WEST COAST EARTHQUAKE
I was just woke up to a earthquake/tsunami warning at 1:31am Pacific time.The epicentre was 265 kilometers(165 miles) southeast of Kodiak Alaska & registered at 7.9.A tsunami alert was issued for the west coast.Tofino was in the direct path.The primary wave would take around 3 hours to reach us.
The warning & alerts appears to of been called off at 4:30am (pacific). The earthquake was a “Strike Slip” quake & not the damaging “Thrust ” quake! Basically the difference is that a strike slip moves horizontal & a thrust fault moves vertically! When water is displaced vertically thats when a tsunami is created! This earthquake did not have that as it was a “Strike Slip”.
We dodged a bullet this morning!!
Update:(4:30pm same day) – I have thought more about this Tsunami warning & how it has affected everyone? It’s not a matter of “IF” a large subduction quake will happen,It’s more about “WHEN”?
I use to be a Geologist & have studied earthquakes & tsunamis. The earth is composed of very large plates that basically float around crashing into other plates. These areas are called subduction zones.The subduction zone off the west coast of America is called the “Cascadia subduction zone”.It goes from Alaska right down to the southern tip of South America.There are basically two types of plates,oceanic & continental. The oceanic plates are composed of minerals that are denser than the continental crust.So when these two plates meet,the oceanic plate always goes under the less dense continental plate.This denser plate is being “subducted” back into the earths hot core where it’ll remelt. As long as this oceanic plate keeps moving along (about the same speed as your finger nails grow) no problems.It’s when this plate sticks that problems arise.A plate can stick for hundreds of years & suddenly let loose! Which releases an enormous amount of energy! This energy propagates outward to other parts of the earth much like throwing a pebble into a pond,except more 3 dimensional. The earth is rung like a huge bell.This energy reverberates back to it’s origin & we call these “aftershock” waves.
What happened this morning was a release of energy (7.9) from a strike slip fault 280 klicks south of Kodiak island.Not all faults are created equal.A strike slip fault is when two sides move past each other horizontally.These quakes are benign compared to their big bad cousin the “Thrust” fault! A strike slip fault moves horizontally but a thrust fault moves vertically! This vertical movement either pushes the ocean water up or drops it down.Either way this produces a tsunami.(Japanese for harbour wave) How large the tsunami will be is dependant upon how large the energy release was & how close to the surface it was released? A shallow 6.0 can be more deadly than a deeper 7.0 quake if it is right under your city.So how far away the epicentre is also very important!
When there is a large subductive quake,like the boxing day quake of 2004 off of the northern tip of Sumatra,the energy released propagates along the oceans surface as a large tsunami. These events have been going on for millions of years. The last time the Cascadia subduction zone released was January 26th,1700 around 9pm. How do I know that when it was so long ago? A Geologist (Brian Atwater) with the U.S. Geological Survey at Department of Earth and Space Sciences University of Washington figured it out.He was over in Japan discussing earthquakes with peers.He met another fellow Geologist who was Japanese (Kenji Satake). The Japanese keep meticulous earthquake/tsunami records. Satake talked about a tsunami hitting their coast back in 1700 but had no record of a earthquake prior? So this tsunami was nicknamed the “Orphan” tsunami. Because a wave travels around the same speed (960 kph or 600 mph)They calculated back the distance & speed of the tsunami & arrived at the date January 26th,9pm (Pacific)1700.
The “Ghost forest” in Washington State confirmed this date by carbon dating of the dead trees.A large swath of land dropped down enough for the salty ocean water to inundate. As a result the entire forest died from the salt. Atwater found solid evidence to back this theory up.
So the last time the Cascadia subduction zone released was 9pm January 26th,1700.(8.7-9.2 est.) Around 1000 kilometers (620 miles)”unzipped” along the Cascadia & the land dropped around 20 meters(66 feet)! They not only could calculate that but also saw all the other previous tsunamis.There have been 13 other megathrust events in the past.It appears the average length of time is around 500 years. (this is for quakes over 8.0) So set your watches for the year 2200?
The first thing to be affected during a large event of this nature is the power grid.The power will usually go out right away. Than the primary surface wave will rip through cracking the earths surface.This cracking will most assuredly damage the roads.
So………. my long winded explanation comes to this conclusion about Tofino.We have two tsunami sirens.One in Cox bay & the other at the northern end of Chestermans beach near the Wickaninnish Inn.They are hooked into the electrical grid.Neither have any emergency power back up. The power will go out & there will be no warning of a tsunami! (also because the pole base is in sand,the sand will liquify & the poles will most likely fall over) The people who are not killed from the initial shaking will get into their cars & head to higher ground.Only to find a long line up of cars going nowhere!Why? Because the road will have large cracks in it making it impassable!These people will be stuck in the tsunami zone.The best they can do is to abandon their cars & walk into town.The only problem with this option is that the tsunami will only take about twenty minutes to hit.I fear many people relying upon their cars for transport will be caught in this deadly web?
The one thing I saw last night that I fear “may” be a problem is people relying upon their cars for safety. I saw cars parked on front lawns.Anyone who relies on cars to escape the tsunami zone might be getting themselves into a situation?
So in conclusion,the poles need to have back up power & everyone needs to be able bike it………..& we both know that ain’t going to happen.