During the night (22-July-2013) a minor earthquake swarm took place in Katla volcano. Most of the earthquakes where shallow, with the depth of 1 km, one earthquake had the depth of 12 km. This earthquake swarm took place in the central area of the caldera. I am not sure what did create this earthquake swarm, it might have been a dike intrusion, or it simply might just be a pressure changes in hydro-thermal areas in this location.
This earthquake swarm is probably just part of normal summer activity in Katla volcano, at least there is nothing that suggests otherwise at present time. It is possible to watch the activity in Katla volcano here from my geophone at Skeiðflöt farm, just outside Katla volcano.