Study on refinements of the highly sensitive/wide band servo-type seismometer using the astatic rotational pendulum

这项研究的目的是研制一种高灵敏度/宽带地震仪，用于全球地震学的新阶段。地震仪测量的加速度应在10^&lt；-9 m/S以下，频率从0.003赫兹到100赫兹。我们的研究成果如下：1.研制了稳定度小于10^~(-6)、噪声为-130 dBV、频率在1赫兹以上的直流电源。2.研制了三台实用的旋转摆地震仪。地震仪配备了一个与钟摆重量对应的浮子计数器来校正重量处大气压力变化的影响，并配备了一个腔体来隔离大气压力的变化。3.低噪声直流电源和没有腔体的地震仪能够测量高达10^&lt；-10&gt；(m/S)/srt(赫兹)的噪声水平，几乎克服了STS-II的噪声水平。4.为了考虑在湿度较大的地下隧道中的观测，研制了使用光纤电缆进行激光输入和输出的激光标尺。因为像激光二极管这样的有源器件不适合这样的隧道。作为热源的激光和光电二极管可以通过光缆放置在距离标尺很远(例如1公里)的地方。它们的热效应与地震仪的低频噪声有关。5.利用自行研制的地震仪在Spring-8场地进行了地面背景振动噪声垂直分量的观测。观测结果表明，在0.1赫兹以下，该地震仪的低频噪声水平为10^lt；-7(m/S)/srt(Hz)。这一噪声水平比CMG-3T地震仪的噪声水平大几倍，与CMG在0.1赫兹以上的噪声水平几乎相同。

The aim of this study is development of a highly-sensitive/wide-band seismometer utilized for a new stage on global seismology. The seismometer should measure acceleration under 10^<-9> m/s in a frequency from 0.003Hz to 100Hz. We show the results of our study below.1.The DC power supply, having stability of less than 10^<-6> and noise of -130 dBV in a frequency over 1Hz, was developed.2.Three practical seismometers using the rotational pendulum were built. The seismometer equips a float counter to a pendulum weight to correct the effect of an atmosphere pressure change at the weight, and a chamber to isolate an atmospheric pressure change.3.The seismometer with the low noise DC power supply and without the chamber was able to measure as much as a noise level of 10^<-10>(m/s)/Sqrt(Hz) that is almost overcoming that of STS-II.4.To consider observations in an under ground tunnel that has much humidity, the laser scale employing optical fiber cables for a laser input and outputs was developed. Because the active device like a laser diode is not suitable for such tunnel. The laser and photo diodes as thermal sources could be far placed (e.g.1km) from the scale by the fiber cables. The thermal effect from them, related to the low frequency noise of the seismometer, could be reduced.5.The observation of the vertical component of earth back ground vibration noise using our developed seismometer was carried out at the SPring-8 site. The results of the observations showed the noise level of the seismometer was 10^<-7>(m/s)/Sqrt(Hz) in a low frequency side under 0.1Hz. This noise level was several times larger than that of CMG-3T seismometer and almost the same as CMG over 0.1Hz.