999 Chi-chi earthquake. The Hualien earthquake also prompted a tsunami warning in Ryukyu Islands, Japan.
The Okinawa Trough, which is located on the northwest side of the Ryukyu Arc, is currently in the early stages of back-arc rifting. Associated with the rifting, seismic swarm activity and hydrothermal activity are also active within the trough. However, the mechanism of the Okinawa Trough's extension is still unknown.
The geodetic measurements on the Ryukyu islands indicate that the plate coupling is very weak, while recent offshore geodetic measurements indicate coupled patches along the megathrust. Slow earthquakes have been observed along the Ryukyu trench.
In order to exchange current knowledge on the Ryukyu trench and stimulate further collaboration between Taiwan and Japan, we organized a joint session between Chinese Geoscience Union in Taiwan (TCGU) and JpGU. The submitted papers include the structures of Ryukyu Trench, Okinawa trough and their extensions, slow and regular earthquakes in Ryukyu Trench, studies of the 2024 Hualien earthquake and its tsunami, submarine landslides and turbidity currents in the region.