Abstract
In recent years, considerable attention in seismology has been given to the world-wide observation of distant earthquakes and microseims. To observe long period seismic waves caused by distant earthquakes, we have developed an entirely new type of seismometer with a dynamic long period pendulum using a gyroscope. This seismometer is called the gyrotransducer throughout this paper. Our gyrotransducer consists of a gyroscope and an ordinary mass-spring system, and the range of its natural period is about 30∼60sec.
In this paper, we consider an observation system for measuring a vertical seismic motion and examine the amplitude response of a forced vibration which is the most important characteristic of a seismometer. The technical problems of this seismometer are investigated. Among them are mainly the problem of how an ambient temperature change influences the elastic constant of a spring in the seismometer and the problem of what fluctuation the zerolevel of recording suffers due to null-torque. Experimental results obtained in the laboratory and in the seismological station at Tsukuba provide useful data for us to apply this gyrotransducer to a practical seismic observation system.
