Why aftershocks happen
A large rupture changes stress on nearby faults. Some patches that were close to failing tip over. That produces a cloud of smaller (and occasionally still damaging) events around the mainshock zone.
Decay over time
On average, aftershock rates fall roughly like 1/time after the mainshock (Omori’s law and its variants). “On average” matters: individual days can still be busy, and occasionally a larger aftershock occurs late in the sequence.
How to use the live map
- Open Live Quakes and filter to the week feed after a big event
- Look for spatial clustering near the mainshock (USGS event page helps)
- Remember: empty filters mean “no events matched,” not “safe forever”
Safety
Damaged buildings can fail in aftershocks. Follow local officials. Our site is not a life-safety system.