Time-dependent ground motion amplification characteristics at reclaimed land after the 1995 Hyogoken Nambu Earthquake

摘要

Two sets of borehole array records obtained fromthe Great Hanshin Earthquake, as well as its fore and after shocks,are investigated. One of the stations is located at Port Island inKobe City, where severe liquefaction occurred mid the recordsfrom the main event include the typical phenomena of liquefaction.The other station is located at Rokko Island in Kobe City, wherethe liquefaction phenomenon was not predominant as it was atPort Island. The non-linear ground motion amplification,depending on the level of input ground motion as well as itsspectral characteristics, is carefully investigated. Two numericaltechniques for seismic response ground analysis are applied forthese stations: one is the frequency-dependent equivalentlinearization technique for frequency domain analysis, and theother is the effective stress-based liquefaction analysis. Thediscussion is focused on the amplification characteristics of thesetwo reclaimed lands, depending on their reclamation history. Thetime-dependent amplification ratio for peak ground motion andspectral contents is demonstrated, caused by the recovery of soilrigidity due to the decrease in excess pore water pressure after themain event.