Wave of tsunami prep heads our way
March 24, 2011
Add this to the list of potential catastrophes that come with living in Southern California: an earthquake-triggered tsunami washing over beaches and harbors and leaving devastation all along the coast.
The nightmarish images of powerful waves buffeting Japan after the March 11 quake there have prompted many to wonder whether the same thing could happen here—and how to escape it if it does. But some Los Angeles experts and planners have been focused on the local tsunami threat long before the first wave hit Japan.
And their assessment of what could be coming our way, and how best to prepare for it, is both simple and complex.
Costas Synolakis, who directs the Tsunami Research Center at USC, said tsunamis triggered by faraway events occur once or more a decade here, and generally pose a relatively minor threat to human safety in Southern California—although they can wreak havoc in the ports by damaging docks and disrupting shipping. A tsunami triggered by a large earthquake in Chile last year did just that, he said—though since it was a Saturday, its impact was less severe than it might have been.
However, a major temblor in the Aleutian earthquake zone in Alaska could pose a significant exception to the general rule about distant-source tsunamis. Such a quake could unleash a powerful tsunami that could endanger both people and property in low-lying coastal communities such as Marina del Rey, Venice and Long Beach, Synolakis said.
To better understand the possible impact of a hypothetical 8.8 quake in the Eastern Aleutian Islands, officials with the U.S. Geological Survey started work in January on their first-ever emergency planning “tsunami scenario” for Southern California. Modeled on the Great California ShakeOut, the scenario, when completed in 2013, will assess how such a tsunami would affect the region economically, environmentally and as an emergency response challenge. It also could serve as the basis for future tsunami response exercises.
Whether they end up causing minor or major damage, tsunamis that originate far away come equipped with one important safety feature: forecasters can see them coming, often hours in advance, allowing time to alert the public and evacuate beach areas likely to be affected.
A “local-source” tsunami would not be so kind. A tsunami triggered by a nearby offshore earthquake could trigger an underwater landslide, causing profound and fast-moving damage all along the Santa Monica Bay—with little or no time for evacuations.
“The landslide event keeps me up more at night because it’s far less predictable,” Synolakis said.
On the upside: it’s an exceptionally rare occurrence, taking place once every 2,000 to 3,000 years, he said.
The Board of Supervisors voted to designate this week “Tsunami Awareness and Preparedness Week” in Los Angeles County, part of a national effort that includes videos like this one.
Planning for any kind of tsunami in Los Angeles County is complicated because there’s no way of knowing in advance which kind will strike.
However, here are some guidelines to improve your odds of staying safe and dry.
Know where you are:
Tsunami “inundation zones” are located all along the coast. Check out this map for a more detailed look at the terrain in various communities. In Marina del Rey, recently-posted signs designate entry and exit points for the tsunami zone, and also point out evacuation routes. “We were fortunate to get one grant to do one [sign] demonstration. We wanted to show it could be done. We just finished it in March,” said Jeff Terry, program manager for the L.A. County Office of Emergency Management.
Make friends with your local emergency services coordinator
With fourteen incorporated cities along the coast, evacuation routes and response plans can vary. In unincorporated Marina del Rey, the latest evacuation map is here.
When the earth moves, get away from the water:
“For most of L.A. County, it’s simply a matter of moving away from the beach,” said Keith Harrison, assistant administrator of the county’s Office of Emergency Management. Resist the temptation to stick around and watch the action; these aren’t ordinary waves.
Don’t expect a siren:
The best source of emergency information will be on radio, TV or online. Los Angeles County emergency response officials said it would be impractical and too expensive to install and maintain enough sirens along the coast to serve as an effective warning system. In addition, the county’s “reverse 911” system, known as Alert L.A., allows authorities to rapidly telephone every land line in the county with emergency information. To be even better plugged in, you can…
Register your cell phone number and e-mail address with Alert L.A.:
Land lines already are covered but take a few minutes to sign up to make sure that official emergency information reaches you wherever you are.
Sometimes the best way out is on foot:
In the event of a fast-approaching local-source tsunami, people in the tsunami zone may have only 5 to 20 minutes to get to higher ground. “Most places you walk up a couple blocks and you’re safe,” Terry said. Added Harrison: “On foot is what we recommend. Don’t get in a car.” For people in a high-rise building, the best response to an extremely fast-moving tsunami could be to climb to a higher floor. (But If there’s time to evacuate, leaving the building and setting out for higher ground would be the safer course.)
The county’s overall tsunami plan was approved in 2006. It’s a good start, but there is still more to do, Harrison said. “One of our goals is to eventually qualify for the “tsunami-ready” designation by NOAA,” he said, referring to the program administered by the National Oceanic and Atmospheric Administration.
Individual county departments have their own plans, and already are working to incorporate insights gained from the recent events in Japan.
“When you look at the video of Japan, it’s apocalyptic. It’s almost surreal, like a movie shoot. It does definitely hit home,” said Santos H. Kreimann, director of the county’s Beaches and Harbors department. “It’s consciousness-raising.”
His department used its new Twitter account to send out messages about the tsunami advisory issued for the Los Angeles coast following the quake in Japan. And it’s been busy ever since with logistical questions such as how best to communicate with and evacuate “live-aboards” who reside on boats in the marina, and figuring out how to relocate the department’s earth-moving equipment far enough from the coast so it will be safe and available for cleanup work after the crisis is over.
“The Japanese event required us to really look at this closer and try to get things done sooner rather than later,” Kreimann said.