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

[SIT03-18] 局所的３次元詳細構造のための波形インバージョン手法の開発およびその応用

*河合 研志¹、小西 健介²、ゲラー ロバート³、冨士 延章⁴ (1.東京工業大学大学院理工学研究科地球惑星科学専攻、2.ソウル大学、3.東京大学大学院理学系研究科地球惑星科学専攻、4.パリ地球物理研究所)

キーワード：最下部マントル, 波形インバージョン法, ファラロンプレート

We formulate the inverse problem of waveform inversion for localized 3-D seismic structure, computing partial derivatives of waveforms with respect to the elastic moduli at arbitrary points in space for anisotropic and anelastic media. In this study we minimize computational requirements by using the Born approximation with respect to a laterally homogeneous model, but this is not an inherent limitation of our approach. We solve the inverse problem using the conjugate gradient (CG) method, using Akaike's Information Criterion (AIC) to truncate the CG expansion. We apply our method to invert for three-dimensional shear wave structure in the lowermost mantle beneath Central America using a total of 2154 waveforms at periods from 12.5 to 200 s recorded at stations near the Pacific coast of North America for 29 deep and intermediate-depth events beneath South America. The resulting model shows lateral heterogeneity in the E-W direction which may be associated with a subducted cold slab surrounded by hotter materials with slower velocities. Various tests show that our model is robust.