While the geodesic data indicate that the Pacific coast of eastern Hokkaido is sinking for the past hundred years, the geological data shows slow coastal uplift for the past hundred of thousands years. In order to solve this mysterious controversy, the Active Fault Research Center has investigated volcanic ash deposit, tsunami deposit and fossil diatoms in the coastal geological layers, and found a coastal uplift of 1 to 2 m over decades following multi-segment interplate earthquakes occurred in the 17th century. A model computation indicates that the coastal uplift is due to fault movement at a depth below the seismogenic zone of the interplate earthquake.