Collaborative Research: Developing a Link between Dynamic Friction and Fracture Mechanics Models of Earthquake Rupture using a New Dynamic Double-direct Shear Apparatus

合作研究：使用新型动态双直剪装置建立地震破裂的动态摩擦和断裂力学模型之间的联系

• 批准号: 1215669
• 负责人: WIlliam Griffith
• 金额: $ 15.96万
• 依托单位: University of Akron
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-15 至 2013-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1215669&HistoricalAwards=false
• 关键词: Collaborative; Research; Developing; Link; between

There is broad agreement amongst researchers in the geophysics community that similar rocks may undergo very different weakening processes in different normal stress and/or slip velocity regimes. Consequently, inference of weakening behavior of fault rocks in situ from laboratory experiments at interfacial conditions of relevance to earthquake physics cannot be done simply by scaling exercises, and relatively small changes in normal stress and/or the slip speed can result in changes in the slip weakening distance of an order of magnitude. Motivated by these observations, the investigators propose to advance the current state of our understanding regarding the frictional constitutive behavior of earthquake faults using two principal approaches: (1) implementing a new dynamic shear friction testing apparatus by synergistically combining the split-Hopkinson pressure bar and the double-direct shear friction apparatus to the study of dynamic friction in both intact and granular geo-materials; and (2) developing a methodology for testing the efficacy of parameters extracted from dynamic friction experiments in dynamic rupture models. The intellectual merit of this proposal is strengthened by the fact that it addresses some of the outstanding problems in earthquake-physics, including the influence of slip and slip-velocity on fault strength during a typical fault rupture event. No laboratory experiments to-date combine the large displacement, high slip rates, and normal stresses that are understood to characterize dynamic earthquake slip at natural fault interfaces. These failings mean that processes that may occur during dynamic slip in earthquakes have not been explored experimentally. The new experimental configuration proposed in here, which is a modification of the well-established experimental procedures employed routinely in engineering for investigating high-strain-rate behavior of engineering materials (split Hopkinson pressure bar) and quasi-static friction studies in geo-materials (double-direct shear apparatus), has the potential to provide friction data in the slip-speed and normal stress range of direct relevance to earthquake physics. Furthermore, the two-pronged methodology of our proposed work aims to fundamentally change the way we approach studying the frictional resistance of faults. The first task guarantees significant results that will advance the state of understanding of dynamic friction during earthquake rupture under relevant conditions, whereas the second approach will further constrain the inferred frictional constitutive models by comparing predictions of dynamic rupture models that incorporate lab-derived frictional slip constitutive behavior with laboratory rupture experiments. The proposed research will contribute toward our understanding of earthquakes in several ways. To construct theoretical models of the earthquake process, we must understand how frictional resistance on faults changes during an earthquake. In particular, the weakening mechanism that we propose to study have profound implications for the magnitude of stress-drops during earthquakes and consequently for the magnitude of strong ground shaking. The manner in which fault strength varies with displacement and rupture velocity, as well as the rate at which healing occurs as the slip velocity decreases behind the rupture tip, can control the mode of rupture propagation, i.e. as a crack or a pulse. Thus, understanding dynamic friction is important not only for practical matters related to predicting strong ground motions and resulting damage, but also for answering major scientific questions receiving considerable attention, e.g. the strength of the San Andreas fault/the heat-flow paradox, the question that ultimately is responsible for the San Andreas Fault Observatory at Depth (SAFOD) project. The proposed program also provides exciting opportunities for interdisciplinary research and educational interactions by involving faculty and graduate students from two neighboring institutions.. Both universities are strongly encouraging the involvement of undergraduate students in cutting edge faculty research, and this would occur for the proposed work as well. Special attention will also be given to recruitment of underrepresented minority students for the project. Dissemination of research results is planned by conference presentations and publications in relevant peer-reviewed journals. The investigators will also employ internet and mass-media-based information dissemination to increase awareness of the potential impact of the proposed research in earthquake hazard mitigation.

地球物理学界的研究人员之间存在广泛的一致性，即在不同的正常压力和/或滑动速度制度中，类似的岩石可能会发生截然不同的弱化过程。因此，在与地震物理相关的界面条件下，从实验室实验中的故障岩石行为的推断不能简单地通过缩放练习来进行，并且正常压力和/或滑移速度相对较小的变化可能会导致滑移的变化减弱的数量级距离。 在这些观察结果的推动下，调查人员建议使用两种主要方法来提高我们对地震断层摩擦本构行为的理解的现状：（1）通过协同结合分裂的人高压棒和分裂的剪切摩擦测试设备双向剪切摩擦仪置于完整和颗粒状地质材料中动态摩擦的研究； （2）开发一种测试从动态破裂模型中动态摩擦实验中提取的参数功效的方法。 该提案的智力优点得到了以下事实，即它解决了地震物理学的一些杰出问题，包括在典型的断层破裂事件中滑动和滑移对断层强度的影响。没有实验室实验待办事项结合了较大的位移，高滑动速率和正常应力，这些应力被理解为表征自然断层界面处的动态地震滑动。这些失败意味着在地震中可能发生的过程中可能发生的过程尚未在实验中探索。此处提出的新实验配置是对工程材料的高应变率行为（拆分霍普金森压力棒）和地质材料中的准静态摩擦研究的高压率行为的定期修改的修改。 （双向剪切设备），有可能在与地震物理的直接相关性的滑动速度和正常应力范围内提供摩擦数据。此外，我们提出的工作的两种义方法旨在从根本上改变研究断层摩擦抗性的方式。第一项任务保证了重大结果，可以在相关条件下地震破裂期间对动态摩擦的理解状态提高理解状态，而第二种方法将通过比较包含实验室摩擦的动态破裂模型的预测来进一步限制推断的摩擦本构模型实验室破裂实验的行为。拟议的研究将以几种方式有助于我们对地震的理解。为了构建地震过程的理论模型，我们必须了解地震期间断层的摩擦抗性如何变化。特别是，我们建议研究的弱化机制对地震期间的压力滴度的大小有着深远的影响，因此对强大的地面摇动的幅度具有深远的影响。断层强度随位移和破裂速度而变化的方式，以及随着滑动速度在破裂尖端后面降低的降低而发生愈合的速度，可以控制破裂传播的模式，即作为裂缝或脉冲。因此，理解动态摩擦不仅对预测强大的基础运动和造成的损害相关的实际事项很重要，而且对于回答主要的科学问题而受到相当大的关注，例如圣安德烈亚斯断层/热流悖论的强度，最终导致了San Andreas断层天文台（SAFOD）项目的问题。 拟议的计划还通过参与来自两个邻近机构的教职员工和研究生，为跨学科研究和教育互动提供了令人兴奋的机会。这两所大学都强烈鼓励本科生参与尖端教师研究，这将作为拟议的工作作为拟议的工作，这将成为拟议中的工作。出色地。还将特别注意该项目代表性不足的少数族裔学生。研究结果的传播是通过相关同行评审期刊中的会议演讲和出版物计划的。研究人员还将采用互联网和大众的信息传播，以提高人们对拟议研究对地震危害的潜在影响的认识。