[S-IT39_2AM2] 地球深部ダイナミクス：プレート・マントル・核の相互作用

[SIT39-08] 西太平洋下のD”領域内部の３次元S波速度構造

小西 健介¹、河合 研志²、*ゲラー ロバート³、冨士 延章⁴ (1.ソウル大学校、2.東京工業大学大学院理工学研究科地球惑星科学専攻、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：波形インバージョン, 西太平洋, マントル対流, 最下部マントル, プルームクラスター

We infer 3-D localized shear velocity structure in the lowermost 400 km of the mantle at the western edge of the Pacific large low shear velocity province (LLSVP) by applying waveform inversion to transverse component body-wave waveforms from the F-net seismic array in Japan. Our dataset consists of relatively long period (12.5-200 s) broad-band seismic waveforms of Tonga-Fiji deep focus and intermediate deep earthquakes. We conduct several tests to confirm the robustness of the inversion results. We find two low velocity zones at the bottom of the target region, with a high velocity zone in the middle, and a low velocity zone above the high velocity zone and contiguous with the two deeper low velocity zones at a depth of 200-300 km above the CMB. This supports the idea that the Pacific LLSVP may be an aggregation of small upwelling plumes rather than a single large thermochemical pile.