[S-SS10] Strong Ground Motion and Earthquake Disaster

[SSS10-10] High-dense seismic observation in Seikan Tunnel and Tappisaki

*Seiji Tsuno¹, Masahiro Korenaga¹, Shinji Sato¹, Hiroaki Yamanaka², Nobuo Takai³ (1.Railway Technical Research Institute, 2.Tokyo Institute of Technology, 3.Hokkaido University)

Keywords:High-dense seismic observation, Spatial variation, Topographical effect, Tappisaki

To understand the spatial variation of earthquake ground motions in a long tunnel and the influence of earthquake ground motions due to the topographical effects of stiff sites, a high-dense continuous seismic observation has been carried out in the Seikan Tunnel and Tappisaki. We installed seismometer JEP-6A3-2/JEP-6A3-10 at 7 sites in the Seikan Tunnel near Tappi and EPSON M-A352 at 10 sites in the inclined shaft. In addition, seismometer JEP-6A3-2 have been installed at 13 sites at Tappisaki with elevation range from 2 to 166 m. We started to install seismometers at observation points in November 2023 and finished to install in February 2024. A magnitude (Mj) 5.9 earthquake occurred on November 20, 2023, with its epicenter off the eastern coast of Aomori Prefecture, and the seismic data was recorded at 4 sites in Tappisaki. The PGA of earthquake ground motions at each site with the elevation between 16 and 166 m is in the range of 1.1 to 4.3 cm/s² for the NS component and 1.2 to 2.3 cm/s² for the EW component. Since the epicenter distance of the event is approximately 160 km, the surface geology and topography are inferred these differences in earthquake ground motions. In the presentation, we will provide an overview of the observation and the initial analysis results.