Earthquakes rattle Southern California
Experimental early warning system gave 4-second advanced notice
USGS map of recent Southern California earthquakes.
A series of earthquakes shook Southern California between Los Angeles and Orange counties Friday night. Reports of the shaking have come in from residents throughout Southern California. There have been no reports of major damage or injuries.
A 5.1-magnitude at 9:09 p.m. was the strongest of four temblors, according the US Geological Survey. Three other medium quakes and several smaller ones rolled in around the main quake, including a 3.6-magnitude at 8:39 p.m., a 3.4-magnitude at 9:11 p.m. and a 3.6-magnitude at 9:30 p.m.
There have been 38 aftershocks as of 10:45 p.m. The aftershock sequence may continue for several days to weeks, but will likely decay in frequency and magnitude as time goes by, according to USGS.
The epicenter of the main tremor was 1 mile east of La Habra, Calif. about 20 miles east of downtown Los Angeles and about four miles deep in the earth’s crust.
An experimental earthquake early warning system provided a four second warning in Pasadena, about 30 miles away from the epicenter, USGS reports.
This sequence could be associated with the Puente Hills thrust (PHT), according to USGS. The PHT is a blind thrust fault that extends from this region to the north and west towards the City of Los Angeles. It caused the 5.9-magnitude 1987 Oct. 1 Whittier Narrows earthquake. Previously, the 5.4-magnitude 2008 Chino Hills earthquake occurred in this region. It caused somewhat stronger shaking in Orange County and across the Los Angeles Basin.
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