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.

地震面波和地球自由振荡的观测提供了关于地球内部结构的宝贵信息。然而，主要分析的地震数据是垂直分量，因为水平分量通常包含源自地面倾斜的非常大的低频噪声。我们在另一项研究中调查了水平分量噪声的来源，发现它与大气压力变化有很强的相关性。压力荷载似乎引起了地面倾斜。本研究的目的是利用高精度激光干涉仪观测地震面波和地球自由振荡，消除地震仪记录中的噪声。研究结果如下：1.研制了用于激光干涉仪的碘稳频Nd：YAG激光系统。频率稳定度达到10 ^<13>。2.研制了一种双腔真空系统，该系统包括两个腔室和连接腔室的管道，用于容纳干涉仪系统。采用4个波纹管的补偿机构，以避免大气压力变化的影响。为了保持10 μ Torr的真空<-6>，我们使用涡轮分子泵系统。3.激光干涉仪系统安装在名古屋大学的犬山观测站，可以观测地震面波和大地震激发的地球自由振荡。

项目成果

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。

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

Naoki Suda：“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。

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。