Fig. 6.
From: Long-term change of site response after the MW 9.0 Tohoku earthquake in Japan
Percentage drop of resonance frequency plotted against PGA for the six stations. The blue and red circles show the percentage drop of resonance frequency measured from stacked spectral ratio in each PGA bin before and after the Tohoku main shock, respectively. The blue and red dashed lines show the least-squares fitting of the blue and red circles, respectively. The correlation coefficient (CC) values are shown at the bottom of each panel.