Three-dimensional spontaneous dynamic rupture models on geometrically complex faults with state-of-the-art frictional parameterization

具有最先进摩擦参数化的几何复杂断层的三维自发动态破裂模型

• 批准号: 0838464
• 负责人: David Oglesby
• 金额: $ 17.19万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-15 至 2012-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838464&HistoricalAwards=false
• 关键词: Three; dimensional; spontaneous; dynamic; rupture

Dynamic spontaneous earthquake rupture models have proven themselves to be valuable tools to investigate the physics of earthquakes and to help predict ground motion. These numerical models start from basic assumptions about material structure, frictional behavior, and fault geometry, and calculate the spatiotemporal evolution of fault slip (and often the resultant near-source ground motion). Such dynamic models typically use either laboratory-derived friction laws or realistically complex fault geometry, but not both. The researchers propose to bring dynamic earthquake modeling an important step forward by combining these two separate tracks: they will use laboratory-derived friction laws to model spontaneous rupture propagation and slip on faults with realistically complex geometry. They expect to obtain first-order effects in rupture propagation, slip, and ground motion that will differ from previous modeling efforts, leading to both a better understanding of the earthquake process and better predictions of faulting behavior and ground motion. Dynamic earthquake models have historically followed two tracks: 1) investigations of the effect of frictional parameterization and stress pattern on simple planar faults, and 2) investigations of the effects of fault geometry on the earthquake process, using simple frictional parameterizations. the PIs will combine these two tracks to produce a new generation of dynamic earthquake models. Data from laboratory experiments at high slip rates and theoretical models imply that at the high slip rates observed during earthquakes, the typical rate-and-state frictional formulation must be modified to incorporate a greater degree of weakening over a larger length scale. Additionally, research on faults with complex, asymmetrical geometry shows that temporal variation of normal stress, which is inevitable on non-planar faults, can have a significant effect on rupture dynamics. To correctly model both these aspects of faulting behavior, they will develop a modern frictional parameterization and use it to model the behavior of geometrically complex faults, such as systems with stepovers and branches. The new 3D finite element method that will incorporate a new, realistic method for off-fault stress relaxation, which is necessary to avoid pathological stress buildup on such fault systems. These important ingredients of earthquake physics have never before been combined in a single modeling method, and the result of such a combination will be a state-of-the art tool to model the physics of earthquakes. The researchers will address important questions about the behavior of faults at stepovers and branches, including determining if there are general rules for how to predict rupture path at branches, and the ability of rupture to span stepovers.The proposed research will have important implications for both earthquake science and the broader scientific and educational community. A key use of the modeling method will be to gain insight into the potential size of earthquakes on geometrically complex fault systems, such as those in the Los Angeles region. Many fault systems are bounded by geometrical features such as fault gaps and changes in segment orientation; the proposed numerical models will help determine the circumstances under which earthquake rupture may propagate across these segment boundaries, and generate larger earthquakes with larger ground motion. In addition, the proposed research will lead to better estimates of the slip distribution and rupture front evolution, which also strongly affect ground motion. The resulting improved earthquake source models can help in the probabilistic assessment of earthquake size and ground motion pattern, with subsequent potential impacts on seismic hazard and building code and design.

动态自发地震破裂模型已证明自己是研究地震物理学并帮助预测地面运动的有价值工具。 这些数值模型始于关于材料结构，摩擦行为和断层几何形状的基本假设，并计算断层滑移的时空演化（通常是所得的近源地面运动）。 这种动态模型通常使用实验室衍生的摩擦定律或现实的复杂断层几何形状，但并非两者兼而有之。 研究人员建议通过结合这两个单独的轨道来使动态地震建模一步：他们将使用实验室衍生的摩擦定律来对自发的破裂传播进行建模，并以现实复杂的几何形状在断层上滑落。 他们期望在破裂的传播，滑动和地面运动中获得一阶影响，这将与以前的建模工作不同，从而更好地了解地震过程，也可以更好地预测断层行为和地面运动的预测。动态地震模型从历史上遵循了两条轨道：1）对摩擦参数化和应力模式对简单平面断层的影响的研究，以及2）使用简单的摩擦参数化研究了断层几何形状对地震过程的影响。 PI将结合这两个轨道，以产生新一代的动态地震模型。实验室实验的数据以高滑动速率和理论模型表明，在地震期间观察到的高滑动速率时，必须修改典型的速率和状态摩擦配方，以纳入更大程度的削弱长度尺寸。 此外，对具有复杂，不对称几何形状的故障的研究表明，正常应力的时间变化（在非平面断层上都是不可避免的）会对破裂动力学产生重大影响。 为了正确地对故障行为的这两个方面进行建模，它们将开发现代的摩擦参数化，并使用它来建模几何复杂的故障的行为，例如带有Stepover和分支的系统。 新的3D有限元方法将结合一种新的，现实的方法，以避免过错压力放松，这对于避免在此类断层系统上避免病理压力是必要的。 这些地震物理学的这些重要成分从来没有以单个建模方法结合在一起，这种组合的结果将是建模地震物理学的最先进的工具。 研究人员将解决有关在Stepover和分支机构中故障行为的重要问题，包括确定是否有有关如何预测分支机构破裂路径的一般规则，以及破裂的能力跨越了阶梯范围。该拟议的研究将对地震科学和更广泛的科学和教育社区具有重要意义。 建模方法的关键用途是深入了解几何复杂断层系统（例如洛杉矶地区的地震的潜在大小）。 许多故障系统都受到几何特征的限制，例如故障差距和段方向的变化；提出的数值模型将有助于确定地震破裂可能在这些段边界传播的情况，并以较大的地面运动产生更大的地震。 此外，拟议的研究将导致对滑动分布和破裂前进化的更好估计，这也强烈影响地面运动。 最终改善的地震源模型可以帮助对地震大小和地面运动模式的概率评估，并随后对地震危害，建筑法规和设计产生潜在影响。