日本地球惑星科学連合2018年大会

講演情報

[EE] Evening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-IT28] The lithosphere and the asthenosphere

2018年5月22日(火) 17:15 〜 18:30 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:Catherine Rychert(University of Southampton)、川勝 均(東京大学地震研究所)、Samer Naif(共同)、Jessica M Warren (University of Delaware)

[SIT28-P03] VTI mantle structure under the northeast Pacific ocean

*丸山 純平1川勝 均1竹内 希1 (1.東京大学地震研究所)

キーワード:鉛直軸対称異方性、リソスフェア−アセノスフェア系、北西太平洋

The existence of seismic anisotropy in the lithosphere-asthenosphere system (LAS) has been well established. Especially, strong radial anisotropy (transverse isotropy with vertical symmetric axis, VTI) under the Pacific ocean have been observed (Nettles and Dziewonski, 2008) and it is important to understand the formation and evolution process of the LAS. In order to describe the VTI of earth’s interior, 5 elastic parameters are needed. Kawakatsu et al. (2015) suggest a new representation of the parameters, αH, αV, βH, βV, ηκ, based on the elliptic condition of slowness. In this representation, αH, αV, βH, βV mean velocity of P or S wave which oscillate in horizontal or vertical plane and ηκ has change of incident angle dependence of P-SV wave velocities. In this study, we investigate the relationship between VTI parameters and traveltime of surface wave and various body waves and estimate an 1-D VTI mantle structure under the Pacific ocean using seismic waveform data. The events occurred near Japan and observed at the pacific islands, Hawaii, Midway, and broad-band ocean bottom seismometers (BBOBSs) on the northwest pacific seafloor. Because the effect of ηκ on a body wave traveltime depends on a incident angle in the LAS, a distance dependence of direct body wave traveltime is affected by ηκ and the traveltime of vertically propagating wave such as ScS is independent on ηκ. Then the 1-D structure of a corridor which has observation points and seismic source on the same line will be estimated in detail.