What are multiple small earthquakes called?

Answer 1

Names used include tremor, temblor, and seism. A "microseism" is a faint tremor caused by any of several sources (earthquake, avalanche, large waves, explosions).

Colloquial terms for minor quakes are shakes, rumbles, or bumps.

Answer 2

Multiple small earthquakes that occur in a sequence are often referred to as a swarm. These swarms can sometimes precede a larger mainshock event.

Answer 3

Lots of small earthquakes clustering around an area with no identifiable mainshock is called an 'earthquake swarm'.