Crustal structure beneath Aso Caldera, Southwest Japan, as derived from receiver function analysis

Yuki Abe, Takahiro Ohkura, Takuo Shibutani, Kazuro Hirahara, Mamoru Kato

doi:10.1016/j.jvolgeores.2010.05.011

Abstract Aso Volcano experienced a huge pyroclastic eruption 90 thousand years ago, and formed a large caldera (18 km × 25 km). In order to test the hypothesis of a magma body in the mid and lower crust that has been suggested geophysically and geochemically, we investigated seismic velocity discontinuities and velocity structure beneath Aso Caldera using receiver functions and a genetic algorithm inversion. We confirm the existence of the Moho at depths between 30 km and 35 km and a large velocity anomaly should exist in the deep portion of the crust beneath Aso Caldera, from imaging of receiver functions observed only at stations outside the caldera. As a result of a more detailed examination with GA inversion, a low velocity layer is detected at depths between 10 km and 24 km beneath the western part of the caldera. S-wave velocity of the layer is estimated to be 2.0–2.4 km/s. We estimate that the low velocity layer contains at most 15% melt or 30% aqueous fluid. The layer exists near the Conrad and at the same depths as the swarm of the low frequency earthquakes and a compressional and dilatational deformation source which are expected to be caused by fluid movement beneath the middle-eastern part of the caldera. Fluid contained in the layer might be related with huge pyroclastic eruptions of Aso Volcano.

Crustal structure beneath Aso Caldera, Southwest Japan, as derived from receiver function analysis

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Crustal structure beneath Aso Caldera, Southwest Japan, as derived from receiver function analysis

書誌事項

この論文をさがす

説明

収録刊行物

被引用文献 (13)*注記

参考文献 (36)*注記

関連プロジェクト

詳細情報 詳細情報について

書き出し

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