Geodynamics and earthquakes in subduction zones and lithosphere

通过这项申请，我寻求资金，在未来五年内的任何一年为两到三名研究生提供部分支持。拟议的基础研究主要集中在俯冲带的地震过程。卡斯卡迪亚俯冲带对加拿大西海岸构成威胁的预期中的“大地震”，是这项研究的社会相关性的一个近乎家喻户晓的例子。学生们将研究是什么控制了巨型逆冲断裂的向下延伸，浅层断裂如何促成海啸的发生，地球地幔的粘弹性行为如何控制地震周期，今天观察到的地壳变形告诉我们下一次地震是什么，构造载荷如何控制俯冲带和岩石圈的应力状态，什么应力和构造环境使地震发生，等等。我们的主要方法是使用计算机建模来解释全球多学科观察，以揭示潜在的物理原理。指导学生从大量的观察和基本原理中发展出地球动力学的概念，而不仅仅是从教科书和传统模型中。为了了解收敛边缘的地球动力学及其更大的构造环境，我们将在未来五年内从三个方向进行研究。第一个方向是关于地壳如何为下一次地震积累能量。这一过程在前一次地震后立即开始，并以一种复杂的方式向下一次地震推进。它是由地幔的粘弹性行为控制的。我们将开发新的粘弹性地震周期模型，并对变形过程有更好的理解。这一结果将指导利用当代地壳形变观测来评估地震潜力。第二个方向是关于地震破裂本身。我们将研究是什么导致或阻止巨型断裂深入到50公里或更深，包括温度和断裂带材料在内的因素。我们还将研究巨型逆冲浅端的破裂如何使海底变形以产生海啸。对于浅层和深层部分，我们都对传统概念提出质疑，并致力于发展新的理论。研究结果将有助于地震和海啸危害的评估以及早期预警系统的设计。第三个方向是关于构造力如何引起地震。我们将研究俯冲带和岩石圈的应力状态，包括调查一个关于地震发生在似乎非常低的应力下的悖论。这些结果将使人们对地震产生的机制有新的理解，并指导未来将长期构造与地震灾害联系起来的研究。

With this application, I seek funds to provide partial support for two to three graduate students at any given year over the next five years. The proposed fundamental research is focused mainly on earthquake processes in subduction zones. The anticipated "big one" from the Cascadia subduction zone that threatens Canada's west coast is a near-home example to exemplify the societal relevance of the research. The students will study what controls the downdip extension of megathrust rupture, how shallow rupture contributes to tsunami generation, how the viscoelastic behaviour of Earth's mantle controls earthquake cycles, what crustal deformation observed today tells us about the next earthquake, how tectonic loading governs the state of stress in subduction zones and the lithosphere, what stress and structural environments enable earthquakes, and so forth. Our main method is to use computer modelling to explain global multidisciplinary observations to reveal underlying physical principles. The students are directed to develop geodynamic concepts from large volumes of observations and basic principles, not merely from textbooks and conventional models. With the long-term objective of understand the geodynamics of convergent margins and its larger tectonic environment, we will conduct research in three directions over the next five years. The first direction is about how the Earth's crust builds up energy for the next earthquake. The process begins right after the previous earthquake and proceeds in a complex fashion towards the next earthquake. It is controlled by the viscoelastic behaviour of the mantle. We will develop new viscoelastic earthquake cycle models and gain improved understanding of the deformation process. The results will guide the use of contemporary crustal deformation observations to evaluate seismic potential. The second direction is about earthquake rupture itself. We will study what enables or stops megathrust rupture to depths as large as 50 km or greater, factors including temperature and fault zone material. We will also study how the rupture of the shallow end of the megathrust deforms the seafloor to generate tsunamis. For both the shallow and deep parts, we question conventional concepts and aim to develop new theories. The results will contribute to the assessment of seismic and tsunami hazards and the design of early warning systems. The third direction is about how tectonic forces cause earthquakes. We will study the state of stress in subduction zones and the lithosphere, including investigating a paradox regarding earthquake occurrence under seemingly very low stresses. The results will yield new understanding of the mechanics of earthquake generation and guide future research in linking long-term tectonics to earthquake hazards.