Deakin Communicating Science 2016

EES 200/101

The Overdue Catastrophes of Earth: Earthquake of the Pacific North West

Consecutive shockwaves radiated from the heart of the rift, shuddering the city to its core. The San Andreas fault roared to life, destroying all that stood in it’s path. The city of San Francisco fell to it’s knees defeated. 9.6, the scale read as Dwayne Johnson scanned the wreckage of the Golden Gate Bridge.

Admittedly, I have neglected to add the movie ‘San Andreas’ to my repertoire (thanks IMDB for filling me in), but the picture painted is quite clear should the San Andreas fault shake California with “The Big One”. It’s all quite dramatic, however, the perpetually rumored ‘Earthquake of the Century’ is actually NOT on the verge of unleashing hell on California.

But how? Hollywood told me otherwise?

The aptitude capacity on the San Andreas fault – on of the most extensively studied, has an upper limit for its capacity of destruction at 8.2 on the Richter scale. Devastating? Yes, but nothing compared to the potential of the Cascadia Subduction almost at breaking point.

Where’s that?

CascadiaSubductionZone2.jpg

Fig.1 Cascadia Subduction Zone (USGS)

A bit further north lies a fault line known as the Cascadia Subduction Zone (Sounds familiar? Think Cascade Mountain region line), running off the Pacific North West coast from the top of California and terminating at Vancouver Island, Canada

Subduction Zone?

This zone occurs when one of the earth’s tectonic plates (big ol’ slab of crust) slides under – ‘subducts’ another. A seemingly slow paced and minor riffle, but occasionally at the collision point a “minor riffle” becomes a gross understatement. Especially in the case of the Cascadia Zone.

Here’s where the problem lies – The North American plate is refusing to subduct at the collision edge and under the neighboring Juan De Fuca plate. Instead, North America has decided to jam itself head on into the other plate.

The consequences are that the North American plate is bulging upwar

Screen Shot 2016-05-11 at 5.41.59 PM

Fig 2. Subduction: North America Vs Juan De Fuca (USGS)

d and compressing eastward at 30-40ml per year which is at an alarming rate. This is caused by the youthful and malleable abilities of the plate being super elastic. Like all pieces of elastic, there is a limit to how far it can be stretched.

 

And so the unbudgeable mass of a whole freaking continent is likely to snap back. Yikes.

The impact?

Should the Southern part of the subduction zone subsid, an earthquake of 8.0-8.6 will occur (San Andreas potential equivalent). Should the complete zone give way, the magnitude will be recorded as somewhere between 8.7 and 9.2. That’s the very big one.

A full margin collapse could prove to be the worst natural disaster in the history of North America.

The northwest edge from California to Canada and the continental shelf to the Cascade range, could drop by as much as 2m and rebound back to the west 10-30m. Causing a loss of centuries worth of compression within minutes. 

This shift undoubtable will displace an incredible amount of ocean water. A humongous coastal surge has the speed to reach shore on average in 15 minutes following the earthquake. There is no doubt that the region of approximately 65,000 square kilometres will be obliterated. Further estimates conclude that nearly 13,000 people with perish in the Earthquake/ Tsunami combo with another 27,000 injured. Millions of displaced people will try to seek refuge and try rebuild their lives.

This overdue disaster is calculated to strike within the next 300 years. It seems far away now at best, but a harsh reality to accept for our future generations in the direct line of fire.

Thinking of booking a ticket to Australia now? Anyone?

 

Sources:
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This entry was posted on May 11, 2016 by in Uncategorized.

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