From California to British Columbia, the Pacific Northwest coast bears an omnipresent earthquake and tsunami hazard from the Cascadia subduction zone. Multiple lines of evidence suggests that magnitude eight and greater megathrust earthquakes have occurred - the most recent being 321 years ago (i.e., 1700 A.D.). Outstanding questions for the next great megathrust event include where it will initiate, what conditions are favorable for rupture to span the convergent margin, and how much slip may be expected. We develop the first 3-D fully dynamic rupture simulations for the Cascadia subduction zone that are driven by fault stress, strength and friction to address these questions. The initial dynamic stress drop distribution in our simulations is constrained by geodetic coupling models, with segment locations taken from geologic analyses. We document the sensitivity of nucleation location and stress drop to the final seismic moment and coseismic subsidence amplitudes. We find that the final earthquake size strongly depends on the amount of slip deficit in the central Cascadia region, which is inferred to be creeping interseismically, for a given initiation location in southern or northern Cascadia. Several simulations are also presented here that can closely approximate recorded coastal subsidence from the 1700 A.D. event without invoking localized high-stress asperities along the down-dip locked region of the megathrust. These results can be used to inform earthquake and tsunami hazards for not only Cascadia, but other subduction zones that have limited seismic observations but a wealth of geodetic inference.

中文翻译：

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使用 3-D 动态破裂模拟评估沿 Cascadia 大推力的边缘范围内的破裂行为

从加利福尼亚到不列颠哥伦比亚省，太平洋西北海岸承受着来自卡斯卡迪亚俯冲带的无所不在的地震和海啸危险。多条证据表明已经发生了 8 级或更大的大逆冲地震——最近一次发生在 321 年前（即公元 1700 年）。下一个巨大的大逆冲事件的悬而未决的问题包括它将在哪里开始，什么条件有利于破裂跨越收敛边缘，以及预计会发生多少滑动。我们为卡斯卡迪亚俯冲带开发了第一个由断层应力、强度和摩擦驱动的 3-D 全动态破裂模拟，以解决这些问题。我们模拟中的初始动态应力降分布受到大地耦合模型的约束，分段位置取自地质分析。我们记录了成核位置和应力下降对最终地震矩和同震沉降幅度的敏感性。我们发现最终的地震规模很大程度上取决于卡斯卡迪亚中部地区的滑动不足量，对于卡斯卡迪亚南部或北部的给定起始位置，这被推断为地震间蠕动。这里还介绍了几个模拟，它们可以非常接近记录的公元 1700 年事件的海岸沉降，而不会引起沿着大逆冲断层的下倾锁定区域的局部高应力粗糙度。这些结果不仅可用于为卡斯卡迪亚以及其他地震观测有限但具有丰富的大地测量推断的俯冲带提供地震和海啸危险信息。