The Richter scale is used to measure the magnitude of earthquakes. The scale, more formally known as the Richter magnitude test scale, ranges from 0 to over 8.0. It is a logarithmic scale, meaning each unit of increase on the scale corresponds to an absolute increase by an order of magnitude, or factor of 10. Earthquakes measured at less than about 2 on the Richter scale are not very serious, and can barely even be measured, much less felt. An earthquake is usually considered much more serious once it hits about 5. At magnitudes of 7.0 or 8.0 the damage can be catastrophic.