Ask A Scientist General Science Archive

Author:     Eric Peterson
Text:       What is the exact difference between an earthquake and an 
aftershock, especially in that they are not always centered at the same point 
on the fault, and there may be several months between the original quake and 
the aftershock.  (Reference recent California aftershock at Big Bear 6 months 
after original quake centered almost 100 miles south)

Reply #:  1 of 1
Author:   Sam Bowen
Subject:  Aftershocks vs. Earthquakes
Text:     I doubt if there is a precise definition.  If some shaking occurs 
after a bigger one in the same fault, the tendency is to call it an after 
shock.  In fact, the earlier episode could be an after shock of a much earlier 
episode and therefore should have been called an after shock also.  It is a 
useful distinction for the shocks that are close in time to each other, but it 
is not rigorously precise.