Observations of microtremors were carried out to estimate the S-wave velocity structure by using arrays of seismographs around the Kyoto Research Park. The observation points were so arranged that equilateral triangle arrays may be formed with maximum radii at 0.2 km, 0.4 km and 0.8 km respectively with the premises of the Kyoto Research Park as the center. The seismographs have used seven vertical movement components (PELS), and were adjusted to a period of eight seconds. In addition, high-cut filters of 4 Hz were used because the observation areas are located in urban areas with heavy traffic. The analysis has used the spatial self-correlation method as a means to estimate phase velocity of surface waves contained in microtremors. As a result, phase velocity estimation has become possible for frequencies from about 0.4 Hz to 2 Hz, whereas the S-wave velocity structure was estimated to a depth of down to about 900 m by using as reference the result of the reflection method exploration having been carried out in the present areas. In addition, it was suggested that microtremors with frequencies higher than 1 Hz are in unsteady state in terms of time or space. 4 refs., 7 figs., 1 tab.