Deep seafloor borehole observatories for seismogenic zone monitoring

Real-time borehole observation system for seismogenic zone monitoring called long-term borehole monitoring system (LTBMS) was developed to give better access to the seismogenic faults nucleating earthquakes while avoiding observational effects of dampening by shallow soft sediment and oceanographic noise commonly experienced in the seafloor observation. Installation of the LTBMS has been conducted in two location in the Nankai Trough, Japan, near the rupture zone of the Tonankai earthquakes during the NantroSEIZE program of the Integrated Ocean Drilling Program (IODP). The LTBMSs were connected to the real-time seafloor cabled observation network called DONET and initial data from the LTBMS demonstrated their ability to capture slow crustal deformation and high fidelity earthquake records that are difficult by seafloor observatories.