  Earthquake network is known to be of the small-world type. The values of the
network characteristics, however, depend not only on the cell size (i.e., the
scale of coarse graining needed for constructing the network) but also on the
size of a seismic data set. Here, discovery of a scaling law for the clustering
coefficient in terms of the data size, which is refereed to here as finite
data-size scaling, is reported. Its universality is shown to be supported by
the detailed analysis of the data taken from California, Japan and Iran.
Effects of setting threshold of magnitude are also discussed.
