In this study, we investigate the relationship between topological and seismological parameters of earthquake sequences generated by the Olami-Feder-Christensen (OFC) [Olami et al., Phys. Rev. Lett. 68(8), 1244 (1992)] spring-block model and converted in undirected graphs by using the visibility graph method [Lacasa et al., Proc. Natl. Acad. Sci. U.S.A. 105(13), 4972-4975 (2008)]. In particular, we study the relationship between the Gutenberg-Richter b-value and the so-called K-M slope, which describes the relationship between magnitudes and connectivity degrees. This relationship was found to follow a rather universal law in observational earthquake sequences, and, thus, in the present work, we aim at verifying such universality also in earthquake sequences generated by the OFC spring-block model. We found that for ⟨b⟩ between approximately 1 and 2, which is nearly the range of variation for most of the real seismicity cases observed worldwide, the relationship between ⟨b⟩ and ⟨K-M slope⟩ does not depend on the lattice size L. Furthermore, the slope of the regression line between ⟨b⟩ and ⟨K-M slope⟩ in the range of ⟨b⟩ between 1 and 2 changes with the definition of magnitude and the length of the earthquake sequence.