  Scaling analysis of seismicity in the space-time-magnitude domain very often
starts from the relation N(m,L)=a(L)*10**(-bm)*L**c for the rate of seismic
events of magnitude M>m in an area of size L. There are some evidences in favor
of multifractal property of seismic process. In this case the choice of the
scale exponent 'c' is not unique. It is shown how different 'c''s are related
to different types of spatial averaging applied to lambda(m, L) and what are
the 'c''s for which the distributions of a(L) best agree for small L.
Theoretical analysis is supplemented with an analysis of California data for
which the above issues were recently discussed on an empirical level.
