In the past few hours an interesting harmonic signals have been taking place on two sil stations (so far) around Vatnajökull glacier. I do not know what is creating this harmonic tremor spikes on them, it might be water on the move or starting to move from Skaftár cauldron in Vatnajökull glacier or it might be something different that I do not know about at present time. Currently the source of this harmonic tremor is unknown and it might never been known in the worst case. I do hope to figure out in next few hours what is creating this harmonic tremor spikes on this two sil stations.
The harmonic tremor signal at Skrokkalda sil station. The harmonic tremor signal can be found at the end of the tremor plot. Copyright of this image belongs to Icelandic Meteorological Office.
The harmonic tremor signal at Jökulsel sil station. It is at the end of the tremor plot. Copyright of this image belongs to Icelandic Meteorological Office.
As I say above, the source of this tremor signal is not known. It might be bad weather in the area, traffic (unlikely due to bad weather in this part of Iceland at the moment) or something that is not known at the moment. What I can rule out at the moment is this harmonic tremor signal does not appear to come from magma movement, the frequency of the harmonic tremor is too high for that at the moment and does not show little to no energy at 0.5 to 1 Hz band. This suggest the source is something else then magma, this however does not rule out magma. Since magma is known to due many strange things under pressure and high frequency harmonic tremors are not unknown, but they are unlikely to take place rather than being a common feature in volcano activity.
For the moment the best thing that can be done is to monitor the signal and see if there are any changes and on the nearby sil stations. For the moment I do not expect any major change in this area, risk of glacier flood is still in place for this part of Vatnajökull glacier. If this harmonic tremor signal connects to that is not known at the moment.