A critique of the ICOLD method for selecting earthquake ground motions to design large dams

The practice for selection of earthquake ground motion for design of large dams as recommended by the International Committee on Large Dams (ICOLD) bulletin 72 is examined. It is shown that the recommended practice is flawed and does not bear a scrutiny on the basis of statistical theory. The ground motion attenuation relationships are derived on the basis of different sets of assumptions and different sets of data, and with different standard errors. Estimates from these different attenuation relationships cannot be averaged (weighted, or otherwise) as recommended in the bulletin due to the presence of standard errors for each of these relationships.