资源环境科技发展态势分析平台

Despite recent observations of slow earthquakes along the Nankai subduction zone, none have been reported in the central Nankai Trough between the Kii Channel and Cape Shionomisaki. In November and December 2018, a very dense array of 96 ocean bottom seismometers was deployed by JAMSTEC to acquire active‐source seismic refraction dataset (supplemented by a multichannel seismic reflection profile) from the seaward side of the subduction trough to the accretionary prism off Cape Shionomisaki. We applied traveltime tomography to the refraction data to constrain the P‐wave velocity down to the upper mantle, coordinating with a migrated seismic reflection profile to confirm the depth of the Moho and interpret shallower structural features. From a comparison with a transect across the Kumano basin, we conclude that structural and physical differences between these two locations, especially the geometry of the subducting plate surface, lead to different slow earthquake activities.

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