Magnitude 2.8 earthquake hits near Vernon

A magnitude 2.8 earthquake struck near Vernon about 9:22 a.m., according to the U.S. Geological Survey.

The earthquake was centered two miles north of Vernon and 2 miles southwest of East Los Angeles.

Several people in southeast Los Angeles County reported feeling the earthquake, according to "Did You Feel It?" responses on the USGS website. A couple of people in Long Beach and South Pasadena also reported feeling it.

ALSO:

Lindsay Lohan on Twitter: 'I'm taking this seriously'

Prescription drug deaths: Bill would tighten rules on hydrocodone

Sheriff probes snafu that sent reputed gang members to wrong court

-- Kimi Yoshino

Image: A map of the earthquake that struck near Vernon. Credit: USGS

4.6-magnitude earthquake shakes Northern California awake

A 4.6-magnitude earthquake rattled Northern California overnight Thursday, shaking residents from San Francisco to north of Sacramento.

The temblor struck at 2:09 a.m. and was centered in Geyserville, about 20 miles north of Santa Rosa, according to the U.S. Geological Survey. USGS measurements indicated at least 20 smaller earthquakes followed throughout the morning.

The Santa Rosa Press Democrat reported the quake began only one mile below ground level, which is why it was felt across the region. There were no immediate reports of damage, the newspaper said.

But it woke people up. More than 60 people reported to USGS's "Did you feel it?" site, with reports ranging from San Francisco and Oakland to Lake and Yuba counties.

Others reported the shaking on Twitter. Some of those messages are included below.

Earthquake early-warning system's future still in doubt

Supporters of California's quake early warning system hope this week's success will prompt state officials to help fund completion of the network.

The system currently is being funded as a pilot program, largely by private donations as a temporary project.

Scientists and some lawmakers have called for the state to pay to make the system permanent.

Backers want the state to spend $80 million to install and upgrade thousands of the sensors across California. If they can get the money, seismologists said the system could be operational in two years.

Without the funding, the future of the system is unclear.

Monday's 4.7 temblor in Anza marked a big advance for the system.

The quake struck in the desert town of Anza, about 35 miles south of Palm Springs, and hundreds of sensors embedded in the ground immediately sent an alert to seismologists at Caltech in Pasadena. They had 30 seconds' warning before the quake was felt there.

"It was right," said Kate Hutton, a Caltech seismologist. "I sat really still to see if I could feel it and it worked."

4.6 earthquake shakes Northern California

A magnitude 4.6 earthquake struck Northern California on Thursday morning,

The temblor struck about 26 miles north of Santa Rosa in the Geysers area. There were no reports of damage or injuries, but there were some apparent aftershocks.

It was felt over a wide area of the region, including in Santa Rosa, Marin County and Vallejo, according to the U.S. Geological Survey.

The "Do You Feel It?" survey by the USGS showed people as far south a San Francisco felt shaking.

ALSO:

Still no verdict in Bell corruption trial; jurors on Day 13

Rapist held in mental hospital must be tried or freed, court says

Drunk driver killed brother, faces manslaughter charges, D.A. says

--Shelby Grad

Image: USGS

L.A. Now Live: Monday's earthquake tested early warning system

Monday's earthquake in Riverside County offered scientists one of their first opportunities to match data from an earthquake early warning pilot program to what they could actually feel.

According to Caltech and U.S. Geological Survey seismologists, the test was a success. The Monday morning 4.7-magnitude temblor gave Caltech scientists a 30-second warning ahead of the shaking.

Though the quake didn't cause any damage, researchers say even a few seconds of notice can prove vital for shutting down utilities, slowing trains and giving people time to prepare.

Reporter Joseph Serna will join us at 9 a.m. to discuss how the pilot program works and how far away it is from being introduced to the public.

Earthquake early warning system passes major test with quake

In the seismic annals of California, Monday’s 4.7 earthquake was little more than a footnote. It gave Southern California a small morning jolt but caused no damage and was largely shrugged off by noon.

But in one important way, the quake was highly significant because it marked an advance in California’s burgeoning earthquake early warning system.

The quake struck in the desert town of Anza, and hundreds of sensors embedded in the ground immediately sent an alert to seismologists at Caltech in Pasadena. They had 30 seconds warning before the quake was felt there.

“It was right,” said Kate Hutton, a seismologist with Caltech. “I sat really still to see if I could feel it and it worked.”

The system has been in place for more than a year. But Monday’s quake offered a rare opportunity to actually see – and feel -- if it worked.

The sensor have warned scientists of numerous quakes, but the vast majority were either too small to feel or too far away to be felt in the Los Angeles area. For example, the sensor gave an early warning of several magnitude 5 quakes last year in Imperial County, but the temblors hit too far away for them to felt in Los Angeles.

The Anza quake was different.

Even though it measured magnitude 4.7, its location on solid granite made the shaking stronger and more widespread. People reported to the USGS that they felt it as far away as Arizona and Central California. At Caltech, computer screens flashed with a 30-second countdown to when the shaking would hit Pasadena. Sure enough, it came on time.

Hutton and other declared the test a success, with some caveats.

The system initially overestimated the quake’s magnitude, saying it was a 5.2. But U.S. Geological Survey seismologist Susan Hough was not overly concerned about the error. She noted that the main job of the system is to alert people to a coming quake, not to gets its magnitude precisely right. The Anza quake caused an unusually intense amount of shaking, Hough added, so the warning system accurately captured that.

The early earthquake warning system is a pilot project for what scientists hope will eventually be a statewide network using thousands of sensors to notify people about imminent shaking from moderate to strong earthquakes.

Earthquake early-warning system successful during Monday quake

An earthquake early warning system being tested in California gave seismologists in Pasadena up to 30 seconds to prepare for Monday morning’s temblor in the desert of Riverside County.

“It was right,” said Kate Hutton, a seismologist with Caltech. “I sat really still to see if I could feel it and it worked.”

The Early Earthquake Warning project, a test run of a proposed statewide program that would use thousands of sensors already in place to notify people about imminent shaking from moderate to strong earthquakes, alerted Caltech scientists about a 4.7 temblor in Anza.

In the moments leading up to an earthquake, even a few seconds can make a difference, seismologists say.

An early warning would give utilities time to shut down, trains a chance to slow so they don’t derail and workers a chance to move away from hazardous materials or precarious positions.

The system that warned Hutton on Monday morning was part of a beta-test for an early warning program proposed by state Sen. Alex Padilla (D-Pacoima) earlier this year.

Researchers have relied on about $400,000 annually to develop technology for the system. A $6-million grant in 2011 from the Palo Alto-based Gordon and Betty Moore Foundation injected more life into the project, but experts estimate upgrading monitors and sensors across California – there are thousands of them – would cost up to $80 million.

Southern California earthquake points to danger of fault line

This post has been corrected. See the note below.

Some might believe that the 4.7 magnitude Riverside County temblor that rattled windows and swayed skyscrapers across Southern California on Monday morning released tension from the San Jacinto fault, thereby avoiding danger of a larger earthquake.

But according to a study published in January in the journal Nature, conventional wisdom is wrong.

A pair of researchers, one from Caltech and the other from the Japan Agency for Marine-Earth Science and Technology, concluded that stick-slip faults similar to the San Jacinto fault that ruptured Monday aren’t limited to frequent, smaller temblors.

The authors pointed to the 2011 Fukushima earthquake in Japan. That quake, a 9.0, was born from a stick-slip fault that unexpectedly ruptured with devastating consequences.

Before that disaster, seismologists believed earthquake faults that experienced “creep,” or small, gradual movement throughout the year, had little chance of massive ruptures. The San Jacinto fault, Hutton said Tuesday, is one of those creeping faults.

“It does have frequent, small earthquakes but it does have big ones every now and then,” she said. “It doesn’t make it any safer.”

The San Jacinto fault is similar, with tectonic plates that slide horizontally against each other. Monday’s tremor was the biggest in three years and was felt across a wider swath than typical West Coast earthquakes, Susan Hough of the U.S. Geological Survey told the Los Angeles Times on Monday.

Scientists said the finding is forcing seismologists to rethink faults worldwide. A quake from San Francisco to San Diego along the San Andreas fault now seems more plausible, the study’s authors wrote.

For the Record, 3:52 p.m. March 12: An earlier version of this post incorrectly identified Susan Hough as Sarah Hough.

ALSO:

Bell corruption trial: Illness forces jurors to be sent home

California earthquake: Hundreds of aftershocks, more expected

Four arrested after motorcycle marriage proposal on 10 Freeway

-- Joseph Serna

Image: San Jacinto fault zone. Credit: USGS

California earthquake: Hundreds of aftershocks, more expected

The magnitude 4.7 earthquake in Riverside County on Monday has produced hundreds of aftershocks, and experts said that trend should continue for several days.

There have been about 250 aftershocks Tuesday, and there were more than 200 on Monday. All were small and probably not felt by residents in the Anza area.

“I think in a week or so they should be back to normal but that’s still fairly high for that area,” said Kate Hutton, a seismologist at Caltech.

Monday morning's quake, centered near Anza, caused no major damage, but it was felt over what seismologists said was an unusually large area.

The quake was initially recorded as three separate quakes because a foreshock tricked seismographs into recording multiple quakes of multiple sizes, said Susan Hough, a seismologist at the U.S. Geological Survey.

Earthquakes of a magnitude 4.7 are typically felt only about 120 miles away from the epicenter, but Monday morning's quake traveled farther. The USGS said it was felt as far away as Arizona. The temblor also shook coffee cups in Los Angeles. 

That's because the quake occurred in the San Jacinto Mountains, which are composed of hard granite rock that transmits energy more efficiently, Hough said.

The quake occurred along the San Jacinto fault zone, which runs through San Bernardino, San Diego, Riverside and Imperial counties, roughly parallel to the San Andreas fault. It's one of three fault zones that absorb friction from the motion of the North American continent and the Pacific plates rubbing against each other.

“It's capable of generating moderate to large earthquakes,” USGS seismologist Robert Graves said Monday. “Today's activity was not out of the ordinary. Actually, it's pretty typical of the area.”

There is some evidence that the largest quake in the fault zone, a magnitude 7, occurred sometime in the early 1800s, Graves said.

California earthquake a reminder of seismic dangers

Monday morning's magnitude 4.7 earthquake in Riverside County hit is a seismically active area, and experts said it was a reminder of the potential dangers.

“It's a good idea to take it to heart and make sure you're prepared,” U.S. Geological Survey Seismologist Robert Graves said. “We live in Southern California, and we have lots of active faults; and every once in a while, it's large enough to cause damage.”

Here are four graphics from the USGS that tell the story of Monday's earthquake:

The USGS said the quake was felt as far away as Arizona and the Central Valley. Here's a map showing where people responded to the USGS's "Did You Feel It?" website:

The USGS got more than 9,000 responses from the public. The chart shows when the responses were sent:

This map shows the shaking intensity of the Monday temblor:

The star shows the location of the quake with other historic quakes in the area plotted with orange circles.

 

 

 

 

 

 

The quake was initially recorded as three separate quakes because a foreshock tricked seismographs into recording multiple quakes of multiple sizes, said Susan Hough, a USGS seismologist.

Earthquakes of a 4.7 magnitude are typically only felt about 120 miles from the epicenter, but Monday morning's quake traveled farther.

That's because the quake occurred in the San Jacinto Mountains, which are composed of hard granite that transmits energy more efficiently, Hough said.

The quake occurred along the San Jacinto Fault Zone, which runs through San Bernardino, San Diego, Riverside and Imperial counties roughly parallel to the San Andreas Fault. It's one of three fault zones that absorb friction from the motion of the North American Continent and the Pacific plates rubbing against each other.

“It's capable of generating moderate to large earthquakes,” said Graves. “Today's activity was not out of the ordinary. Actually, it's pretty typical of the area.”

There is some evidence that the largest quake ever recorded in the fault zone, a magnitude 7, occurred in the early 1800s, Graves said.

No injuries or major damage was reported.

ALSO

Southern California earthquake: More than 100 aftershocks

Convicted rapist Andrew Luster's 124-year sentence vacated

Dorner case: Women shot by cops still don't have truck promised by LAPD

--Frank Shyong and Joseph Serna

Map at left: The San Jacinto fault zone. Credit: USGS