EAR-PF: Active Tectonics and Crustal Structure of Northern Alaska

EAR-PF：阿拉斯加北部的活动构造和地壳结构

• 批准号: 2052839
• 负责人: Bryant Chow
• 金额: $ 17.4万
• 依托单位: Chow, Bryant
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2052839&HistoricalAwards=false
• 关键词: EAR; PF; Active; Tectonics; Crustal

Dr. Bryant Chow has been awarded an NSF EAR Postdoctoral Fellowship to investigate the question of why earthquakes occur where they do. This work will take place at the University of Alaska Fairbanks under the mentorship of Dr. Carl Tape. The Earth’s crust is the outermost shell where all human activity takes place. Fractured into many tectonic plates, the crust hosts disastrous events, such as earthquakes, tsunamis, and volcanic eruptions, near its surface. Earthquakes typically occur where two or more plates meet, but they can also occur far from plate boundaries. The processes that cause these earthquakes are not well understood. This project seeks to characterize Earth’s crustal structure, linking deep-Earth processes with surface geological activity to explore why earthquakes occur where they do. The work will investigate plate tectonic processes and crustal structure in northern Alaska, an understudied region far from plate boundaries that has hosted M4 earthquakes. The goal is to characterize earthquakes and develop high-resolution models of the crust in order to understand how tectonic forces are transferred far into the interior of plates. Although population density in northern Alaska is low, earthquake hazard remains important for infrastructure, environmental, and industrial purposes and is critical for development in the region. Alaska’s North Slope is a major oil producing region for the United States, and northeastern Alaska is home to the largest national wildlife refuge in the country. This project involves outreach to local communities in northern Alaska using novel teaching tools to convey earthquake risks and hazards. Additionally, Dr. Chow will produce a comprehensive catalog of models that can be used for characterizing earthquake hazard. This project proposes a detailed seismotectonic investigation of northern Alaska to constrain mechanisms controlling tectonics in and around the region. Northern Alaska features diffuse seismicity and large-scale deformation far from the plate boundaries. However, the structures and processes involved are not well understood. Due to its remoteness, difficulties in mapping and monitoring of northern Alaska have resulted in historically sparse coverage. This changed following the deployment of the EarthScope Transportable Array in Alaska, with years of high-quality seismic data now available for a comprehensive study. This project involves investigation of two scientific questions: Are deformation and structure in northeastern Alaska consistent with (1) far field deformation from plate convergence 1000 km away? and (2) extrusional extension of western Alaska? This work will advance understanding of how global geodynamic processes shape continental scale tectonics and relate to regional deformation and local seismicity, using waveform cross-correlation techniques and 3D numerical waveform simulations. Detection and re-location of seismicity will be followed by inversion of seismic moment tensors to constrain fault structure and deformation characteristics. Waveform simulations will be used to validate existing tomography models of northern Alaska and for subsequent full-waveform tomography, which will result in high-resolution structural models of the crust and upper mantle. Ambient noise adjoint tomography will provide a velocity model of northern Alaska with resolution on the order of tens of km. A subsequent earthquake adjoint tomography inversion will refine a northeastern subset of this model, resulting in km scale resolutions. The success of these tasks will lead to refined earthquake catalogs, high resolution velocity models, and detailed interpretations of tectonic processes for northern Alaska.This project is jointly funded by the EAR Postdoctoral Fellowship program, the Established Program to Stimulate Competitive Research (EPSCoR), and the EAR Geophysics program.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.

布莱恩特·周（Bryant Chow）博士被授予NSF耳朵博士后奖学金，以调查为什么发生地震的问题。这项工作将在卡尔录音带博士的心态下在阿拉斯加的Fairbanks大学举行。地壳是所有人类活动都发生的最外壳。地壳被破裂成许多构造板，围绕着灾难性事件，例如地震，海啸和火山喷发，附近的地面。地震通常发生在两个或多个板相遇的地方，但也可能发生远离板边界。引起这些地震的过程尚不清楚。该项目旨在表征地球的地壳结构，将深地球过程与地面地质活动联系起来，以探讨为什么地震发生在它们的位置。这项工作将研究阿拉斯加北部的板块构造过程和地壳结构，这是一个远离板块边界的远处的区域。目的是表征地震和开发地壳的高分辨率模型，以了解如何将构造力转移到板内部。尽管阿拉斯加北部的人口密度较低，但地震危害对于基础设施，环境和工业目的仍然很重要，对于该地区的发展至关重要。阿拉斯加的北坡是美国的主要生产地区，阿拉斯加东北部是该国最大的国家野生动物保护区的所在地。该项目涉及使用新颖的教学工具向阿拉斯加北部的当地社区推广，以传达地震风险和危害。此外，Chow博士将生成全面的模型目录，可用于表征地震危险。该项目建议对北阿拉斯加进行的详细地震调查限制控制该地区及其周围构造的机制。阿拉斯加北部具有弥漫性地震性和远离板边界的大规模变形。但是，所涉及的结构和过程尚不清楚。由于其偏远，绘制和监视北阿拉斯加的难度导致历史上稀疏的覆盖范围。在阿拉斯加的Earthscope可运输阵列部署后，情况发生了变化，现在有多年的高质量地震数据可用于全面研究。该项目涉及两个科学问题的投资：阿拉斯加东北部的变形和结构是否与（1）距离（1）远离1000公里外的板收敛远处的野外变形？ （2）阿拉斯加西部的延伸延伸？这项工作将通过波形互相关技术和3D数值波形模拟来促进对整体地球动力学如何塑造连续规模的构造构造构造构造构成构造构造的理解。地震性的检测和重新定位将随后反转地震矩张量，以限制断层结构和变形特征。波形模拟将用于验证北阿拉斯加的现有层析成像模型和随后的全波断层扫描，这将导致地壳和上地幔的高分辨率结构模型。环境噪声伴奏层析成像将提供阿拉斯加北部的速度模型，并以数十亿公里的命令分辨率。随后的地震伴随断层扫描倒置将完善该模型的东北子集，从而导致km量表分辨率。这些任务的成功将导致精致的地震目录，高分辨率速度模型以及对北阿拉斯加构造过程的详细解释。该项目由Ear Postdoctoral奖学金计划共同资助。基金会的智力优点和更广泛的影响评论标准。

项目成果

Strong Upper‐Plate Heterogeneity at the Hikurangi Subduction Margin (North Island, New Zealand) Imaged by Adjoint Tomography

• DOI: 10.1029/2021jb022865
• 发表时间: 2022-01
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: B. Chow;Y. Kaneko;C. Tape;R. Modrak;N. Mortimer;Stephen Bannister;John Townend

Evidence for Deeply Subducted Lower‐Plate Seamounts at the Hikurangi Subduction Margin: Implications for Seismic and Aseismic Behavior

• DOI: 10.1029/2021jb022866
• 发表时间: 2021-07
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: B. Chow;Y. Kaneko;John Townend