FESD Type I: Earthquake Fault System Dynamics

大地震发生在世界构造板块的边界，那里有越来越多的人口面临高地震风险。该项目开发并使用大规模计算机模拟来研究控制沿板块边界断层系统发生的地震的发生和特征的断层系统相互作用。该项目将开发北美板块边界的计算机模型，该边界由不列颠哥伦比亚省南部、华盛顿州、俄勒冈州和北加州的俯冲带组成；以及加州北部和南部的圣安德烈亚斯断层系统。这项研究解决了地震的短期（几分钟到几年）可预测性，以及使断层系统在大地震中失效的长期过程（100-1000年）。为了更好地描述破坏性地震中地面震动的震级和变化，这是提高我们对地震灾害的恢复能力所必需的，断层系统模型将与先进的地面运动模拟相结合。在几何形状复杂的分形断裂系统中，脆壳在板块边界处的高度集中变形主要是通过断裂的综合滑移发生的。断层滑动现象，包括地震、连续断层蠕变、慢滑动事件、地震余震和地震重复，具有异常广泛的时间和空间尺度，是这些系统中丰富的相互作用的产物。本项目开发的板块边界断层系统模拟将跨越10000年的板块运动，并由多达106个离散事件组成。由于我们对断层本构性质和引起不同断层滑动模式的相互作用的理解的进步，这种规模的模拟现在是可能的；板块边界断裂系统三维几何构造知识的增长；以及数值方法的发展，这些方法允许在非常广泛的空间和时间尺度上进行高效的模拟。系统级模拟提供了一种实验能力来探测这些非常复杂的系统，以更好地理解产生可观察效应的相互作用，并提高预测能力。此外，模拟提供了将地震学、构造大地测量学和地震地质学的广泛观测整合到一个共同框架中的手段。概率地震危害分析（PSHA）是地震科学家和工程师用来确保建筑环境地震安全的主要工具，它需要对所有潜在破坏性地震的地面运动进行长期预测。本研究将把断层系统模型与先进的断层破裂和地面运动模拟相结合，以研究可靠的PSHA所需的强地面运动的统计性质。

Great earthquakes occur at the boundaries of the world's tectonic plates where an increasing fraction of the population is exposed to high seismic risk. This project develops and uses large-scale computer simulations to investigate fault system interactions that control the occurrence and characteristics of earthquakes occurring along plate boundary fault systems. The project will develop computer models of the North American plate boundary, which consists of the subduction zone of Southern British Columbia, Washington, Oregon, and Northern California; and the San Andreas fault system of Northern and Southern California. This research addresses the short-term (minutes to years) predictibilty of earthquakes, and long-term processes (100-1000 years) that condition fault systems to fail in great earthquakes. To better characterize the magnitude and variability of ground shaking in damaging earthquakes, which is needed for increasing our resilience to earthquake disasters, the fault system models will be integrated with advanced ground motion simulations.The highly concentrated deformation of the brittle crust at plate boundaries largely occurs through the integrated slip of faults in geometrically complex fractal-like fault systems. Fault slip phenomena, including earthquakes, continuous fault creep, slow slip events, earthquake afterslip, and earthquake repeaters, with their exceptionally wide range of temporal and spatial scales, are products of the rich array of interactions that operate in these systems. The simulations of plate boundary fault systems developed by this project will span 10,000yrs of plate motion and consist of up to106 discrete events. Simulations on this scale are now possible due to advances in our understanding of fault constitutive properties and the interactions that give rise to the different modes of fault slip; growth of knowledge to define the 3D geometry of plate boundary fault systems; and development of numerical methods that permit highly efficient simulations across a very wide range of spatial and temporal scales. System-level simulations provide an experimental capability to probe these very complex systems to better understand the interactions that give rise to observable effects, and to advance predictive capabilities. In addition, simulations provide the means to integrate a wide range of observations from seismology, tectonic geodesy, and earthquake geology into a common framework. Probabilistic seismic hazard analysis (PSHA), the main tool used by earthquake scientists and engineers to ensure seismic safety in the built environment, requires long-term forecasting of ground motions of all potentially damaging earthquakes. This research will integrate the fault system models with advanced fault rupture and ground motion simulations to investigate the statistical nature of strong ground motions needed for reliable PSHA.