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Simulation of strong motions in Fukuoka City during the 2005 West Off Fukuoka Prefecture Earthquake with special reference to thick Quaternary sediments around the Kego fault

Earth, Planets and Space200658:BF03351922

  • Received: 8 August 2005
  • Accepted: 7 December 2005
  • Published:


We simulate velocity records at two stations in the building damaged area near the Kego fault in Fukuoka City by 1-D wave propagation theory during the 2005 West Off Fukuoka Prefecture Earthquake, Japan. Here we use the pre-Tertiary bedrock wave deconvolved from the record observed at a K-NET station outside of the damaged area. The observed velocity waveforms and pseudo velocity response spectra in the period range from 0.7 to 10 seconds in the predominant direction (N20°E) components are reasonably reproduced. Velocity pulses with a period of about 1 to 2 seconds in observed velocity waveforms at two stations are found to be amplified by the Quaternary sediments above the pre-Tertiary bedrock. After we confirmed the validity of our approach through the simulation, we predict the peak ground velocity (PGV) distribution around the Kego fault by considering 1-D response of Quaternary sediments at each site. The predicted PGV distribution of N20?E components is largest (about 80 cm/s) in the northeast side of the Kego fault and agrees well with the building damage distribution. Our result shows that the 1-D site responses of Quaternary sediments mainly contributed to the difference of PGVs inside and outside of the damaged area in Fukuoka City.

Key words

  • 2005 West Off Fukuoka Prefecture Earthquake
  • one-dimensional site response
  • peak ground velocity
  • Quaternary sediment
  • Kego fault