Investigation of the earth's mantle plumbing system at the global scale using an advanced seismic imaging approach.

使用先进的地震成像方法在全球范围内研究地幔管道系统。

• 批准号: 1417229
• 负责人: Barbara Romanowicz
• 金额: $ 25.95万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1417229&HistoricalAwards=false
• 关键词: Investigation; earth; mantle; plumbing; system

Improving the resolution of earth's mantle structure through seismic imaging is important for our understanding of the deep dynamic processes that are reflected in surface tectonics and ultimately give rise to earthquakes and volcanic eruptions. Seismic tomography utilizes seismic waves originating from natural earthquakes to illuminate the earth's interior using similar principles as used in medical imagery. While the long wavelength, smooth structure is now well documented, we strive to sharpen the picture and resolve smaller scale features that will help understand in detail how the internal circulation drives the motions of tectonic plates, and vice-versa, and obtain a better view of how heat is channeled from the deep interior to the surface, resulting not only in the system of volcanoes mid-ocean ridges but also in mid-plate volcanoes called "hotspots", such as the Hawaiian chain. Because hotter than average regions correspond to low seismic velocities, which are particularly difficult to image, their accurate imaging has not been possible until recently, with the advent of numerical methods to accurately compute the seismic wavefield propagation across the earth's mantle. This project builds upon our recent efforts to develop global seismic images of the entire mantle using such computations, and improve the sharpness of these images.The main goal of this project is to finalize the construction of higher resolution (up to 200-400 km laterally) global 3D radially anisotropic shear velocity model of the whole mantle based on a time domain waveform inversion approach that has so far been applied only to the upper mantle, with promising results. This waveform inversion methodology builds upon 20 years of experience of the PI in waveform tomography using mode-based wavefield computations, as well as two generations of global upper mantle shear velocity models developed using long period fundamental mode and overtone waveforms (periods 60s) and numerical wavefield computations (Spectral Element Method). In order to resolve lower mantle structure, isolating wavepackets that contain body wave energy is necessary, therefore we propose to extend the period range of our dataset to 30s - this will also increase spatial resolution further in the upper mantle, while keeping computations manageable. Further goals of the proposal are to (1) obtain higher resolution in the lateral variations of radial anisotropy throughout the mantle, (2) test the sensitivity of the 30 s dataset to inversion for a global averaged S/P velocity conversion factor and (3) collect additional, shorter window (~30mn after origin time) waveforms down to 20s to include more P wave energy and perform additional iterations to obtain a global P velocity model of the lower mantle.

通过地震成像改善地球结构的分辨率对于我们对反射在表面构造中反映的深层动态过程的理解很重要，并最终导致地震和火山喷发。地震层析成像利用源自自然地震的地震波使用与医学图像中使用的类似原理来照亮地球的内部。 While the long wavelength, smooth structure is now well documented, we strive to sharpen the picture and resolve smaller scale features that will help understand in detail how the internal circulation drives the motions of tectonic plates, and vice-versa, and obtain a better view of how heat is channeled from the deep interior to the surface, resulting not only in the system of volcanoes mid-ocean ridges but also in mid-plate volcanoes called "hotspots", such as the夏威夷连锁店。由于比平均区域高的区域对应于低地震速度，这是特别难以成像的，因此直到最近，由于数值方法的出现，它们的准确成像才能准确地计算地震波场传播。该项目以我们最近为使用此类计算开发整个地幔的全球地震图像的努力为基础 结果。这种波形反演方法基于使用基于模式的波场计算的波形层析成像中PI的20年经验，以及使用长期基本模式和夸隆波形（周期60s）和数值波场计算（Spectral Element方法）开发的两代全球上层地幔剪切速度模型。为了解决较低的地幔结构，必须隔离包含人体波能的波袋，因此我们建议将数据集的周期范围扩展到30s-这也将在上幔中进一步增加空间分辨率，同时使计算可管理。 Further goals of the proposal are to (1) obtain higher resolution in the lateral variations of radial anisotropy throughout the mantle, (2) test the sensitivity of the 30 s dataset to inversion for a global averaged S/P velocity conversion factor and (3) collect additional, shorter window (~30mn after origin time) waveforms down to 20s to include more P wave energy and perform additional iterations to obtain a global P下地幔的速度模型。