”Įxplainer thanks Paul Bodin and Gary Patterson of the University of Memphis. Instead the common shorthand is to describe an earthquake as being a “magnitude. Although the two scales may use different methods, they should end up producing virtually the same number.Many news organizations have dropped the “Richter” but not adopted the phrase “moment magnitude” scale. It is also possible to compare earthquakes using the new scale to those measured in the past on the Richter scale. Because the Richter scale had become so commonly understood, they devised a method to convert the information from the seismic moment into a scale comparable to Richter’s, or what’s now known as the moment magnitude scale. With the creation of more sophisticated seismology equipment in the 1970s, scientists could determine the actual area where the rupture in the fault took place and measure how much energy was released there during the earthquake, a calculation they call the seismic moment. Scientists wanted a measurement that was universally applicable. For another, although the Richter scale was revised to be used to measure earthquakes in other parts of the world, it had limitations since it was based on conditions in California. They wanted to get a physical snapshot of how much energy was released when a fault slipped. But scientists wanted something that measured an earthquake not just in comparative terms, but in absolute terms. For one, it is a relative measure that is, it was developed to compare the size of one earthquake to another.
As effective a tool as the Richter scale is, it has some drawbacks. The way the scale works, each whole number increase, say from 4.8 to 5.8 to 6.8, represents a 10-fold increase in the size of the ground motion.
Richter, who worked in southern California, using data from seismographs–which measure earth movement–devised a method to calculate where an earthquake began, or its epicenter, and its magnitude. The Richter scale was developed by seismologist Charles Richter (1900-1985) in the 1930s to bring consistent, objective criteria to evaluating the size of earthquakes. While the Richter scale is not obsolete, the universal measurement today is the moment magnitude scale. Is the Richter scale obsolete, and what is used instead? They can travel around the whole earth from large earthquakes many times before they become too small to record on seismographs.The Seattle earthquake registered 6.8 on the … well, not on the Richter scale, which the New York Times reported has been displaced. Surface waves travel around the surface layers of the earth and are the slowest of the earthquake waves.However, they cannot travel through liquids because liquids have no shear strength. Their side-to-side motion (like a snake wriggling) is what causes the most damage to structures. They pack a bigger punch because they are bigger and move at right angles to the direction of travel. For example, a magnitude of 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. S-waves are secondary waves and are the second waves to arrive, traveling at 2.5–4 km/sec (9000–14,000 km/h). On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions.They do not generally cause a lot of damage except in the biggest earthquakes. They are also called sound or compression waves since they are often heard rather than felt. P-waves are primary waves and are the first waves to arrive.An earthquake produces three kinds of waves that travel through the Earth’s crust.
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