  Distant regional cross correlations are analyzed for seismicity in Japan by
making use of the theory of random matrices as the null hypothesis. The
empirical correlation matrix is shown to strongly deviate from the random
matrix of the Wishart type. Accordingly, nonuniversal (i.e., nonrandom)
correlations are identified and are represented by the networks on the map of
Japan. The effect of setting threshold for magnitude is also examined, and it
is found that the threshodling alters the results only slightly.
