Surface Wavefield Tomography of the Alpine Region to Constrain Slab Geometries, Lithospheric Deformation and Asthenospheric Flow

高山地区表面波场层析成像以约束板块几何形状、岩石圈变形和软流圈流动

• 批准号: 363550787
• 负责人: Professor Dr. Jörg Ebbing
• 金额: --
• 依托单位: Institut für Geowissenschaften
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/363550787?language=en
• 关键词: Surface; Wavefield; Tomography; Alpine; Region

Surface waves are ideally suited to constrain isotropic and anisotropic elastic properties of the lithosphere and asthenosphere. The Alpine region is characterized by relatively small-scale structural variations. To answer key questions regarding its lithospheric dynamics requires particularly high imaging resolution. Such resolution can be provided by the wavefield tomography, able to extract highly complete structural information from data recorded by a large-aperture, dense array. Recordings of the AlpArray Seismic Network, including its marine part, and of the Swaths C and D (AF A, B, C, D) will be analyzed to image both the local propagation of teleseismic Rayleigh and Love waves and crustal and mantle structure, with a lateral resolution below 50 km. The resulting shear-wave velocity model for the Earths upper 300 km will image the subducting Adriatic and Eurasian mantle lithospheres, as well as the forelands. It will resolve the slab geometry in the regions of polarity switches (SW Alps to Apennines, western to eastern Alps), of slab gaps (central Alps), of slab break-off (SW Alps), and in the transition from the eastern Alps towards the Dinarides (RT1, Reorg. of Lithosphere). Conversion into density anomalies will enable us to estimate slab-pull and buoyancy forces in the Alpine region and quantify the contribution of endogenous forces to surface uplift and subsidence (RT2, Surface Response). Seismic anisotropy reveals imprints of recent and past deformation on the lithosphere as well as mantle flow in the asthenosphere. We will compute a 3D model of seismic anisotropy within the lithosphere and the asthenosphere, offering new evidence on the deformation of the crust and on the coupling/decoupling between the curst and mantle and between plate motion and mantle flow (RT3, Deform. of Crust + Mantle). It will further serve as observational evidence to evaluate predictions by numerical modelling for different evolution scenarios (RT1, Reorg. of Lithosphere).New method development will focus on the measurement of Rayleigh and Love phases and amplitudes and their use in the imaging of the curvature, amplitude variations, and direcionality of the wavefields and of the seismic velocity structure beneath the arrays footprint. In order to cope with the large amount of recordings, automated measurement methods will be developed. Helmholtz and eikonal tomography will be extended to the anisotropic case. Phase velocity maps will be inverted for a radially and azimuthally anisotropic shear-wave velocity model of the Alpine region embedded into regional models and constrained by a-priori knowledge on the crust. Tools for efficient numerical forward modelling of the interaction of teleseismic surface waves with the deep structure of the Alps based on discontinuous Galerkin methods will be developed. The methods will allow the imaging of the Alps and their forelands that is both high-resolution and whole-region-scale.

表面波非常适合约束岩石圈和软流圈的各向同性和各向异性弹性特性。高山地区的特点是相对较小的结构变化。要回答有关其岩石圈动力学的关键问题，需要特别高的成像分辨率。波场层析成像可以提供这样的分辨率，它能够从大孔径、密集阵列记录的数据中提取高度完整的结构信息。将分析AlpArray地震台网的记录，包括其海洋部分，以及C和D （AF A， B， C， D）的记录，以成像远震瑞利波和洛夫波的局部传播以及地壳和地幔结构，横向分辨率低于50公里。由此产生的地球300公里以上的横波速度模型将描绘俯冲的亚得里亚海和欧亚地幔岩石圈，以及前陆。它将在极性转换区域（西南阿尔卑斯山脉到亚平宁山脉，西阿尔卑斯山脉到东阿尔卑斯山脉）、板块间隙区域（中部阿尔卑斯山脉）、板块断裂区域（西南阿尔卑斯山脉）以及从东阿尔卑斯山脉到迪纳里德山脉的过渡区域（RT1, Reorg）解决板块几何问题。岩石圈)。转换成密度异常将使我们能够估计高山地区的板拉力和浮力，并量化内力对地表隆起和下沉的贡献（RT2, surface Response）。地震各向异性揭示了岩石圈最近和过去的变形印记以及软流圈的地幔流动。我们将计算岩石圈和软流圈内地震各向异性的三维模型，为地壳变形、地壳与地幔之间的耦合/解耦以及板块运动与地幔流动之间的耦合/解耦提供新的证据(RT3, Deform。地壳+地幔)。它将进一步作为观测证据，以评估不同进化情景的数值模拟预测（RT1, Reorg）。岩石圈)。新方法的开发将集中在瑞利和洛夫相位和振幅的测量，以及它们在成像中的应用，曲率、振幅变化、波场的方向性以及阵列足迹下的地震速度结构。为了处理大量的记录，自动化测量方法将得到发展。亥姆霍兹层析成像将扩展到各向异性的情况。将高寒地区径向和方位各向异性横波速度模型嵌入到区域模型中，并受地壳先验知识的约束，进行相速度图的反演。将开发基于不连续伽辽金方法的远震表面波与阿尔卑斯山脉深部结构相互作用的有效数值正演模拟工具。这些方法将使阿尔卑斯山及其前陆的成像既具有高分辨率，又具有整个区域的尺度。