4D Imaging of Oceanic Transform Fault Material Properties Variations During the Earthquake Cycle

许多具有破坏性的大地震发生在人口密集的地区，如印度尼西亚、日本、智利和加利福尼亚。因此，预测地震及其影响是地震学长期追求的目标。实现这些目标需要提高对导致大地震的断层和断层过程的理解。这种理解被大多数断层和断层系统的极端复杂性所削弱。虽然海洋转换断层并不发生在人口稠密的地区，但它们是相对简单的自然实验室，在那里已经观察到一些基本的过程。东太平洋隆起的转换断层为研究断层性质的时空变化如何控制地震破裂提供了一个独特的机会，因为这些断层上的最大地震发生的间隔是有规律的，并且断层性质的相关变化已经被观察到。这个项目有三个目标，将推进我们对断层力学的理解。一是确定哪些材料特性的空间变化控制了最大地震的发生。二是了解断裂带性质在地震周期中如何随时间变化，三是了解材料性质的变化与地震活动性的关系。该项目更广泛的影响包括支持两名年轻的博士后研究人员；主要的更广泛的影响是，虽然它不直接关注地震危害估计，但可能会导致对地震过程的更好理解，因此具有很高的潜在社会效益。

Many large and damaging earthquakes occur in highly populated areas, such as Indonesia, Japan, Chile and California. For that reason, forecasting earthquakes, and predicting their effects is a long-sought goal of earthquake seismology. Achieving those goals requires improved understanding of the faults and fault processes that lead to large earthquakes. That understanding is impaired by the extreme complexity of most fault and fault systems. Though they do not occur in populated areas, oceanic transform faults are comparatively simple natural laboratories, where some fundamental processes have been observed. Transform faults on the East Pacific Rise (EPR) offer a unique opportunity to study how spatial and temporal variation of fault zone properties control earthquake rupture because the largest earthquakes on these faults occur at regular intervals, and related variations of the properties in the fault zone have been observed. This project has three objectives that will advance out understanding of fault mechanics. One is to determine which spatial variations of material properties control the occurrence of the largest earthquakes. The second is to understand how fault zone properties change with time over the earthquake cycle, and the third is to understand how variations of the material properties are related to earthquake seismicity.The broader impacts of this project include support for two young post doctoral researchers; the primary broader impact is that, while it is not directly focused on seismic hazard estimates, may be expected to lead to a better understanding of earthquake processes, with accordingly high potential societal benfits.