Earth Planets Space, Vol. 58 (No. 1), pp. 105-110, 2006LETTER
Toshimi Satoh1 and Hiroshi Kawase2
1Institute of Technology, Shimizu Corporation, 4-17 Etchujima 3-chome, Koto-ku, Tokyo 135-8530, Japan
2Deptartment of Architecture and Urban Design, Faculty of Human-Environment Studies, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
(Received August 8, 2005; Revised December 6, 2005; Accepted December 7, 2005; Online published January 27, 2006)
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.