The twosome was studying earthquakes to establish a way to measure and compare them. Their finished product was published in the s, called the Richter scale. Richter spent most of his life working at Cal Tech. He became a professor of seismology in He continued researching and teaching simultaneously. He retired in On September 30, Charles Richter died of congestive heart failure at the age of 85 Enotes. The Mercalli scale classified earthquakes from 1 to 12 depending on the amount of damage that occurred to people and buildings.
This scale was subjective to how well constructed buildings had been and how prepared a population was for a natural disaster. Less populated areas had a hard time rating earthquakes USGS. Mercalli Scale created in Pronk Palisades, It is not a physical scale, but rather a mathematical calculation. During an earthquake, he would use a seismograph to record actual earth movement.
In order to calculate this, Richter had to take into account the distance from the epicenter of the earthquake the point on the surface of the Earth directly above the earthquakes starting focus.
He ranked the scale from 1 to 10 and called them magnitudes. An earthquake with a magnitude of 5 would be ten times stronger than a magnitude 4 earthquake. His scale was published in and was quickly adopted by scientists worldwide. Richters Magnitude Scale Pronk Palisades, They paid particular attention to deep earthquakes, ones whose focus was more than miles below the ground.
Earthquakes with the same magnitude can differ in many fundamental ways, including the directions of the vibrations, and their relative amplitude at different periods during the tremblor. These differences can lead to earthquakes with the same magnitude having significantly different levels of destructiveness. Beginning in the mid's, seismologists developed a fairly complete understanding of how a slipping fault generates ground vibrations.
An important quantity that characterizes the strength of the faulting is the seismic moment, the algebraic product of the fault area, the fault slip and the stiffness of the surrounding rock.
Generally speaking, an earthquake with large magnitude corresponds to faulting with a large moment, with an increase in one magnitude unit corresponding to an increase of moment by about a factor of But the relationship is inexact, and many cases occur where small faulting causes an unexpectedly large magnitude earthquake or vice versa.
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See Subscription Options. Go Paperless with Digital. Read more from this special report: An Essential Guide to the U. East Coast Earthquake. Get smart. Sign up for our email newsletter. The Richter Scale is not used to express damage. An earthquake in a densely populated area which results in many deaths and considerable damage may have the same magnitude as a shock in a remote area that does nothing more than frighten the wildlife.
Large-magnitude earthquakes that occur beneath the oceans may not even be felt by humans. How did you become interested in seismology? At Caltech, I was working on my Ph. Robert Millikan. One day he called me into his office and said that the Seismological Laboratory was looking for a physicist; this was not my line, but was I at all interested? I talked with Harry Wood who was in charge of the lab; and, as a result, I joined his staff in What were the origins of the instrumental magnitude scale?
Wood's staff, I was mainly engaged in the routine work of measuring seismograms and locating earthquakes, so that a catalog could be set up of epicenters and times of occurrence. Incidentally, seismology owes a largely unacknowledged debt to the persistent efforts of Harry O.
Wood for bringing about the seismological program in southern California. At the time, Mr. Wood was collaborating with Maxwell Alien on a historical review of earthquakes in California. We were recording on seven widely spaced stations, all with Wood-Anderson torsion seismographs. What modifications were involved in applying the scale to worldwide earthquakes?
Extending the scale to worldwide earthquakes and to recordings on other instruments was begun in in collaboration with Dr. This involved using the reported amplitudes of surface waves with periods of about 20 seconds. Incidentally, the usual designation of the magnitude scale to my name does less than justice to the great part that Dr. Gutenberg played in extending the scale to apply to earthquakes in all parts of the world. Many people have the wrong impression that the Richter magnitude is based on a scale of In a sense, magnitude involves steps of 10 because every increase of one magnitude represents a tenfold amplification of the ground motion.
But there is no scale of 10 in the sense of an upper limit as there is for intensity scales; indeed, I'm glad to see the press now referring to the open-ended Richter scale. Magnitude numbers simply represent measurement from a seismograph record—logarithmic to be sure but with no implied ceiling. The highest magnitudes assigned so far to actual earthquakes are about 9, but that is a limitation in the Earth, not in the scale.
There is another common misapprehension that the magnitude scale is itself some kind of instrument or apparatus. Visitors will frequently ask to "see the scale. No doubt you are often asked about the difference between magnitude and intensity. I like to use the analogy with radio transmissions.
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