The State of Oregon is encouraged to prepare for a 9.0 earthquake on the Cascadia Subduction Zone in the Pacific Ocean that would kill more than 10,000 people, mostly along the coast, and leave many communities without water, power, or other resources for months. Wikimedia Commons/ Walter Siegmund
A new report to the Oregon State Legislature details the risks from a powerful earthquake on the Cascadia Subduction Zone, and outlines a 50-year plan to build infrastructure resilience.
March 26, 2013—A 9.0 earthquake on the Cascadia Subduction Zone in the Pacific Ocean, and the resulting tsunami, could kill more than 10,000 people, mostly in western Oregon and along the Oregon shoreline, in less than an hour. This would leave coastal communities cut off from electricity for three to six months and drinking water and sewer service for a year or more. Those are some of the startling findings of a new report to the Oregon state legislature.
The report—The Oregon Resilience Plan: Reducing Risk and Improving Recovery for the Next Cascadia Earthquake and Tsunami—was presented to House and Senate committees of the 77th Legislative Assembly by the Oregon Seismic Safety Policy Advisory Commission (OSSPAC) on March 14.
The report paints a sobering picture: an estimated $32 billion in economic losses from an earthquake and tsunami and approximately 24,000 buildings destroyed. Officials would face the task of management and disposal of 10 million tons of debris.
The report notes that geologists have developed a 10,000-year record for the fault, finding that it produces very strong earthquakes, ranging from magnitude 8.3 to 9.3. It has been 313 years since an estimated 9.0 temblor was unleashed on January 26, 1700. The likelihood of a magnitude 8 or larger over the next 50 years is estimated to be around 40 percent. Current pressure building on the fault is causing the Oregon coast to move east several inches per year.
During an earthquake, portions of the Oregon coastline could drop as much as 5 ft. Residents would have as little as 15 minutes warning to evacuate the coast and low-lying areas to escape the swiftly moving water—traveling as fast as 500 mph in the open sea.
“There is no scientific doubt that another great subduction earthquake will strike the Pacific Northwest; the questions now are how soon, how large, and how destructive that earthquake will be,” notes the report.
The committee found that although Oregon’s political leaders are addressing the problem, the state is still unprepared for a massive earthquake on the subduction zone. It wasn’t until 1984 that geologists began to fully understand the risks the fault posed. The state dramatically strengthened building codes in 1993 to address the threat, but the majority of buildings in the state predate that code change, the report notes.
The infrastructure systems are vulnerable, and the lengthy projected times to return energy and potable water services to communities greatly exceeds the amount of time most small businesses can remain financially viable without that critical infrastructure.
“The business community only can tolerate two to four weeks of business disruption. There is a huge gap between what the community wants and in reality what infrastructure services we can provide,” says Kent Yu, Ph.D., P.E., S.E., M.ASCE, chair of the OSSPAC and a principal in the Portland office of Degenkolb Engineers.
“If you look at our economy, a lot of small businesses are very vulnerable,” Yu says. “They are supporting somewhere between 50 and 60 percent of the workforce in Oregon. They are not prepared. If we cannot provide the services they are looking for, they are going to close, relocate, or leave the state entirely. Even large businesses with the resources to withstand extended service interruptions will be heavily affected by the impact on smaller firms (that is, their suppliers, service providers, et cetera). ”
The OSSPAC divided into eight task groups, each focusing on a different aspect: likely earthquake scenarios, business and workforce continuity issues, the unique impacts to coastal communities, the preparedness of critical buildings, transportation infrastructure, energy infrastructure, water and wastewater treatment systems, and the communications network.
The commission developed four overarching recommendations for the state. The first recommendation is for the state to conduct comprehensive seismic risk assessments and develop mitigation plans for critical buildings, transportation infrastructure, energy systems, and water and wastewater treatment systems.
The commission recommends the creation of a capital investment program to fund seismic rehabilitation of schools, colleges, and emergency facilities, seismically upgrade key transportation routes, and establish a State Resilience Office to coordinate those efforts.
The OSSPAC also recommends that the state develop an incentive package to encourage private sector seismic resilience efforts.
Finally, the commission recommends that the state revise several public policies. The state would encourage residents to plan for two or more weeks without water or power. Standards would be developed for temporary bridges and their deployment. And as a public education measure, the state would adopt a two-tiered rating system that informs residents of the days or months they can expect to wait for relief after a disaster and the days or months they can expect until restoration of public services reaches the 90 percent threshold.
The commission recommended a targeted, phased approach over 50 years to build greater resilience into Oregon’s critical infrastructure. Yu said this work would focus on creating robust cores in the transportation and utility infrastructure. The work would be prioritized and could be added to infrastructure renovation or replacement projects.
“We are realistic,” Yu says, using water and wastewater infrastructure as an example. “We cannot make sure every pipe is going to work. It’s impossible. We are willing to accept some damage. We want to make sure we have a critical backbone in place.”
“We want to make sure the main transmission facility, pipes, pump stations, and reservoirs are operational,” Yu explains. “And we also want to make sure the water supply to critical facilities such as hospitals and major manufacturing facilities is available. We want to make sure that water for fire suppression at key supply points is available. Not every single fire hydrant will have water. No. But we want to make sure that at critical supply locations we have water so that we can suppress fire after a disaster.”
The report presents recent earthquake recovery successes in Chile and Japan as resilience models the state could emulate.
“We firmly believe in smart planning,” Yu says. “Today, we know the extent of the tsunami inundation zone. Why can’t we do the planning before the tsunami hits?”
The Oregon Resilience Plan full report, by chapter, is available for download.