Earthquake Swarm in the Brawley Seismic Zone

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An 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.