By Jim Hoover
For those who are buying potassium iodide tablets, there is another reason to panic.
The Cascadia megaquake is long overdue.
Run for your lives!!
Well, wait a minute. This is only if you live in the coastal region of northern California, Oregon, Washington, or Western Canada.
The rest of you can take your potassium iodide pills.
But hold on for now. This is only fear-speak, something angst-mongerers do.
“PANIC!” said the front-page headlines of New York Daily News about a week ago.
Don’t panic, but buy your pills only if there is a possible exposure to radiation above safety limits. It would take a large explosion that releases a significant fallout cloud to signal any danger for the Pacific coast, and that would take several days to reach our shores.
But getting back to Cascadia, some twelve kilometers beneath the seafloor off the Pacific Coast from Northern California to the coast of Vancouver, a subduction fault zone lies. You can see it on the map above \˃ with the inclusion line with the arrows marking the 600 mile long subduction zone. \˃
It is a long sloping fault that separates the Juan de Fuca and North American plates that is 600 miles long and 30 miles wide, and a mere 40 miles from downtown Seattle.
The last megaquake of over 9 on the Richter scale hit Cascadia in 1700 CE, followed by a huge tsunami on our northern Pacific coast, but also across the Pacific on Japanese shores some hours later.
Such a quake would shake for a full 5 minutes, toppling at least a few of Seattle’s high rises, followed by a tsunami of up to 50 feet.
When is the next one due?
Scientists say that they occur on that fault-line — megaquakes,that is — every 170-200 years, based on past history.
Did we say that the last one was over 300 years ago?
In case you don’t believe me, GPS scientists have measured an uneven (I said uneven) movement toward the East of the North American plate by 39 feet since 1700 when the last one hit. That “uneven” means that the two subduction crusts have been locked for those 300 years.
Yipes! What if a continent-size rocky shell were pushing under your crust for 300 years?
Wouldn’t you eventually pop up?
A 9.0 makes California’s “Big One” look rather small. Wouldn’t you say? Our big one is considered to be anything over 6.7. Even the San Francisco quake of 1906 was only 8.3.
On the logarithmic scale a 9.0 is 1000 times more destructive than a 7.0. Something that snaps over a 600 mile fault line will shake you for over 5 minutes.
But before you Easterners get too puffed up with betterment, you have the New Madrid Fault. It caused a quake of over 8 magnitude when Thomas Jefferson was president. It runs through parts of Missouri and Tennessee and was felt as far away as Washington DC.
In fact a few years ago West Salem, Illinois had one that registered 5.3.
And you have your major storms, tornadoes and hurricanes too.
So we can all panic on queue with the periodic fear-stoking.
Give it to us, NY Daily News medias of the world!!
