  The unified scaling law for earthquakes, proposed by Bak, Christensen, Danon
and Scanlon, is shown to hold worldwide, as well as for areas as diverse as
Japan, New Zealand, Spain or New Madrid. The scaling functions that account for
the rescaled recurrence-time probability densities show a power-law behavior
for long times, with a universal exponent about (minus) 2.2. Another decreasing
power law governs short times, but with an exponent that may change from one
area to another. This is in contrast with a spatially independent,
time-homogenized version of Bak et al's procedure, which seems to present a
universal scaling behavior.
