Tsunamis Could Hit Pacific Coast
Giant tidal waves like the one that devastated Papua New Guinea have also struck the Pacific United States in the past.
Don Hull, an Oregon state geologist, said the danger may be increasing for coastal areas of Oregon, Washington, and northern California.
"Since the New Guinea event, people have asked repeatedly if it could happen here," Hull said Tuesday. "The answer is yes."
The Cascadia subduction zone, a offshore fault stretching along the Northwest coast, poses a threat of offshore earthquakes that can generate the giant sea waves, called tsunamis.
A tsunami slammed the shore of Papua New Guinea on July 17 as a result of an offshore quake. The 23-foot water wall killed almsot 2,000 people and left many others injured and homeless.
In the past, there have been earthquakes generated from the Cascadia fault, with an estimated recurrence rate of 300 to 600 years, Hull said. The last such quake was in January of 1700.
Hull's warning came from a briefing on tsunamis organized by the National Oceanic and Atmospheric Administration. The organization is responsible for studying and issuing warnings of great waves.
Besides earthquakes, tsunamis can be caused by undersea landslides and volcanoes, said Charles McCreery of the Pacific Tsunami Warning Center in Hawaii. These waves can travel across the Pacific in 24 hours but may be hardly noticable in midocean. But, unlike other waves, tsunamis are deep. So when they approach the shore, the rising bottom causes them to mound up.
"In the best case, they come ashore as a rapidly rising tide. In the worst case, they come as a wall of water, followed by a flood," McCreery said. They also come as a series of waves.
The NOAA warning centers receive earthquake information from 100 seismic sensors as well as tide gauges, and buoys, said Thomas Sokolowksi, from the Alaska Tsunami Warning Center in Palmer. But it can take anywhere from 8 to 14 minutes to get enough data to issue a warning. If the quake is nearby (as in Papua New Guinea), there may not be enough time.
"There is no way, at this time, to predict tsunami-generating earthquakes," Sokolowski said.