Even before small eruptions there's alot of seismic activity. But, the area this is happening in sees these swarms over the decades. They have been recording them there since the 30's. I was in the 1989 Loma Prieta and saw the Cyprus super structure go out of my kitchen window while I was trying to make it out of my home. I could barely stand up straight and at the moment it seemed like the world was ending.
They have been expecting a volcanic eruption of some kind from Brawly county north to Yosemite for a century now. Early explorers and the local indians have always said SoCal shakes alot even before Hollywood and all the parties.
Earthquake Swarm in the Brawley Seismic Zone
August 27, 2012An energetic earthquake swarm (largest event magnitude 5.5) is ongoing in the Brawley Seismic Zone south of the Salton Sea in Southern California. The swarm started on Saturday August 25 with earthquake activity on a northeast striking fault zone located about 20 km (12.5 miles) south of the young volcanic center known as Salton Buttes. The most recent eruptions, which took place about 9,000 years ago, produced five rhyolite lava domes along the present-day shore of the southern Salton Sea. The Brawley Seismic Zone, located between the northern end of the Imperial Fault and the southern end of the San Andreas Fault is a tectonically active area, with numerous earthquake swarms occurring over the last several decades, most recently in 2005 and in 1981. There is no evidence to suggest the present swarm is volcanic in nature.
More information on the Brawley swarm can be found on the website of the Southern California Seismic Network (a partnership of Caltech and the USGS) at
http://www.scsn.org/. Visit the Salton Buttes page to learn more about the Salton Buttes volcanic area. This sight does some intersting mapping of the Brawley swarm.
I still know people who were in the 89 quake who turn white when even a 3.0 rolls through while we are together. You can see them holding their breath waiting for it to stop because there is no place to run. We were all used to the regular 3.0-4.0 tremblers through the year, year after year. The big one in the SF Bay 89, then the one in LA 94 came out of the blue.
These SoCal swarms in the south eastern CA volcanic region are expected about every 10 years becasue of a magma chamber about 4 miles down below the Long Valley Caldera. It's part of why an eruption was thought to be ready to take place at Mammoth mountain some years back with the CO2 leak. The 92 Big Bear lake earthquake made people think the big one was happening and others thought a volcano was waking up.
