Underthrusting‐accretion cycle: Work budget as revealed by the boundary element method
Underthrusting‐accretion cycle: Work budget as revealed by the boundary element method
复制标题
冲积循环：边界元法揭示的工作预算
DOI：
10.1029/2007jb004997
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发表时间：
2007
影响因子：
--
通讯作者：
M. Cooke
中科院分区：
文献类型：
--
作者：
M. D. Castello;M. Cooke
[1]增生楔的砂箱模型表明，断层系统通过交替楔增厚和楔延长的循环周期性地增长，楔增厚是由楔内断层的沿着滑动（俯冲）和楔延长调节的，楔延长是由楔趾处新断层的增长调节的（增生）。这两种变形模式之间的转换受重力做功、摩擦热、断层周围变形功、断层传播功和地震/声能的相互作用控制。使用数值力学模型的基础上的边界元法，我们模拟了在沙箱实验中观察到的变形，提供了一个力学分析的俯冲/增生过渡。我们的研究结果表明，在俯冲阶段的收缩楔所做的总工作增加到一个临界值时，一个新的正面推力的传播显着减少进一步变形所需的工作。数值模型还预测了最大剪切力沿着基底滑脱在俯冲过程中的位置，以及一个新的推力的成核的积极最可行的位置和聚散度。这些位置并不一致，并且与实验结果相匹配的能量最有利的位置表明，新的逆冲斜坡首先向前发展，然后向下和向后连接到传播的基底滑脱。产生新的推力斜坡的剪切局部化将发生在变形楔所消耗的能量由于重力、摩擦、内部和传播功项的最佳组合而最小化的地方。
[1] Sandbox models of accretionary wedges have demonstrated that fault systems grow episodically via cycles of alternating wedge thickening, which is accommodated by slip along faults within the wedge (underthrusting), and wedge lengthening, which is accommodated by growth of new faults at the wedge toe (accretion). The transition between these two modes of deformation is controlled by the interplay of work against gravity, frictional heating, the work of deformation around faults, and the work of fault propagation and seismic/acoustic energy. Using numerical mechanical models based on the boundary element method, we have simulated the deformation observed in sandbox experiments, providing a mechanical analysis of the underthrusting/accretion transition. Our results show that the total work done by the contracting wedge increases during the underthrusting stage up to a critical value when the propagation of a new frontal thrust significantly reduces the work required for further deformation. The numerical models also predict the location of the maximum shear along the basal decollement during underthrusting as well as the energetically most viable position and vergence for the nucleation of a new thrust. These locations do not coincide, and the match of the energetically most favorable position with the experimental results suggests that the new thrust ramps develop first ahead and then link down and backward to the propagating basal decollement. The shear localization producing a new thrust ramp will occur where the energy spent by the deforming wedge is minimized due to an optimal combination of gravitational, frictional, internal, and propagation work terms.