EAR-PF: Towards a robust understanding of the spatio-temporal evolution of foreshock sequences from the laboratory to the field

该奖项的全部或部分资金来自《2021年美国救援计划法案》(公法117-2)。David C.Bolton被授予NSF EAR博士后奖学金，研究地震前震序列在时间和空间上的演变，通过天然和实验室断裂带进行探索。估计未来地震的时间和地点一直是地震学研究中的一个长期目标。然而，由于对地震起源和地震活动之间的联系缺乏了解，这一领域的进展缓慢。前震是在主震之前发生的小地震，被认为是断层接近破裂的间接证据。然而，前震并不是所有地震的一个容易观察到的特征，它们与即将到来的地震之间的联系也没有得到很好的理解。这项工作将结合实验室和现场对前震的观测，目的是提供对前震序列演化的连贯了解。一个重要的重点将致力于调查前震属性是否编码了有关主震大小的信息。这项工作将为地震的准备阶段提供关键的见解，并将有助于推进地震预警系统和改进地震危险评估。该项目还将与德克萨斯大学奥斯汀分校杰克逊地球科学学院领导的GeoFORCE推广计划合作，为德克萨斯州西南部代表性不足的社区提供研究机会。该项目将实施新的机器学习和地震地震学技术，以开发丰富的小震级地震的高保真地震目录。这些高分辨率的目录将阐明前震是如何相互作用的，它们在空间和时间上的演变，以及它们与主震的联系。该项目将利用配有声发射监测的实验室实验，阐明驱动前震序列的起因过程。断裂带属性，如应力、滑动位移、应变，将与声发射的时空模式相结合，从而能够详细了解地震成核过程和地震活动之间的物理联系。该项目的第二个关键要素将涉及通过探测和定位意大利亚平宁断裂系统上具有良好特征和地震活动的前震，扩大实验室观测以适应地质相关条件。这一多尺度的综合研究计划代表着从实验室到构造尺度研究地震过程的独特机会，并将决定实验室前震的特征是否可以扩大到构造断裂带。这项拟议的工作对地震危险性分析具有重要影响，并有助于提高我们对地震过程做出准确的危险预测和科学预测的能力。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Dr. David C. Bolton has been awarded an NSF EAR Postdoctoral Fellowship to investigate the evolution of earthquake foreshock sequences in time and space, explored through natural and laboratory fault zones. Estimating the timing and location of future earthquakes has been a long-standing goal in the study of seismology. However, progress in this area has been slow due to a poor understanding of the connections between the origins of earthquakes and seismic activity. Foreshocks are small earthquakes that precede the main earthquake and are thought to be indirect evidence that a fault is close to failure. However, foreshocks are not an easily observed feature of all earthquakes, and their connection to the impending earthquake is not well understood. This work will integrate laboratory and field-based observations of foreshocks with an aim to provide a coherent understanding of the evolution of foreshock sequences. A significant focus will be devoted to investigating whether foreshock properties encode information about the mainshock size. This work will provide key insights into the preparatory phase of earthquakes and will help advance earthquake early warning systems and improve earthquake hazard assessment. The project will also join forces with the GeoFORCE outreach program led by the Jackson School of Geosciences at UT-Austin to provide research opportunities to underrepresented communities in southwest Texas. This project will implement novel machine learning and earthquake seismology techniques for developing high-fidelity earthquake catalogs that are rich in small magnitude events. These high-resolution catalogs will illuminate how foreshocks interact with each other, their evolution in space and time, and their connection to the mainshock. The project will utilize laboratory experiments instrumented with acoustic emission monitoring to shed light on the causative processes that drive foreshock sequences. Fault zone properties such as stress, slip displacement, strain, will be integrated with the spatio-temporal patterns of acoustic emissions, allowing for a detailed understanding of the connection between the physics of earthquake nucleation processes and seismic activity. A second key element of the project will involve scaling up the laboratory observations to geologically relevant conditions by detecting and locating foreshocks on the well-characterized and seismically active Apennine fault system in Italy. This multi-scale, integrated research plan represents a unique opportunity to study seismic processes from the laboratory to tectonic scale and will determine if characteristics of laboratory foreshocks can be scaled up to tectonic fault zones. The proposed work has important implications for seismic hazard analysis and could help improve our ability to make accurate hazard forecasts and scientific predictions about earthquake processes.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.