Static and Dynamic Triggering of Fault Creep on Strike-Slip Faults

2010年El Mayor-Cucapah MW7.2级地震是过去18年来袭击加利福尼亚州南部的最大地震。它在南加州索尔顿海槽的许多断层上引发了浅层蠕动，使其在过去42年中至少第八次发生在当地或地区性地震中。然而，断层蠕变的触发机制及其对地震危险性和断层力学的影响仍然知之甚少。该项目的主要目标是通过分析大地测量数据，并在速率和状态摩擦的框架内模拟静态和动态的触发过程，来开发改进的断层蠕动视图。研究人员首先将通过开发可处理数千张InSAR图像的自动蠕变检测器来构建改进的断层蠕变数据集，其结果稍后将与现有的蠕变仪和现场调查数据集整合。其次，他们将使用附近地震造成的真实静态和动态振动作为应力扰动，对2D平面断层模型进行应力扰动，该模型具有沿深度和走向的速率和状态摩擦特性变化。这些参数最终可用于地震危险性的计算。通过为大型断层系统开发最先进的模型和最全面的蠕变事件数据集，他们希望从对断层蠕变的概念性理解过渡到对在特定断层上产生蠕变事件的条件的定量、预测性理解。该项目将提高我们对断层浅部力学的理解，这对农业和经济上重要的地区索尔顿海槽未来地震预计的震动/危险程度具有重大影响。自动瞬变探测器是此类探测器中的第一个，将激励新的探测器将模式识别应用于大地测量数据。

The 2010 El Mayor-Cucapah Mw 7.2 earthquake was the largest earthquake to strike southern California in the last 18 years. It triggered shallow creep on many faults in Salton Trough, Southern California, making it at least the 8th time in the last 42 years that a local or regional earthquake has done so. However, the triggering mechanism of fault creep and its implications for seismic hazard and fault mechanics remain poorly understood. The main goal of this project is to develop an improved view of fault creep by analyzing geodetic data and modeling the triggering process, both static and dynamic, in the framework of rate-and-state friction. The investigators will first construct an improved fault creep dataset by developing an automatic creep detector that can process thousands of InSAR images, whose results will later be integrated with the existing creepmeter and field survey datasets. Second, they will use realistic static and dynamic shaking due to nearby earthquakes as stress perturbations to a 2D planar fault model with rate-and-state frictional property variations both in depth and along strike. These parameters can eventually be used in the calculation of seismic hazard. By developing both state of the art models and the most comprehensive dataset of creep events for a large fault system, they hope to transition from a conceptual understanding of fault creep towards a quantitative, predictive understanding of the conditions that create creep events on particular faults. This project will improve our understanding of the mechanics of the shallow portions of faults, which has significant implications for the shaking/hazard levels expected from future earthquakes in the Salton Trough, an agriculturally and economically important area. The automatic transient detector is one of the first of its kind and will inspire new detectors applying pattern recognition on geodetic data.