Radially anisotropic structure beneath the Shikoku Basin from broadband surface wave analysis of ocean bottom seismometer records
Radially anisotropic structure beneath the Shikoku Basin from broadband surface wave analysis of ocean bottom seismometer records
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DOI：
10.1002/jgrb.50219
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发表时间：
2013-06
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影响因子：
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通讯作者：
A. Takeo;Kiwamu Nishida;T. Isse;H. Kawakatsu;H. Shiobara;H. Sugioka;T. Kanazawa
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文献类型：
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作者：
A. Takeo;Kiwamu Nishida;T. Isse;H. Kawakatsu;H. Shiobara;H. Sugioka;T. Kanazawa
我们已经分析了宽带面波数据部署在四国盆地在菲律宾海东北部的海底地震仪，以确定径向各向异性的上地幔结构下的海洋盆地。我们首先将噪声相关方法应用于连续微地震记录，以获得周期为7-29 s的基模和第一高模瑞利波以及基模Love波的相速度。在较长的周期下，我们将阵列分析方法应用于远震表面波，以获得周期为29-117 s的基模Rayleigh波和Love波的相速度。使用这些宽带相速度测量，我们确定了从地壳到四国盆地下方低速带（LVZ）的一维径向各向异性结构，而无需假设上地幔的先验结构。最终的结构模型（SB-RA 10）有一个从莫霍面到深度为1040 km的高速盖，在更深的地方有一个LVZ。在40-70 km深度范围内，S波速度降低6%~ 10%.这种速度的大幅度降低表明，这些层之间的晶粒尺寸存在很大差异，或者表明LVZ中存在部分熔体或水。此外，在上地幔中还观察到4%-5%（VSH>VSV）的强径向各向异性，这种各向异性在低纬带中可能更强。
We have analyzed broadband surface wave data from ocean bottom seismometers deployed in the Shikoku Basin in the northeastern Philippine Sea to determine the radially anisotropic uppermost mantle structure beneath this oceanic basin. We first applied noise correlation method to continuous microseismic records to obtain phase velocities for fundamental‐mode and first higher‐mode Rayleigh waves and fundamental‐mode Love waves at periods of 7–29 s. At longer periods, we applied an array analysis method to teleseismic surface waves to obtain phase velocities of fundamental‐mode Rayleigh and Love waves at periods of 29–117 s. Using these broadband phase velocity measurements, we have determined the one‐dimensional radially anisotropic structure from the crust to the low velocity zone (LVZ) beneath the Shikoku Basin without assuming a priori structure in the uppermost mantle. The final structural model (SB‐RA10) has a high‐velocity lid from the Moho to a depth of ∼40 km, with an LVZ at greater depths. S wave velocities decrease by 6%–10% at a depth range of ∼40–70 km. This large decrease in velocity suggests that there is either a large difference in grain size between these layers or indicates the presence of partial melt or water in the LVZ. Furthermore, strong radial anisotropy of 4%–5% (VSH>VSV) is observed in the uppermost mantle, which may be stronger in the LVZ.