CAREER: Subduction Zone Hazards: Megathrust Rupture Dynamics and Tsunamis

俯冲带是地球上最壮观和最危险的两种自然灾害的发源地：大型逆冲地震和海啸。为了降低风险，我们必须更好地了解俯冲带的地震周期：相对板块运动中有多少是在地震而不是地震中发生的，地震耦合系数的估计在多大程度上允许人们预测未来大逆冲地震的程度？吸积棱镜的非弹性变形在破裂动力学中起什么作用？是什么决定了滑移的上倾程度，这是控制海底隆起和海啸高度的关键因素？是什么导致了海啸地震的缓慢破裂过程，而这些地震产生的海啸比从周期小于10秒的地震波振幅中预期的要大得多？这些问题将通过三维数值模拟来解决，三维数值模拟能够解决地震间载荷、蠕变和慢滑，以及具有真实几何形状和非均质材料结构的完全动态自发破裂。该模型的固体地球部分将与可压缩海洋完全耦合，以便同时捕捉地震波、水声（海洋声音）波和表面重力波（海啸）。重点将放在海底压力传感器记录的俯冲地震的水声特征上。海底位移激发的水声波在海啸发生前几分钟到达海岸，可能被用来估计海啸波高，用于早期预警系统。将对2011年东北大地震和其他近期事件进行模拟，并与地震、大地测量、海啸和海洋声学数据进行比较。地球上最大的地震发生在沿构造板块边界的俯冲带，比如华盛顿州和俄勒冈州近海的卡斯卡迪亚俯冲带。这些地震引起海底垂直隆起，产生海啸。该项目旨在利用计算模拟耦合固体地球（包括沿断层的摩擦滑动）和海洋的反应来描述这些地震和海啸的危害。模拟将捕捉地震破裂过程，以及地震波、水声波（海洋中的声波）和海啸的激发和传播。将为2011年日本东北大地震和其他近期事件开发具体模型，并与一系列地球物理数据进行比较，以验证建模方法。对日本东北大地震的初步模拟表明，部署在离岸数十或100公里处的海底压力传感器可以记录水声波，水声波可以用来快速估计海啸波高，用于早期预警系统。这项研究工作将辅以一项外联教育计划，旨在通过斯坦福大学和艾伦汉考克学院（AHC）之间的合作伙伴关系，提高加州中部海岸地区对自然灾害的认识和准备。PI将与AHC的教师和学生合作，为AHC开发地震和海啸演示和活动。it’周五晚间科学外展活动有600人参加？1000个社区成员。每年夏天，PI都会邀请一名AHC学生到斯坦福大学进行为期八周的研究实习。

Subduction zones are home to two of the most spectacular and dangerous natural hazards on Earth: megathrust earthquakes and tsunamis. To mitigate risk, we must better understand the earthquake cycle in subduction zones: What fraction of relative plate motion is accommodated aseismically instead of seismically, and to what extent do estimates of the seismic coupling coefficient allow one to predict the extent of future megathrust earthquakes? What role does inelastic deformation of the accretionary prism play in rupture dynamics? What determines the up-dip extent of slip, a key factor controlling the seafloor uplift and tsunami height? And what causes the slow rupture process of tsunami earthquakes that produce vastly larger tsunamis than expected from the amplitude of seismic waves at periods less than ~10 s? These questions will be addressed with three-dimensional numerical simulations capable of resolving interseismic loading, creep and slow slip, and fully dynamic spontaneous ruptures, with realistic geometries and heterogeneous material structure. The solid Earth component of the model will be fully coupled to a compressible ocean, in order to simultaneously capture seismic waves, hydroacoustic (ocean sound) waves, and surface gravity waves (tsunamis). Attention will be placed on the hydroacoustic signature of subduction earthquakes, as recorded by ocean bottom pressure sensors. Hydroacoustic waves excited by seafloor displacement arrive at the coast many minutes before the tsunami, and could potentially be used to estimate tsunami wave heights for use in early warning systems. Simulations will be conducted for the 2011 Tohoku-Oki earthquake and other recent events, and comparisons made to seismic, geodetic, tsunami, and ocean acoustic data. The largest earthquakes on Earth occur in subduction zones along the boundary between tectonic plates, such as the Cascadia subduction zone offshore Washington and Oregon. These earthquakes cause vertical uplift of the seafloor, generating tsunamis. This project is aimed at characterizing hazards from these earthquakes and tsunamis using computational simulations coupling the response of the solid Earth, including frictional sliding along faults, and the ocean. The simulations will capture the earthquake rupture process, as well as excitation and propagation of seismic waves, hydroacoustic waves (sound waves in the ocean), and tsunamis.Specific models will be developed for the 2011 Tohoku-Oki, Japan, earthquake and other recent events, and comparison made to a range of geophysical data to validate the modeling approach. Preliminary simulations of the Tohoku-Oki earthquake suggest that hydroacoustic waves, which can be recorded by cabled ocean bottom pressure sensors deployed tens or a hundred kilometers offshore, might be used to rapidly estimate tsunami wave heights for use in an early warning system. This research effort will be complemented with an outreach education program aimed an increasing awareness of and preparedness for natural hazards in the Central Coast region of California, through a partnership between Stanford and Allan Hancock College (AHC), a Hispanic-serving community college in the Central Coast. The PI will work with faculty and students at AHC to develop earthquake and tsunami demonstrations and activities for use in AHC?s Friday Night Science outreach programs attended by 600?1000 members of the community. Each summer, the PI will host an AHC student in an eight-week research internship at Stanford.