Today (02.09.2012) a harmonic tremor pulse did start in Hamarinn volcano (best guess) (Bárðarbunga volcano). This harmonic tremor pulses are intermittent and normally last for up to 20 to 30 min., at the time. What is creating them is hard to say. But this might just be hydro-thermal activity taking place in Hamarinn volcano. This might also be magma on the move inside Hamarinn volcano. But nothing is confirmed so far. I do not expect anything to be confirmed any time soon.
The harmonic tremor pluses appear on the end of the traces on this image. They are bit hard to spot for the untrained eye. But they appear as higher then background noise change in the tremor plot image.
The harmonic tremor pulse as it appears on the SIL station at Grímsfjall volcano. This is high resolution image from this IMO web page. Copyright of image belongs to Icelandic Meteorological Office.
It is impossible to know what this means exactly. But so far there are no signs of eruption in the area. This activity is less then activity in July 2011 that was created by an minor eruption in Hamarinn volcano. Stronger harmonic tremor pluses appear on SIL station at longer distance. But for now (when active) most of the activity only appears on SIL stations closest to the Vatnajökull glacier. I am going to continue to monitor the current situation. I will update or make a new blog post about what is going on if anything happens.