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.
Nothing is less predictable than the development of an active scientific field.
If one introduces the concept of energy of an earthquake then that is a theoretically derived quantity.
Logarithmic plots are a device of the devil.
My amateur interest in astronomy brought out the term 'magnitude', which is used for the brightness of a star.
I suggested that we might compare earthquakes in terms of the measured amplitudes recorded at these stations, with an appropriate correction for distance.
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.
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.
In every area of the world where there is earthquake risk, there are still many buildings of this type; it is very frustrating to try to get rid of them.
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.
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.'
Refining is inevitable in science when you have made measurements of a phenomenon for a long period of time.
I was lucky because logarithmic plots are a device of the devil.
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.
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.
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