A comparison of approaches for the prediction and inversion of surface wave phase delays
A comparison of approaches for the prediction and inversion of surface wave phase delays
复制标题
面波相位延迟预测和反演方法的比较
DOI：
10.1093/gji/ggz096
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发表时间：
2019
影响因子：
2.8
通讯作者：
G. Ekström
中科院分区：
文献类型：
--
作者：
K. Godfrey;C. Dalton;Zhitu Ma;V. Hjörleifsdóttir;G. Ekström
进行了一项受控实验，以研究表面波断层扫描中表面波传播的不同假设的影响。使用谱元法生成了 42 个地震和 190 个台站以及两个不同的 3-D 地球模型的合成地震图。使用聚类分析技术测量了 35-250 秒的基模瑞利波和洛夫波传播时间。我们使用大圆射线近似、精确射线理论和二维有限频率理论预测了这些路径的瑞利波和拉夫波传播时间。通过计算所有路径的失配和“获胜者”方法，根据测量结果评估预测方法，该方法识别最适合预测方法的路径部分。 Misfits 表明对于周期 > 50 秒的瑞利波的预测方法之间几乎没有什么区别，而有限频率理论对于周期 > 125 秒的勒夫波的预测方法更优越。 “获胜者”方法表明，精确射线理论在短周期内更优越，而有限频率理论在长周期内更优越。然而，当仅考虑大圆射线和有限频率方法时，我们发现每种方法的优越性和不优越性一样多。我们使用两种反演方法通过测量求解相速度图：大圆射线近似和有限频率理论。虽然使用两种方法生成的输出图通常相似，但对方差减少以及与输入图的相关性的分析表明，大圆射线理论反演产生的相速度图可以更好地解释测量结果并与输入图匹配。根据我们进行的测试和获得的结果，我们建议使用大圆射线理论而不是二维有限频率理论来分析表面波相位延迟，至少在全球范围内。
A controlled experiment was performed to investigate the influence of different assumptions made about the propagation of surface waves in surface wave tomography. Synthetic seismograms were generated using the spectral element method for 42 earthquakes and 190 stations and two different 3-D earth models. Fundamental-mode Rayleigh and Love wave traveltimes were measured using a cluster analysis technique for periods 35–250 s. We predicted Rayleigh and Love wave traveltimes for these paths using the great-circle ray approximation, exact ray theory and 2-D finite-frequency theory. Prediction approaches were evaluated with respect to the measurements by calculating misfit for all paths and with a ‘winner’ approach, which identifies the fraction of paths that are best fit by a prediction approach. Misfits indicated little difference between prediction approaches for Rayleigh waves at periods >50 s and that finite-frequency theory is superior for Love waves at periods >125 s. The ‘winner’ approach indicated that exact ray theory is superior at short periods, whereas finite-frequency theory is superior at long periods. However, when only the great-circle ray and finite-frequency approaches were considered, we found that each approach was superior as often as it was not. We solved for phase velocity maps with the measurements using two inversion approaches: the great-circle ray approximation and finite-frequency theory. While output maps generated using both approaches were generally similar, analysis of the variance reduction and the correlation with the input map showed that the great-circle ray theory inversion yielded phase velocity maps that better explained the measurements and matched the input maps. On the basis of the tests we have performed and the results we have obtained, we recommend using great-circle ray theory instead of 2-D finite-frequency theory for the analysis of surface wave phase delays, at least on the global scale.