日本地球惑星科学連合2018年大会

講演情報

[EE] ポスター発表

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-IT24] Probing the Earth's interior with geophysical observation on seafloor

2018年5月22日(火) 13:45 〜 15:15 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:末次 大輔(海洋研究開発機構 地球深部ダイナミクス研究分野)、Guilhem BARRUOL(CNRS, Institut de Physique du Globe de Paris, France)、川勝 均(東京大学地震研究所、共同)、Douglas Wiens(Washington University in St Louis)

[SIT24-P03] Shear wave splitting observed in the Ontong Java Plateau and adjacent regions

*田中 聡1末次 大輔1塩原 肇2杉岡 裕子3伊藤 亜妃1一瀬 建日2石原 靖4大林 政行1利根川 貴志4吉光 淳子1小林 拓史3 (1.海洋研究開発機構 地球深部ダイナミクス研究分野、2.東京大学 地震研究所、3.神戸大学理学研究科惑星学専攻、4.海洋研究開発機構 地震津波海域観測研究開発センター)

キーワード:マントル異方性、オントンジャワ海台

We measured shear wave splitting of SKS, SKKS, and PKS phases observed at broadband seismic stations on the sea floor and islands in the Ontong Java Plateau (OJP) and adjacent regions. Due to high noise level, we could use only 3 deep earthquakes with magnitudes greater than 7 occurred in the south America. A bandpass filter with cut-off frequencies between 0.02 and 0.2 Hz was applied to the observed seismograms, of which frequency range is a bit lower than the usual for continental areas. By using the eigenvalue method (Silver and Chan, 1991; Helffrich et al., 2000), we tried to estimate the splitting directions and delay times. However, except for three stations, null or node with N-S and E-W directions were obtained or many cases. The directions of the nodes did not coincide with the absolute plate motion of the Pacific plate (WNN-ESE, Argus et al., 2011). The exceptions were observed at the stations located in the southeast margin of the OJP near Stewart Basin and Ellice Basin, which showed that the fast direction was NNW-SSE or N-S and the delay time was 1–2 s. These observations suggest that the directions of mantle flows below the OJP are different from those in the southeastern outside.