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

高山造山带是优先方案4D-MB的科学重点，其特点是其高度复杂的构造性质，是由交汇的欧洲和非洲板块之间的海洋和大陆岩石圈相互作用造成的。利古里亚盆地是亚平宁-卡拉布里亚-马格里布德斯俯冲带东南向海沟后撤所形成的弧后盆地，该俯冲带也引发了邻近西地中海盆地的打开。由于其复杂的地球动力学背景，地壳性质和厚度的显著变化，利古里亚海也是一个关键的位置。特别是在盆地中心，地壳和地幔的性质仍然存在争议。拟议的项目将具体收集AlpArray （LOBSTER）海洋成分的丰富数据集，以从OBS数据中提取最大限度的信息。23 LOBSTER OBS包括AlpArray地震网络的海上组成部分，用于定义从西阿尔卑斯山到亚平宁山脉过渡的地下结构，并提高我们对系统3d几何形状及其运动学的理解。我们将使用来自OBS和AlpArray永久和临时站点的主要和次要到达的体波（P， S, Pn, Sn）来反演利古里亚海及其周围的速度模型。开始使用的到达时间将来自以下来源a.)在龙虾和陆地站点上登记的气枪射击。b.)龙虾台站部署期间的当地地震活动，c.) 2000年以来ISC目录中列出的到达的地震。利用三维速度结构的速度可以提取构造单元的分布和性质信息，特别是大陆地壳、超伸展大陆地壳、蛇纹石化地幔和海洋地壳单元。横波到达和模式将有助于地幔岩石的蛇纹石化程度（即“水化”）。在地壳-地幔边界（MOHO）下方传播的波可以确定最上层地幔的速度，并提供有关上地幔的热和构造历史的信息。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该改变了地幔流动，因此快速极化方向提供了MOHO以下深处伸展带宽度的信息。从速度模型获得的结果将与重力数据、沉积物信息和地貌进行解释。在项目平衡技术的最后一年，我们将使用建模技术量化沿着这些剖面的大陆延伸量。伸展的时间可受合裂谷和后裂谷沉积年龄的限制。

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.