Finite-Frequency SKS Splitting: Measurement and Sensitivity Kernels
Finite-Frequency SKS Splitting: Measurement and Sensitivity Kernels
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有限频率 SKS 分裂：测量和灵敏度内核
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
J. Tromp
中科院分区：
文献类型：
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作者：
A. Sieminski;H. Paulssen;J. Trampert;J. Tromp
由各向异性引起的 SKS 波的分裂可以通过测量分裂强度来分析，即 SKS 时间窗口中横向信号相对于径向信号的幅度。这个量仅仅与结构参数有关。将广泛使用的用于测量走时异常的互相关方法扩展到各向异性问题，我们建议通过稳健的互相关方法来测量 SKS 分裂强度，该方法可以自动构建大型高质量数据集。对于弱各向异性，SKS 分裂强度通过将径向信号与径向和横向信号之和进行互相关来检索。互相关方法根据一组加州地震图进行了验证。我们基于数值技术（伴随谱元法）考虑了波传播的完整物理原理，研究了 SKS 分裂强度对地幔中一般各向异性的敏感性。计算结果表明，敏感性主要集中在少数弹性参数和上地幔的一小部分区域。这些基本特性和测量的实际优势使得互相关 SKS 分裂强度特别适合上地幔各向异性的有限频率成像。
Splitting of SKS waves caused by anisotropy may be analyzed by measuring the splitting intensity, i.e., the amplitude of the transverse signal relative to the radial signal in the SKS time window. This quantity is simply related to structural parameters. Extending the widely used cross-correlation method for measuring travel-time anomalies to anisotropic problems, we propose to measure the SKS-splitting intensity by a robust cross-correlation method that can be automated to build large high-quality datasets. For weak anisotropy, the SKS-splitting intensity is retrieved by cross-correlating the radial signal with the sum of the radial and transverse signals. The cross-correlation method is validated based upon a set of Californian seismograms. We investigate the sensitivity of the SKS-splitting intensity to general anisotropy in the mantle based upon a numerical technique (the adjoint spectral-element method) considering the full physics of wave propagation. The computations reveal a sensitivity remarkably focused on a small number of elastic parameters and on a small region of the upper mantle. These fundamental properties and the practical advantages of the measurement make the cross-correlation SKS-splitting intensity particularly well adapted for finite-frequency imaging of upper-mantle anisotropy.