![]() ![]() Therefore, the Richter scale has been replaced by the moment magnitude scale, symbolized as M w. The Richter magnitude scale was found to not transfer very well from the San Andreas fault zone, a transform plate boundary, to the much more powerful earthquakes that occur at convergent plate boundaries, particularly subduction zone earthquakes. There is no upper limit defined for the Richter scale, but after a century of seismograph measurements, it appears that rocks in the earth release their stress before building up enough energy to reach magnitude 10. The distance to the epicenter must also be taken into account because the greater the distance from the earthquake, the smaller the waves get. The effect of distance is factored out of the calculation. The maximum amplitude seismic wave – the height of the tallest one – is measured in mm on a seismogram. Two measurements are factored together to determine the Richter magnitude of an earthquake: the amplitude of the largest waves recorded on a seismogram of the earthquake, and the distance to the epicenter of the earthquake. Richter used seismograms of earthquakes that occurred in the San Andreas fault zone to calibrate his magnitude scale. For several decades, earthquake magnitudes were calculated based on a method first developed by Charles Richter, a seismologist based in California. The magnitude of an earthquake is a number that allows earthquakes to be compared with each other in terms of their relative power. Intensity is determined from effects on people, human structures, and the natural environment. ![]() Intensity measures the strength of shaking produced by the earthquake at a certain location. Magnitude is determined from measurements on seismographs. Magnitude measures the energy released at the source of the earthquake. Magnitude and Intensity measure different characteristics of earthquakes. The following video explains the difference between scales: Most seismologists now use the moment magnitude scale. The moment magnitude scale more accurately reflects the energy released and the damage caused. ![]() Which scale do you think is best? With the Richter scale, a single sharp jolt measures higher than a very long intense earthquake that releases more energy. How does an increase in two integers on the moment magnitude scale compare in terms of the amount of energy released? Two integers equals a 900-fold increase in released energy. The amplitude of the largest seismic wave of a magnitude 5 quake is 10 times that of a magnitude 4 quake and 100 times that of a magnitude 3 quake. How does the amplitude of the largest seismic wave of a magnitude 5 earthquake compare with the largest wave of a magnitude 4 earthquake? How does it compare with a magnitude 3 quake?
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