  In this study we address the question of the minimum sample size needed for
distinguishing between Gutenberg-Richter distributions with varying b-values at
different resolutions. In order to account for both the complete and incomplete
parts of a catalog we use the recently introduced angular frequency magnitude
distribution (FMD). Unlike the gradually curved FMD, the angular FMD is fully
compatible with Aki's maximum likelihood method for b-value estimation. To
obtain generic results we conduct our analysis on synthetic catalogs with Monte
Carlo methods. Our results indicate that the minimum sample size used in many
studies is strictly below the value required for detecting significant
variations.
