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.

确定海洋岩石圈的性质以及它们如何随着岩石圈年龄的变化而变化是科学家用来推断其组成和演化的主要方法之一。海洋地壳的参考模型使用地震波穿过地球的速度（即，地震速度）作为主要参数。然而，目前的模型主要使用压缩地震波（波的振动方向与传播方向相同）。该项目将建立一个海洋地壳和上地幔的剪切速度（与传播方向成直角振动的波）参考模型。该模型将来自2012年在俄勒冈州和华盛顿近海的胡安德富卡构造板块收集的数据。该地区的地壳年龄从0到900万年不等。这个模型将提供一个参考框架，解释海洋地壳的组成，修改岩浆活动，变形，蚀变和断裂的程度方面的属性。该模型还可用于量化海洋地壳中进入深海海沟的水量，这些海沟会影响到俯冲带的巨型逆冲断层地震和弧火山活动等自然灾害。该项目将支持一名博士后研究员和一名研究生。通过利用现有的地震数据集，该项目还将利用以前在海洋地震采集方面的投资。2012年海底地震仪数据集包括转换波的高质量记录，可用于限制穿过沉积物、地壳、和最上地幔在板块尺度上从Juan de Fuca海岭近轴区到Cascadia变形锋，包括0 ~9 Ma的地壳年龄。该数据集将用于：（1）通过模拟来自基底的压缩（P）和P-S反射的振幅与偏移距，并基于马尔可夫链蒙特卡罗方法和P-Sv波传播的时域弹性有限差分模拟，对OBS数据进行高级伪一维非线性贝叶斯波形反演，来约束最浅火成岩地壳中的S波速度结构。(2)利用超虚折射干涉理论对OBS记录进行高级处理，提高地幔折射S波的信噪比和可探测性。(3)使用广角地壳和地幔折射/反射P到S转换相位，对沿沿着洋脊到海沟断面的地壳和上地幔的二维S波速度结构进行走时层析成像建模。(4)研究了地壳和地幔S波速度结构的方位各向异性特征。结果将使用有效介质理论，根据地壳和地幔内矿物沉淀引起的热液蚀变和孔隙填充作为年龄的函数来解释。该项目的最后交付产品将是一个参考模型，描述地壳年龄为0- 10年的洋壳和上地幔剪切波结构。该奖项反映了NSF的法定使命，并通过利用基金会的智力价值和更广泛的影响审查标准。