Sorry, I haven't seen the full article, but it was mentioned in a news summary.

Not all earthquakes are the result of movement along geological faults. Some small quakes were attributed to the filling of Lake Mead. I waas surprised to learn that Minnesota had experienced recentearthquakes. It had nothing to do with faults (that part of the continent is extremely stable) but was attributed to crustal unloading as the Pleistocene glaciers melted.