Richter scale when was it invented

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. It applies in seismology because seismographs, or the receivers, record the waves of elastic disturbance, or radio waves, that are radiated from the earthquake source, or the broadcasting station.

Magnitude can be compared to the power output in kilowatts of a broadcasting station. Local intensity on the Mercalli scale is then comparable to the signal strength on a receiver at a given locality; in effect, the quality of the signal. Intensity like signal strength will generally fall off with distance from the source, although it also depends on the local conditions and the pathway from the source to the point.

There has been interest recently in reassessing what is meant by the "size of an earthquake. Our original intent was to define magnitude strictly in terms of instrumental observations. If one introduces the concept of "energy of an earthquake" then that is a theoretically derived quantity. If the assumptions used in calculating energy are changed, then this seriously affects the final result, even though the same body of data might be used.

So we tried to keep the interpretation of the "size of the earthquake" as closely tied to the actual instrument observations involved as possible. What emerged, of course, was that the magnitude scale presupposed that all earthquakes were alike except for a constant scaling factor.

And this proved to be closer to the truth than we expected. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors.

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Richter then went on to devise correction tables that allowed magnitudes to be calculated regardless of the actual distance of the earthquake from the seismometer. The appeal of the Richter magnitude scale is twofold. First, an earthquake is summarized by an easy-to-remember and easy-to-interpret single-digit number. A magnitude 3 is a tiny earthquake. A magnitude 6 is one that can cause substantial damage. A magnitude 9, like the one that caused December's deadly Indian Ocean tsunami, is capable of causing severe devastation.

Second, the magnitude can easily be determined from measurements made by a seismometer, which need not be located particularly close to the fault. Indeed, modern seismometers can record earthquakes of magnitude 5 and above occurring anywhere in the world. The downside to the Richter scale is that magnitude is a single number, which cannot fully characterize a complicated phenomenon such as an earthquake. 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. Already a subscriber?

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