Crustal movements caused by the Nemuro-Oki earthquake of 1973 were observed by means of leveling survey and tidal gauge measurment. It was found that the observed crustal movements were subsidence on the land and the maximum observed subsidence was about 7cm at Attoko from the above mentioned leveling survey.
In order to explain this subsidence, the low-angle reverse fault models were assumed and the vertical displacements were calculated by these models. Although it is impossible to obtain the unique solution because of a few data, the fault parameters obtained from a reasonable fault model are as follows,
fault dimension…100km×100km
dip angle…30°
direction of slip…N 60°W
dislocation…100cm (Ud:Us=2:1).
The direction of fault motion is the same one which occurred in this region, and then, this earthquake is interpreted as the low-angle reverse faulting, with the Pacific plate underthrusting against the Continental (the Asian) plate.