Both an earthquake swarm and aftershocks are a series of multiple earthquakes happening in a concentrated region. So what is the difference?
What is an Earthquake Swarm?
An earthquake swarm is a series of small earthquake not following a mainshock. A mainshock is the largest earthquake in a sequence of earthquakes that may have foreshocks and/or aftershocks. A swarm is usually a sequence of earthquakes in comparable size that can occur over a number of days or even months. Many swarms are associated with geothermal activity. Aftershocks are part of the “readjustment process” after the main slip on the fault (USGS). As with swarms, aftershocks can continues for days and even up to years after a main earthquake event although the magnitude lessens over time.
What are Aftershocks?
Aftershocks are a series of earthquakes that occur after a mainshock has happened. Aftershocks occur near the fault where the main earthquake occurred. This means there is one large earthquake and a series of smaller earthquakes than can occur before (foreshocks) and/or afterwards (aftershocks).