| 基于旋转微椭地球模型的内核平动振荡三重谱线理论模拟与实验探测 |
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| 引用本文： | 江颖,徐建桥,孙和平,刘子维,李辉.基于旋转微椭地球模型的内核平动振荡三重谱线理论模拟与实验探测[J].地球物理学报,2016,59(8):2754-2764. |
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| 作者姓名： | 江颖 徐建桥 孙和平 刘子维 李辉 |
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| 作者单位： | 1. 中国地震局地震研究所, 中国地震局地震大地测量重点实验室, 武汉 430071;2. 中国科学院测量与地球物理研究所大地测量与地球动力学国家重点实验室, 武汉 430077 |
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| 基金项目： | 科研院所基本科研业务费（中国地震局地震研究所所长基金）（IS201526225），国家自然科学基金（41404064，41374088），大地测量与地球动力学国家重点实验室开放基金（SKLGED2015-1-2-EZ），地震行业科研专项（201508009）联合资助. |
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| 摘 要： | 本文基于旋转微椭地球模型,采用简正模理论计算了地球内核平动振荡三重谱线的本征周期,理论上系统研究了地球内部介质(包括密度、地震波速等)分布异常对三重谱线本征周期的影响,计算了不同的内外核密度差和地核中的不同的P/S波速对应的内核平动振荡理论三重谱线周期;利用全球分布的9个超导台站,迭积每个台站长达54个月的高精度超导重力仪数据,在亚潮汐频段(0.162~0.285cph)检测内核平动振荡三重谱线.结果发现,三重谱线本征周期对内外核边界的密度跳跃非常敏感,随着密度差的增加,以类似于双曲线的特征减小;无论是采用地球质量不变的方法还是采用浮力频率为常数的方法,计算得到的三重谱线本征周期结果相差较小,且随着内外核密度差的增大,差距逐渐减小;内、外核P波波速分布异常对三重谱线周期的影响基本相当,内核S波波速分布异常比P波波速分布异常对三重谱线周期的影响小1个量级;探测到一组信噪比较高且满足谱峰分裂特征的三重谱线的信号(0.19281,0.21456和0.24151cph),有极大的可能是来自于内核平动振荡.基于探测结果可以推断实际的地球模型其内外核密度差应该介于PREM模型和1066A地球模型之间,更接近于1066A模型.
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| 关 键 词： | 内核平动振荡 超导重力仪 三重谱线 积谱密度 |
| 收稿时间： | 2015-09-18 |
Theoretical calculation and experimental detection of the inner core translational triplet based on a rotating,slightly elliptical Earth model |
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| JIANG Ying,XU Jian-Qiao,SUN He-Ping,LIU Zi-Wei,LI Hui.Theoretical calculation and experimental detection of the inner core translational triplet based on a rotating,slightly elliptical Earth model[J].Chinese Journal of Geophysics,2016,59(8):2754-2764. |
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| Authors: | JIANG Ying XU Jian-Qiao SUN He-Ping LIU Zi-Wei LI Hui |
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| Institution: | 1. Key Laboratory of Earthquake Geodesy, Institute of Seismology, China Earthquake Administration, Wuhan 430071, China;2. State Key Laboratory of Geodesy and Earth's Dynamic, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China |
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| Abstract: | In this study, the eigenperiods of inner core translational oscillations were calculated using normal modes theory based on a rotating, slightly elliptical Earth model, and the effects of the Earth's interior medium (including its density and seismic velocity) on the Slichter mode eigenperiods were investigated systematically. In particular, the eigenperiods of the triplet were calculated based on different density jumps and different P/S-wave velocities at the inner-outer core boundary (ICB), and the triplet was searched in the subtidal band (0.162~0.285 cph) by stacking 54 months of high-precision superconducting gravimeter (SG) observations from nine stations. The results indicate that the eigenperiods are sensitive to the density jump at the ICB, and they exhibited significant reductions (similar to hyperbolic characteristics) when the density difference at the ICB was increased. Moreover, similar results were found regardless of whether the mass of the Earth or the Brunt-Väïsälä frequency was maintained constant, although the difference between the eigenperiods obtained using the two different methods was smaller for a greater density difference at the ICB. Changes in P-wave velocity of the inner and outer cores affected eigenperiods in an almost identical manner; however, the effects of changes in S-wave velocity were one order of magnitude smaller than those caused by changes in P-wave velocity. One group of signals with high signal-to-noise ratios was found, consistent with the characteristics of the triplet. Although the results are confusing, group 2 (0.19281, 0.21456 and 0.24151 cph) may be related to the inner core translational oscillations. Based on these results it can be deduced that the density difference at the ICB for the real Earth model lies somewhere between those for the PREM and 1066A Earth models, but closer to the 1066A Earth model. |
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| Keywords: | Slichter mode Superconducting gravimeter Triplet Product spectra density |
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