Fig. 4.

(a) Example of KiK-net stations where linear borehole response is computed at 68% (dark gray area) and 95% (light gray area) confidence limits. Black line represents the nonlinear borehole response computed using the M_w 9 Tohoku data. (b) average linear-to-nonlinear borehole response ratios for all KiK-net sites for different V_s30 classes. When this ratio is greater than one means that the soil behaves nonlinear. Note the clear separation among classes and the broadband nonlinear response (3 to 30 Hz) for soils having V_s30 < 400 m/s.