Abstract
Observation in deep boreholes enables the high S/N ratio observations for detecting very small signals without both artificial noises and meteorological disturbances. Therefore, we have developed multi-component borehole instruments. The instruments are composed of 7 strainmeters (4 horizontal, 2 inclined and one vertical), 2 tiltmeters, 3 seismometers, 4 magnetometers and a quartz thermometer of high resolution. Resolution of A/D conversion of the instruments is 22 bits and sampling rates are 200 Hz for seismometers, 20 Hz for strainmeters, 10 Hz for tiltmeters and 1 Hz for thermometer.
We installed the instruments by cementing at the bottom of the deep boreholes with expansion grout and have constructed borehole array stations. The deepest borehole (JRJ) is 1030m deep and the second (BYB) is 1020 m. Data obtained from the sensors in the instruments are transmitted to the surface by using only one coaxial cable and then sent to our institute(TRIES). We have also constructed data base of collected data from the borehole stations.
We introduce some interesting results obtained from these borehole array stations and how valuable the deep borehole observations are. We also discuss continuous observation forcrustal activity in future.
