SAN FRANCISCO (KPIX 5) — A swarm of more than 250 small earthquakes since New Year’s Eve near the California-Mexico border is raising concerns among scientists.

The strongest was a magnitude 3.9 underneath the town of Brawley, about 170 miles southeast of Los Angeles, according to the U.S. Geological Survey.

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The quakes struck in the southern end of the Brawley Seismic Zone.

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That’s a seismically active region where tectonic plates are moving away from each other and the earth’s crust is getting stretched out.

Scientists say that area is of concern because it is the region that connects the San Andreas and Imperial faults.

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Both faults can produce devastating earthquakes.