Earthquake near Vancouver, Canada

[CuriousByNature]

Hi everyone,

I just got off the phone with my uncle who lives near Vancouver, BC.   There was a 5.1 or 5.2 earthquake about 40 miles northwest of the city earlier today.  He said it was the biggest shake he's felt in decades and he was very unsettled by it.  There was no damage in his area, thankfully, and it was not large enough to cause any tsunamis.

I used to live in Vancouver and in the surrounding areas quite a while back, but I think I only felt a small earthquake once, and that one was quite far south and closer to Seattle, if I recall.  Anyway, I'm not sure if anyone on the forum lives in the BC Lower Mainland or on Vancouver Island, but if so, I hope everyone is fine.  5.1 or 5.2 probably didn't cause any damage, but I expect it could have been pretty alarming.

 

 

[Luv2play]

As I understand it, both Vancouver and LA are  on fault lines that at some point will result in the Big One. I think small earthquakes are to be welcomed as they relieve the tension between the tectonic plates that underly the region. 

[CuriousByNature]

3 hours ago, Luv2play said:

As I understand it, both Vancouver and LA are  on fault lines that at some point will result in the Big One. I think small earthquakes are to be welcomed as they relieve the tension between the tectonic plates that underly the region. 

Yes, I read a lot about 'the Big One' when I was living there.  It's the Cascadia fault line that is overdue to rupture, by some estimates.  I believe it runs about 1000 km from northern Vancouver Island all the way down to northern California.  It's quite far off shore where the Juan de Fuca Plate is subducting beneath the North American Plate - and it doesn't reach as far south as LA. I don't think it even reaches the northernmost section of the San Andreas fault. 

The last megathrust Cascadia quake was in January 1700, and we know this because a tsunami hit Japan approximately 10 hours after the quake.  There were no written records in what is now western Canada at that time, but there are Indigenous oral histories that speak about great shaking and flooding.  Japanese historians recorded the tsunami as an 'orphan' tsunami because there was no quake felt in Japan before the waves hit there - since the earthquake had happened all the way across the Pacific.  

I've read that these ruptures happen on average every 300-800 years, or so.  Cascadia is currently 25 years past the low end of this average, and almost 500 years from the top end.  If the entire fault ruptures it could cause a quake in the range of 9.0 to 9.5, which would likely devastate Vancouver, Seattle and Portland.  If only a portion of the fault ruptures, then the quake might 'only' be 8.0-8.5.  This is still extremely strong and damaging, but it would only release one tenth of the energy of a 9.0-9.5 quake, since the scale is base-10 logarithmic in nature - if I recall correctly.  I don't know if the quake today would have relieved any pressure on the Cascadia fault, since it's quite far off the west coast of Vancouver Island and today's shaker was on the coast of the mainland itself - and I don't believe the two faults are connected.  🤷‍♂️

Edited February 22 by CuriousByNature

[Lotus-eater]

4 hours ago, Luv2play said:

As I understand it, both Vancouver and LA are  on fault lines that at some point will result in the Big One. I think small earthquakes are to be welcomed as they relieve the tension between the tectonic plates that underly the region. 

Myth #5: Small Earthquakes Relieve Pressure and Prevent Larger Ones 

FALSE: It’s a common misconception that small earthquakes can release pressure along fault lines and prevent more significant earthquakes.  

While small earthquakes can indeed relieve some stress along a fault, they typically DO NOT significantly affect the likelihood of larger earthquakes. In fact, a sequence of smaller quakes can SOMETIMES indicate that a larger one is on the horizon, but not always. It’s essential to remember that earthquakes are unpredictable and can happen at any time or anywhere.

[+ Pensant]

I live north of Seattle on an island for part of the year and occasionally wonder about the Cascadia fault or the eruption of Rainier. Either would devastate Seattle, much of which is built on fill. In eleven years, I’ve never even felt a tremor.

[Luv2play]

3 hours ago, Pensant said:

I live north of Seattle on an island for part of the year and occasionally wonder about the Cascadia fault or the eruption of Rainier. Either would devastate Seattle, much of which is built on fill. In eleven years, I’ve never even felt a tremor.

How did Seattle come to be built on fill?

[CuriousByNature]

3 hours ago, Luv2play said:

How did Seattle come to be built on fill?

I heard that Phil was an early mobster in the Pacific Northwest, and a rival mob made him 'disappear' and buried him in the vicinity of what is now Seattle.  

That's how Seattle came to be built on Phil.