Body-Wave Magnitude mb Is a Good Proxy of Moment Magnitude Mw for Small Earthquakes (mb<4:5 –5 :0)

Body-wave magnitude mb is usually considered a poor proxy of moment magnitude Mw because it saturates for moderate and large earthquakes (Mw >5.5–6) and generally shows a poor correlation with Mw. On the other hand, the observed distribution of data at the global scale also seems to indicate an inverse saturation at low magnitudes (Mw <4.5–5.0) in which Mw appears to be almost uncorrelated with mb. We show here that the latter is an artifact of the incompleteness of the global Mw datasets for Mw <4.5–5.0 and that disappears considering lower Mw estimates available from regional centroid moment tensor (CMT) catalogs and/or using general orthogonal regression methods. In these cases we show that mb well corresponds to Mw <4.5–5.0 and hence can confidently be used for approximating the Mw of small earthquakes.