  It is well accepted that, at the global scale, the Gutenberg-Richter (GR) law
describing the distribution of earthquake magnitude or seismic moment has to be
modified at the tail to properly account for the most extreme events. It is
debated, though, how much additional time of earthquake recording will be
necessary to properly constrain this tail. Using the global CMT catalog, we
study how three modifications of the GR law that incorporate a corner-value
parameter are compatible with the size of the largest observed earthquake in a
given time window. Current data lead to a rather large range of parameter
values (e.g., corner magnitude from 8.6 to 10.2 for the so-called tapered GR
distribution). Updating this estimation in the future will strongly depend on
the maximum magnitude observed, but, under reasonable assumptions, the range
will be substantially reduced by the end of this century, contrary to claims in
previous literature.
