Geodynamics and earthquakes in subduction zones and lithosphere

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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.