Collaborative Research: NSFGEO-NERC: Advancing capabilities to model ultra-low velocity zone properties through full waveform Bayesian inversion and geodynamic modeling

合作研究：NSFGEO-NERC：通过全波形贝叶斯反演和地球动力学建模提高超低速带特性建模能力

• 批准号: 2341237
• 负责人: Michael Thorne
• 金额: $ 56.04万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-04-01 至 2027-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2341237&HistoricalAwards=false
• 关键词: Collaborative; Research; NSFGEO; NERC; Advancing

This proposal will improve the description of features called Ultra-Low Velocity Zones (ULVZs). ULVZs are thin patches of material that sit on the Earth’s core-mantle boundary (CMB), which is at a depth of 2891 km (1796 miles). As their name implies, ULVZs slow passing seismic waves by as much as 50%. This makes which makes them some of the most anomalous features of the Earth’s interior. Several ULVZs are beneath some of Earth’s largest hot spot volcanoes, such as Hawaii, Iceland, and Samoa. Imaging of the Earth’s interior shows that hot rising materials, or mantle plumes, connect these volcanoes from ULVZs to the surface. But the origin, lifetime, size, and composition of these ULVZs are not known, nor is their role in the formation of the mantle plumes. This project will provide greater details as to where these features exist, their formation and composition. This work analyzes two types of seismic waves sensitive to thin ULVZ layering that interact with and bounce off these ULVZ features. The study focuses on an area beneath the western Pacific Ocean because of extensive seismic data coverage and known ULVZs in the region. The project will create a new seismic database built from public records and networks in South Korea, Taiwan, and Japan. This database will then enable imaging of ULVZ structures at the CMB using modern statistical capabilities. Computer simulations of mantle flow will help interpret the formation, motion, and role in mantle processes of the ULVZs. This project includes an annual outreach STEM event for K-8 students for the local Utah Pacific Island community. This event will include activities to teach about the mantle plumes that form Pacific Islands through hot spot volcanism.Ultra-Low Velocity Zones (ULVZs) are structures with strongly reduced seismic velocities at Earth’s core-mantle boundary (CMB) which have been associated with or linked to hot-spot volcanism, Large Igneous Provinces, core-mantle interaction, downwelling subduction and Large-Low Velocity Provinces (LLVPs) and thus are a critical component of global mantle dynamics. ULVZs are typically studied using waveform analysis of ULVZ-sensitive seismic probes (e.g., SPdKS, ScP, ScS), but previous studies suffer from large uncertainties in ULVZ parameters due to modeling trade-offs and lack a geophysical inference of ULVZs through rigorous parameter estimation. This project will develop a transformative waveform inversion approach and apply it to characterize ULVZ properties including their seismic velocities, density, size, and shape. Specifically, the project will (1) collect a new database of ULVZ-sensitive ScP and PcP waveforms utilizing publicly available seismic array data as well as new data from South Korea, Taiwan, Japan, and the International Monitoring System (IMS) arrays, (2) advance capabilities for full waveform Bayesian inversion for ULVZ properties to quantitatively distinguish regions with and without ULVZ structures (i.e., Bayesian model selection), and to perform joint inversion of ScP and PcP waveforms, (3) quantify the waveform effects from 2-D/3-D ULVZ structures, (4) search for additional, previously unlooked-for arrivals in the ScP wavefield consistent with 3-D ULVZ structure using array processing approaches, and (5) relate observed ULVZ localities and properties to lowermost mantle flow and dynamics through 3D geodynamic models. This is a collaborative proposal between scientists at the University of Utah, Arizona State University, and Leeds University, and is therefore co-funded by the National Science Foundation (NSF) and the United Kingdom’s Natural Environment Research Council (NERC).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.

该提案将改善称为超低速度区（ULVZ）的特征的描述。 Ulvz是位于地球核心壳边界（CMB）上的薄材料，其深度为2891公里（1796英里）。顾名思义，UlvzS慢速传播地震波的速度高达50％。这使它们成为地球内部最异常的特征。几个Ulvz在地球上一些最大的热点火山下方，例如夏威夷，冰岛和萨摩亚。地球内部的成像表明，将这些火山从Ulvzs连接到地表，表明这些火山将这些火山连接起来。但是这些Ulvz的起源，寿命，大小和组成尚不清楚，它们在地幔羽的形成中也不是其作用。该项目将提供有关这些特征的存在，它们的形成和组成的更大细节。这项工作分析了两种类型的地震波对薄的ULVZ分层敏感，它们与这些ULVZ特征相互作用并反弹。该研究的重点是西太平洋下面的一个地区，因为该地区广泛的地震数据覆盖范围和已知的ULVZ。该项目将创建一个由韩国，台湾和日本的公共记录和网络构建的新的地震数据库。然后，该数据库将使用现代统计功能在CMB处启用ULVZ结构的成像。地幔流的计算机模拟将有助于解释ULVZ的地幔过程中的形成，运动和作用。该项目包括针对当地犹他州太平洋岛社区的K-8学生的年度外展STEM活动。这项活动将包括教授通过热点火山造成太平洋岛屿的地幔羽流的活动。低速度区域（ULVZ）是地球核心膜边界（CMB）的地震速度强烈降低的结构，与热火型火山群和大型火山群体相关或与之息息相关。省份（LLVP），因此是全球地幔动力学的关键组成部分。通常，使用对ULVZ敏感的地震问题的波形分析（例如SPDK，SCP，SCS）研究ULVZ，但是先前的研究因建模而折衷而缺乏通过严格的参数估计而导致的ULVZ参数引起的大量不确定性，并且缺乏ULVZ的地球物理推断。该项目将开发一种变换的波形反演方法，并将其应用于表征ULVZ特性，包括其地震速度，密度，大小和形状。具体而言，该项目将（1）收集一个对ULVZ敏感的SCP和PCP波形的新数据库，利用可公开可用的地震阵列数据以及来自韩国，台湾，日本，国际监测系统（IMS）阵列的新数据以及（2）用于全波式bay bayvz Propertion and ulvz Properties（2）的预先功能（2），以及ul versian的构造。 Bayesian model selection), and to perform joint inversion of ScP and PcP waveforms, (3) quantify the waveform effects from 2-D/3-D ULVZ structures, (4) search for additional, previously unlooked-for arrivals in the ScP wavefield consistent with 3-D ULVZ structure using array processing approaches, and (5) related observed ULVZ localities and properties to lowermost mantle flow and dynamics through 3D geodynamic models.这是犹他大学，亚利桑那州立大学和利兹大学科学家之间的合作提议，因此由国家科学基金会（NSF）和英国自然环境研究委员会（NERC）共同资助。本奖反映了NSF的立法使命，并通过使用基金会的智力效果和广泛的评估来评估诚实地对其进行了评估，以诚实地进行评估。