30
   

Quake activity along the San Andreas fault is picking up

 
 
CalamityJane
 
  1  
Wed 7 Jul, 2010 06:21 pm
5.4 in the Borrego Springs area about 20 minutes ago - we felt that one pretty
strongly. The 20+ quakes since then in the same area, we did not feel. It is getting a bit unnerving.

http://img688.imageshack.us/img688/1089/picture1fy.png
Butrflynet
 
  1  
Wed 7 Jul, 2010 06:30 pm
@CalamityJane,
I've been watching the SoCal area for a couple weeks now. It doesn't look good for the area between LA and San Diegol lots of unusual activity there for quite awhile now.

Hope you have your emergency kits refreshed and plans organized and up to date, just in case.

There's been a lot of renewed movement in Central CA also. Seems to be a repeat of the same activity cycles and locations in CA the last time the Yellowstone area also increased in activity.
Irishk
 
  1  
Wed 7 Jul, 2010 07:06 pm
@CalamityJane,
I was reading some tweets from friends in the SD area and all of a sudden, they were all tweeting about the earthquake! One said it felt like something picked up their sofa and shook it...oh my!
0 Replies
 
Butrflynet
 
  1  
Wed 7 Jul, 2010 07:46 pm
@CalamityJane,
Just adding the statistics and map for that one to keep the log going:

http://earthquake.usgs.gov/earthquakes/recenteqsus/Maps/special/California_Nevada.gif

Earthquake Details

Magnitude 5.4
Date-Time

* Wednesday, July 07, 2010 at 23:53:33 UTC
* Wednesday, July 07, 2010 at 04:53:33 PM at epicenter

Location 33.420°N, 116.489°W
Depth 14 km (8.7 miles)
Region SOUTHERN CALIFORNIA
Distances 20 km (15 miles) NNW of Borrego Springs, California
40 km (25 miles) SW of Indio, California
45 km (30 miles) S of Palm Springs, California
730 km (455 miles) SE of SACRAMENTO, California

-----------------------------------------

http://www.signonsandiego.com/news/2010/jul/07/strong-earthquake-hits-san-diego-county/

Quote:
5.4 earthquake hits Borrego Springs

By GARY ROBBINS, MIKE LEE and ONELL SOTO

Wednesday, July 7, 2010 at 4:55 p.m.
A magnitude 5.9 earthquake hit Borrego Springs at 4:53 p.m.

/ USGS/Caltech

A magnitude 5.9 earthquake hit Borrego Springs at 4:53 p.m.

Updated 6:21 p.m.

Scientists say a magnitude 5.4 earthquake erupted 13 miles north-northwest of Borrego Springs at 4:53 p.m., shaking all of San Diego County hard and rattling windows as far away as northern Los Angeles County. The quake began 7.3 miles deep and follows a series of smaller quakes in that area in recent weeks, including a 4.9 near Coyote Creek on June 13. Seismologists initially listed today's quake at 5.9 but quickly downgraded it to 5.4.

USGS said that today's earthquake was not an aftershock to to 7.2 Easter Sunday quake. Instead, today's quake occurred on the Clark strand of the larger San Jacinto fault, the most active system -- and possibly most dangerous -- in Southern California. The 130 mile system snakes through parts of Imperial, San Diego, Riverside and San Bernardino counties, and is considered potentially very dangerous because much of the fault is located near heavily populated areas.

The San Jacinto is capable of producing a 7.5 quake, which hasn't happened for a long while. But there was a 6.8 quake on fault on April 21, 1918.


Today's quake "felt like a bomb had exploded," said Bud Perez, a maintenance worker at the Borrego Water District in Borrego Springs.

But that didn't create any immediate problems for the agency, said general manager Richard Williamson.

"We are looking at all the tanks and facilities and everything seems to have rode through it pretty well," he said.

The earthquake produced minor ground motion at the San Onofre Nuclear Generating Station site. The motion was not sufficient to trigger the seismic alarms or lead to a plant shut-down. Plant personnel are conducting routine equipment inspections that follow an incident of this type. No damage has been reported. Both generating units continue to operate normally and safely.

“The building seemed to continue moving, even after the person I was on the phone with stopped feeling the shaking,” said Rachel Laing, a spokeswoman for the mayor who works on the 11th floor of City Hall. A few magazines even fell off a shelf, she said. “It was a pretty serious shake.”

At Center Market in Borrego Springs, Mary Jane Laws said the shaking was violent.

"I have been here 30 years and never felt one that strong," Laws said. "Quite a lot of items fell off the shelves -- quite a few breakages. Salad dressings, soap products, even fluor products and cake mixes."

Laws said her colleagues bolted for the front door but she stayed put. "We know the drills, but when it happened, I froze," she said.

The quake has been followed by seven aftershocks in the 3.0 to 3.6 range, including one at Lake Henshaw. There's a five percent possibility of a 5.0 aftershock within the next 24 hours.

"It looks like it is on the San Jacinto fault system in Borrego Springs, or a splinter of it," said Bob Dollar, a seismologist at the USGS. "A lot of scientists are working on this fault because it is the most active fault in Southern California. We've had more 6s there than any other fault in Southern California in the last century."

The fault produced a 6.5 earthquake on Dec. 25, 1899 that was felt throughout Southern California. The fault also produced a 6.8 quake on April 21, 1918.

Tom Rockwell, a seismologist at San Diego State, said, "Today's quake was on the Clark strand of the San Jacinto, near the Anza seismicity gap. When the San Jacinto has quakes that rupture the surface, they tend to be in the 7.2. to 7.3 range. But the system also gets a lot of quakes in the 5.0 to 6.0 range that don't break the surface."

Rockwell, who has been doing trench work on the San Jacinto, said a massive quake hit the fault on Nov. 22, 1800, and that the "return time" for an event of that scale is estimated at 210 years. However, scientists cannot reliably forecast quakes. So there is no way of knowing whether today's event was a foreshock to a much larger event.



http://latimesblogs.latimes.com/lanow/2010/07/59-earthquake-hits-southern-california.html

Quote:
5.4 earthquake hits Southern California; felt in Los Angeles [Updated]
July 7, 2010 | 5:00 pm


[Updated at 5:26 p.m.: The quake swayed skyscrapers in downtown San Diego, but there were no reports of damage there.

A rockslide was reported on a road outside of Palm Springs neat the aerial tramway, accord to the Desert Sun. But someone at the tramway restaurant told The Times there was no major damage. Palm Springs Fire Chief Blake Goetz told The Times that there was a rock slide near the Palm Springs Aerial Tramway, but no damage to the Tramway itself.




0 Replies
 
Butrflynet
 
  1  
Wed 7 Jul, 2010 07:52 pm
@Butrflynet,
Here's the animation map of quakes in the US for the last 10 days, if it is of interest to anyone else:

http://earthquake.usgs.gov/earthquakes/recenteqsanim/us/
CalamityJane
 
  1  
Wed 7 Jul, 2010 08:07 pm
@Butrflynet,
Quote:
USGS said that today's earthquake was not an aftershock to to 7.2 Easter Sunday quake. Instead, today's quake occurred on the Clark strand of the larger San Jacinto fault, the most active system -- and possibly most dangerous -- in Southern California. The 130 mile system snakes through parts of Imperial, San Diego, Riverside and San Bernardino counties, and is considered potentially very dangerous because much of the fault is located near heavily populated areas.


This is worrisome indeed. I do have an earthquake kit but I think I should
update it now.
0 Replies
 
Butrflynet
 
  1  
Wed 7 Jul, 2010 08:41 pm
This is interesting. Science used to tell us that stress was not transferred. Seems they are changing their minds. Farmerman, is this part of the changing theory that earthquake activity in differing parts of the world may indeed be inter-connected. Or, could it be part of the emerging evidence in the volcanic slip zone monitoring areas in Nor Cal?

http://www.google.com/hostednews/ap/article/ALeqM5g62lBreuMlDQjWUanVDu6Z76zCzAD9GQJB700

Excerpt:

Quote:
Caltech seismic analyst Anthony Guarino said preliminary information indicates the quake was on the San Jacinto fault, one of two that were stressed by the 7.2-magnitude temblor near the U.S.-Mexico border on Easter.

Wednesday's quake was related to the powerful Easter Day temblor, but it was not an aftershock. Seismologist Kate Hutton of the California Institute of Technology said strain from the April temblor transferred to a different fault zone and triggered Wednesday's quake.

Recent airborne analysis by the NASA Jet Propulsion Laboratory found that the Easter quake put increased pressure on the San Jacinto Fault and neighboring Elsinore Fault.


"There's certainly a little higher level of activity than we've seen before" along the two faults, said JPL geophysicist Eric Fielding.

The upshot is that the Easter quake appeared to have decreased the stress on the southernmost San Andreas Fault — slightly lowering the chance of a quake on the mother of California faults.

That's "good news for us living in Southern California," Fielding said.
Butrflynet
 
  1  
Wed 7 Jul, 2010 10:08 pm
Now Alaska is getting into the act:

http://earthquake.usgs.gov/earthquakes/recenteqsus/Maps/AK10/55.65.-160.-140.gif

5.3 Ml - SOUTHERN ALASKA
Preliminary Earthquake Report Magnitude 5.2 Ml
Date-Time

* 8 Jul 2010 03:15:48 UTC
* 7 Jul 2010 19:15:48 near epicenter
* 7 Jul 2010 19:15:48 standard time in your timezone

Location 61.855N 150.508W
Depth 0.3 km
Distances

* 29 km (18 miles) WNW (290 degrees) of Willow, AK
* 33 km (21 miles) N (6 degrees) of Susitna, AK
* 40 km (25 miles) E (94 degrees) of Skwentna, AK
* 84 km (52 miles) NNW (332 degrees) of Anchorage, AK
-------------------------------------
5.0 Mb - SOUTHERN ALASKA
Preliminary Earthquake Report Magnitude 5.0 Mb
Date-Time

* 8 Jul 2010 03:15:49 UTC
* 7 Jul 2010 19:15:49 near epicenter
* 7 Jul 2010 19:15:49 standard time in your timezone

Location 61.839N 150.568W
Depth 10 km
Distances

* 31 km (19 miles) N (1 degrees) of Susitna, AK
* 31 km (19 miles) WNW (285 degrees) of Willow, AK
* 37 km (23 miles) E (97 degrees) of Skwentna, AK
* 84 km (52 miles) NNW (330 degrees) of Anchorage, AK
0 Replies
 
Butrflynet
 
  1  
Thu 8 Jul, 2010 02:38 am
@Butrflynet,
A summary of the technical analysis from USGS is now in:

Quote:
Tectonic Summary

A M5.4 earthquake occurred in southern California at 4:53 pm (Pacific Time) about 30 miles south of Palm Springs, 25 miles southwest of Indio, and 13 miles north-northwest of Borrego Springs. The earthquake occurred near the Coyote Creek segment of the San Jacinto fault, which is one of the strands of the San Jacinto fault. The earthquake exhibited sideways horizontal motion to the northwest, consistent with slip on the San Jacinto fault. It was followed by more than 60 aftershocks of M1.3 and greater during the first hour. Seismologists expect continued aftershock activity.

In the last 50 years, there have been four other earthquakes in the magnitude 5 range within 20 km of this location: M5.8 1968, M5.3 on 2/25/1980, M5.0 on 10/31/2001, and M5.2 on 6/12/2005. The biggest earthquake near this location was a M6.0 Buck Ridge earthquake on 3/25/1937.

The earthquake was felt all over southern California, with strong shaking near the epicenter.

The San Jacinto fault, along with the Elsinore, San Andreas, and other faults, is part of the plate boundary that accommodates about 2 inches/year of motion as the Pacific plate moves northwest relative to the North American plate. The largest recent earthquake on the San Jacinto fault, near this location, the M6.5 1968 Borrego Mountain earthquake April 8, 1968, occurred about 25 miles southeast of the July 7 M5.4 earthquake.

This M5.4 earthquake follows the 4th of April 2010, Easter Sunday, Mw7.2 earthquake, located about 125 miles to the south, well south of the US Mexico international border. A M4.9 earthquake occurred in the same area on June 12th at 8:08 pm (Pacific Time). Thus this section of the San Jacinto fault remains active.

Seismologists are watching two major earthquake faults in southern California. The San Jacinto fault, the most active earthquake fault in southern California, extends for more than 100 miles from the international border into San Bernardino and Riverside, a major metropolitan area often called the Inland Empire. The Elsinore fault is more than 110 miles long, and extends into the Orange County and Los Angeles area as the Whittier fault. The Elsinore fault is capable of a major earthquake that would significantly affect the large metropolitan areas of southern California. The Elsinore fault has not hosted a major earthquake in more than 100 years. The occurrence of these earthquakes along the San Jacinto fault and continued aftershocks demonstrates that the earthquake activity in the region remains at an elevated level. The San Jacinto fault is known as the most active earthquake fault in southern California. Caltech and USGS seismologist continue to monitor the on going earthquake activity using the Caltech/USGS Southern California Seismic Network and a GPS network of more than 100 stations.
0 Replies
 
Butrflynet
 
  1  
Thu 8 Jul, 2010 06:42 pm
@CalamityJane,




0 Replies
 
Butrflynet
 
  1  
Thu 8 Jul, 2010 06:44 pm
@Butrflynet,
More on the transfer of stress to other faults in the area:

Quote:
Earthquake warning for California fault line proves accurate
July 8, 2010 | 9:01 am

http://www.uoregon.edu/~rdorsey/SJFig1.gif

California earthquake experts have been saying for weeks that the 7.2 temblor on Easter Sunday in Mexicali had placed pressure on two Southern California fault lines -- the Elisnore and the San Jacinto -- making quakes there more likely.

They proved prescient.

The 5.4 earthquake that rattled Southern California on Wednesday evening appeared to hit along the San Jacinto fault, officials said. That fault runs roughly from the Salton Sea area northwest through the San Jacinto Mountains toward San Bernardino.

Scientists are now studying how the Mexicali quake changed the pressure of various Southern California fault lines. One questions: Did the temblor make quakes more likely along more dangerous fault lines, such as the Whittier — which produced the deadly 1987 Whittier Narrows quake? Scientists are particularly interested in the Whittier fault because it's connected to the Elsinore and runs under heavily populated areas.

The 5.4 quake on Wednesday wasn't exactly an aftershock of Mexicali.

"We've been calling those 'triggered earthquakes,' " Caltech seismologist Kate Hutton said, referring to temblors north of the aftershock zone that runs from the Gulf of California to Ocotillo, Calif., near the Mexican border.

"We've been able to see an increase in activity," Hutton said. Wednesday's earthquake was the largest to hit the Elsinore and San Jacinto fault zones since the April 4 shaker.
0 Replies
 
Butrflynet
 
  1  
Fri 9 Jul, 2010 10:05 pm
California is still rocking and rolling, where she'll next break, no one knows...

Magnitude 3.0 - NORTHERN CALIFORNIA
2010 July 09 08:42:26 UTC

Magnitude 3.0
Date-Time

* Friday, July 09, 2010 at 08:42:26 UTC
* Friday, July 09, 2010 at 01:42:26 AM at epicenter

Location 38.753°N, 122.711°W
Depth 2.1 km (1.3 miles)
Region NORTHERN CALIFORNIA
Distances

* 3 km (2 miles) SSW (213°) from Anderson Springs, CA
* 8 km (5 miles) W (270°) from Middletown, CA
* 9 km (6 miles) S (174°) from Cobb, CA
* 27 km (17 miles) E (101°) from Cloverdale, CA
* 34 km (21 miles) N (359°) from Santa Rosa, CA
* 110 km (68 miles) WNW (282°) from Sacramento, CA
-----------------------------
Magnitude 3.0 - OFFSHORE NORTHERN CALIFORNIA
2010 July 09 23:56:31 UTC

Magnitude 3.0
Date-Time

* Friday, July 09, 2010 at 23:56:31 UTC
* Friday, July 09, 2010 at 04:56:31 PM at epicenter

Location 40.395°N, 125.132°W
Depth 1.2 km (~0.7 mile) (poorly constrained)
Region OFFSHORE NORTHERN CALIFORNIA
Distances 85 km (55 miles) WSW of Fortuna, California
95 km (60 miles) WSW of Eureka, California
155 km (95 miles) NW of Fort Bragg, California
370 km (230 miles) NW of SACRAMENTO, California
----------------------
Magnitude 3.0 - OFFSHORE NORTHERN CALIFORNIA

Magnitude 3.0
Date-Time

* Saturday, July 10, 2010 at 03:11:21 UTC
* Friday, July 09, 2010 at 08:11:21 PM at epicenter

Location 40.288°N, 124.361°W
Depth 8.3 km (5.2 miles)
Region OFFSHORE NORTHERN CALIFORNIA
Distances 40 km (25 miles) SSW of Fortuna, California
60 km (35 miles) SSW of Eureka, California
105 km (65 miles) NNW of Fort Bragg, California
310 km (195 miles) NW of SACRAMENTO, California

-----------------------------------
Magnitude 3.2 - CENTRAL CALIFORNIA

Earthquake Details

Magnitude 3.2
Date-Time

* Saturday, July 10, 2010 at 03:33:40 UTC
* Friday, July 09, 2010 at 08:33:40 PM at epicenter

Location 36.779°N, 118.191°W
Depth 0 km (~0 mile) (poorly constrained)
Region CENTRAL CALIFORNIA
Distances 20 km (15 miles) NNW of Lone Pine, California
65 km (40 miles) SSE of Bishop, California
110 km (70 miles) ENE of Visalia, California
355 km (220 miles) ESE of SACRAMENTO, California

http://earthquake.usgs.gov/earthquakes/recenteqsus/Maps/special/California_Nevada.gif
0 Replies
 
Butrflynet
 
  1  
Sat 10 Jul, 2010 01:20 pm
3.6 Ml - NORTHERN CALIFORNIA
Preliminary Earthquake Report Magnitude 3.6 Ml
Date-Time

* 10 Jul 2010 16:04:30 UTC
* 10 Jul 2010 09:04:30 near epicenter
* 10 Jul 2010 08:04:30 standard time in your timezone

Location 40.429N 123.563W
Depth 32 km
Distances

* 39 km (24 miles) WSW (246 degrees) of Hayfork, CA
* 41 km (26 miles) NNE (33 degrees) of Redway, CA
* 46 km (29 miles) ESE (106 degrees) of Hydesville, CA
* 65 km (40 miles) SE (128 degrees) of Eureka, CA
* 275 km (171 miles) NW (320 degrees) of Sacramento, CA
0 Replies
 
Butrflynet
 
  1  
Sat 10 Jul, 2010 09:33 pm
Magnitude 3.8 - NORTHERN CALIFORNIA
2010 July 10 16:04:30 UTC

Earthquake Details

Magnitude 3.8
Date-Time

* Saturday, July 10, 2010 at 16:04:30 UTC
* Saturday, July 10, 2010 at 09:04:30 AM at epicenter

Location 40.429°N, 123.564°W
Depth 32.2 km (20.0 miles)
Region NORTHERN CALIFORNIA
Distances 55 km (35 miles) ESE of Fortuna, California
60 km (40 miles) WSW of Weaverville, California
65 km (40 miles) SE of Eureka, California
270 km (170 miles) NW of SACRAMENTO, California
0 Replies
 
Butrflynet
 
  1  
Sun 11 Jul, 2010 12:53 pm
Hello Canada!

http://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/10/230_50.gif

Magnitude 4.1 - VANCOUVER ISLAND, CANADA REGION
2010 July 11 06:22:06 UTC

Earthquake Details

Magnitude 4.1
Date-Time

* Sunday, July 11, 2010 at 06:22:06 UTC
* Saturday, July 10, 2010 at 11:22:06 PM at epicenter

Location 50.488°N, 130.136°W
Depth 10 km (6.2 miles) set by location program
Region VANCOUVER ISLAND, CANADA REGION
Distances 195 km (120 miles) W of Port Hardy, British Columbia, Canada
230 km (145 miles) SW of Bella Bella, British Columbia, Canada
355 km (220 miles) W of Campbell River, British Columbia, Canada
545 km (335 miles) WNW of VICTORIA, British Columbia, Canada

0 Replies
 
Butrflynet
 
  1  
Mon 12 Jul, 2010 03:40 pm
Magnitude 3.5 - OFFSHORE NORTHERN CALIFORNIA
2010 July 12 15:15:12 UTC

Earthquake Details

Magnitude 3.5
Date-Time

* Monday, July 12, 2010 at 15:15:12 UTC
* Monday, July 12, 2010 at 08:15:12 AM at epicenter
* Time of Earthquake in other Time Zones

Location 40.706°N, 124.597°W
Depth 13.3 km (8.3 miles)
Region OFFSHORE NORTHERN CALIFORNIA
Distances

* 31 km (20 miles) WNW (297°) from Ferndale, CA
* 33 km (21 miles) W (265°) from Humboldt Hill, CA
* 36 km (22 miles) W (259°) from Bayview, CA
* 38 km (23 miles) WSW (256°) from Eureka, CA
* 359 km (223 miles) NW (313°) from Sacramento, CA
BumbleBeeBoogie
 
  1  
Mon 12 Jul, 2010 03:57 pm
@Butrflynet,
I have friends who live in Eureka and our Osso Buco used to live 10 miles away from them.
They get strong earthquakes, which is why the state had to close the atomic facility when a quake cracked a critical part of the structure in the 1970s.

BBB
0 Replies
 
Butrflynet
 
  1  
Mon 12 Jul, 2010 11:10 pm
3.4 Ml - NORTHERN CALIFORNIA
Preliminary Earthquake Report Magnitude 3.4 Ml
Date-Time

* 13 Jul 2010 03:03:23 UTC
* 12 Jul 2010 20:03:23 near epicenter
* 12 Jul 2010 19:03:23 standard time in your timezone

Location 38.792N 122.758W
Depth 2 km
Distances

* 4 km (3 miles) E (99 degrees) of The Geysers, CA
* 6 km (4 miles) SSW (213 degrees) of Cobb, CA
* 6 km (4 miles) WNW (288 degrees) of Anderson Springs, CA
* 38 km (24 miles) N (353 degrees) of Santa Rosa, CA
* 115 km (71 miles) WNW (284 degrees) of Sacramento, CA
0 Replies
 
Butrflynet
 
  1  
Tue 13 Jul, 2010 02:06 pm
Magnitude 3.2 - NORTHERN CALIFORNIA
2010 July 13 03:03:23 UTC

Earthquake Details

Magnitude 3.2
Date-Time

* Tuesday, July 13, 2010 at 03:03:23 UTC
* Monday, July 12, 2010 at 08:03:23 PM at epicenter
* Time of Earthquake in other Time Zones

Location 38.792°N, 122.757°W
Depth 2.5 km (1.6 miles)
Region NORTHERN CALIFORNIA
Distances 25 km (15 miles) SSW of Clearlake, California
40 km (25 miles) N of Santa Rosa, California
55 km (35 miles) SE of Ukiah, California
115 km (70 miles) WNW of SACRAMENTO, California
0 Replies
 
Butrflynet
 
  1  
Thu 15 Jul, 2010 11:26 am
http://earthquake.usgs.gov/earthquakes/recenteqsus/Maps/special/California_Nevada.gif

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

* 15 Jul 2010 15:31:43 UTC
* 15 Jul 2010 08:31:43 near epicenter
* 15 Jul 2010 07:31:43 standard time in your timezone

Location 38.819N 122.807W
Depth 2 km
Distances

* 2 km (1 miles) N (359 degrees) of The Geysers, CA
* 8 km (5 miles) WSW (256 degrees) of Cobb, CA
* 11 km (7 miles) WNW (296 degrees) of Anderson Springs, CA
* 42 km (26 miles) NNW (348 degrees) of Santa Rosa, CA
* 120 km (74 miles) WNW (285 degrees) of Sacramento, CA
0 Replies
 
 

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