JEFFREY BROWN: Recent events in Japan have, of course, sparked new concerns and warnings about the safety of cities, buildings, and nuclear plants in this country. One focus: the risks of a tsunami along the West Coast.
NewsHour correspondent Spencer Michels reports.
SPENCER MICHELS: The tsunami that devastated Japan has raised new fears in the United States that a powerful earthquake-triggered wave could wreak havoc in North America as well.
And in fact, those fears are well-grounded, according to Eddie Bernard, who ran the government’s tsunami research center for decades and is still active. Even he was astounded by what he learned, that once ashore, the tsunami reached a height of 130 feet above sea level.
DR. EDDIE BERNARD, National Oceanic and Atmospheric Administration: Never have I seen anything this widespread. I mean, the amount of debris, meters deep, bodies buried in within all this stuff, I never expected to see anything of this massive magnitude. So, I think this is a very big wakeup call for the United States, because we have a similar geological feature off our coast.
SPENCER MICHELS: That geological feature runs from Vancouver Island to Northern California. It’s called the Cascadia fault or subduction zone, where a collision of large rigid plates in the Earth’s surface caused a huge earthquake in 1700, and scientists say it is due to happen again.
Gary Griggs, director of the Institute of Marine Sciences at the University of California at Santa Cruz, has studied subduction zones.
GARY GRIGGS, University of California at Santa Cruz: One of those plates, the Pacific is diving down beneath the continent. And, as it goes down, it’s actually dragging on the overlying layer. It’s hung up. It’s stuck.
Every 100 or 200 years, that’ll break loose. And what typically happens is, the upper plate will sort of rebound. It will bounce back up. And that displaces a huge amount of water. And that happens all around the Pacific intermittently.
SPENCER MICHELS: If the quake happened close to shore, the tsunami would arrive very quickly, as it did in Japan, and cause enormous devastation.
DR. EDDIE BERNARD: Ten percent of the damage was caused by the earthquake, but the tsunami that followed did 90 percent of the damage and killed 99 percent of the people.
SPENCER MICHELS: But a close-in tsunami is not the only threat worrying scientists. In Santa Cruz, Calif., the Japanese tsunami was felt when a five- or six-foot wave roared into the harbor, sunk 20 boats, damaged 100, and broke docks, nearly 6,000 miles from Japan.
And that underscored another threat that concerns scientists: tsunamis that happen thousands of miles away.
RICK WILSON, California Department of Conservation: Got the mast stuck underneath the boat.
SPENCER MICHELS: Rick Wilson, a geologist for California’s Department of Conservation, says it could have been much worse.
RICK WILSON: In this area right here, we could — in a worst-case scenario, we could expect waves up to 30-feet high, and it would flood this entire valley right here.
SPENCER MICHELS: And what — what makes you think a 30-foot wave is possible here and all that damage?
RICK WILSON: Well, because we run numerical models on different scenarios. And we simulate these tsunamis coming across the Pacific and striking California’s coast. And from those scenarios, we’re able to say, yes, a 30-foot wave could be possible here.
BRUCE JAFFE, U.S. Geological Survey: Most of the damage was in the upper harbor.
RICK WILSON: Right.
SPENCER MICHELS: Wilson and colleagues, including oceanographer Bruce Jaffe, met in a restaurant at the harbor to go over damage reports and analyze what happened.
BRUCE JAFFE: You can see where the energy is going to be focused, the red areas here.
SPENCER MICHELS: Jaffe is with the U.S. Geological Survey and watched with intense personal interest the Japanese tsunami.
BRUCE JAFFE: I was not able to sleep that entire night. I felt it was my duty as a scientist to track what was going on and to let people know as much as possible what I thought the risks were.
SPENCER MICHELS: Jaffe says that since the Indonesia tsunami of 2004, the number of tsunami researchers has more than doubled. Looking at geological deposits, they can trace historically the intensity and damage of past tsunamis. And while they haven’t figured out how to prevent the big waves and may never, they have figured out how to predict where the waves will travel and with what intensity and speed once an earthquake occurs.
On the day of the Japanese quake, scientists were able to warn people in Hawaii of impending danger.
DR. EDDIE BERNARD: We zero in on one community on the island of Maui. We can see that the forecast for this island seven hours before it struck the islands was for some small flooding and some very strong currents in this harbor.
SPENCER MICHELS: Such scientific calculations are valuable, says longtime tsunami researcher Gary Griggs. He’s looking into the recent tsunami.
GARY GRIGGS: We were accurate within 15 minutes or so. Knowing the height of those waves, and what the topography of the land is, we have some idea about which areas will be inundated or flooded. So, I think that’s significant progress. It isn’t a mystery anymore.
SPENCER MICHELS: Here at the Tsunami Research Center in Seattle, they’re trying to use what they have learned scientifically to lessen the impact of tsunamis. And buoys like these are a key part of that effort.
For 25 years, scientists have been designing and redesigning these floating platforms toward a simple end: to detect a tsunami by measuring changes in water pressure on the ocean floor near a large earthquake. Getting the signal from the sensor up to the buoy was a major challenge, says Chris Meinig, engineering director of the lab, part of the National Oceanic and Atmospheric Administration.
CHRIS MEINIG, National Oceanic and Atmospheric Administration: There’s no wire connecting this. It sends the signals acoustically from the bottom pressure gauge up through the buoy in upwards of seven kilometers of water depth.
SPENCER MICHELS: Then the buoy sends a signal to a satellite, which relays the alarm to a tsunami warning center, part of the Weather Service.
When the recent quake struck, Meinig says, the data from the buoys was vital across the ocean.
CHRIS MEINIG: And what we were able to do for the first time is really ingest a mega-earthquake data from — that we measured the ocean from the tsunami wave into the forecast models, and produce site-specific forecasts. And we could do that and give those communities six to 10 hours, which is enough time.
SPENCER MICHELS: But this sophisticated warning system breaks down, as it did in Japan, where beachfront areas lie close to the earthquake’s epicenter, and the tsunami roars ashore within a few minutes.
That’s why the closeness of the subduction zone to the Pacific Northwest is so scary.
DR. EDDIE BERNARD: Probably, we’re at some physical limits of what a warning system, from a technological standpoint, can do. And that’s where we cross the threshold into education and preparedness.
I think the Japanese tsunami of March 11, 2011, gave us that clue. We need to focus our energies on the local tsunami problem, and that is, what types of structures should be built? How should they be built?
SPENCER MICHELS: Along the West Coast, unlike in Japan, there are no tsunami shelters, though one city, Cannon Beach, Ore., is considering building one that would double as a city hall.
Local communities have put up signs for tsunami evacuation routes, but they fear gridlock on the roads. The problem is, says U.C.’s Griggs, the public doesn’t stay focused on tsunami preparation for long.
GARY GRIGGS: Legislation get passed. People get on the alert. They — you know, they store their gallon of water and their flashlight, and then we have this thing I call collective amnesia. We forget about it. I think we have this window in which we can respond right after a disaster, and then it’s gone again.
SPENCER MICHELS: Rebuilding and avoiding dangerous areas may not be in the cards. So for coastal residents, the most practical advice when faced with an unexpected tsunami may be to head for the hills as fast as possible.