I can say with absolute certainty: Every unusual spot of earthquake action in the Mid-west is due to some well operator taking a chance on injecting gas frack waste. He can inject other stuff all day long, but then gets tempted by the riches.
So, this little town is getting some fame and excitement. They won't be happy too long, if they continue to inject and say "What?". Eventually, they stop and nobody is the wiser. It has happened in every state so far. They have to send these stuff to OK, where the earthquakes are slowly picking up again.