A model of three-dimensional topographic stresses with implications for bedrock fractures, surface processes, and landscape evolution
A model of three-dimensional topographic stresses with implications for bedrock fractures, surface processes, and landscape evolution
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DOI：
10.1002/2016jf004155
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发表时间：
2017-04-01
影响因子：
3.9
通讯作者：
St Clair, J.
中科院分区：
文献类型：
--
作者：
Moon, S.;Perron, J. T.;St Clair, J.
基岩断裂影响地表过程的速率，驱动景观演变，反过来又受到地形的影响，扰动周围的构造和重力应力场。在这个模拟研究中，我们研究了三维地形和构造应力状态如何影响地球表面下的弹性应力场和基岩断裂模式。我们说明了一般的地形方向和构造应力的大小和各向异性的影响，使用边界元模型的应力下合成细长的脊与不同的纵横比。然后，我们研究了更详细的地形形状的影响，使用自然景观在科罗拉多和南卡罗来纳州。我们表明，应力场是最敏感的地形扰动，如果最压缩的水平构造应力是垂直于长轴的细长地貌，如山脊和山谷，地形应力扰动是最明显的地形下具有较高的平均曲率，如通道路口和山脊波峰。预测的地下富矿带的形状主要取决于地貌相对于最大压缩水平构造应力方向的方向和无量纲比率，该比率表示与水平构造压缩和地形起伏相关的地形应力的相对大小。在这个无量纲比的变化也可以改变潜在的开放模式断裂面的预测方向。我们使用这些模型的结果来说明如何地形扰动的三维构造和重力应力可能会影响景观的演变，通过改变地面过程和地下水流的速率和空间异质性。
Bedrock fractures influence the rates of surface processes that drive landscape evolution and are in turn influenced by landforms that perturb ambient tectonic and gravitational stress fields. In this modeling study, we examine how three-dimensional topography and tectonic stress regimes influence elastic stress fields and bedrock fracture patterns beneath Earth's surface. We illustrate general effects of landform orientation and of tectonic stress magnitude and anisotropy using boundary element models of stresses beneath synthetic elongated ridges with different aspect ratios. We then examine the more detailed effects of landform shape using natural landscapes in Colorado and South Carolina. We show that the stress field is most sensitive to topographic perturbations if the most compressive horizontal tectonic stress is oriented perpendicular to the long axis of elongated landforms such as ridges and valleys and that topographic stress perturbations are most pronounced beneath landforms with higher mean curvatures, such as channel junctions and ridge crests. The shape of a predicted fracture-rich zone in the subsurface depends mainly on the orientation of landforms relative to the most compressive horizontal tectonic stress direction and a dimensionless ratio that expresses the relative magnitudes of topographic stresses associated with horizontal tectonic compression and topographic relief. Variations in this dimensionless ratio can also change the predicted orientations of potential opening-mode fracture planes. We use these model results to illustrate how topographic perturbations of three-dimensional tectonic and gravitational stresses could influence landscape evolution by altering the rates and spatial heterogeneity of surface processes and groundwater flow.