Yup, saw that. It seemed a little off the smooth curve of the other ones. There is a huge natural gas field in the northern Netherlands (Groningen). They have to be careful how the produce it, because if they let pressures fall much the sediment compacts and being the Netherlands (low lands), that would lead to subsidence and flooding.

The Rhine graben cuts across southern Netherlands. The Rhine graben has had much larger quakes (Germany, Switzerland also).

So, Penny, do you think there is some wave-like mysterious triggering going on, or just a coincidence?

Chris