The
INSIDE Is spring here?
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Nat’l Monument positions
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Sea lion rescue
Anne Willis photo
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VOLUME 38, NUMBER 8 • FEBRUARY 24, 2015
How to prepare for a tsunami on the islands By Cali Bagby Weekly editor
Big tsunamis come every 300 to 600 years and the last one for the west coast was 315 years ago, which means a disaster could be headed our way. “There are a number of quake scenarios that could impact the islands,” said Brendan Cowan, director of the county’s department of emergency management. “All are real, and could potentially happen tomorrow.” The good news is that when the tsunami comes islanders can be ready. According to the DEM’s new webpage entitled Common Tsunami Questions, “In the most likely scenario, San Juan County will have plenty of warning (due to the large quake we
feel) before a tsunami in the form of an extremely large earthquake.” The tsunami could come in 45 minutes or less after a large quake, which is defined as rating 5.0 or greater on the logarithmic scale. Although 9.0 would be incomprehensibly larger than a 5.0, Cowan describes both as large enough to cause concern. “In general, the larger the quake, the bigger the tsunami, but there’s an almost limitless number of scenarios that could cause a tsunami,” he said. “By focusing on the 9.0 quake with our maps, we’re looking at the most studied/best understood and one of the potentially most damaging events.” What complicates matters is that not all quakes
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cause tsunamis. The quake has to lift the sea floor to be followed by a tsunami, and according to Cowan, the majority of undersea quakes don’t cause a tsunami. To understand how likely it is that a tsunami is headed our way one has to look back to 1700 – and a forest submerged by salt water. For many years quake experts believed that the closest fault, the Cascadia subduction zone, was safely aseismic. When they found mysteriously sunken Northwest forests that appeared to have been killed by salt intrusion in the year 1700, their conclusion changed. It turns out that the eastward-moving Juan de Fuca tectonic plate is not sliding smoothly beneath the westward-moving North American plate; instead, it’s bunching up, building up tremendous pressure that scientists believe will eventually let loose in the space of a few minutes. If the fault’s five segments all “go off” at once, a 9.0-plus magnitude megaquake could launch twin killer tsunamis, one toward the Pacific Coast and one toward Japan. Seismologists now believe that’s what caused what
Contributed photo
The map created by county geographic information system staff, shows levels of tsunami inundation on Lopez Island. Orange represents 16 - 18 feet, dark pink 14-16, purple 4 - 6 and blue 0 - 2. is known as the Orphan Tsunami, which killed 1,000 people in 1700. When the plates finally slipped free, the pent-up Pacific Coast dropped by about five feet, submerging the forest. Predictions as to when the plates will roar again vary, but the Washington State Department of Natural Resource Chief Hazards Geologist Tim Walsh has said six past earthquakes affecting Washington have occurred 500 to 550 years
apart. The year 2015 will make it 315 years and counting since the last big event. Canadian and U.S. experts have offered probabilities of 14 to 29 percent that the event could occur during the next 50 years.
Where to run?
The DEM just released an online map tool that allows islanders to view the tsunami risk following a Cascadia quake. You can see the maps at http:// sjcgis.org/tsunami-inunda-
Lopez School Drama Club ✧
presents ✧
10th Annual Festival of One-Act Plays
Dinner Theatre at the Galley!
Wednesday, Thursday, Friday March 4, 5, 6 Dinner from 5pm; Show at 6:45pm Call the Galley for reservations:
Dinner and Show: $30 Show only: $10 at the door (available 6:30 pm)
tion/. According to Cowan, this is the first time that the department has had a datadriven picture of how the tsunami will affect San Juan County. This data has been collected over the span of 10 years. Prior to that, predictions of the tsunami effects were based on speculation or interpretation from work done on either a larger scale or for locations other than the San Juans. Since the tsunami hit Japan in March 2011, Cowan said there has been a lot of confusion in the community about tsunami risks. “The very idea of them can understandably bring up strong emotions, likely due to the extremely vivid images we’ve seen from Japan and the Indian Ocean,” he said. Some of the most common misunderstandings Cowan hears from the public is that what happened in Japan would be replicated here, and that if you know it’s coming you should get in a boat and ride it out. Apparently jumping in SEE TSUNAMI, PAGE 4