What is the Richter Scale?
A scale for determining the size of an earthquake from the recording of earthquake waves made on a seismograph. The maximum height of the visible recording is adjusted for the distance from the instrument to the earthquake. This is not a physical scale (in other words, one cannot look at or hold the “Richter Scale”). Each 1-unit increase in the Richter Scale roughly corresponds to a 30-fold increase in energy release and a 10-fold increase in ground motion at any site. The Richter magnitude is the number generally reported in the press, and in principle the value should be the same at all recording locations (though natural variations and the use of diverse scales may lead to reported numbers that slightly differ). Due to the earth’s physical limitations, the largest earthquakes have Richter magnitudes in the upper 8 range. Magnitude Energy released (millions of ergs) Energy equivalence -2 600 100 watt light bulb left on for a week -1 20000 Smallest earthquake detected at Parkfield, CA
The Richter Scale was developed by Charles Richter in 1935 at the California Institute of Technolgy. It was the first reliable way of comparing the size of earthquakes. The method used a specific type of seismometer common for the time and was done by measuring the physical size of the seismogram traces. Then using other information, such as the distance from the quake, the information was put into a simple formula and a magnitude number was derived. This scale is logarithmic, meaning that a one point increase in magnitude corresponded to approximately a 32 times increase in energy. The Richter Scale is no longer in use, mainly due to the fact that it was calibrated to a specific type of seismograph (which is no longer used) and was also calibrated to the crustal conditions of southern California, making it less accurate for other parts of the globe. Many seismologists today cringe when the media continues to say that a particular earthquake was a given size “on the Richter Scale.” See
