09:00 〜 09:15
[SSS13-01] 海洋島の広帯域地震計を用いた海洋外部重力波のモニタリング
キーワード：海洋重力波、広帯域地震計、脈動
Ocen infragravity (IG) waves are surface ocean waves typically below 40m Hz. Past studies reported coastal loadings by the IG waves cause significant background noise at island broadband stations. Our previous study developed a technique for reconstructing a tsunami from island broadband seismic data (Nishida et al., 2019), which can be extended for background ocean infragravity waves because they are the physically same phenomenon. The method models the ground deformation due to the IG wavefield at the center of a conical island. We can infer the virtual IG wavefield without the conical island by fitting the modeled displacement to observed seismic data.
IG waves are also crucial for understanding the excitation of background seismic wavefield: primary microseisms and seismic hum. The purpose of this study is to monitor IG waves in order to understand the excitation mechanism at a volcano island, Aogashima. We analyzed three components of seismic data from 2 to 5 mHz at the F-net station and inferred the virtual IG height and the propagation directions as a function of time from 2014 to 2015. The observations are consistent with the array observation of the temporal array of ocean pressure gauges near Aogashima (Tonegawa et al. 2018). The result also shows abrupt changes in the propagation direction associated with typhoons. This method enables us to monitor the azimuthal changes of IG waves by the single station analysis. We plan to use long-term data at Aogashima to track typhoons in the future.
IG waves are also crucial for understanding the excitation of background seismic wavefield: primary microseisms and seismic hum. The purpose of this study is to monitor IG waves in order to understand the excitation mechanism at a volcano island, Aogashima. We analyzed three components of seismic data from 2 to 5 mHz at the F-net station and inferred the virtual IG height and the propagation directions as a function of time from 2014 to 2015. The observations are consistent with the array observation of the temporal array of ocean pressure gauges near Aogashima (Tonegawa et al. 2018). The result also shows abrupt changes in the propagation direction associated with typhoons. This method enables us to monitor the azimuthal changes of IG waves by the single station analysis. We plan to use long-term data at Aogashima to track typhoons in the future.