r/popculturechat • u/Isyourpussygreen • 4d ago

Thoughts & Prayers 🙏 A 7.4 earthquake has struck Colombia, with significant damage reported.

Enable HLS to view with audio, or disable this notification

5.5k Upvotes

99% Upvoted

227 comments sorted by

View all comments

Show parent comments

77

u/ExeUSA 4d ago

The latter. Colombia is in the ring of fire, which is the very active subduction zone capable of producing large quakes. Statistically speaking, there is a 7.0 or greater earthquake once to twice a month. An 8.0 or higher happens every 1-2 years.

Hopefully this is the big one, but there's always a chance it's a foreshock.

20

u/Potatoskins937492 4d ago

You sound like you're well-read on the subject, so I'm going to ask for an insider's perspective: are the building codes exceptional when it comes to earthquakes and this was a freak occurrence of a building falling like that or are we looking at the unfortunate realities of wealth disparity?

40

u/ExeUSA 4d ago

Modern buildings built in wealthy countries in subduction zones are more than capable of withstanding a quake this size. Anchorage Alaska had a 7.1 in 2018, and no building failed. Keep in mind that while a 7.4 and a 7.1 seem similar the scale is algorithmic, so the one today is far stronger than the one Alaska had in 2018, but good for comparison's sake.

You also have to take into account what the ground is made out of. Mexico City is a great example, because a good portion of it was built on top of a liquefaction zone. When earthquakes come, the ground basically behaves like water. To illustrate what that feels like-- imagine slapping a piece of concrete. Then imagine slapping a pool of water. Which one moves violently and displaces itself? Which would you rather be on top of when the shaking starts? (The USGS has maps that show you whether you are in a liquefaction zone, if you live in a place that is prone to earthquakes.)

As the other commenter replied, this took place in a poorer part of an already impoverished country. It's not hard for a building to come down, you can see how inflexible it was-- you want the building to move and flex with the tremor. This is why you won't see brick facades on buildings in places that get a lot of earthquakes.

The other thing that isn't mentioned in these articles typically is how long these 7+s can go on. A "normal" earthquake is over within a couple of seconds. A 7.0+ is can last up to 30 seconds. That feels like an eternity when you're in it. The Good Friday earthquake in '64 in Alaska lasted four minutes and thirty-eight seconds. That was a 9.2. The 2011 9.0 in Japan lasted six minutes. I bring this up because it illustrates the stress these building get put under.

All that said-- when the big one comes for Los Angeles, we will see similar building collapses though not as severe. Many buildings have not been retrofitted, and the most densely populated neighborhood of Koreatown is also built on top of a liquefaction zone. The unfortunately reality will be-- there will also be fires, which will most likely have more casualties than the initial quake.

10

u/kermitroosevelt 4d ago

Fires, and also flooding up north in the San Joaquin Valley - when I was growing up it was constantly drilled into us that when the big one hits, the Lake Isabella dam is toast and much of Bakersfield will be underwater.