For the purpose of this report, a swarm is defined as many earthquakes of the same size occurring in a small volume.
Swarms are especially common in volcanic areas.
Because swarms are such a common and important phenomenon, we undertook a systematic and comprehensive study of swarms at volcanoes using modern commercially available database software. We chose BVE as our primary data source for several reasons. First, it contains data on many swarms that were never reported in the open literature. This is because most papers report eruptions, and swarms are included only if they were associated with eruptions. In other words, the open literature is biased in favor of eruptions, whereas BVE more fully reports a variety of activity during times of no eruptions.