The earthquakes within Tjörnes Fracture Zone are aligned paralell to the convection rolls of polar system.
This can be compared with the convection rolls map:
https://www.vedur.is/skjalftar-og-eldgos/jardskjalftar/tjornesbrot_stort/
The earthquakes started mainly within the First Polygon, but then spread northwards along the central NS-axis of the Second Polygon shown on the picture above.
Also, it is interesting to see how the earthquakes spread north of Skagafjörður, the old volcanic zone, which has been volcanically extinct for a few hundred thousand years, but is still seismically and geothermally active.
