Development of Borehole Seismometer Using Conical Pendulum to Three-Component Velocity Measurement

The aim of this study is to develop a small, inexpensive borehole seismometer that can accurately measure the shot-period velocity signal of three directions. The prototype developed in prior research is composed of a biaxial horizontal electromagnetic sensor in conical pendulum form and a vertical electromagnetic sensor installed on the pendulum axis. The performance of the prototype has been verified experimentally, however, the accuracy of the measurement became degraded due to the elastic vibration and residual vibration of the pendulum axis. As a countermeasure for this problem, the prototype has been improved such as increasing the rigidity of the pendulum axis and adding a magnetic attenuation. In the paper, the performance of the improved prototype was evaluated based on the verification experiment results