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

基本信息

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

项目摘要

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测提供了有关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起源，发现它与大气压力变化有很强的相关性。压力载荷似乎会引起地面倾斜。因此，只要我们使用带有摆的地震仪，水平分量噪声就不可避免。本研究旨在使用高精度激光干涉仪来观测地震面波和地球自由振荡，该干涉仪不受地震仪记录中观测到的噪声的影响。研究结果如下: 1.研制了用于激光干涉仪的碘稳定Nd:YAG激光系统。实现了1O^<13>的频率稳定度。2.研制了包含两个腔室和连接它们的管道的真空系统来容纳干涉仪系统。采用4个波纹管补偿机构，避免大气压力变化的影响。为了保持 1O^<-6> Torr 的真空，我们使用了涡轮分子泵系统。干涉仪基线长度约为15m长。3.激光干涉仪系统安装在名古屋大学犬山观测站，现已准备好观测地震面波和大地震激发的地球自由振荡。