ABSTRACT
The word ' intensity ' may be defined qualitatively as ' the quality or condi t ion of being intense ' or quanti tat ively as 'magni tude , as of energy or a force per uni t of area or t ime' . The te rm ear thquake intensity was in t roduced to be a physical quant i ty , bu t th rough quali tat ive or fuzzy definitions. In the ea r thquake engineering field, some consider it a qual i ta tive ra t ing th rough the intensity scale, bu t many engineers consider it an equivalent of g round peak acceleration. F o r example, in Japan , the term ' intensity ' (or shinto in Japanese) is used for the ra t io of peak ground accelerat ion to tha t of gravity, or a/g, and at the same time in the term ' intensity (shinto) scale' . In this b o o k it will be used only for its quali tat ive definition, as accepted by most seismologists and engineers, and R o m a n numera ls are used; if it has to be used as a quant i ta t ive term, quo ta t ion marks will be added.
