Modeling Body and Surface Wave Anisotropy in 3-D Media with a Case Study in Iceland

通过冰岛的案例研究对 3D 介质中的体和表面波各向异性进行建模

• 批准号: 0510955
• 负责人: Aibing Li
• 金额: $ 3万
• 依托单位: University of Houston
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-15 至 2007-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0510955&HistoricalAwards=false
• 关键词: Modeling; Body; Surface; Wave; Anisotropy

Seismic anisotropy provides important constraints on deformation in the lithosphere and mantle flow patterns in the asthenosphere. Radial anisotropy can be measured from Rayleigh and Love wave dispersions; and azimuthal anisotropy is often obtained from shear-wave splitting of SKS phases and from Rayleigh wave tomography. However, the results of azimuthal anisotropy from the two methods do not agree in many areas, such as in the Colorado Rockies, Iceland, and Australia. Part of the discrepancy is due to the different properties of body and surface waves. For example, SKS splitting reflects an integral result of anisotropy from the core mantle boundary to the surface while Rayleigh waves at periods less than 100 s primarily sample the earth above 200 km. The discrepancy can also be attributed to many other factors, including the tradeoff between lateral heterogeneity and anisotropy, 3-D variations of anisotropy, and the finite frequency. The goal of our proposed study is to investigate the discrepancy between shear-wave splitting anisotropy and Rayleigh wave anisotropy in general cases. The suspected reasons listed above will be studied individually. We propose to adopt the parallel pseudo-spectral method in computing synthetic waveforms of SKS phases and surface waves in various 3-D heterogeneous and anisotropic models. This method has been successfully applied in modeling shear-wave splitting. More experiments will be performed in modeling surface waves through the pseudo-spectral method. The shear-wave splitting technique and the two-plane-wave inversion method will be applied to the synthetic data to retrieve anisotropy and heterogeneity. The proposed study will improve our understanding about the discrepancy in azimuthal anisotropy from body and surface waves.

地震各向异性对软圈的岩石圈和地幔流动模式的变形提供了重要的限制。 径向各向异性可以从瑞利和爱波分散体中测量；并且方位角各向异性通常是从SKS相的剪切波分裂和瑞利波断层扫描中获得的。 但是，这两种方法的方位角各向异性的结果在许多领域，例如在科罗拉多洛矶山脉，冰岛和澳大利亚都不一致。 差异的一部分是由于身体和表面波的不同特性所致。 例如，SKS分裂反映了从核心地幔边界到表面的各向异性的积分结果，而雷利在周期小于100 s的波浪中主要采样了200 km以上的地球。 差异也可以归因于许多其他因素，包括侧向异质性和各向异性之间的权衡，各向异性的3-D变化以及有限的频率。 我们提出的研究的目的是研究在一般情况下，剪切波分裂各向异性和瑞利波各向异性之间的差异。 上面列出的可疑原因将进行单独研究。我们建议在各种3-D异质和各向异性模型中，在计算SKS相和表面波的合成波形中采用平行伪谱法。 该方法已成功应用于建模剪切波分裂。 通过伪谱法对表面波进行建模时，将进行更多实验。 剪切波分裂技术和两平面波反转方法将应用于合成数据以检索各向异性和异质性。 拟议的研究将提高我们对方位角各向异性差异的理解。