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Continental and oceanic upper mantle structure from seismic array data

来自地震阵列数据的大陆和海洋上地幔结构

基本信息

批准号：
NE/F000898/1
负责人：
Sebastian Rost
金额：
$ 9.12万
依托单位：
University of Leeds
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FF000898%2F1
关键词：
Continental oceanic upper mantle structure

项目摘要

Velocity profiles of the Earth's upper mantle are characterized by discontinuous jumps of the seismic velocities. The main velocity discontinuities (or simply discontinuities) are located at depths of approximately 410 and 660 km. Both of these discontinuities can be explained by solid-solid phase transitions in the major olivine component of the mantle material. Nonetheless, the minor constituents of the mantle material will introduce additional, mostly smaller, discontinuous jumps of the velocities at different depths. These transitions complicate the seismic image of the upper mantle structure. High resolution studies are necessary to detect these discontinuities and to image the fine scale structure of the upper mantle with strong implications for the mineral-physical constitution of the Earth's mantle and geodynamical modelling of dynamics and evolution of Earth's mantle. We propose to use traveltime and waveform information from data recorded at seismic arrays located in India and Australia to resolve the structure of the upper mantle beneath northern Australia and northern and eastern India. Major earthquake belts are located in a distant range from these arrays that allows the study of the seismic wave triplications due to the velocity increases at the discontinuities. Several thousand earthquakes recorded at the arrays will be collected to achieve a dense coverage of the study area. Using time series stacking techniques we are able to resolve the different branches of the triplication and measure traveltimes with high precision. Using this information in forward modelling schemes will allow us to develop models of the upper mantle velocity structure and the depth location of the discontinuities. Furthermore, stacking techniques lead to increased signal-to-noise ration of coherent arrivals allowing us to use waveform information from subtle arrivals originating from the upper mantle discontinuities. We will use waveform modelling of the triplicated arrivals and of S-to-P conversions at the discontinuities to resolve the fine scale structure of the velocity increases. One-dimensional and high-performance wave propagation techniques will be used to model the effect of the fine-scale structure of the discontinuities onto the wavefield. This study will put important constraints on the composition and dynamics of the upper mantle in different tectonic regions of the Earth including a continent-continent collision zone and recent oceanic subduction.

地球上地幔的速度剖面具有地震波速度不连续跳跃的特征。主要的速度间断（或简称间断）位于大约410和660公里的深度。这两个不连续性可以解释为地幔物质的主要橄榄石成分的固-固相变。尽管如此，地幔物质的次要成分将在不同深度处引入额外的、大多数较小的、不连续的速度跳跃。这些转变使上地幔结构的地震图像复杂化。高分辨率的研究是必要的，以检测这些不连续性和图像的上地幔的精细尺度结构与地球地幔的矿物物理构成和地球动力学模型的动力学和地球地幔的演化的强烈影响。我们建议使用位于印度和澳大利亚的地震台阵记录的数据的走时和波形信息，以解决澳大利亚北方和印度北方和东部下的上地幔的结构。主要地震带位于远离这些阵列的范围内，这使得可以研究由于不连续处的速度增加而引起的地震波三重化。将收集在阵列上记录的数千次地震，以实现研究区域的密集覆盖。利用时间序列叠加技术，我们能够解决三重波的不同分支，并以高精度测量走时。在正演模拟方案中使用这些信息将使我们能够建立上地幔速度结构和不连续面深度位置的模型。此外，叠加技术导致增加的信号-噪声比的相干到来，使我们能够使用来自上地幔不连续性的微妙的到来波形信息。我们将使用波形模拟的三重到达和S到P转换的不连续性，以解决速度增加的精细尺度结构。一维和高性能的波传播技术将被用来模拟波场上的不连续的精细尺度结构的影响。这项研究将对地球不同构造区域的上地幔的组成和动力学提出重要的限制，包括大陆-大陆碰撞带和最近的大洋俯冲。