Seismic event in northwest suburbs wasn't earthquake, researchers say

CHICAGO (CBS) -- Did you feel a rumble in the northwestern suburbs Sunday night? You aren't alone.

More than 200 people in Lake and McHenry counties reported feeling an earthquake on Sunday. Some reported hearing unusually loud thunder, and feeling their homes shake.

Researchers at Northwestern University said, while they are confident it wasn't an earthquake, they aren't quite sure what caused it, saying they recorded a "sequence of interesting signals" at their seismic station in Lake County.