Earthquake in IL!?

I was awakened at 430ish this morning from a dead sleep when I realized my bed shaking was not in my dream. I jumped from bed not able to comprehend what woke me up "What the heck is that!" I said, and my husband said "It's an earthquake." Having never experienced one in my life, I was quite scared as the house shook, rattled, and a weird hum roared through the house for several seconds. We're all ok and no damange noted yet this morning. We discovered this morning that it was a 5.4 originating south of us about an hour.