1:45 PM - 3:15 PM
[SEM14-P04] Investigation of extraction method of high-quality electromagnetic data for marine MT survey
Keywords:subduction zone, magnetotelluric method, resistivity
Recently, the amount of observed electromagnetic data is increased due to the lengthening of observation periods and the larger observation density resulting from the development of observation equipment. In general, more analytical data will stabilize analytical errors, but at a higher analytical cost. Also "Remote reference" and "Robust stacking" are other methods for removing noise from observed data. Remote reference repels noise specific to the observation site by prioritizing signals common to the two sites, while Robust stacking statistically eliminates outliers and anomalies in the data. However, these methods alone cannot perfectly eliminate noise, and it is necessary to select data that should be used for analysis.
In this study, we investigated a method to obtain high-quality results by selecting data with low noise levels using seafloor electromagnetic field data acquired in the Nankai Trough Kumano-nada in 2020-2021. In the Nankai Trough, where the Philippine Sea Plate meets the Eurasian Plate, huge earthquakes occur every 100 to 200 years. Observations recorded electromagnetic field fluctuations on the seafloor with the aim of elucidating detailed earthquake generation mechanisms. Here we focus on the dehydration embrittlement theory, which is one of the models for the mechanism of earthquake generation. The model suggests that subduction of the oceanic plate causes dehydration and decomposition of the hydrous minerals in the slab, and the resulting water triggers earthquakes.
By applying the magnetotelluric (MT) method to estimate the resistivity structure, we can infer the water distribution in the area of a large earthquake. As a result of the study in this research, automatic selection of good quality data was possible, and high-quality MT response functions were obtained that can be used for future structural analysis.
In this study, we investigated a method to obtain high-quality results by selecting data with low noise levels using seafloor electromagnetic field data acquired in the Nankai Trough Kumano-nada in 2020-2021. In the Nankai Trough, where the Philippine Sea Plate meets the Eurasian Plate, huge earthquakes occur every 100 to 200 years. Observations recorded electromagnetic field fluctuations on the seafloor with the aim of elucidating detailed earthquake generation mechanisms. Here we focus on the dehydration embrittlement theory, which is one of the models for the mechanism of earthquake generation. The model suggests that subduction of the oceanic plate causes dehydration and decomposition of the hydrous minerals in the slab, and the resulting water triggers earthquakes.
By applying the magnetotelluric (MT) method to estimate the resistivity structure, we can infer the water distribution in the area of a large earthquake. As a result of the study in this research, automatic selection of good quality data was possible, and high-quality MT response functions were obtained that can be used for future structural analysis.