A Second Look at Low-Frequency Marine Vertical Seismometer Data Quality at the OSN-1 Site off Hawaii for Seafloor, Buried, and Borehole Emplacements
A Second Look at Low-Frequency Marine Vertical Seismometer Data Quality at the OSN-1 Site off Hawaii for Seafloor, Buried, and Borehole Emplacements
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夏威夷附近 OSN-1 站点低频海洋垂直地震仪数据质量的二次审视，用于海底、埋地和钻孔安置
DOI：
10.1785/0120050234
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发表时间：
2006
影响因子：
3
通讯作者：
S. Bolmer
中科院分区：
文献类型：
--
作者：
W. Crawford;R. Stephen;S. Bolmer
我们改善海洋低频（1 - 100兆赫）垂直地震仪数据减去噪音产生的倾斜下的流体流动和海底变形下的海洋表面重力波。我们从垂直通道和其他对噪声源更敏感的数据通道之间的相干性和传递函数对噪声进行建模：用于倾斜的水平地震仪组件和用于海浪的压差计。我们从OSN-1深海试验场的三个相邻的海底宽带地震计站中减去噪声：一个位于海底，另一个埋在1米深的沉积物中，第三个夹在海底以下248米的钻孔中。海底海流产生海底传感器倾斜噪声，而潮汐驱动的流体泵送产生钻孔传感器倾斜噪声。减去倾斜噪声后，海底传感器上1至60 mHz之间的垂直通道噪声水平可降低35 - 40 dB，钻孔传感器上1至10 mHz之间的垂直通道噪声水平可降低15 - 20 dB。减去海浪噪声，所有仪器上的噪声水平在4和20 mHz之间进一步降低了5 - 15 dB。在减去倾斜和海浪噪声后，在低于30 mHz的频率下，海底垂直信道比埋地传感器垂直信道安静5 - 10 dB。校正后的钻孔垂直通道具有与海底和埋地10 mHz以上类似的噪声水平，但噪声在较低频率下迅速增加，这可能是由于潮汐驱动流体流动下的垂直振动。
We improve marine low-frequency (1–100 mHz) vertical seismometer data by subtracting noise generated by tilting under fluid flow and by seafloor deformation under ocean-surface gravity waves. We model the noise from the coherency and transfer functions between the vertical channel and other data channels that are more sensitive to the noise sources: the horizontal seismometer components for tilting and a differential pressure gauge for ocean waves. We subtract noise from three adjacent seafloor broadband seismometer stations at the OSN-1 deep-ocean test site: one sitting on the seafloor, another buried 1 m deep in sediments, and the third clamped in a borehole 248 m beneath the seafloor. Seafloor currents generate the seafloor sensor tilt noise, whereas tidally driven fluid pumping generates the borehole sensor tilt noise. Subtracting the tilt noise reduces the vertical channel noise levels by 35–40 dB between 1 and 60 mHz on the seafloor sensor and by 15–20 dB between 1 and 10 mHz on the borehole sensor. Subtracting the ocean-wave noise further reduces the noise level on all instruments by 5–15 dB between 4 and 20 mHz. After subtracting tilt and ocean-wave noise, the seafloor vertical channel is 5–10 dB quieter than the buried sensor vertical channel at frequencies below 30 mHz. The corrected borehole vertical channel has a similar noise level to the seafloor and buried sites above 10 mHz, but noise increases rapidly at lower frequencies, probably because of vertical strumming under tidally driven fluid flow.