Collaborative Research: Imaging small-scale convection and structure of the mantle in the south Pacific: a US contribution to international collaboration PacificArray

合作研究：对南太平洋小规模对流和地幔结构进行成像：美国对国际合作的贡献 PacificArray

基本信息

批准号：
1658491
负责人：
James Gaherty
金额：
$ 51.64万
依托单位：
Columbia University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-08-15 至 2020-10-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1658491&HistoricalAwards=false
关键词：
Collaborative Research Imaging small scale

项目摘要

All deformation on the surface of Earth, including faulting responsible for earthquakes, is produced by the motion of tectonic plates. It is widely accepted that thermal convection in the mantle drives plate motion, but details of that convection and how exactly it moves the plates are poorly understood. Oceanic plates make up 70% of the Earth's surface and offer important windows into mantle convection, yet they are largely unexplored due to the lack of seismic data from the ocean basins. Questions abound regarding the thermal structure of oceanic plates, the significance of volcanism in the middle of oceanic plates, and how the convecting mantle beneath the plates controls their movements. Waves in the gravity field and un-explained shallowing of the ocean floors hint at small-scale convection beneath the oceanic plates. This project contributes to an international effort to strategically place temporary arrays of instruments across the Pacific Ocean basin that record the energy from earthquakes. Recent community advances in ocean bottom seismographs will be used to record unique datasets in locations where large gaps in coverage exist today. These data will allow us to infer deformation and variations in mantle temperature related to small-scale convection. As part of the international collaboration, all data will be openly available to scientists worldwide. The project supports the training of graduate and undergraduate students.This project will collect 12-15 months of broadband ocean bottom seismograph (OBS) data in two 30-station arrays in the central and southern Pacific. These arrays, deployed at two distinct plate ages (~30 Ma and ~120 Ma), will address specific critical questions on the dynamics of the oceanic asthenosphere, including its underlying state (temperature, presence of melt, water or other volatiles, and deformation mechanism). The arrays are designed to image the anisotropic velocity signature of small-scale convection, which has been invoked to explain the flattening of the age versus depth curve in old ocean plates, 140-200 km wavelength gravity lineations, and ubiquitous off-axis, non-plume volcanism observed at a variety of scales. Anisotropic surface wave and body wave tomographic models will be supplemented by shear wave splitting and attenuation measurements to obtain a multi-faceted understanding of the asthenosphere and base of the plates. Finally, the order-of-magnitude increases in path coverage for surface and body waves in the south-central Pacific will enable new advances in global tomography.

地球表面的所有变形，包括引发地震的断层作用，都是由构造板块的运动产生的。人们普遍认为地幔中的热对流驱动板块运动，但人们对这种对流的细节以及它如何精确地移动板块却知之甚少。海洋板块占地球表面的 70%，为了解地幔对流提供了重要窗口，但由于缺乏海洋盆地的地震数据，海洋板块基本上未被勘探过。关于海洋板块的热结构、海洋板块中部火山活动的重要性以及板块下方的对流地幔如何控制其运动等问题比比皆是。重力场中的波浪和无法解释的海底变浅暗示着海洋板块下方存在小规模对流。该项目有助于国际社会战略性地在太平洋盆地放置临时仪器阵列来记录地震能量。海底地震仪方面的最新进展将用于记录当今覆盖范围存在较大差距的地区的独特数据集。这些数据将使我们能够推断与小规模对流相关的变形和地幔温度变化。作为国际合作的一部分，所有数据都将向全世界的科学家开放。该项目支持研究生和本科生的培训。该项目将在中太平洋和南太平洋的两个30站阵列中收集12-15个月的宽带海底地震仪（OBS）数据。这些阵列部署在两个不同的板块年龄（~30 Ma 和~120 Ma），将解决有关海洋软流圈动力学的具体关键问题，包括其基础状态（温度、融化、水或其他挥发物的存在以及变形）机制）。这些阵列旨在对小规模对流的各向异性速度特征进行成像，这已被用来解释旧海洋板块中年龄与深度曲线的平坦化、140-200公里波长重力线状以及无处不在的离轴、非-在各种尺度上观察到的羽流火山活动。各向异性表面波和体波层析成像模型将辅以剪切波分裂和衰减测量，以获得对软流圈和板块底部的多方面了解。最后，中南太平洋表面波和体波路径覆盖范围的数量级增加将使全球层析成像取得新进展。