Sunday's earthquake swarm of over 300 quakes

[Opmmur]

So. Calf. Swarm Connected to Salton Trough, Cascadia, and Walker Lane​

by Mitch Battros - Earth Changes Media

associated with the 'Salton Trough' has been studied to show connected relevance to the Walker-Lane rift and the Cascadia subduction zone. I will be working through the night to layout the scientific research which currently has geologists (which are also working thru the night) - concerned over today's events and near-future consequences.​

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[BlastTyrant]

I wasn't even aware of Earthquakes sunday.

 

[Opmmur]

Aftershocks Continue to Rattle SoCal

By Monica Garske, Diana Guevara


A rash of up to 70 moderate earthquakes were felt on Sunday from Orange County and San Diego County into Arizona as part of a swarm of shakers located at the south end of the Salton Sea near Brawley, Calif.

The aftershocks continued Monday morning throughout San Diego and parts of Arizona.

According to the USGS, the largest quake was 5.5-magnitude that rattled Brawley, Calif., just before 2 p.m. on Sunday.

A 5.3-magnitude quake centered in Brawley was felt throughout San Diego county at 12:30 p.m. Sunday and a 4.9-magnitude quake followed minutes later, as well as several lower magnitude earthquakes and aftershocks.

The epicenters of the bigger earthquakes were 11 to 12 miles from Imperial, Calif., and 15 to 16 miles from El Centro, Calif., the USGS reported.

According to the USGS, there have been roughly 70 lower magnitude earthquakes in the Brawley area on Sunday alone.

In San Diego, residents across the county reported feeling the quake in places including downtown San Diego, Mission Valley, Santee and Chula Vista. No injuries were reported.

San Diego State University geology expert Pat Abbott told NBC 7 San Diego that Sunday’s earthquakes were in the middle of the Brawley Seismic Zone, famous for swarms of quakes. He said Southern California residents should expect aftershocks.

“[The Brawley Seismic Zone] is a broad zone with lots of little faults,” explained Abbott. “This area has clearly activated. We will likely experience swarms of 3, 4 and 5-magnitude [earthquakes] but they are not likely to increase in intensity. Of course, there are no guarantees on this, but history says they likely won’t get bigger – that we will experience more of the same or smaller quakes,” he added.

As of 1:30 p.m., San Diego Fire Dispatch had no reports of earthquake-related damages or injuries in San Diego county.

The San Onofre Nuclear Generating Station declared a “Notice of Unusual Event” following the earthquakes around 12:30 p.m.

“An earthquake was detected by the station’s monitoring system. The station subsequently received reports of earthquakes near the Mexico border. The plant has been off-line since earlier this year, and there is no safety risk for the public or SONGS employees,” a statement from the plant read.

The declaration is part of protocol set by the Nuclear Regulatory Commission.

At around 1:40 p.m. Southern California Edison posted this update to their Twitter feed: "Earthquake felt in [San Onofre power plant] SCE _SONGS control room. Plant is safely shutdown."

At 1:57 p.m., USGS reported another 5.4-magnitude earthquake centered three miles from Brawley, Calif. USGS later upgraded the quake's magnitude to 5.5.

In compliance with regulations, the San Onofre Generating Station issued a second “Notice of Unusual Event” at 2:03 p.m., following the 5.5-magnitude quake.

Southern California Edison posted this update on its Twitter feed following the second Notice:

“Once again, no plant systems harmed at @SCE_Songs and no risk to public safety. Will update when second NOUE has been closed.”

As of 4 p.m., Pioneer Memorial Hospital in Brawley, Calif., was beginning to evacuate patients due to the ongoing quakes in the area. About a dozen patients were transferred to hospitals in San Diego and Riverside Counties, but the majority of the hospital was operating with a generator.

Brawley Mayor George Nava said all damage to the area was mostly cosmetic damage to businesses and homes. About 30 mobile home residents were displaced, and Red Cross helped them find shelter.

Several outages were also reported following the earthquakes in Brawley. Workers were repairing low pressure instances and power outages in the hours following the quakes.

Monday marks the first day of school for Brawley students, but all schools will be closed to assess the damages.

 

[Opmmur]

Unusual earthquake swarm shakes Southern California

(Reuters) - An unusual swarm of hundreds of mostly small earthquakes has struck Southern California over the last three days and shaken the nerves of quake-hardy residents, but scientists say the cluster is not a sign a larger temblor is imminent.

The earthquakes, the largest of which measured magnitude 5.5, began on Saturday evening and have been centered near the town of Brawley close to the state's inland Salton Sea, said Jeanne Hardebeck, research seismologist for the U.S. Geological Survey.

Scientists were monitoring the earthquake cluster, which continued on Tuesday, to see if it approaches the Imperial Fault, about three miles away. A destructive and deadly earthquake of magnitude 7.0 struck on that fault in 1940, she said.

"We don't have any reason to believe that the (earthquake) storm is going to trigger on the Imperial Fault, but there's a minute possibility that it could," Hardebeck said, adding that the swarm of quakes was not moving closer to that fault.

The Brawley quake cluster, which is caused by hot fluid moving around in the Earth's crust, is different than a typical earthquake, in which two blocks of earth slip past each other along a tectonic fault line.

After that kind of an earthquake of magnitude 5.5 or above, there is a 5 percent chance a larger quake will follow, Hardebeck said. But she added the same kinds of probability estimates were not possible with earthquake clusters caused by the movement of hot fluid.

"We understand them even less than we understand normal earthquakes," Hardebeck said, adding that scientists do not know why a cluster of earthquakes will occur at one time rather than another.

The swarm led to jangled nerves in Brawley, a town of about 25,000 residents 170 miles southeast of Los Angeles near the border with Mexico. "It's pretty bad. We had to evacuate the hotel just for safety," Rowena Rapoza, office manager of a local Best Western Hotel, said on Sunday.

There were two earthquakes on Sunday afternoon, one with a 5.5 magnitude and one measuring 5.3, Hardebeck said. Those were the largest quakes in the cluster amid hundreds of others, she said.

In the past, earthquake clusters have gone on for as long as two weeks, Hardebeck said. Before this recent cluster in Brawley, the last swarm of this size to hit the area was in 1981, she said.

Earlier this month, a pair of moderate-sized earthquakes both registering a magnitude 4.5 struck the California town of Yorba Linda within 10 hours of each other, but no damage was reported. Yorba Linda, the birthplace of the late President Richard Nixon, is 145 miles northwest of Brawley.

(Reporting By Alex Dobuzinskis; Editing by Cynthia Johnston and Philip Barbara)

 

[Opmmur]

Scientists Identify Hot Spots That Trigger Earthquakes
August 30, 2012

Scientists are reviving a century old Tesla experiment by trying to recreate an earthquake through laboratory means.
Nikola Tesla tried recreating earthquakes with his electro-mechanical oscillator, or “earthquake machine,” back in 1898. He attached the device to building structures in a laboratory on Houston Street in New York.

According to legend, the machine shook not only his building, but neighboring structures, leading police to come to his doorstep and make him shut it off.

Now, scientists at Scripps Institution of Oceanography at University of California, San Diego have created a device to help them better understand earthquakes. While Tesla’s device was to aimed at trying to create quakes, the modern researchers wanted to discover how fault zones weaken in select locations after an earthquake reaches a tipping point.

The scientists reported in the journal Nature they have found new information through their laboratory experiments mimicking earthquake processes that show just how these faults weaken.

They said “melt welts” are the culprit on how fault zones weaken in particular locations.

“Melt welts appear to be working as part of a complicated feedback mechanism where complex dynamic weakening processes become further concentrated into initially highly stressed regions of a fault,” Kevin Brown, first author of the study, said in a statement.

“The process allows highly stressed areas to rapidly break down, acting like the weakest links in the chain. Even initially stable regions of a fault can experience runaway slip by this process if they are pushed at velocities above a key tipping point.”

Yuri Fialko, a paper coauthor, said the findings add to the understanding of the earthquake process. He said they address the questions of how these ruptures become energetic and dynamic.

Faults zones like the San Andreas Fault produce very little heat from friction when considering the size and magnitude of the earthquakes they produce.

Laboratory experiments have shown that thermal energy released by friction during slip can become rapidly reduced, which could potentially help account for a “low heat flow paradox.” The melt welts could also explain questions in earthquake rupture dynamics, such as why some slowly slipping tremor-generating events can snowball into massive earthquakes if they pass a velocity tipping point.

“This may be relevant for how you get from large earthquakes to giant earthquakes,” Brown, who used the example of last year’s magnitude 9.0 earthquake off Japan, said in a press release. “We thought that large patches of the fault were just creeping along at a constant rate, then all of a sudden they were activated and slipped to produce a mega earthquake that produced a giant tsunami.”

Fialko said their finding could eventually lead to improved “shake” maps of ground-shaking intensities, and also lead to improved structural engineering plans. Further research could be done to look into why the melt welt weakening occurs, and in what areas.

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