One of the top priorities of researchers in early 1900s was to develop a methodology to analyse and design buildings that are resistant to earthquakes. But how to estimate the earthquake force was a moot point. How to get the accelerogram of ‘the earthquake’ that is likely to occur at a given location? The problem became quite complicated for the following reasons:
(a) Earthquakes do not occur frequently.
(b) Earthquakes cannot be predicted.
(c) It is not possible to instrument each and every possible location to record the earthquake ground motion and maintain these instruments over a period of several decades—24 × 7.
(d) Very meagre database on earthquakes.
(e) An earthquake is a random ...