ALBERT

Description: Seafloor pressure observations mainly use precise quartz resonant sensors at the present due to its high sensibility. Recently, a new silicon resonant sensor using Micro Electro Mechanical Systems (MEMS) technology has emerged with low-power consumption, compact-size, constant quality, and high sensitivity. High stability is expected due to small size of a sensing unit, and individual difference of each sensors is believed to be small because of using the MEMS technology. Influence of movement of the sensor itself is small due to mechanism of pressure transmission. Nankai Trough seafloor network for earthquakes and tsunamis-net (N-net) will be equipped with the new sensors. Before routine observations using this new sensor, we evaluate performance of the new silicon resonant sensor for seafloor pressure observation. An existing Free-fall pop-up type Ocean Bottom Pressure gauge (OBP) has a quartz resonant sensor. We replaced the sensor to the new silicon sensor, and performed seafloor observations off Boso peninsula near Tokyo. We obtained pressure data from two new sensors. Ambient noise spectra of the new sensor was compared to that of the ordinary sensor which was installed at the same position. The new and ordinary sensors have identical noise level at periods longer than about 50 s. However, the new silicon sensor seems to have higher noise levels at periods between 50 s and 10 s. The new sensor observed sea level fluctuation by volcanic eruption in Tonga and The identical waveforms were obtained from the new and ordinary sensors.