Abstract
On May 16th, 1968, at 09:49, an earthquake (Tokachi-oki Earthquake) with the magnitude of 7.8 occurred on the Pacific side of Tohoku and Hokkaido. Many of artificial embankments such as railroad basements, highway constructions and earth-fill dams were severely damaged. The connecting slopes to bridges were subsided in many cases, but the bridges were undamaged.
On the alluvial lowlands, especially newly reclaimed or graded lands for factory areas around urban districts of Hakodate, Aomori, Mutsu and Hachinoho, there occurred many cracks, depressions and sand-jetting.
It is characteristic of this earthquake that some steel-concrete buildings on the terrace surface collapsed.
Land falls and landslides in the valleys dissecting the uplands to the west of Hachinohe City were the most disasterous accidents, in which the earthquake acted as a trigger after a heavy rain amounting 160mm in three days.
