Earthquake Rupture Simulation: thermo-mechanical models and validation with strong motion data

地震破裂模拟：热机械模型和强运动数据验证

• 批准号: 0810271
• 负责人: Steven Day
• 金额: $ 29万
• 依托单位: San Diego State University Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-02-01 至 2013-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0810271&HistoricalAwards=false
• 关键词: Earthquake; Rupture; Simulation; thermo; mechanical

Large earthquakes are rare, complex events and their sources are deep-seated and inaccessible to direct observation. Moreover, relatively few near-source strong motion recordings exist for events of very large magnitude, i.e., those earthquakes that pose the greatest potential threat to life safety and the built environment. Well-validated computer simulations provide a means to forecast strong ground motion from large earthquakes, based upon the best available earthquake physics and wave propagation models. Simulations can help fill the pressing need for site-appropriate ground-shaking estimates for use in performance-based engineering and structural analysis, a requirement that is especially acute in light of the construction boom in very tall buildings in western U.S. cities. Computer simulations are also essential for advancing our basic scientific understanding of earthquakes, as they reveal how large-scale effects emerge from smaller-scale interactions that are difficult to study experimentally or via traditional theoretical analysis. This project is developing numerical earthquake models that represent the principal mechanical and thermal processes of faulting, including the weakening of frictional resistance by the heating of rock contacts and the pressurization of pore fluids. These computer models also incorporate established statistical representations of fault roughness and of the stress state in the earth, as well as the strength limits of geologic materials (which place upper bounds on the amplitude of the stress wave disturbances excited by faulting). The models must run efficiently on large computer clusters (i.e., those with thousands of processor cores), so that they can combine (i) the small-scale resolution required to accurately simulate fault-zone processes with (ii) the large overall physical volume required to simulate large earthquake sources and compute surface ground motion at distances of engineering interest. The project engages both earth and computational scientists and trainees to address these modeling challenges. The project team is testing the computer models by comparing the ground motion predictions from large suites of simulations with comparable compilations from actual earthquake recordings. For example, the distributions (including median and statistical spread) of ground motion parameters such as spectral acceleration and peak ground velocity, as functions of event magnitude, site distance, and other variables, are among the targets of these observational tests. Those computer models that can be validated in the above sense are then used to (i) simulate earthquake shaking from future large earthquake scenarios, (ii) develop improvements to simplified modeling methods for ground shaking (the so-called kinematic methods), and (iii) improve the empirical ground motion models that are conventionally used in engineering design, by providing a physics-based extrapolation beyond the range in which they have significant support from data (i.e., to large magnitude and small source-to-site distances).

大地震是罕见的，复杂的事件，其来源是深处的，无法直接观察。此外，对于非常大的事件，即那些对生命安全和建筑环境构成最大潜在威胁的地震，几乎没有近乎源的强劲运动记录。 验证了充分的计算机模拟提供了一种基于最佳可用地震物理和波浪传播模型的大地震的强烈地面运动的方法。模拟可以帮助满足对基于绩效的工程和结构分析的适当地面震动估算的紧迫需求，鉴于美国西部城市非常高的建筑物的建设繁荣，这一要求尤其急切。计算机模拟对于我们对地震的基本科学理解也至关重要，因为它们揭示了很难通过实验或传统的理论分析来研究的较小互动的大规模影响。 该项目正在开发数值地震模型，该模型代表断层的主要机械和热过程，包括通过加热岩石接触和孔隙液的加压来减弱摩擦电阻。 这些计算机模型还包含了断层粗糙度和地球应力状态的既定统计表示，以及地质材料的强度极限（将上限放在压力波干扰的振幅上，而断层的振幅）。这些型号必须在大型计算机簇（即具有数千个处理器核心的型号）上有效运行，以便它们可以结合（i）（i）准确模拟故障区域工艺所需的小规模分辨率，并与（ii）较大的整体物理体积需要模拟大地震来源并在工程兴趣的距离内计算地面地面运动。该项目与地球和计算科学家和学员都互动，以应对这些建模挑战。项目团队正在通过比较大型模拟套件的地面运动预测与实际地震记录的可比汇编来测试计算机模型。例如，这些观察测试的目标之一是地面运动参数（包括光谱加速度和峰值接地速度）的分布（包括中位数和统计扩散），例如光谱加速度和峰值地面速度，作为事件幅度，位点距离和其他变量的函数。然后，那些可以在上述意义上进行验证的计算机模型被用来（i）模拟地震从未来的大地震场景中摇晃，（ii）对简化的建模方法进行改进，以进行地面摇动（所谓的运动学方法）和（（ iii）通过提供基于物理学的外推超出数据（即大量和小源到位点距离）的大量支持的范围，改善了工程设计中常规使用的经验地面运动模型。