5:15 PM - 7:15 PM
[SCG55-P33] Assessment of long-term drift removal performance using the A-0-A approach based on the laboratory experiment
Keywords:Ocean Bottom Pressure gauges, A-0-A, Instrument drift, crustal deformation on the sea floor
Ocean bottom pressure gauges (hereafter, OBPs) can continuously monitor vertical crustal deformation on the sea floor. However, OBP data are affected by instrument drift, which hinders the detection of slow crustal deformations. Instrument drift can be classified into pressure-dependent drift (“span drift”) and pressure-independent drift (“zero-point drift”). For high-precision ocean bottom pressure observations, sensors employing Bourdon tubes manufactured by Paroscientific are commonly used. In these sensors, zero-point drift constitutes the majority of the instrument drift. In other words, if the zero-point drift can be accurately determined, it is expected that the drift under applied pressure can be efficiently removed (Kajikawa and Kobata, 2019). This method is referred to as the A-0-A (Ambient–Zero–Ambient) approach and efforts are underway to incorporate this mechanism into actual seafloor observations to eliminate the instrument efficient drift in OBPs (e.g., Wilcock et al., 2021; Aline Peltier et al., 2022).
However, there are few cases in which the assumption—that zero-point drift comprises the majority of the instrument drift has been validated by long-term laboratory experiments spanning several years. Therefore, in this study, calibration tests of the pressure gauges were conducted under controlled laboratory conditions using the A-0-A approach to evaluate its drift removal performance. In addition, laboratory calibration tests were alternated with observations in the actual sea trial, and a comparison of the drift behavior in the laboratory and at sea was performed.
In this study, four OBPs utilizing Paroscientific’s Bourdon tubes were tested. The laboratory calibration experiments used a pressure standard at the National Institute of Advanced Industrial Science and Technology. The data employed for the analysis spanned from July 2020 to June 2024, with seafloor measurements interspersed during this period. The A-0-A calibration experiments obtained drift components at applied and zero-point (atmospheric) pressures. The results showed that, for all OBPs, the time series of the applied pressure drift and the zero-point drift were similar, indicating that instrument drift can be effectively removed using the A-0-A approach.
Subsequently, the residuals of the obtained drift components were calculated. As a result, while two of the OBPs exhibited no significant drift components in the residual time series, the other two OBPs displayed discernible drift components, with the drift amount reaching up to 15 hPa over four years (equivalent to a vertical crustal deformation of 15 cm). This suggests that, for these OBPs, span drift is non-negligible, thereby underscoring the necessity of pre-selecting instruments with minimal span drift when applying the A-0-A approach. A similar tendency was observed when comparing laboratory and seafloor drift: OBPs presumed to have significant span drift did not exhibit consistent drift patterns between the laboratory and seafloor measurements. This discrepancy may be attributed to differences between the applied pressure in the laboratory and the installation pressure on the seafloor environment.
However, there are few cases in which the assumption—that zero-point drift comprises the majority of the instrument drift has been validated by long-term laboratory experiments spanning several years. Therefore, in this study, calibration tests of the pressure gauges were conducted under controlled laboratory conditions using the A-0-A approach to evaluate its drift removal performance. In addition, laboratory calibration tests were alternated with observations in the actual sea trial, and a comparison of the drift behavior in the laboratory and at sea was performed.
In this study, four OBPs utilizing Paroscientific’s Bourdon tubes were tested. The laboratory calibration experiments used a pressure standard at the National Institute of Advanced Industrial Science and Technology. The data employed for the analysis spanned from July 2020 to June 2024, with seafloor measurements interspersed during this period. The A-0-A calibration experiments obtained drift components at applied and zero-point (atmospheric) pressures. The results showed that, for all OBPs, the time series of the applied pressure drift and the zero-point drift were similar, indicating that instrument drift can be effectively removed using the A-0-A approach.
Subsequently, the residuals of the obtained drift components were calculated. As a result, while two of the OBPs exhibited no significant drift components in the residual time series, the other two OBPs displayed discernible drift components, with the drift amount reaching up to 15 hPa over four years (equivalent to a vertical crustal deformation of 15 cm). This suggests that, for these OBPs, span drift is non-negligible, thereby underscoring the necessity of pre-selecting instruments with minimal span drift when applying the A-0-A approach. A similar tendency was observed when comparing laboratory and seafloor drift: OBPs presumed to have significant span drift did not exhibit consistent drift patterns between the laboratory and seafloor measurements. This discrepancy may be attributed to differences between the applied pressure in the laboratory and the installation pressure on the seafloor environment.