Geodynamics and earthquakes of subduction zones

提出的研究旨在了解俯冲带的力学过程。这一发现将对理解板块俯冲的地球动力学，特别是其地震过程具有重要意义。该提案寻求有限的资金，在未来五年的任何一年为两名研究生提供部分支持，以对三个主题进行计算机建模。第一个主题是大俯冲地震的变形周期，比如1700年加拿大西海岸发生的9级地震。基于不同俯冲带的大地测量学和地震学观测，我们将开发模型来解决地震期间和之后地壳和地幔如何变形以及应变能如何重新积累导致下一次事件。第二个主题是幕式震颤和滑动（ETS），这是一种新发现的现象，发生在一些俯冲断层的发震带，如西海岸外的卡斯卡迪亚俯冲带。这将有助于我们理解俯冲断层的复杂行为，即它们不仅在地震中滑动，而且在地震间隙的地震滑动瞬变中滑动的原因和方式。第三个主题是对大俯冲地震的几何和构造控制。地震破裂是不稳定摩擦的表现，但俯冲断层不是离散的摩擦接触，而是三维复杂构造带。我们将致力于建立一个新的概念框架，这将使我们能够解决许多尚未解决的一级问题，例如为什么卡斯卡迪亚俯冲带倾向于产生不频繁但巨大的（M ~ 9）地震，而许多其他俯冲带倾向于产生更频繁但较小的事件。

The proposed research is designed to understand mechanical processes of subduction zones. The findings will have important implications for understanding the geodynamics of plate subduction, especially its earthquake processes. This proposal seeks limited funding to provide partial support for two graduate students at any given year over the next five years to conduct computer modeling on three subjects. The first subject is the deformation cycles of great subduction earthquakes such as the M 9 earthquake in 1700 off Canada's west coast. Based on geodetic and seismological observations from different subduction zones, we will develop models to address how the Earth's crust and mantle deform during and after an earthquake and how strain energy is re-accumulated leading to the next event. The second subject is the Episodic Tremor and Slip (ETS), a phenomenon newly found downdip of the seismogenic zone of some subduction faults, such as at the Cascadia subduction zone off the west coast. This will help us understand the complex behavior of subduction faults, that is, why and how they slip not only in earthquakes but also in aseismic slip transients during the time between earthquakes. The third subject is geometrical and structural controls on great subduction earthquakes. Earthquake rupture is a manifestation of unstable friction, but subduction faults are not discrete frictional contacts but zones of three-dimensional structural complexity. We will work on a new conceptual framework that will allow us to address many unanswered first-order questions such as why the Cascadia subduction zone tends to produce infrequent but giant (M ~ 9) earthquakes while many other subduction zones tend to produce more frequent but smaller events.