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Very‐low‐frequency earthquakes indicate a transpressional stress regime in the Nankai accretionary prism
Author(s) -
Ito Yoshihiro,
Asano Youichi,
Obara Kazushige
Publication year - 2009
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 - 10.1029/2009gl039332
Subject(s) - geology , accretionary wedge , seismology , thrust fault , trench , stress field , tectonics , borehole , cauchy stress tensor , subduction , geotechnical engineering , chemistry , physics , organic chemistry , layer (electronics) , classical mechanics , finite element method , thermodynamics
We investigated the stress field within the Nankai accretionary prism of southwestern Japan, where very‐low‐frequency (VLF) earthquakes occur associated with thrust faulting. A northwest–southeast azimuth of the maximum horizontal principal stress previously estimated from borehole breakouts in wells drilled in the region by deep‐sea drilling vessel Chikyu suggests trench‐normal shortening, although strike‐slip and normal faulting are also possible within a thrust‐dominated tectonic environment. We estimated stress orientations and stress ratios by using stress tensor inversion to derive moment tensor solutions for VLF earthquakes in three regions along the Nankai Trough: off Kumano, off Muroto, and Hyuga‐nada. The stress orientations we obtained indicate that the regions off Kumano and off Muroto are within a transpressional stress regime with trench‐normal shortening, whereas the Hyuga‐nada region on the westernmost edge of the Nankai accretionary prism is in a reverse‐faulting regime.