Seismic Studies of the Lowermost Mantle and Core-Mantle Boundary

[9417542]本次研究的目的是对核幔边界进行地震填图。这个边界对于地幔对流和地核热传递的模型是重要的。这项工作将利用基本上未开发的数字数据来源，将对核心-地幔边界的直接观测数量增加一个数量级。搜索数字波形目录，提取和分析sks - skks - shff - svdiff和PKP(DF)-Pdiff相位的波形集，使用涉及反射率合成地震图的差分传播时间计算。衍射相位和核心相位之间的差分旅行时间消除了大部分的杂散源和接收器效应，这两个路径是相似的。目前的3-D层析地幔速度模型将用于帮助纠正非均质程度之间的差异，以及地幔中发散的衍射相和核相之间的异常差异。由于外核流体太大，无法保持高度的非均质性，衍射相和核相旅行时间之间的异常差异将被解释为D ‘ ’的非均质性。由于不同的D”速度结构以不同的方式影响SVdiff/SHdiffand SKKS/SKS比值，因此还将分析波形频率幅值的变化以解释最下层地幔的速度结构。* * * ? ?

9417542 Wysession This research is to do seismological mapping of the core-mantle boundary. This boundary is important for models of convection in the mantle and of heat transfer from the core. This work will take advantage of essentially untapped sources of digital data to increase by an order of magnitude the number of direct observations of the core-mantle boundary. A search will be done for digital waveform catalogs to extract and analyze the waveform sets of SKS-SKKS-SHdiff-SVdiff and PKP(DF)-Pdiff phases using a calculation of differential travel times involving reflectivity synthetic seismograms. Differential travel times between diffracted and core phases eliminate most of the spurious source and receiver effects which are similar for both paths. Current 3-D tomographic mantle velocity models will be used to help correct for differences between the degrees of heterogeneity, anomalous differences between the diverging diffracted and core phases in the mantle, and because the outer core is too fluid to maintain high degrees of heterogeneity, anomalous differences between the diffracted and core phase travel times will be interpreted as being due to heterogeneities in D". Variations in the frequency amplitudes of the waveforms will also be analyzed to interpret the velocity structure of the lowermost mantle, as different D" velocity structures affect the SVdiff/SHdiffand SKKS/SKS ratios in different ways. *** ??