Comment on ‘Magnitude conversion problem using general orthogonal regression’ by H. R. Wason, Ranjit Das and M. L. Sharma, (Geophys. J. Int., 190, 1091–1096)

Abstract

The argument proposed by Wason et al. that the conversion of magnitudes from a scale (e.g. Ms or mb) to another (e.g. Mw), using the coefficients computed by the general orthogonal regression method (Fuller) is biased if the observed values of the predictor (independent) variable are used in the equation as well as the methodology they suggest to estimate the supposedly true values of the predictor variable are wrong for a number of theoretical and empirical reasons. Hence, we advise against the use of such methodology for magnitude conversions.