Linking the deep structure to surface deformation: Body wave tomography of the Ligurian Sea and South-Western Alps

将深层结构与地表变形联系起来：利古里亚海和西南阿尔卑斯山的体波断层扫描

• 批准号: 442653120
• 负责人: Professorin Dr. Eline Le Breton
• 金额: --
• 依托单位: GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/442653120?language=en
• 关键词: Linking; deep; structure; surface; deformation

The Alpine orogenic belt, which represents the scientific focus of the priority programme 4D-MB, is characterized by its highly complex tectonic nature resulting from the interaction of oceanic and continental lithosphere between the converging European and African plates. The Ligurian Basin is a back-arc basin generated by the southeastward trench retreat of the Apennines-Calabria-Maghrebides subduction zone, which also triggered the opening of the adjacent western Mediterranean basins. The Ligurian Sea is also a key location due to its complex geodynamic setting characterized by pronounced variations in crustal nature and thickness. In particular, in the center of the basin, the nature of crust and mantle is still debated. The proposed project will specifically harvest the rich data set of the marine component of AlpArray (LOBSTER) to extract a maximum of information from the OBS data. The 23 LOBSTER OBS comprises the offshore component of the AlpArray seismic network to define subsurface structures at the transition from the Western Alps to the Apennines and to improve our understanding of the 3D-geometry of the system and its kinematics. We will use body waves from primary and secondary arrivals (P, S, Pn, Sn) from OBS and AlpArray permanent and temporary stations to invert for velocity models of the Ligurian Sea and surrounding. The arrival times used onset will be from the following sources a.) airgun shots registered on the LOBSTER and landstations. b.) from local seismicity during the deployment of the LOBSTER stations and c.) from arrivals listed in the ISC catalog since the year 2000. Using velocities from the three-dimensional velocity structure will allow extracting information of the distribution and nature of the structural units, in particular for the units continental crust, hyper-extended continental crust, serpentinized mantle, and oceanic crust. Shear wave arrivals and models will contribute to the degree of serpentinization (i.e. ‘hydration’) of mantle rocks. Waves travelling just below the crust-mantle boundary (MOHO) allow determining the velocity of the uppermost mantle and yield information on the thermal and tectonic history of the upper mantle. These waves (refracted waves) allow inverting for transverse anisotropy for the uppermost mantle. We hypothesize that stretching of the crust should have modified the mantle flow and hence the fast polarization directions provide information on the width of the extensional zone at depths below the MOHO. The obtained results from the velocity models will be interpreted in relation to gravity data, sediment information, and geomorphology. In the last year of the project balancing techniques, we will quantify the amount of continental extension along those profiles using modeling techniques. Timing of extension can be constrained with the age of syn- and post-rift sediments.

阿尔卑斯造山带是优先方案4D-MB的科学重点，其特点是构造性质非常复杂，这是欧洲和非洲板块汇合处的海洋和大陆岩石圈相互作用的结果。 利古里亚盆地是亚平宁-卡拉布里亚-马格里布俯冲带向东南方向的海沟后退所形成的弧后盆地，这也引发了邻近的西地中海盆地的打开。利古里亚海也是一个关键地点，因为其复杂的地球动力学背景，其特点是地壳性质和厚度变化明显。特别是在盆地的中心，壳幔的性质仍有争议。 拟议的项目将专门收集AlpArray（LOBSTER）海洋部分的丰富数据集，以从OBS数据中提取最大限度的信息。23 LOBSTER OBS包括AlpArray地震网络的海上组件，用于确定从西阿尔卑斯山到亚平宁山脉过渡处的地下结构，并提高我们对系统三维几何形状及其运动学的理解。 我们将使用来自OBS和AlpArray永久和临时台站的一次和二次到达（P、S、Pn、Sn）的体波来反演利古里亚海及周边地区的速度模型。开始使用的到达时间将来自以下来源a.）在龙虾和陆地上登记的气枪射击。B.）LOBSTER台站部署期间当地地震活动的影响，以及c.）从2000年以来ISC目录中列出的到达者。 使用来自三维速度结构的速度将允许提取结构单元的分布和性质的信息，特别是对于大陆地壳、超伸展大陆地壳、蛇纹化地幔和大洋地壳单元。横波波至和模式将有助于地幔岩石的蛇纹化（即“水化”）程度。 在壳幔边界（MOHO）下方传播的波可以确定上地幔的速度，并提供上地幔热历史和构造历史的信息。这些波（折射波）允许反演最上层地幔的横向各向异性。我们假设，地壳的拉伸应修改地幔流，因此快速极化方向提供的信息，在深度低于MOHO的伸展带的宽度。 从速度模型中获得的结果将结合重力数据、沉积物信息和地貌进行解释。在平衡技术项目的最后一年，我们将使用建模技术量化沿着这些剖面的大陆延伸量。伸展的时间可以受到同裂谷期和裂谷期后沉积物年龄的限制。