Ninety-two strong-motion earthquake records from
the California region, U.S.A., have been statistically
studied using principal component analysis in terms of twelve
important standardized strong-motion characteristics. The
first two principal components account for about 57 per cent
of the total variance. Based on these two components the
earthquake records are classified into nine groups in a
two-dimensional principal component plane. Also a
unidimensional engineering rating scale is proposed. The
procedure can be used as an objective approach for
classifying and rating future earthquakes
