Performance tests of sensors for Long-Term Borehole Monitoring System

Long-Term Borehole Monitoring System (LTBMS) is a one of projects of the Integrated Ocean Drilling Program (IODP), Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE). A series of LTMBS sensors including a volumetric strainmeter, broadband seismometer, tiltmeter, geophone, accelerometer and thermistor array have been planned to be installed to collect broadband dynamics for understanding the mechanism of mega-thrust earthquakes which have occurred repeatedly in the Nankai Trough plate subduciton area. LTMBS sensors were developed and improved by JAMSTEC project team to resist vortex induced vibration (VIV). After development was completed, we carried out performance tests including vibration and shock tests. We also carried out noise evaluation tests before and after vibration and shock tests. As a result of a series of performance tests, we confirmed that anti-vibration mechanism for VIV was working as expected by comparison of Power Spectral Density (PSD) before and after the vibration and shock tests.