Fluidization of granular material in a subduction thrust at seismogenic depths
Fluidization of granular material in a subduction thrust at seismogenic depths
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DOI：
10.1016/j.epsl.2007.04.049
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发表时间：
2007-07-30
影响因子：
5.3
通讯作者：
Toh, Shoichi
中科院分区：
文献类型：
--
作者：
Ujiie, Kohtaro;Yamaguchi, Asuka;Toh, Shoichi
从地震发生深度挖掘出的俯冲逆冲断层可能记录了俯冲带地震期间的动态滑动过程。日本西南部四万十增生杂岩中的逆冲断层叠瓦状沉积岩和玄武岩的混杂岩，代表与地震发生深度（深度4-6公里，温度= 130-150摄氏度）俯冲冲断层向下台阶相关的双重底侵作用。一个暴露良好的双断层带主要由玄武岩衍生的叶状碎裂岩和超碎裂岩组成。断层带结构表明滑移定位于不同岩性之间边界处的 2-20 厘米厚的超碎裂岩层。沿着超碎裂岩层观察到的共同特征是颗粒材料注入混杂岩中，而没有对细颗粒颗粒进行分选，并且注入材料中碎片对应物的检测概率很小，这表明断层期间流化颗粒材料的快速注入。超碎裂岩层以与流体相关的过程为标志，如沿着超碎裂岩的无定形硅胶的蚀变和沉淀以及超碎裂岩附近脉的集中所表明的。流体渗透条件下局部滑移过程中的流化可能是由于热加压造成的，这导致流体压力接近岩石静压值。流化粒状材料的注入可以由响应于与热加压相关的流体压力的增加的水力压裂而产生。当地震期间颗粒材料由于热加压而流化时，可以润滑板块边界俯冲推力。 (c) 2007 Elsevier B.V. 保留所有权利。
Subduction thrusts exhumed from scismogenic depths may record the dynamic slip processes during subduction zone earthquakes. The thrust faults in the Shimanto accretionary complex of southwest Japan imbricate the melange derived from sedimentary rocks and basalt, which represent a duplex underplating associated with the downward step of the subduction thrust at seismogenic depths (4-6 km in depth, temperature= 130-150 degrees C). One well-exposed duplex-fault zone consists mainly of foliated cataclasites and ultracataclasites derived from basalt. The fault zone structure suggests slip localization along the 2-20 cm thick ultracataclasite layer at the boundary between different lithologies. The common features observed along the ultracataclasite layer are the injection of granular material into the melange without the sorting of fine-grained particles along with a small detection probability of the fragmented counterparts in the injected materials, which suggests a rapid injection of fluidized granular material during faulting. The ultracataclasite layer is marked by fluid-related processes, as indicated by the alteration and precipitation of amorphous silica gel along the ultracataclasite and the concentration of veins near the ultracataclasite. The fluidization during localized slip under fluid-infiltrated conditions could be due to thermal pressurization, which causes the fluid pressure to approach lithostatic values. The injection of fluidized granular material may result from hydraulic fracturing in response to an increase in the fluid pressure associated with thermal pressurization. The plate boundary subduction thrust could be lubricated when the granular material fluidizes due to thermal pressurization during earthquakes. (c) 2007 Elsevier B.V. All rights reserved.