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Quake report unsettling

• New report outlines what will happen in SCV when Big One hits

Posted: May 25, 2008 1:38 a.m.
Updated: July 26, 2008 5:02 a.m.
 

When the Big One hits Santa Clarita some will likely die, many will be injured and many buildings will be destroyed.

That's the bad news about a 7.8 magnitude earthquake hitting our area, based on a scenario presented in a scientific report released this week by the U.S. Geological Survey, and on a safety report released last month by the city of Santa Clarita.

The good news is that California, and specifically Santa Clarita, have learned from past earthquake mistakes and have done much to minimize injury and damage as a result.

"It is more important what you do before the earthquake than what you do after it," said Adele MacPherson, emergency manager for the city of Santa Clarita.

"It is all about preparedness," she told The Signal Friday. "We came through (other, smaller) earthquakes because we were prepared."

When the Northridge quake hit on Jan. 17, 1994, it registered a magnitude 6.7 on the Richter scale.

It killed 57 people, injured 9,253 and displaced 20,000.

In Santa Clarita, less than 23 miles from the Northridge epicenter, no one died but damage to roads and bridges totaled more than $29 million. The damage city-wide was estimated at between $300 and $400 million, MacPherson said.

Today, there is a 67 percent chance that a magnitude 6.7 or larger earthquake will hit the greater Los Angeles area sometime in the next 30 years, according to the geological survey group.

A 7.8 quake along the San Andreas fault - similar to the recent earthquake in China - would cause a loss of lives and massive damage to infrastructure, including critical transportation, power, and water systems.

In the geological group's scenario, the earthquake would kill 1,800 people, injure 50,000, cause $200 billion in damage, and have long-lasting social and economic consequences.

It's impact on Santa Clarita would figure into each of those respective numbers.

The "Shakeout Scenario"

Thursday's U.S. Geological Survey report is considered by its presenters to be the most comprehensive analysis ever of what a major Southern California earthquake would mean to residents.

It is the scientific framework for what is expected to be the largest earthquake preparedness drill in California history, scheduled for Nov. 13.

The exercise - dubbed Golden Guardian '08 - is expected to test the ability of emergency responders to deal with a magnitude 7.8 earthquake on the San Andreas Fault, and is being jointly organized by the Governor's Office of Emergency Services and the California Office of Homeland Security.

The exercise will occur during a week-long series of public events planned, for what those agencies are calling the "Great Southern California Shakeout."

Next week, on June 4, a kick-off event is planned for the "Shakeout Scenario" which is expected to help communities plan to respond to the risks highlighted in the scenario.

Local officials say preparedness is the only way to minimize damage and injury.

Santa Clarita City Emergency Management staff is on a state priority list of agencies to be notified immediately in the event of any earthquake in the state, Macpherson said.

"The neat thing about the (US Geological Survey) report is that it's science-based," she said. "The fact that it is a scientific study gives it more credibility."

The geological ‘Shakeout Scenario' report was released Thursday in conjunction with the California Geological Survey during a Congressional hearing in Washington, D.C.

The House Committee on Natural Resources, Subcommittee on Energy and Mineral Resources, led by Chairman Jim Costa (D-CA), will hold an oversight hearing on USGS efforts to prepare for future earthquakes.

The strongest shaking and greatest damage expected is near the stretch of the San Andreas Fault that extends through the fastest growing areas of Southern California, including the Coachella Valley, Inland Empire and Antelope Valley.

At least 10 million people will be exposed to heavy shaking, according to the report.

California's efforts at mitigation have concentrated on life safety and have been largely successful. Because of that, in spite of the large numbers of people in highly shaken areas, deaths are estimated at only 1,800.

Building types known to be vulnerable to damage and collapse, do indeed sustain major damage. All un-reinforced masonry buildings within 15 miles of the San Andreas Fault are completely destroyed. Those that are not retrofitted kill many occupants. Many other older building types without retrofitting contribute to over $33 billion in damage to buildings.

Water implications

The fault offsets all lifelines crossing into Southern California at Cajon Pass (Interstate 15), San Gorgonio Pass (Interstate 10) and along Route 14, including pipelines, power lines, roads, railways, telecommunications and aqueducts.

Dan Masnada, general manager of the Castaic Lake Water Agency which supplies water to four water retailers in the Santa Clarita Valley said contingency plans are in place to offset interruptions to water supply as a result of damaged infrastructure.

"We're more impacted from a quake centered in the north, affecting our water supply from the north," he said Friday when asked about the possible consequences of a 7.8 earthquake.

"If a quake hit in the vicinity of the (San Joaquin) Delta it would likely mean water outages for two years, maybe three years.

"The good news is that we have water in storage in Kern County we would be able to call on to make up for any temporary loss in supply."

Masnada said a quake centered near or in Santa Clarita would likely affect the Los Angeles Aqueduct.

"If there was a failure in the aqueduct, it might stop delivery for four to six months ," he said. "If those failures occurred we would not be able to access the Kern County water supply."

Masnada said the agency does not rely on one source of water.

Last month, city planners assessing safety in Santa Clarita Valley identified a dozen active faults in the Santa Clarita Valley.

A report called the draft version of the safety element of the One Valley One Vision General Plan, was presented by planners as a long-term planning document that will act as a sort of constitution for the Santa Clarita Valley.

The city and county are developing the final stages of the plan, which likely will be adopted in spring 2009.

The report could easily be called One Shaky Valley, One Vision.

Shaky SCV
In it, planners determined that Santa Clarita Valley sits atop numerous active earthquake faults, defined as those which have caused soil displacement within the last 11,000 years.

The epicenters of most of the recorded earthquakes were identified in the report as being west of Interstate 5 and south of Highway 126, in and around the area of Mentryville.

Each of the dozen faults identified was tagged with a prediction of when it was likely to quake again.

The San Andreas Fault, of course, north of Santa Clarita, was listed as a fault that is capable of causing major damage in Santa Clarita. It marks the boundary between the Pacific and North American geological plates.

Other faults, such as the San Fernando and San Gabriel faults, were also listed as nearby faults that could potentially produce earthquakes with magnitudes of more than 6.0.

California is prone to earthquakes because the state straddles two massive plates that make up Earth's crust. Quakes occur when the plates grind past each other along the 800-mile San Andreas and its offshoot faults.

According to some estimates, there is a 30 to 70 percent chance a magnitude 7.5 to 7.8 quake could rupture the southern San Andreas within the next 30 years.

The city's draft safety plan also outlines flood hazard areas throughout the valley, including Placerita Canyon and Sand Canyon.

"In 1994, we were cut off from other valleys," said city spokesman Gail Ortiz, who experienced the Northridge quake firsthand in Santa Clarita. "That's something we have to prepare for."

The Northridge quake revealed a very positive factor, however, which will undoubtedly serve to minimize casualties and damage in the event of a larger one, Ortiz said.

"The way this community pulled together during the Northridge quake was incredible," she said. "You saw neighborhoods helping neighborhoods, that's why Santa Clarita is a success story.

"In the end, it was how the community responded that made a difference."

Santa Clarita learned valuable lessons from the Northridge quake.

"Since ‘94, our building codes have changed dramatically," Ortiz said, citing retro-fitting, reinforcement structures and retaining walls.

Those changes were put to the test last summer when Santa Clarita Valley shook once again.

Shaken, not stirred
On August 9, an earthquake hit Santa Clarita with a magnitude of 4.5 on the Richter Scale.

City officials went out to the Whites Canyon Bridge to see if their post-Northridge plans had worked.

Inspectors with the Sheriff's Department noticed damage to the bridge - some concrete at the bottom had broken off and expansion joints separated a bit - but determined that the valley withstood a significant earthquake.

Shaking from the quake was felt from Santa Barbara to Venice Beach.

In the end, city officials, responding formally through Gail Ortiz, reported: "The expansion joints did what they were supposed to do."

State officials also reported learning from the Northridge experience.

The 1994 quake toppled the I-5/Highway 14 interchange - playing a part in the death of Clarence Wayne Dean, a Los Angeles Police Department motorcycle officer. The interchange had also collapsed during the 1971 quake that originated in Sylmar.

The interchange that exists today was rebuilt and retrofitted and is expected to pass the test of another earthquake, Jeanne Bonfilio, spokeswoman for the California Department of Transportation told The Signal in an interview last year.

"Caltrans feels that all of our bridges are safe," she said.

In recent years, she said at the time, Caltrans has worked to ensure that all bridges and interchanges are retrofitted and in compliance with earthquake-ready standards. That task has been completed in both Los Angeles and Ventura counties, she said.

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