It seems that since the late 1990's, Clear Lake (also called The Geysers Geothermal Field) in northern California, ongoing shallow quakes have plagued the region now for almost two decades. This first fascinated me as I was looking at the USGS real time quake maps on their website, and once I plugged in the real time KMZ file into Google Earth, it's been interesting to watch ever since.
Information on this ongoing quake swarm is a bit hard to come by. It seems that the longer this goes on, the less people are interested in this area of seismicity, so I thought I might "stoke the fire" a bit and get people to pay some attention to this.
The Clear Lake volcano has not had any historical eruptions, but the area is an active volcano. The landscape is dotted with cinder cones, maars (explosion craters), geothermal geysers, and lava domes. The area last erupted around 10,000 years ago, and has been anything but quiet ever since. Much like the geysers at Yellowstone, The Geysers Geothermal Field gets its heat source from a large silicic magma chamber that provides the heat source for one of the worlds largest geothermal power plants.
Locals state that these quakes are a direct result of water injection into the hot rock, which can lubricate fault lines, cause stress fractures in the rocks, and very rarely, lead to phreatic eruptions (gas and steam). This has not occurred at Clear Lake.
My fascination with this area is that it seems these quakes are a tad bit too large to be "merely" the result of geothermal drilling. Some quakes have ranged up to 5.0, while for the most part, you get 1.0-3.0 quakes daily in the region. This suggests to me that either human activities related to the power generators have destabilized some of the mountain regions around the lake, or seismic activity is related somehow to ongoing volcanic activity.
As this has been a consistent swarm for about two decades, there is no need to worry about any eruption in the near future, but my concern is that the area is not being studied by any publication-posting geologists. You would think that a swarm of this duration would be something of interest to geologists, but if you try to search for information, most of it is extremely old.
There have been lawsuits brought by locals who wish the plant to be shut down, so it could be they hired some lobbyists to quiet the USGS, or any freelance scientists. There's simply no way to tell without some deep investigations.
In any case, the below picture was taken today showing the location of these quake swarms. As you can see, there are a lot, and a daily scan of the area just reveals more and more. I'd personally love it if the area was surveyed by an agency not tied to the geothermal power plant for an objective view.