Bounds on Anisotropic Velocity Heterogeneity from Surface Waves and Body Phases

我们要求利用一种直接反演地球结构的三分量基波、高模面波和体相波形的技术，研究太平洋下上地幔的横向非均质性和各向异性。我们将把最初的工作集中在太平洋盆地的西部、北部和西北部，收集来自GDSN和WWSSN网络的数据。我们对穿越该区域的波形的初步观察显示了上地幔各向异性和非均质性的大量证据，这些证据不容易用简单的年龄依赖模型来解释，包括夏威夷西北部涌浪和沙茨基隆起下方的大面积异常快速度。对“正常”路径的极化各向异性的初步估计表明，至少在低速带的底部，SH速度到处都比SV速度快。合成数据的实验证明了我们的技术能够解决各向异性随深度的分布和盖子/各向异性的权衡。

We request for studies of the lateral heterogeneity and anisotropy of the upper-mantle beneath the Pacific Ocean, using a technique which inverts three-component fundamental and higher-mode surface-wave and body-phase waveforms directly for earth structure. We will concentrate our initial work on the western, northern, and northwestern Pacific Ocean basin, accumulating data from the GDSN and WWSSN networks. Our initial observations of waveforms traversing this region show substantial evidence for upper-mantle anisotropy and heterogeneity not easily explained by simple age-dependent models, including a large area of anomalous fast velocities beneath the northwestern Hawaiian Swell and the Shatsky Rise. Preliminary estimates of polarization anisotropy for "normal" paths indicate that SH velocities are everywhere faster than SV velocities at least to the bottom of the low-velocity zone. Experiments with synthetic data demonstrate the ability of our technique to resolve the distribution of anisotropy with depth and the lid/anisotropy tradeoff.