Nonlinear ground motion amplification at reclaimed borehole stations

Two sets of borehole array records obtained from the Great Hanshin Earthquake as well as its fore and after-shocks, are investigated One of the stations is located in Port Island in Kobe City where the severe liquefaction occurred and the records from the main event include the typical phenomena of liquefaction. The other station is located in Rokko Island in Robe City where the liquefaction phenomena was not predominant as it was in Port Island. The nonlinear ground motion amplification, depending on the level of input ground motion as well as their spectral characteristic, are carefully investigated The discussion is focused on the amplification characteristic of these two reclaimed lands depending on their reclamation history. Time-dependent amplification ratio is demonstrated which is caused by the recovery of soil rigidity after the main event.