Aftershock Probabilities

Normally, earthquakes between magnitude 2.0 and 3.0 can be felt near the epicenter but cause no damage. Earthquakes between magnitude 3.0 and 5.0 are more widely felt and can cause minor damage near the epicenter, while magnitude above 6.0 can cause more severe damage to buildings.

What to expect during and after an earthquake


The earthquake of greatest magnitude in a series of earthquakes which occur over a relatively short period of time in a particular area.


Additional earthquakes that occur after the mainshock and in the same geographic area. Usually an aftershock is smaller than the mainshock, but occasionally an aftershock may be strong enough to be felt widely throughout the area and may cause additional damage, particularly to structures already weakened in the mainshock.


An earthquake which occurs immediately preceeding a mainshock in the exact same area in which the mainshock occurs.

If you've felt an earthquake:

  • Email the Weston Observatory at or call at 617-552-8300 to tell us precisely when and where you felt the earthquake.
  • Notify the U.S. Geological Survey by filling out a form at "Did You Feel It?"
  • If there is damage, call the Mass. Emergency Management Agency at 508-820-2000.