We have examined the effects of heavy traffic on dispersion curves analyzed by the space autocorrelation method. In order to observe short-period microtremors circular arrays of six seismometers with radiuses of 5 and 20m were deployed at the position 200m away from a road on which traffic was heavy. We took out waveforms with durations of 10s from the array data, and estimated power spectral densities and spatial autocorrelation coefficients. Changing the start time of the waveform segments, we repeated this procedure over entire records. It is revealed that the phase velocities analyzed depend on the intensity of microtremors.
