ABSTRACT
The Horonobe Underground Research Laboratory (URL) is assumed to be located in an aseismic region and earthquakes are rarely occur. An earthquake with a moment magnitude of 4 occurred in at 5:28 (JST) in early morning of June 20, 2018. The strong motions induced by this earthquake were recorded by the accelerometers installed in the URL as well as the Kik-Net and K-Net strong motions networks operated by the National Research Institute for Earth Science and Disaster Prevention of Japan (NIED). The authors explain the results of analyses carried out on the ground amplification and frequency characteristics of the acceleration records at the URL and those of the Kik-net strong motion station and the structural effect of the URL on the ground amplification and frequency characteristics. Furthermore, the implications of the results obtained from this study in practice and the safety of the nuclear waste disposal at depth are discussed.
