CAREER: Earth Rheology and Deformation Processes

职业：地球流变学和变形过程

• 批准号: 0955909
• 负责人: Anthony Lowry
• 金额: $ 50万
• 依托单位: Utah State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-15 至 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0955909&HistoricalAwards=false
• 关键词: CAREER; Earth; Rheology; Deformation; Processes

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.

造山、地震和大陆构造的其他表现形式从根本上取决于岩石如何对应力做出反应。岩石流的性质取决于温度、岩石类型和流体含量，这些都不容易在深处测量，因此限制了我们对构造过程的基本理解。该项目将把重力和地形数据与新的地震成像工具和新的形变测量和建模工具结合起来，以仔细测量地球上的质量密度变化和不可避免地必须适应它们的岩石流。通过测量岩石流对沉积或火山流在地表堆积、岩浆侵入地壳以及热力和地壳厚度变化所产生的巨大垂直应力或载荷的响应，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变化到另一个地方。S项目的科学目标对我们对地震物理、地震危险和造山过程的基本理解具有潜在的深远影响。对岩石流性质的了解有可能极大地提高我们对地震周期和断层上应力演化的理解，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的方法，通过重力、地形、地表热流和大地测量数据的随机反演来估计岩石圈的流变参数(和有效流动粘度)，并结合用于地震测量产品的新分析工具。一项关键的创新将是通过将地震测量(例如，接收器函数振幅叠加)与所需的3D质量场和温度场的其他数据相结合，来规避通常在地震速度场建模中引入的误差。这些数据将被用作动力学模型的输入，动力学模型将使用随机方法来反演浅层(岩石圈)的应力、应变率和流变参数的三维变化。在浅层(岩石圈)考虑三维粘性非均匀的地球变形正演模拟表明，流体流变性的横向变化对S地表的水平速度和应变起着非常根本的控制作用。估计大陆内部岩石圈弯曲强度的随机反演方法显示，强度的急剧梯度与陆内地震带的位置和大地应变聚焦具有很强的相关性。该项目将在一定程度上受到地球范围重大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革命的刺激，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，并探索岩石圈流变性的随机反演估计是否可能揭示地震危险。项目研究还将探索观测到的均衡响应方位各向异性的机制(和可能的用途)，以及从长期均衡响应与地震后和更新世湖泊反弹研究对浅层粘度估计存在差异的可能原因。主要的科学成果将是对浅层(岩石圈)质量密度、温度和流动流变参数的新的全三维估计，这些估计将向科学界提供，并可用于约束变形建模，或用作分离与断层滑动或冰块加载历史等其他所需信号交织在一起的固体-地球粘弹性信号的一种手段。