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.

最大的地震和相关的海啸以及火山喷发都是在俯冲带发现的，在那里一个构造板块潜入另一个板块之下。北美的一个突出例子是阿拉斯加半岛近海的俯冲带，现代有记录以来最大的一些地震就发生在那里，比如1938年的大地震和1964年毁灭性的威廉王子9.2级地震。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，而且变化很快。然而，关于俯冲带产生大地震的能力，许多问题仍然没有得到回答。该项目将分析和解释2018-2019年作为美国国家科学基金会-GeoPRISMS资助的阿拉斯加两栖社区地震实验(AACSE)的一部分而收集的地震记录。由密集的近海和陆上地震仪阵列记录的地震数据将使人们能够开发这一俯冲带深达100公里的地质结构和物理性质的三维图像。图像的质量将足以检查以前提出的解释该地区和世界其他俯冲带板块边界地震行为变化的结构。该项目支持两名研究生的培训。将根据AACSE两栖地震台阵记录的受控震源和当地地震数据，对P波和S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：阿拉斯加半岛边缘在孕震性质、地震间隔期的地震活动性和板块耦合方面的分段在多大程度上受上大陆板块结构、成分和(或)下行大洋板块物理性质和结构(如海山、弯曲断层和断裂带)沿走向和向下倾斜的变化控制？三维地震速度模型将被用来研究进入俯冲带的水的沿走向的变化，以及假定的水化大洋地幔的深度范围，以及水是否被输送到可能影响大地震带地震性质的地震孕育深度。通过绘制沿板块界面的地震速度异常图，将审查板块界面起伏和海山链、隆起和断裂带等俯冲构造异常的存在(或不存在)，以及它们在大地测量推断的板块界面锁定中对破裂分段和变化的推定作用。加强对与大地震有关的俯冲带过程的了解，对于评估阿拉斯加半岛俯冲带的地震和海啸危害很重要。虽然这个项目聚焦于阿拉斯加半岛俯冲带，但这个科学问题适用于世界各地的许多俯冲带。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。