Clay‐clast aggregates: A new textural evidence for seismic fault sliding?
Clay‐clast aggregates: A new textural evidence for seismic fault sliding?
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DOI：
10.1029/2007gl032554
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发表时间：
2008-03
影响因子：
5.2
通讯作者：
S. Boutareaud;D. Calugaru;R. Han;O. Fabbri;K. Mizoguchi;A. Tsutsumi;T. Shimamoto
中科院分区：
文献类型：
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作者：
S. Boutareaud;D. Calugaru;R. Han;O. Fabbri;K. Mizoguchi;A. Tsutsumi;T. Shimamoto
为了确定粘土层泥中滑移弱化的过程，在饱和和非饱和初始条件下，进行了0.6 Mpa法向应力下的地震滑移率(相当于0.9m/S和1.3m/S)下的旋转剪切试验。无论初始湿度条件如何，模拟断层的力学行为都显示出可重复的滑动弱化行为。通过对饱和和非饱和初始条件下残余摩擦阶段得到的断层泥的检验，可以定义出两种类型的微结构：反映应变局部化的分层型和由球形集合体组成的非分层型。摩擦实验表明，由于摩擦加热导致的水在断层泥中的液汽转变很好地解释了驱替头几米内球形聚集体的形成。这一结果表明，天然粘土断层泥中球状集合体的存在，为地震滑动速度下的浅层孔隙水相变，进而为过去的地震断层滑动提供了新的结构证据。
To determine the processes responsible for slip‐weakening in clayey gouge zones, rotary‐shear experiments were conducted at seismic slip rates (equivalent to 0.9 and 1.3 m/s) at 0.6 MPa normal stress on a natural clayey gouge for saturated and non‐saturated initial conditions. The mechanical behavior of the simulated faults shows a reproducible slip‐weakening behavior, whatever initial moisture conditions. Examination of gouge obtained at the residual friction stage in saturated and non‐saturated initial conditions allows the definition of two types of microstructures: a foliated type reflecting strain localization, and a non‐foliated type composed of spherical aggregates. Friction experiments demonstrate that liquid‐vapor transition of water within gouge due to frictional heating has a high capacity to explain the formation of spherical aggregates in the first meters of displacement. This result suggests that the occurrence of spherical aggregates in natural clayey fault gouges can constitute a new textural evidence for shallow depth pore water phase transition at seismic slip velocity and consequently for past seismic fault sliding.