Fig. 4.
From: Long-term change of site response after the MW 9.0 Tohoku earthquake in Japan
Color-coded surface/borehole spectral ratios for the six stations. All the computed moving-window spectral ratios are aligned by the sequential number, rather than real time. The spectral ratio values are color-coded with red being high and blue being low. The two vertical dashed lines indicate the occurrence time of the Tohoku main shock, and the estimated time when most (95%) of the co-seismic changes are recovered. The horizontal solid and dotted lines show the reference value and uncertainties before and after the rapid recovery period defined as between the two vertical dashed lines. The white curve on the top of each panel shows the peak ground acceleration (PGA) value of the windowed seismogram used to compute the spectral ratio.