We observed three explosions along a 60 km profile in the central part of the Kitakami massif, northeastern Honshu, Japan. Explosion sites and most of the observation sites were located on hard-rock outcrops. Using P-wave first arrivals, the average Q
P along ray paths and site amplification factors were determined for the frequency range between 6 and 30 Hz based on the amplitude spectra decay with distance. Q
P increased proportional to f
n (n_??_0.9). The difference in amplification factors among hard-rock sites was as much as a factor of five for frequencies lower than 12 Hz and became large at higher frequencies. Q
S and S-wave site amplification factors were obtained only for 5 and 7.5 Hz. Q
S was slightly larger than Q
P, but the difference was not significant. S-wave site amplification factors were more variable than those of P-wave among the stations.
View full abstract