Seismic Studies of the Lowermost Mantle and Core-Mantle Boundary

9417542届会议本研究的目的是进行核幔边界的地震学填图。这一边界对于地幔对流和来自地核的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，将核-地幔边界的直接观测次数增加一个数量级。将搜索数字波形目录，以通过计算涉及反射率合成地震记录的差分走时来提取和分析SKS-SKKS-SHdiff-SVdiff和PKP(Df)-Pdiff相位的波形集。衍射相和核心相之间的不同旅行时间消除了对两个路径都相似的大部分伪源和接收器效应。目前的三维层析成像地幔速度模型将被用来帮助校正非均质性程度之间的差异，地幔中发散绕射和核相之间的异常差异，并且由于外核太过流体而不能保持高度的非均质性，衍射相和核相旅行时之间的异常差异将被解释为由于D“的非均质性。还将分析波形频率幅度的变化来解释最低地幔的速度结构，因为不同的D”速度结构以不同的方式影响SVdiff/SHDiff和SKKS/SKS比率。*？？

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. *** ??