ER-PF: Using Distributed Acoustic Sensing for Tremor Detection and Site Characterization in Cascadia to Evaluate Earthquake Hazard

该奖项全部或部分根据2021年美国救援计划法案（公法117-2）资助。Manuel门多萨博士已被授予博士后奖学金，在科罗拉多大学博尔德分校和科罗拉多矿业学院开展研究和教育计划。门多萨博士计划开发一种新的地震监测技术，称为分布式声学传感（DAS）。DAS使用黑暗（未照明/未使用）现有的电信光纤电缆，并将其变成一种仪器，作为一个网络，能够检测微小或遥远的地震事件。在美国的太平洋西北部，两个构造板块交汇，条件适合大地震，这可能导致其他危险，如海啸。 因此，需要进行大规模和连续的地震监测，以评估即将发生的风险。在这个项目中，门多萨博士将与Anne Sheehan教授和Ge Jin博士一起工作，通过在华盛顿西北部进行DAS实验来测试和演示DAS的性能。具体来说，这项工作将调查被称为“震颤”的地震事件，并确定当地地质条件如何沿光纤电缆沿着变化。门多萨博士的工作将促进对地震的理解，地面如何对地震作出反应，以及随之而来的地震危险。拟议的研究将为DAS提供机会，使其与现有的地震网络一起在更大的规模上应用，以进行多学科和跨学科的研究和监测地球过程。该项目还将使门多萨博士能够教授和指导来自代表性不足群体的学生，包括在科罗拉多矿业学院担任多样性、包容性和准入委员会的导师，以及在科罗拉多博尔德大学担任暑期实习导师。与该项目相关的其他活动包括设计和领导一个地方DAS实验的物理学课程和监督专业和教育发展的本科生谁将进行原始研究与DAS数据。在这两个校区，PI将参与旨在提高公众科学素养和扩大参与S.T.E.M领域的外展活动。分布式声学传感（DAS）使用光纤测量地球地震扰动引起的变形（应变），近年来，已被证明是一个非常适用和有前途的地震学工具。这是由于它能够被配置为具有数十公里量级的孔径、米级传感器（即通道）间距以及与传统宽带地震仪相当的性能的地震阵列。这意味着DAS阵列可以覆盖大面积区域，同时在对地震波场进行采样时不会受到空间混叠的影响-与传统网络不同-并提供经常被错过的高保真新信息。因此，一个单一的DAS实验可以用来同时调查发生在不同的空间和时间尺度的各种地球过程。在这里，研究人员将使用现有电信电缆的光纤在卡斯卡迪亚进行第一个已知的DAS实验，以监测震颤并描述现场条件，以评估地震危险性。具体而言，PI将追求三个主要科学目标：（1）使用DAS检测和定位卡斯卡迪亚的震颤;（2）表征其时空行为，并推断其对板块界面上倾锁定部分的作用;（3）确定DAS阵列沿着场地条件的米级变化。这些目标将通过采用基于地震阵列的技术来实现，例如波束形成和波束反投影来捕获震颤，以及环境噪声干涉测量技术来估计顶部30米（Vs 30）的剪切波速度。 将本研究获得的结果与使用不同仪器和方法进行的其他观察结果进行比较，以证明DAS在改善卡斯卡迪亚地震和地面震动模型方面的有效性，并评估其对各种构造环境中未来实验的影响。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的评估来支持。影响审查标准。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Dr. Manuel Mendoza has been granted an EAR Postdoctoral Fellowship to carry out research and education plans at University of Colorado Boulder and Colorado School of Mines. Dr. Mendoza plans to develop a new technique for earthquake monitoring called distributed acoustic sensing (DAS). DAS uses dark (unlit/unused) existing telecommunication fiber optic cables and turns them into an instrument that acts as a network capable of detecting tiny or distant seismic (earthquake) events. In the Pacific Northwest of the US where two tectonic plates converge, the conditions are right for large earthquakes which could result in other hazards such as tsunamis. Therefore, large-scale and continuous seismic monitoring is needed to evaluate the impending risks. In this project, Dr. Mendoza will work alongside Professors Anne Sheehan and Dr. Ge Jin to test and demonstrate DAS performance capabilities by carrying out a DAS experiment in Northwestern Washington. Specifically, the work will investigate seismic events known as “tremor” and determine how local geologic conditions vary along the fiber cable. Dr. Mendoza’s work will advance understanding of earthquakes, how the ground shakes in response to them, and consequent seismic hazards. The proposed study will provide opportunities for DAS to be applied at larger scales alongside existing seismic networks to perform multi and interdisciplinary research and monitoring of Earth processes. The project will also allow Dr. Mendoza to teach and mentor students from underrepresented groups, including as a mentor on the Diversity, Inclusion, and Access committee at the Colorado School of Mines and as a summer internship mentor at University of Colorado Boulder. Other activities associated with this project include designing and leading a local DAS experiment for a geophysics course and supervising the professional and educational development of an undergraduate student who will conduct original research with the DAS data. At both campuses, the PI will engage in outreach activities aimed at increasing public scientific literacy and broadening participation in the S.T.E.M fields.Distributed acoustic sensing (DAS) using fiber-optics to measure deformation (strain) caused by seismic perturbations in the Earth has, in recent years, proved to be a highly applicable and promising tool in seismology. This is owed to its ability to be configured as a seismic array with an aperture on the order of tens of kilometers, meter-level sensor (i.e. channel) spacing, and performance comparable to that of conventional broadband seismometers. This implies that DAS arrays can blanket a large area while not suffering from spatial aliasing when sampling the seismic wavefield – unlike traditional networks – and provide new information in high fidelity that often goes missed. A single DAS experiment can therefore be used to simultaneously investigate a variety of Earth processes occurring across different spatial and temporal scales. Here, the investigators will conduct the first known DAS experiment in Cascadia using fiber from an existing telecommunication cable, to monitor tremor and characterize site conditions for the purpose of evaluating seismic hazard. Specifically, the PI will pursue three primary scientific goals: (1) Use DAS to detect and locate tremor in Cascadia; (2) characterize its spatiotemporal behavior and infer its contribution to stressing the up-dip locked portion of the plate interface; and (3) determine meter-level variation in site conditions along the DAS array. These goals will be addressed by employing seismic array-based techniques such as beamforming and beam back-projection to capture tremor, as well as ambient noise interferometry techniques to estimate shear wave velocities of the top 30 meters (Vs30). The results obtained from this study will be compared to other observations performed using different instruments and methods, to demonstrate the efficacy of DAS in improving earthquake and ground shaking models in Cascadia and assess its implications for future experiments in a variety of tectonic settings.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.