Here are few harmonic tremor charts from the Grímsfjall volcano / Grímsvatn eruption. It can clearly be seen where the eruption looses strength for an few hours. It is also clear when the eruption starts to regain it’s eruption strength again.
The volcanic tremor is best seen on 0.5 – 1Hz band, alongside 1 – 5Hz bands.
All pictures are from Icelandic Met Office web page. Copyright of this pictures belongs to them.