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Quake activity along the San Andreas fault is picking up

 
 
cicerone imposter
 
  1  
Reply Fri 10 Jul, 2009 10:32 am
Seems there's been an 80% increase in earthquake activity here in California.
0 Replies
 
Butrflynet
 
  1  
Reply Fri 10 Jul, 2009 12:31 pm
This article has the most detail about the report and the science behind it.

http://www.latimes.com/news/local/la-me-tremors10-2009jul10,0,6189113.story

Tremor patterns under San Andreas fault offer insights into earthquakes

The seismic activity has increased in the years since the San Simeon and Parkfield quakes, and even seems to have predicted the latter one, study finds.

By Jia-Rui Chong

July 10, 2009

Under the central part of the San Andreas fault, the deep seismic whisperings known as tremors have increased after two recent large earthquakes, and a surge in tremors appears to have foreshadowed one of them, according to a study to be published today in the journal Science.

"It reaffirms the need to be ready," said Robert Nadeau, a research seismologist at UC Berkeley who led the study. "The San Andreas fault is changing down deep and it's changing down deep in places where large earthquakes have happened in the past."

Among the findings was an unusually strong tremor episode three weeks before the magnitude-6.0 Parkfield earthquake in 2004. If these types of signals are found before other large earthquakes, they could provide a kind of early warning, said Greg Beroza, a seismologist at Stanford University who was not involved in the study.

"There have been plenty of tremor episodes that have not triggered earthquakes in other places," he said. "This one might make the strongest case."

Predicting large quakes with precision is the elusive Holy Grail of seismology. Scientists have only been able to calculate probabilities for quakes in certain areas by analyzing a timeline of ruptures and calculating the amount of stress building on a fault.

The latest study may potentially inch us closer to having an actual predictor, scientists said.

Earthquakes typically generate clear seismic waves with sharp onsets, tailing off after a minute or two, seismologists said. Tremors vibrate quietly and can continue for days. Tremors also tend to happen in a deeper, softer part of the Earth's crust, rather than in the upper part typically thought to generate earthquakes.

Seismologists used to ignore tremors because they looked like noise in the data caused by wind or cars. Until recently, scientists also had difficulty storing the enormous amounts of data required to detect tremors.

About 10 years ago, Japanese seismologists discovered deep tremors when they took a closer look at the background noise. Since then, scientists have detected tremors in the Pacific Northwest and below the San Andreas.

Nadeau's study focused on the San Andreas fault in the Parkfield region, about 170 miles northwest of Los Angeles.

Nadeau and graduate student Aurelie Guilhem combed through seismometer data from July 2001 to February 2009. That period included two strong earthquakes: the magnitude-6.5 San Simeon earthquake of 2003 and the Parkfield temblor the following year.

Even though the San Simeon quake originated on a fault about 40 miles away from the San Andreas fault in Parkfield, the quake appeared to set off stress changes under the San Andreas, Nadeau said.

The tremor activity in the Parkfield area 45 days after the San Simeon quake more than doubled compared with the 45 days before the quake.

About eight months later, there was a five-day spike of tremors about 10 times more active than the average before the San Simeon quake, Nadeau found. The tremors quieted, but the Parkfield earthquake hit about three weeks later on the San Andreas.

This surge can be considered a "foretremor" of the Parkfield quake because the events were close together, Nadeau said. But, he added, "we don't have enough resolution to say there's a mechanical connection between the two."

The Parkfield quake appeared to stimulate the tremors again, raising the activity level to about six times the level before the San Simeon quake. Since then, tremor activity has remained high, varying from 1.5 to two times the level before the San Simeon quake.

Scientists still do not understand the exact relationship between tremors and quakes, Nadeau said. But more tremors probably means more stress on the fault, he said, and that suggests "an increased probability of an earthquake coming sooner rather than later."

Southern California has a huge stake in watching this part of the San Andreas fault, said Susan Hough, a seismologist at the U.S. Geological Survey in Pasadena who was not involved in Nadeau's study.

While the 2004 Parkfield earthquake ruptured northward away from Los Angeles, the massive Fort Tejon earthquake in 1857, estimated to have a magnitude of 7.9, appeared to start just south of Parkfield and roar down to the Cajon Pass, Hough said.

That quake sent long, rolling ground motions into the San Fernando Valley and collapsed a number of houses, she said. It was preceded by two moderate quakes in the Parkfield area.

"We don't know for sure, but there's pretty good evidence that the last Big One started up there," Hough said. "So it's always been in the back of people's minds that maybe a moderate quake at Parkfield could be the foreshock to the next Big One."
0 Replies
 
CalamityJane
 
  1  
Reply Sat 11 Jul, 2009 08:43 am
We just had a rude awakening - quite a jolt too!

http://img16.imageshack.us/img16/2135/picture1afh.png
Foxfyre
 
  1  
Reply Sat 11 Jul, 2009 10:17 am
@CalamityJane,
I have not yet experienced an earthquake. You can really significantly feel a 4.0?
CalamityJane
 
  1  
Reply Sat 11 Jul, 2009 10:30 am
@Foxfyre,
Oh yes, you can feel it quite a bit, depending on your location. I am close to the ocean where the epicenter was. It was just a sudden jolt, shaking the house good for a few seconds only.
From my experience, the earthquakes on land are more of a rolling motion and last longer than the ones from the ocean that seem short and more violent.

0 Replies
 
Walter Hinteler
 
  1  
Reply Sat 11 Jul, 2009 10:30 am
@Foxfyre,
I have noticed two earthquakes, one a bit more than 4.0, the other 4.7.

You feel them, not only that things (books) fell down ...
0 Replies
 
Foxfyre
 
  1  
Reply Sun 2 Aug, 2009 04:47 pm
I've notice two or three moderate quakes in north central New Mexico over the last few weeks--the latest this last week. What makes these especially interesting to me is the large number of 'extinct' volcano cores and lava flows throughout that area when NM was having large amounts of seismic activity not all that long ago in the grand scheme of things.

Wouldn't it be interesting if one of those old 'extinct' volcanos was starting to wake up?

Meanwhile, I've noticed that activity along the San Andreas, Hayward, and other California faults has become unusually quiet lately, at least in central California. Is this a good thing? Ominous? Sometimes I wish I worked at the USGS because this stuff is fascinating to me.
ossobuco
 
  1  
Reply Sun 2 Aug, 2009 08:15 pm
@Foxfyre,
Nice, that's close to my house...

but, what me worry? I'm from California and used to much more than 4's.
ossobuco
 
  1  
Reply Sun 2 Aug, 2009 08:18 pm
@ossobuco,
It's true that here no one seems to have the slightest clue about the possibility of earth shifts. Or, as I've mentioned before, drainage. Or traffic or pedestrian access. Or urban planning. I could work up a list.
littlek
 
  1  
Reply Sun 2 Aug, 2009 09:02 pm
@ossobuco,
I always said that in NM it's like the whole state is on The Dope.
Foxfyre
 
  1  
Reply Sun 2 Aug, 2009 09:15 pm
@littlek,
Maybe. But the whole world seems to be moving in here.
roger
 
  1  
Reply Sun 2 Aug, 2009 09:43 pm
@Foxfyre,
Ain't that the truth. I first saw Albuquerque in '67. There was a Burger King just east of the university, and that was the edge of town. Now, it's practically the center.
0 Replies
 
Butrflynet
 
  1  
Reply Mon 3 Aug, 2009 01:56 pm
http://earthquake.usgs.gov/eqcenter/recenteqsus/Maps/US10/22.32.-120.-110.gif

Earthquake Details
Magnitude 6.9
Date-Time

* Monday, August 03, 2009 at 17:59:56 UTC
* Monday, August 03, 2009 at 10:59:56 AM at epicenter
* Time of Earthquake in other Time Zones

Location 29.066°N, 112.871°W
Depth 10 km (6.2 miles) set by location program
Region GULF OF CALIFORNIA
Distances

* 89 km (56 miles) NNE (31°) from Santa Isabel, Baja California, Mexico
* 137 km (85 miles) W (280°) from La Doce, Sonora, Mexico
* 174 km (108 miles) NE (46°) from Guerrero Negro, Baja California Sur, Mexico
* 185 km (115 miles) W (270°) from Hermosillo, Sonora, Mexico
* 553 km (343 miles) SE (133°) from Tijuana, Baja California, Mexico


http://latimesblogs.latimes.com/lanow/2009/08/69-quake-in-baja-california-rattles-office-workers-in-downtown-san-diego.html

A 6.9 earthquake this morning in Baja California was felt in the San Diego area, prompting some people to evacuate a downtown San Diego office tower.

The temblor hit about 360 miles south of the California border, according to the U.S. Geological Survey. TV news footage showed some office workers milling outside San Diego high-rise buildings, and the local NBC affiliate reported that people had left City Hall.

The temblor struck about 11 a.m. in the Gulf of California, about 49 miles from Santa Isabel. There was no immediate word of damage or injuries.

[Updated at noon: There were several moderate temblors in the same part of the Gulf of California before the 6.9 earthquake struck, and officials said this might be a quake swarm.

Officials have not issued a tsumani warning in the wake of the quakes. A preliminary estimate placed the temblor's epicenter about 4 1/2 miles underground.

According to the USGS's Did You Feel It? Web page, the quake was felt in San Diego, Phoenix, Tucson, Los Angeles, Beverly Hills, Long Beach, Orange and elsewhere.]
Foxfyre
 
  1  
Reply Mon 3 Aug, 2009 01:59 pm
@Butrflynet,
Yes I just saw that. A preshock was big too according to the USGS event list:

MAP 6.9 2009/08/03 17:59:56 29.066 -112.871 10.0 89 km ( 56 mi) NNE of Santa Isabel, Mexico
MAP 5.8 2009/08/03 17:55:23 28.976 -112.988 10.3 75 km ( 47 mi) NNE of Santa Isabel, Mexico
0 Replies
 
Butrflynet
 
  1  
Reply Mon 3 Aug, 2009 02:01 pm
@Butrflynet,
http://online.wsj.com/article/BT-CO-20090803-712819.html

MEXICO CITY (AFP)--Four earthquakes, the strongest registering a powerful 6.9 magnitude, struck Monday near the coast of Mexico in Baja California, but there were no immediate reports of damage.

The series of quakes began with a 5.8-magnitude tremor at 1755 GMT, followed by one registering a magnitude of 6.9 at 1800 GMT.

Another of 5.0 magnitude struck at 1833 GMT and a fourth of 5.9 magnitude followed at 1840 GMT, according to the U.S. Geological Survey.

USGS said the epicenter of the strongest quake was located 76 miles north-northeast of Santa Isabel in Baja California, Mexico, and had a depth of 6.2 miles.

Baja California, Mexico's northernmost and westernmost state, is sparsely populated.

The tremor was felt across the border in San Diego, Calif., where a downtown office building evacuated some of its workers, local media said.

There appeared to be no imminent threat of tidal waves from the quakes, USGS said, although individual governments were advised to make their own decisions on whether to issue a tsunami warning.

"Earthquakes of this size sometimes generate local tsunamis that can be destructive along coasts located within a few hundred kilometers of the earthquake epicenter," it added.

"Authorities in the region of the epicenter should be aware of this possibility and take appropriate action."
Butrflynet
 
  1  
Reply Mon 3 Aug, 2009 02:07 pm
@Butrflynet,
We should be getting a first hand report from Calamity Jane in San Diego any minute

Here are the reports of it being felt in Phoenix:


http://www.azcentral.com/community/ahwatukee/articles/2009/08/03/20090803phx-tremors-ON-CR.html

Valley feels tremors from Baja earthquakes

94 comments by John Faherty - Aug. 3, 2009 01:00 PM
The Arizona Republic

Parts of the Valley, including central Phoenix, felt tremors Monday from a series of strong earthquakes that struck the Gulf of California region.

A first quake of 5.8 struck around 10:55 a.m. Arizona time, followed by a 6.9 around 11 a.m., according to the U.S. Geological Survey. There were two aftershocks, one of 5.0 and the other 5.9 at 11:40 a.m. The epicenter was roughly about 100 miles west of Hermosillo, Mexico, and approximately 100 to 150 miles south of the popular American vacation destination Rocky Point.

The tremors could be felt in buildings around the Valley, including the various floors of The Arizona Republic building at Van Buren and Second streets. Others reported on Twitter traffic of elevators creaking, blinds swaying and doors moving; many reported feeling dizzy or discombobulated.

At one central Phoenix building, in the 2000 block of North Central Avenue, the structure shook violently enough that workers were evacuated, a Phoenix Fire spokesman said.

A 6.9 magnitude quake is considered a "strong" tremblor and can cause considerable property damage if it occurs in a populated area, according to the Geological Survey.

The National Oceanic and Atmosphere Administration said there's no tsunami warning, watch or advisory for the coastal areas of California, Oregon, Washington, British Columbia, or Alaska.

Nonetheless, as a precaution, government officials are asking people, including tourists, to stay away from the beaches of Kino Bay and El Desemboque in the state of Sonora for the next two to three hours, following the 6.9 earthquake.

Carlos Arias, the assistant director of Civil Protection for the state of Sonora, said there is no indication of damage at this point.

"There is no reason to panic. The only thing we are asking is that people stay away from Kino Bay and El Desemboque. A tsunami is not possible, but it's possible there could be big waves." But in Rocky Point, the overarching response was a combination of surprise and ambivalence.

Manuel Uato of the Red Cross in Puerto Penasco said he was unaware of the earthquake.

"What time did it happen?'' he asked. "Everything is quiet here. Everyone is fine.''

Glenda Joquaz who works at the library in Rocky Point said that no one there felt anything. "We didn't know it happened. No one felt anything,'' she said. "It's very quiet here.''

There was a similar response by some in Hermosillo, the capitol of the state of Sonora, south of Arizona.

Rosa Vasquez, the reservations manager at the Hotel Ariza, on the north side of Hermosillo, said she was not aware there had been an earthquake. "Sincerely, we haven't felt anything. It's been very quite," Vasquez said.

Teresa Diaz, who works at a hotel in the Sandy Beach area of Rocky Point, said the earthquake got everybody's attention.

"We felt it," she said. "But not too much. I felt it more in my body than in the building. The buildings went back and forth a little, but not too much.

"People were worried, but just for a couple of minutes. It's the beach."

In Goodyear in the West Valley, Rudy Talks, said he felt it.

"I started seeing my lights swaying," he said. "I didn't feel much of a tremor, but I saw my lights move."

Talts said he called his brother-in-law, who lives several miles away, and said the in-law also saw his lights swinging.

"We have long, hanging lights and they were swaying...It was kind of exciting."

The tremors were felt in parts of California as well.

According to reports on nbcsandiego.com, witnesses reported seeing crowds of people streaming out of City Hall in downtown San Diego. There have so far been no reports of damage.
0 Replies
 
Butrflynet
 
  1  
Reply Mon 3 Aug, 2009 02:12 pm
@Butrflynet,
http://www.nbcsandiego.com/news/local-beat/69-Quake-Felt-in-San-Diego-52369142.html

An earthquake measuring 6.9 struck Monday in Mexico but people in San Diego's downtown high rises felt the shaking.

The U.S. National Earthquake Information Center reported the quake struck at 11 a.m. about 50 miles northeast of Santa Isabel in Baja, Calif., 330 miles southeast of Tijuana.

Civil protection officials in the two states on either side of the quake -- Baja California and Sonora -- said there were no reports of damage or injury.

The quake came minutes after two others calculated at magnitudes 5.8 and 5.0, according to the earthquake center.

In San Diego one city employee reported seeing crowds of people filing out of her building. By 11:30 a.m., the crowd of people had moved back inside.

It was more of a strange sound than a rattling according to one downtown worker.

“Wasn’t so much that I felt it but I heard it,” said Greg Shimansky. “It lasted so long it didn’t feel so much like an earthquake.”

Charles Washington was sitting at his desk in a building downtown. “It felt like a creaking noise. It lasted up to 40 seconds,” said Washington. “We thought it was a window washer at first too.”

“We thought it was really something,” he said.

The quakes were all centered in the middle of the narrow slice of sea between the Baja peninsula and Mexico's mainland, which should help cut down on its chances of causing major damage, said Don Blakeman, an analyst at the center.

"It's going to be felt extremely widely and it's possible there may be some damage but there's no way to speculate at this point," Blakeman said.

NBCSanDiego received reports from two people working on higher floors at two separate downtown high rises saying books fell of shelves and file cabinets rocked.

One of our Facebook users, Raffael Antonio Scullari in North Park, messaged us saying nothing was felt in North Park.

Delfina sent us an email saying the SANDAG offices at the Wells Fargo Plaza were swaying. Daphanie works for the city at 4th and B and emailed us to tell us that her building shook during the quake as well.
0 Replies
 
Butrflynet
 
  1  
Reply Sun 9 Aug, 2009 10:39 am
Quote:
Magnitude 4.9 - OFFSHORE NORTHERN CALIFORNIA
2009 August 07 10:49:34 UTC

Earthquake Details
Magnitude 4.9
Date-Time

* Friday, August 07, 2009 at 10:49:34 UTC
* Friday, August 07, 2009 at 03:49:34 AM at epicenter
* Time of Earthquake in other Time Zones

Location 40.310°N, 124.637°W
Depth 16.9 km (10.5 miles)
Region OFFSHORE NORTHERN CALIFORNIA
Distances

* 30 km (19 miles) W (267°) from Petrolia, CA
* 44 km (27 miles) SW (227°) from Ferndale, CA
* 50 km (31 miles) WSW (245°) from Rio Dell, CA
* 67 km (42 miles) SW (217°) from Eureka, CA
* 335 km (208 miles) NW (307°) from Sacramento, CA



Quote:
3.7 Ml - NORTHERN CALIFORNIA
Preliminary Earthquake Report Magnitude 3.7 Ml
Date-Time

* 9 Aug 2009 11:07:08 UTC
* 9 Aug 2009 04:07:08 near epicenter
* 9 Aug 2009 03:07:08 standard time in your timezone

Location 39.900N 120.683W
Depth 65 km
Distances

* 4 km (2 miles) NNE (30 degrees) of Cromberg, CA
* 6 km (4 miles) E (97 degrees) of Greenhorn, CA
* 10 km (6 miles) E (95 degrees) of Spring Garden, CA
* 58 km (36 miles) S (183 degrees) of Susanville, CA
* 164 km (102 miles) NNE (24 degrees) of Sacramento, CA




http://earthquake.usgs.gov/eqcenter/recenteqsww/Maps/region/Asia.gif

This was a deep one!

Earthquake Details
Magnitude 7.1
Date-Time

* Sunday, August 09, 2009 at 10:55:56 UTC
* Sunday, August 09, 2009 at 07:55:56 PM at epicenter
* Time of Earthquake in other Time Zones

Location 33.144°N, 138.040°E
Depth 303.1 km (188.3 miles)
Region IZU ISLANDS, JAPAN REGION
Distances 165 km (100 miles) W of Hachijo-jima, Izu Islands, Japan
175 km (110 miles) S of Hamamatsu, Honshu, Japan
205 km (130 miles) S of Shizuoka, Honshu, Japan
320 km (200 miles) SSW of TOKYO, Japan


http://www.reuters.com/article/latestCrisis/idUST224049

Strong quake jolts Tokyo; trains halted briefly

TOKYO, Aug 9 (Reuters) - A strong earthquake with a preliminary magnitude of 6.9 jolted central Japan on Sunday, halting some train services briefly but there were no immediate reports of damage.

The lengthy quake, felt across the capital just before 8 p.m. (1100 GMT), prompted railway services to halt some high-speed services briefly while tracks were checked, national broadcaster NHK said, but there were no immediate reports of damage.

The tremor was centred 340 km (210 miles) deep under the sea south of Tokyo but, based on a Japanese scale of ground shaking from the Japan Meteorological Agency, it was unlikely there was much damage.

Earthquakes are common in Japan, one of the world's most seismically active areas. The country accounts for about 20 percent of the world's earthquakes of magnitude 6 or greater.

In October 2004, an earthquake with a magnitude of 6.8 struck the Niigata region in northern Japan, killing 65 people and injuring more than 3,000.

That was the deadliest quake since a magnitude 7.3 tremor hit the city of Kobe in 1995, killing more than 6,400. (Reporting by Rodney Joyce and Yoko Nishikawa; Editing by Sanjeev Miglani)
0 Replies
 
Foxfyre
 
  1  
Reply Mon 10 Aug, 2009 04:11 pm
Quote:
Two Quakes Rock Indian Ocean, Japan Less Than 15 Minutes Apart
By Mark Tannenbaum and Aaron Sheldrick

Aug. 11 (Bloomberg) -- Two potentially destructive earthquakes struck minutes apart in the Indian Ocean and Japan today, generating tsunami alerts for India, Myanmar, Indonesia, Thailand, Bangladesh and Japan.

The larger of the two quakes was a magnitude-7.6 temblor that hit the Andaman Islands in the Indian Ocean, and it was followed less than 15 minutes later by a 6.6-magnitude quake in Japan southwest of Tokyo.

The Andaman quake struck at a depth of 33 kilometers (21 miles) at about 1:55 a.m. local time and was centered 260 kilometers north of Port Blair in the Andaman Islands, or about 825 kilometers west of Bangkok, the U.S. Geological Survey said.

A tsunami warning was in effect for as long as three hours after the quake struck for parts of India, Myanmar, Indonesia, Thailand and Bangladesh, the Japan Meteorological Agency said.

The U.S. Pacific Tsunami Warning Center retracted an earlier statement that a potentially destructive tsunami had been generated near the quake epicenter.
http://www.bloomberg.com/apps/news?pid=20601087&sid=ajriIG8eRHEg
0 Replies
 
Foxfyre
 
  1  
Reply Fri 28 Aug, 2009 05:02 pm
I noted in Butrfly's initial post on this thread in November that there was a small earthquake in Oklahoma.

Now this:

http://earthquake.usgs.gov/eqcenter/recenteqsus/index.gif

What the heck is going on?

Quote:
More earthquakes reported in central Oklahoma
By Robert Medley Staff Writer
Published: August 28, 2009

More rumblings underground, all in the same location, have been reported as earthquakes by the Oklahoma Geological Survey in Norman, bringing the total to 9 separate earthquakes in the last 24 hours in the state, the U.S. Geological Survey reports today.

Aug 28 Nine earthquakes rumble Oklahoma in a 24 hour period. No damages reported.

All but one of the earthquakes was reported in eastern Oklahoma County, according to the U.S. Geological Survey. The other quake one was reported northeast of Ada early Thursday.

The largest earthquake was registered as 3.7 magnitude on the Richter scale Thursday night in Jones.

No damages have been reported.

The last quake in the eastern Oklahoma County area was recorded at 10:30 p.m. Thursday on the north and northeast side of Jones, reading 2.4 magnitude on the Richter scale.

In the same location at 10:15 p.m. on the north and northeast side of Jones, an earthquake reading 2.3 magnitude on the Richter scale, according to the survey.

The survey reports the largest was at 9:09 p.m. Thursday, a 3.7 magnitude earthquake was felt in the same area.
http://newsok.com/more-earthquakes-reported-in-central-oklahoma/article/3396369?custom_click=headlines_widget
 

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