Development of the prototype system for the long-term OBP drift elimination using the "A-0-A" approach
Abstract
Ocean bottom pressure gauge (OBP) can continuously observe the vertical crustal deformation on the seafloor. The long-term sensor drift of pressure sensors equipped with OBPs has been a serious and long-standing problem for detection of the slow crustal deformation. One of the approaches to reduce the long-term drift from OBP record is so-called "A-0-A" method. The method uses atmospheric pressure in the housing as the reference pressure (Kajikawa et al., 2014) instead of using the pressure standard, such as a dead-weight tester (Sasagawa and Zumberge, 2013), to monitor the sensor drift. To assess the "A-0-A" approach, we conducted a series of lab-experiments with the pressure standard in Advanced Industrial Science and Technology (AIST). Based on the lab-experiments, we assessed the drift characteristic can be basically removed by the atmospheric pressure as zero-point ("0").
Following the lab-experiments, we developed a prototype of OBP with "A-0-A" function, which can be deployed to deep (~ 6,500 m) sea environment. We adopted a standard 17-inch glass sphere as the pressure housing. In the system, a pressure sensor must be installed in the housing and the water pressure must be applied through a penetrator hole of the glass sphere. A three-way ball-valve is placed in front of the sensor so that the applied pressure can switched between outside (water pressure) and inside (air pressure in the housing). A precise barometer is also installed to measure the internal pressure because the pressure data is used as references to know the drifting nature of the pressure sensor at its "zero-point". To assess the ability of the developed system, we conducted the 4-day sea-trial in Nemuro-Oki, southern Kuril trench. We installed the system on the seafloor of 2,700m depth with free-fall and pop-up recovery system. During the observation, the valve switched to the internal pressure side every two-hour and the position was kept for 20 min. After measuring the internal pressure, the valve moved back to the outside. We successfully obtained the both records of the water pressure and of the internal pressure measured by a single deep-sea water pressure sensor (Paroscientific, 410K-291). In the presentation, we will describe our system more in detail as well as its behavior on the seafloor based on the records obtained by the first sea-trial.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.S33D0615O
- Keywords:
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- 1294 Instruments and techniques;
- GEODESY AND GRAVITY;
- 4594 Instruments and techniques;
- OCEANOGRAPHY: PHYSICAL;
- 7240 Subduction zones;
- SEISMOLOGY;
- 7294 Seismic instruments and networks;
- SEISMOLOGY