[S-GD01] Gravity and Geoid

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

*Masaya Kimura¹, Nobuki Kame¹, Shingo Watada¹, Makiko Ohtani², Akito Araya¹, Yuichi Imanishi¹, Masaki Ando³, Takashi Kunugi⁴ (1.Earthquake Research Institute,The University of Tokyo, 2.National Institute of Advanced Industrial Science and Technology, 3.Department of Physics, The University of Tokyo, 4.National Research Institute for Earth Science and Disaster Resilience)

Keywords: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.