Fault weakening caused by smectite swelling
Fault weakening caused by smectite swelling
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DOI：
10.1186/s40623-019-1108-5
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发表时间：
2019-12-02
影响因子：
3
通讯作者：
Kimura, Gaku
中科院分区：
文献类型：
--
作者：
Kameda, Jun;Uno, Masaoki;Kimura, Gaku
2011年东北冲地震（M（w）9.0）期间，沿浅俯冲界面的大规模滑动沿着引起了袭击日本本州东北海岸的巨大海啸。综合大洋钻探计划远征343 JFAST计划显示，断层带主要由蒙皂石组成。我们使用断层材料的膨胀实验表明，膨胀压力系统地增加与样品孔隙度的减少。根据IODP钻孔中的原位孔隙度估计，断层的膨胀压力高达8 MPa，这与钻井现场的有效正应力（类似于7 MPa）相当。这也表明断层的修正有效围压相当低或可能为零，这意味着断层强度主要由粘聚力而不是摩擦强度决定。因此，断层可能是内在薄弱的，这可能会增加同震位移向沟槽时，地震滑动传播从深处。
The large slip along the shallow subduction interface during the 2011 Tohoku-Oki earthquake (M(w)9.0) 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 (similar to 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.