Earthquake Intensity Scale

The Modified Mercalli Intensity (MMI) scale is used to measure the intensity of earthquakes based on their effects on people, buildings, and the environment. Here is a detailed breakdown of the intensity levels:

Intensity Levels

Light (MMI < 4)

Generally felt by people indoors, especially on upper floors. Hanging objects may swing slightly.

Moderate (MMI 4-5)

Felt by most people indoors and some outdoors. Dishes, windows, and doors may rattle.

Strong (MMI 5-6)

Felt by all people indoors and many outdoors. Some heavy furniture may move.

Very Strong (MMI 6-7)

Felt by all people. Some walls may crack, and some buildings may sustain slight damage.

Severe (MMI 7-8)

Significant damage to buildings. Some buildings may collapse. Heavy furniture overturned.

Violent (MMI 8-9)

Extensive damage to buildings. Many buildings collapse. Large landslides possible.

Extreme (MMI ≥ 9)

Total destruction. Most buildings destroyed. Ground surface waves visible.

How MMI is Calculated

The MMI value is calculated using an empirical formula that takes into account:

  • Earthquake magnitude
  • Distance from the epicenter
  • Depth of the earthquake