Seismic Studies of the Lowermost Mantle and Core-Mantle Boundary

小行星9417542 本研究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都很重要。 这项工作将利用基本上尚未开发的数字数据来源，以增加核幔边界直接观测的数量。 将对数字波形目录进行搜索，以提取和分析SKS-SKKS-SHdiff-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走时计算。 衍射相位和核心相位之间的差分传播时间消除了大部分寄生源和接收器效应，这两条路径都类似。 目前的三维层析地幔速度模型将被用来帮助纠正不同程度的非均匀性之间的差异，在地幔中的发散衍射和核心阶段之间的异常差异，因为外核心是太流体保持高度的非均匀性，衍射和核心阶段旅行时间之间的异常差异将被解释为由于在D”的非均匀性。 由于不同的D”速度结构以不同的方式影响SVdiff/SHdiff和SKKS/SKS比值，因此还将分析波形频率振幅的变化，以解释最低地幔的速度结构。 *** ??

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. *** ??