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There have been five others of a similar magnitude in the Yorkton-Esterhazy area in the past 16 years, and 11 since 1981.
Must be the potash mine given the dates are long before fracking.
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In fact, there is some history of mild quakes near the Esterhazy area -- as many as six small quakes have occurred there since 1990. Geologists believe the most likely cause is heavy potash mining in the area. "It doesn't mean a collapse in the mine or anything that dramatic," Frederiksen said.
"But the presence of mines does change loading conditions and could potentially lead to an earthquake."
Another theory holds the quakes may be triggered when groundwater dissolves salt deposits beneath the Saskatchewan soil.
http://www.winnipegfreepress.com/local/ ... 50924.html