A mobile pressure gauge for calibrating pressure sensors on the seafloor with a resolution less than 1 hPa
Abstract
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 with accuracy of 1 hPa or less on the seafloor using a high accurate pressure gauge. Machida et al. (2018) evaluated dependencies of temperature and pressure condition of a quartz pressure sensor assuming a transport condition between laboratory and seafloor. They suggested that the careful assessment of the pressure sensor dependencies before assembling the gauge and the controlling of the sensor temperature and applied pressure during the transportation decrease the uncertainties of the measurement accuracy. We have developed a mobile pressure gauge based on their suggestion. Quartz pressure sensors incorporated in the gauge are controlled so that the temperature and applied pressure are constant within a certain range to enhance the measurement accuracies. The laboratory performance tests of the pressure gauge assuming an in situ seafloor measurement at 2000m depth corresponding to a seismogenic zone in the Nankai trough showed that: 1) the pressure sensor temperature was controlled with a change of 0.1 degC or less: 2) the applied pressure was controlled with a change of 200 hPa or less. Considering these results, the uncertainties of pressure sensor accuracies by a temperature characteristic and a pressure hysteresis are 0.01 hPa.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T44C..07M
- Keywords:
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- 1209 Tectonic deformation;
- GEODESY AND GRAVITYDE: 3050 Ocean observatories and experiments;
- MARINE GEOLOGY AND GEOPHYSICSDE: 8170 Subduction zone processes;
- TECTONOPHYSICSDE: 8194 Instruments and techniques;
- TECTONOPHYSICS