5:15 PM - 6:45 PM
[SCG48-P11] Magnetic anomalies in the Japan Sea: Seafloor spreading in the Japan Sea
Keywords:Japan Sea, magnetic anomalies, back-arc basin
We will present the latest magnetic anomaly map of the Japan Sea to reveal tectonic history of the Japan Sea. Previous works indicated that the Japan Sea started to open around ca 25 Ma with seafloor spreading (e.g., Tamaki et al., 1992). Several works showed the existence of magnetic anomaly lineations. Isezaki and Uyeda (1973) pointed out the existence of magnetic anomaly lineations in the Japan Basin, northeast part of the Japan Sea. Isezaki (1986) showed magnetic anomaly lineations in the southern half of the Japan Basin. Tamaki and Kobayashi (1988) also found the magnetic anomaly lineations in the Japan Basin. They proposed the seafloor spreading with ridge propagations. Kato et al. (2005) confirmed the magnetic anomaly lineations using deep-tow magnetic survey. However, the distribution of the magnetic anomaly lineations is obscured in the whole Japan Basin. To expose the whole picture of the magnetic anomalies of the Japan Sea is essential for a comprehensive grasp of the tectonic history of the Japan Sea.
We compiled all the available geomagnetic data to make a new magnetic anomaly map of the Japan Sea. The geomagnetic data incorporated in this study were derived from cruises of R/Vs Hakuho-maru and Tansei-maru of Ocean Research Institute, the University of Tokyo, those of R/V Hakurei-maru No. 2 of Geological Survey of Japan from (Ishihara, 2020), and those of R/Vs, Professor Bogorov and Professor Gagarinsky (e.g., Karp et al., 1996). We also used the data from the databases of National Oceanic and Atmospheric Administration/National Centers for Environmental Information and Japan Oceanographic Data Center. Since the cruises span more than four decades and the total magnetic field data were originally reduced to anomalies using different reference magnetic fields in most of the original data files, we recalculated magnetic anomalies using Comprehensive Model Phase 4 (Sabaka et al., 2004) and the 13th generation of the International Geomagnetic Reference Field (Alken et al., 2021). The magnetic anomalies were levelled to reduce crossover differences by the method proposed by Ishihara (2015).
Our map shows mostly linear magnetic anomalies around the Japan Basin. The linear magnetic anomalies support the hypothesis of formation of the Japan Sea proposed by Tamaki et al. (1992). No clearly linear magnetic anomalies are not recognized around the areas where the recent refraction surveys indicate an existence of an oceanic crust (e.g., Sato et al., 2018).
We compiled all the available geomagnetic data to make a new magnetic anomaly map of the Japan Sea. The geomagnetic data incorporated in this study were derived from cruises of R/Vs Hakuho-maru and Tansei-maru of Ocean Research Institute, the University of Tokyo, those of R/V Hakurei-maru No. 2 of Geological Survey of Japan from (Ishihara, 2020), and those of R/Vs, Professor Bogorov and Professor Gagarinsky (e.g., Karp et al., 1996). We also used the data from the databases of National Oceanic and Atmospheric Administration/National Centers for Environmental Information and Japan Oceanographic Data Center. Since the cruises span more than four decades and the total magnetic field data were originally reduced to anomalies using different reference magnetic fields in most of the original data files, we recalculated magnetic anomalies using Comprehensive Model Phase 4 (Sabaka et al., 2004) and the 13th generation of the International Geomagnetic Reference Field (Alken et al., 2021). The magnetic anomalies were levelled to reduce crossover differences by the method proposed by Ishihara (2015).
Our map shows mostly linear magnetic anomalies around the Japan Basin. The linear magnetic anomalies support the hypothesis of formation of the Japan Sea proposed by Tamaki et al. (1992). No clearly linear magnetic anomalies are not recognized around the areas where the recent refraction surveys indicate an existence of an oceanic crust (e.g., Sato et al., 2018).