The Richter magnitude scale is a scale of numbers used to tell the size of earthquakes. Charles Richter developed the Richter Scale in 1935. His scale was based on the seismogram measured by a particular type of seismometer at a distance of 100 kilometres (62 mi) from the earthquake.
Earthquakes 4.5 or higher on the Richter scale can be measured by tools all over the world.
The scale is logarithmic, with a base of 10. The amplitude of an earthquake that scores 3.0 is about 10 times the amplitude of one that scores 2.0. The energy that is released increases by a factor of about 32.
|Descriptor||Richter Magnitude number||Damage caused by the earthquake||Frequency of occurrence|
|Micro||Less than 2.0||Micro (very small) earthquakes, people cannot feel these.||About 8,000 each day|
|Very minor||2.0-2.9||People do not feel these, but seismographs are able to detect them.||About 1,000 per day|
|Minor||3.0-3.9||People often feel these, but they rarely cause damage.||About 49,000 each year|
Objects inside houses are disturbed, causing noise. Nothing is damaged.
|About 6,200 each year|
Buildings that are not built well may be damaged. Light objects inside a house may be moved.
|About 800 per year|
Moderately powerful. May cause a lot of damage in a larger area.
|About 120 per year|
|Major||7.0-7.9||Can damage things seriously over larger areas.||About 18 per year|
|Great||8.0-9.9||Massive damage is caused. Heavy objects are thrown into the air and cracks appear on the ground, as well as visible shockwaves. Overhead highways may be destroyed, and buildings are toppled.||About 1 per 20 years|
|Meteoric||10.0+||There are no records of anything of this size. The vibration is about the same as that of a 15 mi meteor.||Unknown|
(Adapted from U.S. Geological Survey documents)
The earthquake with the biggest recorded magnitude was the Great Chilean Earthquake. It had a magnitude of 9.5 (approximately 9.5 on the Richter scale) and occurred in 1960. About 6,000 people died because of the earthquake.
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