USGS
A magnitude 5.3 earthquake struck off the coast of southern California today, the strongest one to hit the area in several years. The United States Geological Survey puts the earthquake epicenter 17 miles southwest of Santa Cruz Island off southern California.
The earthquake struck today, on April 5th at 12:29 PM local time at a depth of 10 kilometers. Even though the earthquake struck off the coast of California, shaking was felt as far away as Bakersfield, Palmdale and the city of Orange over 100 miles away. The quake's epicenter was 85 miles west of Los Angeles and 41 miles southwest of Ventura. Thankfully, the shaking subsided just as quickly as it came, lasting roughly 10 seconds.
Did You Feel the M5.3 EQ that just took place off the Channel Islands, CA? Please let us know here: https://t.co/cHMIb35SOk pic.twitter.com/qhgXpT166c — USGS (@USGS) April 5, 2018
At this time there are no reports of significant injuries or damage caused by the earthquake, although it is too soon to say for certain. Even though this earthquake was not significant to cause widespread damage, it does increase the likelihood of another, larger earthquake in the near future. In addition, local residents of southern California can expect smaller aftershock earthquakes through today and the coming days. There is no tsunami threat as the earthquake was not powerful enough to create a significant tsunami wave.
Southern California is accustomed to earthquakes, with smaller earthquakes occurring fairly regularly. The Santa Ynez fault, which runs along the northern end of the city is the largest concern for a major earthquake. This fault could produce a powerful earthquake if enough strain is built up over time, causing widespread damage in the Santa Barbara area.
Wikipedia
The location of the earthquake beneath Santa Cruz Island likely occurred due to slippage along the Santa Cruz Island fault. In the image above you'll notice a central running valley across the island, this is the location of the fault line and a surface representation of how it has modified the surrounding geology.
It is a left-reverse fault and about 90 kilometers long. Caltech notes that the fault slip rate is about 0.9 mm per year and that each major rupture occurs on average every 4,000 years. This particular fault has the capability to produce larger earthquakes than the one seen today, up to magnitude 7.5
The Los Angeles Police Department is on alert, they noted on Twitter that they are aware of the earthquake and will monitor all local systems closely. This includes "earthquake mode" which employs crews from the police department and the fire department to survey areas of the city for damage.
Experts predict that an earthquake of this size is typical about once a year in southern California. However, it has been a few years since a comparably sized earthquake was felt in this area. The last one was in 2014 when La Habra earthquake struck as a magnitude 5.1.
USGS
What is certain is that an earthquake of this size is bound to pop up in the near future. However, the continued release of strain on nearby faults through smaller earthquakes is likely a good sign. That could mean there's less chance of a major earthquake.
An earthquake of preliminary magnitude 5.3 struck 38 miles (61 kilometers) off the coast of California Thursday afternoon (April 5), rattling Los Angeles.
That's a moderate quake in the grand scheme of things, and common enough in the region of the San Andreas fault, where LA sits. But the event was still dramatic enough to make people sit up and take notice. Several Twitter users took to the platform to ask if others had felt the quake. [What Causes Earthquakes?]
"This is a very interesting earthquake," Mark Legg, founder of the consulting firm Legg Geophysical, Inc., in Huntington Beach, California, told Live Science, adding that he's been anticipating such an earthquake, as a magnitude-5-plus temblor occurs there about every six years. The last one, a magnitude-6.3, struck in December 2012, he said.
The earthquake occurred near a complex region of several faults called the East Santa Cruz Basin fault zone, Legg said. These fissures in the Pacific Plate are located offshore around the Channel Islands; they were most active during the Miocene epoch (between about 20 million and 5 million years ago), Legg said, though they still produce earthquakes today. That's because they sit snugly on the Pacific Plate, whose motion toward Alaska is impeded by a bend in the San Andreas Fault and the Western Transverse mountain ranges, "which block the smooth northwest movement of the Pacific Plate," Legg said.
(The San Andreas Fault, which marks the boundary between the Pacific and North American tectonic plates, is not a straight line, but rather has lots of bends and other "cricks" along its path.)
Today's earthquake seems to have struck at a spot where a major collision is occurring along a boundary between the Western Transverse Ranges and what is called the California Continental Borderland.
"Sometimes, there are thrust earthquakes along this boundary, other times there are strike-slip earthquakes as the WTR [Western Transverse Ranges] tries to 'escape' around the bend in the San Andreas fault, as the Pacific plate moves to the northwest," Legg wrote in an email.
A thrust-type quake happens when the earth on one side of a fault jumps upward and over the other side; a strike-slip earthquake means both sides of the fault move mostly horizontally, as happens along the San Andreas Fault.
If this all sounds complicated, don't worry, it is.
"I like to think of the southern California region as a major crustal 'Shear Zone' composed of many faults working together (or against each other sometimes) to enable the Pacific Plate to move on its way to Alaska," Legg said. "It is not a simple process, and that is what makes it extremely interesting to scientists like myself and many others.
The LA region experiences an earthquake of this magnitude about once a year,
There's a 1-in-20 chance that today's temblor will be followed by a larger quake in the coming weeks, said John Vidale, director of the Southern California Earthquake Center at USC, as reported by the Los Angeles Times. He added that the more likely scenario involves a series of much smaller aftershocks that may be too weak for anyone to even notice.
"There is a slight chance that this is a foreshock, but as time passes, that probability diminishes rapidly," Legg said.
There are no reports at this time of any significant damage from the quake, and there may not be any in a region well-prepared for temblors.
Earthquake? — christine teigen (@chrissyteigen) April 5, 2018
earthquake!!! — erin ryan (@morninggloria) April 5, 2018
Live Science's Jeanna Bryner contributed reporting to this article.
Editor's Note: This article was updated this evening with more information about the earthquake.
Originally published on Live Science.
The last quake to be felt this widely in the L.A. area was a magnitude 4.4 in Encino in 2014. That quake also shook a wide area and was the largest in the Los Angeles area in four years. It was the strongest to hit directly under the Santa Monica Mountains in the 80 years.
Magnitude 5.3 earthquake off coast of southern California
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CNBC's L.A. Bureau Chief Paul McNamara reports a 5.3 magnitude earthquake off the coast of southern California.
