Kinematics and Dynamics of Time-dependent Slip Along the Central Creeping Segment of the San Andreas Fault

圣安德烈亚斯断层(CSAF)的中央非地震滑动段是一个独特的天然实验室，可以详细研究无地震断层滑动的运动学和动力学。大地测量和地震资料表明，CSAF的行为具有强烈的时间依赖性，包括慢地震的发生，几年来滑动速率的变化，以及对区域应力变化的复杂响应。该项目(1)刻画了无震断层滑动在空间和时间上的模式，以更好地了解下伏断裂带过程的物理过程；(2)利用区域应力场细微变化引起的滑动变化的敏感性，更好地约束断层的本构性质；(3)利用无震断层滑动对下地壳变形性质的敏感性，提高我们对下地壳流变性的理解。这项工作包括一个观测程序，以解决CSAF上空间可变和时间相关的断层滑动的运动学问题，以及一个理论建模程序，以允许在断层机械过程、断层相互作用和流变学的背景下解释滑动模式。无震断层滑动的时空运动学是根据横跨CSAF的空间大地测量数据，通过对沿断层的微震分布和活动的观测，以及对历史形变数据的分析得出的。这些运动学信息构成了使用基于过程的建模技术分析CSAF动力学的基础，以解决一些基本研究问题，包括(1)随时间变化的无震滑动的行为范围，(2)滑动瞬变与应力边界条件细微变化的关系，(3)断裂带的本构性质，以及(4)反映在浅层滑动分布中的下地壳的流变性及其较长期的时间变化。

The central, aseismically-slipping segment of the San Andreas fault (CSAF) represents a unique natural laboratory allowing detailed investigations of the kinematics and dynamics of aseismic fault slip. Geodetic and seismic data show that the CSAF behaves in a strongly time-dependent fashion including the occurrence of slow earthquakes, variations of slip rates over several years, and a complex response to regional stress changes. This project (1) characterizes the patterns of aseismic fault slip in space and time to better understand the physics of the underlying fault zone processes, (2) utilizes the sensitivity of slip variations from subtle changes in the regional stress field to better constrain the fault's constitutive properties, and (3) benefits from the sensitivity of aseismic fault slip to the nature of lower crustal deformation to improve our understanding of the rheology of the lower crust. The effort includes an observational program to resolve the kinematics of spatially variable and time dependent fault slip on the CSAF and a theoretical modeling program to allow for interpretation of the slip patterns in the context of fault mechanical processes, fault interaction and rheology. The spatio-temporal kinematics of aseismic fault slip are deduced from space geodetic data spanning the CSAF, from observations of micro-earthquake distribution and activity along the fault, and from analysis of historic deformation data. The kinematic information forms the foundation of an analysis of the dynamics of the CSAF using process-based modeling techniques to address a number of fundamental research problems including (1) the range of behaviors of time dependent aseismic slip, (2) the relationship of slip transients to subtle changes in stress boundary conditions, (3) fault zone constitutive properties, and (4) the rheology of the lower crust reflected in the shallow slip distribution and its longer-term variation in time.