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.
Logarithmic plots are a device of the devil.
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.
A good deal of my consulting work consists of site analysis for proposed developments. The problem of assessing seismic risk starts at the geological-geophysical end and winds up at the engineering end.
I was lucky because logarithmic plots are a device of the devil.
I suggested that we might compare earthquakes in terms of the measured amplitudes recorded at these stations, with an appropriate correction for distance.
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.
Refining is inevitable in science when you have made measurements of a phenomenon for a long period of time.
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.
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.
I saw that I could now rank the earthquakes one above the other. Also, quite unexpectedly the attenuation curves were roughly parallel on the plot.
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.
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.
We have a given site, and we have to ascertain what disturbances will affect the structures on that site as a result of an earthquake.
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.'
I'm glad to see the press now referring to the open-ended Richter scale.
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.
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.
These are usually described in the form of a design earthquake with a time history of the motion and shaking characteristics that are 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.
So we tried to keep the interpretation of the 'size of the earthquake' as closely tied to the actual instrument observations involved as possible.
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.
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.
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.
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.
From here, it becomes an engineering problem; the engineer considers the ground motion that will occur and evaluates the requirements of the proposed structure in the light of the local foundation conditions.
According to Democritus, truth lies at the bottom of a well, the water of which serves as a mirror in which objects may be reflected. I have heard, however, that some philosophers, in seeking for truth, to pay homage to her, have seen their own image and adored it instead.
At least there is progress of California toward building new construction according to earthquake-resistant design. We would have less reason to ask for earthquake prediction if this was universal.
My amateur interest in astronomy brought out the term 'magnitude,' which is used for the brightness of a star.
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