CSEDI: Fine Structure of the Lower Mantle

地震学家多年前就知道，最下层的地幔是复杂的。在对该区域进行地震波形建模采样的尝试中，产生了超低速度带、明显的水平不连续带、强各向异性带（SHSV），在某些情况下，在垂直墙附近。现在看来，从矿物物理学的角度来看，这种无数的精细结构开始被理解，热钙钛矿的密集熔体和新的后钙钛矿结构。这些新发现可以解释上述许多特征。特别是，研究人员早期在CMB的板块折叠动态二维模型产生了一个强大的正速度梯度，如果允许1%的速度跳跃，这反过来产生了包含小三倍的合成地震图。假设这种跳跃是由于Clapeyron斜率为正的相变引起的，并通过这种混合全球模型转换层析图像，产生了观察到的s波三重的一些地理行为：在快速区域下，后钙钛矿层最厚，在缓慢区域下消失。该团队最新的3D动态模型解释了基于板块俯冲历史的最快区域的位置。三维动力学的结果与二维的结果有很大的不同，当地震和动力模型合并时，可以帮助我们解释更多的下地幔地震波形数据的变异性。为了加快对下地幔的了解，我们提出了解决这些结构的三维性质的研究。他们将解决以下问题：o板块历史与下地幔结构的三维动态预测的兼容性如何？o我们能否将俯冲引起的速度梯度效应与相边界效应分开，并更新全球地图？与非洲结构相比，中太平洋下地幔结构有何不同？就上升流的稳定性而言，这意味着什么？o哪些热化学边界层动力学模型与提出的后钙钛矿结构和地震数据相一致？更广泛的影响上述问题的答案将对整个地球科学界非常有用，特别是矿物物理学家，他们需要关于新发现的相边界的全球特性的基本地震信息。在俯冲史上建立下地幔快速构造之间的直接联系将回答板块构造动力学中的一个关键问题。这些跨学科的努力将帮助参与的学生成为未来CSEDI发展的领导者。

Intellectual MeritSeismologists have known for many years that the lowermost mantle is complex.Attempts at modeling seismic waveforms sampling this region produced ultra-low velocity zones, sharp horizontal discontinuities, strong zones of anisotropy (SHSV), and in some cases near vertical walls. It now appears that this myriad of fine structure is beginning to be understood in terms of mineral physics with dense melts from hot perovskite and a new post-perovskite structure. These new discoveries can explain many of the above features. In particular, the investigators earlier dynamic 2D model of slabs folding at the CMB generates a strong positive velocity gradient, which in turn produces synthetic seismograms containing a small triplication, if a 1% velocity jump is allowed. Assuming that this jump results from a phase-change with a positive Clapeyron slope, and transforming tomographic images through such a hybrid global model, generates some of the geographic behavior of the observed S-wave triplication: where the post-perovskite layer is thickest beneath fast regions and disappears beneath slow regions. The team's latest 3D dynamic models explain the locations of the fastest regions based on the history of plate subduction. Results from 3D dynamics are significantly different from those in 2D, and may help us explain more of the variability in seismic waveform data sampling the lower mantle when seismic and dynamic models are merged. In order to make accelerated progress toward understanding the lower mantle and D" propose research to resolve the 3D nature of these structures. They will address the following questions:o How compatible are 3D dynamic predictions of slab histories with lower mantlestructure? o Can we separate velocity gradient effects caused by subduction from the phase-boundary effects and update a global map?o How different is the mid-Pacific lower mantle structure compared to the Africanstructure and what does this imply in terms of the stability of upwelling?o What dynamic models of thermo-chemical boundary layers are consistent with the proposed post-perovskite structure and seismic data?Broader ImpactAnswers to the above questions will be of great use to the entire Earth Science community, especially mineral physicists who need fundamental seismic information about the global properties of the newly discovered phase boundary. Making the direct connection between the detailed fast structures in the lower mantle with respect to the history of subduction will answer a key question in plate tectonic dynamics. These multi-disciplinary efforts should help the involved students become leaders in future CSEDI developments.