A Reference Vs and Vp/Vs Model for Young Oceanic Crust From Controlled-Source OBS Data

基于受控源 OBS 数据的年轻洋地壳参考 Vs 和 Vp/Vs 模型

• 批准号: 2149630
• 负责人: Juan Pablo Canales
• 金额: $ 38.97万
• 依托单位: Woods Hole Oceanographic Institution
• 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: 2022-03-01 至 2024-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2149630&HistoricalAwards=false
• 关键词: Reference; Vs; Vp; Model; Young

Determining the properties of oceanic lithosphere and how they vary as the lithosphere ages is one of the primary methods that scientists use to infer its composition and evolution. Reference models of oceanic crust use the speed at which seismic waves travel through the Earth (i.e., seismic velocity) as their main parameter. However, current models use primarily compressional seismic waves (waves that vibrate in the same direction as they travel). This project will build a shear velocity (waves that vibrate at right angles to the direction of travel) reference model for oceanic crust and upper mantle. The model will be derived from data collected in 2012 across the Juan de Fuca tectonic plate offshore Oregon and Washington. Crustal ages in this region vary from 0 to 9 million years. This model will provide a reference framework to interpret ocean crust properties in terms of composition, modification by magmatic activity, and extent of deformation, alteration, and fracturing. The model can also be used to quantify the amount of water in oceanic crust entering deep-sea trenches that influence natural hazards such as megathrust earthquakes and arc volcanism at subduction zones. This project will support a postdoctoral investigator and a graduate student. By making use of existing seismic datasets, this project will also leverage previous investments in marine seismic acquisition.The 2012 ocean bottom seismometer (OBS) dataset includes high-quality recordings of converted waves that can be exploited to constrain shear-wave (S) velocity structure through the sediments, crust, and uppermost mantle at a plate scale from the Juan de Fuca Ridge near-axis region to the Cascadia deformation front, encompassing crustal ages from 0 to ~9 Ma. This dataset will be used to: (1) Constrain S-wave velocity structure in the shallowmost igneous crust by modeling the amplitude vs. offset of compressional (P) and P-to-S reflections from the basement and performing advanced pseudo-1D nonlinear Bayesian waveform inversion of OBS data based on a Markov Chain Monte Carlo method and time-domain elastic finite-difference simulation of P-Sv wave propagation. (2) Advanced processing of the OBS records using the theory of supervirtual refraction interferometry for improving the signal-to-noise ratio and detectability of mantle refracted S waves. (3) Conduct traveltime tomography modeling of the 2-D S-wave velocity structure of the crust and uppermost mantle along the Ridge-to-Trench transects using wide-angle crustal and mantle refracted/reflected P-to-S converted phases. (4) Investigate the azimuthal anisotropic character of the crustal and mantle S-wave velocity structure. The results will be interpreted in terms of hydrothermal alteration and porosity in-filling due to mineral precipitation within the crust and mantle as a function of age using effective medium theory. The final deliverable product of this project will be a reference model describing the shear-wave structure of oceanic crust and uppermost mantle for crustal ages of 0-9 Ma built from synthesizing the project’s results and integrating them with existing results from other seismic experiments in the region.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.

确定海洋岩石圈的特性以及它们如何随着岩石圈年龄的变化是科学家用来推断其组成和进化的主要方法之一。海洋壳的参考模型使用地震波穿过地球（即地震速度）作为其主要参数的速度。但是，当前模型使用主要的压缩地震波（波动的波动在与行进相同的方向上振动）。该项目将建立一个剪切速度（波动的振动与旅行方向的振动为振动），用于海洋壳和上地幔的参考模型。该模型将源自2012年在俄勒冈州近海和华盛顿的Juan de Fuca Tectonic板块中收集的数据。该地区的地壳年龄从0到900万年不等。该模型将提供一个参考框架，以解释海壳特性，从组成，通过岩浆活动进行修改以及变形，改变和破裂的程度。该模型还可以用来量化海洋壳中的水量，进入深海沟渠，这些水沟影响自然危害，例如俯冲带的自然危害，例如巨型地震和弧火山。该项目将支持博士后调查员和研究生。 By making use of existing seismic datasets, this project will also leverage previous investments in marine seismic acquisition.The 2012 ocean bottom seismometer (OBS) dataset includes high-quality recordings of converted waves that can be explored to constrain shear-wave (S) velocity structure through the sediments, crust, and uppermost mantle at a plate scale from the Juan de Fuca Ridge near-axis region to the Cascadia变形前，包括0到〜9 mA的地壳年龄。 This dataset will be used to: (1) Constrain S-wave velocity structure in the shallowmost igneous crust by modeling the amplifier vs. offset of compression (P) and P-to-S reflections from the basement and performing advanced pseudo-1D nonlinear Bayesian waveform inversion of OBS data based on a Markov Chain Monte Carlo method and time-domain elastic finite-difference simulation of P-Sv wave propagation. （2）使用Supperirual Firtual折射干扰理论来提高信噪比和地幔折射波的可检测性，对OBS记录进行了高级处理。 （3）使用宽角壳和地幔折射/反射的P-TO-T-TO-S转换相位的相位的宽角地壳和地幔沿山脊到沟渠进行2-D S波速度结构的旅行时间断层扫描建模。 （4）研究地壳和地幔S波速度结构的方位角各向异性特征。由于地壳和地幔内的矿物降水为该项目的最终可交付产品，将根据水热的改变和孔隙率来解释结果，将是一个参考模型，描述了海洋外皮的剪切波结构，并在与其他项目中综合了其他实验的结果，并将其整合到了其他实验的结果，并将其与其他成果整合在一起，并将其整合到现有的结果中NSF的法定使命，并使用基金会的知识分子优点和更广泛的审查标准来评估，被认为是宝贵的支持。