According to conventional earthquake wisdom, aftershocks represent the ground's "relaxing" after the main temblor has rattled the land. But researchers in Britain report that, statistically speaking, aftershocks are no different from main shocks.
Physicists Per Bak, Kim Christensen, Leon Danon and Tim Scanlon of Imperial College London mapped more than 330,000 earthquakes that struck California between 1984 and 2000. They found that all the quakes obeyed a single underlying scaling law, a mathematical relation that gives the statistical spread of events for a given area and magnitude. According to this law, earthquakes cluster in the same way at a range of timescales, from tens of seconds to tens of years. So from a wide enough perspective, an aftershock could come years after a primary event.
This article was originally published with the title Scaling the Quakes.