Collaborative Research: Incoming plate and forearc structure of the Semidi and SW Kodiak Segments offshore Alaska Peninsula from 3-D active-source and local earthquake tomography

合作研究：阿拉斯加半岛近海塞米迪和西科迪亚克段的传入板块和弧前结构，来自 3D 主动源和当地地震层析成像

• 批准号: 1947758
• 负责人: Anne Becel
• 金额: $ 31万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-04-01 至 2024-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1947758&HistoricalAwards=false
• 关键词: Collaborative; Research; Incoming; plate; forearc

The largest earthquakes and associated tsunamis as well as volcanic eruptions are found at subduction zones where one tectonic plate dives beneath another. A prominent example in North America is the subduction zone offshore of the Alaska Peninsula, where some of the largest earthquakes ever recorded in modern times have occurred, like the great earthquake of 1938 and the devastating 1964 M9.2 Prince William earthquake. In this region the history of large and small earthquakes and how strongly the two plates are locked together vary substantially and rapidly along the margin. Many questions, however, remain unanswered about the ability of the subduction zone to generate large earthquakes. This project will analyze and interpret recordings of earthquakes that were collected as part of a larger NSF-GeoPRISMS funded Alaska Amphibious Community Seismic Experiment (AACSE) in 2018-2019. The seismic data, recorded by a dense array of offshore and onshore seismometers, will allow the development of a three-dimensional image of the geological structure and physical properties of this subduction zone down to a depth of 100 km. The quality of the images will be high enough to examine structures that have been previously proposed to explain changes in the seismic behavior of the plate boundary in this area and at other subduction zones worldwide. The project supports the training of two graduate students.Three-dimensional seismic tomography studies will be conducted of P- and S-wave structure based on controlled-source and local earthquake data recorded by the AACSE amphibious array. The project will address the following key question: To what extent is the segmentation of the Alaska Peninsula margin in seismogenic properties, seismicity during the interseismic period, and plate coupling controlled by along-strike and downdip variations in upper continental plate structure, composition, and/or downgoing oceanic plate physical properties and structures such as seamounts, bending faults and fracture zones? The 3-D seismic velocity models will be used to investigate along-strike variations in water input into the subduction zone, as well as depth extent of the presumed hydrated oceanic mantle and whether or not water is delivered to seismogenic depths where it could influence megathrust seismic properties. By mapping seismic velocity anomalies along the plate interface, the plate interface relief and the presence (or lack thereof) of subducted structural anomalies such as seamounts chains, swell and fracture zones, and their presumed role in contributing to rupture segmentation and variations in the geodetically inferred plate interface locking, will be examined. An improved understanding of subduction zone processes associated with large earthquakes is important for assessing earthquakes and tsunami hazards at the Alaska Peninsula subduction zone. Although this project focuses on the Alaska Peninsula subduction zone, the scientific question applies across many subduction zones worldwide.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.

最大的地震和相关海啸以及火山喷发发生在一个板块潜入另一个板块下方的俯冲带。北美的一个突出例子是阿拉斯加半岛近海的俯冲带，这里曾发生过一些现代有记录以来最大的地震，例如 1938 年的大地震和 1964 年毁灭性的 M9.2 威廉王子地震。在该地区，大地震和小地震的历史以及两个板块锁定在一起的强度沿边缘变化很大且迅速。然而，有关俯冲带产生大地震的能力的许多问题仍未得到解答。该项目将分析和解释地震记录，这些记录是 2018-2019 年 NSF-GeoPRISMS 资助的阿拉斯加两栖社区地震实验 (AACSE) 的一部分收集的地震记录。由一系列密集的海上和陆上地震仪记录的地震数据将有助于绘制该俯冲带深度达 100 公里的地质结构和物理特性的三维图像。图像的质量将足够高，以检查先前提出的结构，以解释该地区和全球其他俯冲带板块边界的地震行为的变化。该项目支持培养两名研究生。将根据AACSE两栖阵列记录的受控源和当地地震数据，对纵波和横波结构进行三维地震层析成像研究。该项目将解决以下关键问题：阿拉斯加半岛边缘的发震特性、震间期地震活动以及上大陆板块结构、成分和分布的沿走向和下倾变化控制的板块耦合在多大程度上被分割。 /或下行海洋板块的物理特性和结构，例如海山、弯曲断层和断裂带？ 3D地震速度模型将用于研究俯冲带中水输入的沿走向变化，以及推测的水合洋地幔的深度范围，以及水是否被输送到可能影响巨型逆冲的地震深度。地震特性。 通过绘制沿板块界面的地震速度异常图，板块界面起伏和俯冲结构异常的存在（或缺乏），例如海山链、隆起和断裂带，以及它们在导致破裂分段和大地测量变化中的假定作用推断板接口锁定，将进行检查。更好地了解与大地震相关的俯冲带过程对于评估阿拉斯加半岛俯冲带的地震和海啸灾害非常重要。尽管该项目的重点是阿拉斯加半岛俯冲带，但该科学问题适用于全球许多俯冲带。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。