Deep borehole observation can eliminate effectively various earth's surface interferences, providing considerable advantage over other geophysical measurements made at the ground, and improve greatly our capability to detect very small deformations and vibrations in the surrounding strata. This new technology will promote consequently our understanding of presently active geological processes and its relation to earthquakes and tectonics. Based on previous experiences of developing RZB type borehole strainmeter a new multi-component borehole instrument for deep boreholes has been developed. The new system, namely RZB-3 multi-component borehole instrument is a complete package consisting of strain, tilt, strain seismic waves and ground temperature measurement units in a stainless-steel pressure cylinder with 102mm outside diameter. Furthermore, another three channels provide the assistant observation including well temperature, well water level and atmospheric pressure. This new instruments can run at maximum sensitivity to provide strain resolution of 0.1 nanostrain with the maximum of 5×105 nanostrain and tilt resolution of 1 nanorad with the maximum of 5 microrad. Up to now these instruments have observed good tidal signals, strain-steps associated with large earthquakes, and strain changes of geophysical interests. Some details relate to design of the multi-component borehole instruments and the relevant observation data were presented, and primary analyses were discussed as well.
Deep boreholes enable the high S/N ratio geophysical observations for detecting very small tectonic strain, tilt and vibration signals with negligible artificial disturbances and meteorological noises. But the cost of digging deep borehole is very expensive, therefore, the only way is to develop the multi-component borehole instrument to cut down the total cost for establishing of an compositive observation station. During last decade, the borehole strain project has progressed from a small instrumentation research effort to a larger-scale monitoring program.
