Big Quake Risks Surge in Eastern Hokkaido: Govt Committee

June 26, 2018

Tokyo- The possibility of a powerful earthquake of lower 6 or above on the Japanese seismic intensity scale of 7 occurring in the next 30 years has sharply increased in the eastern part of Japan's northernmost prefecture of Hokkaido, a government report showed Tuesday.

The likelihood of such a strong earthquake jumped to 69 pct from 47 pct projected last year for the city of Kushiro and to 78 pct from 63 pct for the city of Nemuro.

The new predictions are part of the 2018 National Seismic Hazard Maps for Japan compiled by the government's Earthquake Research Committee. The report shows quake probabilities for sites where administrative centers of local governments are located.

The higher risks reflected the committee's new long-term forecast of a giant earthquake occurring along the Chishima trench off Hokkaido's eastern coast, announced in December last year.

The probability of a major earthquake with a magnitude of about 8 taking place at the trench off Nemuro within the next 30 years stands at around 80 pct, according to the committee's latest hazard maps.

The committee sees that a predicted huge temblor in the Nankai Trough off the Pacific coast of central to southwestern Japan is drawing closer.

The possibility of a powerful earthquake with a magnitude of 8 to 9 occurring along the trough within the next 30 years stands at 70-80 pct, according to the committee.

The new hazard maps showed higher possibilities of major quakes of lower 6 or above taking place on the Pacific side of the Japanese archipelago, from the Kanto eastern region to the Shikoku western region, reflecting the very high likelihood of the Nankai Trough temblor.

The chances of lower 6 or stronger quakes stood the highest among all locations at 85 pct for the city of Chiba in eastern Japan. The city also topped the list in last year's hazard maps.

The cities of Yokohama and Mito, both in eastern Japan, came in second and third, with the possibilities standing at 82 pct and 81 pct, respectively.

As the committee made the new predictions as of Jan. 1, they do not reflect the 6.1-magnitude earthquake that rocked the northern part of Osaka Prefecture, western Japan, on June 18 and measured up to lower 6.

The likelihood of such a strong earthquake stood at 56 pct for the city of Osaka in the new report, unchanged from last year.

The connection between the latest temblor in Osaka and a nearby fault zone is yet to be clarified. The committee plans to examine it in its long-term evaluation of active faults in the Kinki region, including Osaka, and other parts of the country, which will be announced next year at the earliest.

The possibility of a lower 6 or stronger earthquake stands at 48 pct for a central Tokyo site where the Tokyo metropolitan government building is located, much lower than the figures for Chiba and Yokohama, which are not far from Tokyo.

"This is because the metropolitan government building happens to be sitting on hard soil," said University of Tokyo Prof. Naoshi Hirata, who chairs the committee.

He said, however, that large cities in general, including Osaka, are located on flat land that is prone to shaking. "We recommend residents to get prepared for quakes by making their houses quake-resistant and securing their furniture to the wall," Hirata added. Jiji Press