Weekend Update 4/23/23

[Jbub]

There was a 5.7 earthquake in Salt Lake, March 2020. Not to high on the Richter Scale but it was strong enough to make my chandelier swing for almost 20 minutes and knock some stuff of shelves. That was the first "real" quake that I had experienced and I was freaked out and couldn't go down to my basement for a couple of days because I was afraid my brand new house would collapse. Fear is real and often stupid.

[nkalanaga]

Considering the quality of some construction today, especially if local codes don't include earthquake resistance, staying out of the basement for a while might be a wise decision.

[lock4244]

My area of the globe (Toronto/southern Ontario, so kinda north-eastish) does indeed experience the occasional earthquake.   

They are very mild and short lived, but noticeable (tall houseplants might sway, slight china rattles, my office chair on wheels once moved an inch or two to-&-fro). 

Interestingly, these quakes are due to isostatic rebound.  In short, the earth’s crust in these areas had previously been depressed, for exceedingly long periods of time, by massive glacial ice sheets over one mile high.  The ice melted long ago, but the crust is still rebounding, hence the minor vertical bumps that we (rarely) experience as almost-insignificant quakes.  Quite different than the slip-fault quakes that can be horrifically destructive in plate subduction zones. 

(Two minute dissertation, courtesy of a humble BSc Geology, UofT - retired!)

I've lived my whole life in Scarborough until last year, and can recall at least two earthquakes. One I jumped out of bed to the sound of a loud bang which was later determined to be an earthquake out somewhere below Lake Ontario. The other was at work one day and everyone just sort of felt a slight disorientation at the same time, but it wasn't anything that you could perceive though the movement of objects or anything obvious. Was also confirmed to be an earthquake.

[C855B]

Earthquakes... heh. I grew up in Southern California.

I was still living at home during the 1971 Sylmar earthquake, diving under my bed and dragging our dog underneath with me out of a justifiable concern the ceiling was going to cave in on us. It held, but cracked pretty good. We were about 25 miles from the epicenter. This quake was a 6.6, and quite a ride where we were. This earthquake did indeed collapse a freeway flyover, leaving a "bridge to oblivion" very much like the model you guys are laughing about.

There was another memorable quake about two years before, it was only a 3.5 or so, but it cracked the mortar on our chimney. I recall about a half-dozen notable earthquakes while growing up. Quakes weren't an everyday thing as people who sneer at California imply; I'll take the very infrequent earthquakes over Midwest springtime tornadoes any day. But we're not immune to quakes in southern Illinois - I was knocked out of bed by a 5.4 temblor 15 years ago, epicenter about 50 miles to the east.

There was a 5.7 earthquake in Salt Lake, March 2020. Not to high on the Richter Scale...

No, 5.7 is pretty strong. Again, the Sylmar quake was 6.6, and it destroyed a hospital, damaged another, collapsed a big freeway interchange, and almost took out a major dam. What is perceived on the surface all depends on the depth and type of movement.

[Jbub]

Considering the quality of some construction today, especially if local codes don't include earthquake resistance, staying out of the basement for a while might be a wise decision.

The inspector did call out a few items during framing that didn't align with earthquake code, which i was greatful for. The racking boards were in the wrong spot on the trusses. We always talk about the"big one" along the wasatch front that we are overdo for so building codes are pretty specific with earthquake stuff. But then we have cities who allow developers to do stuff that leads to this
https://www.ksl.com/article/50627265/2-homes-slide-in-draper-nearby-trails-closed

[craigolio1]

My area of the globe (Toronto/southern Ontario, so kinda north-eastish) does indeed experience the occasional earthquake.   

They are very mild and short lived, but noticeable (tall houseplants might sway, slight china rattles, my office chair on wheels once moved an inch or two to-&-fro). 

Interestingly, these quakes are due to isostatic rebound.  In short, the earth’s crust in these areas had previously been depressed, for exceedingly long periods of time, by massive glacial ice sheets over one mile high.  The ice melted long ago, but the crust is still rebounding, hence the minor vertical bumps that we (rarely) experience as almost-insignificant quakes.  Quite different than the slip-fault quakes that can be horrifically destructive in plate subduction zones. 

(Two minute dissertation, courtesy of a humble BSc Geology, UofT - retired!)

This is by far the coolest thing I have learned in recent times! I always wondered why we had tiny quakes now and then. I thought maybe the Niagara Escarpment was an ancient fault that still shook now and again.

Craig

[Dwight in Toronto]

I've lived my whole life in Scarborough until last year, and can recall at least two earthquakes.

I’m a Scarborough boy too - Brimley & Lawrence ‘til I got married some 40+ years ago (now in Markham).  I remember those quakes.

  But we're not immune to quakes in southern Illinois - I was knocked out of bed by a 5.4 temblor 15 years ago, epicenter about 50 miles to the east.

Some folks might be surprised to learn that southern Illinois is part of an area that is THE most active quake zone in all of North America.  Google “The New Madrid Seismic Zone”, an area comprising western Tennessee & Kentucky, NE Arkansas, SE Missouri & southern Illinois.  I’ve been fascinated with this locale for decades - seismometers pick up negligible activity pretty much every day, but there have been some very significant incidents in the past. 

Craigolio - it makes me happy to think that I helped enlighten your day … cheers!

[chuck geiger]

New layout short:

https://youtube.com/shorts/q5t2XIpK8zQ?feature=share

[lock4244]

I’m a Scarborough boy too - Brimley & Lawrence ‘til I got married some 40+ years ago (now in Markham).  I remember those quakes.

Grew up in three homes, starting on Midland at Kingston, then closest to you would've been on Amberjack (Bellamy and Brimorton) from 78 to 83, then was a eastern Scarbierian at Meadowvale and Lawrence E.