I. Instrumental

Not felt by many people unless in favourable conditions.

II. Feeble

Felt only by a few people at best, especially on the upper floors of buildings. Delicately suspended objects may swing.

III. Slight

Felt quite noticeably by people indoors, especially on the upper floors of buildings. Many do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated.

IV. Moderate

Felt indoors by many people, outdoors by few people during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably. Dishes and windows rattle alarmingly.

V. Rather Strong

Felt outside by most, may not be felt by some outside in non-favourable conditions. Dishes and windows may break and large bells will ring. Vibrations like large train passing close to house.

VI. Strong

Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken; books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight.

VII. Very Strong

Difficult to stand; furniture broken; damage negligible in building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by people driving motor cars.

VIII. Destructive

Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture moved.

IX. Ruinous

General panic; damage considerable in specially designed structures, well designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.

X. Disastrous

Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundation. Rails bent.

XI. Very Disastrous

Few, if any masonry structures remain standing. Bridges destroyed. Rails bent greatly.

XII. Catastrophic

Total damage - Almost everything is destroyed. Lines of sight and level distorted. Objects thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move position.

Richter Magnitudes

Description

Earthquake Effects

Frequency of Occurrence

Less than 2.0

Micro

Microearthquakes, not felt.

About 8,000 per day

2.0-2.9

Minor

Generally not felt, but recorded.

About 1,000 per day

3.0-3.9

Often felt, but rarely causes damage.

49,000 per year (est.)

4.0-4.9

Light

Noticeable shaking of indoor items, rattling noises. Significant damage unlikely.

6,200 per year (est.)

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 per year

6.0-6.9

Strong

Can be destructive in areas up to about 160 kilometres (100 mi) across in populated areas.

120 per year

7.0-7.9

Major

Can cause serious damage over larger areas.

18 per year

8.0-8.9

Great

Can cause serious damage in areas several hundred miles across.

1 per year

9.0-9.9

Devastating in areas several thousand miles across.

1 per 20 years

10.0+

Epic

Never recorded; see below for equivalent seismic energy yield.

Extremely rare (Unknown)