California earthquake swarm is strongest in 30 years, officials say
August 27, 2012
Hundreds of small earthquakes shake Imperial County
The seismic activity is not unusual for the area where the quakes were centered, which is between the San Andreas and Imperial faults, experts said.
LEFT: El Sol Market on Main Street in Brawley, Calif., was hit hard by the earthquakes that hit Imperial County on Sunday. (Brandy Ronek, Associated Press/ August 26, 2012)
By Kate Mather, David Zahniser and Abby Sewell, Los Angeles Times
An "earthquake storm" continued to rattle Imperial County late Sunday, with the region experiencing hundreds of mostly low-intensity temblors that could be felt in neighboring counties.
The seismic activity is not unusual for the area around Brawley, a city of about 25,000 where the quakes were centered and located between the San Andreas and Imperial faults, experts said. The spurt of smaller quakes does not necessarily herald that the Big One is on its way, they said.
After a series of milder quakes in the morning, a magnitude 3.8 temblor hit at 10:02 a.m. about three miles northwest of Brawley, and was followed by a nearly continuous series of quakes in the same general area, according to the U.S. Geological Survey. The two largest quakes, which struck at about 12:30 p.m. and 2 p.m., measured at magnitudes of 5.3 and 5.5, respectively.
By 5 p.m., the USGS had recorded about 300 earthquakes, and the count continued to rise throughout the evening. The vast majority of the temblors measured under magnitude 3.0.
The reason for the recurring swarms in the Brawley seismic zone is not fully understood. The most recent swarm was in 2005, when the area was shaken by hundreds of quakes, with the largest measuring magnitude 5.1, said USGS seismologist Rob Graves.
A previous swarm in 1981 reached a magnitude of 5.8, the highest on record in the area.
Graves said the swarms can last for days, but do not typically foreshadow a bigger quake in the Los Angeles area.
"This type of activity has occurred in the past, and it has not preceded a large earthquake," he said, adding, "That doesn't mean it will always happen that way."
The earthquakes caused "cosmetic" damage to at least three buildings dating to the 1930s in downtown Brawley, said Capt. Jesse Zendejas of the Brawley Fire Department. Crews were still assessing other areas of the city, he said, but no injuries had been reported.
The Imperial County Office of Emergency Services was working with the American Red Cross to set up a shelter at the Imperial Valley College gymnasium for families who were displaced after about 20 mobile homes shifted from their foundations.
The area saw scattered power outages, including at Pioneers Memorial Hospital. The hospital's generators kicked in, but officials decided to evacuate patients as a precautionary measure in case the building had suffered structural damage, said assistant hospital administrator Art Mejia. Hospital officials were inspecting the building with state regulators Sunday evening and had not seen evidence of such damage, he said.
The quakes rattled residents such as Alfonso Alvarez, who has a business renting bounce houses and other party supplies. Alvarez, 28, said he and his family had relocated to the front yard after feeling a series of 15 quakes in two and a half hours.
"It's been pretty bad. Some of them are slow and then they get intense," he said. "We're so anxious right now we can't sit still."
The USGS' "Did You Feel It?" system showed the quakes were felt as far away as San Diego, Temecula and San Clemente, including in the control room of the shuttered San Onofre nuclear plant. (There was no damage reported to the plant.) The 5.3 quake was also felt in Moreno Valley, Indio, National City and Palm Desert.
LEFT: El Sol Market on Main Street in Brawley, Calif., was hit hard by the earthquakes that hit Imperial County on Sunday. (Brandy Ronek, Associated Press/ August 26, 2012)
An "earthquake storm" continued to rattle Imperial County late Sunday, with the region experiencing hundreds of mostly low-intensity temblors that could be felt in neighboring counties.
The seismic activity is not unusual for the area around Brawley, a city of about 25,000 where the quakes were centered and located between the San Andreas and Imperial faults, experts said. The spurt of smaller quakes does not necessarily herald that the Big One is on its way, they said.
After a series of milder quakes in the morning, a magnitude 3.8 temblor hit at 10:02 a.m. about three miles northwest of Brawley, and was followed by a nearly continuous series of quakes in the same general area, according to the U.S. Geological Survey. The two largest quakes, which struck at about 12:30 p.m. and 2 p.m., measured at magnitudes of 5.3 and 5.5, respectively.
By 5 p.m., the USGS had recorded about 300 earthquakes, and the count continued to rise throughout the evening. The vast majority of the temblors measured under magnitude 3.0.
The reason for the recurring swarms in the Brawley seismic zone is not fully understood. The most recent swarm was in 2005, when the area was shaken by hundreds of quakes, with the largest measuring magnitude 5.1, said USGS seismologist Rob Graves.
A previous swarm in 1981 reached a magnitude of 5.8, the highest on record in the area.
Graves said the swarms can last for days, but do not typically foreshadow a bigger quake in the Los Angeles area.
"This type of activity has occurred in the past, and it has not preceded a large earthquake," he said, adding, "That doesn't mean it will always happen that way."
The earthquakes caused "cosmetic" damage to at least three buildings dating to the 1930s in downtown Brawley, said Capt. Jesse Zendejas of the Brawley Fire Department. Crews were still assessing other areas of the city, he said, but no injuries had been reported.
The Imperial County Office of Emergency Services was working with the American Red Cross to set up a shelter at the Imperial Valley College gymnasium for families who were displaced after about 20 mobile homes shifted from their foundations.
The area saw scattered power outages, including at Pioneers Memorial Hospital. The hospital's generators kicked in, but officials decided to evacuate patients as a precautionary measure in case the building had suffered structural damage, said assistant hospital administrator Art Mejia. Hospital officials were inspecting the building with state regulators Sunday evening and had not seen evidence of such damage, he said.
The quakes rattled residents such as Alfonso Alvarez, who has a business renting bounce houses and other party supplies. Alvarez, 28, said he and his family had relocated to the front yard after feeling a series of 15 quakes in two and a half hours.
"It's been pretty bad. Some of them are slow and then they get intense," he said. "We're so anxious right now we can't sit still."
The USGS' "Did You Feel It?" system showed the quakes were felt as far away as San Diego, Temecula and San Clemente, including in the control room of the shuttered San Onofre nuclear plant. (There was no damage reported to the plant.) The 5.3 quake was also felt in Moreno Valley, Indio, National City and Palm Desert.
California earthquake swarm 'pretty bad,' buildings damaged
August 27, 2012
Parts of Southern California were rattled by an earthquake swarm that officials said could last for several days.
Hardest hit was Imperial County, where most quakes were centered.
A number of families were displaced and hospital patients evacuated as a result of a swarm of hundreds of earthquakes earlier in the day.
No deaths or critical injuries were reported as a result of the quakes, the largest of which measured magnitudes 5.3 and 5.5.
Some buildings were damaged by the earlier quakes, including 20 mobile homes that shifted from their foundations, according to the Imperial County Office of Emergency Services. The office was working with the American Red Cross to set up a shelter for displaced families at the Imperial Valley College gymnasium.
The quakes cause scattered power outages, including at Pioneers Memorial Hospital, which lost power for about three hours. Assistant hospital administrator Art Mejia said generators immediately kicked in, but officials decided to evacuate patients as a precautionary measure in case the facility had suffered structural damage.
"We decided to err on the side of caution," he said.
Patients in critical condition were transferred to other hospitals in the area or in San Diego and Riverside counties, while others were either discharged or moved across the street to a medical office building.
Mejia said Sunday evening that hospital staff and state regulators were walking through the hospital to assess the damages, but so far, the damages appeared superficial, including fallen ceiling tiles.
He said they hoped to be able to return patients to the hospital in a matter of hours.
Officials were urging residents to conserve water Sunday, and some schools were planning to close Monday, including Brawley Union High School, schools in the Brawley Elementary School District, Del Rio Community School and Mulberry Elementary.
County officials said updates would be posted on the Imperial County Emergency Medical Services Agency and the Imperial County Public Health Department's Facebook pages, and residents with questions about issues like school closures and water issues may call 760-351-2686.
The earthquakes caused cosmetic damage to at least three buildings dating to the 1930s in downtown Brawley, said Capt. Jesse Zendejas of the Brawley Fire Department. Crews were still assessing other areas of the city, he said, but no injuries had been reported.
The succession of quakes rattled Brawley resident Alfonso Alvarez, who has a business renting “bounce houses” and other party supplies. Alvarez, 28, said he and his family had felt 15 quakes over two and a half hours and, after the biggest one, had relocated to the front yard.
“It’s been pretty bad. Some of them are slow and then they get intense,” he said. “We’re so anxious right now we can’t sit still.”
"Earthquake storm" continues to rattle Imperial County, surrounding areas
August 26, 2012
An “earthquake storm” continued to rattle Imperial County on Sunday, with the region experiencing about 300 temblors throughout the day but causing little damage.
The majority of the quakes were low-intensity, but two reached magnitudes above 5.0 -- 5.3 and 5.5 respectively -- early in the afternoon.
"Obviously, all this activity is related or interconnected, but it doesn't really follow the typical main shock, aftershock activity," said Rob Graves, a seismologist with the U.S. Geological survey.
Such earthquake storms are not unprecedented or unusual in that region. The most recent, Graves said, also centered near Brawley, was in 2005, when the area was shaken by hundreds of earthquakes, the largest measuring magnitude 5.1. A previous swarm in 1981 reached a magnitude of 5.8.
The earthquakes caused cosmetic damage to at least three buildings dating to the 1930s in downtown Brawley, said Capt. Jesse Zendejas of the Brawley Fire Department. Crews were still assessing other areas of the city, he said, but no injuries had been reported.
The cause of the swarm phenomenon is not entirely understood, Graves said, although he noted that the Brawley area is a transition between known active earthquake faults, including the Imperial fault to the south and the San Andreas fault to the north.
The current swarm
could last for days,
Jones said.
The data collected during this event may give clues to what causes the phenomenon, he said.
The succession of quakes rattled Brawley resident Alfonso Alvarez, who has a business renting “bounce houses” and other party supplies. Alvarez, 28, said he and his family had felt 15 quakes over two and a half hours and, after the biggest one, had relocated to the front yard.
“It’s been pretty bad. Some of them are slow and then they get intense,” he said. “We’re so anxious right now we can’t sit still.”
The USGS' "Do You Feel It" system shows the quakes were felt as far away as San Diego, Temecula and San Clemente. The 5.3 quake was also felt in Moreno Valley, Indio, National City and Palm Desert.
Lucy Navarro, who works at the front desk at the Vacation Inn in El Centro, said she felt two of the afternoon’s quakes, including the one that reached 5.3 magnitude at 12:30 p.m.
“The first one was pretty strong," she said. "That one scared me because it really shook me. I could see the building move."
The first quake — a magnitude 3.8 temblor — occurred at 10:02 a.m. about three miles northwest of Brawley, and was followed by a series of other quakes in the same general area, according to the U.S. Geological Survey.
The agency's data have changed throughout the day, but the two largest quakes measured at magnitudes of 5.5 and 5.3.
Seismologist Lucy Jones of the USGS said the activity was not uncommon for the area, a region known as the "Brawley Seismic Zone" that sits between the San Andreas and Imperial faults. Similar swarms occurred in the area in the 1970s, she said, the most recent in 1981.
"This is a classic Brawley Seismic Zone swarm," she said. "It's relatively hot."
Experts can't predict what size temblors could come, but Jones said they have never seen a Brawley swarm produce anything larger than a magnitude 5.8 quake. That rattler was part of the 1981 swarm.
"We've never seen a Brawley swarm followed by a big earthquake on another fault," she added.
The current swarm could last for days, Jones said.
A series of earthquakes rattles San Diego area
Posted: 08/27/2012
SAN DIEGO (AP) -- Dozens of small to moderate earthquakes struck southeastern California on Sunday, knocking trailer homes off their foundations, shattering windows and rattling nerves in a small farming town east of San Diego.
The largest quake, at 1:57 p.m., registered at a magnitude 5.5 and was centered about three miles northwest of the town of Brawley, said Robert Graves, a geophysicist with the U.S. Geological Survey. Another quake about an hour and a half earlier registered at magnitude 5.3.
No injuries were reported.
...
read more at http://www.mercurynews.com/california-earthquakes/ci_21405235/series-earthquakes-rattles-san-diego-area
Earthquake swarm puts California town on edge
Published August 27, 2012
Associated Press
BRAWLEY, Calif. – A series of small to moderate earthquakes that shattered windows and knocked trailer homes off their foundations is putting this small farming town east of San Diego on edge as they continue to feel jolts that scientists said could last for days.
The largest quake, registered at a magnitude 5.5, struck at 1:57 p.m. Sunday and was centered about three miles northwest of Brawley, said Robert Graves, a geophysicist with the U.S. Geological Survey. Another quake about an hour and a half earlier registered at magnitude 5.3.
No injuries were reported.
More than 30 additional earthquakes with magnitudes of at least 3.5 shook the same area near the southern end of the Salton Sea, Graves said.
"The type of activity that we're seeing could possibly continue for several hours or even days," Graves said.
The quakes pushed 20 mobile homes at a trailer park off their foundations and rendered them inhabitable, said Maria Peinado, a spokeswoman for the Imperial County Emergency Operations Center. A red-tiled roof apparently collapsed and landed on a wooden fence.
Sporadic power outages, at one point affecting 2,500 Imperial Irrigation District customers, also prompted authorities to evacuate 49 patients from one of the county's two hospitals, Peinado said. Police also received numerous calls about gas leaks and water line breaks.
"Sunday's quake cluster occurred in what scientists call a transition zone between the Imperial and San Andreas faults, so they weren't assigning the earthquakes to either fault, Graves said."
By late Sunday, a magnitude-5.1 quake followed by several more with magnitudes of at least 4.0 shook the area.
"It's not uncommon for us to have earthquakes out here, but at this frequency and at this magnitude it's fairly unusual," said George Nava, the mayor of Brawley, a town of 25,000.
"And the fact that the aftershocks keep coming are a little alarming," he said.
At the El Sol Market, food packages fell from shelves and littered the aisles.
"It felt like there was quake every 15 minutes. One after another. My kids are small and they're scared and don't want to come back inside," said Mike Patel, who manages Townhouse Inn & Suites.
A TV came crashing down and a few light fixtures broke inside the motel, Patel said.
The first quake, with a magnitude of 3.9, occurred at 10:02 a.m. The USGS said more than 300 aftershocks struck the same approximate epicenter.
Some shaking was felt along the San Diego County coast in Del Mar, some 120 miles from the epicenter, as well as in southwestern Arizona and parts of northern Mexico.
USGS seismologist Lucy Jones said earthquake swarms are characteristic of the region, known as the Brawley Seismic Zone.
"The area sees lots of events at once, with many close to the largest magnitude, rather than one main shock with several much smaller aftershocks," Jones said.
The last major swarm was in 2005, following a magnitude-5.1 quake, she said.
Sunday's quake cluster occurred in what scientists call a transition zone between the Imperial and San Andreas faults, so they weren't assigning the earthquakes to either fault, Graves said.
Read more: http://www.foxnews.com/us/2012/08/27/earthquake-swarm-puts-california-town-on-edge/#ixzz24m4PzBFU
The following is posted by the video poster...
Published on Aug 26, 2012 by dutchsinse
90 miles ENE of Tijuana Mexico -- near the border of California and Mexico -- a series of mid-range earthquakes (5.0M and 4.0M) struck.. followed by multiple DOZENS of subsequent earthquakes in the same location ... a swarm ... not really aftershocks.. since the largest of the tremors was a 5.4M.
Which, to me, means we need to watch for a LARGE earthquake at the end of this chain reaction.. the 5.4M wouldn't be large enough to cause such movement that we're actually having.
If you live in the southern California area -- or along the west coast extending near the fresh lava fields off the coast of Oregon... also along the edge of the north American Craton... New Mexico, Colorado, Oklahoma, Texas, Louisiana, Arkansas, Missouri.. and the east coast states extending northeast to New Brunswick Canada.
Be prepared for followup movement in adjacent areas to the south California swarm zone.
Which, to me, means we need to watch for a LARGE earthquake at the end of this chain reaction.. the 5.4M wouldn't be large enough to cause such movement that we're actually having.
If you live in the southern California area -- or along the west coast extending near the fresh lava fields off the coast of Oregon... also along the edge of the north American Craton... New Mexico, Colorado, Oklahoma, Texas, Louisiana, Arkansas, Missouri.. and the east coast states extending northeast to New Brunswick Canada.
Be prepared for followup movement in adjacent areas to the south California swarm zone.
