Effect of increased shear stress along a plate boundary fault on the formation of an out-of-sequence thrust and a break in surface slope within an accretionary wedge, based on numerical simulations
Effect of increased shear stress along a plate boundary fault on the formation of an out-of-sequence thrust and a break in surface slope within an accretionary wedge, based on numerical simulations
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DOI：
10.1016/j.tecto.2009.08.037
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发表时间：
2010-03
期刊：
影响因子：
2.9
通讯作者：
A. Miyakawa;Yasuhiro Yamada;T. Matsuoka
中科院分区：
文献类型：
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作者：
A. Miyakawa;Yasuhiro Yamada;T. Matsuoka
我们研究了增加剪切应力对增生楔体结构的影响，剪切应力描述了由于材料摩擦力增加或孔隙压力降低而产生的沿滑脱层沿着的摩擦滑动阻力。为了阐明这种效应的本质，我们使用两种模型进行了数值模拟：稳定摩擦模型和增加摩擦模型。稳定摩擦力模型产生了一个低角度、平滑的表面斜坡和一个顺冲断层，而增加摩擦力模型产生了一个表面斜坡（陡坎）的中断和一个切穿逆冲断层席的逆冲断层（OST）。OST的形成是通过两个相邻冲断层的连接段，它的形成导致了楔体增厚模式的变化，从逆冲断层片旋转和背冲活动的底侵。向陆高摩擦带和向海低摩擦带之间增厚模式的这种对比导致形成明显的斜坡突变，因为向陆带比向海带更陡，与临界锥度理论一致。基底岩片或海山的俯冲可产生类似的结构，这是由于基底剪切滑动的阻力增加。然而，由于剪切滑动阻力增加，增生楔中出现的独特结构包括平坦的基面和OST下方没有斜坡破坏沉积物。这些构造特征在日本室户外海的南海海槽、巽他海峡和巴巴多斯海脊的增生楔中得到了观察。
We investigated the effect on accretionary wedge structure of increased shear stress, which describes the frictional sliding resistance along a decollement arising from an increase in material friction or reduction in pore pressure. To clarify the nature of the effect, we performed numerical simulations using two models: a Stable Friction model and an Increased Friction model. The Stable Friction model produced a low-angle, smooth, surface slope and an in-sequence thrust, whereas the Increased Friction model produced a break in surface slope (scarp) and an out-of-sequence thrust (OST) that cuts through the thrust sheet. The OST formed via the connection of segments of two adjacent thrusts, and its formation resulted in a change in the thickening mode of the wedge from thrust-sheet rotation and back-thrust activity to underplating. This contrast in thickening mode between the landward high-friction zone and seaward low-friction zone resulted in the formation of a clear break in slope, as the landward zone is steeper than the seaward zone, consistent with critical taper theory. The subduction of a basement slice or seamount can produce similar structures arising from an increase in resistance to basal shear sliding. However the distinctive structures arising in an accretionary wedge as a result of increased shear sliding resistance include a flat basal plane and absence of slope-failure sediments beneath the OST. These structural features are observed in accretionary wedges of the Nankai Trough off Muroto (Japan), the Sunda Strait, and the Barbados Ridge.