Dynamically Self-Consistent Contstraints on the Long-Term Strength of Faults in Western North America

北美西部断层长期强度的动态自洽约束

• 批准号: 0538437
• 负责人: William Holt
• 金额: $ 12万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-15 至 2009-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0538437&HistoricalAwards=false
• 关键词: Dynamically; Self; Consistent; Contstraints; Long

This work is advancing the understanding of the long-term strength of faults, lower crust, and upper mantle within the plate boundary zone of Western North America. Constraints on the long-term frictional resistance to steady sliding on active faults holds information on processes that affect earthquake rupture and the seismic cycle in general, such as dynamic weakening mechanisms, the role of pore pressure, and the role of intrinsic weakness, such as fault gauge. Observationally constrained kinematic and dynamic models of western North America are being refined using the Quaternary Fault database and GPS velocities as a constraint. The long-wavelength components of the GPS data are being used to help constrain the long-term deformation field, while the transient signal is filtered out. Moreover, the no-length-change directions in the Quaternary Fault database, along with fault style and slip vector directions, are being used to help constrain the long-term deformation field for latest Quaternary in western North America. The long-term estimates of the directions of principal axes and relative magnitudes of principal axes (style of faulting) for the rates of strain provide a proxy for orientation and style of deviatoric stress field responsible for such deformation. Dynamic models are constrained by topography, gravity, seismically defined crustal thicknesses and densities, heat flow, as well as the observations important for global mantle circulation models, such as tomography and history of subduction. Given these dynamic models, significant advances are being made on the constraints of long-term frictional behavior of faults because (1) the absolute magnitudes of vertically integrated deviatoric stresses acting within the brittle crust and the lithosphere are quantified and (2) a general approach is applied that accounts for the dramatic change in fault mechanisms observed across the plate boundary zone. Furthermore, hypotheses are being tested using a general three-dimensional model that properly deals with lateral strength anisotropy, lateral variations in strength profile characteristics, and non-uniform layer thicknesses resulting from topography on the surface and the Moho. The grant will be used to support the Ph.D. research of Stony Brook graduate student Elliot Klein. This work is providing further support for the mentoring of REU undergraduates who participate in development of visualization tools for understanding the plate boundary zone in western North America. These visualization tools will be displayed on the interactive web site maintained at UNAVCO (http://jules.unavco.org/). Moreover, this research is further supporting activities to updateexisting models on the ILP's Global Strain Rate Map (GSRM) interactive web site, used for both teaching and research (www.world-strain-map.org). In addition, this work is providing infrastructural support for broadening and enriching the activities of a graduate student, Daniel Hernandez, from an underrepresented group. The proposed work is basic research. It willadvance fundamental knowledge about the long-term strength of faults, and it holds implications for fault mechanics and even the earthquake rupture energy budget and earthquake cycle. However, the contributions we make to the younger generation are of societal benefit in itself.

这项工作正在推进对北美西部板块边界带内断层、下地壳和上地幔长期强度的理解。对活动断层上稳定滑动的长期摩擦阻力的限制，包含了影响地震破裂和地震周期的过程的信息，如动态弱化机制，孔隙压力的作用，以及内在弱点的作用，如断层规。正在利用第四纪断层数据库和GPS速度作为约束条件，对北美西部的观测约束运动学和动力学模型进行改进。全球定位系统数据的长波长部分正被用来帮助限制长期变形场，而瞬态信号则被滤除。此外，第四纪断层数据库中的无长度变化方向，沿着断层样式和滑动矢量方向，正被用来帮助约束北美西部第四纪晚期的长期变形场。主轴的方向和主轴的相对大小（风格的断层）的应变率的长期估计提供了一个代理的方向和风格的偏应力场负责这种变形。动力学模型受到地形、重力、地震确定的地壳厚度和密度、热流以及对全球地幔环流模型很重要的观测结果（如断层扫描和俯冲历史）的限制。在这些动力学模型的基础上，断层长期摩擦行为的约束正取得重大进展，因为（1）作用在脆性地壳和岩石圈内的垂直综合偏应力的绝对大小被量化，（2）一种通用的方法被应用于解释在板块边界带观测到的断层机制的巨大变化。 此外，假设正在测试使用一个通用的三维模型，适当地处理横向强度各向异性，横向变化的强度分布特征，以及不均匀的层厚度所造成的地形表面和莫霍面。这笔赠款将用于支持博士学位。斯托尼布鲁克的研究生埃利奥特·克莱因的研究。 这项工作提供了进一步的支持，指导REU本科生谁参与可视化工具的开发，以了解北美西部的板块边界带。这些可视化工具将在联合国艾滋病毒/艾滋病联合方案维持的交互式网站（http：//jules.unavco.org/）上展示。 此外，这项研究还进一步支持ILP的全球应变率图（GSRM）交互式网站（www.world-strain-map.org）上现有模型的更新活动。此外，这项工作还为扩大和丰富一名研究生丹尼尔埃尔南德斯的活动提供了基础设施支持，他来自一个代表性不足的群体。 这项工作属于基础研究。 它将推进对断层长期强度的基本认识，并对断层力学甚至地震破裂能量收支和地震周期具有意义。然而，我们对年轻一代的贡献本身就是社会利益。