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Journal Articles Earth Planets and Space Year : 2019

Fault weakening caused by smectite swelling

Masaoki Uno
  • Function : Author
Marianne Conin
Kohtaro Ujiie
  • Function : Author
Yohei Hamada
  • Function : Author
Gaku Kimura
  • Function : Author

Abstract

The large slip along the shallow subduction interface during the 2011 Tohoku-Oki earthquake (Mw9.0) caused a huge tsunami that struck the northeast coast of Honshu, Japan. The Integrated Ocean Drilling Program Expedition 343 JFAST program revealed that the fault zone is composed primarily of smectite. Our swelling experiments using the fault material demonstrated that the swelling pressure systematically increases with a decrease in sample porosity. Based on in situ porosity estimations in the IODP borehole, the swelling pressure of the fault is as high as 8 MPa, which is comparable to the effective normal stress at the drill site (~ 7 MPa). This also suggests that the modified effective confining pressure of the fault is quite low or potentially zero, meaning that fault strength is governed mainly by cohesion rather than frictional strength. The fault may therefore be intrinsically weak, which could enhance the coseismic displacement toward the trench when earthquake slip propagates from depth.
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hal-02982526 , version 1 (30-08-2021)

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Jun Kameda, Masaoki Uno, Marianne Conin, Kohtaro Ujiie, Yohei Hamada, et al.. Fault weakening caused by smectite swelling. Earth Planets and Space, 2019, 71 (1), ⟨10.1186/s40623-019-1108-5⟩. ⟨hal-02982526⟩
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