[shasheene]

The entirety of SoMa and Mission Bay are liquefaction zones [1], expected to face major damage during the next major earthquake.

I wonder if "Drop, Cover, and Hold On" really is good advice for liquefaction zones for a very big earthquake.

[1] https://gis.data.ca.gov/datasets/b70a766a60ad4c0688babdd4749...

[mrexroad]

Covering doesn’t do too much (in the moment) to stop a building coming down, but it def helps stop heavy objects from concussing or worse. For those in the Bay Area, Cal academy of sciences has a nifty simulator exhibit. For everyone else, just watch a few YouTube videos of how violently and abruptly everything not bolted down becomes a projectile.

It’s been so long since we’ve had strong seismic activity in the Bay Area that I’d wager most that have moved here in past two decades (hi!) don’t have all their bookshelves/etc bolted to the wall, breakables secured with quake-hold, shoes under bed, etc… not to mention proper supplies for significant infrastructure damage. I know I caught myself being complacent earlier this year after I reorganized all of our stemware and whisky/etc to a glass cabinet next one of our two exit paths. It would have been an a guaranteed 20-30 lbs of glass shards thoroughly blocking that path. But hey, I’ll admit I have cinema-induced-paranoia about two things: 1) being trapped barefoot with glass covered floors, and 2) potential for velociraptor ingress.

[kstrauser]

Don’t forget the quicksand, which could be a real thing in this case.

[rgoulter]

My experience (from the Christchurch earthquakes in 2010-2011) was that "wait and see if it's a big one" is what most people are more likely to do.

[robomartin]

> Drop, Cover, and Hold On

The only people who believe this advice haven't been in an earthquake or government workers who have to justify their existence by coming up with such nonsense, you know, like all the "don't do drugs" messaging and whatever they hand out at the DMV.

The last large quake I experienced was the Northridge quake. I lived very near to the epicenter at the time. It was 4:31 AM. I remember exactly because stayed up all night coding. I felt a strong tug. I immediately thought "this is a big one".

Next image I have in my head was me floating four feet up in the air and all my books up in the air with me (I had bookcases full of books on three walls). The lights went out, we fell to the ground and the powerful shaking started. When it all stopped, books covered the entire floor, it was a mess.

Floating four feet up in the air?

Yes!

The quake had a very strong vertical component. As it pushed up, it compressed the air cylinder right under me (part of the desk chair). That cylinder and the reversal of motion was enough to launch me vertically. My cars were launched into the air and collided with each other...on the driveway. The whole thing was insane.

"Drop, cover and hold on"? Yeah, right.

Don't get me wrong, running around like a maniac isn't smart at all. Keep your wits about you, stand under a doorway or something with decent structural support and assess from there. That is, if you are able to. Sometimes, as was the cased with Northridge, you don't have time for anything. People had entire buildings collapse onto them while in bed.

[Buttons840]

Question: An earthquake can be dangerous because it is long lasting or because it is short and especially violent. So my question is, are earthquakes usually a consistent intensity? Or can they be moderate intensity for 45 seconds and then flatten me with a pulse that makes me experience 3x my body weight?

[flashback2199]

They are generally not a consistent intensity during the event. Yes, it can be moderate for a bit and then more intense shortly later. There are several different waves that move at different speeds from the earthquakes epicenter and which decay at different rates relative to distance from the epicenter. One categorization is P, S, and surface wave. The time of arrival of each wave and their intensities depend on many variables. I think it is possible for the later arrival to be much larger and more destructive than the first, but I'm a bit hazy on the details.

https://science8sc.weebly.com/uploads/1/3/2/7/132773018/publ...

Anecdote, I was in a small earthquake in Tokyo, the initial thump woke me up and I rolled over under the dining table (sleeping on the floor as a guest) then the bigger vibrations arrived a few seconds later. The building was well designed for earthquakes, but in the moment I figured that, not knowing how big the rest of the earthquake will be, it was probably best to get cover anyway. I think cover is just about increasing the probability by some small amount that you could end up alive under the rubble if the building were to collapse.

[vtail]

Length of the earthquake is proportional to its strength.

[ck2]

I really do not understand how creatures like humans who can understand and plan for things build cities in flood zones, wildfire zones, earthquake zones, below sealevel, etc.

It's not like the death of the sun or heat death of universe where it's a billion years outside of your lifetime, it's going to happen in your lifetime.

The "oh well what can you do" response leads me to believe we aren't going to do a damn thing about runaway climate change.

[nostrademons]

Your commute happens about 250 days every year. A big earthquake happens maybe once ever 30 years. Buying a house takes 30 years to pay off. There's a limited supply of land; if all the houses in safe zones are taken, it may be worth it to some people to roll the dice on a house with natural hazards that's cheaper yet still close to everything. They're optimizing for the common case.

[atomicnumber3]

Some humans do, at least. I've read about there being stones in lakes or rivers that basically say "btw if you see this stone, you're as fucked as we were in the year 300AD" or something.

And in Japan there's those old stone marker monuments telling people not to build below them because of tsunamis or floods or something to that effect.

But I mean I guess when it's as desirable property as the SF Bay Area, the fact that you lose the building on it every hundred years or so is a small price to pay?

[toast0]

Some of those zones aren't static. Some of those zones are discovered after people have made a life there and getting people to leave an area where they've made a life is hard.

If you live somewhere with strong earthquakes on a regular basis and enforcable building codes, chances are most of the buildings will withstand a pretty good earthquake, but a really big one will cause trouble.

Areas without regular strong earthquakes are likely to be caught by surprise, although newer buildings are likely to do ok, if they enforce international standard building codes; IBC is good for reasonable earthquakes, but not for extreme earthquakes (earthquake prone areas have additional requirements). Areas without enforcable building codes unfortunately aren't going to be well prepared, it costs more to build buildings that won't fall over in a nearby 4.0, especially if they're taller than one story.

[Loughla]

It's too abstract.

Person is good at planning for abstract problems, because person controls their income, expenses, and priorities.

People are terrible at planning for abstract problems because it's collective resources and collective solutions requiring agreement from multiple parties who, inherently, have different and often conflicting priorities.

In other words, until the planet crashes and kills a vast, vast majority of us, we are going to carry on like we always have. It's depressing.

[Aeolun]

Even if it does happen in your lifetime. Do not underestimate the power of convenience.

https://99percentinvisible.org/article/tsunami-stones-ancien...

[dylan604]

>I really do not understand

money money money, MONEY! seems pretty simple to me

[aifooh7Keew6xoo]

Well, it usually beats homelessness or rent slavery.

[toast0]

What's the alternative? Drop cover and hold on at least avoids injury from attempting to move on an unexpectedly moving surface.

When the ground stops moving, then you have a chance at purposeful motion.

[opportune]

One alternative might be “run as fast as you fucking can towards Potrero Hill” if you are close enough to be able to make progress towards it.