5:15 PM - 7:15 PM
[SCG55-P31] Estimating Vertical Movement During the 2024 Boso Slow Slip from Ocean Bottom Pressure Gauge and an Oceanic Model
Keywords:slow slip event, ocean bottom pressure gauge, Oceanic Model, MSSA
GNSS observations, which began in the late 1990s, have shown that slow slip events (SSEs) have occurred in similar areas on the plate boundary off the Boso Peninsula 6 times between 1996 and 2018. Unlike normal earthquakes, SSEs are a phenomenon in which plate boundaries slip without emitting seismic waves. Many of the SSEs that occur at plate boundaries occur beneath the seafloor. As a method for continuously observing these events, ocean bottom pressure gauges (OBPs) have been used to observe vertical crustal movements. The data obtained from the OBPs include changes in tides, oceanographic variations, seasonal variations on the seafloor, postseismic variations due to large earthquakes, and so on. Various methods have been used to remove changes and variations that are not due to SSEs. In recent years, a method for applying multichannel singular spectrum analysis (MSSA) has been developed (Sato et al., GRL, 2024). Another SSE was observed off the Boso Peninsula in late February to early March 2024, approximately 6 years after the 2018 SSE. This study aims to use MSSA to estimate the vertical movement of the seafloor due to the slip of the 2024 Boso SSE.
The data used were OBP data and oceanic model data developed by Meteorological Research Institute. We applied MSSA to the tide-corrected and detrended OBP data and the detrended oceanic model data. MSSA is a method for decomposing multiple channels into similar components. Next, the correlation between the OBP data and the oceanic model data was calculated for each component, and the oceanic model was reconstructed using only those with good correlations. This means that only those components from the oceanic model data that reproduce the observed data well are extracted, compensating for the imperfections of the oceanic model. By subtracting the reconstructed ocean model data from the OBP data, oceanic variation can be better removed. Then, by fitting a parametric function representing seasonal variation of the seafloor and SSE-induced variation to the data from which oceanic variation was removed, variation due to SSE was extracted.
The analysis showed that there was a slight uplift at the observation point thought to be the center of the SSE slip, while there were almost no changes at the surrounding observation points. This suggests that the changes were smaller than the previous Boso SSE in 2018, and that the scale of the 2024 Boso SSE was relatively small.
Acknowledgment
We thank the captains and crews for R/V Shinsei-maru of JAMSTEC, R/V Shinyo-maru of Tokyo University of Marine Science and Technology, Kaiyo-maru No. 2 of Kaiyo Engineering Co. for their support. This work was supported by the Earthquake and Volcano Hazards Observation and Research Program authorized by the Ministry of Education, Culture, Sports, Science and Technology. This work was also supported by the Japan Society for the Promotion of Science (25287109, 23K03541).
The data used were OBP data and oceanic model data developed by Meteorological Research Institute. We applied MSSA to the tide-corrected and detrended OBP data and the detrended oceanic model data. MSSA is a method for decomposing multiple channels into similar components. Next, the correlation between the OBP data and the oceanic model data was calculated for each component, and the oceanic model was reconstructed using only those with good correlations. This means that only those components from the oceanic model data that reproduce the observed data well are extracted, compensating for the imperfections of the oceanic model. By subtracting the reconstructed ocean model data from the OBP data, oceanic variation can be better removed. Then, by fitting a parametric function representing seasonal variation of the seafloor and SSE-induced variation to the data from which oceanic variation was removed, variation due to SSE was extracted.
The analysis showed that there was a slight uplift at the observation point thought to be the center of the SSE slip, while there were almost no changes at the surrounding observation points. This suggests that the changes were smaller than the previous Boso SSE in 2018, and that the scale of the 2024 Boso SSE was relatively small.
Acknowledgment
We thank the captains and crews for R/V Shinsei-maru of JAMSTEC, R/V Shinyo-maru of Tokyo University of Marine Science and Technology, Kaiyo-maru No. 2 of Kaiyo Engineering Co. for their support. This work was supported by the Earthquake and Volcano Hazards Observation and Research Program authorized by the Ministry of Education, Culture, Sports, Science and Technology. This work was also supported by the Japan Society for the Promotion of Science (25287109, 23K03541).