Hey there, Andy Lin here. Welcome to another issue of my newsletter: Back of the Envelope, where I focus on SE-related mini-lessons to help you (and myself) become slightly smarter.

Today I am going to talk a little about the Turkey/Syria earthquake…

This one was tough to write. Lots of people lost their lives, and many lost their friends, loved ones, and their homes ☹. My heart goes out to all those affected.

But we are structural engineers – so we need to talk about building collapses and failures. We need to talk about earthquakes. We need to talk about it so we can learn something and hopefully make the world safer.

Here we go.

(Estimated reading time = 2 minutes and 49 seconds)

The Big One in Turkey/Syria

As you know, a 7.8 earthquake struck Turkey/Syria 4 weeks ago. It was followed by another 7.6 just nine hours later (with lots of 4, 5, 6’s before and after).

(map of aftershocks and their magnitude)

(source)

Turkey’s building codes were supposedly modified in 1997 to match California’s, and they have been getting regular updates since.

But the number of collapsed/severely damaged buildings is estimated to be over 160,000…

How could that be?

Here are some of the preliminary findings and theories that I’ve found online:

1/ The actual spectral acceleration far exceeded the code design spectra (by 1.5x to 2x).

Here is a chart of spectral acceleration vs. period: (Red is the design spectra, and gray is the spectra based on recorded ground acceleration)

(source)

2/ Lots of older buildings have no ductility.

They were designed and built before the code update, which means there were no provisions to prevent the building from brittle failures.

Lots of shear failures and column longitudinal bar buckling etc leading to building collapse.

(Image from past earthquakes)

3. Major aftershock.

This is something we don’t really think about often. Major quakes back-to-back…

So basically, another massive shake just hours after the buildings were already severely damaged would likely bring the buildings down.

4. Soft/weak story

Apparently, there were many buildings in Turkey with these issues (apartment towers with open storefronts or parking on the first floor).

If not considered carefully and designed for, structural irregularities like these (ASCE 7 Table 12.3-2) will cause the building to fail prematurely in a modest earthquake, let alone a major one.

(Image from past earthquakes)

(source)

5. New building with shabby construction practices and lack of code enforcement

Basically many contractors and owners were taking shortcuts to save money.

Not much detail about this, but I picture a lack of permitting and inspection. Or perhaps design changes without engineer review…etc. In fact, hundreds of people are under criminal investigation for this.

Lots of lessons to be learned, and I am sure we’ll know more in the coming weeks.

So what does this mean for us?

This was an important reminder that “The Big One” could hit us anytime. We must be prepared and expect the worst – not just when designing structures at work but also in our day-to-day lives.

Here are some of the recommendations:

• Have your emergency kit ready

• Know your exit routes in a building

• Anchor your shelves and check for things that could be hazardous

• Talk to your kids about earthquakes

• Have a plan on what to do immediately after an earthquake (and be ready for aftershocks)

• Have a plan for a week or two following a major quake (i.e., communication, water, or electricity might be down)

Alrighty hopefully that was helpful.

Maybe we’ll end this on a lighter note – a dad joke?

Ask your kid (or someone with a sense of humor): "Hey what was yesterday's date?

They’ll respond, “...March 1st?”

You'd then proceed to march around the room. And when you are done say, “ok I marched. So what was yesterday’s date?”

(Wait for the groan.)

The end. I am going to try this on my kids later.

And that is all – thanks for reading!

Andy Lin
Back of the Envelope/Structural Engineer HQ