Within the last few days, there have been several large (2.0-4.0) and very shallow (2km-1km) quakes hitting the Lavic Lake/Amboy Crater region in Southern California. While the area does lie on a tectonic fault position near the San Andreas faultline, the placement and depth of the quakes could very well mean that magma is on the move, and quite near the surface. The quakes are clustered in a very concentrated area, and are very near to past volcanic activity such as Lavic Lake, Amboy Crater, and more in the region. The mountains near the quake center are very old volcanoes, so it would not be entirely surprising if indeed there was dike intrusion or magma movement near the surface... definitely something to keep an eye on!
Below is an image from Google Earth, with the real time USGS Quake overlay.
You can see pretty clearly here that these are shallow, strong quakes. While this could easily be purely tectonic in nature, it is worrisome that these quakes are so very near to past volcanism in the region, and the quakes certainly line up between Amboy and Lavic Lake.
I'll update this post should anything new develop. In the meantime, this area is not populated, save for some military operations, and is probably not a danger to any major city. So there is no real reason for panic or concern. If an eruption does occur in this area, it will likely be nothing more than scientifically and historically interesting. Nothing like the movie "Volcano" where one erupted in the middle of Los Angeles!
Other interesting seismicity in California that piques my interest is the ongoing earthquake swarms in the Geysers Geothermal Field in Northern California on the edge of the Clear Lake volcanic field. Research indicates these quakes are most likely a result of geothermal development in the area (this being one of the largest geothermal plants in the world), and more than likely has nothing to do with magma movement. Scientists theorize that Clear Lake contains an old silicic magma chamber, detached from the mantle, that is slowly cooling, but provides plenty of renewable thermal energy to power the plants. Locals have complained that it makes the region highly unstable, and new drilling has ceased.
Also in California, the Ubehebe Craters area has shown in the last week that it is also seismically active, with many small quakes occurring just under one of the eastern cones in the field. This area last erupted around 6000 years ago, with layers of tephra covering some ancient native American artifacts. But as Chaiten volcano in Chile demonstrated in 2008, and Nabro volcano in Eritrea (which is an ongoing eruption last I checked!), long dormant volcanoes can easily wake up given the right circumstances. Indeed, this was witnessed recently, and in the 1940's when a volcano in Mexico grew out of a farmer's cornfield to become the Paricutin volcano in the Michoacan-Guanajuato volcanic field.
If indeed the activity near Lavic Lake does result in a volcanic eruption, the event will likely be quite similar to the Paricutin eruption, producing a monogenetic volcanic cinder cone not unlike Amboy or the vents at Lavic Lake. This means that an eruption, if it does occur, will produce one or two cones, and probably never erupt again in the same spot, as monogenetic cinder cones do not repeat their eruptive cycles due to the nature of the magma pocket that briefly feeds them.
Stay tuned, and stay alert!