Great Lakes tectonic zone southern Ontario. Several earthquakes have been documented in Minnesota in the last 120 years, with at least six in the GLTZ. The epicenters show a clear relationship to tectonic features of the state; four epicenters lie along the Great Lakes tectonic zone. Depths are estimated at . The best-documented event occurred on July 9, 1975, near Morris, Minnesota, with a magnitude of 4.6, and a felt area of covering parts of four states. Wisconsin has had no earthquakes along the GLTZ, Michigan's Upper Peninsula has had four earthquakes in the vicinity of the GLTZ – Negaunee, Newberry and two in
Great Lakes Airlines (Canada) 440 propliners and Convair 580 turboprops, were older and subject to vibrations during take-off, resulting in passengers nicknaming the company "Great Shakes". Convair 580 turboprops operated by Air Ontario prompted the nickname "Scare Ontario". Great Lakes Airlines was serving the following destinations in Ontario province in Canada with scheduled passenger flights operated with Convair aircraft in 1979: Great Lakes Airlines (Canada) Great Lakes Airlines was a regional airline in Canada. It was formed in 1958 in Sarnia, Ontario by John Blunt and by 1983 became Air Ontario Ltd. In June 1987 Air Ontario Ltd. merged with Austin Airways to form