Saturday's earthquake that shook much of Michigan took many by surprise.

\"It did rock me off my left foot, and onto my right,\" said Dot Rifenbark, a Bay County resident.

But even the experts are scratching their heads on this one.

\"Earthquakes with an epicenter if Michigan are fairly rare,\" said Larry Ruff, a seismologist with the University of Michigan.

Ruff said Michiganders sometimes feel the effects of quakes in other states, like the earthquake that rocked the nation's capital in 2011.

But Saturday's was the strongest in nearly seven decades to strike the Great Lakes state.

\"There was an earthquake that occurred in the vicinity of Coldwater, Michigan, back in 1947, with a magnitude of approximately 4.5,\" said Ruff. \"But it was strongly felt in the entire Lansing area.\"

But what caused the earthquake this weekend, and why did it happen now? Do experts have an answer?

\"The short answer is no, we do not,\" said Ruff. \"And that makes it both interesting, scientifically, and to the general public as well to speculate on that.\"

With the recent earthquake overseas , Rifenbark said her interest in the quake is heightened, too.

\"We had been watching the earthquake news over in India and Nepal just this past week, so we were focused on that,\" she said.

But for now, the speculation will continue, about the surprise Saturday shake.

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