南沙地块海底地震仪转换横波震相识别最新进展*

doi:10.11978/2015025

摘要/Abstract

摘要： 通过挖掘海底地震仪记录的转换横波信息, 可以促进对地壳岩性、均质性的认识。以南海南沙地块OBS973-1剖面上18个台站的数据为实例, 阐明了海底地震仪横波震相识别的方法。首先对三分量OBS (Ocean Bottom Seismometer )地震数据进行带通滤波、维纳滤波、极化滤波等去噪处理, 然后利用能量扫描法求得极化角进行水平分量坐标旋转, 求取最佳径向分量。数据处理结果表明, 相对于OBS记录的磁罗盘方位角, 能量扫描法求取的极化角更为准确可靠。最后通过OBS973-1地震剖面垂直分量与径向分量上的纵横波走时对比、质点运动轨迹、速度模型试算等手段, 进一步确定了转换横波震相的类别。在南沙地块OBS探测中成功地在10个台站中识别出了PgSs、PnSc、Pms等震相, 不仅可以为下一步横波速度结构模拟提供坚实的数据基础, 而且可以为今后OBS转换横波在其他地区的有效应用与推广提供借鉴。

关键词: 海底地震仪(OBS), 转换横波, 滤波, 水平分量旋转, 南沙地块

Abstract: Using converted shear-wave information recorded by Ocean Bottom Seismometer (OBS) can promote our understanding about lithology and physical properties of crustal rocks. Taking 18 OBS stations along Profile OBS973-1 of Nansha Block in the South China Sea (SCS) as examples, we illustrated the method of OBS converted shear-wave identification. First, noise reduction processing of three-component OBS seismic data was completed using a band-pass filter, Wiener filter and polarization filter. Then, we used energy scanning method to find out the polarization angle, and obtained the optimal radial component data by horizontal component rotation. The results showed that the angle obtained by energy scanning method was more accurate and reliable than the magnetic compass angle recorded by OBS. Finally, the types of converted shear-waves were determined through the comparisons of travel times, particle trajectory and velocity model trial between vertical component and radial component. The method was applied successfully to the experiment in Nansha Block of the SCS for Profile OBS973-1. A few converted shear-wave phase groups, such as PgSs, PnSc and PmS, were identified in 10 OBSs. These results not only provided solid foundation for shear-wave velocity structure, but also offered experience and reference for effective application and promotion of OBS-converted shear-wave in other areas in the future.

Key words: Ocean Bottom Seismometer (OBS), converted shear wave, filter, horizontal components rotation, Nansha Block

张莉, 赵明辉, 丘学林, 王强. 南沙地块海底地震仪转换横波震相识别最新进展^*[J]. 热带海洋学报, 2016, 35(1): 61-71.

ZHANG Li, ZHAO Minghui, QIU Xuelin, WANG Qiang. Recent progress of converted shear-wave phase identification in Nansha Block using Ocean Bottom Seismometers data[J]. Journal of Tropical Oceanography, 2016, 35(1): 61-71.

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南沙地块海底地震仪转换横波震相识别最新进展^*

Recent progress of converted shear-wave phase identification in Nansha Block using Ocean Bottom Seismometers data

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