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High‐Density Seismic Refraction Imaging of Plate‐Boundary Structures in the Slow Earthquake Gap Zone off Western Kii Peninsula, Nankai Trough
Author(s) -
Qin Yanfang,
Fujie Gou,
Kodaira Shuichi,
Nakamura Yasuyuki,
Kaiho Yuka,
No Tetsuo,
Obana Koichiro,
Miura Seiichi
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl089132
Subject(s) - geology , seismology , subduction , accretionary wedge , trough (economics) , seismometer , seismic tomography , seismic refraction , receiver function , mantle (geology) , geophysics , tectonics , lithosphere , economics , macroeconomics
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 2018, a very dense array of 96 ocean‐bottom seismometers were 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.