Effects of Upper Mantle Phase Transitions on Seismic Motions

[9526905] Wahr这项研究是为了研究上地幔相变，例如在410和660公里深处，对地震运动，特别是地球的自由振荡可能产生的影响。初步估计表明，在地震运动期间，相位边界附近的物质在振荡时可能会改变相位。例如，660公里边界对自由振荡的本征频率的扰动可能在十分之一到百分之几之间的任何地方，完全在本征频率的观测不确定性之内。目的是研究球面结构的自由振荡数据反演能否提供410 km和660 km不连续面的有用信息；并判断在反演过程中加入相变效应是否会改善其他参数的反演。对于后者，工作将特别集中，虽然不是完全集中，对过渡区密度分布的影响，以及从径向模式衰减观测推断出的体耗散模型。* * * ? ?

9526905 Wahr This research is to study the possible effects of upper mantle phase transformations, for example at depths of 410 and 660 km, on seismic motions, especially the free oscillations of the earth. Preliminary estimates suggest that during seismic motions, material in the vicinity of a phase boundary could change phase as it oscillates. For example, perturbations to the eigenfrequencies of free oscillations due to the 660 km boundary could be anywhere from a few tenths to several percent, well within the observational uncertainties of the eigenfrequencies. The objectives are to study whether the inversion of free oscillation data for spherical structure could provide useful information on the 410 and 660 km discontinuities; and to judge whether the inclusion of phase transformation effects into the inversion process might improve the inversions for other parameters. For the latter, the work will focus especially, though not exclusively, on implications for the density profile in the transition zone, and on the bulk dissipation models that have been inferred from observations of radial mode attenuation. *** ??