Earthquake experts see the 'Big One' getting bigger LA Times

[sce56]

Earthquake experts see the 'Big One' getting bigger
http://www.latimes.com/news/local/la-me-san-andreas-20101010,0,7815936.story
Recent reports suggest that the major rupture predicted for the southern San Andreas fault could be longer and stronger than the last big quake, shaking from Monterey County down to the Salton Sea.

The "Big One" that has been forecast for the San Andreas fault could end up being bigger than earthquake experts previously thought.
Recent research showing that a section of the fault is long overdue for a major earthquake has some scientists saying the southern portion of the fault is capable of a magnitude 8.1 earthquake that could run 340 miles from Monterey County to the Salton Sea.
That's significantly stronger and longer than the southern San Andreas' last major rupture, in 1857. Such a temblor would cause much more damage because with a larger stretch of the fault rupturing, a larger area would be exposed to the quake and the shaking would last longer. Whether such a quake would happen in our lifetime had been a subject of hot debate among scientists. That's because until recently, experts believed that a part of the southern San Andreas that runs through the Carrizo Plain 100 miles northwest of Los Angeles would remain dormant for at least another century.

But that rosy hypothesis seemed to be shattered by an August report in the journal Geology by researchers at UC Irvine and Arizona State University, which said that even that section is far overdue for a major quake. "The next earthquake could be sooner than later," Lisa Grant Ludwig, a study coauthor and UC Irvine earthquake expert, said in August. According to U.S. Geological Survey seismologist Lucy Jones, who was not involved in the study, it is possible that all 340 miles of the southern San Andreas could rupture. Such a scenario would trigger a magnitude 8.1 earthquake, said Thomas Jordan, director of the Southern California Earthquake Center, a calculation with which Jones agreed.
<SNIP>
The last Big One ripped through Southern California in 1857, when an estimated magnitude 7.9 quake ruptured 200 miles of fault between Monterey and San Bernardino counties. But it wasn't a wall-to-wall quake: It stopped around the Cajon Pass, near the present-day 15 Freeway, probably because the fault south of that area had shaken just a few decades earlier, in 1812, Jones said. Because the 1812 quake had relieved tectonic tension in the Cajon Pass, it effectively stopped the 1857 quake from moving farther south. "Can I imagine the 1857 earthquake happening again and stopping at the Cajon Pass? Probably not," Jones said. "Once you have a big slip, you're more likely to move along down the fault," she said. "If the rupture has been made ... that's a lot of momentum that will keep the rupture moving down the fault." A magnitude 8.1 wall-to-wall quake would release twice the energy of the 1857 temblor, Jordan said.

The San Andreas has long been considered one of the most dangerous faults in Southern California, in part because of its length. Not only do longer faults produce bigger quakes, but they also emit a type of shaking energy that can travel longer distances.

I can see a big one like that will paralyze LA the freeways will not survive transportation will come to a standstill and relief supplies will be hard to get in!












The I5 CA14 Above failed in both the 1971 Sylmar and 1994 Northridge quakes

[FirstLight]

1. The San Andreas goes all the way up the coast...

They may be minimizing the impact on No. Cal just to make us feel better...

in 1989 the Loma Prieta happened, usually the Hayward fault goes within 5 years after a San Andreas quake. They tend to pop relatively close to eachother...

but it's been 20 years and those faults are still pressurizing... so if the southern piece on the San Andreas goes up, it could definitely trigger the next wave up north too.

you know those tectonic/earth changes maps that say that baja and part of CA will break off and fall into the ocean? :scared:
i guess here in the sierras, I'll have beachfront property after all! :hide:

[Po_d Mainiac]

5. One of Murphy's Laws

everything East of the SA fault will fall into the Atlantic

[Po_d Mainiac]

2. The paralysis could extend far beyond the faults

The financial (banking and insurance) sectors are already on life support.

The 'big one' could shake to Country enough to give the USA a fairly high standing amongst the other third world nations
:tinfoilhat:
YMMV

[jimlup]

3. Yikes!

Glad I don't live in California anymore. No faults, only tornadoes where I reside.

[Moostache]

7. Come to Missouri! WE get BOTH!

The New Madrid fault is priming for a quake as well and we get tornadoes all the time!

Of course, we also have to deal with out of control teabaggers too!

[Beaverhausen]

4. note to self=store more water and buy more canned food

:scared:

[kestrel91316]

6. Relief supplies can and will be helicoptered in if need be. And we already

have shown how quickly we can rebuild critical freeways as evidenced by the 10 on the West side after Northridge.

The VERY good thing is, the San Andreas runs far from the city proper. If it ran underneath us, we'd be toast. My bigger fear is of the Newport-Inglewood fault which DOES run right under the city.

[sce56]

9. There is a big difference between the Northridge 6.9 and an 8.1 as predicted!

I don't think downtown will survive an 8.1 and if all of the freeways fall it will truly be a mess.

The following is from http://en.wikipedia.org/wiki/Richter_magnitude_scale


Richter magnitudes Description Earthquake effects Frequency of occurrence
Less than 2.0 Micro Microearthquakes, not felt. About 8,000 per day
2.0-2.9 Minor Generally not felt, but recorded. About 1,000 per day
3.0-3.9 Often felt, but rarely causes damage. 49,000 per year (est.)
4.0-4.9 Light Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. 6,200 per year (est.)
5.0-5.9 Moderate Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings. 800 per year
6.0-6.9 Strong Can be destructive in areas up to about 160 kilometres (100 mi) across in populated areas. 120 per year
7.0-7.9 Major Can cause serious damage over larger areas. 18 per year
8.0-8.9 Great Can cause serious damage in areas several hundred miles across. 1 per year
9.0-9.9 Devastating in areas several thousand miles across.
1 per 20 years
10.0+ Epic Never recorded; see below for equivalent seismic energy yield.
Extremely rare (Unknown)




Here is a more complex listing since the power is on a logarithmic scale the intensity goes up a thousand fold every higher number.





Richter
Approximate Magnitude Approximate TNT for
Seismic Energy Yield Joule equivalent Example
0.0 15.0 g (0.529 oz) 63.1 kJ
0.5 84.4 g (2.98 oz) 355 kJ Large hand grenade
1.0 474 g (1.05 lb) 2.00 MJ Construction site blast
1.5 2.67 kg (5.88 lb) 11.2 MJ World War II conventional bombs
2.0 15.0 kg (33.1 lb) 63.1 MJ Late World War II conventional bombs
2.5 84.4 kg (186 lb) 355 MJ World War II blockbuster bomb
3.0 474 kg (1050 lb) 2.00 GJ Massive Ordnance Air Blast bomb
3.5 2.67 metric tons 11.2 GJ Chernobyl nuclear disaster, 1986
4.0 15.0 metric tons 63.1 GJ Small atomic bomb
4.5 84.4 metric tons 355 GJ
5.0 474 metric tons 2.00 TJ Seismic yield of Nagasaki atomic bomb (Total yield including air yield 21 kT, 88 TJ)
Lincolnshire earthquake (UK), 2008
2010 Central Canada earthquake<8><9>
5.5 2.67 kilotons 11.2 TJ Little Skull Mtn. earthquake (Nevada, USA), 1992
Alum Rock earthquake (California, USA), 2007
2008 Chino Hills earthquake (Los Angeles, USA)
6.0 15.0 kilotons 63.1 TJ Double Spring Flat earthquake (Nevada, USA), 1994
6.5 84.4 kilotons 355 TJ Caracas (Venezuela), 1967
Rhodes (Greece), 2008
Eureka Earthquake (Humboldt County, California, USA), 2010
Southeast of Taiwan (270 km), 2010
6.7 168 kilotons 708 TJ Northridge earthquake (California, USA), 1994
6.9 336 kilotons 1.41 PJ San Francisco Bay Area earthquake (California, USA), 1989
7.0 474 kilotons 2.00 PJ Java earthquake (Indonesia), 2009
2010 Haiti earthquake
7.1 670 kilotons 2.82 PJ 1944 San Juan earthquake
2010 Canterbury earthquake (New Zealand)
7.2 938 kilotons 3.94 PJ 1977 Vrancea earthquake (Romania)
2010 Baja California earthquake
7.5 2.67 megatons 11.2 PJ Kashmir earthquake (Pakistan), 2005
Antofagasta earthquake (Chile), 2007
7.8 7.52 megatons 31.6 PJ Tangshan earthquake (China), 1976
Hawke's Bay earthquake (New Zealand), 1931
1990 Luzon earthquake (Philippines)
April 2010 Sumatra earthquake (Indonesia)
8.0 15.0 megatons 63.1 PJ San Francisco earthquake (California, USA), 1906
Queen Charlotte Islands earthquake (Britsh Columbia, Canada), 1949
México City earthquake (Mexico), 1985
Gujarat earthquake (India), 2001
Chincha Alta earthquake (Peru), 2007
Sichuan earthquake (China), 2008
1894 San Juan earthquake
8.5 84.4 megatons 355 PJ Energy released is larger than that of the Tsar Bomba (50 megatons, 210 PJ), the largest thermonuclear weapon ever tested
Toba eruption 75,000 years ago; among the largest known volcanic events.<10>
Sumatra earthquake (Indonesia), 2007
8.8 238 megatons 1.00 EJ Chile earthquake, 2010
9.0 474 megatons 2.00 EJ Lisbon Earthquake (Lisbon, Portugal), All Saints Day, 1755
9.1–9.3 1.34 gigatons 5.62 EJ Indian Ocean earthquake, 2004
9.2 946 megatons 3.98 EJ Anchorage earthquake (Alaska, USA), 1964
9.5 2.67 gigatons 11.2 EJ Valdivia earthquake (Chile), 1960
10.0 15.0 gigatons 63.1 EJ Never recorded by humans
12.55 100 teratons 422 ZJ Yucatán Peninsula impact (creating Chicxulub crater) 65 Ma ago (108 megatons; over 4x1030 ergs = 400 ZJ)



UCI: Spanish Explorers Recorded First and Possibly Largest Quake in L.A.
Email this article
2002-03-20


042-KY-02

FOR IMMEDIATE RELEASE

SPANISH EXPLORERS RECORDED FIRST AND POSSIBLY LARGEST QUAKE IN LOS ANGELES HISTORY, SAY UCI RESEARCHERS

1769 Earthquake of Estimated 7 or Larger Magnitude Lifted Orange County Coastline 3 to 11 Feet; Indicates Active Fault Beneath San Joaquin Hills

Irvine, Calif., March 19, 2002 -- California's first recorded earthquake may have been the largest in the history of the Los Angeles basin and powerful enough to raise the Orange County shoreline more than 11 feet in some places, UC Irvine researchers say.

On July 28, 1769, Spanish explorer Gaspar de Portola and his men lay encamped on the banks of the Santa Ana River in what is now north Orange County. They felt a violent earthquake, followed by a number of aftershocks over the next several days. The Spanish measured the length of the shaking by the number of Hail Marys they could utter.

According to Lisa Grant, professor of environmental analysis and design at UCI's School of Social Ecology, the "severe" earthquake described in Portola's July 31 diary entry may have had a magnitude of 7.3, significantly larger than the 6.7-magnitude Northridge earthquake of 1994.

With plants, pollens, shells and a nod to Portola, Grant and UCI colleagues Leslie Ballenger and Eric Runnerstrom have traced geological and historical records to determine that a major earthquake occurred sometime between 1635 and 1855 in the San Joaquin Hills, most likely in 1769. In findings to be published in the March edition of the Bulletin of the Seismological Society of America, the researchers describe uplift averaging 1.8 meters--about 5 feet, 10 inches--along the shoreline from Corona del Mar to Dana Point. The most obvious cause, Grant claims, is a major earthquake, probably along the "blind," or underground, fault in the San Joaquin Hills that Grant first detected in 1999.

"The San Joaquin Hills cover an area previously thought to have low earthquake potential," Grant said. "In findings published in 1999, we discovered that a large-magnitude earthquake could occur here; now we've discovered it has occurred. Our research may the first documented evidence of an early historic or prehistoric blind thrust earthquake."

Grant and her research team used radiocarbon dating to determine the age of plants and shells from the elevated marsh bench, or ancient shoreline, in Upper Newport Bay and along the coastal San Joaquin Hills, finding that they must have been deposited no earlier than 1635. They measured the elevations of the marsh bench and the current shoreline and calculated the earthquake's magnitude from the amount of displacement it caused.

"The shoreline went up, and it went up quickly and by several meters," Grant said. "We knew an earthquake could do that, but there was no documented quake on the Pacific Coast prior to 1769."

So the researchers looked at the historical record of earthquakes since Portola's expedition, including an 1800 earthquake that cracked the walls of Mission San Juan Capistrano and an 1855 quake that may have generated a tsunami off Dana Point. Other researchers think the 1800 earthquake occurred further south or offshore, and the 1855 quake further north in Los Angeles County.

Finally, they studied data from the freshwater San Joaquin Marsh, which lies inland between UCI and Upper Newport Bay. Core samples from the marsh indicate a change in salinity that could have been caused by an earthquake lifting the marsh above sea level. And just above evidence in the sample of changed salinity, Grant said, "there are 'exotic' pollens--European pollens--which were introduced between 1776 and 1797."

The pollens suggest that the earthquake occurred just before, or at approximately the same time that the Spaniards arrived in Southern California. The pollens were the final bit of evidence needed to date, locate and measure the earthquake that Grant believes is the earliest and largest in the history of the Los Angeles basin and to help map the elusive fault that generated it.

"Unlike faults that come to the surface, such as the San Andreas fault, subterranean faults--like the San Joaquin Hills fault and the fault that generated the Northridge earthquake--are difficult to map. We have evidence that an active fault exists, but what it looks like, we don't know," Grant said.

Grant's research was supported by UCI and the Southern California Earthquake Center with funding from the National Science Foundation and United States Geological Survey.

UNIVERSITY OF CALIFORNIA, IRVINE: A TOP-10 PUBLIC UNIVERSITY

[kestrel91316]

11. You have failed to take distance from epicenter into consideration.

Downtown won't shake much worse, if at all, from an 8.1 WAAAAAYYYYYYY over on the San Andreas Fault than it did from the Northridge quake, which was not all that far from downtown. I've already been through about the worst shaking this area (San Fernando Valley) can dish out and that was having that thing directly under me in 1994.

[SharonAnn]

12. Helicopter supplies in for how many million people? Really? I don't think

that will work.

We don't have enough helicopters.

[shireen]

8. damn, this is really scary.

even tho' it's impossible to predict what's going to happen, i hope everyone in that area has thought of some form of emergency plans for family and friends. The more people are prepared, the less difficult it will be for first responders from around the country to help them.

[Bluenorthwest]

10. Be as prepared as possible for any eventuality! ShakeOut!

This week is the CA ShakeOut, Oct 21, 10:21 am. Over 6 million are registered to partipate, all CA families should shuffle through the link and consider doing the ShakeOut and well as reviewing other emergency prep at home and in daily life....
http://www.shakeout.org/