A Generalized H‐κ Method With Harmonic Corrections on Ps and Its Crustal Multiples in Receiver Functions
A Generalized H‐κ Method With Harmonic Corrections on Ps and Its Crustal Multiples in Receiver Functions
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DOI：
10.1029/2018jb016356
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发表时间：
2019-04
期刊：
影响因子：
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通讯作者：
Jiangtao Li;Xiaodong Song;Pan Wang;Lupei Zhu
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文献类型：
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作者：
Jiangtao Li;Xiaodong Song;Pan Wang;Lupei Zhu
H-κ方法（Zhu & Kanamori，2000，https：//doi.org/10.1029/1999JB900322）已被广泛用于利用接收函数估计地壳厚度（H）和P与S速度比（VP/VS比，κ）。然而，在地壳结构复杂的地区，该方法可能会产生偏差的结果，特别是从倾斜莫霍面和/或地壳各向异性。已经提出了在具有平坦莫霍面的方位角或径向各向异性的情况下的H-κ叠加，但没有提出在具有倾伏各向异性和倾斜莫霍面的情况下的H-κ叠加。在这里，我们提出了一个广义的H-κ方法，称为H-κ-c，它在叠加之前首先校正这些影响。本文考虑了较一般的情况，包括倾伏各向异性和多层倾斜界面，用调和函数校正Ps波及其地壳多次波的到时随后方位角（θ）的变化。系统的综合试验表明，即使在非常复杂的地壳结构下，cosθ和cos 2 θ函数也能很好地拟合到时变化。对后方位角变化的校正显著增强了H-κ堆叠。我们通过将H-κ-c方法应用于中国大陆不同地质背景下的40个永久台站，验证了该方法的可行性。结果表明，谐波校正后有明显改善，多次波更清晰，叠加能更强，H-κ值更可靠。新方法和传统方法之间的H（高达5.0 km）和κ（高达0.09）差异很大，主要发生在地壳结构趋于复杂的山区。当传统方法用于倾斜界面时，我们特别注意系统偏差。该方法简单易行，适用于世界任何地方。
The H‐κ method (Zhu & Kanamori, 2000, https://doi.org/10.1029/1999JB900322) has been widely used to estimate the crustal thickness (H) and the ratio of P to S velocities (VP/VS ratio, κ) with receiver functions. However, in regions where the crustal structure is complicated, the method may produce biased results, arising particularly from dipping Moho and/or crustal anisotropy. H‐κ stacking in case of azimuthal or radial anisotropy with flat Moho has been proposed but not for cases with plunging anisotropy and dipping Moho. Here we propose a generalized H‐κ method called H‐κ‐c, which corrects for these effects first before stacking. We consider rather general cases, including plunging anisotropy and dipping interfaces of multiple layers, and use harmonic functions to correct for arrival time variations of Ps and its crustal multiples with back azimuth (θ). Systematic synthetic tests show that the arrival time variations can be well fitted by cosθ and cos2θ functions even for very complex crustal structures. Correcting for the back azimuthal variations significantly enhances H‐κ stacking. We verify the feasibility of the H‐κ‐c method by applying it to 40 permanent stations in various geological setting across the Mainland China. The results show clear improvement after the harmonic corrections, with clearer multiples and stronger stacking energy, as well as more reliable H‐κ values. Large differences in H (up to 5.0 km) and κ (up to 0.09) between the new and traditional methods occur mostly in mountainous regions, where the crustal structure tends to be more complex. We caution in particular about systematic bias when the traditional method is used in the presence of dipping interfaces. The modified method is simple and applicable anywhere in the world.