CAREER: Mechanics of Viscous Damage Zones Along Rough Faults and Community Tutorial/Forums for Experimental Rock Mechanists

职业：沿粗糙断层的粘性损伤区域的力学和实验岩石力学的社区教程/论坛

• 批准号: 2045259
• 负责人: Hiroki Sone
• 金额: $ 52.81万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2045259&HistoricalAwards=false
• 关键词: CAREER; Mechanics; Viscous; Damage; Zones

Earthquakes occur to release the compressional forces (stress) that accumulate in the Earth due to plate tectonics. Such accumulation and release of stress is oftentimes studied using models that treat rocks as spring-like elastic materials. However, real rocks - especially those surrounding fault zones - contain many defects that cause non-elastic (permanent) deformation. Therefore, movement between tectonic plates may not only be accommodated by slip along faults, but also by deformation distributed in the surrounding rocks. Ignoring such effects may lead to overestimating stress accumulation in the Earth. Accounting for rock deformation around faults is thus crucial to accurately assess seismic hazards. Here, the team aims to characterize such rock behavior through laboratory experiments. They use rock specimens with existing defects; specimens are either collected around natural faults or prepared in the laboratory. They quantify the rock behavior and assess its impact on earthquake mechanics through numerical modeling. The project provides support for an early-career scientist and graduate and undergraduate students at University of Wisconsin - Madison. It also fosters knowledge transfer and community building among experimentalists experts in rock mechanics.The goal of the project is to evaluate the impact of fault damage-zone rheology on fault mechanics. Field and laboratory evidence shows that fault damage-zone rocks exhibit time-dependent deformational behavior and that shear stress relaxation within the damage zone is a ubiquitous phenomenon. Viscous properties of fault damage-zone rocks are not acknowledged in current fault mechanical models. This may lead to an over-estimation of fault shear stress accumulation. Here, the researchers characterize the damage distribution around selected fault zone outcrops. The emphasis is on quantifying the heterogeneities across and along the faults. Laboratory experiments are conducted on both natural and synthetic damage-zone rocks to constrain the viscous constitutive properties of damaged rocks in the framework of viscoplasticity. A synthesis modeling incorporates findings from the field and lab. The goal is to evaluate how slow distributed deformation in rough damage zones influence the interseismic loading of fault shear stress. The team also examines how the distribution of stress and fault slip evolve during the interseismic period; this provides insights on how earthquake statistics and kinematics evolve during interseismic loading. Another goal is to evaluate the validity of upscaling friction laws to field scale problems. Finally, geophysical observations on transient changes in seismic velocity and strain from the San Jacinto Fault Zone will be examined to explore consistency with the viscous properties constrained in the laboratory.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

发生地震会释放由于板块构造引起的压缩力（应力）。这种积累和应力的释放通常是使用将岩石视为弹簧样弹性材料的模型来研究的。但是，真正的岩石 - 尤其是周围断层区域 - 包含许多导致非弹性（永久性）变形的缺陷。因此，构造板之间的运动不仅可以通过沿断层滑动来容纳，而且可以通过在周围岩石中分布的变形来容纳。忽略这种影响可能会导致高估地球中的压力积累。 因此，对断层周围的岩石变形进行核算对于准确评估地震危害至关重要。在这里，团队旨在通过实验室实验来表征这种摇滚行为。他们使用现有缺陷的岩石标本；标本要么是在自然断层周围收集的，要么是在实验室中准备的。他们通过数值建模来量化岩石行为并评估其对地震力学的影响。该项目为威斯康星大学 - 麦迪逊分校的早期科学家和研究生和本科生提供了支持。它还促进了岩石力学专家之间的知识转移和社区建设。该项目的目的是评估断层损害区流变对故障力学的影响。现场和实验室证据表明，断层损伤区岩石表现出时间依赖性变形行为，损伤区内的剪切应力松弛是无处不在的现象。当前断层机械模型中未确认断层损伤区岩石的粘性特性。这可能会导致断层剪切应力积累的过度估计。在这里，研究人员表征了选定断层区露头周围的损伤分布。重点是量化断层之间和沿线的异质性。实验室实验是对自然和合成损伤区岩石进行的，以限制受损岩石的粘性本构特性在粘性性的框架内。合成模型结合了现场和实验室的发现。目的是评估粗糙损伤区域中分布变形的速度如何影响断层剪切应力的经过震荡。该小组还研究了在微观时期的压力和断层滑移的分布如何发展；这提供了有关在经济势载荷过程中地震统计和运动学如何发展的见解。另一个目标是评估将摩擦法律提高到现场尺度问题的有效性。最后，将检查对San Jacinto断层区域抗震速度和压力的瞬时变化的地球物理观察，以探讨与实验室中粘性属性一致的一致性。该奖项反映了NSF的法定任务，并通过评估该基金会的知识绩效和广泛的影响来评估NSF的法定任务，并被认为是值得的。