Japan Geoscience Union Meeting 2025

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[J] Oral

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG59] Oceanic plate as inputs to subduction zone: evolution process of the oceanic plate

Sun. May 25, 2025 1:45 PM - 3:15 PM 304 (International Conference Hall, Makuhari Messe)

convener:Takanori Kagoshima(University of Toyama), Naoto Hirano(Center for Northeast Asian Studies, Tohoku University), Gou Fujie(Japan Agency for Marine-Earth Science and Technology), Yuya Akamatsu(Japan Agency for Marine-Earth Science and Technology), Chairperson:Takanori Kagoshima(University of Toyama), Naoto Hirano(Center for Northeast Asian Studies, Tohoku University), Gou Fujie(Japan Agency for Marine-Earth Science and Technology), Yuya Akamatsu(Japan Agency for Marine-Earth Science and Technology)

2:45 PM - 3:00 PM

[SCG59-05] Are earthquake nests beneath Kanto caused by subducted seamounts?

*Junichi Nakajima1 (1.Department of Earth and Planetary Sciences, Institute of Science Tokyo)

There are many earthquake nests (areas of highly concentrated seismic activity isolated from nearby activity) beneath Kanto region. The most active nest is located at the upper boundary of the Pacific plate at a depth of 60–70 km in the northern part of Tokyo Bay. Seismic wave analysis revealed that the earthquake nest is distributed in a circular shape with a radius of ~10 km, and the distribution of thrust earthquakes is slightly steeper than the average dip angle of the subducting Pacific plate. Furthermore, the characteristics of earthquake occurrence are spatially different, with many plate-interface earthquakes in the second quadrant, few plate-interface earthquakes in the third quadrant, and earthquakes of M≧5 occurring in the fourth quadrant. In this presentation, I propose the subduction of seamounts as a cause of the earthquake nests beneath the Kanto region.