Intel is (supposedly) going to build a giant semiconductor fab in Ohio, and one of the reasons was "very low seismic activity".
Well, compared to California...
Re microquakes and Intel, at one point I was operating a delicate vacuum gauge which relied on the slowing down of a spinning ball suspended magnetically in the vacuum. It was called "the spinning rotor gauge" and was touted by NBS/NIST as a possible new transfer standard for measuring ultra high vacuums.
Seemed like almost every day the damned thing would give crazily impossible results around three o'clock-ish. It took a while before I realized that this was due to a coal train rumbling by about half a mile from the lab building at about that time-ish every day-ish. The apparatus would vibrate slightly, while the rotor ball would tend to stay in the same place by some Newtonian law or another, and would therefore yield the crazy readings.
The -ishes explain why it took so long to figure it out.
Oh, those damned intervening variables!
Terry, 230RN
NOTE Many semiconductor MFRing operations are under vacuum.