Development of a High-Gain Rotational-Motion Seismograph

点击翻译按钮获取中文摘要

The aim of this research program is to develop a new fiber optic gyro for measuring rotational motion of seismic waves. The target value of sensitivity is less than 10^<-9> rad/sec for portable type and 10^<-1> rad/sec for long-period type. The frequency ranges are 0.02 Hz - 50 Hz for portable type and 0.01 HZ - 1 Hz for long-period type. Fiber optic gyro has the following advantages. It is easy to increase sensitivity by enlarging the size of the fiber coil, and it has no moving elements which make internal noise. Because of these advantages, we select a fiber optic technology as a basic technology of the rotational-motion seismograph. We have succeeded in developing a triaxial rotational seismograph using three high-gain fiber optic gyros whose internal noise is reduced down to 5 x 10^<-9> rad/sec. To confirm the performance of the new high-gain rotational seismograph, we perform a parallel operation using another rotational sensor based on a different technology. We used a rotational sensor model R1 produced by EENTEC.The R-1 is in a line of sensors using state-of-the-art electro chemical technology, and the resolution is 5 x 10^<-7> rad/sec at 1 Hz. Anyway, we have succeeded in developing the new high-gain rotational seismograph which can record local small earthquakes.