[S-GD01] 重力・ジオイド

[SGD01-08] Detection of Earthquake-induced Prompt Gravity Signals in Multi-channel Data

*木村 将也¹、亀 伸樹¹、綿田 辰吾¹、大谷 真紀子²、新谷 昌人¹、今西 祐一¹、安東 正樹³、功刀 卓⁴ (1.東京大学地震研究所、2.産業技術総合研究所、3.東京大学大学院理学系研究科物理学専攻、4.防災科学技術研究所)

キーワード：earthquake-induced gravity perturbation、transient deformation、time variable gravity、2011 Tohoku-Oki earthquake

Seismic waves radiating from an earthquake rupture induce density perturbations of the medium, which in turn generate widespread transient gravity perturbations before the arrival of P-waves. Recently, signal detections of such prompt gravity perturbations from the 2011 Tohoku-Oki earthquake were reported. However, the data used for the detections were only a small subset of the available data, and the statistical significance of the signals were not sufficient nor discussed. In this study, we optimized multi-channel data recorded by several instruments and searched for the signals from the 2011 event. Though the single-trace records did not show any signal, the stacked trace of the broadband seismometer array data in Japan showed a signal clearly standing above the noise level, and this detection was confirmed with a sufficient statistical significance. This result provides the first constraint on the amplitude of prompt gravity signals by observation and will work as a reference for future detections.