ACKNOWLEDGMENTS

Equation 6 for the contribution to the variance of the pre-dicted random component of ground motion due to compo-nent-to-component variation is in error by a factor of 2. The proper equation is ()2 a2- 1,~s ln ~ j- ln Y2 j c nrecs j=l 4 (6) The same erroneous equation appears as Equation 3 in Boore et al. (1993). As a result of the error, the column labeled "O'c" in Table 8 is too large by a factor of x/-2, and the error carries through to the columns labeled "o r ' and "C51nr The cor-rected Table 8 is included here, with an added column giving the ratio of the corrected and erroneous values of the total standard eviation of the predicted value of the random com-ponent of ground motion (O'lnY; for brevity the column in the table is labeled "n/o " for "new " divided by "old"). Because the component-to-component variance is smaller than the vari-ance of the geometric mean (compare columns "O-c " and "Crl"), and because variances are added to obtain the total variance, the impact of the error on the total standard evia-tion is minor. (The ratios of the standard eviation of the ran-dom-component ground motion to the geometric-mean ground motion, sometimes used in seismic hazard calcula-tions, differ by amounts almost identical to the "n/o " column in the table included in this erratum. For example, at 1-sec period the ratio is 1.18 and 1.09 for the erroneous and cor-rected values of cy C, respectively, with a ratio of the ratio equal to 0.92.) The error also propagated to two Spudich et al. paper