Collaborative Research: Rivers, Faults, and Growing Mountains: Dynamic Feedback between Crustal Deformation, Rock Strength, and Erosion

大多数活跃山脉的地形显示出变形和侵蚀之间的清晰联系，其形式是与断层和剪切带紧密相连的山谷网。我们认为这种联系是变形、岩石破坏和地表侵蚀之间动态反馈的标志，这种反馈在造山带演化中起着根本作用。通过这个研究项目，我们将验证我们的假设，即与构造驱动的地震相关的岩石破碎降低了地球上地壳的强度和颗粒大小，在物质表面产生更容易被河流、山体滑坡和冰川侵蚀的区域。沿着这些弱断层带的侵蚀比未变形的物质进行得更快，因此，变形历史被记录在地形结构中。这些断裂弱化带的三维方向在很大程度上是由与地幔对流有关的大规模板块构造决定的。因此，如果我们的假设成立，那么我们将能够利用地表特征（山谷和山脊）的方向以相对高的分辨率描述地幔对流的长期历史。为了验证这一假设，我们提出了一个将先进的数值模拟与新西兰南阿尔卑斯山的现场数据收集相结合的程序，以评估两个可测试的预测：(1)地形与岩石强度之间应该存在相关性，反映在体积黏聚、断裂密度、摩擦系数、抗拉强度和粒度等属性上；(2)基于我们目前对相关物理的理解，三维变形和侵蚀的耦合模型应该产生地形、侵蚀和应变的模式，这些模式既与观测结果一致，又与均匀岩石强度的情况有很大不同。我们预计，这项研究将为研究从地幔对流到单个流域盆地的地表和构造过程相互依存关系的科学家提供关键信息。作为与该项目相关的外展活动的一部分，我们将制作并测试一个可在网上访问的景观建模模块，该模块将允许k12和普通观众在一个简化的、耦合的地貌/构造造山带系统中进行景观发展的数值实验。该项目得到了地貌学和土地利用动力学项目和构造学项目的支持。此外，该奖项被指定为OIIA/ISE全球风险基金奖，由美国国家科学基金会OIIA国际科学与工程部门共同资助。

The topography of most active mountain ranges shows a clear link between deformation and erosion in the form of valley networks that align closely with faults and shear zones. We propose that this association is the signature of dynamic feedback between deformation, rock damage, and surface erosion, and that this feedback plays a fundamental role in the evolution of orogens. With this research program, we will test our hypothesis that the rock crushing associated with tectonically-driven earthquakes reduces the strength and grain size of the upper crust of the Earth, producing zones at the surface of material that is more readily eroded by rivers, landslides and glaciers. Erosion along these weakened fault zones proceeds more rapidly than the non-deformed material, and consequently, the deformation history is recorded within the topographic fabric. The 3D orientation of these fault-weakened zones is largely determined by large scale plate tectonics related to mantle convection. Consequently, if our hypothesis is sustained, then we will be able to use the orientation of surface features (valleys and ridges) to describe the long term history of mantle convection at relatively high resolution.To test this hypothesis, we propose a program that combines advanced numerical modeling and field data collection in the Southern Alps of New Zealand to evaluate two testable predictions: (1) that there should exist a correlation between topography and rock strength, as reflected in properties such as bulk cohesion, fracture density, friction coefficient, tensile strength and grain size; and (2) that a coupled model of 3D deformation and erosion, based on our current understanding of the relevant physics, should produce patterns of topography, erosion, and strain that are both consistent with observations and substantially different from the case of uniform rock strength. We anticipate that this research will provide critical information for scientists working on the interdependence of surface and tectonic processes at scales ranging from those of mantle convection to those of individual drainage basins. As part of the outreach associated with this program, we will produce and test a Web-accessible landscape modeling module that will permit numerical experimentation by k12 and general audiences of landscape development in a simplified, coupled geomorphic/tectonic orogenic system.This project is supported by the Geomorphology and Land-use Dynamics program and the Tectonics program. In addition, this award is designated as an OIIA/ISE Global Venture Fund Award and is being co-funded by NSF's OIIA International Science and Engineering Section.