Mobile Pressure Calibrator for the Development of Submarine Geodetic Monitoring Systems

Abstract

AbstractMonitoring long‐term vertical seafloor displacements at the centimeter scale using a pressure gauge network in the seismogenic zone is key to understanding the real‐time strength of interplate coupling. The mobile pressure calibrator (MPC) was developed for calibrating a seafloor pressure gauge network with a resolution of less than 1 hPa/year, equivalent to about 1 cm/year. Inherent drift of the seafloor pressure gauges is estimated by comparing the raw observations between the seafloor pressure gauges and the MPC and subsequently subtracting the long‐term pressure data. In October 2018, three in situ pressure measurements were conducted to evaluate the measurement uncertainty of the MPC. The calibrator was placed adjacent to a seafloor pressure gauge, which is installed at a depth of about 1,750 m in the Nankai Trough offshore Japan, and measured the pressure differences between the calibrator and the seafloor pressure gauge. The drift component of the pressure gauge used inside the MPC was estimated and corrected based on calibrations performed in the laboratory before and after the in situ seafloor pressure measurements. The results indicated an uncertainty of 0.04 hPa for the in situ measurements and therefore the possibility of detecting small, long‐term seafloor displacements. We continue to compare the MPC and seafloor pressure gauge deviations over intervals of several months to years and estimate the drift of the seafloor pressure gauge.