Collaborative Research: Investigating Structure and Seismicity Within the Southern M9.2 1964 Great Alaska Earthquake Rupture Area Using a Dense Node Array

合作研究：使用密集节点阵列调查 1964 年 M9.2 大地震破裂区域南部的结构和地震活动

• 批准号: 2207441
• 负责人: Catherine Grace Barcheck
• 金额: $ 17.54万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2207441&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Structure; Seismicity; Collaborative; Research; Investigating; Structure; Seismicity

A subduction zone is a region where an oceanic plate slips below a continental plate, along a shallowly inclined fault. One example is the Alaska-Aleutian subduction zone, which is responsible for more Magnitude 8 or greater earthquakes than any other subduction zone in the world, among them the 1964 Magnitude 9.2 Great Alaska Earthquake. Kodiak Island lies just above part of the Alaska-Aleutian subduction zone fault that was responsible for the 1964 earthquake, and in 2019, 400 seismic instruments were deployed there for 25 days as part of the Alaska Amphibious Community Seismic Experiment (AACSE). Using machine learning and other techniques, Worthington and her team will re-analyze data collected by these instruments to identify numerous very small earthquakes, and pinpoint their locations. This will provide an unprecedented snapshot of how earthquakes are distributed along the subduction zone fault and its vicinity. Recordings of these and other earthquakes will be used together to generate images of the subsurface, including the subduction zone fault itself, and to estimate physical properties of the fault and its surroundings. Detailed characterization of seismicity and structure within shallow subduction forearc regions offers insight into plate interface properties along the seismogenic megathrust, and the distribution, location and kinematics of active and past deformation. This project characterizes seismicity and structure beneath Qikertaq (Kodiak Island) using existing data from a densely-spaced seismic node array deployed along a ~50 km transect as part of the Alaska Amphibious Community Seismic Experiment (AACSE) in May, 2019. The Kodiak node array is located within the southern asperity of the largest historical US earthquake, the M9.2 1964 Great Alaska event, which ruptured a 600-800 km section of the Alaskan subduction zone. The main goals of the project are to determine: 1) The distribution of upper plate vs lower plate vs interface seismicity during the interseismic cycle through increased microseismicity (M1.0) detection and relocation; 2) The nature of the plate interface in the shallow forearc of the southern 1964 earthquake rupture asperity, properties of which control earthquake rupture, propagation and initiation; 3) Upper plate velocity structure within the Kodiak region, providing constraints on material strength and elastic properties of the seaward portion of the forearc. Using both machine-learning and coalescence-based automatic detection algorithms, this project will produce an enhanced seismicity catalog for the duration of the 25-day deployment. The locations of existing and new detections will be refined to provide a snapshot of the distribution of seismicity during the interseismic interval following great megathrust earthquakes. Travel-times from active-source marine shots and local earthquakes (including newly detected events) will be used for raytracing and inversion to develop a high-resolution velocity model of the shallow forearc above the plate interface. This velocity model will, in turn, be used to further refine event locations. Energy from local earthquakes will be used for imaging the crust and plate interface below the node array using scattered waves and reflected phases for vertical reflection profiling and coda auto-correlation.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.

俯冲带是一个区域，海洋板在大陆板下方滑动，沿着浅倾斜的断层滑动。一个例子是阿拉斯加 - 亚利亚人的俯冲带，它比世界上任何其他俯冲区更大的8或更大地震，其中1964年的9.2级9.2阿拉斯加地震。科迪亚克岛位于阿拉斯加 - 阿拉斯加俯冲带的一部分上方，该区域导致了1964年地震，2019年，作为阿拉斯加两栖动物社区地震实验（AACSE）的一部分，在那里部署了400种地震仪器25天。使用机器学习和其他技术，沃辛顿和她的团队将重新分析这些乐器收集的数据，以识别许多非常小的地震，并确定其位置。这将提供一个前所未有的快照，说明如何在俯冲带断层及其附近分布地震。这些和其他地震的记录将共同用于生成地下图像，包括俯冲区故障本身，并估计断层及其周围环境的物理特性。对浅俯冲前臂区域内的地震性和结构的详细表征可洞悉沿地震源性巨质的板界面特性，以及主动变形和过去变形的分布，位置和运动学。该项目的特征是，Qikertaq（Kodiak Island）下方的地震性和结构使用来自阿拉斯加两栖动物社区地震实验（AACSE）的一部分，使用沿一个约50 km prrancect部署的密集的地震节点阵列（AACSE）在2019年5月。事件，在阿拉斯加俯冲带的600-800公里处破裂。该项目的主要目标是确定：1​​）在微观震动度（M1.0）检测和搬迁过程中，在跨板上的上板与下板与界面地震性的分布； 2）南部1964年地震破裂的浅牙中板界面的性质，控制地震破裂，繁殖和启动的特性； 3）板速度结构内部的板速度结构，对前臂的材料强度和弹性特性提供了限制。使用基于机器学习和基于合并的自动检测算法，该项目将在25天部署的期限内产生增强的地震目录。现有检测和新检测的位置将被完善，以提供大量大型地震后的瞬间间隔期间地震性分布的快照。活动源海洋镜头和局部地震（包括新检测到的事件）的旅行时间将用于射线跟踪和反转，以开发板界面上方的浅牙前固体的高分辨率速度模型。此速度模型反过来将用于进一步完善事件位置。当地地震中的能量将用于对节点阵列下方的地壳和板界面进行成像，并使用散射波和反射阶段进行垂直反射概况和CODA自动相关。这项奖项反映了NSF的法定任务，并已通过评估该基金会的知识分子功能和广泛的影响来评估NSF的法定任务。