Effect of lithospheric geometry on rift valley relief
Effect of lithospheric geometry on rift valley relief
复制标题
岩石圈几何形状对裂谷地势的影响
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
W. Buck
中科院分区：
文献类型：
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作者：
R. Qin;W. Buck
[1]大陆裂谷和洋中裂谷通常表现为以正断层和隆起的肩为界的裂谷。在本文中，我们数值模拟裂谷地形的演化在一个缺口脆性岩石圈。结果表明，裂谷存在一个最大的山谷起伏，这是由等厚线和岩石圈几何形状之间的竞争所控制的。如果轴向岩石圈比两侧岩石圈薄得多，均衡力将打破轴上向外倾斜的断层，阻止裂谷的加深。我们称之为轴向失效模式。另一方面，如果轴向岩石圈的厚度接近于侧翼的厚度，挠曲弯曲将在侧翼破坏新的断层并阻止山谷加深。我们称之为侧翼失效模式。任一模式的触发给出了最大的谷深，而选择是由等值线和岩石圈几何形状之间的相互作用控制的。在这些机制的基础上，我们提出了一个缩放方程，涉及到的最大谷深的几何形状（侧翼厚度，轴向厚度和切口宽度）和强度（摩擦角和凝聚力）的岩石圈。该模型通过岩石圈轴向厚度的变化解释了洋中脊山谷起伏的轴向变化。
[1] Continental and mid-oceanic rifts commonly show a rift valley bounded by normal faults and uplifted shoulders. In this paper we numerically model the evolution of rift valley relief in a notched brittle lithosphere. Results show that the rift valley has a maximum valley relief, which is controlled by the competition between isostasy and lithospheric geometry. If the axial lithosphere is much thinner than the flanking lithosphere, the isostatic force will break outward dipping faults on the axis and stop the deepening of the rift valley. We call this the axial failure mode. On the other hand, if the thickness of axial lithosphere is close to that of the flanks, flexural bending will break new faults on the flanks and stop the valley deepening. We call this the flanking failure mode. Triggering of either mode gives the maximum valley depth, and the selection is controlled by the interplay between isostasy and lithospheric geometry. On the basis of these mechanisms we propose a scaling equation that relates the maximum valley depth to the geometry (flanking thickness, axial thickness, and notch width) and strength (friction angle and cohesion) of the lithosphere. The model explains along-axis variation of valley relief at mid-oceanic ridges by changes of the axial lithosphere thickness.