Deformation Process and Mechanism of the Frontal Megathrust at the Nankai Subduction Zone
Deformation Process and Mechanism of the Frontal Megathrust at the Nankai Subduction Zone
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DOI：
10.1029/2021gc009855
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发表时间：
2022-04
期刊：
影响因子：
3.7
通讯作者：
G. Kimura;Y. Hamada;S. Yabe;A. Yamaguchi;R. Fukuchi;Y. Kido;M. Lena;S. Toczko;H. Okuda;N. Ogawa;H. Morioka;K. Ujiie;D. Saffer
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文献类型：
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作者：
G. Kimura;Y. Hamada;S. Yabe;A. Yamaguchi;R. Fukuchi;Y. Kido;M. Lena;S. Toczko;H. Okuda;N. Ogawa;H. Morioka;K. Ujiie;D. Saffer
南海海槽俯冲带的前缘巨型逆冲断层被认为是一个孕震断层的基础上记录的摩擦加热，但基本的微观力学过程，作用于断层面上知之甚少。在这里，我们展示了一个横跨巨型逆冲断层钻探的岩心中的一层约2 mm厚的断层泥，其中富含蒙皂石的粉砂岩已转化为优先取向的伊利石聚集体。蒙皂石的几乎完全的故障是一致的快速摩擦加热在这个故障，但是，断层泥及其周围的微观结构断言一个实验产生的缓慢滑动。我们认为，缓慢的滑动与小的剪切应变叠加的纹理所产生的前一个更快，更大的滑动。这种解释的基础上的微构造证据表明，在减速，后滑，或地震间的俯冲带中观察到的，发生在正面的巨型逆冲断层周围的缓慢滑动。我们认为，伊利石为主的断层泥是有条件的稳定，可能会在不同的时间从快速转向缓慢滑动。
The frontal megathrust of the Nankai Trough subduction zone is recognized as a seismogenic fault based on a record of frictional heating, but the underlying micromechanical processes that act on the fault surface are poorly known. Here we present a layer of fault gouge ∼2 mm thick within a core drilled across the megathrust, in which smectite‐rich siltstone has been transformed into a preferentially oriented illite aggregate. The nearly complete breakdown of smectite is consistent with fast frictional heating on this fault; however, the microtextures of the gouge and its surroundings are asserted one produced experimentally by slow slip. We suggest that slow slip with small shear strain has overprinted the textures produced by the previous faster and larger slip. This interpretation based on microtectonic evidence suggests a slow slip around the frontal megathrust took place during slow down, afterslip, or interseismic as observed now going in subduction zone. We suggest that the illite‐dominated gouge is conditionally stable, likely to shift from rapid to slow slip at different times.