[buccaneer81]

Do you mind telling me what a “swarm” is?

Many small quakes occurring in a short period of time.

[FromLori]

More than 1,200 tiny quakes hit Yellowstone Park

http://www.missoulian.com/news/state-and-regional/article_9db5e032-0a22-11df-95bc-001cc4c002e0.html