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及其随岩石圈年龄的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（即地震波）。然而，当前模型主要使用压缩地震波（与传播方向相同的波）。该项目将建立剪切速度（振动的波）。与行进方向成直角）海洋地壳和上地幔的参考模型 该模型将根据 2012 年在俄勒冈州和华盛顿州近海的胡安德富卡构造板块收集的数据得出。该地区的地壳年龄从 0 到 9 不等。该模型将提供一个参考框架来解释海洋地壳的成分、岩浆活动的改变以及变形、蚀变和破裂的程度。该模型还可用于量化水量。该项目将支持一名博士后研究员和一名研究生，利用现有的地震数据集，并利用之前的投资。 2012 年海底地震仪 (OBS) 数据集包括高质量的转换波记录，可用于约束穿过沉积物的剪切波 (S) 速度结构，从胡安德富卡海岭近轴区域到卡斯卡迪亚变形前缘的板块尺度上的地壳和最上地幔，涵盖 0 到 ~9Ma 的地壳年龄。该数据集将用于：（1）约束 S 波速度。通过对来自基底的压缩 (P) 和 P-to-S 反射的幅度与偏移进行建模，并基于 OBS 数据执行先进的伪一维非线性贝叶斯波形反演，可以确定最浅火成岩地壳中的结构。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（2）利用超虚拟折射干涉测量理论对OBS记录进行高级处理，提高地幔的信噪比和可探测性。 (3) 沿脊至海沟横断面对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)研究地壳和地幔横波速度结构的方位各向异性特征，结果将根据热液蚀变和孔隙度进行解释。 - 使用有效介质理论，由于地壳和地幔内的矿物沉淀导致的充填作为年龄的函数，该项目的最终可交付产品将是描述海洋地壳和地幔剪切波结构的参考模型。地壳年龄为 0-9 Ma 的最上地幔是通过综合该项目的结果并将其与该地区其他地震实验的现有结果相结合而建立的。该奖项授予 NSF 的法定使命，并通过使用基金会的智力成果和评估进行评估，被认为值得支持。更广泛的影响审查标准。