What is the Difference Between Earthquake Magnitude and Intensity?

The difference between earthquake magnitude and intensity lies in what they measure and how they are determined:

• Magnitude is a measure of the size of an earthquake, specifically the energy released at the source of the earthquake. It is determined from measurements on seismographs and remains unchanged with distance from the earthquake.
• Intensity describes the degree of shaking caused by an earthquake at a given place. It measures the strength of shaking produced by the earthquake at a certain location, and it decreases with distance from the earthquake epicenter. Intensity is determined from effects on people, human structures, and the natural environment.

Magnitude is often measured using the Richter scale or the moment magnitude scale, while intensity is typically measured using the Modified Mercalli Intensity Scale or the Rossi-Forel scale. The Modified Mercalli Intensity Scale ranges from I (Not felt) to XII (Total devastation), with each intensity level assigned based on the observed effects of the earthquake.

Comparative Table: Earthquake Magnitude vs Intensity

The table below summarizes the difference between earthquake magnitude and intensity:

Earthquake magnitude and intensity are distinct characteristics of earthquakes:

• Magnitude: This quantifies the size of an earthquake and represents the amount of energy released during it. The moment magnitude scale (MW) is the preferred method for measuring earthquake magnitude today as it works over a wider range of earthquake sizes and is applicable globally.

• Intensity: This measures the amount of shaking at a particular location during an earthquake. The Modified Mercalli Intensity Scale is one of the most commonly used intensity scales, ranking earthquake shaking from I (not felt) to XII (total damage). The intensity of an earthquake varies greatly from place to place and depends on factors such as the distance from the epicenter and the local geology.