Geological Controls on the Seismic Cycle

目前，科学家们还无法预测地震，部分原因是我们对控制地震发生的时间、地点和强度的地球过程没有基本的了解。地震波震动地球表面，由地震仪探测到，这使科学家能够精确地确定断层破裂的确切时间和位置，而断层破裂导致了断层带深处的地震。我通过在地球表面的侵蚀作用下抬升和暴露的古断裂带中确定这个震源区来研究对地震的控制。在岩石中原位研究震源使我能够在小尺度（千米到纳米）上进行观察，这是单个矿物颗粒在地震中破碎、融化和反应以控制岩石性质的尺度，但这超出了现代地震学的限制。我的方法包括投入大量时间勘探和发现暴露出古老断层的新领域，目的是拓宽许多类型断层系统的变化范围，从而有助于对地震有更广泛的了解。这些古老的断层使我能够研究滑动面的几何形状，并推断出地震周期中对深度能量平衡的控制。利用包括无人机航空摄影在内的前沿野外技术，我重建了古代断裂带露头的三维模型，并利用这些模型将古代地震破裂的基本几何形状和长度尺度与地震学和大地测量学的现代地震观测结果进行比较。我确定岩石化学，矿物学和流体-岩石反应特征的这些断层在地震之前，期间和之后。地震断层中的流体-岩石反应对魁北克和加拿大特别重要，因为这些流体是某些类型矿床沉积的原因，而地震是可以触发贵金属沉积的事件。通过调查不同岩石类型和构造环境下的一系列古代断层，我的研究为控制加拿大和世界其他地区的地震周期提供了一个通用模型。

At present, scientists are not able to predict earthquakes, in part because we do not have a fundamental understanding of the earth processes which control when and where earthquakes occur and how big they are. Seismic waves shake the earth's surface and are detected by seismometers, which allow scientists to pinpoint the exact time and location of the fault rupture which caused the earthquake at depth within fault zones. I investigate the controls on earthquakes by identifying this earthquake source region in ancient fault zones which have been uplifted and exposed by erosion at the surface of the earth. Studying the earthquake source in situ within the rocks allows me to make observations on small scales (kilometers down to nanometers), which are the scales at which individual mineral grains break, melt, and react to control the rock properties during earthquakes, but which are beyond the limit of modern seismology. My approach involves significant time invested in exploration and discovery of new field areas where ancient faults are exposed, with the intention of opening up the breadth of variation across many types of fault systems to contribute to a more generalized understanding of earthquakes. The ancient faults allow me to study the geometry of slip surfaces and infer controls on the energy balance at depth during the seismic cycle. Using cutting-edge field techniques including drone aerial photography, I reconstruct a three-dimensional model of outcrops of ancient fault zones and use these to compare the fundamental geometry and length scales of ancient earthquake ruptures to the modern earthquake observations from seismology and geodesy. I identify the rock chemistry, mineralogy, and fluid-rock reactions which characterize these faults before, during and after earthquakes. Fluid-rock reactions in seismic faults are of particular importance to Quebec and Canada because these fluids are responsible for the deposition of some types of ore deposits, and earthquakes are events which can trigger the deposition of precious metals. By investigating a range of ancient fault sites in different rock types and tectonic settings, my research contributes to a general model for controls on the earthquake cycle across Canada and the rest of the world.