日本地球惑星科学連合2018年大会

講演情報

[JJ] ポスター発表

セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG67] 海底下の変動現象を捉えるための海域観測の現状と展望

2018年5月24日(木) 10:45 〜 12:15 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:平原 和朗(京都大学大学院理学研究科地球惑星科学専攻地球物理学教室)、日野 亮太(東北大学大学院理学研究科)、堀 高峰(独立行政法人海洋研究開発機構・地震津波海域観測研究開発センター)

[SCG67-P09] Mobile pressure calibrator for ocean bottom pressure gauge of the DONET, Part1: Development of the pressure measurement unit

*町田 祐弥1西田 周平1荒木 英一郎1 (1.海洋研究開発機構)

キーワード:Mobile pressure calibrator、crustal deformation、pressure sensor、seismogenic zone、Nankai trough

We have developed a mobile calibration device for an ocean bottom pressure gauge. Since vertical seafloor displacements result in changes in water pressure, precise pressure measurement on the seafloor has been a key to understand geophysical phenomena such as occurrence of large interplate earthquakes. A simulation of earthquake cycles in the Tonankai distinct, Japan, showed long-term uplift at a rate of about 1 hPa/year (i.e., = 1cm seawater height/year) as a result of pre-seismic slip immediately above the rupture area at depth ~2000 m. However a pressure sensor has inherent instrumental drift at a maximum rate of 10 hPa/year. Therefore we need to calibrate each pressure sensor absolutely on the seafloor to detect crustal deformations. The mobile pressure calibrator is composed of a pressure measurement unit and a level adjusting unit. The pressure measurement unit has quartz pressure sensors (Paroscientific Inc. 410K). We laboratory evaluated dependencies of temperature and pressure condition of quartz pressure gauge assuming a transport condition between laboratory and seafloor. Based on the results, we have developed the pressure measurement unit with high accuracy on the seafloor condition. In order to adjust a level with the ocean bottom pressure gauge, the pressure measurement unit is combined with the level adjusting unit whose adjustment accuracy is 1 mm. The system enables us to calibrate the ocean bottom pressure gauge at accuracy of less than 1 hPa. We have plan to calibrate the DONET pressure sensors over 5 years. In March, 2018, a first calibration of the DONET pressure sensor is performed. In the presentation, we show initial results of the calibrations, and discuss about the possibility to detect crustal deformation in the Nankai trough seismogenic zone.