Estimation of azimuthal anisotropy in the NW Pacific from seismic ambient noise in seafloor records
Estimation of azimuthal anisotropy in the NW Pacific from seismic ambient noise in seafloor records
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DOI：
10.1093/gji/ggu240
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发表时间：
2014-10
影响因子：
2.8
通讯作者：
A. Takeo;D. Forsyth;D. Weeraratne;Kiwamu Nishida
中科院分区：
文献类型：
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作者：
A. Takeo;D. Forsyth;D. Weeraratne;Kiwamu Nishida
我们通过对PLATE项目部署在太平洋西北部的八个海底地震仪和九个差压计的连续记录进行互相关，分析了地震环境噪声中的背景表面波。在利用互相关函数估计差压计的时钟延迟和仪器相位响应后，通过波形拟合测量了基模、第一高阶和第二高阶瑞利波以及基模Love波在3-40 s周期范围内的阵列区域内的平均相速度。然后，我们在5-25 s的周期范围内测量了每对台站的基模和第一高阶瑞利波的相速度异常，并校正了水深变化的影响。这些地震异常反映了台阵东部存在较强的方位各向异性。最大速度的方向约为N35 <$E的化石海底扩张方向垂直于磁线理从古三联点在这个位置。地幔中剪切波速度各向异性的峰-峰强度为0.7%。
We analysed background surface waves in seismic ambient noise by cross-correlating continuous records of eight ocean bottom seismometers and nine differential pressure gauges deployed in the northwestern Pacific Ocean by the PLATE project. After estimating the clock delay and instrumental phase responses of differential pressure gauges by using cross-correlation functions, we measured average phase velocities in the area of the array for the fundamental-, first higher- and second higher-mode Rayleigh waves, and the fundamental-mode Love waves at a period range of 3–40 s by waveform fitting. We then measured phase-velocity anomalies of fundamental-mode and first higher-mode Rayleigh waves for each pair of stations at a period range of 5–25 s, and corrected the effect of variation in water-depths. The seismic anomalies imply the presence of strong azimuthal anisotropy beneath the eastern part of array. The direction of maximum velocity is approximately N35 ◦ E in the fossil seafloor spreading direction perpendicular to magnetic lineations from the ancient triple junction at this location. The peak-to-peak intensity of shear-wave velocity anisotropy in the mantle is ∼ 7 per cent.