Long Term Borehole Monitoring System (LTBMS)

Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) proposes not only drilling, coring, geological analysis, and geophysical logging, but also a long-term borehole monitoring system (LTBMS) to observe the seismogenic zone. LTBMS will be connected to a seafloor observatory network, to enable real-time monitoring and contribute to reducing the severity of earthquake-disasters.

Development plan

Development of the riser borehole LTBMS started in FY2007. The experimental prototype (EXP) was built for evaluation testing in a land-based well, using the results of the component level tests. After reviewed the EXP test results, the engineering prototype (ENP) will be built and installed in the riser borehole.

Conceptual image of LTBMS

Schematic diagram of long term borehole monitoring system

Technical challenges for the 3,500 m riser hole LTBMS

• High temperature/long life (125°C / 5 years), low power consumption (for multi sensor)
• Safe/reliable deployment (deep well, fault zone, shock resistance, retrieval)
• Coupling to formation (cement, clamp)
• Multi-level/multi-purpose monitoring (seismic, geodetic, hydro geologic), real-time monitoring
• Accurate synchronization (for seismic array), wide frequency range/wide dynamic range
• Miniaturization, system redundancy (fault tolerant)