Tectono-topographic response of convergent plate margins to changes in submarine margin relief – a combined analysis using analytical and numerical force-balance models

大洋岩石圈在会聚板块边缘的俯冲导致变形和造山，这在数百万年的时间里导致沿板块边界的剪切力和重力之间的平衡。剪切力在上盘引起挤压，并驱动变形和造山作用。相反，边缘起伏，即海沟和上板块最高地形之间的高程差，会导致重力压力梯度，从而产生偏向拉伸并抵消挤压。当剪切力和重力达到平衡时，上平板中的应力最小。然而，力平衡中的扰动会改变上板块中的应力，并驱动变形和地形调整，直到应力再次降至最小。计划中的项目将调查a)海底海脊俯冲和b)从俯冲到大陆碰撞的转变造成的力量平衡扰动如何影响上板块的构造地形发展。在这两种情况下，海沟的深度和海底地形都会减少，这改变了重力和剪切力之间的平衡，促进了变形和造山。为了研究潜艇减边对上板块应力场和地形的影响，我们将解析力平衡计算与二维和三维有限元模拟相结合。该项目包括一项详细的参数研究，以确定决定上平板对力平衡扰动的反应的主要因素。考虑的参数包括绝对起伏变化、大洋板块的倾角以及板块边界和上板块的机械强度。通过使用三维有限元模型，在评估力平衡变化时，将首次考虑斜向俯冲引起的边缘平行应力和变形模式。我们将把我们的模型应用于自然案例研究，包括科科斯海脊(中美洲)、纳斯卡海岭(秘鲁)和Sunda-Banda弧初初碰撞(东南亚)。这种分析力平衡模型和数值力平衡模型的新组合将给出详细和定量的约束，说明海脊或被动大陆边缘俯冲导致的海底边缘起伏变化如何影响上板块的应力场和地形。这一结果将对研究活动大陆边缘和古大陆边缘的应力和变形模式以及重建古地形具有重要意义。最终，该项目将有助于显著提高对地形变化对会聚板块边缘构造地形演化的影响的理解。

The subduction of oceanic lithosphere at convergent plate margins leads to deformation and mountain building, which over millions of years results in an equilibrium between the shear force along the plate boundary and gravitational forces. The shear force causes compression in the upper plate and drives deformation and orogeny. In contrast, the margin relief, i.e. the difference in elevation between the trench and the highest topography in the upper plate, causes a gravitational pressure gradient that creates deviatoric tension and counteracts the compression. When the shear and gravitational forces are in balance, the stresses in the upper plate are minimized. A disturbance in the force balance, however, alters the stresses in the upper plate and drives deformation and topographic adjustments until the stresses are minimized again. The planned project will investigate how disturbances in force balance due to a) the subduction of a submarine ridge and b) the transition from subduction to continental collision affect the tectono-topographic development of the upper plate. In both cases, the depth of the trench and therefore the submarine relief decreases, which alters the balance between gravitational and shear forces and promotes deformation and mountain building. To investigate the effect of a submarine margin-relief reduction on the stress field and topography of the upper plate, we will combine analytical force-balance calculations with 2D and 3D finite element modelling. The project includes a detailed parameter study to identify the main factors that determine the response of the upper plate to perturbations in force balance. The parameters considered include, among others, the absolute relief change, the dip angle of the oceanic plate as well as the mechanical strength of the plate boundary and upper plate. By using 3D finite-element models, margin-parallel stresses and deformation patterns arising from oblique subduction will, for the first time, be taken into account when evaluating the force-balance changes. We will apply our models to natural case studies, including the Cocos Ridge (Central America), the Nazca Ridge (Peru) and the incipient collision at the Sunda-Banda arc (Southeast Asia). The novel combination of analytical and numerical force-balance models will yield detailed and quantitative constraints on how changes in submarine margin relief due to the subduction of a ridge or a passive continental margin affect the stress field and topography in the upper plate. The results will be relevant for investigating stress and deformation patterns at active and fossil continental margins as well as for reconstructions of palaeotopography. Ultimately, the project will contribute to significantly improve the understanding of the effects of relief changes on the tectono-topographic evolution of convergent plate margins.