What is Earthquake swarm?

In seismology, an earthquake swarm is a sequence of seismic events occurring in a local area within a relatively short period of time. The length of time used to define a swarm varies, but may be days, months, or years. Such an energy release is different from the situation when a major earthquake is followed by a series of aftershocks: in earthquake swarms, no single earthquake in the sequence is obviously the main shock. In particular, a cluster of aftershocks occurring after a mainshock is not a swarm.