The size of an earthquake is defined by a magnitude scale and the scales are logarithmic, for example a magnitude 5 earthquake shakes the ground 10 times more than a magnitude 4 and around 32 times the energy released.1U.S. Geological Survey, "Earthquake Magnitude, Energy Release, and Shaking Intensity," usgs.gov, accessed September 2026. https://www.usgs.gov/programs/earthquake-hazards/earthquake-magnitude-energy-release-and-shaking-intensity For every minor increase of 0.1 in magnitude, the energy release increases by about 1.5 times.1U.S. Geological Survey, "Earthquake Magnitude, Energy Release, and Shaking Intensity," usgs.gov, accessed September 2026. https://www.usgs.gov/programs/earthquake-hazards/earthquake-magnitude-energy-release-and-shaking-intensity
One common scale is the Moment Magnitude (Mw) which shows how much energy is released. Magnitude is a measure of size and intensity is the measure of shaking at a location. The US uses the Modified Mercalli Intensity (MMI).