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Earthquake Scales

Richter Magnitude, Moment Magnitude and Mercalli Intensity.

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earthquake damage scale

The intensity of an earthquake can be described by scales as

  • Moment magnitude (MW)
  • Mercalli intensity
  • Richter magnitude (ML)
 Mercalli IntensityRicher MagnitudeMoment MagnitudeActual Observation of the Earthquake
Instrumental I 2 1.0 - 3.0 Micro earthquakes, usually not felt - detected by instruments
Feeble II 2 3.9 Often felt, especially on upper floors - detected by instruments
Slight III 3 4.0 Felt noticeably indoors, vibration like passing vehicles, cars may rock
Moderate IV   4.9 Felt indoors by many, felt outdoors by few. Dishes and doors disturbed, like a heavy truck nearby, walls-cracking sound
Rather Strong V 4 5.0 Felt by most people, slight damage. Some dishes and windows broken, some cracked plaster, trees disturbed
Strong VI 5 5.9 Felt by all, many frightened and run outdoors. Damage minor to moderate
Very Strong VII 5 - 6 6.0 Everyone runs outdoors. Much damage to poor designed buildings, some chimneys broken, noticed by people driving cars
Destructive VIII 6 6.9 Everyone runs outdoors. Damage moderate to major. Minor damage to well designed structures, major damage in poor designed structures. Chimneys, columns and walls falls. Heavy furniture turned. Well water changes, sand and mud ejected
Ruinous IX 7 7.0 Can cause serious damage over larger areas. Major damage in all structures, ground cracked, pipes broken, shift foundation
Disastrous X 7 - 8   Major damage, most masonry and frame structures destroyed. Ground badly cracked, landslides, water sloshed over river banks, rails bent
Very Disastrous XI 8   Almost all masonry structures destroyed, bridges fall, big fissures in ground, land slumps, rails bent greatly
Catastrophic XII >8   Devastating in areas several thousand miles across. Total destruction, Ground surface waves seen, objects thrown in the air. All constructions destroyed.
  • Mercalli Intensity - based on actual observations of the damage - can not be measured on instruments
  • Moment Magnitude - based on energy released - logarithmic scale
  • Richter Magnitude - based on the movement of a needle - logarithmic scale
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