[J07-P] Poster

[J07-P-06] Characteristics of a quartz pressure sensor assuming an ocean bottom environment for highly accurate measurements of small and long-term crustal deformation

^○Yuya Machida, Shuhei Nishida, Eiichiro Araki, Toshinori Kimura (JAMSTEC, Kanagawa, Japan)

In the Nankai Trough region, several large interplate earthquakes occurred repeatedly due to a subduction of the Philippine Sea Plate beneath the Eurasian Plate. In this area, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) have deployed cabled observatory system (DONET) and long-term borehole monitoring systems (LTBMS) to monitor earthquakes and tsunamis, and to understand a seismogenic process of large interplate earthquakes. Seafloor pressure measurements are continuously conducted since the installation of the observatories, and are important for the detection of long-term crustal deformations to obtain geophysical knowledge associated with the occurrence of large earthquakes. However, pressure values contain instrumental drifts in the sensors in addition to the pressure changes associated with crustal deformations on the seafloor. Therefore calibrations of the pressure sensor is indispensable. We are developing a mobile pressure gauge to calibrate existing pressure sensor. The gauge has a quartz pressure sensor as a water pressure sensor. A target accuracy of the gauge is less than 1 hPa compared to the absolute pressure value to detect small crustal deformations. Machida et al. (2016) assessed a quartz pressure sensor characteristics assuming an ocean bottom environment in the laboratory. The results showed that several factors, such as a temperature hysteresis and a pressure hysteresis, cause less-accurate water pressure measurements. We conducted further assessments regarding attitude of the sensor. Results showed that the attitudes have an impact on the target accuracy. Based on the assessments, specifications of the gauge has to be designed to achieve the accurate water pressure measurements on the order of 1hPa. It would contribute to obtain long-term small amounts of seafloor displacements related to geophysical phenomena.