What floor should I live on in an earthquake zone?

December 7, 2005 2:21 AM

Disaster filter: So, I live in an earthquake zone and am looking for a new apartment. What floor should I live on?

I've just moved to Kathmandu and am looking for an apartment. All the houses are built using a simple concrete and steel structure, and are liable to collapse in a similar way to those in the recent Pakistan 'quake. In looking for an apartment is it safer to be on the upper floor or ground floor of an apartment? Or does it make little difference?

posted by MrC to home & garden (15 comments total)

Upper floor vs. ground floor MIGHT matter, but it's not the first thing I'd consider, MrC. Do you have any way to find out about the soil? That's the biggest factor. If you have a choice, you want to be on rock. If Kathmandu is where I think it is, that should be easy. Next, are ALL the houses built the same way and of the same materials, same vintage? If possible, you want wood....

Oh heck, if you have to be in a multistory building, go for the top floor. There's less to fall on you. Makes a big difference.
posted by clicktosubmit at 4:53 AM on December 7, 2005

I would say ground floor so that you can escape quickly as soon as you feel an earthquake starting. If the building is going to collapse I can't imagine that any of it would be safe. Earthquakes don't start suddenly; usually you will have a few seconds to get out of there. I would look for a ground floor apartment near a safe open space like a park without trees.
posted by Alison at 4:55 AM on December 7, 2005

I live in an earthquake zone and unless you're Barry Allen I don't think there is time to realize what is going on, gather your wits, and evacuate the area unless you happen to be right next to the door. I mean, save for those who work at home, people are usually asleep more than half of the time they're in their apartments. Who has the presence of mind and sheer reflexes to be woken out of a sound sleep, instantly realize that there is a serious earthquake starting, and sprint out of the building while naked or nearly so?

I don't think counting on running out of the building is a good strategy. IF you are already awake and IF you can instantly tell a bad earthquake is starting and IF you can safely get to a wide open area, that would be great. But those are some serious ifs.

Planning to debris surf a collapse should, needless to say, also be a definite Plan B.

Your best strategy is to find the safest building on the safest ground that you can and then to figure out the safest place inside the apartment to be during an earthquake. If conditions are such that you happen to be able to evacuate to a clear and wide-open area at the start of a big quake, well, great. But don't count on it.
posted by Justinian at 5:15 AM on December 7, 2005

I live in an earthquake zone and unless you're Barry Allen I don't think there is time to realize what is going on, gather your wits, and evacuate the area unless you happen to be right next to the door.

Granted, it is not a log period of time and if you're a heavy sleeper you might be screwed, but in every earthquake I have been in there has been a few seconds (maybe 20) to turn off the gas before getting under a table.

When reading about the aftershocks in Banda Aceh most people slept outside or ran out of their homes at the first sign of a tremor. ("With the earthquake's first aftershock, everyone again rushed from the emergency room, afraid the roof would fall.") Likewise, when there were rumors of an earthquake in Harbin people camped outside. This is because being inside any poorly made building is not safe and it is better to stay outside.

However, if this is not an option, I have heard that the second highest floor is the safest. You are more likely to survive a roof collapse.
posted by Alison at 5:46 AM on December 7, 2005

seems likely, since you're posting to mefi, that you're some kind of relatively affluent westerner. if so, you have more chance than most of being able to afford a room in a well constructed place (or a single storey building).
posted by andrew cooke at 7:12 AM on December 7, 2005

It really depends on the construction. In the Loma Prieta quake here in SF, many buildings collapsed downward, where the upper floors survived relatively well, but the first floor was demolished by the weight of the floors above falling down. On the other hand, top floors get much more sway than bottom floors... The other thing to note is that corner buildings get much more shock than buildings on the interior of a block in that they generally get force from both axes rather than just side to side.
posted by judith at 8:52 AM on December 7, 2005

Building height is critical, if the building resonates at the frequency that the earth is shaking, you are in deep trouble.

Here is the first thing I could google on it: +plus magazine - Quake-proof.

As a result, earthquakes can be very selective in their destruction. For example, in the 1985 earthquake in Mexico City 8-10 storey buildings were badly damaged, while shorter and taller buildings fared better.

(I have no idea why you would want to call your site plus-plus magazine, but it does look interesting)

I'm sure soil considerations are also important, but maybe not as much as you would think for a very large building. Who knows what else...

Then there is the question of where in a building you want to be if it is going to collapse. I think you want to be on the bottom, then if you are lucky (or unlucky depending on how much imagination you have) you might find yourself in a void and hold out for a few days. I think if you are 30 stories up and the floor goes out from under you -- that's the end.
posted by Chuckles at 8:56 AM on December 7, 2005

corner buildings get much more shock than buildings on the interior of a block in that they generally get force from both axes rather than just side to side.

That would only make sense if they were physically connected - like row houses - otherwise it couldn't make any difference. Even then... Being in the middle of a row of houses would probably help a lot because the houses on either side should help to hold yours up. The effect of this might be as you describe, because the stiffness along the row would be much higher than the stiffness from front to back.
posted by Chuckles at 9:06 AM on December 7, 2005

Chuckles said, "For example, in the 1985 earthquake in Mexico City 8-10 storey buildings were badly damaged, while shorter and taller buildings fared better. ... I'm sure soil considerations are also important, but maybe not as much as you would think for a very large building."

Mexico City is built on an ancient lake bed, so the soil below it is weak and amplifies the waves. Second the built on rock suggestion.

Interestingly, Mexico City is one of the only places that has an earthquake warning system -- quakes tend to originate from a fault on the coast and take about a minute to reach the city.
posted by LeiaS at 9:37 AM on December 7, 2005

Regarding the inside-outside question: If you live in a country with reasonable earthquake engineering standards and lots of things outside that can fall on you (America, Japan, &c.), stay inside. Get under something, if you can (say, a table) and stay away from windows. In someplace with crap construction, consider this AskMe. The Triangle of Life referred to there is probably still safer than running outside unless you live next to a field.

Also, I grew up in earthquake country, and I gotta say, the chances of being alert enough to run outside before the earthquake starts (or turn off gas!) seem pretty low to me. That is, I think Alison's experience is rare enough not to be counted on. But learn where your gas hookup is. And then, don't turn it off unless you smell gas, because when everyone turnsit off, it can be a while before it goes back on (in my experience).

Most generally, though, don't worry about it too much. Make yourself a nice little survival kit with some water & food & blankets, and then just leave it. People think earthquakes are scary because really big ones can create some photogenic destruction. But the majority of them are not that big and not such a big deal. Between my mother and I, we have sixty years of living in an earthquake zone, and we've never even had our crockery break. It's like terrorism: it sounds scary, but the chances of it specifically killing you are pretty low.
posted by dame at 9:40 AM on December 7, 2005

Also, I grew up in earthquake country, and I gotta say, the chances of being alert enough to run outside before the earthquake starts (or turn off gas!) seem pretty low to me. That is, I think Alison's experience is rare enough not to be counted on.

Sorry! To be clear, I was cooking and turned off the gas to the stove because open flame + earthquake = bad. Still, those few seconds are critical if you are cooking or using a kerosene heater. Fire is the biggest threat if you're trapped.

Anyway, I agree that going outside is bad unless you have an open area to get to. Falling debris is a huge hazard.
posted by Alison at 10:18 AM on December 7, 2005

Geology nut here ...

All the answers above are on the right track -- there is no "best" place to be in an earthquake, as there are so many variables to consider. You can only maximize your odds so much.

The main point to realize is that in an earthquake in a third-world country, it's the lack of proper building construction/inspection techniques that are the real culprits in collapse and resulting fire. Does it surprise anyone that there is so much loss of life in Pakistan and Mexico, when San Francisco, Los Angeles and Kobe don't get completely hammered by the same or similar levels of earthquake activity?

Moreover, the lack of thoughtful, organized emergency services that prevent rescue and recovery.

My advice: Maximize odds by choosing well-constructed buildings on areas that are not atop loose, sandy soils. Choose buildings that are near whatever emergency services are available (e.g. try to live next to the fire station). Cache emergency supplies. Make evacuation plans.
posted by frogan at 10:35 AM on December 7, 2005

Check this out. Nepal does not sound like a place with many well constructed buildings.

I'd recommend finding a living space in a one-story building. There's still a significant risk of heavy masonry walls falling in though, or the roof falling down, due to inadequate connections between the roof and tops of the walls.

Frogan - that's a good post. But as someone who practices structural engineering for a living, even I would have a hard time figuring out which buildings were better constructed than other and what types of soil deposits underlay that site in a third world country, let alone a layperson. A lot of what you'd be looking for is hidden, such as the presence of steel reinforcing in masonry or concrete elements, the strength of the mortar or concrete itself, or wall-to-roof/wall-to-floor connections.

I don't have any direct experience in third world construction methods, but, I would definitely stay away from buildings like this made from stone masonry with mud mortar. Really, as someone pointed out upthread, you'd ideally like to find a one-story timber framed building, but that seems unlikely in your location.

As far as your question of what story? I've never seen any advice about which may be more survivable. There may be studies out there, but I don't know. But I would not listen to any talk about "surfing" debris - gravity is gravity.
posted by pitchblende at 1:11 PM on December 7, 2005

I would have a hard time figuring out ... what types of soil deposits underlay that site

Good point. Geological survey maps are the starting point.

But for a true layman ... Look around. Try to avoid a flood plain (most of Los Angeles), or the area beneath a rise that shows lots of weathering (e.g. the Marina District of San Francisco, rolling hills, the flats adjacent to a cliff side). Stay out of the bottom areas of canyons. Was the area a dry lake bed (like Mexico City)? Is the surface soil sandy? Odds are the ground beneath is sandy as well.

A lot of what you'd be looking for is hidden, such as the presence of steel reinforcing in masonry

Another good point. But common sense should prevail -- you know, if you really worried, don't live in a building that looks like it was made entirely out of cheap-ass cinder blocks, like you see in Mexico City.
posted by frogan at 4:50 PM on December 7, 2005

In Kathmandu you may have little control over whether or not your building is constructed from reinforced masonry (IMHO, the most important factor besides soil composition.)

What you do have control over is your preparedness. Inside your apt, minimize items that are tall and heavy, or that could fall or be thrown across the room, especially near the bed. Keep a backpack handy with survival items: water filter, energy bars, first aid kit, cash, etc. If your building is damaged you may need to evacuate, and you will definitely need to be self-sufficient for a while. And make a plan ahead of time as to where you would go if you did have to evacuate.
posted by shifafa at 11:16 AM on December 8, 2005