A shallow earthquake that struck the Westwood area Sunday evening was upgraded to magnitude 4.2, the U.S. Geological Survey said.
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The temblor, initially reported as magnitude 3.8, hit at 7:36 p.m. about 4 miles west-northwest of Westwood, the USGS said. There were no immediate reports of injuries, damage or power outages.
"It was a pretty big rattle," said Yuri Thomas, who was in Westwood when he felt shaking.
The Los Angeles Fire Department went into earthquake mode, sending firefighters from all 106 stations across the city to check for damage. About an hour later, the LAFD said no damage had been found.
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Scientists said the quake may have been an aftershock of a magnitude-4.4 temblor that struck west Los Angeles in March. They later determined that the epicenter of Sunday's quake was too far away for the two events to be connected.
"The new location is deeper, so farther away from the stations. To create the same signal farther away, it must be bigger," tweeted Dr. Lucy Jones.
NBC4 viewers reported feeling the shaking in various locations, including Pacific Palisades, Sherman Oaks, Tarzana, Santa Monica, Simi Valley and Panorama City.
In 72 years leading up to 2013, the Los Angeles basin had 36 earthquakes of magnitude 4 or greater, Jones tweeted. So far in 2014, there have been three.
Jones said the region may be entering a more active seismic period.