A homogeneous estimate of moment magnitude () for small‐to‐moderate‐magnitude (SMM) earthquakes is important to assess regional ground‐motion attenuation and seismic hazard. Multiple estimates of for SMM events are often available from regional agencies. These estimates are typically biased compared with the estimates from a global agency due to limited geographic or azimuthal convergence. The of SMM earthquakes near the border between Japan and Taiwan is available from both the Broadband Array in Taiwan for Seismology and the Full Range Seismograph Network of Japan for . The provided by these agencies is compared with that by the Global Centroid Moment Tensor for to estimate the bias and standard deviation of the values. An optimum data fusion of these s is presented to obtain a homogeneous estimation of for SMM earthquakes () near the border between Japan and Taiwan.