Recognizing seamount-forearc collisions at accretionary margins: Insights from discrete numerical simulations
Recognizing seamount-forearc collisions at accretionary margins: Insights from discrete numerical simulations
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DOI：
10.1130/g38923.1
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发表时间：
2017-07
期刊：
影响因子：
5.8
通讯作者：
J. Morgan;N. Bangs
中科院分区：
文献类型：
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作者：
J. Morgan;N. Bangs
我们进行了离散的数值模拟，以研究海山碰撞的影响与前弧沿着积极增生的俯冲边缘。海山相互作用模型在覆盖前弧中留下了独特的结构，与非增生边缘的结构不同。平面滑脱层上方的加积作用产生了位移均匀的间隔均匀的逆冲断层，而海山则激活了一个或多个大偏移展布断层，可容纳大量偏移。海山上方形成局部过陡的斜坡，但与非增生边缘相比，陡坡是短暂的。通过海山后的重新加积使平衡表面坡度得以恢复。海山还保护了其尾流中的侵入地层，推迟了新逆冲断层的形成，并增加了断层间距。加积地层中的软弱层位使滑脱层逐步上升到海山之上，进一步保护了更深的地层，并垂直分割楔形变形。值得注意的是，所有模拟故障形成序列，在非增生边缘发现的序列外故障。在许多增生边缘，包括南海（日本近海）发现的类似结构表明，我们可能低估了海山相互作用在许多地方的作用，影响我们在这些环境中的俯冲危险的评估。
We conducted discrete numerical simulations to examine the effects of seamount collisions with forearcs along actively accreting subduction margins. Modeled seamount interactions leave behind distinctive structures in overriding forearcs that differ from those found at non-accreting margins. Whereas accretion above a planar decollement produces evenly spaced thrust faults with uniform displacements, seamounts activate one or more large-offset splay faults that accommodate substantial offset. Locally oversteepened slopes develop above the seamounts, but in contrast to non-accreting margins, the steep slopes are transient. Renewed accretion following seamount passage allows the equilibrium surface slopes to recover. Seamounts also protect incoming strata in their wake, delaying formation of new thrust faults and increasing fault spacing. Weak horizons within accreting strata allow the decollement to step up above the seamount, further protecting deeper strata and vertically partitioning wedge deformation. Notably, all modeled faults form in sequence, in contrast to out-of-sequence faults found at non-accreting margins. Similar structures found at many accretionary margins, including Nankai (offshore Japan), suggest that we may underestimate the role of seamount interactions in many locations, with implications for our assessment of subduction hazards in these settings.