Detection of the oscillations of Earth's core by a collaboration observation with superconducting gravimeters and laser strain meters-Comparison between the Kamioka site and Matsushiro site-

通过超导重力仪和激光应变仪的协作观测来检测地核的振动～神冈遗址与松代遗址的比较～

• 批准号: 16340134
• 负责人: SATO Tadahiro
• 金额: $ 10.69万
• 依托单位: National Astronomical Observatory
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16340134/
• 关键词: Superconducting gravimeter; Laser strain meter; Absolute gravimeter; Tidal Strain; Earth's normal modes; Effect of the atmospheric pressure; Effect of the ocean; Strain step; Effect of the tsunami; 絶対重力系; 地球のノーマルモード; 歪ステップ; 2004スマトラ地震; 低周波地球自

This research project was planed to detect weak normal mode signals from the Earth's core based on the observations with two superconducting gravimeters (SGs) at Kamioka and Matsushiro and by a comparison between the SG and laser strain meters set at Kamioka. H. Ikeda of the Tsukuba University and Severine Rosat of JSPS fellow did join to this project as the cooperative researchers though the term of the project.We have done the followings ;1.Developing a new non-linear analysis method for the normal mode analysis, which can treat both the frequency and Q-value of normal modes as unknown parameters,2.Analysis of the SG records mainly of the Sumatra-Andaman earthquake (Mw=9.0-9.3), which were obtained from the world wide SG network including Kamioka, Matsushiro and the Syowa Station in Antarctica,3.Improving the quality of the laser strain meter and the analysis of the records of the Sumatra-Andaman earthquake,4.Improving the estimation accuracy of gravity effect of the regional atmosph … More eric air mass changes,5.Investigating the accuracy of modern global ocean tide models, which are used in the correction for the ocean tides, and also studying the non-tidal sea surface height variations by comparing some model computation results with the actual data obtained from the ocean bottom pressure measurements in Off-Sanriku,6.Improving the calibration accuracy of the scale factor of SG by using an absolute gravimeter.In December 26th 2004, two months later when the SG was newly installed at Kamioka, the Sumatra-Andaman earthquake occurred. The fundamental radial mode _oS_o, which consists of a global deformation of the Earth with changes in its circumference, has been strongly excited by this event and its time decay has been observed till the occurrence of the second Sumatra event in March 28th 2005 at many of SG sites. A notable result obtained by this research project is; we have succeeded to reveal that the _oS_o mode shows a geographical amplitude distribution depending on not only the latitude but also on the longitude, which may reflect a large scale lateral inhomogeneity in the Earth's structure. The observed geographical pattern is consistent with the model prediction based on a 3-D seismic tomography model.Based on the two SG data sets for the Sumatra-Andaman event, which were obtained at Strasbourg (France) and Canberra (Australia) and using the new analysis method developed by this project, we have tried to find out such weak core signals as the Slichter triplets and the core undertones. Although we found some peaks to be closely related to these modes, the analysis results have not revealed such inner core signals yet, because some spectrum peaks fond are not observed commonly at these two sites.The effect of tsunami waves excited by the Sumatra event was also observed by several instruments set at the Syowa Station including the SG. We have compared the predicted tsunami effects with those observed from the SG and SST-1. Improvement of the accuracy of the bathymetry around the Syowa station is essential to improving the comparison accuracy between the observations and predictions. Less

本研究计划根据位于神冈和松代的两台超导重力仪（SG）的观测结果，并通过SG和位于神冈的激光应变仪之间的比较，探测来自地核的弱简正模信号。H.筑波大学的池田和JSPS研究员Severine Rosat作为合作研究者参与了本项目。1.提出了一种新的非线性模态分析方法，该方法可以将模态频率和Q值作为未知参数，2.苏门答腊-安达曼地震SG记录分析（Mw=9.0-9.3），其从包括南极洲的神冈、松代和昭和站的全球SG网络获得，3.提高激光应变仪的质量和苏门答腊-安达曼地震记录的分析; 4.提高区域大气重力效应的估计精度; ...更多信息 5.考察了现代全球海潮模式在海潮改正中的准确性，并通过将一些模式的计算结果与Off-Sanriku洋底压力测量的实际数据进行比较，研究了非潮汐海面高度的变化。6.利用绝对重力仪提高SG标度因子的标定精度2004年12月26日，SG新安装在神冈的两个月后，苏门答腊-安达曼地震发生。基本径向模_oS_o是由地球的整体形变及其周长的变化组成的，它被这次事件强烈激发，并且在2005年3月28日第二次苏门答腊事件发生之前，在许多SG站点上都观察到了它的时间衰减。本研究项目取得的一个显著结果是：我们成功地揭示了_oS_o模的地理振幅分布不仅依赖于纬度，而且依赖于经度，这可能反映了地球结构中的大尺度横向不均匀性。根据在法国斯特拉斯堡和澳大利亚堪培拉获得的苏门答腊-安达曼地震SG数据集，利用本项目开发的新的分析方法，试图找出诸如Slichter三联体和核底等弱核信号。虽然我们发现一些峰与这些模式密切相关，但分析结果还没有揭示这样的内核信号，因为一些谱峰在这两个站点并不常见。苏门答腊事件激发的海啸波的影响也被设置在昭和站的几个仪器，包括SG。我们比较了预测的海啸影响与SG和SST-1观测到的影响。提高昭和站周围水深测量的准确性对于提高观测和预测之间的比较准确性至关重要。少

项目成果

Parameters of the fluid core resonance inferred from superconducting gravimeter data

• DOI: 10.1016/j.jog.2004.07.016
• 发表时间: 2004-10
• 期刊: Journal of Geodynamics
• 影响因子: 2.3
• 作者: Tadahiro Sato;Y. Tamura;Koji Matsumoto;Y. Imanishi;H. McQueen

神岡レーザー伸縮計のフリンジーひずみ変換方式の改良

神冈激光引伸计条纹应变转换方法的改进

• 发表时间: 2006
• 期刊: 測地学会誌 52・3
• 作者: 早河秀章;竹本修三;由井智志;新谷昌人;高森昭光;森井亙;大橋正健
• 通讯作者: 大橋正健

A 100 m laser strainmeter system in the Kamioka Mine, Japan, for precise observations of tidal strains

• DOI: 10.1016/j.jog.2005.08.009
• 发表时间: 2006
• 期刊: Journal of Geodynamics
• 影响因子: 2.3
• 作者: S. Takemoto;Hideo Momose;A. Araya;W. Morii;J. Akamatsu;M. Ohashi;A. Takamori;S. Miyoki;T. Uchiyama;D. Tatsumi;T. Higashi;S. Telada;Y. Fukuda

A geophysical interpretation of the secular displacement and gravity rates observed at Ny-Alesund, Svalbard in the Arctic -Effects of post-glacial rebound and present-day ice melting

对北极斯瓦尔巴特群岛尼奥勒松观测到的长期位移和重力率的地球物理解释 - 冰期后反弹和当今冰融化的影响

• 发表时间: 2006
• 期刊: Geophysical Journal International 165
• 作者: S.Rosat;S.Watada;T.Sato;Kazunari Nawa 他7名;Tadahiro Sato 他7名
• 通讯作者: Tadahiro Sato 他7名

Estimating the Fluid Core Resonance Based on Strain Observation.

基于应变观测估计流体核心共振。

• 发表时间: 2006
• 期刊: Journal Geodynamics 41
• 作者: J.Ping;T.Tsubokawa;Y.Tamura;K.Heki;K.Matsumoto;T.Sato
• 通讯作者: T.Sato