How to Measure Earthquakes

Written By: Heidi Stonehill Executive Editor

February 21, 2024

Wondering how earthquakes are measured? Seismologists have developed a new measurement of earthquake size, called the Moment Magnitude.

All earthquakes can now be compared on the same scale with the Moment Magnitude. Previously, the Richter scale was used, however, it is precise only for measuring earthquakes of a certain size and at a certain distance from a seismometer.

See the Moment Magnitude chart below.

Magnitude	Effect
Less than 3	Micro
3–3.9	Minor
4–4.9	Light
5–5.9	Moderate
6–6.9	Strong
7–7.9	Major
8 or more	Great

Heidi Stonehill

Executive Editor

Heidi Stonehill is the Executive Editor for The Old Farmer’s Almanac, joining the team in 2001. As such, she manages the content development of the Almanac’s line of wall, engagement, box, and special...