Damage estimates released Thursday by the Hokkaido government show tsunami could kill 149,000 people in the event 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 swiftly carried out, a conclusion prompting 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 tsunami originating in the Japan Trench, which stretches from Hokkaido to east of the Boso Peninsula near Tokyo, and the Chishima Trench, which lies off the Chishima Islands, also known as the Kuril Islands.
The Hokkaido government revised the estimates by including data gathered from geological surveys carried out so far and factoring in details such as specific evacuation routes and their distance from oncoming tsunami.
The central government had predicted in December that up to 199,000 could die across seven prefectures including Hokkaido in the event a massive earthquake occurred along the Japan or Chishima trenches, with 137,000 of the deaths projected for Hokkaido.
Central government estimates had shown up to 19,000 could die in a quake scenario as a result of not being able to find proper shelter indoors, being swept away by tsunami or as a result of hypothermia. But the Hokkaido government estimated 66,000 would die, by factoring in people being trapped and isolated on roads during evacuation.
The number of buildings predicted to be completely destroyed by a megaquake was also revised from the state's estimate of up to 1,700 to 6,200 after the theoretical seismic intensity was increased.
"In order to reduce the number of deaths, it is important for residents to be conscious of infrastructure such as seawalls and evacuation procedures," said Shigeyuki Okada, a visiting professor at Hokkaido University's Center for Natural Hazards Research.
"I want Hokkaido residents to think about how to evacuate from their homes and how long it will take to get to safety."
The Hokkaido government said it will use the new estimates for disaster prevention education, as well as incorporate them when coordinating with local governments in considering the development of infrastructure such as tsunami evacuation buildings.