The role of strike-slip fault interaction on long-term slip rates

对地震危险性的准确估计取决于对地壳中承载地震的活动断层的位置和这些活动断层上的载荷的了解。加载速度较快的断层比加载速度较慢的断层能够发生更频繁的地震。当过去的地震记录被用来估计未来的断层活动时，断层上未来的负荷被假设为与过去相同。然而，在具有紧密间隔的活动断层的区域中，例如加州，断层可以相互作用，使得局部载荷不是随时间恒定的。该项目将使用物理实验室实验来模拟地壳断层的生长。虽然新断层的形成和旧断层的废弃通常需要数十万年的时间，但同样的过程可以在实验装置中在几个小时内复制。这使得能够直接观察和记录随着系统发展而发生的故障的局部负载变化。这项研究将产生模拟实验室实验的数字模型，并利用地壳的特性，以复制地球内部的相同过程。本研究的结果将显示沿沿着的哪些区域更可能经历局部载荷的变化。这次调查的信息可以指导我们如何使用过去地震的记录来估计未来地震的危害。该项目小组包括妇女、第一代大学生和残疾人。该团队将通过几项指导、外联和科学传播工作，加强多元化STEM劳动力的发展，提高科学素养和公众参与度。这些努力包括教学推广计划，为马萨诸塞大学地质力学YouTube频道开发教学视频，并指导聋人和重听地质科学家和学术专业人士。活动断层的地震危险评估依赖于对其长期滑动速率的估计。这些评估假定，从地质记录中确定的长期滑动率可以可靠地用于预测未来的地震灾害。然而，这种假设只有在活动断层具有恒定的长期滑动速率时才有效。在走滑断层系统承载具有不规则几何形状的多个活动断层的情况下，系统的重组（例如通过新断层段的生长）可能影响沿沿着断层的滑动速率。地质滑动记录并不总是能够描述随时间推移的滑动行为，这些记录也不能揭示滑动速率变化的过程。因此，需要从物理和数值实验中直接观察断层系统的演化，以表征驱动长期滑动速率变化的过程。为了评估断层重组对长期滑动速率的作用，本项目将使用比例物理实验直接观察断层系统演化并记录滑动行为。不同的断层配置和不同的模拟材料的实验将被缩放，以模拟广泛的地壳断裂条件，并允许直接评估断层滑动响应断层的相互作用和重组。数值模型将通过与实验数据的比较进行基准测试和验证，并将利用地壳流变学和尺度来告知长期滑动速率行为，以响应走滑断层重组和相互作用。这些实验将揭示断层系统固有的驱动机制，这些机制可以导致断层滑动速率的时间变化以及这些机制作用的时间跨度。这些物理和数值实验的结果将有助于评估地质滑动率记录的相对可靠性，以估计未来的滑动率在不同的结构位置沿着走滑future.This奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Accurate estimates of earthquake hazards depend on knowledge of both the location of active faults in the Earth's crust that host earthquakes and the loading on those active faults. Faults with faster loading are capable of more frequent earthquakes than faults with slower loading. When records of past earthquakes are used to estimate future fault activity, future loading on the fault is assumed to be the same as the past. However, in regions with closely spaced active faults, such as California, faults can interact so that the local loading is not constant through time. This project will use physical laboratory experiments to mimic the growth of faults in the Earth’s crust. While hundreds of thousands of years are typically required for new faults to develop and old faults to be abandoned, the same processes can be replicated within hours in an experimental apparatus. This enables direct observation and documentation of the variations in local loading on faults that happens as a system evolves. This research will produce numerical models that simulate laboratory experiments and use properties of the Earth’s crust in order to replicate the same processes acting within the Earth. Results from this study will show which regions along faults are more likely to experience changes in local loading. Information from this investigation can guide how we use records of past earthquakes to estimate hazards of future earthquakes. The project team includes women, first generation college students, and persons with disabilities. This team will strengthen the development of a diverse STEM workforce and increase scientific literacy and public engagement, through several mentoring, outreach and science communication efforts. These efforts include teaching outreach programs, developing instructional videos for the UMass Geomechanics YouTube channel and mentoring deaf and hard of hearing geoscientists and academic professionals.Seismic hazards assessments of active faults rely on estimates of their long-term slip rates. These assessments presume that long-term slip rates determined from the geologic record can be reliably used to forecast future seismic hazards. However, this presumption is only valid if active faults have constant long-term slip rates. Where strike-slip fault systems host multiple active faults with irregular geometry, reorganization of the system, such as via the growth of new fault segments, may impact slip rates along nearby faults. Geologic slip records cannot always characterize slip behavior through time, nor can these records reveal the processes responsible for slip rate variations. Therefore, direct observations of fault system evolution from physical and numerical experiments are needed to characterize the processes that drive variations in long-term slip rates. In order to assess the role of fault reorganization on long-term slip rates, this project will use scaled physical experiments to directly observe fault system evolution and document slip behavior. Experiments with different fault configurations and different analog materials will be scaled to simulate a wide range of crustal faulting conditions and permit direct assessment of fault slip response to fault interaction and reorganization. Numerical models will be benchmarked and validated by comparisons to experimental data, and will utilize crustal rheology and scale to inform long-term slip rate behavior in response to strike-slip fault reorganization and interaction. The experiments will reveal the array of driving mechanisms intrinsic to a fault system that can contribute to temporal variations in fault slip rate and the time spans over which these mechanisms act. The findings from these physical and numerical experiments will help to evaluate the relative reliability of geologic slip rate records in order to estimate future slip rates at different structural locations along strike-slip faults.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.