Collaborative Research: Seismic cycles and earthquake nucleation on heterogeneous faults: Large-scale laboratory experiments, numerical simulations, and Whillans ice stream

合作研究：非均质断层上的地震周期和地震成核：大规模实验室实验、数值模拟和惠兰斯冰流

• 批准号: 2240375
• 负责人: Gregory McLaskey
• 金额: $ 44.63万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-15 至 2026-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2240375&HistoricalAwards=false
• 关键词: Collaborative; Research; Seismic; cycles; earthquake

According to well-established theory, earthquakes may start with very slow movement (or "slip") along a fault, which suddenly accelerates to the violently rapid slip that can generate ground shaking. Slow slip has been seen before large earthquakes, but it is usually different from what the theories predict. Dr. McLaskey and his team will use laboratory experiments and computer models to measure and understand slow slip and tiny earthquakes that happen along faults before a large earthquake. In the laboratory experiments, a ten-foot slab of rock with a cut (fault) embedded in it is compressed and sheared using a giant press, making the fault creep and then slip suddenly in "laboratory" earthquakes. The experiments can test how realistic, non-uniform fault properties—like rough versus slippery sections, or bumps and bends—can play a role in providing warning signs of an impending earthquake. Computer models will be developed to understand and explain data collected during the laboratory earthquake experiments. To check how well these computer models perform, they will be tested against a large collection of data on slow pre-earthquake slip and earthquakes that are ocurring beneath a glacier in Antarctica. As part of this project, three graduate students and at least two undergraduates will receive training in earthquake science (experiments, modeling, and data analysis).Heterogeneous fault properties—bumps, bends, differing lithology, and heterogeneous loading conditions that exist at a variety of scales—are generally not considered in earthquake nucleation theories, but have been shown to strongly influence the way an earthquake initiates. On a heterogeneous fault, neighboring fault patches reach failure at different times, often resulting in the propagation of slow slip fronts that may only be detectable as a gradual decrease in seismic coupling, such as that observed prior to the M 9 Tohoku Earthquake, or from the migration and coalescence of microseismicity. This project explores the behavior of heterogeneous faults late in the earthquake cycle including the propagation of slow slip fronts and their interaction with strong/unstable asperities. These mechanisms may transform models of the way earthquakes initiate and better inform the interpretation of precursory activity. This project employs meter-scale laboratory experiments, where heterogeneous fault properties are imposed at specific locations and the effects on earthquake nucleation and triggering by slow slip fronts are studied in detail. Additionally, theoretical and numerical models for slow slip propagation on heterogeneous faults are developed to extend the laboratory results to length scales and conditions more relevant to natural earthquakes. The models are then tested against a field-scale glacial stick-slip cycle at Whillans Ice Stream, an Antarctic glacier, where aseismic transients affect 100 km-scale glacial stick-slip events and exhibit behavior similar to that observed in the lab.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.

根据公认的理论，地震可能始于沿着断层的非常缓慢的运动（或“滑动”），然后突然加速到剧烈的快速滑动，从而产生地面震动。在大地震之前就已经出现过慢滑动，但这种情况是存在的。通常与理论预测不同。麦克拉斯基博士和他的团队将使用实验室实验和计算机模型来测量和理解大地震前沿断层发生的慢滑移和微小地震。有切口的岩石使用巨大的压力机对嵌入其中的（断层）进行压缩和剪切，使断层蠕变，然后在“实验室”地震中突然滑动。这些实验可以测试真实的、不均匀的断层特性，例如粗糙与光滑的部分或凸起。和弯曲——可以在提供即将发生的地震的警告信号方面发挥作用，将开发计算机模型来理解和解释实验室地震实验中收集的数据，为了检查这些计算机模型的性能，将对它们进行大量的测试。数据缓慢南极洲冰川下发生的震前滑动和地震作为该项目的一部分，三名研究生和至少两名本科生将接受地震科学培训（实验、建模和数据分析）。异质断层特性 - 碰撞。 、弯曲、不同的岩性以及存在于多种尺度的异质荷载条件——通常在地震成核理论中不予考虑，但已被证明会影响地震的发生方式在异质断层上，相邻断层块在不同时间达到破坏，通常会导致慢滑锋的传播，这种传播只能通过地震耦合的逐渐减弱来检测，例如在 M 9 东北地震之前观察到的情况，或来自微震活动的迁移和合并，该项目探讨了地震周期后期异质断层的行为，包括慢滑锋的传播及其与强/不稳定粗糙体的相互作用。这些机制可能会改变地震发生方式的模型，并更好地解释前兆活动。该项目采用米级实验室实验，在特定位置施加异质断层特性，并研究慢滑锋对地震成核和触发的影响。此外，还开发了非均质断层上缓慢滑移传播的理论和数值模型，以将实验室结果扩展到与自然地震更相关的长度尺度和条件，然后针对现场规模的冰川进行测试。南极冰川 Whillans Ice Stream 的粘滑循环，其中地震瞬变影响 100 公里规模的冰川粘滑事件，并表现出与实验室观察到的行为类似的行为。该奖项反映了 NSF 的法定使命，并被认为值得支持通过使用基金会的智力优点和更广泛的影响审查标准进行评估。