Very‐low‐frequency earthquakes indicate a transpressional stress regime in the Nankai accretionary prism
2009; American Geophysical Union; Volume: 36; Issue: 20 Linguagem: Inglês
10.1029/2009gl039332
ISSN1944-8007
AutoresYoshihiro Ito, Youichi Asano, Kazushige Obara,
Tópico(s)High-pressure geophysics and materials
ResumoWe 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.
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