Control of Fault Weakening on the Structural Styles of Underthrusting‐Dominated Non‐Cohesive Accretionary Wedges
Control of Fault Weakening on the Structural Styles of Underthrusting‐Dominated Non‐Cohesive Accretionary Wedges
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断层弱化对逆冲主导的非粘性增生楔构造样式的控制
DOI：
10.1029/2019jb019220
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Gerbault Muriel
中科院分区：
文献类型：
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作者：
Bauville Arthur;Furuichi Mikito;Gerbault Muriel
下冲推覆作用是挤压边缘推覆体叠加和沉积物俯冲的典型过程。在自然界中，俯冲作用通常与弱基底断层有关，尽管静态力学分析（临界锥理论）表明弱基底断层促进加积，而强基底断层促进俯冲作用。我们进行数学分析和数值模拟，以确定是否永久断层弱化促进或抑制俯冲。我们研究了永久性断层弱化对强基（）非粘性楔形体动力学的控制（以及 分别是内部摩擦和基础摩擦）。我们通过空间恒定的流体超压因子（）控制楔体材料强度，通过塑性应变弱化因子（）控制断层强度。首先，我们使用临界锥度理论来确定预测结构样式的机械模式图。然后，我们进行数值模拟的增生楔形成，以建立其动力学结构特征。我们确定了三个端部构件之间的结构风格的连续体，其对应于理论力学模式转换。样式1的特征是构造薄片和很少或没有俯冲。样式2显示厚切片、推覆体堆叠和浅层重力驱动构造。样式3显示了进入的沉积物的完全下冲，当它们到达后挡时被挖出。我们的结论是，在一个最初强大的楔基底的条件下，永久性断层弱化促进下冲。因此，这一贡献启发的物质性质的动态演化的形成俯冲通道，斜坡不稳定性，和反形式的推覆体堆栈的控制。
Underthrusting is a typical process at compressive margins responsible for nappe stacking and sediment subduction. In nature, underthrusting is often associated with weak basal faults, although static mechanical analysis (critical taper theory) suggests that weak basal faults promote accretion while strong basal faults promote underthrusting. We perform mathematical analyses and numerical simulations to determine whether permanent fault weakening promotes or inhibits underthrusting. We investigate the control of permanent fault weakening on the dynamics of a strong‐based ( ) non‐cohesive wedge ( and are internal and basal friction, respectively). We control the wedge material strength by a spatially constant fluid overpressure factor ( ), and fault strength by a plastic strain weakening factor ( ). First, we use the critical taper theory to determine a mechanical mode diagram that predicts structural styles. Then, we perform numerical simulations of accretionary wedge formation to establish their dynamical structural characteristics. We determine a continuum of structural styles between three end‐members which correspond to the theoretical mechanical mode transitions. Style 1 is characterized by thin tectonic slices and little to no underthrusting. Style 2 shows thick slices, nappe stacking, and shallow gravity‐driven tectonics. Style 3 displays the complete underthrusting of the incoming sediments, that are exhumed when they reach the backstop. We conclude that in the condition of an initially strong wedge base, permanent fault weakening promotes underthrusting. Thus, this contribution enlightens the control of the dynamic evolution of material properties on the formation of subduction channels, slope instabilities, and antiformal nappe stacks.