[S-CG44] Science of slow-to-fast earthquakes

[SCG44-14] Nine-component seismic observation at AIST Iitaka observatory

*矢部 優¹、今西 和俊¹、椎名 高裕¹、千住 朱美² (1.産業技術総合研究所、2.株式会社オーシャンウィングス)

キーワード：回転、歪

Seismic events generate seismic waves. They include not only three-component translational motions, but also six-component strain and three-component rotation. Although rotation was difficult to observe, recent instrumental advances reduce noise level of rotation sensor, which is now being useful in field observations. We conducted a campaign observation of rotational motion using blueSeis-3A sensor developed by iXblue along with Trillium compact sensor observing translational motions. We put these sensors at Iitaka observatory of Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (GSJ, AIST), which is located at Kii Peninsula, southwest Japan. The campaign observation was conducted from 22^nd November, 2021 to 28^th January, 2022. At this observatory, GSJ constructed a strain observation station using Gradwin Tensor Strainmeters (GTSMs). GTSMs measure three-component horizontal strain. Therefore, nine-component seismic records were monitored during the campaign observations. We investigated noise levels of strain and rotation sensors to evaluate usefulness of these sensors in the purpose of seismic wave analysis. During the observation period, a moderate earthquake with moment magnitude 5.1 occurred on 3^rd December, 2021 beneath the Kii channel at 17 km depth (according to F-net catalog). Seismic waves excited by this event were successfully recorded by three sensors. We calculate synthetic waveforms and compare them with observed waveforms to demonstrate that strain and rotation seismograms are useful to constrain seismic source properties of earthquakes.