The United States Geological Survey recoded a Magnitude 3.0 Earthquake at a depth of 6.7 km in Orange County, California, roughly 40 km east of Los Angeles, at about 1.55 pm local time (about 8.55 am GMT) on Friday 4 October 2013. There are no reports of any damage or injuries arising from this quake, though it was felt as far away as Palmdale, 100 km to the northwest.
The approximate location of the 4 October 2013 Orange County Earthquake. Google Maps.
California is extremely prone to Earthquakes due to the presence of the San Andreas Fault, a tectonic plate margin that effectively bisects the state. The west of California, including Santa Barbara and Los Angeles, is located on the Pacific Plate, and is moving to the northwest. The east of California, including Fresno and Bakersfield is on the North American Plate, and is moving to the southeast. The plates do not move smoothly past one-another, but constantly stick together then break apart as the pressure builds up. This has led to a network of smaller faults that criss-cross the state, so that Earthquakes can effectively occur anywhere.
Witness accounts of Earthquakes can help geologists to understand these events and the underlying structures that cause them. If you felt this quake (or if you were in the area but did not, which is also useful information) then you can report it to the United States Geological Survey here.
See also Magnitude 2.5 Earthquake on the San Diego/Riverside County boundary, southern California, Two Earthquakes in Riverside County, southern California, Magnitude 2.6 Earthquake in Kern County, California, Magnitude 2.5 Earthquake in San Bernardino County, California and Magnitude 3.2 Earthquake in southern California.
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