1.4.2. Intensity Scale

Intensity of an earthquake is measured in terms of its effects on human life. The intensity of an earthquake at a specific location depends on a number of factors. Some of them are:

♤ the total amount of energy released,

♤ the distance from the epicentre,

♤ the types of rocks and the degree of consolidation.

The Mercalli intensity scale is a scale used for measuring the intensity of an earthquake. The scale quantifies the effects of an earthquake on the Earth's surface, humans, objects of nature, and man-made structures on a scale of I through XII, with I denoting ‘not felt’, and XII ‘total destruction’. Data is gathered from individuals who have experienced the quake, and an intensity value will be given to their location.

Characteristic	Mercalli Scale	Richter Scale
Measures	The effects caused by earthquake	The energy released by the earthquake
Measuring Tool	Observation	Seismograph
Calculation	Quantified from observation of effect on earth’s surface, human, objects and man-made structures	Base-10 logarithmic scale obtained by calculating logarithm of the amplitude of waves.

Scale

I (not felt) to XII (total destruction)

From 2.0 to 10.0+ (never recorded). A 3.0 earthquake is 10 times stronger than a 2.0

earthquake.

Consistency

Varies depending on distance from

epicentre.

Varies at different distances from the epicentre, but one value is given for the earthquake as a

whole.

Table 1: Comparison between Richter and Mercalli Scale