2024 Hyuganada Sea Earthquake

On 8 August 2024 at 07:42 local time, a magnitude 7.1 earthquake occurred in the Hyuganada Sea off eastern Kyushu, Japan. The event was centered at a focal depth of 24.0 km. Available records indicate this as the sole M7.1 earthquake in the region since 1 January 2000. The Hyuganada Sea lies above the Nankai Trough subduction zone, where the Philippine Sea Plate converges northwestward beneath the Amurian Plate at rates of approximately 4–6 cm per year. This tectonic setting produces both intraslab and interface seismicity. The 24 km depth places the hypocenter within the subducting slab, consistent with typical intermediate-depth events in the area. The broader Kyushu region records a long history of great earthquakes generated by the same plate boundary. Paleoseismic and historical data document recurrent megathrust ruptures along the Nankai Trough every 100–200 years, with the most recent major sequence occurring in the 1940s. While the 2024 event did not reach the magnitude of classic Nankai megathrust earthquakes (M8+), its location and depth align with the expected stress regime of the subducting slab. Seismic monitoring networks operated by the Japan Meteorological Agency and international agencies confirm ongoing background seismicity in Hyuganada, reflecting continuous plate convergence and slab dehydration processes that facilitate brittle failure at these depths.

References

USGS Earthquake Catalog Japan Meteorological Agency seismic database Provided event parameters (M7.1, 07:42 JST 8 Aug 2024, 24 km depth)