5:15 PM - 6:30 PM
[SSS07-P05] Velocity structure of the uppermost mantle beneath central Japan
Keywords:velocity structure of upper most mantle, volcanic front, Chubu district, Japan
In the central Japan area, complicated tectonic structure is recognized due to the interaction between the Pacific plate and the Philippine Sea plate. The volcanic front bends sharply in this area. There are many volcanoes with wide distribution such as Mt. Asama, those in northern Nagano Prefecture, and Hida mountain range. We estimated velocity structure of the uppermost mantle beneath this area with the tomography method. We used a method by Katsumata (2010), in which velocity structure was estimated from shallower parts to the deeper including depth distributions of discontinuities sequentially.
We describe the low velocity areas seen in the result of the tomographic analysis. Low velocity area is recognized beneath Niijima island. The low velocity area is distributed beneath the Philippine Sea plate rather than extending toward the Pacific Plate. In northeastern Japan, characteristic low velocity areas are recognized beneath the volcanic front which is considered to be related to the Pacific plate subduction. It is natural that the low velocity area beneath Izu Islands extends toward the Pacific plate. However, the appearance of the low velocity area is different from the expectation. Beneath the Izu Peninsula, the low velocity area seems to connect to the low velocity area beneath the western area of Shizuoka Prefecture down to about 100 km. It is similar to the low velocity area beneath Mt. Fuji (Figure). We recognize a large low velocity area beneath Yamanashi Prefecture at depth of about 100 km. Low velocity area is recognized beneath Mt. Yakedake above the Philippine Sea plate. Whereas it seems that low velocity area beneath Mt. Nasu extends toward the Pacific plate, low velocity areas beneath Mt. Myoko and Mt. Tateyama seems to extend downward to the west.
These low velocity distributions are just appearance seen in the result of a tomographic analysis, and interpretation on them are an unresolved problem.
Acknowledgements: We used the data provided by the Japan Meteorological Agency with the cooperation of the Ministry of Education, Culture, Sports, Science and Technology of Japan based on data from NIED, Hokkaido University, Hirosaki University, Tohoku University, The University of Tokyo, Nagoya University, Kyoto University, Kochi University, Kyushu University, Kagoshima University, the National Institute of Advanced Industrial Science and Technology, the Geospatial Information Authority of Japan, the Japan Agency for Marine-Earth Science and Technology, the Association for the Development of Earthquake Prediction, the Incorporated Research Institutes for Seismology, the Japan Meteorological Agency, and the governments of Aomori Prefecture, the Tokyo Metropolitan Government, Shizuoka Prefecture, and Kanagawa Prefecture.
We describe the low velocity areas seen in the result of the tomographic analysis. Low velocity area is recognized beneath Niijima island. The low velocity area is distributed beneath the Philippine Sea plate rather than extending toward the Pacific Plate. In northeastern Japan, characteristic low velocity areas are recognized beneath the volcanic front which is considered to be related to the Pacific plate subduction. It is natural that the low velocity area beneath Izu Islands extends toward the Pacific plate. However, the appearance of the low velocity area is different from the expectation. Beneath the Izu Peninsula, the low velocity area seems to connect to the low velocity area beneath the western area of Shizuoka Prefecture down to about 100 km. It is similar to the low velocity area beneath Mt. Fuji (Figure). We recognize a large low velocity area beneath Yamanashi Prefecture at depth of about 100 km. Low velocity area is recognized beneath Mt. Yakedake above the Philippine Sea plate. Whereas it seems that low velocity area beneath Mt. Nasu extends toward the Pacific plate, low velocity areas beneath Mt. Myoko and Mt. Tateyama seems to extend downward to the west.
These low velocity distributions are just appearance seen in the result of a tomographic analysis, and interpretation on them are an unresolved problem.
Acknowledgements: We used the data provided by the Japan Meteorological Agency with the cooperation of the Ministry of Education, Culture, Sports, Science and Technology of Japan based on data from NIED, Hokkaido University, Hirosaki University, Tohoku University, The University of Tokyo, Nagoya University, Kyoto University, Kochi University, Kyushu University, Kagoshima University, the National Institute of Advanced Industrial Science and Technology, the Geospatial Information Authority of Japan, the Japan Agency for Marine-Earth Science and Technology, the Association for the Development of Earthquake Prediction, the Incorporated Research Institutes for Seismology, the Japan Meteorological Agency, and the governments of Aomori Prefecture, the Tokyo Metropolitan Government, Shizuoka Prefecture, and Kanagawa Prefecture.