An Investigation into Time-Dependent Fault Zone Properties at Seismogenic Depth on the San Andreas Fault near Parkfield

该奖项是根据2009年美国复苏和再投资法案（公法111 - 5）资助的。该项目的目的是提高我们对地震成核过程的理解，通过贡献更好的地震学约束的时间依赖的断层带性质在孕震深度。加州帕克菲尔德密集井孔地震仪网络提供的大量高质量地震数据的可用性，为阐明地下断层带特性的详细视图提供了机会。我们寻求开发新的方法，以利用众多的识别序列的特征重复地震，并确定三个时间相关的性质在孕震深度：1）断层带强度，2）流变行为，和3）滞弹性模型的内部断层带。该项目将探索重复地震序列震源性质的时间变化，作为断层强度变化的代表，以更好地了解随时间变化的断层强度对断层变形力学和地震成核过程的作用。我们寻求显着扩大重复地震活动性数据，以允许大大提高时空分辨率的断层强度沿着圣安德烈亚斯断层。该项目的其他重点将包括了解深度处随空间和时间变化的流变特性，并对2004年帕克菲尔德6级地震后震后期间狭窄断层核内的瞬态或系统性结构变化进行成像。该项目将调查孕震深度处随时间变化的断层带强度，这将影响地震的触发和排序。利用加州帕克菲尔德密集的钻孔地震仪网络积累的大量已识别重复地震。该项目的其他活动将探讨断层带流变特性的时空变化，并将描述地震后变形期间断层带中心核的时间变化，以便更全面地了解随时间变化的断层带特性对地震成核过程的作用。该项目将通过改进对地下时间相关断层带特性的了解，直接有助于改进对圣安德烈亚斯断层地震潜力的估计。该项目的成果将用于当地社区和组织的地震减灾工作。该项目将包括一名研究生的教育和研究。

This award is funded under the American Recovery and Reinvestment Act of2009 (Public Law 111-5). This project aims to improve our understanding of the nucleation process of earthquakes by contributing better seismological constraints of time-dependent fault zone properties at seismogenic depth. The availability of a large number of high-quality seismic data from a dense borehole seismograph network at Parkfield, California introduces opportunities for unraveling detailed view of subsurface fault-zone properties. We seek to develop new approaches to take advantage of numerous identified sequences of characteristic repeating earthquakes, and to determine three time-dependent properties at seismogenic depth: 1) fault-zone strength, 2) rheological behaviors, and 3) anelastic model of the inner fault zone. The project will explore temporal variations in source properties of repeating earthquake sequence as a proxy for changes in fault strength to gain a better understanding of the role of time-dependent fault strength on the mechanics of fault deformation and the earthquake nucleation process. We seek to significantly expand repeating seismicity data to allow for much improved spatiotemporal resolution of fault strength along the San Andreas Fault. The other focuses of this project will involve understanding space- and time-varying rheological properties at depth and imaging transient or systematic structural changes within the narrow fault core in the postseismic period following the 2004 M6 Parkfield earthquake.This project will investigate time-varying fault-zone strength at seismogenic depth that will effect the triggering and sequencing of earthquakes, by taking the advantage of the numerous identified repeating earthquakes accumulating from a dense borehole seismograph network at Parkfield, California. The other activities of this project will explore spatiotemporal variations in fault-zone rheological properties and will characterize temporal changes in the central core of fault zone in postseismic deformation period, in order to gain a more comprehensive picture of the role of time-varying fault zone properties on the earthquake nucleation process. The project will directly contribute improved estimates of earthquake potential on the San Andreas Fault by improved knowledge of subsurface time-dependent fault zone properties. Results from the project will be used in earthquake hazard mitigation efforts by local communities and organizations. The project will include the education and research of a graduate student.