The Mainichi Shimbun answers some common questions readers may have about very strong earthquakes in Japan.
Question: What is the Japanese earthquake intensity scale?
Answer: The Japanese earthquake intensity scale ranges from 0-7 with 10 levels (levels 5 and 6 are divided into weak and strong subcategories), with the strongest tremor being level 7. Furniture not fixed in place bounces and topples over while the pillars of the first and middle floors of many reinforced concrete buildings with low earthquake resistance often collapse.
Q: Which earthquakes have hit level 7?
A: The Great Hanshin Earthquake in 1995, the Chuetsu Earthquake in Niigata Prefecture in 2004, the Great East Japan Earthquake in 2011, and most recently both the major foreshock and main shock of the Kumamoto Earthquake in April 2016. It is predicted that sometime soon, another level-7 earthquake will occur along the Nankai Trough, affecting prefectures on Japan's Pacific coast. At a meeting in June this year, the governors of these coastal prefectures concluded that in a worst-case scenario, a major Nankai Trough quake would hit level-7 intensity in 10 prefectures and 151 municipalities, and requested that the national government strengthen countermeasures.
Q: Is there anything we can do to prepare for a level-7 earthquake?
A: There is no way to bring the damage down to zero. However, by steadily continuing to increase the earthquake resistance of buildings, fix furniture to the floor, and reinforce areas with unstable ground, it is possible to reduce damage. Instead of believing that earthquakes of this size only happen to other people, accepting that an earthquake of that size could occur at any time and making personal preparations is crucial. (Answers by Kazuki Iida, Science & Environment News Department)