“We set off 54 sirens today” said a quietly pleased Robert Purdom from the Washington State Emergency Operations Centre in Camp Murray on the day of the great “Shake out” the bi-annual earthquake drill practiced by millions of Californians for the past few years, and now hundreds of thousands of people from a dozen other US states and even Canada, Italy and New Zealand.
The sirens are one of the principle tools designed to alert the community to a tsunami. And the threat is very real. The western states lie on a variety of fault lines which are quite active. In written history of the North America region there have been numerous very damaging earthquakes and accompanying tsunami. But the alert system now is based on an event which occurred at 9pm, January 26, 1700. There are no written records in the US of this earthquake, but there are in Japan.
“We had a Magnitude 9 rupture of the Cascadia fault line at 9pm on January 26, 1700,” says John Schelling, the Earthquake/Tsunami/Volcano Program Manager. “We know the exact time and date from historical records in Japan. The tsunami washed up in Japan the next day, without warning and flooded fields and washed away homes. They called it the “Orphan Tsunami” as they knew it wasn’t caused by an earthquake in Japan.
An earthquake of that magnitude almost certainly will cause a tsunami along the American coast . The records from tree rings show the Orphan tsunami submerged great areas of coast, and stopped the trees growing. Washington State is preparing its warning system for another event, with the belief they need people to respond within 30 minutes or less.
The warning system is based around getting quality advice about the tsunami, and then using a variety of means to alert residents and emergency agencies. Local familiarisation and training is critical to the success of the system. “We were pleased that we had 700,000 people register to participate in our first Great Earthquake Shake Out” says John. But we hope for many more next year.”
If an earthquake occurs and generates a tsunami the warning system will be activated.
The US Pacific or Alaskan Tsunami monitoring centres operated by The National Weather Service, will generate a report, which is immediately public.
The report will be received at the Washington State Emergency Operations Centre, (EOC) which is responsible for alerting all emergency and response agencies and organisations which are likely to be affected. There is one nuclear power plant in the state.
Simultaneously the EOC will activate the siren system.
“We have about 100 phrases pre-programmed onto a voice chip and the sirens can be programmed to announce anything that the voice chip has available, but we’ve only ever activated it from the EOC for a tsunami siren test” says Telecommunications Field Engineer Robert Purdom. “Each event consists of voice recording as well as the siren sound. We will generate the alerts every few minutes for about 40 minutes.
But although the sirens are tested regularly, they are not considered effective without explanation, or context.
“Every time the siren sounds there must be a combination of siren and voice material,” says John Scheling, Earthquake Program Manager (Mitigation and Recovery)
” We know a siren alone wont make people change their behaviour.”
The announcement begins with the heart stopping words: ”This is not a drill.”
“The sirens are for outdoor use only,” says John Schelling. “They are for people on the beach and in the streets. They won’t be heard indoors, so people have to be aware they might not hear the sirens when a tsunami alert is generated.”
It’s expected the police will drive through towns and neighbourhoods using loud hailers attached to their vehicles warning people of the tsunami.
In addition the “Emergency Alert System” will carry the tsunami warnings to emergency broadcasters, including radio, TV, and digital platforms, and US phone carriers will activate their alerts to mobile devices using CMAS – the Commercial Mobile Alert System.
If the electricity and land lines are damaged by the earthquake, each siren can be activated locally by a county or city emergency agency professional via VHF or UHF radio.
But the awareness messages stress that people must not wait for an alert. “The ground shaking, that’s the warning” says John. “Our messages are straightforward and each has a call to action: “If the ground starts shaking, you run. If you see the sea receding, you run.If you hear a siren, you run.”
The population is expected to seek higher ground, with awareness plans in place to try to raise understanding that the public should not expect to be able to use roads. “An earthquake is likely to damage roads. We expect people will walk or run to higher ground,” says John. The Mayor of Long Beach, which is a marine spit built at water level and with no nearby hills, says “goodness knows which way the warning signs will be pointing after an earthquake.”
Washington State is trying a Japanese idea: “vertical evacuation.” This can include towers, buildings and berms. Vulnerable communities are encouraged to become involved in considering these developments, drawing up plans and seeking federal funding.
“The community is asked if they would like a “vertical evacuation plan” and where they would like the hill or high ground to be built,” says John. This called “Project Safe Haven” and it is an attempt to get the community thinking what kind of structure might help them survive a tsunami.
It might be a berm, reinforced dirt structure, a little like a big river levee, that can be built close to population centres. They could be 10 metres high or more, and will cost $250,000 – to $1 million each. They are an active feature of Japanese tsunami response.
Engaging the whole community in its design and placement results in widespread understanding of what the berm is for; and solid community buy-in. A berm could wrap around a sporting field and create new and useful lines of visibility or it could create an amphitheatre for public events in a community.
But it’s still just a concept: “No vertical evacuation structures exist yet, so we are hoping to build the first one in the U.S. in coming years. Additionally, funding is not yet available, but we hope to use a combination of federal, state, and local funds to implement the results developed by each community.” It’s ambitious,m but the issue calls for an open mind.
“The siren towers cost about $50,000 each, and the cost is shared between state and local counties.” says John.
The Federal Emergency Management Agency in the US has tried to evaluate the cost of natural hazards. In addition to the infrastructure costs, it has discovered that each death from natural hazard results in costs of about $ 5 million. A few hundred thousand dollars for some sirens, and a million or so for a berm, pales into insignificance if they save hundreds or thousands of people.