2005 Interior of the Earth Gordon Conference

2005年地球内部戈登会议

• 批准号: 0531095
• 负责人: Lars Stixrude
• 金额: $ 2.35万
• 依托单位: Gordon Research Conferences
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2006-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0531095&HistoricalAwards=false
• 关键词: 2005; Interior; Earth; Gordon; Conference

The actual physical process of an earthquake-the propagating fracture that breaks the friction holding two sides of the fault together allowing them to slip past one another-is never directly observed. It must be inferred by analysis of the elastic waves and the deformation that the earthquake caused. The data from the MW 6.0 Parkfield earthquake of September 28, 2004, provide an unprecedented opportunity to infer the dynamics of an earthquake source. Within 20 km of the fault, there are 56 three-component strong motion accelerographs, a dense 13-element array (UPSAR), 13 continuous GPS sites with 10 or more GPS campaign sites and four borehole dilatometers. These data can be inverted to find the kinematic description of the earthquake source. The kinematic description lays the foundation for describing the nonlinear process of earthquake dynamics. The mechanics of inverting data have become routine, but the scientific questions that the Parkfield data can answer go beyond simply finding a kinematic faulting model. Inverting all of the data to find a "best" model of the faulting process will be done, but this data set provides a much greater opportunity. The richness of the data allows a multifaceted approach to inverting the data. Most importantly, the density and quality of the data allow a rare opportunity to explore what features of the kinematic models are robust and well resolved. The kinematic features that are robust will define features of the earthquake that will be vital for establishing the best initial stress conditions for developing dynamical models that will simulate the propagating fracture. There are many fundamental questions that will be addressed. Why did the 2004 rupture go from southeast to northwest, opposite to that of the 1934 and 1966 earthquakes? With minor perturbations to the initial stress conditions could the rupture have nucleated near Middle Mountain and propagated to the southeast? Even though the rupture is primarily northwest, what caused the large ground motions to the southeast? Do they arise from dynamics of the rupture front? It has been proposed that maps of b-values on the fault correlate with regions of high and low stress on the fault. The 2004 mainshock hypocenter is within a region of high stress. Will the dynamic rupture follow a path that mimics the b-value maps? What will dynamic models give for stress changes on different parts of the fault? Will the variation be as large as that found in studies of prior seismicity. The answers depend on dynamics of the rupture. By inverting the abundant Parkfield data, a kinematic model is deduced that will provide the initial conditions for dynamic simulations, which in turn will allow one of the most detailed examinations of the dynamics of an earthquake.

地震的实际物理过程--断裂的传播打破了断层两侧的摩擦力，使它们相互滑动--从来没有被直接观察到。它必须通过分析弹性波和地震引起的变形来推断。2004年9月28日帕克菲尔德6.0级地震的数据为推断震源动力学提供了前所未有的机会。在距断层20 km范围内，有56个三分量强震加速度计，一个密集的13元阵列（UPSAR），13个连续的GPS站点，10个或更多的GPS活动站点和4个钻孔地震仪。这些数据可以被反演以找到震源的运动学描述。运动学描述是描述地震动力学非线性过程的基础。反演数据的机制已经成为常规，但帕克菲尔德数据可以回答的科学问题不仅仅是找到一个运动断层模型。将颠倒所有数据以找到断层过程的“最佳”模型，但该数据集提供了更大的机会。数据的丰富性允许多方面的方法来反转数据。最重要的是，数据的密度和质量允许一个难得的机会来探索运动学模型的哪些功能是强大的和良好的解决。强大的运动学特征将定义地震的特征，这些特征对于建立最佳初始应力条件以开发模拟传播断裂的动力学模型至关重要。 有许多基本问题将得到解决。为什么2004年的破裂方向是从东南向西北，与1934年和1966年的地震方向相反？在初始应力条件有微小扰动的情况下，断裂是否可能在中山附近成核并向东南传播？尽管断裂主要是西北方向的，是什么导致了东南方向的巨大地面运动？它们是由破裂前缘的动力学引起的吗？有人提出，断层上的b值图与断层上的高应力和低应力区域相关。2004年主震震源位于高应力区。动态破裂会沿着一条模仿b值图的路径吗？动力学模型会给出断层不同部分的应力变化吗？这种变化是否会像先前地震活动性研究中发现的那样大？答案取决于断裂的动力学。通过反演丰富的Parkfield数据，推导出一个运动学模型，该模型将为动态模拟提供初始条件，这反过来又将允许对地震动力学进行最详细的检查。