Lesson video

Hello, my name's Mrs. Harking.

The title of today's lesson is Living in Earthquake Regions.

It's taken from the unit Tectonic Hazards: Why is Earth Restless? Today we're going to be exploring what we can do if we ever are in a situation where we experience earthquake and how people who live in these zones survive in them.

There are some tricky bits in today's lesson, but that just makes it more interesting.

We'll work through this together.

Our outcome today is to explain to what extent people can anticipate earthquakes and how they can survive living in areas affected by earthquakes.

There are some words that are really useful to know before we start the lesson.

If you are not sure about any of these words, it might be a good idea to pause the video and jot them down.

Firstly, we've got probability.

This is the chance of something occurring, such as an earthquake.

Then we've got prediction.

This is saying exactly when, where, and what will happen.

And detection.

So this is identifying that something has just happened or is happening right now.

We're going to break down these words a little bit more in the lesson and you'll see how useful they are to know.

But if you are not familiar with any of these words, maybe in another context, then it would be a good idea to get these jotted down now.

Today's lesson is in two parts.

Firstly, Can we tell if there will be an earthquake? And then, How can we protect people from earthquakes? So first we're gonna look at Can we tell if there will be an earthquake? Andeep says, "I don't think earthquakes are much of a worry now, as people know all about them." Laura says, "I'm not so sure about that.

I don't think scientists can tell when they will happen.

So they are still very dangerous." What do you think? Feel free to pause the video now to discuss.

Maps of plate boundaries and historical earthquake records as well as satellite measurements of plate movements all allow scientists to calculate the pressure exerted on different fault lines.

We can see on the map here the earthquake locations and their magnitudes for the earthquakes to happen between 1900 and 2017.

So all of this information means that humans can calculate the probability of an earthquake happening within a region over a long period of time.

For example, we've got here, there's a 75% chance of a magnitude 7 or more earthquake on the San Andreas Fault at some point in the next 30 years.

So that would be just here located on our plate boundaries map.

So we're only saying a 75% chance of a really significant 7+ earthquake in the next 30 years.

They are not saying, on Friday there'll be a magnitude 7 earthquake.

That is not something that they can say right now.

So which of these might be used to help calculate the likelihood of an earthquake occurring within a region in future years? Is it maps of plate boundaries, historical earthquake records, satellite measurements of plate movements? Which do you think helps scientists? Well done, it's all of these is now.

Maps of plate boundaries, historical earthquake records and satellite measurements of plate movement.

So it's worth noting the one you missed if you did miss one or two of these.

All of these pieces of information are put together to help scientists calculate the likelihood of earthquakes occurring in a region in future years.

Alex says, "If we know where earthquakes will occur, that means people can get ready.

So we're sorted?" Is he right? Jun doesn't agree.

"It's not possible to predict exactly when or where earthquakes will occur or of what size they will be.

So no scientific method using short-term warning signs like changes in radon gas, animal behaviour, et cetera, have been proven to work." This is a common misconception that's out there that actually there are methods we can use to predict earthquakes happening maybe hours or days before and that is not the case.

At the moment, it is not possible to do that, although scientists are obviously trying to find methods which would work.

None of these methods have been proven to work yet.

Earthquakes can be detected whilst they are happening.

So this is different to predicting them.

They can be detected as the shaking is happening.

Now, this is actually useful because seismic sensors detect the first felt wave which hits slightly before the most damaging waves.

So have a look at our diagram here.

You can see that the first wave felt is the yellow wave.

Now that one isn't as damaging, and the sensors can detect that and then send signals to warn people in local areas that might be hit by the damaging waves that come second.

In some locations, people benefit from systems like ShakeAlert in the USA or Japan's Early Warning system.

These send out fast alerts, which is really useful to the people in the local area.

They only provide seconds of warning, though.

So this can be enough to stop trains and shut down power plants and maybe even people can take cover, but it's only seconds of warning.

We're not talking hours or minutes or days, just seconds because this is only happening after the earthquake has actually started.

Time for a check for understanding now.

Which of the following are believable statements to hear about earthquakes? Is it A: A magnitude 7 earthquake will hit LA on Friday, B: There is a 60% chance of a big earthquake here in the next 30 years, or C: An earthquake just started, take cover? Yes, so the last two, B and C.

We've got there is a 60% chance of a big earthquake here in the next 30 years.

So that's the probability, isn't it? And then we've got C, an earthquake just started, take cover.

So that's when the earthquake has been detected and a warning has been sent out.

So seconds of warning might be given.

True or false? People living on plate boundaries have to evacuate before earthquakes hit.

False.

Can you tell me why? Yes, it is not possible to predict earthquakes yet.

So evacuation is not possible.

Once the earthquake has started people might get some seconds of warning before the damaging shaking starts, if they're lucky, but not long enough to evacuate.

That is not possible at the moment.

Earthquake alerts rarely provide as much as 60 seconds warning.

It's normally less than 60 seconds.

Let's have a look at some examples just to give you an idea of this.

So our first example here is in China.

So they got up to 50 seconds of warning in Chengdu, in China during the 2022 Luding earthquake.

So that's quite good, up to 50 seconds depending on where you were.

In contrast, people in Tokyo in Japan had only 15 seconds of warning during the 2022 Tohoku earthquake due to the shorter distance between the epicentre and the affected communities.

So the closer the epicentre, the point on Earth where the most shaking is felt, the closer that is to large populations, so cities for example, the less warning those people in the city are going to get because the earthquake is simply going to get there faster.

There's less distance to travel.

So if the earthquake begins really close to a large city, there's very little warning that can be provided.

Still we're trying.

Not all areas have sufficient detection and communication systems to be able to provide such warnings.

So some areas don't have the detection.

So even if an earthquake happens a distance away from a city, actually the detectors aren't there to pick up those first waves and then the communication systems aren't in place to be able to inform people to shut those trains down, those power stations, et cetera.

So some areas benefit from these warnings if the earthquakes happen sufficiently far away from large populations, and even then, the warnings are only going to be seconds before the damaging shaking hits.

So it's something but it's not great.

Time for a check for understanding now.

True or false? The further you are from the epicentre, the more warning time you are likely to get.

Is this true or false? Can you tell me why this time? It is true.

Well done.

Right, now I'm looking for the why.

The seismic waves take time to radiate out from the focus underground.

The epicentre is a place on surface directly above the focus that the waves of energy reach first.

So the further from the epicentre, the more warning time you are likely to get.

Time for our practise task now.

Can you correct each of these statements for me? Each statement has one error in it.

So you've got to spot the error and make sure you correct it.

Pause the video now to give yourself time to do this.

Well done.

So the correct statement should look like this: Number one: Calculating the chance of an earthquake occurring in the next 30 years is possible.

And that's just the probability of it happening, isn't it? We can do that.

That's brilliant.

Number two: Those who live on plate boundaries should always be ready to protect themselves an earthquake.

Number three: The exact timing and location of an earthquake cannot be predicted.

We cannot predict that.

However we can detect it, so number four: Detecting earthquakes while they are happening gives us seconds warning before the worst shaking hits.

And we said it was unusual to get more than 60 seconds warning, don't we? So number five, our final one: The USA's ShakeAlerts and Japan's Earthquake Early Warning system send out alerts and give people seconds to prepare.

So it's not hours to prepare.

That's not possible.

It's only seconds.

So what we can see here is that we can say vaguely, we can predict the probability of an earthquake happening in a certain location and give a rough magnitude, but that's over a long time period.

When we look at something more specific, we cannot predict the exact timing, location, et cetera of an earthquake, but we can detect them when they're happening.

That only gives seconds warning, but it is something.

And that's really good.

Time for the second part of our lesson now.

How can we protect people from earthquakes? So it is wise to take precautions when living on a plate boundary.

So this means earthquake drills, earthquake emergency kits and building design need to be considered.

Preparation protection are as, if not more important than detection.

So we've said that actually predicting earthquakes is impossible.

We can get a probability of a long time scale, but we can't predict them.

We can detect them, but we only get a few seconds warning.

If that's the case, then we really need to make sure that before that detection has happened, we're in the best possible situation to withstand an earthquake.

And that's what people who live in these zones do.

That's how they survive living in these zones.

Earthquake drills are run in the same way that fire drills are.

Except instead of leaving the building, participants do this: They drop.

This is to avoid being knocked over.

Cover: So this is covering head and neck to avoid injuries from falling objects.

And then hold on.

So this is if they're able to hide under a shelter, for example, a table is a really good one, then they hold on to make sure that that doesn't move away from them.

On earthquake awareness days, participants are also educated with further safety tips.

For example: Avoid windows as broken glass can cause serious injuries.

Sheltering under tables is always better than a doorway as it provides a barrier against falling objects and debris.

Stay indoors during the shaking as there's greater risk of falling debris and power lines outside than there is inside.

And prepare an earthquake emergency kit.

These tips are not only useful for people living in earthquake zones, but also for people who might visit earthquake zones at some point in their life.

And that probably includes us, doesn't it? That there's a chance that we might visit an earthquake zone.

So for that reason, it's really good for everyone to be educated about this globally because it could save your life.

Earthquake emergency kits are one that are worth discussing in a little bit more detail.

They contain items that are useful if someone has to leave their damaged home after an earthquake.

So for example: food, canned food, protein bars, nuts, things that might go off.

Blankets.

If you are out of your home, then you might need to protect yourself from the elements, keep warm.

First aid kit, especially if people have had an injury.

That's going to be quite important.

Don't want, say, a scratch becoming infected and actually causing you to end up in hospital, even if you haven't been badly damaged by the initial quake.

That could be quite life-threatening if an injury does get infected.

Torch.

So electricity can be really affected during earthquakes.

So it can mean that the normal street lighting and lighting in the area that you're in isn't there.

So you want to be able to see after dark falls.

Water, obviously really important, not only for drinking but for cleaning cuts and injuries as well.

It can be really hard to access water if pipes have been damaged.

Lastly, we've got important documents, for example, passports and medical information.

Now all of these are examples of what could be included in kit.

There is lists that are far, far longer than this.

I'd like you to see if you can remember these useful items and I'm going to remove one and you've got to see if you can remember which one has disappeared.

Get working.

So check for understanding now.

Which item is missing from the earthquake management kit? Well done.

It was the first aid kit.

A really important item to have in there.

Architects can design earthquake resistant buildings.

This is another way that people in earthquake risk zones can feel more protected against earthquakes.

There are lots of different ways that buildings can be made more earthquake resistant and we're going to go through a few of these now.

Base isolators absorb vibrations, reducing the amount of shaking that reaches the building.

You can see on the diagram here that these are not normal foundations for a building.

They allow the building to move from side to side without the structure actually bending and breaking.

We can see in the animation, so a small model of this showing how actually the building on the right which has a base isolator is able to move from side to side without bending, shaking and breaking.

Whereas the building on the left is, there's a lot more wobble going on there, isn't it? So there's no base isolation on that one and that building is subject to a lot more shaking.

Flexible building materials are another architectural trick which means that buildings don't break but they bend instead when an earthquake happens.

So on the left here we've got bamboo, which is a really low cost, natural, flexible, strong material that can be used in buildings.

We've also got steel on the right and this is expensive, but it offers great strength and it does flex.

So these two materials are used a lot in areas at risk of earthquakes.

Time for a quick check for understanding.

Which material is more likely to be used in a low income country to build homes in a zone prone to earthquakes? Is it going to be bamboo or steel? You remember which one was cheaper? Well done, it's bamboo.

Fabulous.

Strong shapes are another trick architects use to prevent buildings collapsing in earthquake risk areas.

So cross-bracing provides this cross shape and gives more strength to a building.

Circular or curved shapes are very strong so they can be used as well.

And we've got triangular or conical shapes are also very strong shapes.

So often these shapes will be seen in buildings, in earthquake risk zones.

This one is a really interesting strategy.

So a mass damper is a device mounted at the top of the building and it's engineered to counteract and dampen its swaying in the event of an earthquake.

Here we have the Taipei 101 building, which in Taipei in Taiwan.

The animation shows us here how it works to counteract that shaking.

Time for a check for understanding now.

What is the name of this feature of earthquake resistant building design? Is it A: base isolator, B: strong shapes, or C: mass damper? Well done, it's C, mass damper.

Task B.

I would like you to complete the poster aimed at educating the public about how to survive an earthquake.

So over on the right here we've got the poster.

It says be earthquake safe, take part in earthquake drills.

You've got to drop.

Then what is it that's missing in the middle? And then hold on.

And then create your own earthquake kit, including: Could you list me four things? You can list more if you'd like, that's absolutely fine, that you should have in an earthquake kit.

The second part of this task is to design an earthquake-resistant building.

I would like you to anate on at least three features that make it earthquake resistant.

So you can use any of those strategies that we looked at that architects use to try and make buildings more resistant to earthquakes.

I would suggest you do a diagram of this.

It doesn't have to be made, don't worry if you are not the best drawer in the world.

Just keep it simple and focus on the strategies that we've talked about.

So put those into your design.

I'm sure you're going to come up with some really ingenious and amazing-looking buildings Pause the video now to give yourself time to do this.

Well done, everyone.

Let's have a look at my version.

Here we've got our poster and I've just put Cover in the middle.

So I drop, cover, hold on, in the first part.

In the second part of the poster about the earthquake kit, I have included blankets, first aid kits, food, such as canned goods, protein bars and nuts, a torch, water, important documents, for example, passports and any medical information.

You may have any four from that list in any order.

That's absolutely fine.

You may even have included some more things than I have, which is great.

So second part of this task was to design an earthquake-proof building.

Now I'm gonna show you here an example.

Yours may look very different to this and that's absolutely fine, as long as we're including the strategies that we discussed that will actually help these buildings resist earthquakes.

So here I have drawn a strong triangular shape.

Your shape may be circular, for example, or it might be conical.

That's absolutely fine.

I've put a mass damper at the top to counteract its swaying in the event of an earthquake.

If you've included one of these, have you given a brief explanation of how it works? That would be really good to add in.

Cross-bracing has been added as well at the bottom for strength.

So it's really good that I've put cross-bracing, but I've also said why, so it's adding strength to the building.

And then I've put that it's built with steel frame for strength and flexibility.

So yours could be built maybe with bamboo or it might have been built with steel.

Did you include the materials that you used to build it? Maybe add that one if you didn't.

Lastly, I've put base isolators.

So base isolators absorb vibrations, stopping the shaking reaching the building.

So that has been included at the bottom.

Is there anything that you'd like to add to your own design to improve how earthquake resistant it is? Feel free to add something now.

Well done, everyone.

We've reached the summary.

That was a really tricky lesson.

There was lots of complex elements in the detection and prediction, or not, of earthquakes, and also we looked at the architecture.

So it's really quite complicated.

So if you feel like you've achieved in this lesson, you should be really proud of yourself.

We're going to look at the summary now.

So scientists can calculate the probability of an earthquake happening within an area in the future.

It is not currently possible to predict exactly when or where earthquakes will occur.

That was really important.

I would like you to remember that as you come away from this lesson.

But we can detect earthquakes, although it only provides seconds of warning.

Drop, cover, hold is practised during earthquake drills.

And base isolators, flexible building materials, strong shapes and mass dampers help to create earthquake resistant-buildings.

I hope you found today's lesson interesting.

I'm looking forward to seeing you next time.

Bye-bye.