日本地球惑星科学連合2014年大会

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インターナショナルセッション(口頭発表)

セッション記号 S (固体地球科学) » S-IT 地球内部科学・地球惑星テクトニクス

[S-IT03_29PM1] Structure and dynamics of Earth and Planetary deep interiors

2014年4月29日(火) 14:15 〜 16:00 418 (4F)

コンビーナ:*田中 聡(海洋研究開発機構 地球内部ダイナミクス領域)、芳野 極(岡山大学地球物質科学研究センター)、亀山 真典(国立大学法人愛媛大学地球深部ダイナミクス研究センター)、趙 大鵬(東北大学大学院理学研究科附属地震・噴火予知研究観測センター)、ヘルンランド ジョン(東京工業大学 地球生命研究所)、座長:田中 聡(海洋研究開発機構 地球内部ダイナミクス領域)、寺崎 英紀(大阪大学大学院理学研究科)

14:45 〜 15:00

[SIT03-17] Rapid lateral variation of P-wave velocity at the base of the mantle beneath the Western Pacific

*田中 聡1川勝 均2大林 政行1NECESSArray プロジェクトチーム 2 (1.JAMSTEC、2.ERI, Univ. Tokyo)

キーワード:P-wave velocity, the base of the mantle, the Western Pacific

We examine P-wave velocity structure at the base of the mantle beneath the Western Pacific, where is the western edge of the Pacific Large-Low Velocity Province (LLVP), by using high-quality seismograms that are provided by the NECESSArray project. Forward modeling with the reflectivity method is conducted to explain the variation of P-wave travel times as function of epicentral distance near the core shadow zone after station and ellipticity corrections are applied. Additionally PcP-P travel times are also examined to enlarge the survey area. As a result, a rapid variation of P-wave velocity structure at the base of the mantle is detected. Thin (10 to 60 km thickness) and very low velocity (-2 to -6 %) layers at the base of the mantle are intersected with a 100 km thickness and high velocity (+3%) layer, and a slightly fast layer exists at the north of the region with the thin and low velocity layers. Their spatial separations are typically several hundred kilometers and it would be difficult to explain by only a thermal effect. These observations suggest that very complicated thermo-chemical reactions occur near the edge of Pacific LLVP.