![]() The Richter scale is not very accurate in measuring these larger earthquakes and today scientists use the Moment Magnitude Scale which uses the same logarithmic scale but which more accurately measures the strength of larger earthquakes. The largest earthquake ever recorded was in Chile in 1960, which measured 9.5 on the Richter scale. Earthquakes measuring upwards of 7 are less frequent but very powerful, and can cause a lot of destruction. Earthquakes measuring 1-2 on the scale happen regularly, and they are so small that people cannot feel them. It is logarithmic which means, for example, that an earthquake measuring magnitude 5 is ten times more powerful than an earthquake measuring 4. A Richter scale is normally numbered 1-10, though there is no upper limit. It is measured using a machine called a seismometer which produces a seismograph. The Richter scale measures the magnitude of an earthquake (how powerful it is). Home Page The Science Site contains information on our planet, volcanoes, science projects, earthquakes and much more.A Willmore seismometer measures earthquakesĮarthquakes, until recently, have been measured on the Richter scale. Normal FaultFind out how and why normal faults form.Įarthquake WavesFind out which earthquake waves are produced only by large earthquakes.Įarthquake FactsDid you know that an earthquake can occur any place on Earth? Moment Magnitude ScaleThe moment magnitude scale measures the total energy released by great earthquakes. Richter Magnitude ScaleThe Richter magnitude scale was developed in 1935 to study California earthquakes. More Earthquake Linksġ964 Alaska EarthquakeThe 1964 Alaska quake was the largest earthquake ever recorded in North America. The 2004 Indian Ocean tsunami and earthquake had a moment magnitude between 9.1-9.3. The moment magnitude of the 1964 Alaska earthquake was 9.2. ![]() The 1960 Chile earthquake had a moment magnitude of 9.5. It is considered the costliest earthquake in U.S. It caused an estimated 20 billion in property losses and infrastructure damages. The quake killed 57 people, injured more than 9,000, and displaced over 20,000. Small earthquakes have about the same value on the Richter scale and the moment magnitude scale, so Richter is fine for those. An earthquake with a magnitude of 6.7 struck the southern California city of Northridge in 1994. Scientists used these two sets of information and other data collected in the field to determine the moment magnitude of an earthquake. The moment-magnitude scale is logarithmic, so an increase of one unit means an earthquake is 10 times bigger, with about 30 times the energy produced. The size of the earthquake waves is determined by reading seismograms at reporting stations. The moment magnitude scale includes the area of the fault's rupture and the slippage along the fault to determine the size of the earthquake's moment. What scientists look at to determine magnitude When the rocks fracture slippage can occur along several hundred kilometers of the fault zone during a single event. ![]() Pressure builds in the rocks along the entire length of the subduction zone fault. Great earthquakes occur in subduction zones where a continental plate overrides an oceanic plate and the plates become locked together. For instance, a magnitude 7.0 earthquake releases 1000 times more energy than a magnitude 5.0 earthquake. Seismologists have recently shown that the magnitude of an earthquake is proportional to the energy released by an earthquake. Scientists look at the total energy released by an earthquake to determine its moment magnitude. ![]() The scale has many advantages over other earthquake scales which look at one type of ground motion. ![]() Scientists devised the scale using the moment magnitude after the 1960 Chile earthquake and the 1964 Alaska earthquake. Moment magnitude scale measures great earthquakes Seismologists studying large earthquakes report the size of the earthquake using the moment magnitude. For earthquakes in this range most news reports do not mention which scale has been used to determine the earthquakes magnitude. The Richter and moment magnitude scales have similar magnitudes if the earthquakes are between 3.0 and 7.0. When Richter and moment magnitude scales are used Damage caused by 1960 Chilean earthquake USGS ![]()
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