Japan Meteorological Agency seismic intensity scale

The Japan Meteorological Agency seismic intensity scale is a seismic scale

Seismic scale

A seismic scale is used to calculate and compare the severity of earthquakes....

used in Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

and Taiwan

Taiwan

Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...

to measure the intensity of earthquake

Earthquake

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

s. It is measured in units of . Unlike the moment magnitude scale

Moment magnitude scale

The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...

(formerly Richter scale), which measures the energy released by the earthquake, the JMA

Japan Meteorological Agency

The or JMA, is the Japanese government's weather service. Charged with gathering and reporting weather data and forecasts in Japan, it is a semi-autonomous part of the Ministry of Land, Infrastructure and Transport...

scale describes the degree of shaking at a point on the Earth's surface, and is analogous to the Mercalli intensity scale

Mercalli intensity scale

The Mercalli intensity scale is a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake, and is distinct from the moment magnitude M_w usually reported for an earthquake , which is a measure of the energy released...

. The intensity of an earthquake is not totally determined by its magnitude, and varies from place to place; for example, a quake may be described as "shindo 4 in Tokyo, shindo 3 in Yokohama, shindo 2 in Shizuoka".

The JMA operates a network of 180 seismographs and 627 seismic intensity meters and provides real-time earthquake reports to the media and on the internet.

History

Japan experiences approximately 400 earthquakes every day, although the vast majority are shindo scale "0" or less and detectable only using specialist apparatus.

The Japan Meteorological Agency (JMA

Japan Meteorological Agency

) first assigned a four stage Shindo in 1884, with the levels: 微 (faint), 弱 (weak), 強 (strong), and 烈 (violent).

In 1898 this scale was changed to a numerical system, assigning earthquakes levels 0–7.

In 1908, the levels on this scale were given descriptions, and earthquakes were assigned levels based on their perceived effect on people. This scale was widely used during the Meiji period

Meiji period

The , also known as the Meiji era, is a Japanese era which extended from September 1868 through July 1912. This period represents the first half of the Empire of Japan.- Meiji Restoration and the emperor :...

, and revised during the Shōwa period

Showa period

The , or Shōwa era, is the period of Japanese history corresponding to the reign of the Shōwa Emperor, Hirohito, from December 25, 1926 through January 7, 1989.The Shōwa period was longer than the reign of any previous Japanese emperor...

with the descriptions seeing an overhaul.

Following the Great Hanshin earthquake

Great Hanshin earthquake

The Great Hanshin earthquake, or Kobe earthquake, was an earthquake that occurred on Tuesday, January 17, 1995, at 05:46 JST in the southern part of Hyōgo Prefecture, Japan. It measured 6.8 on the moment magnitude scale , and Mj7.3 on JMA magnitude scale. The tremors lasted for approximately 20...

in 1995, levels 5 and 6 were divided in two, giving a total of 10 levels of earthquake: 0–4, weak/strong 5 （５弱、５強）, weak/strong 6 （６弱、６強） and 7.

The Shindo scale has been used in Japan from 1996 without change.

JMA scale explanation

The JMA Scale runs from 0 to 7, with 7 being the strongest. The Mercalli intensity scale

Mercalli intensity scale

is sometimes used together with the Shindo; however this is not usual practice in Japan. Real-time earthquake reports are calculated automatically from measurements of ground acceleration. The JMA reports the earthquake level based on the ground acceleration, measured automatically with seismic intensity meters. There is no simple and linear relationship between Shindo Number and peak ground acceleration

Peak ground acceleration

Peak ground acceleration is a measure of earthquake acceleration on the ground and an important input parameter for earthquake engineering, also known as the design basis earthquake ground motion...

,^, so the values of the table below should only be regarded as an approximate orientation.

Shindo scale
Magnitude-Shindo Number (Shindo Number in Japanese) / Meter reading	People	Indoor situations	Outdoor situations	Wooden houses	Reinforced-concrete buildings	Lifelines	Ground and slopes	Peak ground acceleration Peak ground acceleration Peak ground acceleration is a measure of earthquake acceleration on the ground and an important input parameter for earthquake engineering, also known as the design basis earthquake ground motion...
0 (0) / 0–0.4	Imperceptible to people.							Less than 0.008 m/s²
1 (1) / 0.5–1.4	Felt by only some people indoors.							0.008–0.025 m/s²
2 (2) / 1.5–2.4	Felt by most people indoors. Some people awake.	Hanging objects such as lamps swing slightly.						0.025–0.08 m/s²
3 (3) / 2.5–3.4	Felt by most people indoors. Some people are frightened.	Dishes in a cupboard rattle occasionally.	Electric wires swing slightly.					0.08–0.25 m/s²
4 (4) / 3.5-4.4	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.					0.25–0.80 m/s²
5-lower (5弱) / 4.5-4.9	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.	0.80–1.40 m/s²
5-upper (5強) / 5.0–5.4	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 fall, sliding doors slip out of their groove and the deformation of door frames makes it impossible to open doors.	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)	Occasionally, cracks appear in soft ground. and rockfalls and small slope failures take place in mountainous districts.	1.40–2.50 m/s²
6-lower (6弱) / 5.5–5.9	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.	2.50–3.15 m/s²
6-upper (6強) / 6.0–6.4	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.)	Occasionally, cracks appear in the ground, and landslides take place.	3.15–4.00 m/s²
7 (7) / 6.5 and up	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 buildings 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.	Greater than 4 m/s²

External links

Up dating information of earth earthquakes in Japan in last 7 days, Japanese language. Circled number is Shindo(震度) Number.　Format is Hypocenter of earthquakes, location, north latitude, east longitude and depth.
JMA Seismic Intensity Scale in both Japanese and English language.

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History

JMA scale explanation

See also

External links