Seafloor Rayleigh ellipticity, measured from unoriented data, and its significance for passive seismic imaging in the ocean

IF 2.8 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS
Sanxi Ai, Takeshi Akuhara, Lipeng He, Cheng Xiong, Zhiyong Yan, Yong Zheng
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Abstract

Summary Observations of the seafloor Rayleigh ellipticity contribute to seismic imaging in the ocean. To extract such observables from the arbitrarily oriented ocean-bottom seismometer (OBS) data, we develop an orthogonal-regression based approach to measure the waveform amplitude ratios of the unoriented horizontal and vertical components. The amplitude ratios are then used to calculate the Rayleigh ellipticity (and the sensor orientation angle). The robustness of our method is verified by applications to both the unoriented OBS data and the well oriented on-land seismic data. As we propose to calculate the Rayleigh ellipticity directly from the unoriented three-component data, the measurement process avoids the complexity arising from the surface wave non-great circle effects and uncertainties of the OBS sensor orientation angles. Overall the Rayleigh ellipticity measurements from our method are systematically higher than those by conventional analysis and show less uncertainties. Our analyses suggest that the Rayleigh ellipticity curve (14-60 s), which could be retrieved from the raw broadband OBS data, is effective to constrain the oceanic lithosphere structure, and the accurate measurement of Rayleigh ellipticity curve is important. The potential of seafloor Rayleigh ellipticity for seismic imaging in the ocean is evidenced by a case study of the Japan Basin, the Sea of Japan. Considering the insufficient station coverage in the ocean, the single-station measurement of seafloor Rayleigh ellipticity is of significance for OBS community.
根据无定向数据测量的海底瑞利椭圆度及其对海洋被动地震成像的意义
摘要 对海底瑞利椭圆度的观测有助于海洋地震成像。为了从任意取向的海底地震仪(OBS)数据中提取此类观测数据,我们开发了一种基于正交回归的方法,用于测量非取向水平分量和垂直分量的波形振幅比。然后利用振幅比计算瑞利椭圆度(和传感器方位角)。我们的方法在无定向 OBS 数据和定向良好的陆上地震数据中的应用验证了其稳健性。由于我们建议直接从未定向的三分量数据中计算瑞利椭圆度,因此测量过程避免了由面波非大圆圈效应和 OBS 传感器方位角不确定性引起的复杂性。总体而言,我们的方法测得的瑞利椭圆度系统地高于传统分析方法,且不确定性较小。我们的分析表明,从原始宽带 OBS 数据中获取的瑞利椭圆度曲线(14-60 s)可以有效地约束海洋岩石圈结构,而瑞利椭圆度曲线的精确测量非常重要。海底瑞利椭圆度在海洋地震成像方面的潜力通过对日本海日本盆地的案例研究得到了证明。考虑到海洋的台站覆盖率不足,海底瑞利椭圆度的单台站测量对 OBS 界具有重要意义。
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来源期刊
Geophysical Journal International
Geophysical Journal International 地学-地球化学与地球物理
CiteScore
5.40
自引率
10.70%
发文量
436
审稿时长
3.3 months
期刊介绍: Geophysical Journal International publishes top quality research papers, express letters, invited review papers and book reviews on all aspects of theoretical, computational, applied and observational geophysics.
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