The Japanese government’s Earthquake Research Committee has just released the 2018 edition of the “National Earthquake Forecast Map” which predicts the probability of a major earthquake (with a seismic intensity level of Lower 6 or higher) occurring in Japan within the next thirty years. The key new finding in this year’s map is the sharply increased probability of a major quake hitting the southeastern Pacific coast of Hokkaido
On the Japanese seismic intensity scale of one to seven, in a Lower 6 level earthquake it would be difficult for people to keep standing, and furniture would move or topple over. Older wooden buildings with low quake resistance could also collapse. For reference, the June 18th earthquake that struck northern Osaka measured Lower 6.
The map is based on evaluation of data available as of January 1st, 2018, so it does not include any effects from the quake that struck northern Osaka on June 18th. Indeed, the 2018 quake probability map shows as high a probability of a major temblor occurring in northern Osaka prefecture as last year’s map.
The government has been publishing the probability map almost annually since 2005 to help the public prepare for a major quake.
Five Earthquake Probability Levels
The probability map is divided into five levels:
Yellow: Less than 0.1%
Light Orange: 0.1% to Less than 3%
Orange: 3% to Less than 6%
Darker Orange: 6% to Less than 26%
Dark Red: 26% to 100%
As can be seen in the map above, the probability of a major quake occurring in the greater Tokyo region, Shizuoka (in central Japan) and parts of the western region of Shikoku and Kinki (which includes Osaka, Kyoto, and Kobe) is high.
The biggest change in this year’s map was that the research committee increased the probability rating of a major quake occurring in the city of Kushiro (located on Hokkaido’s southeast Pacific coast) to 69%, a sharp jump of 22% points.
This change reflects research suggesting that major earthquakes accompanying massive tsunami have repeatedly occurred along Chishima trench off eastern Hokkaido in the past.
Sharp increases in probability were also given to the cities of Nemuro (on the eastern tip of Hokkaido) and the Hidaka region. In both cases, this was an increase of 15% points.
Kanto (Including Tokyo Capital Region)
In the Tokyo capital region, Chiba has the highest probability of having a major quake (at 85%), followed by 82% for Yokohama near the Sagamihara Trough, and 81% for Mito (in Ibaraki prefecture), both rising by 1% year-on-year.
Central Japan (Including Shizuoka, Nagoya, Wakayama)
Shizuoka City, the capital of Shizuoka, prefecture is located on the Pacific coast of Honshu (the main island). The map shows the probability of a major quake hitting Shizuoka at 70% (up one percentage point from 2017). A quake occurring in this region would happen along the Nankai Trough that extends southwest from the Pacific coast, running from the Kanto region down all the way to Okinawa.
The probability of a major earthquake occurring in the Nankai Trough has been rising every year as it is assumed to occur in a cycle and a major earthquake has not occurred there since 1946. This year’s evaluation of the Nankai Trough puts the probability of a major quake striking Nagoya at 46% and Wakayama at 58%).
Kinki (Including Osaka)
A number of cities in the Kinki region also have high chances (over 50%) of a major quake striking, as western Japan region has a number of active faults and has large plains prone to tremors,
The research committee raised the probability of a major quake occurring in the four prefectures (Ehime, Kagawa, Kochi, and Tokushima) of Shikoku by one to two percentage points from the previous year, as experts re-evaluated the risks posed by the massive active fault zone along the median tectonic line stretching through the Kinki, Shikoku and Kyushu regions. The city of Kochi was given a 75% probability of a major quake occurring.
Nowhere with a probability of zero
As the committee points out, there is no place in Japan with a zero probability of a Lower 6 level earthquake not occurring, and they encourage the public to check the quake resistance of their homes, schools, and offices and to take action to reinforce these structures if necessary. People should also take basic steps for disaster preparedness. For more information, please see:
Japan Seismic Hazard Information Station (J-SHIS)
You can access this year’s (and past year’s) earthquake probability map can here (in English): J-SHIS Map (English)
This online map allows you to search the earthquake probability forecast map by location (such as “Shinjuku” and sometimes by a specific ward in a city) in English, but does not allow detailed search by specific neighborhood (such as by “Chome” or Block number). You will also be asked to select from multiple search results (which are only displayed in Japanese). You can also zoom in and out to find your specific neighborhood or block, if you start by using a broader search term (such as a city or ward name).
The Japanese version of the earthquake forecast map allows for more detailed searches (by a specific address, such as Higashi Azabu 1-Chome), but search terms must be entered (or copy-and-pasted) in Japanese.