Regional Studies of Anisotropy Beneath the Pacific Ocean

近年来的一些研究已经证实，海洋下地壳和上地幔的弹性性质都是各向异性的。我们建议通过比较在区域和近距离记录的观测波形与广义各向异性模型计算的波形来研究该各向异性的性质，广义各向异性模型可以包括多达13个弹性常数，并且可以在大小和方向上随层而变化。通过将我们的观测限制在传播距离较短的波上，我们将尽量减少速度结构的横向非均质性对波形的影响，增加各向异性沿该路径方向和大小均匀的可能性，并且，如果有不同距离的路径可用，可以分离上地壳、下地壳和上地幔各向异性结构变化的影响。此外，由于使用的路径较短，因此可以利用太平洋许多地区的小型活动。

Several studies in recent years have confirmed that both the crust and upper mantle beneath oceanic regions are anisotropic in their elastic properties. We propose to study the nature of that anisotropy by comparisons of observed waveforms recorded at regional and near distances with those calculated for models of generalized anisotropy which can include up to 13 eleastic constants and which can vary from layer to layer in magnitude and direction. By restricting our observations to waves which have traveled short distances we will minimize any effects of lateral heterogeneity of velocity structure on wave forms, increase the likelihood that the orientation and magnitude of anisotropy is uniform along that path, and, if paths of different distances are available, may be able to separate the effects of varying anisotropic structure in the upper crust, lower crust, and upper mantle. In addition, since short paths are used, it will be possible to use small events which are numerous in many parts of the Pacific.