Damage estimates released Thursday by the Hokkaido government show tsunamis could kill 149,000 people if a major earthquake hits off Japan's northernmost main island, surpassing a central government prediction by around 12,000.

But the report also said deaths could be significantly reduced if thorough evacuation measures are carried out swiftly, a conclusion that has prompted the Hokkaido government to further cooperate with municipalities to prepare for the worst-case scenario.

The estimates factored in damage from a megaquake and resulting tsunamis originating in the Japan Trench, which stretches from Hokkaido to east of the Boso Peninsula near Tokyo, and the Chishima Trench off the Chishima Islands, which are also known as the Kuril Islands.