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

通过地震成像和矿物物理的共同努力，我们的目标是提高我们对地球上下过渡带-S地幔的认识，该带在我们理解地幔的演化、成分和动力学方面发挥着核心作用。这种转变以主要地幔硅酸盐(如橄榄石)中的相变为标志，与之相关的弹性参数跳跃可以用地震学技术探测和成像。410和660公里深度附近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，许多问题也没有得到解决。实验室实验表明，不连续面径向变化的深度、大小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。从地震数据现场估计这些参数往往因地幔浅层的非均质性以及需要对界面的位置和特征做出预先假设而受到信号污染的影响。对于220和520，就连横向范围和成因都存在争议，而且不清楚在感兴趣的深度范围内是否存在其他界面。我们的目标是使用大量(100,000)宽带SS波形的广义Radon变换来研究过渡区，这些波形在这些界面的底部包含反射。具体地说，我们希望(I)检测和定位弹性对比，(Ii)表征它们之间的(径向)变化，以及(Iii)确定不同界面之间的横向范围、变化和相关性。地震学对(局部)不连续性质和(区域)地形的估计将与不同(如橄榄石、辉石、石榴石)多组分系统的预测进行比较，以便识别和理解复合转变，并产生对温度、成分和水含量的现场估计。数据覆盖范围不足以进行全球研究：我们最初的地理焦点是横跨输入地幔动力学体系的二维断面：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)，到西伯利亚(稳定大陆)。这项研究可能会加深我们对上地幔过渡带的组成和相化学的总体认识，从而为热化学地幔对流和上地幔层结之间的相互作用提供制约。此外，建议的逆散射、观测地震学和矿物物理学的合作和整合为学生、博士后学者和相关高级工作人员提供了独特的教育体验。

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.