Observation of Seismic Surface Waves and Earth's Free Oscillations Using a High-Precision Laser Interferometer

使用高精度激光干涉仪观测地震表面波和地球自由振荡

• 批准号: 08454121
• 负责人: YAMADA Isao
• 金额: $ 3.84万
• 依托单位: Nagoya University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08454121/
• 关键词: laser interferometer; stabilized laser; surface waves; Earth's free oscillations

Observations of seismic surface waves and Earth's free oscillations give precious informationon internal structure of the Earth. However, seismic data that have mainly been analyzed are vertical component since horizontal components usually contain very large low-frequency noise originated from ground tilting. We have investigated the origin of horizontal component noise in another research and have found that it has a strong correlation with atmospheric pressure variation. It seems that pressure loading gives rise to ground tilting. Therefore the horizontal component noise is inevitable as long as we use seismometers with pendulum.This research was aimed to observe seismic surface waves and Earth's free oscillations using a high-precision laser interferometer, which is free from the noise observed in seismometer records. The results are as follows :1.Iodine-stabilized Nd : YAG laser system was developed to use for a laser interferometer. Frequency stability of 1O^<13> were achieved.2.Vacuum system with two chambers and pipes connecting them was developed to contain interferometer system. Compensation mechanism using 4 bellows was adopted to avoid the effect of atmospheric pressure variations. To maintain a vacuum of 1O^<-6> Torr we used a turbo-molecular pomp system. Length of interferometer base line is about 15m length.3.The laser interferometer system was installed at Inuyama observation station of Nagoya University, It is now ready to observe seismic surface waves and Earth's free oscillations excited by large earthquakes.

对地震表面波和地球自由振荡的观察给出了珍贵的地球内部结构。但是，主要分析的地震数据是垂直组件，因为水平成分通常包含非常大的低频噪声，源自地面倾斜。我们在另一项研究中研究了水平成分噪声的起源，发现它与大气压变化有很强的相关性。似乎压力加载会导致地面倾斜。因此，只要我们使用悬臂的地震仪，水平成分噪声是不可避免的。这项研究的目的是使用高精度激光干涉仪观察地震表面波和地球的自由振荡，这在地震仪记录中没有观察到的噪声。结果如下：1。碘稳定的ND：YAG激光系统用于激光干涉仪。实现了1o^<13>的频率稳定性。2.Vacuum系统具有两个腔室和连接它们的管道以包含干涉仪系统。采用了4卷曲的补偿机制，以避免大气压力变化的影响。为了维持1o^<-6> Torr的真空吸尘器，我们使用了涡轮分子蓬松系统。干涉仪基线的长度约为15m的长度。3。激光干涉仪系统安装在纳戈亚大学的Inuama观察站，现在可以观察到地震表面波和大地震激发地球的自由振荡。

项目成果

Naoki Suda: "Earths background free oscillations" Science. 279. 2089-2091 (1998)

Naoki Suda：“地球背景自由振荡”科学。

Akito Araya: "Iodine-stabilized 633-nm He-Ne laser for lorg-baseline interferometer" Jpn.J.Appl.Phys.36. 426-428 (1997)

Akito Araya：“用于 lorg 基线干涉仪的碘稳定 633 nm He-Ne 激光器”Jpn.J.Appl.Phys.36。

Suda, N., K.Nawa and Y.Fukao: "Earth's background free oscillations" Science. 279. 2089-2091 (1998)

Suda, N.、K.Nawa 和 Y.Fukao：“地球背景自由振荡”科学。

Araya, A.: "Iodine-stabilized 633-nm He-Ne laser for long-baseline interferometers" Jpn.J.Appl.Phys.36. 426-428 (1997)

Araya, A.：“用于长基线干涉仪的碘稳定 633 nm He-Ne 激光器”Jpn.J.Appl.Phys.36。