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Sunday, August 24, 2014

( The USGS Earthquake Report ) Patcnews Aug 24, 2014 The Patriot Conservative News Tea Party Network Reports 6.0 Magnitude Earthquake Hits Northern California © All copyrights reserved By Patcnews






















Earthquakes in the Brawley seismic zone as of the evening of 09/30/2016.
An earthquake swarm near Bombay Beach, California, started on Sept. 26, 2016, in the Brawley Seismic Zone, which lies near the southern terminus of the San Andreas Fault.
The swarm includes 96 earthquakes above magnitude 2 so far (as of 12:00 pm PDT on Sept. 30, 2016). Relocations of these events show that they are occurring in the depth range 4 to 9 km. The largest of these events were two M4.3 earthquakes and a M4.1 earthquake on Sept. 26.
The earthquakes are occurring near a set of north-northeast trending cross-faults beneath the Salton Sea. The cross-faults are part of a fault network that connect the southernmost end of the San Andreas Fault with the Imperial Fault. Some of the cross-faults are oriented such that they add stress to the San Andreas Fault and the San Jacinto Fault system when they rupture in small earthquakes like those in the ongoing swarm.
Swarm-like activity in this region has occurred in the past, so this week’s activity, in and of itself, is not necessarily cause for alarm.
Preliminary calculations indicate that, as of 12:00 pm (PDT) on Sept. 30, 2016, there is 0.006% to 0.2% chance (less than 1 in 10,000 to 1 in 500) of a magnitude 7 or greater earthquake being triggered on the Southern San Andreas Fault within the next seven days through October 7, with the likelihood decreasing over time. This range is estimated using several models developed in California to assess foreshock/aftershock probabilities, and the lower bound is about equal to the average chance of a magnitude 7 earthquake occurring on the Southern San Andreas Fault in any given week.
These revised probabilities are lower than those made earlier this week, due to decreasing swarm activity. The probabilities may change if the swarm activity increases or decreases.

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Risk of big earthquake on San Andreas fault rises after quake swarm at Salton Sea



The rumbling started Monday morning deep under the Salton Sea. A rapid succession of small earthquakes — three measuring above magnitude 4.0 — began rupturing near Bombay Beach, continuing for more than 24 hours. Before the swarm started to fade, more than 200 earthquakes had been recorded.
The temblors were not felt over a very large area, but they have garnered intense interest — and concern — among seismologists. It marked only the third time since earthquake sensors were installed there in 1932 that the area had seen such a swarm, and this one had more earthquakes than the events of 2001 and 2009.
The quakes occurred in one of California’s most seismically complex areas. They hit in a seismic zone just south of where the mighty San Andreas fault ends. It is composed of a web of faults that scientists fear could one day wake up the nearby San Andreas from its long slumber.


 The San Andreas fault’s southernmost stretch has not ruptured since about 1680 — more than 330 years ago, scientists estimate. And a big earthquake happens on average in this area once every 150 or 200 years, so experts think the region is long overdue for a major quake.


The swarm actually increased the likelihood of a much more major quake in Southern California, at least temporarily.
According to the U.S. Geological Survey, as of Tuesday, the chances of a magnitude 7 or greater earthquake being triggered on the southern San Andreas fault over the next seven days were as high as 1 in 100 and as low as 1 in 3,000. Without the swarm, the average chance for such an earthquake striking on any given week is 1 in 6,000.  
“Any time there is significant seismic activity in the vicinity of the San Andreas fault, we seismologists get nervous,” said Thomas H. Jordan, director of the Southern California Earthquake Center, “because we recognize that the probability of having a large earthquake goes up.”
As seismic activity drops, the probability of having a large earthquake also decreases.

Experts said it’s important to understand that the chance of the swarm triggering a big one, while small, was real. 
“This is close enough to be in that worry zone,” seismologist Lucy Jones said of the location of the earthquake swarm. “It’s a part of California that the seismologists all watch.”
The swarm began just after 4 a.m. Monday, starting earthquakes three to seven miles deep underneath the Salton Sea.

The biggest earthquakes hit later that morning, a 4.3, and then a pair later at night, another 4.3 followed by a 4.1. There was another burst of activity Tuesday night.
The earthquakes hit in a sparsely populated area, less than four miles from Bombay Beach, population 171, sitting on the edge of the Sonoran Desert. When swarms hit this area — the northern edge of the so-called Brawley Seismic Zone — it’s enough to give earthquake experts heartburn. And there’s reason for that.
Just 12 hours after a 6.3 earthquake hit south of the Salton Sea in 1987, an even larger temblor, a 6.6, ruptured six miles away — the Superstition Hills earthquake.

No deaths were reported from the earthquake in this sparsely populated area, but it did suggest how an earthquake on one fault could add stress on another fault.
The San Andreas fault is even closer to where Monday’s earthquake swarm hit — less than four miles away.
“When there’s significant seismicity in this area of the fault, we kind of wonder if it is somehow going to go active,” said Caltech seismologist Egill Hauksson. “So maybe one of those small earthquakes that’s happening in the neighborhood of the fault is going to trigger it, and set off the big event.”

And that could set the first domino off on the San Andreas fault, unzipping the fault from Imperial County through Los Angeles County, spreading devastating shaking waves throughout the southern half of California in a monster 7.8 earthquake.
“The southern San Andreas is actually seismically fairly quiet. It doesn’t really make noise. So to have something right next to the main strand making a little noise — you have to pay attention to how it might be transferring stress onto the main strand of the fault,” said USGS research geologist Kate Scharer.
And the problem with the southern San Andreas fault — the stretch from Monterey County to the Salton Sea — is that when it goes, it’s probably going to go big, such as with a magnitude 7 or higher quake, Scharer said.

The San Andreas is also thought to be smoother than other faults, making it easier for an earthquake to keep plowing ahead into a longer, more powerful rupture, rather than ending as a smaller event, Hauksson said.
There have been other earthquakes in past decades that have raised fears among scientists that they could wake the sleeping San Andreas.
One of the biggest concerns came in 1992, when the magnitude 7.3 Landers earthquake struck the Mojave Desert.

That sparked aftershocks, including the magnitude 6.5 earthquake in Big Bear three hours later, and involved faults that were close to the San Andreas.

“We were at a high level of concern then,” Jones said. “And that lasted through the aftershock sequence through the next year, because the aftershocks were coming down and hitting the San Andreas.”
A San Andreas earthquake starting at the Salton Sea has long been a major concern for scientists. In 2008, USGS researchers simulated what would happen if a magnitude 7.8 earthquake started at the Salton Sea and then barreled up the San Andreas fault, sending shaking waves out in all directions.

By the time the San Andreas fault becomes unhinged in San Bernardino County’s Cajon Pass, Interstate 15 and rail lines could be severed. Historic downtowns in the Inland Empire could be awash in fallen brick, crushing people under the weight of collapsed buildings that had never been retrofitted.
Los Angeles could feel shaking for a minute — a lifetime compared with the seven seconds felt during the 1994 Northridge earthquake. Shaking waves may reach as far as Bakersfield, Oxnard and Santa Barbara. About 1,600 fires could spread across Southern California. And powerful aftershocks larger than magnitude 7 could pulverize the region, sending shaking into San Diego County and into the San Gabriel Valley.
The ShakeOut simulation says it’s possible that hundreds of brick and concrete buildings could fall, and even a few fairly new high-rise steel buildings. The death toll could climb to 1,800 people, and such an earthquake could cause 50,000 injuries and $200 billion in damage.

ron.lin@latimes.com
Twitter: @ronlin
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 The Los Angeles Times











Rong-Gong Lin II

San Andreas fault 'locked, loaded and ready to roll' with big earthquake, expert says.

Southern California’s section of the San Andreas fault is “locked, loaded and ready to roll,” a leading earthquake scientist said Wednesday at the National Earthquake Conference in Long Beach.

The San Andreas fault is one of California’s most dangerous, and is the state’s longest fault. Yet for Southern California, the last big earthquake to strike the southern San Andreas was in 1857, when a magnitude 7.9 earthquake ruptured an astonishing 185 miles between Monterey County and the San Gabriel Mountains near Los Angeles.
It has been quiet since then — too quiet, said Thomas Jordan, director of the Southern California Earthquake Center.

 

Northern California rocked by magnitude 6.0 earthquake



A magnitude 6.0 earthquake hit Northern California near Napa Valley Sunday, injuring at least 120 — 3 critically — and causing extensive damage, including fires sparked by burst gas lines, in the largest tremor to rock the Bay Area since the magnitude 6.9 Loma Prieta quake in 1989.
Leslie Gordon of the U.S. Geological Survey says the tremor struck just before 3:30 a.m. Sunday local time, about 10 miles northwest of American Canyon, which is about 6 miles southwest of Napa.
The city of Napa said in a statement Sunday that two adults and one child have critical injuries, and Queen of the Valley hospital in Napa reported treating 120 people. Hospital spokeswoman Vanessa DeGier says most patients have cuts, bumps and bruises.
Three people were admitted with broken bones and two for heart attacks, according to The Associated Press.
Napa City Manager Mike Parness said the city declared a local emergency at 8:59 a.m. California time, which is the first step in getting more help from the state.
Parness said during a news conference Sunday evening that about 11,000-14,000 households of 80,000 in the quake zone were without power and that authorities hoped to have all power restored by Monday.
Mark Ghilarducci, director of the California Governor's Office of Emergency Services, said
about 90 to 100 homes were deemed not habitable. He said the next step was to continue damage assessments and get a cost estimate for potential federal assistance.
Officials said they were still assessing buildings in the area.
A Red Cross evacuation center was set up at a high school, and crews were assessing damage to homes and roadways.
Authorities said Sunday evening that all bridges responded well to the earthquake.
John Callahan of the Napa City Fire Department said at one point Sunday there were a half-dozen multiple structure fires. One was at a mobile home park where four mobile homes have been destroyed by fire, and two others suffered major damage.
Public Works Director Jack LaRochelle assured residents the water has not been contaminated.
“The water is safe to drink,” he said. LaRochelle said that more than 60 water mains have been damaged; 20 have been turned off. He said none of the larger transmission lines had been damaged.
Napa Fire Chief Mike Randolph said firefighters were continuing to assess the damage to buildings in the downtown area, and the department was busy answering more than 100 calls reporting the smell of natural gas. That's "our primary attention right now," he said.
A number of buildings are damaged during the quake, but no number on how many was reported.
The city’s 911 emergency call system was maxed out, according to Napa Police Department operations captain Steve Potter, but he said there have been no reports of major disturbances. “We have relative calm for this magnitude of an earthquake,” he said.
Jennifer Jones Lee, who lives in the earthquake area, told Fox News the tremor “felt like someone just picked up the house, shook it for a while, then dropped it. It was incredibly violent.”
Arik Housley, who owns two grocery stores in the area, said he was awakened at about 3:30 a.m. by the shaking. “It was very jolting and probably went for 20 seconds . . . it was shaking pretty good,” said Housley, whose brother is Fox News senior correspondent Adam Housley.
Arik Housley said he passed a mobile home park where multiple fires could be seen as he drove to one of his stores to assess the damage. Housley said the shelving in his store had moved 2 feet to 3 feet from the wall, and much of his inventory had fallen to the floor, including $200 bottles of wine. Many merchants in the area forgo earthquake insurance because it’s too expensive, he said.  A quake about 14 years ago resulted in about $30,000 in damage, he told Fox News, and speculated the current damage would be in excess of $100,000.
"There's collapses, fires," said Napa Fire Capt. Doug Bridewell, standing in front of large pieces of masonry that broke loose from a turn-of-the-century office building where a fire had just been extinguished.  "That's the worst shaking I've ever been in."
Bridewell said he had to climb over fallen furniture in his own home to check on his family before reporting to duty.
The tremor set off car alarms and had residents of neighboring Sonoma County running out of their houses in the middle of night.
The USGS says the depth of the earthquake was just less than 7 miles, and numerous small aftershocks have occurred in the Napa wine country.
Aftershocks were expected to continue for several weeks, though State Geologist John Parrish said they would decrease in magnitude and it was unlikely that there would be a large follow-up earthquake. Still, he warned people to be careful because buildings that were damaged by the quake were now more susceptible to collapse from aftershocks.
“There’s fires, debris all over the streets, everywhere,” Napa resident Karen Hunt earlier told “Fox & Friends.”
Hunt said her husband, who is an engineer, shut off the gas line to their home to guard against explosions, then went to neighbors’ homes to do the same.
“Right now we’re just waiting for the aftershocks,” she said. She said she had not felt any, but reportedly there have been two, one at magnitude 2.5.
Hunt has said she has felt other earthquakes, but “this is way on top of anything I’ve ever felt.”
Hunt, who has lived in Napa since 1996, owns a winery. She said she heard from her partner that her 2011 and 2012 vintages had been destroyed.
“That’s pretty devastating if that’s the case,” she said.
Sunday's quake was felt widely throughout the region. People reported feeling it more than 200 miles south of Napa and as far east as the Nevada border. Amtrak suspended its train service through the Bay Area so tracks could be inspected.
California Highway Patrol Officer Kevin Bartlett said cracks and damage to pavement closed the westbound Interstate 80 connector to westbound State Route 37 in Vallejo and westbound State Route 37 at the Sonoma off ramp. He said there hadn't been reports of injuries or people stranded in their cars, but there were numerous cases of flat tires from motorists driving over damaged roads.
Thousands of small earthquakes occur in California each year, providing scientists with clear indications of places where faults cut the Earth's crust. There were 4,895 earthquakes in California between 1974 and 2003 with a magnitude of 3.5 or greater (about 163 per year).
 

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