[H-CG22] Monitoring the Comprehensive Nuclear-Test-Ban Treaty: Status, operations, and scientific application

[HCG22-P01] Recent progress on sustainable pressure observation at the seafloor

*Hiroyuki Matsumoto¹, Eiichiro Araki¹, Shuhei Nishida¹, Yuya Machida¹, Shuhei Tsuji¹, Keisuke Ariyoshi¹ (1.Japan Agency for Marine-Earth Science and Technology)

The Japan Agency for Marine-Earth Science and Technology (JAMSTEC) is involved in understanding of recurrence process of megathrust earthquakes to monitor seafloor crustal deformation or slow-slip events (SSEs) by using the DONET seafloor network and the long-term borehole monitoring system (LTBMS) deployed in the Nankai Trough. An ocean-bottom pressure recorder (OPBR) has been installed and connected to the DONET in December 2024. The in-situ pressure observation has been started at 2F-S2 station where three interferometry-based fiber optic strainmeters are in operation. The pressure gauge used in the OBPR is based on a quartz resonant pressure transducer (Paroscientific Inc., 8CB7000-I-005) in which both temperature and pressure are calculated and acquired. Consequently, the continuous pressure dataset has been obtained since 03 December 2024. The Bayesian tidal analysis program BAYTAP-G (Tamura et al., 1991) was applied to the pressure recordings to discriminate between the tide component and the sensor drift. A fitted curve for combining with exponential and linear functions for the sensor drift suggests that the linear component (i.e., the sensor drift) is about 0.2 mm (i.e., 2 Pa) per day for the entire period, whereas its rate is 17 Pa per day for the initial 20 days. Before the OBPR deployment at the seafloor, the long-term stability of the present pressure gauge was examined by applying a precise pressure from a pressure balance in the laboratory. The continuous pressurization has shown that the sensor drift yields 10 Pa per day after 20-day pressurization (Matsumoto et al., 2019), which is comparable to the in-situ observation. This pressurization experiment has allowed us to confirm the sensor drift of the OBPR. Additionally, screening of the better sensors can contribute to the more sustainable in-situ observation.