Deformation patterns in relation to the deep configuration of the lithosphere of the Alps and their forelands – DEFORM

由于观测到的地表形变和地震活动的变化，阿尔卑斯山及其前缘的今天的物理状态仍然是一个有争议的问题。由于我们对岩石圈内部结构与现今应力场的关系的了解有限，这导致了一级机制主导着现代过程的相互矛盾的解释。特别是，地壳浅层区域如何与较深的地壳水平和地幔耦合或脱钩的问题是悬而未决的。SPP第一阶段的结果证实了岩石圈的内部结构具有从造山带到前陆岩性的强烈的横向和垂直变化，密度和地震速度的分布表明了这一变化。这种物理性质的变化还导致了高度可变的热场和不均匀的流变带。DEFORM的主要目的是检验这样一个假设，即如果将岩石圈结构的一阶特征与物理过程结合起来，控制现代变形的不同过程可以被分离出来，并量化它们的相对贡献。为了验证这一假设，我们的目标是定量评估数据得出的内部岩石圈结构如何一方面响应板块边界力，另一方面响应冰川旋回的垂直加载或卸载。在我们的项目中，结合SPP一期的运行，我们发现地壳密度对比与大地测量的现代形变矢量以及大地震事件的分布之间存在着很强的正相关关系。为了评估观测到的变形分布和岩石圈的流变结构之间是否存在系统和跨尺度的关系，我们将使用最新的流变模型作为模拟热力耦合过程的基础。因此，我们建议将地质时间尺度上大变形的热力学模型与区域热力学方法联系起来，这种方法可以解决人类时间尺度问题，并以一致的方式解释控制岩石圈整体行为的不同变形机制之间的多物理耦合。在模拟中，将静态流变模型和热模型作为初始条件，将地表现今变形场作为上边界条件，将由大尺度动力学模型得到的最上面软流圈的变形场作为下边界条件。该项目有助于目前征求建议书的主题2：地表和地壳对不同时间尺度上山脉结构变化的反应。它链接到SPP中的许多其他合作伙伴，以确保将新结果整合到流变模型中，并验证模拟预测。

The present-day physical state of the Alps and their forelands is still a matter of debate due to observed variations of surface deformation and seismicity. Due to our limited knowledge of the internal structure of the lithosphere in relation to the present-day stress field, this leads to contradictory interpretations on which first order mechanisms are dominantly controlling present-day processes. In particular, the question of how the shallow domains of the crust are coupled or decoupled from deeper crustal levels and the mantle, is open. Results obtained in phase I of the SPP confirm that the internal structure of the lithosphere is characterized by a strong lateral and vertical variation in lithology from the orogen to the forelands indicated by the distribution of densities and seismic velocities. This variation in physical properties also results in a highly variable thermal field and a heterogeneous rheological zonation. The main objective of DEFORM is to test the hypothesis that different processes controlling recent deformation can be isolated and their relative contributions quantified if first-order characteristics of lithosphere configuration are considered together with physical processes. To test this hypothesis we aim to quantitatively assess how the data-derived internal lithospheric configuration deforms in response to plate boundary forces on the one hand and vertical loading or unloading over a glacial cycle on the other. In our project INTEGRATE running in phase I of the SPP we find a strong positive correlation between crustal density contrasts and present day deformation vectors from geodetic measurements as well as the distribution of large seismic events. To evaluate if there is a systematic and across scales relationship between the distribution of observed deformation and the rheological configuration of the lithosphere, we will use an updated rheological model as a base for simulations of coupled thermo-mechanical processes. Therefore, we propose to link thermomechanical models of large-scale deformation on geological timescales with regional thermomechanical approaches that can resolve the human time scale and account in a consistent way for the multi-physics coupling among the different deformation mechanisms controlling the bulk behavior of the lithosphere. In the simulations, the static rheological and thermal models are considered as initial conditions, the present-day deformation field at the surface as upper boundary condition and the deformation field of the uppermost asthenosphere derived from large-scale dynamic models will be extracted as lower boundary condition. The project contributes to Theme 2 of the current call for proposals: Surface and crustal responses to changes in mountain structure on different time scales. It links to many other partners in the SPP to ensure the integration of new results in the rheological model and to validate the simulation predictions.