To realize what forces are affecting the earthquake zone of Reykjanes, a 3D model can be useful. The convection rolls below interact with the basic tectonic drift. Layer A has direct contact with the ductile part of the tectonic plate. Layer B has a certain degree of coupling effect with layer A, also affecting the tectonic plate. The ductile part is twisted as a result, turning anti-clockwise. Therefore, the polygon forms a rupture along the NS-axis from one corner to the other. This leads to the fact that the brittle part above may be affected by the twisting effect from below at different points of time at each side of the NS-axis.
The convection rolls are nearly perpendicular to each other. Drawn to scale. The coupling effect between layers leads to different pressure and tectonic drift directions, besides earthquakes.
The relevant earthquake swarm is shown in the previous post.