Mechanics of fore‐arc slivers: Insights from simple analog models
Mechanics of fore‐arc slivers: Insights from simple analog models
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弧前裂片的力学：来自简单模拟模型的见解
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
D. M. Davis
中科院分区：
文献类型：
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作者：
S. Haq;D. M. Davis
具有斜向俯冲的会聚边缘通常包括弧前狭长地带、以海沟为界的上覆板块的一部分和主要的走滑断层系统。长期以来，人们注意到，变形锋附近的相对板块运动，如地震震源机制所示，通常比整体相对板块运动所预期的更接近边缘法线。这是条子运动和前弧内剪切的结果。我们进行了一些简单的计算来确定棉条运动速率应如何随板块会聚倾角而变化。我们发现，结果与流变学有关，但在自然前弧的棉条率的测量是不可能产生真实的洞察物理性质，即使是非常简单的模型，系统太复杂，其关系到流变学是不是唯一的。在简单的桌面实验中，条子运动所占的斜向会聚的比例取决于滑移率和粗糙面的光滑程度。有和没有裂片形成的前缘楔在锥度和应变方式上的相似性表明，对挖出的增生楔的结构观测不太可能让地质学家得出关于楔形成时相对板块运动的相似程度的明确结论，在某些情况下，甚至不可能得出变形时是否存在裂片板块的结论。
Convergent margins with oblique subduction commonly include a fore‐arc sliver, a portion of the overlying plate bounded by the trench and a major strike‐slip fault system. It has long been noted that relative plate motion near the deformation front, as indicated by earthquake focal mechanisms, is generally closer to margin‐normal than would be expected from overall relative plate motion. This results from sliver motion as well as from shear within the fore arc. We carry out some simple calculations to determine how the rate of sliver motion should vary with plate convergence obliquity. We find that the results are related to rheology but that the measurement of sliver rates at natural fore arcs is unlikely to yield real insight into physical properties; even for very simple models; the system is too complicated and its relation to rheology is not unique. The proportion of oblique convergence taken up by sliver motion in simple tabletop experiments depends on the rate of slip and the smoothing of asperities. Similarities in taper and style of strain between frontal wedges forming with and without slivers suggest that structural observations of exhumed accretionary wedges are unlikely to allow geologists to draw definitive conclusions about the degree of obliquity of relative plate motion at the time when the wedges were formed and in some cases not even whether or not a sliver plate was present at the time of deformation.