[Skywise]

M4.5 and vigorous aftershocks in the Geysers area of northern California.

The area is a geothermal field with electric generation plants, thus injection wells. I've heard rumblings of controversy over injection induced seismicity. I'm sure this is going to take those rumblings up a notch.

http://earthquake.usgs.gov/earthquakes/e...76#summary

Brian