Monday, January 09, 2012
Newly discovered earthquake fault lines mean Valley is on shakier ground than originally thought
Yakima Herald-Republic
YAKIMA, Wash. — The scenic ridges that line the Yakima Valley and much of Central Washington have long been admired and touted as part of the region's charm.
Turns out they come with a potential price.
"Every one of those mountains has a fault or two associated with them," said Brian Sherrod, a geologist with the U.S. Geological Survey studying Central Washington faults. "And almost all of them haven't had much work done on them yet."
They include everything from the Yakima, Manastash, Umtanum and Toppenish ridges to Heaven Hills and Saddle and Rattlesnake mountains near Hanford. The information being gathered on them by Sherrod and other geologists is not only helping people understand the likelihood of an earthquake in our region, it's showing just how connected the state's tectonics really are.
Sherrod said recently geologists have been able to map a series of fault lines stretching across the Cascades -- including a group of faults along ridges between Yakima and Ellensburg that connect to faults as far away as Vancouver Island. Their discoveries are changing the way geologists see the relationships between earthquakes on different sides of the state.
That is to say, what happens on one side of the Cascades could mean something down the line for the other, but geologists still have a lot of work to do to understand the likelihood and significance of these discoveries. The biggest task is studying the history of the faults using advanced technologies on the ground and through aerial research to learn whether they're active and what they're capable of doing.
The easiest way to learn if a fault is active is when it produces an earthquake, Sherrod says, the rest is a matter of time and research. It's barely known for many of the Central Washington fault lines when they last had activity, much less their potential for acting up again.
"It's something that's going to take a long time to figure out," said Sherrod, who noted he began his research using work done by geologists in the 1970s and '80s. "I view this as something I'll be working on the rest of my career."
Earthquakes remain more frequent on the westside, with more than 20 small quakes in the last month that registered less than 2.0 on the Richter scale. Experts have long warned of the eventual likelihood of a potentially catastrophic earthquake in the Puget Sound region. However, the state's biggest earthquake last year registered 4.7 in Okanogan County, said John Schelling, the earthquake management program manager for the state Emergency Management Division.
"It continues the need for recognition that no matter where you are in Washington, earthquakes are a reality," Schelling said.
Geologists walk a fine line in keeping the public prepared for a disaster without coming across as something of a Chicken Little. None of the new information about Central Washington suggests a disaster is imminent, but Schelling says the trouble with earthquakes is you can learn where they might happen but never forecast when.
"Looking at a map you can argue probabilitywise (a major earthquake) is not going to happen," Schelling said. "But that doesn't mean it can't happen tomorrow."
The largest earthquake recorded within 100 miles of Yakima was a 5.5 magnitude quake in 1981, according to the Geological Survey.
Only four small earthquakes have been recorded in recent weeks east of the Cascades, according to the Pacific Northwest Seismic Network. Three of them were along the Columbia River between Chelan and Wenatchee -- the biggest and most recent registering at 2.4 on Wednesday. On Christmas, a 0.5 magnitude quake was recorded along the Columbia River just north of Richland. Only at about magnitude 3 or above are earthquakes strong enough to be felt by people.
The new information coming out about fault lines in the region also lets local emergency response officials gauge the level of response that may be necessary for such a natural disaster, Schelling said, though he doesn't expect many changes to emergency preparedness plans already in place.
Jim Hall, director of the Yakima County Department of Emergency Management Services, said officials take an "all hazard" approach and only specially prepare for seasonal events, such as flooding or other potential emergencies that can be forecasted out.
The plan in any situation is to assess the damage, respond to life and safety issues and plot out a course to get the community back to the way it was before the event, Hall said.
The new information "hasn't changed our plans, we're just more aware of the hazard," Hall said. "An earthquake is unique, but we would respond to that in the same way as we would anything."
Hall said local agencies have to be prepared for a response even if a major earthquake hits west of the Cascades. An event that disrupts transportation or commerce in the Puget Sound region could prove costly for the Yakima area, which Hall said gets about 75 percent to 80 percent of food products and fuel transported from the westside.
Hall said state Emergency Management and the Pacific Northwest Seismic Network share information directly so that when an earthquake strikes anywhere that information is funneled to local agencies in a matter of minutes.
Despite the low odds of a major earthquake in Yakima, Hall worries that a number of buildings in the area are outdated and not up to withstand significant seismic activity.
He didn't want to raise any alarms, but said it's important people know about the possibilities and don't discount any of them.
"Mother Nature has a way of doing her own thing," Hall said.
--
Zenguins!
Vei8-Volcanoes of the World Webcams
Roxxfoxx~~Adventures in Geology
Penguin News Today
Penguinology: The Science of Penguins
Gentoo Penguins of Gars O'Higgins Station, Antarctica
Canis lupus 101
Dances with Werewolves
Through Golden Eyes
__._,_.___
No comments:
Post a Comment