Following the two large earthquakes (ML3.5 and ML4.2) there was a swarm of small earthquakes in that area. The earthquakes where seen on Grímsfjall SIL station, but do not appear to have been strong enough to be recorded on other SIL stations around Vatnajökull glacier. This appears to have lasted until around 13:00 UTC on 13th of January 2011. But after that it did quiet down.
Plot is from IMO web site.
Icelandic Met Office tremor plot that shows the two large earthquakes and following minor earthquakes. This area in Grímsfjall volcano has been quiet since the two earthquakes took place few days ago.