Faulting Process from Top to Bottom Along the San Andreas Fault in the San Juan Bautista Region

了解断裂带周围时空变化的变形场对于理解活动构造、断层相互作用和大地震的发生至关重要。该项目集中在加利福尼亚州的圣胡安包蒂斯塔地区，该地区断层结构的复杂性和各种时变慢滑（地震）现象使其成为一个完美的天然实验室，可以研究从地球表面顶部到深处的活动断层过程。该地点还具有吸引力，因为它拥有丰富的历史数据集和最近部署的EarthScope仪器，包括连续GPS站、应变仪和地震仪。项目团队正在分析该地区的大地测量和地震数据，并将它们整合起来，以解释断裂过程的底层结构和机制。蠕变仪、应变仪、GPS和InSAR数据约束了上地壳断层滑动的四维分布模型。从重复地震中推断出的地表以下深处的地震滑动信息补充了大地测量数据。此外，非火山震颤的发作暗示了次发震深度的变形瞬变。由于断层滑动与断裂带岩石和相邻地壳块体的力学特性有关，研究小组还利用接收函数分析来评估地壳特性随时间的变化。这些不同的数据集提供了在断裂带不同深度范围内发生的地震和地震滑动之间相互作用的宝贵信息。这一工作的结果对地震断层滑动瞬变在地震发生和聚集中的作用提供了深入的认识。对地震滑动瞬变过程及其与区域应变异常的关系的进一步了解，以及对地震周期模型的改进，可能有助于改进地震预报和中长期预报。

Understanding of the spatially and temporally varying deformation field around fault zones is critically important for understanding active tectonics, fault interaction and the occurrence of large earthquakes. This project is focused on the San Juan Bautista area of California, where the complexity of the fault structure and a variety of time-varying slow-slip (aseismic) phenomena make a perfect natural laboratory to study active faulting processes from the top of the Earth's surface to great depth. The site is also attractive because of the availability of a rich historic data set and the recent deployment of EarthScope instrumentation, including continuous GPS stations, strainmeters and seismometers.The project team is analyzing geodetic and seismic data in this region and integrating them to interpret the underlying architecture and mechanics of the faulting process. Creepmeter, strainmeter, GPS, and InSAR data constrain models of the four-dimensional distribution of fault slip in the upper crust. The geodetic data are complemented by information on aseismic slip deep below the surface inferred from repeating earthquakes. Furthermore, episodes of non-volcanic tremor hint at deformation transients at sub-seismogenic depths. Because fault slip is tied to the mechanical properties of the fault zone rocks and adjoining crustal blocks, the team is also evaluating changes in crustal properties through time using receiver-function analysis.These diverse data sets provide valuable information on the interactions between earthquakes and aseismic slip that occurs in various depth ranges in the fault zone. Results from this work provide insight into the role of aseismic fault slip transients in earthquake occurrence and clustering. Improved understanding of aseismic slip transients, their relation to regional strain anomalies, and improved models of the earthquake cycle may help to improve earthquake forecasts and intermediate to longer-term predictions.