Earthquake Scales


European Macroseismic Scale
Mercalli Scale
Omori Scale
Richter Scale
Rossi-Forel Scale
Shindo Scale


European Macroseismic Scale (EMS)

A scale which denotes how strongly an earthquake affects a specific place.

1. Not felt
Not felt, even under the most favourable circumstances.
2. Scarcely felt
Vibration is felt only by individual people at rest in houses, especially on upper floors of buildings.
3. Weak
The vibration is weak and is felt indoors by a few people. People at rest feel a swaying or light trembling.
4. Largely observed
The earthquake is felt indoors by many people, outdoors by very few. A few people are awakened. The level of vibration is not frightening. Windows, doors and dishes rattle. Hanging objects swing.
5. Strong
The earthquake is felt indoors by most, outdoors by few. Many sleeping people awake. A few run outdoors. Buildings tremble throughout. Hanging objects swing considerably. China and glasses clatter together. The vibration is strong. Top-heavy objects topple over. Doors and windows swing open or shut.
6. Slightly damaging
Felt by most indoors and by many outdoors. Many people in buildings are frightened and run outdoors. Small objects fall. Slight damage to many ordinary buildings; for example, fine cracks in plaster and small pieces of plaster fall.
7. Damaging
Most people are frightened and run outdoors. Furniture is shifted and objects fall from shelves in large numbers. Many ordinary buildings suffer moderate damage: small cracks in walls; partial collapse of chimneys.
8. Heavily damaging
Furniture may be overturned. Many ordinary buildings suffer damage: chimneys fall; large cracks appear in walls and a few buildings may partially collapse.
9. Destructive
Monuments and columns fall or are twisted. Many ordinary buildings partially collapse and a few collapse completely.
10. Very destructive
Many ordinary buildings collapse.
11. Devastating
Most ordinary buildings collapse.
12. Completely devastating
Practically all structures above and below ground are heavily damaged or destroyed.


Mercalli Scale

I
Not felt except by a few under especially favourable circumstances.
II
Felt only by a few persons at rest, especially on upper floors of buildings. delicately suspended objects may swing.
III
Felt quite noticeably indoors, especially on upper floors of buildings, but people may not recognise it as an earthquake. Standing motor cars may rock slightly. Vibration like the passing of a heavy lorry and duration can be estimated.
IV
Felt indoors by many during the day, outdoors by a few. Some awakened at night. Dishes windows, doors disturbed, walls make a creaking sound. Sensation like a heavy lorry striking building. Standing motor cars rocked noticeably.
V
Felt by nearly everyone, many awakened. Some dishes , windows etc. Broken; a few instances of cracked plaster; unstable objects over turned. Disturbance of trees, poles, and other tall objects sometimes noticed. Pendulum clocks may stop.
VI
Felt by all; many frightened and run outdoors. Some heavy furniture moved; a few instances of fallen plaster or damaged chimneys. Damage slight.
VII
Everybody runs out doors. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable in poorly built or badly designed structures; some chimneys broken. Noticed by people driving motor cars.
VIII
Damage slight in specially designed structures, considerable in ordinary substantial buildings, with partial collapse; great in poorly built or badly designed structures. Panel walls thrown out of frame structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. Sand and mud ejected in small amounts. Changes in well water. Disturbs people driving motor cars.
IX
Damage considerable in specially designed structures; well designed frame structures thrown out of plumb; great in substantial buildings with partial collapse. Buildings shifted off foundations. Ground cracked conspicuously. Underground pipes broken.
X
Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundations; ground badly cracked. Rails bent. Landslides considerable from river banks and steep slopes. Shifted sand and mud. Water splashes over banks.
XI
Few, if any, masonry structures still standing. Bridges destroyed. Broad fissures in the ground. Underground pipe lines out of service. Earth slumps and land slips in soft ground. Rails bent greatly.
XII
Damage total. Waves seen on ground surfaces. Lines of sight and level distorted. Objects thrown up into the air.


The Omori Seismic Intensity Scale

A seven-point scale of seismic intensity, created by Fusakichi Omori. It relates various phenomena to maximum ground acceleration and is based on the behaviour of typical Japanese structures:

I. Maximum Acceleration = 300 mm/s
The shock is rather strong, so much so that it generally induces people to escape from their houses into the open. The walls of badly constructed brick houses crack slightly and some parquet falls down; ordinary wooden houses are shaken in such a degree that they loudly creak; furniture is overturned; trees are visibly shaken; the water in ponds and pools gets turbid, owing to the disturbance of the mud; pendulum clocks stop; some very badly built factory chimneys are damaged.
II. Maximum Acceleration = 900 mm/s
The walls in the wooden houses of Japan crack; old wooden houses get slightly out of plumb; the Japanese tombstones and the badly constructed stone lanterns are overturned; in a few cases the flow of the thermal and mineral springs is changed; ordinary factory chimneys are not damaged.
III. Maximum Acceleration = 1200 mm/s
About one-fourth of the factory chimneys are damaged; badly constructed brick houses are partially or totally destroyed; some old wooden houses are destroyed; wooden bridges are slightly damaged; some tombstones and stone lanterns are overturned; Japanese sliding doors (covered with paper) are broken; the tiles of wooden houses are displaced; some fragments of rocks are detached from the sides of the mountains.
IV. Maximum Acceleration = 2000 mm/s
All factory chimneys are ruined; the majority of the ordinary brick houses are partially or totally destroyed; some wooden houses are totally destroyed; the wooden sliding doors are mostly thrust out of their channels; crevices from 2 to 3 inches (5 to 7-1/2 cm) wide appear in low and soft grounds; here and there the embankments are slightly damaged; wooden bridges are partially destroyed; ordinarily constructed stone lanterns are overturned.
V. Maximum Acceleration = 2500 mm/s
All ordinary brick houses are very seriously damaged; about 3 percent of the wooden houses are totally destroyed; some Buddhist temples are ruined; the embankments are badly damaged; the railways are slightly contorted; ordinary tombstones are overturned; brick walls are damaged; here and there, large fissures from 1 to 2 feet (30 to 60 cm) wide appear along the banks of the watercourses. The water of rivers and ditches is thrown on the banks; the contents of the wells are disturbed; landslides occur.
VI. Maximum Acceleration = 4000 mm/s
The greater part of the Buddhist temples are ruined; from 50 to 80 percent of the wooden houses are totally destroyed; the embankments are almost destroyed; the roads through paddy fields are ruined and interrupted by fissures in such a degree that traffic by animals or vehicles is impeded; the railways are very much contorted; great iron bridges are destroyed; wooden bridges are partially or totally damaged; tombstones of solid construction are overturned; fissures some feet wide appear in the soil, and are sometimes accompanied by jets of water and sand; iron or terra cotta tanks embedded in the ground are mostly destroyed; all lowlying grounds are completely convulsed horizontally as well as vertically in such a degree that sometimes the trees and all the vegetation on them die off; numerous landslides take place.
VII. Maximum Acceleration = much more than 4000 mm/s
All buildings are completely destroyed except a few wooden constructions; some doors or wooden houses are thrown over distances from 1 to 3 feet; enormous landslides with faults and shears of the ground occur.


Richter Scale

Richter scale : A logarithmic scale (from 0-9) used to measure earthquake magnitude. It is based on seismic recordings and takes into account the distance from the epi-centre.
Developed in 1935 by Charles Richter in partnership with Beno Gutenberg, both of the California Institute of Technology, the scale was originally intended to be used only in a particular study area in California, and on seismograms recorded on a particular instrument, the Wood-Anderson torsion seismometer.

< 2 Micro : Microearthquakes, not felt. (8,000 per day)
2.0 - 2.9 Minor : Generally not felt, but recorded. (1,000 per day)
3.0 - 3.9 Minor : Often felt, but rarely causes damage. (49,000 p.a.)
4.0 - 4.9 Light : Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. (6,200 p.a.)
5.0 - 5.9 Moderate : Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings. (800 p.a.)
6.0 - 6.9 Strong : Can be destructive in areas up to about 100 miles across in populated areas. (120 p.a.)
7.0 - 7.9 Major : Can cause serious damage over larger areas. (18 p.a.)
8.0 - 8.9 Great : Can cause serious damage in areas several hundred miles across. (1 p.a.)
9.0 - 9.9 Great : Devastating in areas several thousand miles across. (1 per 20 years)
10.0 + Great : Never recorded (Unknown)

Richter Magnitude 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 5.0
TNT equivalent ( kgs ) 5.6 3 x 101 2 x 102 1 x 103 6 x 103 3 x 104 2 x 105 1 x 106 3 x 107
Joule equivalent 2 x 107 1 x 108 7 x 108 4 x 109 2 x 1010 1 x 1011 7 x 1011 4 x 1012 1 x 1014
Richter Magnitude 5.5 6.0 6.5 7.0 7.5 8.0 9.0 10.012.0
TNT equivalent ( kgs ) 2 x 108 1 x 109 6 x 109 5 x 1010 2 x 1011 1 x 1012 6 x 1012 1 x 1015 2 x 1017
Joule equivalent 7 x 1014 4 x 1015 2 x 1016 2 x 1017 7 x 1017 4 x 1018 1 x 1020 4 x 1021 7 x 1023


Rossi-Forel scale

Developed by Michele Stefano Conte de Rossi of Italy and Franois-Alphonse Forel of Switzerland in the 1800s this was one of the first scales used to determine earthquake intensities.
The 1873 version of the Rossi-Forel scale had 10 intensity levels:

I. Microseismic shock
Recorded by a single seismograph or by seismographs of the same model, but not by several seismographs of different kinds. The shock felt by an experienced observer.
II. Extremely feeble shock.
Recorded by several seismographs of different kinds. Felt by a small number of persons at rest.
III. Very feeble shock.
Felt by several persons at rest. Strong enough for the direction or duration to be appreciable.
IV. Feeble shock.
Felt by persons in motion. Disturbance of movable objects, doors, windows, cracking of ceilings.
V. Shock of moderate intensity.
Felt generally by everyone. Disturbance of furniture, ringing of some bells.
VI. Fairly strong shock.
General awakening of those asleep. General ringing of bells. Oscillation of chandeliers, stopping of clocks, visible agitation of trees and shrubs. Some startled persons leaving their dwellings.
VII. Strong shock.
Overthrow of movable objects, fall of plaster, ringing of church bells. General panic. No damage to buildings.
VIII. Very strong shock.
Fall of chimneys, cracks in the walls of buildings.
IX. Extremely strong shock.
Partial or total destruction of some buildings.
X. Shock of extreme intensity.
Great disaster, ruins, disturbance of the strata, fissures in the ground, rock falls from mountains.


Shindo Scale

0 / 0-0.4
People :
Imperceptible to people.
Peak ground acceleration : Less than 0.008 m/s

1 / 0.5-1.4
People :
Felt by only some people in the building.
Peak ground acceleration : 0.0080.025 m/s

2 / 1.5-2.4
People :
Felt by most people in the building. Some people awake.
Indoor situations : Hanging objects such as lamps swing slightly.
Peak ground acceleration : 0.0250.08 m/s

3 / 2.5-3.4
People :
Felt by most people in the building. Some people are frightened.
Indoor situations : Dishes in a cupboard rattle occasionally.
Outdoor situations : Electric wires swing slightly.
Peak ground acceleration : 0.080.25 m/s

4 / 3.5-4.4
People :
Many people are frightened. Some people try to escape from danger. Most sleeping people awake.
Indoor situations : Hanging objects swing considerably and dishes in a cupboard rattle. Unstable ornaments fall occasionally.
Outdoor situations : Electric wires swing considerably. People walking on a street and some people driving automobiles notice the tremor.
Peak ground acceleration : 0.250.80 m/s

5-lower / 4.5-4.9
People :
Most people try to escape from a danger. Some people find it difficult to move.
Indoor situations : Hanging objects swing violently.Most Unstable ornaments fall. Occasionally, dishes in a cupboard and books on a bookshelf fall and furniture moves.
Outdoor situations : People notice electric-light poles swing. Occasionally, windowpanes are broken and fall, unreinforced concrete-block walls collapse, and roads suffer damage.
Wooden houses: Occasionally, less earthquake-resistant houses suffer damage to walls and pillars.
Reinforced-concrete buildings : Occasionally, cracks are formed in walls of less earthquake-resistant buildings.
Lifelines : 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)
Ground and slopes : Occasionally, cracks appear in soft ground. and rockfalls and small slope failures take place in mountainous districts.
Peak ground acceleration : 0.801.40 m/s

5-upper / 5.0-5.4
People :
Many people are considerably frightened and find it difficult to move.
Indoor situations : 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.
Outdoor situations : 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.
Wooden houses: Occasionally, less earthquake-resistant houses suffer heavy damage to walls and pillars and lean.
Reinforced-concrete buildings : 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.
Lifelines : Occasionally, gas pipes and / or water mains are damaged.(Occasionally, gas service and / or water service are interrupted in some regions)
Ground and slopes : Occasionally, cracks appear in soft ground. and rockfalls and small slope failures take place in mountainous districts.
Peak ground acceleration : 1.402.50 m/s

6-lower / 5.5-5.9
People :
Difficult to keep standing.
Indoor situations : A lot of heavy and unfixed furniture moves and falls. It is impossible to open the door in many cases.
Outdoor situations : In some buildings, wall tiles and windowpanes are damaged and fall.
Wooden houses: Occasionally, less earthquake-resistant houses collapse and even walls and pillars of highly earthquake-resistant houses are damaged.
Reinforced-concrete buildings : 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.
Lifelines : Gas pipes and / or water mains are damaged.(In some regions, gas service and water service are interrupted and electrical service is interrupted occasionally.)
Ground and slopes : Occasionally, cracks appear in the ground, and landslides take place.
Peak ground acceleration : 2.503.15 m/s

6-upper / 6.0 -6.4
People :
Impossible to keep standing and to move without crawling.
Indoor situations : Most heavy and unfixed furniture moves and falls. Occasionally, sliding doors are thrown from their groove.
Outdoor situations : In many buildings, wall tiles and windowpanes are damaged and fall. Most unreinforced concrete-block walls collapse.
Wooden houses: Many, less earthquake-resistant houses collapse. In some cases, even walls and pillars of highly earthquake-resistant houses are heavy damaged.
Reinforced-concrete buildings : Occasionally, less earthquake-resistant buildings collapse. In some cases, even highly earthquake-resistant buildings suffer damage to walls and pillars.
Lifelines : 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.)
Ground and slopes : Occasionally, cracks appear in the ground, and landslides take place.
Peak ground acceleration : 3.154.00 m/s

7 / 6.5 - up
People :
Thrown by the shaking and impossible to move at will.
Indoor situations : Most furniture moves to a large extent and some jumps up.
Outdoor situations : In most buildings, wall tiles and windowpanes are damaged and fall. In some cases, reinforced concrete-block walls collapse.
Wooden houses: Occasionally, even highly earthquake-resistant buildings are severely damaged and lean.
Reinforced-concrete buildings : Occasionally, even highly earthquake-resistant buildings are severely damaged and lean
Lifelines : Electrical service gas service and water service are interrupted over a large area.
Ground and slopes : The ground is considerably distorted by large cracks and fissures, and slope failures and landslides take place, which occasionally change topographic features.
Peak ground acceleration : Greater than 4 m/s