Based on the lessons learned from the Great Hanshin-Awaji Earthquake 26 years ago, the government has evaluated the risk of active faults that have caused repeated earthquakes inland in the past.

Currently, there are 31 active faults nationwide where the degree of urgency of an earthquake is the same as or higher than that immediately before the Great Hanshin-Awaji Earthquake, and it is necessary to take measures such as making houses earthquake-resistant and fixing furniture.

The Great Hanshin-Awaji Earthquake was caused by a magnitude 7.3 earthquake with an epicenter in the southern part of Hyogo Prefecture, and a part of the active fault located from northwestern Osaka Prefecture to Awaji Island in Hyogo Prefecture moved.



In order to promote disaster prevention measures against earthquakes caused by active faults, the national government has set up the Headquarters for Earthquake Research Promotion, and among the active faults nationwide, the length exceeds about 20 km, and an earthquake will have a great impact on society. We have focused on active faults and evaluated risks by calculating the probability of an earthquake occurring within the next 30 years.

The degree of urgency of an earthquake is divided into four ranks, and active faults with a probability of 3% or more are ranked as the highest "S rank".



The probability of occurrence immediately before the Great Hanshin-Awaji Earthquake is 0.02% to 8%, which corresponds to the current "S rank".



Of the 114 major active faults nationwide, 31 are classified as "S rank" as of January 1, of which the "Itougawa-Shizuoka Tectonic Line Fault Zone" and the "Median Tectonic Line Fault Zone" The probability exceeds 8% in each of the eight active fault zones, including some sections of the "Line Fault Zone" and the "Miura Peninsula Fault Group," which is more urgent than before the Great Hanshin-Awaji Earthquake.



In addition, there are 35 "A rank" active faults with the next highest risk nationwide.



The "Futagawa Fault Zone" that caused the Kumamoto earthquake five years ago in 2016 was "A rank" in the evaluation just before the earthquake.

In some cases, an earthquake occurs on an "unknown" active fault

On the other hand, there are a number of cases in which previously unknown active faults, such as the 2004 Niigata Chuetsu Earthquake and the 2008 Iwate-Miyagi Nairiku Earthquake, shift and cause earthquakes.



If an earthquake occurs, it could cause great damage, and the Headquarters for Earthquake Research Promotion is calling for daily preparations such as seismic retrofitting of houses and fixing of furniture.

Eight active fault zones that are said to be particularly urgent

As of January 1, there are 31 active faults nationwide that are classified as "S rank", but the probability of these is over 8% just before the Great Hanshin-Awaji Earthquake, especially the degree of urgency. The following eight active fault zones are said to be high.



In descending order of urgency,


▽ section of "Itoigawa-Shizuoka Tectonic Line Fault Zone" in Nagano Prefecture


▽ "Fujikawa Kawaguchi Fault Zone" in Shizuoka Prefecture ▽


Part of "Hinaku Fault Zone" in Kumamoto Prefecture


▽ Nagano Prefecture "Sakai Pass / Kamiya Fault Zone"


▽ Section of Ehime Prefecture in "Median Tectonic Line Fault Zone"


▽ "Atera Fault Zone" in Gifu Prefecture and Nagano Prefecture


▽ "Miura Peninsula Fault Group" in Kanagawa Prefecture


▽ Hiroshima Prefecture It is the "Aki Nada Fault Zone" off the coast of Yamaguchi Prefecture.



Unlike plate-boundary earthquakes that occur in the Nankai Trough and the Japan Trench, earthquakes caused by active faults are characterized by long intervals of several thousand years, and the probability of occurrence within the next 30 years is calculated. Will be smaller.



However, even if the probability seems low, it does not mean that an earthquake will never occur, and suddenly a large tremor may strike.



It is important to prepare on a daily basis.