Most scales are based on the amplitude of seismic waves recorded on seismometers. Another scale is based on the physical size of the earthquake fault and the amount of slip that occurred.

About 55 earthquakes a day – 20,000 a year – are recorded by the National Earthquake Information Center. A quick guide to how they are measured.

Magnitude describes a quake’s strength Magnitude is the measurement of the strength of an earthquake, and it’s usually expressed using the Richter Scale.

A new kind of earthquake has been detected in western Canada, one that shakes the ground slower and longer than typical ...

Magnitude is the measurement of the strength of an earthquake, and it’s usually expressed using the Richter Scale. Larger, longer-lasting earthquakes have higher magnitudes than smaller, shorter ...