Thursday, April 10, 2014

Earthquakes on the Pacific Northwest.




Thanks to Sumatra our appreciation of the risk level has seriously jumped.  That makes the exposed coastline extremely vulnerable and should become no build zones.  Fortunately, along Vancouver Island, that has proven largely impossible and particularly unpleasant anyway.

Better the urban heartland is situated in the lee of the actual coastal ridge which acts as a huge damper in the event of a mega quake.  There are still gaps in the defenses, particularly through the Juan de Fuca strait where bad luck can lead to an awful day.

In reality our West Coast is far less vulnerable that the Japanese coastline, simply because we have less targets to actually hit.  The worst area of vulnerability is in river mouths and the odd coastal plain.  Off course it is going to take a tsunami to change the building codes there.

Earthquakes on the Pacific Northwest.


West Coast Earthquakes Mitch Battros writes, “It seems as though the 6.9 magnitude earthquake on March 10, 2014, just off the coast of northern California was just a whimper so people are not to be overly concerned. But you won’t find a single seismologist who would agree with such a notion. In fact, it would appear every seismologist, geologist, and volcanologist is on high alert knowing the potential danger hovering like a mist over the entire west.”

Within minutes of the northern California 6.9 event, modern 3.0 to 4.0 quakes popped up just north of Washington State on the border with Canada. Within this same period, a volcano in Alaska lit-up. On March 11, 2014, a 5.1 mag. quake hit just off the coast of Oregon. Put these events together and you just outlined the Cascadia Subduction Zone; one of the most volatile and dangerous zones along the entire North American continent.

This is not a time to panic, but you would be foolish not to be reasonably prepared. The Pacific Northwest has a 40% chance of being hit by a magnitude 8 or larger earthquake in the next 1 to 50 years. That’s more than double previous estimates of a 10-15% risk.

Great Subduction Zone earthquakes are the largest earthquakes in the world, and can exceed magnitude 9.0. Earthquake size is proportional to fault area, and the Cascadia Subduction Zone is a very long sloping fault that stretches from mid-Vancouver Island to Northern California.   It separates the Juan de Fuca and North American plates. Because of the very large fault area, the Cascadia Subduction Zone could produce a very large earthquake. Thermal and deformation studies indicate that the locked zone is fully locked for 60 kilometers (about 40 miles) downdip from the deformation front.

Further downdip, there is a transition from fully locked to aseismic sliding.  Over the past 10,000 years, there have been 19 earthquakes that extended along most of the margin, stretching from southern Vancouver Island to the Oregon-California border. These would typically be of a magnitude from about 8.7 to 9.2 – really huge earthquakes. Researchers have also determined that there have been 22 additional earthquakes that involved just the southern end of the fault. The last mega-earthquake to strike the Pacific Northwest occurred on Jan. 26, 1700. Written records in Japan document how an ensuing tsunami destroyed that year’s rice crop stored in warehouses.

The clock is ticking on when a major earthquake will next strike, Jay Patton, an OSU doctoral student and a co-author on the study

When it hits: Violent shaking may last two minutes or more. The ocean floor will drop, most likely creating a tsunami that will strike long stretches of the coast. The central Olympic peninsula will suddenly rise, while some continue to arrive for hours. - coastal areas will sink below sea level.

If an earthquake occurs at or near coastlines:  - Drop, cover and hold. Get under a sturdy object and hold on. Watch for falling objects. - As soon as the shaking is over, move to high ground or inland. Do not wait for an official warning. - Stay away from the coastal waters. Waves may

Listen to your local radio station for an official “All Clear” notice before returning to the coastal area. - Be alert for aftershocks. Protect yourself and your family:  - Develop a family disaster plan. Everyone needs to know what to do on their own to protect themselves from an earthquake. - Be familiar with local Emergency Management earthquake and tsunami plans. Know where to go to survive a tsunami. - Be prepared to survive on your own for a minimum of three days. - Prepare a disaster supply kit for your home, automobile and work. Take a first aid course and learn survival skills. Knowledge is your greatest defense against potential disaster.


ECM survival guide: http://earthchangesmedia.com/survival_guide March 2014 Thanks to Mitch Battros

1 comment:

Anonymous said...

All studies of the Cascadia fault indicate shaking on, or about every two hundred years. If the trend continues, "we are overdue" for some major movement along this fault line.

Everyone... and I do mean everyone should have drinking water, food, and seasonal clothing stored in their vehicles, home, and work.

Do Not depend on others to save or rescue you in times of disaster. You must be alert to conditions surrounding you at all time. Where you can, carry sufficient supplies that you can help others when necessary. Expect that "most" people will not be ready for the shake.

Those in low lying coastal areas need to know "where the high ground is." DO NOT go searching on the beach when the tide goes out... folks, it will come back in, and you can't run that fast.

Good luck, just 'cause you are inland does not mean you are totally safe... BE PREPARED.