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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=717791
• 关键词: Understanding; deformation; processes; link; ductile

Subduction zonesregions of Earth's crust where one tectonic plate dives beneath anotherare 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 30100 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.

俯冲带是地壳中一个板块潜入另一个板块下方的区域，通常但并不总是与频繁的剧烈地震有关。有时，下行板块会缓慢、平稳、几乎无声地滑到上方板块下方。加拿大科学家通过对卡斯卡迪亚俯冲带的地球物理观测为地震慢信号的研究做出了贡献。然而，还需要现场观察、岩石实验和理论发展来加深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具有影响，旨在（a）扩展我们对机械过程的了解，该机械过程通过脆性-韧性过渡区（承载地震慢信号）将上地壳的大地震与下地壳的稳定和连续的滑动联系起来，以及（b）测试一套创新方法来确定仪器前地震的年龄。 (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，慢滑事件期间发生大地震的概率比背景概率大30100倍。我的研究项目涉及对典型暴露的巨型逆冲系统的跨学科研究，记录其发展的不同阶段。将通过整合一系列尺度和方法的观测来研究大陆巨型逆冲系统，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在地震过程的时间或空间变化的背景下进行解释。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移证据直接联系起来。这一目标是可以实现的，因为我们对地震滑移产生的热量所释放的矿物信号的物理理解的最新进展，以及相关分析方法的改进。为了测试新技术，我们选择了几个已知年龄的地表地震破裂的地点，可以获取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，加拿大还将通过进一步了解地球主要进化步骤的过程而从这项研究中受益，然后将其纳入地质灾害和环境保护的政策制定中。项目目标将涉及加拿大和国际合作者，并培养 2 名博士生和 2 名硕士研究生、1 名 PDF 生和本科生，他们将在科学传播、国际和地震研究方面拥有丰富的知识，与世界领先的研究小组合作，并获得世界一流的基础设施。