Evaluating the effect of subway vibrations on H/V curves in a region in Tehran

In this study, with the purpose of evaluating site effect, a microtremor survey of 4 points near a subway station in Tehran was carried out. The data were recorded in two periods, first at midnight when there was no subway activity (vibration) and second at noon when subway activity was at its peak. The H/V spectral ratio was evaluated using Nakamura’s technique (1989) and it was plotted using the Geopsy software. Utilizing the H/V method the resonance frequency and amplification factor of the soil for each station was measured. After that the results for the two time periods were compared with each other and it was shown that the subway vibrations had a significant influence on resulting H/V curves, resonance frequency and amplification factor of the soil. It was proposed that for reducing the adverse effects of subway vibrations, it is better to carry out microtremor surveys at a time when subway activity is its lowest for example at midnight and also at a place where is far from moving subways if possible.