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

阿尔卑斯山造山带是优先方案4D-MB的科学重点，其特点是高度复杂的构造性质，这是由于汇聚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-马格里比季斯俯冲带向东南海沟撤退形成的弧后盆地，也触发了邻近的西地中海盆地的开放。利古里亚海也是一个关键地点，因为其复杂的地球动力学环境以地壳性质和厚度的显着变化为特征。特别是，在盆地中心，地壳和地幔的性质仍然存在争议。拟议的项目将专门收获AlpArray(龙虾)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龙虾OBS是阿尔卑斯山地震台网的近海部分，用于确定从西部阿尔卑斯山向亚平宁山脉过渡时的地下构造，并提高我们对该系统的三维几何形状及其运动学的理解。我们将使用来自OBS和AlpArrow永久和临时站点的一次和二次到达(P、S、Pn、Sn值)的体波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)龙虾站和登陆站都有气枪射击记录。B.)龙虾站部署期间的当地地震活动和c.)来自ISC目录中自2000年以来的入境旅客。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、蛇纹岩地幔和洋壳单元。剪切波的到达和模型将有助于地幔岩石的蛇纹岩化(即‘水化’)程度。在地壳-地幔边界(MOHO)下方传播的波可以确定最上地幔的速度，并提供关于上地幔的热历史和构造历史的信息。这些波(折射波)允许对最上地幔的横向各向异性进行反演。我们假设，地壳的伸展应该改变了地幔流动，因此快速极化方向提供了关于莫霍面以下深处伸展带宽度的信息。从速度模型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来量化沿这些剖面的大陆延伸量。伸展的时间受同裂谷沉积和裂谷后沉积时代的制约。

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.