The
Richter scale was developed in 1935 by
Charles Francis Richter in partnership with
Beno Gutenberg, to assign a single number to quantify the energy released during an earthquake. The magnitude is defined as the logarithm of the ratio of the amplitude of waves measured by a seismograph
to arbitrary small amplitude. An earthquake that measures 5.0 on the
Richter scale has a shaking amplitude 10 times larger than one that
measures 4.0, and corresponds to a 31.6 times larger release of energy.
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| Richter Scale |
The scale is divided mainly into seven categories as depicted in the image above. Here are more details:
Less than 2.0 (Micro): Micro earthquakes, not felt, or felt rarely by sensitive people. Recorded by seismographs.
Frequency: Several million per year.
2.0 – 2.9 (Minor): Felt slightly by some people. No damage to buildings.
Frequency: Over one million per year
3.0 – 3.9 (Minor): Often felt by people, but very rarely causes damage. Shaking of indoor objects can be noticeable.
Frequency: Over 100,000 per year
4.0 – 4.9 (Light): Noticeable shaking of indoor objects and rattling noises. Felt by most
people in the affected area. Slightly felt outside. Generally causes
none to minimal damage. Moderate to significant damage very unlikely.
Some objects may fall off shelves or be knocked over.
Frequency: 10,000 to 15,000 per year
5.0 – 5.9 (Moderate): Can cause damage of varying severity to poorly constructed buildings. At
most, none to slight damage to all other buildings. Felt by everyone.
Casualties range from none to a few.
Frequency: 1,000 to 1,500 per year
6.0 – 6.9 (Strong): Damage to many buildings in populated areas. Earthquake-resistant structures survive with slight to moderate damage. Poorly-designed structures receive moderate to severe damage. Felt in wider areas; up to hundreds of miles/kilometers from the epicenter. Damage can be caused far from the epicenter. Strong to violent shaking in epicentral area. Death toll ranges from none to 25,000.
Frequency: 100 to 150 per year
7.0 – 7.9 (Major): Causes damage to most buildings, some to partially or completely
collapse or receive severe damage. Well-designed structures are likely
to receive damage. Felt in enormous areas. Death toll ranges from none
to 250,000.
Frequency: 10 to 20 per year
8.0 – 8.9 (Great): Major damage to buildings, structures likely to be destroyed. Will cause
moderate to heavy damage to sturdy or earthquake-resistant buildings.
Damaging in large areas, some totally destroyed. Felt in extremely large
regions. Death toll ranges from 1,000 to 1 million.
Frequency: One per year
9.0 and greater (Great): Near or at total destruction - severe damage or collapse to all
buildings. Damage and shaking extends to distant locations. Permanent
changes in ground topography. Death toll usually over 1,000.
Frequency: One per 10 to 50 years
