Simulation of High-Frequency Strong Vertical Motions using Microtremor Horizontal-toVertical Ratios

We examined the possibility for simulation of vertical ground motions using microtremor horizontal-to-vertical spectral ratios. Comparing earthquake and microtremor horizontal-to-vertical spectral ratios, we showed that although microtremor horizontal-to-vertical ratios are smaller than earthquake-motion horizontal-to-vertical ratios, their spectral shapes are similar. Also, we showed that a correction factor to compensate for the difference between the two ratios is almost the same among geologically similar sites. We then tried to reproduce strong vertical ground motions for the 1995 Hyogo-ken Nanbu earthquake using corrected microtremor horizontal-to-vertical ratios. Vertical accelerations simulated were well reproduced in envelope and high-frequency contents.