M9 Earthquake Is Coming

Earthquake Research Committee of Japanese government released its long-term assessment for major earthquake around Japan. It concluded that there would be a high possibility of super great earthquake with magnitude 9 urgently occurring offshore Hokkaido Island. The committee calculated the likeliness of that earthquake as between 7% to 40% within next three decades.

It was the first announcement of long-term assessment by the committee these 13 years. Assessment of super great earthquake was the first one ever. Because the basic criterion of research was changed after East Japan Great Earthquake in 2011, the size or possibility of great earthquake in each hypocenter area around Japan was accordingly upraised.

The committee calculated that a super earthquake in the class of M9, which had been recognized as occurring every 500 years, would actually be coming within 340 to 380 years after the previous one. Since the last one in the eastern offshore of Hokkaido occurred in between 1611 and 1637, or about 400 years ago, the committee assumed that the next one is coming soon.

Among three regions in Chishima Trench, located in Pacific Ocean along the eastern shore of Hokkaido, the possibility of a great earthquake with M8 was the highest in offshore Nemuro, which marked 70%. The next was in offshore Shikotan and Etorofu with 60%, followed by offshore Tokachi with 7%. The committee will determine how high collateral tsunami will be or impact of quake on the land.

So what can we do before that? One thing should be obtaining more accurate data. But since the assessment is based on the research of strata, the accuracy cannot be so high. Further research of dynamism of underground is indispensable. More important is how to save human lives. While the area does not have dense population, a super great earthquake can cause thousands of death. Each city or town has reinforced municipal office or made evacuation plan. Those measures have to be reviewed with new assessment.

Well, how about old or disable people in the houses? Will they be able to evacuate in a super great earthquake? Some cities have individual evacuation plan for those people, which is still not sure in terms of workability. As long as the basic principle for saving life in tsunami is do-it-yourself, it is possible that those weak people will be left behind. The most important thing is to imagine the devastation seriously.