A Development of a Mobile Pressure Calibrator for Seafloor Geodetic Measurements

Abstract

Difficulty of measuring vertical crustal deformation on the seafloor at a rate of several cm/year related to geophysical phenomena using a water pressure sensor depends on the inherent drift of the sensor. In order to calibrate the drift components of the pressure sensor, calibrator with high accuracy with 1 hPa or less are necessary. However changes in the ambient environment during a process of transporting the pressure sensor inside the calibrator from a laboratory to the seafloor influence the measurement accuracies. To overcome these problems, we have developed a mobile pressure gauge to calibrate pressure sensor network on a centimeter scale. 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 0.07 hPa or less. It suggests that the controlling of the sensor temperature and applied pressure during the transportation decrease the uncertainties of the measurement accuracy.