Abstract
On December 11, 1965, a 2.5 ton explosion was made in an abandoned tunnel of the Toyama mine, Kochi Pref. for the refraction survey of the crustal structure in Kiniki and Sikoku areas. In order to form a reverse profile to the Miboro explosions, 18 temporary stations were aligned to the NE direction from Kochi to the north of the lake Biwa with intervals of 20-30km. Three kinds of refracted waves with apparent velocities of 5.9km/sec, 6.5km/sec and 7.8km/sec were observed, although the seismograms were not high qualities. Some characteristic features with this explosions were as follows: 1) Pg waves with an apparent velocity of 5.9km/sec showed zero intercept time near the explosion site. 2) Most of wave energies were confined within Sikoku and were not propagated to long distances beyond the inland sea.
