Mechanical Anisotropy from Gravity/Topography Coherence: A Global Study

尽管进行了几十年的地球物理和地质研究，但大陆构造、力学行为和长期演化的一级方面仍然是个谜。地球大陆岩石圈在力学上是各向异性的吗？越来越多的证据表明，重力异常通过一种方向各向异性的弹性响应反映了地形表面和界面载荷的影响。科学家们正在研究岩石圈中力学各向异性的原因，试图确定它是某些克拉通的特征还是一种更普遍的现象。他们结合力学和地震特征来定义岩石圈。具体来说，他们通过比较定向可变机械强度的新测量结果与已发表的地震各向异性模型，或者通过将地震各向异性与大地测量观测和活动变形的地球动力学模型进行比较，来量化化石应变的控制。地震各向异性与力学各向异性相关性的深度依赖性是构造作用下岩石圈整体变形深度的诊断。力学各向异性是根据重力异常与地形的二维相干性的空间依赖性来估计的。为此，科学家们正在开发一种多锥度相干分析方法，该方法使用对单个地质单元及更大尺度结构敏感的数据窗口。该研究结合了地质、地球动力学、构造和地震学信息，得出了大陆岩石圈的综合特征。正在开发的方法也适用于海洋和行星岩石圈的研究。这项研究跨越了地球科学的传统界限，应用数学来开发专用的光谱分析方法，以及统计学来基于查询的建模不确定性评估。最终的副产品是一个高质量的区域大陆重力、地形和地质数据数据库，以及一套公开可用的建模软件。

Despite decades of geophysical and geological research, first-order aspects of continental structure, mechanical behavior, and long-term evolution have remained enigmatic. Is Earth's continental lithosphere mechanically anisotropic? Evidence is emerging that gravity anomalies reflect the influence of topographic surface and interface loading via an elastic response that is azimuthally anisotropic. Scientists are investigating the cause of mechanical anisotropy in the lithosphere in an attempt to establish if it is characteristic for certain cratons or a more general phenomenon.They combine mechanical and seismic characterizations to define the lithosphere. Specifically, they are quantifying the control of fossil strain by comparing new measurements of directionally variable mechanical strength with published models of seismic anisotropy, and by alternatively comparing seismic anisotropy with geodetic observations and geodynamic models of active deformation. The depth dependence of the correlation between seismic and mechanical anisotropy is the diagnostic that constrains the depth to which the lithosphere has deformed as one unit under the action of tectonic processes. Mechanical anisotropy is estimated from the spatial dependence of the two-dimensional coherence between gravity anomalies and topography. For this, the scientists are developing a multitaper coherence analysis method that uses data windows sensitive to structure on the scale of individual geological units and beyond.The research combines geological,geodynamical, tectonic, and seismological information to arrive at an integrative characterization of the continental lithosphere. The methods being developed are also suitable for the study of oceanic and planetary lithospheres. The research crosses traditional boundaries of the Earth sciences, to applied mathematics for the development of dedicated spectral analysis methods, and to statistics for a query-based assessment of modeling uncertainties. A final by-product is a high-quality data base of regional continental gravity, topography, and geological data and a suite of publicly available modeling software.