With the 50th anniversary of the devastating tsunami that killed a dozen people in Crescent City approaching, state and federal agencies have teamed up to create a preparedness playbook for each of California’s nearly 130 harbors.
Striking on March 27, 1964, the magnitude-9.2 Great Alaska Earthquake — also known as the Good Friday Earthquake — resulted in California’s deadliest tsunami, which killed 15 people on the West Coast and caused severe damage to several state harbors.
Rick Wilson of the California Geological Survey’s tsunami program said the state has a long history with the devastating waves.
”Since the 1800s, we’ve had over 100 tsunamis observed in California,” Wilson said. “Although most have been small, there have been 13 large enough to cause damage, especially to harbors.”
In order to prepare harbors for future events, the site-specific playbooks — created by the state geological survey in collaboration with the California Office of Emergency Services, the Federal Emergency Management Agency and several state universities, including Humboldt State University — will provide maps that lay out high-hazard areas under a number of different tsunami scenarios.
For each scenario, a corresponding response strategy will be given — whether it’s warning boats to remain offshore or preventing docks from being lifted off pilings.
Though two recent tsunamis — caused by the 2010 earthquake off the coast of Chile and the 2011 Tohoku earthquake off the coast of Japan — caused millions of dollars worth of damage at Crescent City and other California harbors, the events also created a scientific opportunity.
”Before those two events, we really didn’t have information about tsunamis along our coast,” Wilson said. “… It was priceless.”
By obtaining video and data collected during the tsunamis, Wilson said they were able analyze currents and resulting effects, which “gave us the ability to model bigger scenarios” and “validate numerical models” that can be applied to various locations.
Pilot studies have already been completed for five harbors, including the newly renovated Crescent City Harbor. After being heavily damaged in the 2011 tsunami, the harbor underwent a nearly $50 million rebuilding project to make it the West Coast’s first tsunami-resistant port. A ribbon-cutting ceremony is scheduled for 1 p.m. today.
Humboldt State University Geology Department professor Lori Dengler said the harbor’s location and surrounding geography make it a “tsunami magnet.”
”It’s the second most western point in California, losing to Cape Mendocino,” Dengler wrote in an email. “Unlike Cape Mendocino, Crescent City is low-lying and the only relatively populated, exposed community north of Mendocino County.”
Dengler said the south-facing harbor “traps tsunami energy” from the bay, as well as the secondary waves that can linger for several days.
Federal Emergency Management Agency Senior Civil Engineer Ed Curtis said he was “proud” that his agency was funding a project that will help “minimize future losses and enable communities to get back on their feet quicker.”
”Previously, there hasn’t been the ability or the science available to analyze this risk,” Curtis said.
Wilson said that the information in the playbooks will mostly pertain to tsunamis triggered by earthquakes far away.
”These products that we’re working on are for distance-source tsunamis,” Wilson said. “With a distance tsunami, we could have up to several hours to prepare.”
Looking further into the future, the tsunami strategy guides also provide the framework and recommendations for tsunami-equipped harbor infrastructure, as well as land use planning.
”These harbors can then determine what areas are most prone to tsunamis,” Wilson said. “When they put together plans or designs, they can make them more resistant.”
With tsunami preparedness week beginning March 23, Kevin Miller, head of the California Office of Emergency Services’ tsunami program, said it is important that people “trigger their muscle memory” when near-shore quakes strike — as a tsunami could follow in a matter of minutes.
”We encourage people to take a look at their local maps and to know your zone,” Miller said.
All tsunami playbooks are expected to be completed by the end of this year, or early 2015, according to Wilson.
On the Web:
More information on tsunami preparedness week can be found at http://nthmp.tsunami.gov/tpw/tsunami-preparedness-week.html
Tsunami evacuation maps for Humboldt County can be found at www.humboldt.edu/rctwg