Abstract
Refraction measurements by the two ship method were conducted in July 1969 in the deep sea terrace of Hidaka, Hokkaido. The general features of the crustal structures derived are similar to those in the adjacent oceanic areas. Thick sediments cover the whole area, especially its northernmost part. The layer with a P-wave velocity of 6km/s is found in all profiles. That is, the crustal structure in this area is continental and similar to that off the Sanriku area.