Collaborative Research: CSEDI--Multi-scale Analysis of Mantle Discontinuities Using Inverse Scattering of SS Waves and Experimental Mineral Physics

合作研究：CSEDI——利用SS波逆散射和实验矿物物理对地幔不连续性进行多尺度分析

• 批准号: 0757814
• 负责人: Maarten de Hoop
• 金额: $ 8.2万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-15 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0757814&HistoricalAwards=false
• 关键词: Collaborative; Research; CSEDI; Multi; scale

Through a concerted effort of seismic imaging and mineral physics we aim to improve our knowledge of the transition zone between the upper and lower parts of Earth?s mantle, which plays a central role in our understanding of mantle evolution, composition, and dynamics. The transition is marked by phase transformations in the dominant mantle silicates (e.g., olivine), and the associated jumps in elastic parameters can be detected and imaged with seismological techniques. The existence and interpretation (as isochemical phase transitions) of global interfaces near 410 and 660 km depth are no longer disputed. But even for the 410 and 660 many issues are unresolved. Laboratory experiments show that the depth to and the magnitude and transition profile of radial changes across discontinuities depends on various physico-chemical factors, such as temperature, pressure, major element composition and partitioning, and presence of water. In situ estimation of these parameters from seismic data is often complicated by contamination of signal due to shallower mantle heterogeneity and the need to make prior assumptions about the location and character of interfaces. For the 220 and 520 even the lateral extent and cause are debated, and it is unclear if other interfaces exist in the depth range of interest. We aim to investigate the transition zone using a generalized Radon transform of very large numbers (100,000) of broad-band SS waveforms that contain reflections at the underside of these interfaces. Specifically, we wish to (i) detect and locate elasticity contrasts, (ii) characterize the (radial) changes across them, and (iii) determine the lateral extent, variations along, and correlations between different interfaces. The seismological estimates of (local) discontinuity properties and (regional) topographies will be compared with predictions from different (e.g., olivine, pyroxene, garnet) multi-component systems in order to identify and understand compounded transitions and to produce in situ estimates of temperature, composition, and water content. Data coverage is insufficient for a global study: our initial geographical focus is a 2-D transect across import mantle dynamic regimes: from Hawaii (mantle upwelling), across NW Pacific (normal ocean), Kuriles (subduction zone), to Siberia (stable continent). This research is likely to improve our general understanding of the composition and phase chemistry of the upper mantle transition zone and as such provide constraints on the interplay between thermo-chemical mantle convection and upper mantle stratification. Furthermore, the proposed collaboration and integration of inverse scattering, observational seismology, and mineral physics offers a unique educational experience for students, post-doctoral scholars, and senior staff involved.

通过地震成像和矿物物理学的共同努力，我们的目标是提高我们的地球上部和下部之间的过渡带的知识？的地幔，这起着核心作用，在我们的地幔演化，组成和动力学的理解。这种转变的标志是主要地幔硅酸盐的相变（例如，橄榄石），以及弹性参数的相关跳跃可以用地震学技术检测和成像。410公里和660公里深度附近的全球界面的存在和解释（作为等化学相变）不再有争议。 但即使是410和660，也有许多问题没有解决。 实验室实验表明，跨越不连续面的径向变化的深度、幅度和过渡剖面取决于各种物理化学因素，如温度、压力、主要元素的组成和分配以及水的存在。这些参数的地震数据的现场估计往往是复杂的信号污染，由于浅地幔的不均匀性和需要事先假设的位置和接口的字符。 对于220和520，即使是横向范围和原因也存在争议，目前还不清楚在感兴趣的深度范围内是否存在其他界面。 我们的目标是调查过渡区使用广义拉东变换的非常大的数字（100,000）的宽带SS波形，包含在这些接口的底面反射。 具体而言，我们希望（i）检测和定位弹性对比，（ii）表征（径向）变化，并（iii）确定横向范围，变化沿着，和不同接口之间的相关性。 （局部）不连续性和（区域）地形的地震学估计将与不同（例如，橄榄石、辉石、石榴石）多组分系统，以便识别和理解复合转变，并对温度、成分和含水量进行现场估计。 数据覆盖范围不足以进行全球研究：我们最初的地理重点是一个2-D横断面进口地幔动力学制度：从夏威夷（地幔上涌），横跨西北太平洋（正常海洋），千岛群岛（俯冲带），西伯利亚（稳定大陆）。这项研究可能会提高我们的上地幔过渡带的组成和相化学的一般理解，并因此提供热化学地幔对流和上地幔分层之间的相互作用的限制。此外，提议的逆散射、观测地震学和矿物物理学的合作和整合为学生、博士后学者和高级工作人员提供了独特的教育经验。