The data from the earthquake monitors is pretty useless if we don't know how to analyse it. The tremor levels are very low, especially those closest to the Katla volcano. If you go and look at earthquake maps of other places in Iceland you'll see that minor quakes happen there all the time. Actually, the volcanic eruption probably obscured a lot of these quakes in the background tremor. What's more, these recent earthquakes around Katla have high error factors on them and are at very shallow depth. The Icelandics don't seem too concerned!