CAREER: Earth Rheology and Deformation Processes

造山运动、地震和大陆构造的其他表现形式基本上取决于岩石如何对应力作出反应。岩石流动特性取决于温度、岩石类型和流体含量，这些都不容易在深度测量，因此限制了我们对构造过程的基本理解。该项目将把联合收割机重力和地形数据与地震成像的新工具和新的变形测量和建模工具结合起来，仔细测量地球的质量密度变化以及必然要适应这些变化的岩石流动。通过测量岩石流动如何响应大的垂直应力，或？很多？是沉积物堆积或火山喷发造成的吗通过对岩石的表面、岩浆侵入地壳以及热和地壳厚度变化的研究，我们可以更好地了解岩石的流动特性，并确定这些流动特性如何从一个地方到另一个地方发生变化。项目？的科学目标对我们对地震物理学、地震灾害和造山过程的基本理解具有潜在的深远影响。岩石流动特性的知识有可能大大提高我们对地震周期和断层应力演化的理解，并可能有助于为冰川融化和其他气候变化的研究提供信息。该项目开发了一种创新方法，通过对重力、地形、地表热流和大地测量数据的动力学模型进行随机反演，结合用于地震测量产品的新分析工具，来估计岩石圈的流变参数（和有效流动粘度）。一个关键的创新将是通过反演地震测量（例如接收器函数振幅叠加）结合所需三维质量和温度场的其他数据来规避地震速度场建模中通常引入的误差。这些反过来将被用作动力学模型的输入，动力学模型将采用随机方法来反演浅（岩石圈）深度处的应力、应变率和流变参数的三维变化。地球变形的正演模拟，将三维粘度非均匀性在浅（岩石圈）深度表明，横向变化的流动流变施加一个非常根本的控制水平速度和应变在地球？s表面。估计大陆内部岩石圈弯曲强度的随机反演方法表现出强烈的相关性，在强度与陆内地震带的位置和大地应变聚焦的急剧梯度。在EarthScope主要研究设备计划积累的大量新数据以及最近数据分析方法和计算能力的革命的部分刺激下，该项目将研究流变学是否确实对板内变形施加一阶控制的基本问题，并探索岩石圈流变学的随机反演估计是否可以说明地震危险性。项目研究还将探讨均衡响应的观测方位各向异性的机制（和可能的效用），以及长期均衡响应与震后和更新世湖泊反弹研究的浅层粘度估计值存在差异的可能原因。主要的科学产品将是对浅层（岩石圈）质量密度、温度和流动流变学参数的新的全三维估计，这些估计将提供给科学界，可用于限制变形建模，或作为一种手段，分离出与断层滑动或冰质量负荷历史等其他理想信号交织在一起的固体地球粘弹性信号。

Mountain-building, earthquakes and other expressions of continental tectonics depend fundamentally on how rocks flow in response to stress. Rock flow properties depend upon temperature, rock type and fluid content, none of which are easily measured at depth, thus limiting our fundamental understanding of tectonic processes. This project will combine gravity and topography data with new tools for seismic imaging and new deformation measurements and modeling tools to carefully measure mass density variations in the Earth and the rock flow that inevitably must accommodate them. By measuring how rock flow responds to large vertical stresses, or ?loads?, that result from piling of sediments or volcanic flows on the Earth?s surface, from intrusion of magmas into the crust, and from thermal and crustal thickness variations, we can better understand flow properties of rock and also determine how these flow properties change from one place to another. The project?s scientific objectives have potentially far-reaching implications for our fundamental understanding of earthquake physics, seismic hazard and mountain-building processes. Knowledge of rock flow properties has the potential to greatly improve our understanding of the earthquake cycle and evolution of stress on faults, and may help to inform studies of glacial melting and other climatological changes. This project develops an innovative approach to estimating rheological parameters (and effective flow viscosity) of the lithosphere from stochastic inversion of dynamical models of gravity, topography, surface heat flow and geodetic data, coupled with new analysis tools for seismic measurement products. A key innovation will be the circumvention of errors commonly introduced in modeling of seismic velocity fields by inverting seismic measurements (e.g. receiver function amplitude stacks) in combination with the other data for desired 3D fields of mass and temperature. These in turn will be used as inputs to dynamical models, which will employ stochastic methods to invert for stress, strain rate and 3D variations in rheological parameters at shallow (lithospheric) depths. Forward modeling of Earth deformation incorporating 3D viscosity heterogeneity at shallow (lithospheric) depths suggests that lateral variations in flow rheology exert a very fundamental control on horizontal velocities and strains at the Earth?s surface. Stochastic inversion approaches to estimating lithospheric flexural strength in continental interiors exhibit strong correlation of sharp gradients in strength with locations of intracontinental seismic belts and geodetic strain focusing. Stimulated in part by the wealth of new data accruing from the EarthScope Major Research Equipment initiative, as well as by recent revolutions in data analysis methodologies and computing power, the project will examine the fundamental question of whether rheology does in fact exert a first-order control on intraplate deformation and explore whether stochastically inverted estimates of lithospheric rheology may illuminate seismic hazard. Project research will also explore mechanisms for (and possible utility of) observed azimuthal anisotropy of isostatic response as well as possible reasons for a discrepancy in estimates of shallow viscosity from long-term isostatic response versus from postseismic and Pleistocene lake rebound studies. The principal scientific products will be new, fully three-dimensional estimates of shallow (lithospheric) mass density, temperature and flow rheological parameters that will be made available to the scientific community and can be used to constrain deformation modeling, or as a means of separating out solid-Earth viscoelastic signals that are intertwined with other desirable signals such as fault slip or ice mass loading histories.