Earthquake Calculator

The Richter magnitude scale, developed by Charles Richter in 1935, measures earthquake size on a logarithmic scale. Each unit increase corresponds to a tenfold increase in seismic wave amplitude (as recorded on a seismograph) and approximately a 31.6-fold increase in energy released. The energy ratio between two earthquakes is calculated as 10^(1.5 * delta_M), where delta_M is the magnitude difference. The factor of 1.5 comes from the empirical relationship between magnitude and energy first established by Gutenberg and Richter. This logarithmic scale reveals dramatic differences. A magnitude 7 earthquake releases about 31.6 times more energy than a magnitude 6, about 1,000 times more than a magnitude 5, and about 31,623 times more than a magnitude 4. The 2011 Japan earthquake (magnitude 9.1) released about 22,387 times more energy than the 1994 Northridge earthquake (magnitude 6.7). Modern seismology primarily uses the moment magnitude scale (Mw) rather than the original Richter scale for medium and large earthquakes. The Mw scale is based on the seismic moment, which directly measures the energy released. For most practical purposes, Richter and moment magnitudes give similar values. Earthquakes below magnitude 2.5 are generally not felt by people. Magnitude 2.5-5.4 are felt but rarely cause damage. Magnitude 5.5-6.0 cause slight damage to buildings. Magnitude 6.1-6.9 can be destructive in populated areas. Magnitude 7.0-7.9 are major earthquakes. Magnitude 8.0 and above are great earthquakes that can cause tremendous destruction.