As seismologists gained more experience from earthquake records, it became obvious that the problem could not be reduced to a single peak acceleration. In fact, a full frequency of vibrations occurs.
Emphasis was usually put on the horizontal acceleration factor, for the simple reason that ordinary structures have a built-in safety factor for the vertical component; that is, gravity.
I repeatedly have to correct this belief. 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.
I usually point out that most loss of life and property has been due to the collapse of antiquated and unsafe structures, mostly of brick and other masonry.
This is very similar to astronomy where different magnitudes are assigned to the brightness of an astronomical object, depending on the range of wavelengths being measured.
My amateur interest in astronomy brought out the term 'magnitude', which is used for the brightness of a star.
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.
I suggested that we might compare earthquakes in terms of the measured amplitudes recorded at these stations, with an appropriate correction for distance.
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.
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.
We would have been happy if we could have assigned just three categories, large, medium, and small; the point is, we wanted to avoid personal judgments. It actually turned out to be quite a finely tuned scale.
For example, some stars put out large amounts of energy in the infrared part of the spectrum, so that this can produce a different relative magnitude rating than using light energy from the middle of the spectrum.
Refining is inevitable in science when you have made measurements of a phenomenon for a long period of time.
I'm glad to see the press now referring to the open-ended Richter scale.
Don't wait for extraordinary circumstance to do good; try to use ordinary situations.
Logarithmic plots are a device of the devil.
I was lucky because logarithmic plots are a device of the devil.
If one introduces the concept of energy of an earthquake then that is a theoretically derived quantity.
By moving them vertically, a representative mean curve could be formed, and individual events were then characterized by individual logarithmic differences from the standard curve.
