Understanding the deformation and processes that link ductile flow in the deep continental crust with frictional processes in the upper crustal seismogenic zone

了解将深部大陆地壳中的延性流与上地壳地震带中的摩擦过程联系起来的变形和过程

• 批准号: RGPIN-2020-05658
• 负责人: Grujic, Djordje
• 金额: $ 2.19万
• 依托单位: Dalhousie University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=740769
• 关键词: Understanding; deformation; processes; link; ductile

Subduction zones-regions of Earth's crust where one tectonic plate dives beneath another-are usually but not always associated with frequent, violent earthquakes. Occasionally, the downgoing plate slides slowly, smoothly and almost silently under the overriding plate. Canadian scientists have contributed to the research of seismic slow signals with geophysical observations of the Cascadia subduction zone. However, field observations, rock experiments and theoretical developments are also needed to advance our understanding of these newly identified fault slip phenomena. The proposed research program, with implications for future earthquakes offshore western Canada, aims to (a) expand our knowledge of mechanical processes that link mega earthquakes in the upper crust to steady and continuous slip in the lower crust via the brittle-ductile transition zone, which hosts the seismic slow signals, and (b) test a set of innovative methods to determine the ages of pre-instrumental earthquakes. (a) The importance of this research lies in the potential relationship between the fault transition zone and the parts of faults that generate destructive earthquakes. Some calculations find that the probability of a large earthquake occurring during a slow-slip event is 30-100 times greater than background probabilities. My research program involves interdisciplinary studies of exemplary exposed megathrust systems that record different stages of their development. Continental megathrust systems will be investigated via integration of observations across a range of scales and approaches, including field studies, microanalyses, thermochronology, geochronology, and numerical modelling. (b) Deformation data obtained from faulted rocks should be interpreted in the context of temporal or spatial variations in seismic processes. Thus, precise and accurate dating is crucial and entails developing innovative techniques that directly link age data to evidence of seismic slip in the rock record. This goal is achievable because of recent developments in our understanding of the physics of signals from minerals released via exposure to heat produced by seismic slip, and improvements in related analytical methods. To test the new techniques, we selected several locations where a surface earthquake rupture of known age provides access to samples suitable for attaining this goal. In addition to taking a leadership role in the discipline, Canada will benefit from this research by further understanding the processes responsible for Earth's major evolutionary steps, which can then feed into policy development for geohazard and environmental protection. Program goals will involve Canadian and international collaborators and train 2 PhD and 2 MSc graduate students, 1 PDF and undergraduates who will become knowledgeable in science communication and international and earthquake research, collaborate with world-leading research groups and gain access to world-class infrastructure.

俯冲带——地壳上一个构造板块潜入另一个构造板块之下的区域——通常（但并非总是）与频繁的剧烈地震有关。偶尔，下行板块会缓慢、平稳、几乎无声地在上覆板块下方滑动。加拿大科学家通过对卡斯卡迪亚俯冲带的地球物理观测，对地震慢信号的研究做出了贡献。然而，还需要实地观测、岩石实验和理论发展来推进我们对这些新发现的断层滑动现象的理解。拟议的研究计划对加拿大西部近海未来的地震有影响，其目的是(a)扩大我们对机械过程的认识，该过程通过承载地震慢信号的脆性-韧性过渡带将上地壳的特大地震与下地壳的稳定和连续滑动联系起来，(b)测试一套确定仪器前地震年龄的创新方法。(a)这项研究的重要性在于断层过渡带与产生破坏性地震的断层部分之间的潜在关系。一些计算发现，在缓慢滑动事件期间发生大地震的概率是背景概率的30-100倍。我的研究项目包括对典型的暴露的巨型逆冲系统的跨学科研究，这些系统记录了它们发展的不同阶段。大陆巨型逆冲系统将通过一系列尺度和方法的综合观测进行调查，包括实地研究、微观分析、热年代学、地质年代学和数值模拟。(b)从断层岩石获得的变形数据应根据地震过程的时间或空间变化来解释。因此，精确和准确的测年至关重要，需要开发创新技术，将年龄数据与岩石记录中的地震滑动证据直接联系起来。这一目标是可以实现的，因为我们最近对地震滑动产生的热量释放的矿物信号的物理学理解有所进展，以及相关分析方法的改进。为了测试新技术，我们选择了几个地点，在这些地点，已知年龄的地表地震破裂提供了适合实现这一目标的样本。除了在该学科中发挥领导作用外，加拿大还将从这项研究中受益，进一步了解地球主要进化步骤的过程，然后将其用于制定地质灾害和环境保护的政策。项目目标将涉及加拿大和国际合作者，培养2名博士和2名硕士研究生，1名PDF和本科生，他们将成为科学传播和国际地震研究的知识分子，与世界领先的研究小组合作，并获得世界一流的基础设施。