The refraction experiments were conducted to investigate the underground structures reaching the basement by analyzing the results of the artificial earthquakes the explosion earthquake research group produced in City of Kobe and the Hanshin District on December 12 to 15, 1995. Considering that noise level can exceed 1 mkine in an urban area even in the mid-night, the courses of traverse were drawn focusing on Points S2 through S4 and U1. The earthquake waves from Points S2 through S4 are generally low in amplitude. However, the major components of the signals have a dominant frequency exceeding 10Hz, which makes them distinguishable from urban noise having a lower frequency, contrary to the previous indication that such a low-amplitude wave might not be distinguishable. On the other hand, the signals from the explosion at Point 4 in Awaji Island cannot be distinguished in the urban area, even on the nearby course of traverse D. At present, the analytical group is organized to read various phases running and analyze the P-velocity structures. 2 refs., 10 figs., 1 tab.