Improving Earthquake Forecasting and Seismic Hazard Analysis Through Extreme-Scale Simulations

地震是在活动断层系统内复杂的、多尺度的相互作用中产生的，时间尺度从毫秒到数百万年不等，这些活动断层系统非常难以观察。基于物理的大规模地震模拟是基本的科学工具，可以用来更好地理解这些危险的自然现象。该项目将开发基于物理的代码，用于模拟蓝色水域的地震，并应用这些模拟能力来改进现有的危险分析方法。Blue Waters系统的超大规模计算和数据管理能力将使该项目能够开发和测试以更现实的方式捕捉物理的地震模型，并以更精细的分辨率和更高的频率运行模拟。结果将更好地量化地震危险及其不确定性。该项目将使用数值实验和大规模模拟来推进基于物理的概率地震危险性分析(PSHA)方法，以扩大当前表示震源物理、滞弹性和地质非均质性的尺度范围。具体地说，该研究项目将努力实现为提高我们对地震过程的理解和推进基于物理学的PSHA而定义的七个计算目标：(1)开发基于经验校准的基于物理学的地震预报。(2)开发一个统计上足够的、但减少的、代表新的统一加州地震破裂预测的破裂集。(3)实现了一种新的基于动态破裂的运动学震源模型，用于计算高达8周/秒的地面运动。(4)评估在以前的模拟中观察到的盆地连通现象，以确定在低地震频率下进行波导模拟的重要性。(5)研究和表征材料模型和震源模型对地面运动模拟精度的影响。(6)对模拟中使用的流变模型进行验证和标定。(7)对易损土石坝进行物理致灾能力试验。这项研究的目的是改进地震过程的物理表示和地震模拟的确定性代码，这将改进美国的PSHA实践，并有利于全世界的地震系统科学。

Earthquakes emerge from complex, multiscale interactions across time scales that range from milliseconds to millions of years within active faults systems that are incredibly difficult to observe. Large-scale physics-based earthquake simulations are essential scientific tools that can be used to better understand these hazardous natural phenomena. This project will develop physics-based codes for simulating earthquakes on Blue Waters and apply these simulation capabilities to improve existing hazard analysis methods. The very large scale computing and data management capabilities of the Blue Waters system will allow the project to develop and test earthquake models that capture physics in a more realistic manner, and to run simulations at finer resolutions and higher frequencies. The results will better quantify seismic hazards and their uncertainties. This project will advance physics-based probabilistic seismic hazard analysis (PSHA) methods using numerical experimentation and large-scale simulations to increase the scale range in current representations of source physics, anelasticity, and geologic heterogeneity. Specifically, the research project will work towards seven computational objectives defined to improve our understanding of earthquake processes and advance physics-based PSHA: (1) Develop an empirically-calibrated physics-based earthquake forecast. (2) Develop a statistically sufficient, but reduced, rupture set representative of the new Unified California Earthquake Rupture Forecast. (3) Implement a new dynamic-rupture based kinematic source model to compute ground motions up to 8 cycles per second. (4) Evaluate the basin connectivity phenomenon observed in previous simulations to establish the importance of waveguide modeling at low seismic frequencies. (5) Investigate and characterize the influence of material and source models on the accuracy of ground motion simulations. (6) Validate and calibrate the rheological models used in simulations. (7) Test the physics-based hazard capabilities on a vulnerable embankment dam. The goal of this research is to improve the physical representations of earthquake processes and the deterministic codes for simulating earthquakes, which will improve PSHA practice in the United States and benefit earthquake system science worldwide.