Mechanical Anisotropy from Gravity/Topography Coherence: A Global Study

尽管地球物理学和地质学研究了几十年，大陆结构、力学行为和长期演化的一阶方面仍然是个谜。地球的大陆岩石圈是各向异性的吗？有证据表明，重力异常通过方位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，试图确定它是某些岩石圈的特征还是一种更普遍的现象。他们将联合收割机的力学和地震特征结合起来定义岩石圈。具体而言，他们通过将方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进行比较，并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。 地震各向异性和力学各向异性之间的相关性的深度依赖性是限制岩石圈作为一个单元在构造过程作用下变形的深度的诊断。力学各向异性估计重力异常和地形之间的二维相干性的空间依赖性。为此，科学家们正在开发一种多锥相干分析方法，该方法使用对单个地质单元及更大尺度上的结构敏感的数据窗口。该研究结合了地质学、地球动力学、构造学和地震学信息，以综合表征大陆岩石圈。正在开发的方法也适用于海洋和行星岩石圈的研究。该研究跨越了地球科学的传统界限，应用数学开发专用的光谱分析方法，并对基于查询的建模不确定性评估进行统计。最后的副产品是一个高质量的区域大陆重力，地形和地质数据的数据库和一套公开的建模软件。

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.