Seismological Research Letters
 © 2005 by the Seismological Society of America
Equation 6 for the contribution to the variance of the predicted random component of ground motion due to componenttocomponent variation is in error by a factor of 2. The proper equation is (6) The same erroneous equation appears as Equation 3 in Boore et al. (1993). As a result of the error, the column labeled “σ_{C}” in Table 8 is too large by a factor of , and the error carries through to the columns labeled “σ_{r}” and “σ_{lnY}.” The corrected Table 8 is included here, with an added column giving the ratio of the corrected and erroneous values of the total standard deviation of the predicted value of the random component of ground motion (σ_{lnY}; for brevity the column in the table is labeled “n/o” for “new” divided by “old”). Because the componenttocomponent variance is smaller than the variance of the geometric mean (compare columns “σ_{C}” and “σ_{1}”), and because variances are added to obtain the total variance, the impact of the error on the total standard deviation is minor. (The ratios of the standard deviation of the randomcomponent ground motion to the geometricmean ground motion, sometimes used in seismic hazard calculations, differ by amounts almost identical to the “n/o” column in the table included in this erratum. For example, at 1sec period the ratio is 1.18 and 1.09 for the erroneous and corrected values of σ_{C}, respectively, with a ratio of the ratio equal to 0.92.)
The error also propagated to two Spudich et al. papers (1997, 1999). The σ3 values in Table 3 of Spudich et al. (1997) and Table 2 of Spudich et al. (1999) are too large by a factor of .
Acknowledgments
I thank Julian Bommer and Fleur Strasser for pointing out the error in Equation 6.
Footnotes

Seismological Research Letters, Vol. 68, No. 1, pp. 128153, January/February 1997