Collaborative Research: Mapping Upper-Mantle Anisotropy in Western U.S.: Constraints on Crust-Mantle Coupling

0545777 Gaherty地球镜计划的一个主要目标是更好地了解控制大陆组装和演化的过程。 这些过程中有许多可能与上地幔结构和动力学有关-例如，地幔浮力变化驱动地表变形。 由此产生的构造作用的性质不仅取决于浮力的性质，而且取决于传递浮力的地壳和地幔岩石圈的强度。 地幔岩石组构产生的地震各向异性提供了一种绘制地幔变形图的手段，地质学和大地测量观测提供了地表变形的图像。 利用数值模型将两者联合收割机结合起来，科学家们可以推导出地幔流动、岩石圈强度和控制地表变形机制的新约束。 在这个项目中，一个综合的地震-地球动力学分析正在开发和应用于几个关键问题之间的耦合地幔流动和地壳变形在美国西部，包括：（1）地幔组构的变化沿着圣安德烈亚斯断层在加州可以解释的地壳和/或地幔的强度从北到南的变化？ (2)复杂的地幔组构推断中央盆地和山脉的地幔流周围增厚的岩石圈，或者它更暗示浮力驱动的上升流在这个地区？具体来说，地震学家正在测量有限频率的旅行时间从地震波记录在USAray和现有的宽带地震台站，并反演这些旅行时间的三维上地幔模型中，地幔结构是限制使用现实的敏感性内核一般各向异性结构。 与此同时，地球动力学家正在开发区域数值流动模型，这些模型来自地质约束和地表运动学观测。运动学流动模型提供了各种变形情况下的地幔组构发展的估计，这些组构的估计，然后定量评估与地震观测的兼容性。 除了限制地幔流和地壳变形之间的耦合沿着美国西部板块边界，该项目将提供一个通用的方法，区域尺度的各向异性建模的大陆。

0545777GahertyA principal goal of the EarthScope program is to develop a better understanding of the processes that control the assembly and evolution of the continents. It is likely that many of these processes are associated with upper-mantle structure and dynamics -- mantle buoyancy variations drive surface deformation, for example. The character of the resulting tectonism is dependent not only on the nature of the buoyancy forces, but also on the strength of the crust and mantle lithosphere that transmit those forces. Seismic anisotropy produced by fabric in mantle rocks provides a means to map deformation in the mantle, and geology and geodetic observations provide a picture of surface deformation. Using numerical models to combine the two, scientists can derive new constraints on mantle flow, lithospheric strength, and the mechanisms that control surface deformation. In this project, an integrated seismic-geodynamic analysis is being developed and applied to several key questions regarding the coupling between mantle flow and crustal deformation in the western US, including: (1) Can variations in mantle fabric along the San Andreas Fault in California be explained by changes in the strength of the crust and/or mantle from north to south? (2) Is complex mantle fabric inferred beneath the central Basin and Range produced by mantle flow around a thickened lithosphere, or is it more suggestive of buoyancy-driven upwelling beneath this region? Specifically, seismologists are measuring finite-frequency travel-times from seismic waves recorded at USArray and existing broad-band seismic stations, and inverting these travel-times for 3-D upper-mantle models in which mantle fabric is constrained using realistic sensitivity kernels for generally anisotropic structure. Simultaneously, geodynamicists are developing regional numerical flow models that are derived from geological constraints and observations of surface kinematics. The kinematic flow models provide estimates of mantle fabric development for a variety of deformation scenarios, and these fabric estimates are then quantitatively evaluated for compatibility with the seismic observations. In addition to constraining the coupling between mantle flow and crustal deformation along the western US plate boundary, the project will provide a general methodology for regional-scale anisotropy modeling for continents.