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.

If one introduces the concept of energy of an earthquake then that is a theoretically derived quantity.

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.

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.

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.

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.