a = 10 0.414M – 1.696 km Dobrovolsky et al., 1989  = 10 0.43M km Dobrovolsky et al., 1979 l(M 0 ) = exp(M 0 – c) + 2  Keilis-Borok and Kossobokov, 1990  = 10 A E 1/2 Bowman et al., 1998 Magnitude3456789 Earthquake preparation zone radius  (km) 19.552.5141380102227547413