Development on long term borehole monitoring system for earthquake and geodetic research

The deep sea scientific riser drilling vessel capable of riser drilling at 2,500 meter water depth, CHIKYU started its scientific operation from 2007, as the first riser drilling platform of the Integrated Ocean Drilling Program, to contribute such important scientific program as the Nankai Trough Seismogenic Zone Experiment and the Japan Trench Fast Drilling. Any of these expeditions involve technological and operational difficulties related to strong current, high wave, strong wind, deep water, and deep penetration. This paper describes the development of long term borehole monitoring system from view points of technical difficulties on deploying it at deep water, deep hole, and strong current.