The group of earthquakes marked by the green box seem to be an earthquake swarm, since they are grouped together both spatially and temporally. Although there have been earthquakes in this area during 7 of the last 29 years, there is a significant spike in the number of earthquakes in 1981,indicating the time of the swarm. This increase in earthquakes may be the result of increased magmatic or hydrothermal activity.

To contrast what appears to be a true earthquake swarm, I isolated a group of earthquakes in the NE corner of the map that appear to have no close spatial relations. The histogram of events per year shows that there is no real temporal relationship between earthquakes in this area. In otherwords, the distributions of earthquakes through time appears random. This indicates that seismic activity in this area is probably more related to distibuted stresses in and around the caldera and volcanic system, rather than associated with a discrete event like magma moving upwards through the crust (and breaking the rock causing earthquakes) or as an aftershock sequence, etc.