Explanation table of JMA seismic intensity scale (February 1996)

The JMA seismic intensity scale, which provides a measure of the strength of the seismic motion, is measured with a seismic intensity meter. This table describes the situations and damage which may be caused by seismic motion of each seismic intensity. When using this table, please note the following:

  1. The seismic intensity announced by JMA is a value obtained with a seismic intensity meter, and it is not determined from observed phenomena described in this table;
  2. Sites where equal seismic intensity was observed would not necessarily suffer the same degree of damage, because damage depends on the type of construction and on the nature of the seismic motion. This table describes some typical situations which may appear. More or less damage than that described in the table may occur;
  3. Amplitudes of seismic ground motion are influenced greatly by underground structure and topography. The seismic intensity is a value observed at a site where a seismic intensity meter is installed. The seismic intensity occasionally varies even within a city. The seismic intensity is usually measured on the ground, but in general, the shaking on upper stories of buildings may be amplified greatly;
  4. A large earthquake generates long-period seismic waves. Even at locations far from the epicenter¡¤where the seismic intensity is rather small, the long-period waves may occasionally cause some peculiar damage such as the sloshing of oil in a tank and troubles with elevators;
  5. This table is prepared mainly based on the examples collected from recent damaging earthquakes. The table is subject to revision when new examples are collected or the present descriptions become inconsistent with actual situations, due to the improvement of earthquake resistant buildings and so on.
Seismic Intensity *1JMA Scale *2 People Indoor situations Outdoor situations Wooden houses Reinforced-concrete buildings Lifelines Ground and slopes
- 0.40 Imperceptible to people.
0.5 - 1.41 Felt by only some people in the building.
1.5 - 2.42 Felt by many people in the building. Some sleeping people awake. Hanging objects such as lamps swing slightly.
2.5 - 3.43 Felt by most people in the building. Some people are frightened. Dishes in a cupboard rattle occasionally. Electric wires swing slightly.
3.5 - 4.44 Many people are frightened. Some people try to escape from danger. Most sleeping people awake. Hanging objects swing considerably and dishes in a cupboard rattle. Unstable ornaments fall occasionally. Electric wires swing considerably. People walking on a street and some people driving automobiles notice the tremor.
4.5 - 4.95Lower Most people try to escape from a danger. Some people find it difficult to move. Hanging objects swing violently. Most unstable ornaments fall. Occasionally, dishes in a cupboard and books on a bookshelf fall and furniture moves. People notice electric-light poles swing. Occasionally, windowpanes are broken and fall, unreinforced concrete-block walls collapse, and roads suffer damage. Occasionally, less earthquake-resistant houses suffer damage to walls and pillars. Occasionally, cracks are formed in walls of less earthquake-resistant buildings. A safety device cuts off the gas service at some houses. On rare occasions water pipes are damaged and water service is interrupted. [Electrical service is interrupted at some houses.] Occasionally, cracks appear in soft ground, and rockfalls and small slope failures take place in mountainous districts.
5.0 - 5.45Upper Many people are considerably frightened and find it difficult to move. Most dishes in a cupboard and most books on a bookshelf fall. Occasionally, a TV set on a rack falls, heavy furniture such as a chest of drawers falls, sliding doors slip out of their groove and the deformation of a door frame makes it impossible to open the door. In many cases, unreinforced concrete-block walls collapse and tombstones overturn. Many automobiles stop because it becomes difficult to drive. Occasionally, poorly-installed vending machines fall. Occasionally, less earthquake-resistant houses suffer heavy damage to walls and pillars and lean. Occasionally, large cracks are formed in walls, crossbeams and pillars of less earthquake-resistant buildings and even highly earthquake-resistant buildings have cracks in walls. Occasionally, gas pipes and/or water mains are damaged. [Occasionally, gas service and/or water service are interrupted in some regions.]
5.5 - 5.96Lower Difficult to keep standing. A lot of heavy and unfixed furniture moves and falls. It is impossible to open the door in many cases. In some buildings, wall tiles and windowpanes are damaged and fall. Occasionally, less earthquake-resistant houses collapse and even walls and pillars of highly earthquake-resistant houses are damaged. Occasionally, walls and pillars of less earthquake-resistant buildings are destroyed and even highly earthquake-resistant buildings have large cracks in walls, crossbeams and pillars. Gas pipes and/or water mains are damaged. [In some regions, gas service and water service are interrupted and electrical service is interrupted occasionally.] Occasionally, cracks appear in the ground, and landslides take place.
6.0 - 6.46Upper Impossible to keep standing and to move without crawling. Most heavy and unfixed furniture moves and falls. Occasionally, sliding doors are thrown from their groove. In many buildings, wall tiles and windowpanes are damaged and fall. Most unreinforced concrete-block walls collapse. Many less earthquake-resistant houses collapse. In some cases, even walls and pillars of highly earthquake-resistant houses are heavily damaged. Occasionally, less earthquake-resistant buildings collapse. In some cases, even highly earthquake-resistant buildings suffer damage to walls and pillars. Occasionally, gas mains and/or water mains are damaged. [Electrical service is interrupted in some regions. Occasionally, gas service and/or water service are interrupted over a large area.]
6.5 -7 Thrown by the shaking and impossible to move at will. Most furniture moves to a large extent and some jumps up. In most buildings, wall tiles and windowpanes are damaged and fall. In some cases, reinforced concrete-block walls collapse. Occasionally, even highly earthquake-resistant houses are severely damaged and lean. Occasionally, even highly earthquake-resistant buildings are severely damaged and lean. [Electrical service, gas service and water service are interrupted over a large area.] The ground is considerably distorted by large cracks and fissures, and slope failures and landslides take place, which occasionally change topographic features.

*1 Value of instrumental seismic intensity
*2 The JMA seismic intensity scale

Notes

  1. Instrumental seismic intensity is a numerical one indicating the strength of the seismic motion at a site and measured with a seismic intensity meter. The JMA seismic intensity scale announced officially is obtained from the instrumental seismic intensity.
  2. Lifelines are utilities for power, communication, transportation and water supply.
  3. The descriptions given in [ ] of the "Lifelines" describe situations concerning electrical, gas and water service in particular for information.