Using the order parameter of seismicity defined in natural time, we suggest a simple model for the explanation of B?th law, according to which a mainshock differs in magnitude from its largest aftershock by approximately 1.2 regardless of the mainshock magnitude. In addition, the validity of B?th law is studied in the Global Centroid Moment Tensor catalogue by using two different aftershock definitions. It is found that the mean of this difference, when considering all the pairs mainshock-largest aftershock, does not markedly differ from 1.2 and the corresponding distributions do not depend on the mainshock’s magnitude threshold in a statistically significant manner. Finally, the analysis of the cumulative distribution functions provides evidence in favour of the proposed model. Using the order parameter of seismicity defined in natural time, we suggest a simple model for the explanation of B · th law, according to which a mainshock differs in magnitude from its largest aftershock by approximately 1.2 regardless of the mainshock magnitude. validity of B? th law is studied in the Global Centroid Moment Tensor catalog by using two different aftershock definitions. It is found that the mean of this difference, when considering all the pairs mainshock -large aftershock, does not markedly differ from 1.2 and the the distribution distributions do not depend on the mainshock’s magnitude threshold in a maintaining significant manner. Finally, the analysis of the cumulative distribution functions provides evidence in favor of the proposed model.