A New Forecast of California Earthquakes
The 2007 Working Group on California Earthquake Probabilities (WGCEP 2007), a multi-disciplinary collaboration of scientists and engineers, has released the Uniform California Earthquake Rupture Forecast (UCERF)—the first comprehensive framework for comparing earthquake likelihoods throughout all of California. It provides important new information for improving seismic safety engineering, revising building codes, setting insurance rates, and helping communities prepare for inevitable future earthquakes.
In developing the UCERF, the 2007 Working Group revised earlier forecasts for Southern California (WGCEP 1995) and the San Francisco Bay Area (WGCEP 2003) by incorporating new data on active faults and an improved scientific understanding of how faults rupture to produce large earthquakes. It extended the forecast across the entire state using a uniform methodology, allowing for the first time meaningful comparisons of earthquake probabilities in urbanized areas such as Los Angeles and San Francisco Bay Area, as well as comparisons among the large faults in different parts of the state.
The study was organized by the Southern California Earthquake Center, the U.S. Geological Survey, and the California Geological Survey, and it received major support from the California Earthquake Authority, which is responsible for setting earthquake insurance rates statewide. During the three-year study, advice and comment was sought from the broader community of earthquake scientists and engineers through open meetings and workshops. Where experts disagreed on aspects of the forecast, alternative options were accounted for in calculations to reflect these uncertainties. The final forecast is a sophisticated integration of scientific data and expert opinion.
UCERF Earthquake Probabilities
Figure 1
Figure 2
According to the new forecast, California has a 99.7% chance of having a magnitude 6.7 or larger earthquake during the next 30 years (see Figure 1). The likelihood of an even more powerful quake of magnitude 7.5 or greater in the next 30 years is 46%. Such a quake is more likely to occur in the southern half of the state (37% chance in 30 years) than in the northern half (15% chance in 30 years) (see Figure 2).
Figure 3
Figure 4
The probability of a magnitude 6.7 or larger earthquake over the next 30 years striking the greater Los Angeles area is 67%, and in the San Francisco Bay Area it is 63%, similar to previous WGCEP estimates (see Figure 3). For the entire California region, the fault with the highest probability of generating at least one magnitude 6.7 quake or larger is the southern San Andreas (59% in the next 30 years; see Figure 4). For northern California, the most likely source of such earthquakes is the Hayward-Rodgers Creek Fault (31% in the next 30 years). Events of this size can be deadly, as shown by the 1989 Loma Prieta earthquake (magnitude 6.9) and 1994 Northridge earthquake (magnitude 6.7).
Earthquake probabilities for many parts of the state are similar to those in previous studies, but the new probabilities calculated for the Elsinore and San Jacinto Faults in southern California are about half those previously determined. For the far northwestern part of the State, a major source of earthquakes is the offshore 750-mile-long Cascadia Subduction Zone, the southern part of which extends about 150 miles into California. For the next 30 years there is a 10% probability of a magnitude 8 to 9 quake somewhere along that zone. Such quakes occur about once every 500 years on average.
Figure 5
The UCERF model includes the concept that earthquake likelihoods change with time. A fault that has ruptured in a recent large earthquake is less likely to produce another quake in the near future, because tectonic stress has not had time to build back up. Likewise, a fault that last ruptured a long time ago is more likely to produce an earthquake, because the stress on the fault has had time to re-accumulate. The faults with elevated probabilities for an earthquake include the southern San Andreas and Hayward-Rodgers Creek Faults (see Figure 5), although major quakes on these faults may still be decades away.
Earthquake Forecasting, Hazard, and Risk
Californians know that their state is subject to frequent—and sometimes very destructive—earthquakes. Accurate forecasts of the likelihood of earthquakes can help people prepare for these inevitable events. Because scientists cannot yet make precise predictions of the date, time, and place of future quakes, forecasts must be in the form of the probabilities of quakes of certain sizes occurring during specified periods of time.
In daily living, people are used to making decisions based on probabilities—from the flip of a coin (50% probability of heads) to weather forecasts (such as a 30% chance of rain) to the annual chance of being killed by lightning (about 0.0003%). In comparison, the probability of a magnitude 7.5 or greater earthquake striking somewhere in California is about 2% per year.
Earthquake probabilities derived by scientists can help people plan and prepare for future quakes. When an earthquake occurs, two things happen. The first is a fault rupture—a crack in the Earth’s crust—gives way and slips under tectonic stress. The second is the radiation of seismic waves caused by this sudden fault motion, which spread out like ripples from a pebble tossed into a pond. The ground shaking that occurs as these seismic waves pass by causes most of the damage. The strength of the waves at a particular site depends on the earthquake’s magnitude, which measures the size of the fault rupture, the distance of the site from the rupture, and the local geological conditions at the site.
The UCERF study has determined the probabilities that different parts of California will experience earthquake ruptures of various magnitudes (“earthquake rupture forecast”) but not the likelihood of shaking that will be caused by these quakes (“seismic hazard”). This is an important distinction, because even areas with a low probability of fault rupture can experience shaking and damage from distant, powerful quakes.
The U.S. Geological Survey is incorporating the UCERF into its official estimate of California's seismic hazard, which in turn will be used to update building codes. Other subsequent studies will add information on the vulnerability of manmade structures to estimate expected losses, which is called “seismic risk.” In these ways, UCERF will help to increase public safety and community resilience to earthquake hazards.
The results of the UCERF study serve as a reminder that all Californians live in earthquake country and should therefore be prepared (see Putting Down Roots in Earthquake Country). Although earthquakes cannot be prevented, the damage they do can be greatly reduced through prudent planning and preparedness. The ongoing work of the Southern California Earthquake Center, U.S. Geological Survey, California Geological Survey, and other scientists in evaluating earthquake probabilities is part of the National Earthquake Hazard Reduction Program’s efforts to safeguard lives and property from the future quakes that are certain to strike in California and elsewhere in the United States.
WEATHER NOTE
Update at 7:55 a.m. PDT: The status of Intel's plant and the figure for the estimated death toll have been updated.
A massive earthquake struck Western China on Monday, killing up to 5,000 people and trapping more than 900 students in a high school, according to press reports.
The 7.8 magnitude earthquake was centered in a mountainous region of the country in the Sichuan Province, according to The New York Times.
The epicenter was in Xinhua, about 55 miles northwest of Chengdu, the capital of Sichuan--one of the country's most populated provinces, The Wall Street Journal reported, noting the earthquake struck about 2:30 p.m. local time Monday in China--or 11:28 p.m. PDT Sunday.
Sichuan has attracted tech companies to the province, as has China as a whole for outsourcing domestic tech work and as a growing and viable market for technology companies such as Dell to sell into.
Intel, for example, announced in 2003 its investment of $200 million in a chip test-and-assembling center in Chengdu.
On Monday, Intel spokesman Chuck Mulloy said none of its employees in Chengdu were injured, nor was its facility damaged.
The chip giant immediately evacuated its roughly 2,000 workers from the plant when the earthquake struck, Mulloy said.
The plant has no power or water and is currently running on back-up power. Intel hopes to have the test-and-assembly center running again by Wednesday.
"We are geographically diverse, so there is no near-term impact to the business," Mulloy said.
He added that no product is exclusively tested and assembled at the Chengdu plant. The site focuses on microprocessors, chipsets, and communications chips.
Chengdu is also set to host the World Cyber Games' grand finale in 2009. The World Cyber Games is one of the largest global video game tournaments--if not the largest.
OpenTV, which provides software for digital set-top boxes, announced in 2001 it would team up with a system integration company, Sichuan NTC, to launch interactive TV via cable in the Henan province.
Accounts of the earthquake came fast and furious. Graham Webster, a member of the CNET Blog Network, twittered: "13 seismic events above 4.9 measured since the first quake, reports USGS"
The U.S. Geological Survey (USGS), which tracks earthquakes around the world, reported the 7.8 earthquake had a depth of 6.2 miles.
Other bloggers, such as Rory Cellan-Jones of the BBC news blog offered commentary on whether news of the earthquake via Twitter marks its coming of age as the platform for truly real-time news.
Beijing, which is approximately 950 miles from the epicenter, also felt the effects of the earthquake, but it was a "quiet rolling sensation," according to a CNN report. The news agency also noted that the earthquake was also felt in Hong Kong, Shanghai, and Taiwan--and as far as Vietnam and Bangkok.
Sina.com, one of China's most popular sites, featured photos that appear to be related to Monday's earthquake.
U.S. officials say at least 22 killed by tornadoes
 A flag flies over the wreckage of a destroyed home near Racine, Mo., on Sunday, May 11, 2008. (AP / Mark Schiefelbein)  Chris Bryant stands by the damage to a sign on Harrison Road and Eisenhower Parkway in Macon, Ga. on Sunday, May 11, 2008. (AP / Woody Marshall)  Michael Richardson, center, and his mother, Betty Lawson, right, carry a crib from Richardson's home in Picher, Oklahoma on Sunday, May 11, 2008. (AP / Sue Ogrocki) |
CTV.ca News Staff
Updated: Sun. May. 11 2008 10:39 PM ET
Survivors of a series of tornado strikes in the U.S. struggled to come to terms with the destruction Sunday, as officials raised the death toll to 22.
Susan Roberts, a 61-year-old resident of Seneca, Missouri, was left with a heavily damaged 1985 Cadillac in her living room. A woman who had sought shelter in the car had died.
Roberts had warned the woman to flee, minutes before a tornado hit the area. The victim had been trying to change a tire.
"That is what is tearing me up," Roberts told The Associated Press.
At least 15 people died in southwestern Missouri. Officials said another death has been confirmed in Georgia, after the storms made their way there on Sunday.
And at least six people died in Picher, a mining town in Oklahoma, when a tornado tore up a 20-block swath on Saturday.
"We've seen homes that were completely levelled to the foundation," said state Highway Patrol Lt. George Brown of the damage in Picher. "In a few of these homes you would have had to be subterranean to survive."
One of Picher's dead includes an infant, he said. At least three others have been confirmed missing. Crews and search dogs are hunting for survivors or bodies in the piles of debris.
"Trees are toppled over, ripped apart," said Ottawa County emergency manager Frank Geasland. "There are cars thrown everywhere. It looks like a bomb went off, pretty much."
About 150 Picher residents were injured during the storm. Thirty-two people had been taken to hospital, with 26 already released, Geasland said.
Picher is a town of 800 and is heavily polluted by lead from nearby mines. It sits in the state's extreme northeast near the border with Kansas and Missouri.
Ten died when a twister hit near Seneca, Mo., about 32 kilometres southeast of Picher.
American Red Cross disaster relief officials have set up a command post in the area and are providing shelter, food and water to those sifting through what remains of their homes. The agency's Joann Moore told CTV Newsnet on Sunday that the weather has been good for the relief efforts.
Oklahoma's Gov. Brad Henry planned to visit the area Sunday afternoon.
"Our thoughts and prayers are with the people of Picher and all of the other Oklahoma communities that have been impacted by the latest wave of severe weather," he said.
A newspaper in Joplin, Mo. said more than 90 people were being treated in local hospitals following the storm.
A tornado also struck in Arkansas as the storm system swept eastward through the night.
President George Bush has pledged government support in helping communities recover from the massive wreckage.
"The federal government will be moving hard to help," he said. "I'll be in touch with the governors and offer all of the federal assistance we can."
Another storm heading for Burma
HE United Nations today warned another storm was headed in the direction of Burma, which could complicate the slow-moving relief efforts from deadly Cyclone Nargis.
An estimated 1.5 million people have been left homeless by the disaster, which has killed tens of thousands, and the storm could pose serious risks to those battling disease, said Richard Horsey, a UN relief spokesman.
"Our meteorological people tell us there's likely to be fairly strong rainfall in the next seven days,'' he said.
"That's going to be a big issue with unpaved roads. Heavy rainfall could complicate things for all those people going without shelter,'' Horsey said.
"If there's an epidemic of water-borne disease and a lack of shelter when a storm comes in ... if we have another storm coming into the delta, that's going to be a significant concern for all those people without shelter.''
The country's military, which has run Burma with an iron fist for almost half a century, said earlier that it welcomed shipments of supplies but was "not ready'' to let in foreign aid workers, including disaster experts.
"If we don't get this relief effort up to full scale quickly, there's significant risk of a second round of this disaster which could potentially kill as many people as the initial cyclone,'' Mr Horsey said.
The Meteorological Department reported at 4 AM today (May 12th) reported that a trough of low pressure cells lies across central and eastern Thailand, and the southwest monsoon over the Andaman Sea, southern Thailand and the Gulf of Thailand is strengthening. More thundershowers with isolated heavy rainfall are likely over the areas. People in the provinces of Tak, Kamphaeng Phet, Phichit, Nakhon Sawan, Prachin Buri, Chachoengsao, Chumphon, Ranong, Phangnga and Phuket should beware of hazardous weather during this period.
High waves above two meters are present in the Andaman Sea and the Gulf of Thailand. All ships should proceed with caution, and small boats should stay ashore during until May 15th.
Bangkok metropolis and vicinity can expect fairly widespread thundershowers with isolated heavy rain. The daily temperature would range from 25 to 33 degrees Celsius. The speed of southwesterly winds would be around 15 to 30 kilometers per hour.MARITIME NOTE
Coast Guard Issues Safety Alert
WASHINGTON - The office of Investigations and Analysis at Coast Guard Headquarters, here, issued a marine safety alert May 9, advising vessel owners and operators to examine their vessels' watertight integrity and the placement of high-level bilge alarms within their vessels.
The alert was issued in light of information revealed during the ongoing marine board of investigation for the sinking of the Alaska Ranger March 28, that resulted in the loss of five lives, as well as other accident investigations that identified similar issues.
The Coast Guard advised vessel owners and operators to implement a watertight door inspection program that will help ensure all watertight decks and bulkheads are inspected periodically. The inspections should ensure the watertight doors will function properly to prevent progressive flooding in the event of an accident or other incident that causes flooding. The Coast Guard also recommended that all vessel crewmembers be familiar with the locations of watertight doors and weather tight closures throughout their vessels.
The safety alert further urged vessel owners and operators to ensure high-level bilge alarms are arranged to provide the earliest warnings of the abnormal accumulation of water. These alarms should be set as low as possible to the deck or bilge-well along the center-most area of the bilge.
The complete marine safety alert is available online at http://marineinvestigations.us and then by selecting safety alert and most current.
The U.S. Coast Guard typically conducts approximately 14,000 marine casualty investigations to identify the causal factors of reportable maritime accidents. The findings and lessons learned from these investigations are used to develop new standards to prevent future accidents.
Panama Canal – transit of HMS BOUNTY
The Panama Canal Authority issued a press release stating that the H.M.S. BOUNTY transited the Panama Canal en route from St. Petersburg, Florida to the US West Coast. Some people, myself included, had assumed that the ship was wrecked at Pitcairn Island after the mutiny led by Fletcher Christian (or Marlon Brando, whichever). (5/8/08).
RS
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