Construction of System for Seismic Observation in Deep Borehole (SODB) - Development of Multi-depth, High-temperature/pressure resistance seismometer

The development of a high quality system for seismic observation in deep boreholes, the installation process at the NIIT site, and the data sharing plan for this observation were explained. The key points of the development were high temperature resistance (150 degrees Celsius), high pressure resistance (30 MPa), and a high dynamic/wide frequency range seismometer which allows for observation of micro-tremor to strong motions as well as a cascade-connection-type borehole seismometer, which allows multiple probes to be set at several depths in a single borehole. The developed system consists of broadband (0.1-50 Hz) and high dynamic range (up to 1000 gal) seismometer with electronic parts on the ground and only the pendulum part in the borehole (it became a servo-type seismometer). Durability and maintenance may be issues in the future. (author)