Seismic and aseismic slip in faults with rock gouge using a 3D laboratory earthquake setup: the effect of fluid injection rate

流体在震源过程中起着关键作用。大量的观测表明流体与断层活动之间有着密切的联系。这在自然事件和人类活动引起的地震中观察到，例如碳封存，地热能开采以及与石油和天然气开采有关的废水处理。在这里，研究人员调查了流体注入和地震反应之间的关系。 这种响应的范围从缓慢的地震滑动（无地震）到不稳定的地震滑动（地震）。 他们使用高度仪器化的实验室设置，包括故障模拟，允许故障响应的3-D可视化。 用高速摄影机拍摄了失稳滑动的时间序列。 在断层界面处记录流体注入速率和压力。最先进的台架实验有助于从根本上了解流体在断层活动中的作用。他们提供了关键的实验测量验证的3-D数值代码模拟流体诱发地震活动。 该项目为早期职业科学家，研究生和本科生提供支持，并促进对高中和初中学生及其教师的推广。其成果改进了地震危险评估，特别是与人类活动有关的评估。该项目由地球物理计划和构造计划共同资助。 在这里，实验室实验产生摩擦破裂触发高度控制的流体注射在3-D标本。模拟的故障可以主机的范围内的破裂行为，从缓慢的滑动所有的方式，以充分的动态响应。动态破裂自发地沿沿着摩擦界面传播，滑动速率约为0.1-10 m/s;该范围与天然地震高度相关。3-D试样和设置允许测试低与快注射速率可以导致稳定与不稳定滑动行为的假设。实验功能岩凿接口嵌入在由聚合物材料，聚甲基丙烯酸甲酯（PMMA）制成的标本。 这种材料很容易以散装形式获得，并使3D样品的生产成为可能。使用聚合物作为模拟材料产生了几个优点，包括它们的小成核尺寸，用于不稳定的滑移，以及透明性，这在这里是必不可少的。该团队能够在高细节水平上密切监测断层行为，从而能够探索和量化缓慢滑动和动态破裂之间的联系。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Fluids play a key role in earthquake source processes. A large body of observations has shown the close connection between fluids and faulting. This is observed in natural events and in earthquakes induced by human activities, such as carbon sequestration, geothermal energy extraction, and wastewater disposal associated with oil and gas extraction. Here the researchers investigate the relation between fluid injection and the resulting seismic response. This response ranges from slow aseismic slip (no earthquake) to unstable seismic slip (earthquake). They use a highly instrumented laboratory setup comprising fault analogs which allow 3-D visualization of fault responses. Time sequences of unstable slips are captured by a high-speed camera. Fluid injection rate and pressures are recorded at the fault interface. The state-of-the-art bench top experiments contribute to the fundamental understanding of the role of fluids in faulting. They provide critical experimental measurements for the validation of 3-D numerical codes modeling fluid induced seismicity. The project provides support for an early-career scientist, graduate and undergraduate students, and fosters outreach toward high-school and middle-school students and their teachers. Its outcomes improve earthquake hazard assessment, notably related to human activities. The project is co-funded by both the Geophysics program and the Tectonics program. Here, the laboratory experiments produce frictional ruptures triggered by highly controlled fluid injection in 3-D specimens. The simulated fault can host a range of rupture behavior, ranging from slow slip all the way to fully dynamic response. Dynamic ruptures spontaneously propagate along a frictional interface with slip rates of the order of 0.1-10 m/s; this range is highly relevant to natural earthquakes. 3-D specimens and setup allow testing the hypothesis that low vs. fast injection rate can result in stable vs. unstable slip behavior. The experiments feature rock gouge interfaces embedded in specimens made of a polymeric material, poly-methyl-methacrylate (PMMA). This material is readily available in bulk form and makes possible the production of 3-D samples. Using polymers as analog materials yields several advantages, including their small nucleation sizes for unstable slip, and transparency, which are here essential. The ability to closely monitor the fault behavior at a high level of detail enable the team to explore and quantify the connection between slow slip and dynamic rupture.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.