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Cyclic ridge subduction at an inter‐plate locked zone off central Japan
Author(s) -
Kodaira Shuichi,
Nakanishi Ayako,
Park JinOh,
Ito Aki,
Tsuru Tetsuro,
Kaneda Yoshiyuki
Publication year - 2003
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 - 10.1029/2002gl016595
Subject(s) - geology , subduction , seismology , seamount , episodic tremor and slip , ridge , trough (economics) , thrust , thrust fault , reflection (computer programming) , fracture zone , tectonics , paleontology , physics , macroeconomics , computer science , economics , programming language , thermodynamics
There are significant variations in the size, especially lateral extent, of the co‐seismic rupture zones and inter‐plate locked zones for an inter‐plate mega‐thrust earthquake. Obvious factors controlling those variations have been still unsolved questions. We designed integrated seismic profiles, including a wide‐angle seismic profile and a multichannel reflection seismic profile, at the eastern Nankai trough in central Japan. Refraction tomography and pre‐stack depth migration of wide‐angle seismic data successfully image a trough‐parallel cyclic ridge subduction, with thickness of 13–20 km and wavelength of 35–50 km, at a geodetically determined inter‐plate locked zone in a non‐rupture zone during the 1944 Tonankai mega‐thrust earthquake. This result suggests a first direct evidence for the “subducted seamount = strongly locked” hypothesis.