Observations and Modeling of Shallow Fault Creep Along the San Andreas Fault Zone

非常精确的地面运动测量被用来研究沿着圣安德烈亚斯断层（SAF）系统的断层缓慢蠕变的分布和大小。断层蠕变的测量和建模提高了我们对地震危险性和地震物理学的认识。大部分蠕变信号都靠近断层，因此，一种名为干涉合成孔径雷达（InSAR）的天基技术最能观测到蠕变信号，因为它具有50米的空间分辨率。这项研究的新方面是使用最近发射的ALOS航天器（JAXA）的l波段InSAR数据。l波段干涉图比以前可用的c波段干涉图在更长的时间间隔内保持相干。这些新数据在加利福尼亚中部和北部尤其重要，因为c波段永久散射方法在测量缓慢的地壳变形方面只是部分成功。为期三年的调查包括以下任务：(1)参加北美西部InSAR联盟（WInSAR），收集调查所需的数据，并为未来加州的地震事件做准备。(2)分析ERS-1/2、ENVISAT和ALOS的InSAR数据，恢复沿SAF系统的缓慢地震间蠕变信号。研究人员正在改进叠置ERS和ENVISAT干涉图的方法，并开发用于分析l波段ALOS数据的新软件。(3)利用断层蠕变测量来提高我们对浅层断层摩擦物理模型的理解。特别是分析揭示了蠕变速率、浅层应力积累速率和大地震复发间隔之间的关系。这些拟议的研究活动有助于实现NSF的目标。通过提供断层力学和地震危险的见解。资金将主要用于支持研究生的研究和培训。这项研究与日本和欧洲航天局的科学家进行了重要的国际合作。研究人员还与斯克里普斯海洋学研究所（SIO）可视化中心合作，对图像、动画和3d可视化进行编目和分发。教育活动包括在加州大学圣地亚哥分校开设研究生和本科课程，并向当地学校团体介绍地震主题。

Very precise measurements of ground motion are being used to study the distribution and magnitude of slow creep along faults of the San Andreas Fault (SAF) system. Measuring and modelling fault creep is improving our understanding of both earthquake hazard and earthquake physics. Much of the creep signal is close to the fault and therefore, best observed by a space-based technique called Interferometric Synthetic Aperture Radar (InSAR) because of its complete 50-m spatial resolution. The new aspect of this research is the use of L-band InSAR data from the recently launched ALOS spacecraft (JAXA). L-band interferogram remain coherent over longer time intervals than the previously available C-band interferograms. These new data are especially important in central and northern California where C-band permanent scattering methods are only partially successful in measuring slow crustal deformation. The three-year investigation includes the following tasks: (1) Participate in the Western North America InSAR consortium (WInSAR) to assemble the data needed for this investigation as well as to prepare for future seismic events in California. (2) Analyze InSAR data from ERS-1/2, ENVISAT, and ALOS to recover slow inter-seismic creep signals along the SAF system. The investigators are refining methods for stacking ERS and ENVISAT interferograms, as well developing new software for the analysis of L-band ALOS data. (3) Use the measurements of fault creep to improve our understanding of physical models for fault friction at shallow depth. In particular the analysis is revealing the relationship between creep rate, shallow stress accumulation rate, and major earthquake recurrence intervals.These proposed research activities are contributing to the objectives of NSF?s EarthScope Initiative by providing insight into fault mechanics and earthquake hazard. Funding will primarily be used to support graduate student research and training. This research has significant international collaboration with scientists at the Japanese and European Space Agencies. The researchers are also collaborating with the Scripps Institution of Oceanography (SIO) Visualization Center in cataloging and distributing images, animations, and 3-D visualizations. Educational activities include development of graduate and undergraduate courses at UCSD and presentations to local school groups on earthquake topics.