![]() ![]() The Richter scale is logarithmic, meaning that for each increase in the magnitude there is a 10-fold increase in the shaking. The first part of the definition creates the most confusion. The definition is an excellent place to start dissecting the problems with the Richter magnitude. It is defined as the logarithm of the amplitude (measured in thousandths of millimeters or microns) of the largest seismic wave measured 100 km from the epicenter on a particular brand of seismometer. Finally, the fourth and perhaps least known is the best estimate of the size of the earthquake, the moment magnitude (M w) The Richter MagnitudeĬharles Richter developed the Richter magnitude in 1935. The body-wave (M B) and surface-wave magnitudes (M S) are offshoots of the Richter magnitude using those particular waves only. The most popular and well known is the Richter magnitude (M L), also known as the local magnitude. There are at least 4 different measurements of magnitude in use today. Earthquake magnitude: M B, M L, M S, M w - and what is the Richter Magnitude anyways? The size of earthquakes is typically given as a magnitude. ![]() When one asks "how big was that earthquake?" the answer is qualitative because it depends on what is meant by "big." There are several ways that the size of the earthquake can be measured quantitatively. How big was that quake? magnitudes, moments, and energy This quickly shows them that the magnitude of an earthquake is not the only determiner of damage and that anyone who uses magnitudes to talk about damage, clearly does not know much about earthquakes. one in Indonesia, one in Alaska, and one in Kamchatka! I then ask if they think the Needle would survive having one side of its supports moved 100 ft relative to the other side, a typical displacement on a fault producing a M9 quake. If you ride to the top of the Seattle Space Needle, much of the time the elevator operator will state that the needle was "built to withstand a magnitude 9 earthquake." I point out to my classes that the needle has withstood several M9 quakes without damage. Typically this will be shown by someone asking if a particular building will withstand a "magnitude 8" earthquake - and ignoring the distance, duration, hazards other than shaking, and other factors. People often think that magnitude of the earthquake is the only factor that determines damage. Earthquake shaking is typically measured as an acceleration higher magnitude earthquakes cause more violent shaking, which in turn typically cause higher intensity. There is one magnitude for an individual quake, but the intensity varies significantly. Earthquake magnitude is a measurement of the "size" of the quake - typically related to the amount of energy released. ![]() The difference between earthquake magnitude, intensity, and shakingĪsk many seismologists what the most critical and common misunderstanding about earthquakes is and they will answer "the difference between magnitude and intensity." Earthquake intensity and magnitude measure different things and are often misunderstood, and it is shaking that links them.Įarthquake intensity is a measurement of damage.
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