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A swarm of more than 250 small earthquakes has
struck since New Year’s Eve near the California-Mexico border, causing unease
among residents and attention from scientists.
By Strange Sounds - Jan 3, 2017
The earthquakes struck in the southern end of
the Brawley Seismic Zone, a seismically active region where tectonic plates are
moving away from each other and the Earth’s crust is getting stretched out “and
basically adding land,” said Caltech seismologist Egill Hauksson.
The Brawley Seismic Zone is particularly
important to watch because it is the region that connects the San
Andreas and Imperial faults, both of which can produce damaging earthquakes. The
seismic zone extends for about 30 miles from the city of Brawley, across the
Salton Sea’s southern half, and ends near Bombay Beach.
The Brawley Seismic
Zone, which stretches between Brawley to an area near Bombay Beach, is
important to watch because it is a region that connects the San Andreas and
Imperial faults, which can produce major earthquakes.
The southern Brawley Seismic Zone is close in
proximity to the Imperial fault. The Imperial fault has caused two major
earthquakes in recent decades.
In 1979, a magnitude-6.5 earthquake sent
violent shaking into El Centro, injuring 91 and causing so much damage to the
concrete Imperial County Services Building that it had to be demolished.
The magnitude-7.1 earthquake that hit El Centro
in 1940 claimed nine lives and swayed buildings as far away as Los Angeles.
Irrigation systems were damaged, and railroad tracks were left warped where
they crossed the fault.
Earthquake swarms that occur in the other end
of the Brawley Seismic Zone — to the north — could trigger a major event on the
San Andreas fault, one of California’s most dangerous, that could send
catastrophic shaking into Riverside, San Bernardino and Los Angeles counties.
More than 250
earthquakes have rattled the Brawley Seismic Zone near the California-Mexico
border since December 31, 2016 and it is not stopping.
In late September, one such swarm began in the
northern Brawley Seismic Zone, with three measuring above magnitude 4. That
event led the U.S. Geological Survey to warn that chances of a magnitude 7 or
greater earthquake on the San Andreas fault had risen as a result of the swarm.
Another swarm of small earthquakes, topping out
at magnitude 3.5, struck the town of Niland near the eastern shore of
the Salton Sea on Halloween.
Brawley Mayor Sam Couchman said the earthquakes
have placed the city of 26,000 on edge since Saturday afternoon.
“We’re just kind of listening to it, and
when you can hear it coming, it’ll rattle things. Last night, we had the rain,
the earthquakes, and the fireworks. All we needed were frogs and locusts.”
Source : http://strangesounds.org
