Hello, my name is Mrs. Harking.

Today's lesson is the effects of earthquakes, taken from the unit Tectonic Hazards: Why Is Earth Restless? Today we'll be exploring why some earthquakes are so devastating.

Our outcome today is to categorise the primary and secondary effects of earthquakes and to explain why some earthquakes are more deadly than others.

Here are some keywords that will be useful to know before we start our lesson today.

The first is magnitude, the amount of energy released during an earthquake.

This is often measured in Mw, or the moment magnitude.

So this is a scale that measures how strong an earthquake is, and it's the one that is used the majority of the time.

Epicentre is our next keyword.

Epicentre is where the earthquake is first felt.

And it's a point on the surface directly above the focus.

Now focus is our next key term, and this is the point underground, so not on the surface but underground, where the tectonic plates first break or slip.

So we'll have a look at some diagrams to show the difference between epicentre and focus today during the lesson.

Today's lesson is in two parts.

First of all, we have what are the effects of earthquakes, and then why are some earthquakes more deadly than others? First of all, what are the effects of earthquakes? Where two tectonic plates meet, they become stuck or locked together due to friction, yet they may be moving in different directions or at different speeds.

Stress builds up over time until the rock fractures or breaks, releasing the energy.

We can model that with our hands.

So if you take your hands now and make two fists and interlock your knuckles together, you can see this is almost like a plate boundary, or a fault line.

If I try to move my left hand up and my right hand down, the plates are locked together.

They can't move.

And the stress is building up.

That stress will build up and build up and build up until the rock fractures.

And when the rock fractures, breaks, this is an earthquake, as the two plates move.

Waves of energy called seismic waves, or shock waves, are released, meaning the ground shakes.

So the ground shaking is the earthquake.

You can see here on the diagram these circles emanating out from a point are called seismic waves.

The point deep underground where the tectonic plate first break or slip is called the focus.

We mentioned this in the keywords, but let's have a look at it on a diagram to help us.

So focus here, it's underground and it's the point at which the plates slip.

The point on the surface directly above the focus is called the epicentre.

So you can see that labelled on the diagram here.

This is where the most shaking will be experienced by people on the ground.

So a quick check for understanding now.

Where two plates meet, they slide past each other smoothly.

Is this true or false? Well done, that's false.

Can you tell me why? Can you justify your answer? So you can choose between a and b here.

First of all, a, the rough edges of the plate become locked, or b, the two plates are moving in the same direction.

Yes, the rough edges of the plates become locked is the correct justification there.

Another quick check for understanding.

Which is the correct label for X.

So you can see on the diagram, I've put an X on top of one of those red spots.

Can you tell me, is that a, the epicentre, b, the focus, or c, seismic waves? Well done, yes, it's the focus.

The effects of earthquakes on people and property can be categorised into primary effects, these happen directly as a result of the earthquake.

And we could use an example of collapsed buildings for this.

So they're a direct consequence of this shaking.

Then we've also got secondary effects, and this happens because of the primary effects.

So if we think about our example here of the collapsed buildings, an example of a secondary effect caused by that could be fire caused by broken wires or gas pipes in the collapsed buildings.

So primary effects happen directly as a result of the earthquake.

Secondary effects happen because of the primary effects.

They're a knock-on consequence of the primary effects.

Which photo shows a primary effect of an earthquake? Well done, yes, it is the first one, a.

And this is a collapsed building.

The collapsed building could then lead onto other consequences, such as a fire.

Next check for understanding.

The secondary effects are those directly related to ground shaking.

Is this true or false? Well done, this is false.

Can you tell me why? Well done.

So primary effects are those that occur as a direct result of the ground shaking.

It's not secondary.

It's primary effects that was described here.

A seismograph detects and records the strength of ground shaking.

The higher the spikes on the graph, or the amplitude, the greater the magnitude, which means the stronger the earthquake.

We're now going to have a look at some of the primary and secondary effects of earthquakes.

First of all, we're going to have a look at damage to infrastructure.

So many homes, public buildings, roads, and bridges are vulnerable to collapse or damage when the ground shakes.

This can disrupt transportation and power supplies, hindering rescue and recovery efforts.

It can really slow down the teams trying to rescue people because they can't get the supplies to the location that they need to.

Injuries and deaths is our second primary effect.

Injuries can be harder to treat if health services are damaged by the earthquake.

Death tolls often climb after an earthquake, and this is because more deceased are recovered from collapsed buildings.

Secondary effects now.

So a tsunami would count as a secondary effect of an earthquake.

Tsunamis can be triggered if earthquakes under the sea shift sea water.

This sends destructive waves rippling out from the epicentre and causing flooding and damage to coastal areas.

Tsunamis are primary effects of earthquakes.

Is this true or False? Yes, it's false.

And why is that? Yeah, so the movement of the seabed as a result of earthquake displaces water, which creates the waves of a tsunami.

So they're not a primary effect.

They're a secondary effect.

We've also got loss of income here.

So building damage can mean that businesses temporarily close, affecting livelihoods.

The repair and reconstruction costs add to the financial costs for the government and for residents.

Our last secondary effect is the psychological effect on the people that are experiencing this earthquake.

And that can cause fear, stress, depression, and many more emotions among the population.

One of the things a lot of people can be very fearful about is the idea that there might be another quake which could cause buildings to collapse on them.

So many people after an earthquake are too scared to actually go back into buildings and might remain living in tents, for example, for quite a long time.

And this ties in with something called aftershocks, which we're going to hear about a little bit later in the lesson.

Time for a check for understanding now.

Which is not a secondary effect? Is it a, tsunami, b, loss of income, c, buildings collapsing, or d, fear and depression? Well done.

Yes, building collapsing is not a secondary effect.

It is a primary effect.

Time for our practise task now.

Our first task is to define primary and secondary effects.

The second task is to categorise these effects into primary and secondary.

So I've listed the effects I'd like categorised here, and then you have a table with primary and secondary outlined on there.

So all you need to do is put 'em in the correct column of the table.

Brilliant.

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

Well done, everyone.

So your answers may look like this.

For the first task, define primary and secondary effects.

So primary effects happen directly as a result of an earthquake, where secondary effects happen because of the primary effects.

Task 2, categorise the effects into primary and secondary effects.

So first of all, I had ground shaking, damage to infrastructure, injuries and death.

For the secondary effects, I had tsunamis, economic impact, and psychological effects.

Now we're onto the second parts of our lesson.

Why are some earthquakes more deadly than others? Perhaps the most important primary impacts that earthquakes are assessed by is death toll.

Factors which impact death toll include the magnitude, focus depth and epicentre location, the preparation and response, and the aftershocks.

So, first of all, we're going to look into magnitude.

It is one of the most significant factors in determining how deadly an earthquake is.

The more powerful a quake is, the more likely there will be a high death toll.

Now scientists use different scales to measure the energy released.

The most common one is the moment magnitude scale.

This table with Laura.

In 2024, did higher magnitude earthquakes cause more deaths? Let's have a look.

So this table shows us the first five deadliest earthquakes of 2024.

So the death toll is on the left-hand side.

Then our central column has magnitude, using the moment magnitude scale.

And then our third column has location.

Take a look at the table and see what you think.

Yes, in 2024, higher magnitude earthquakes did cause more deaths.

We can see here that as we look at the death toll column, the death toll drops as you go down each row.

And the same pattern is seen in the magnitude column.

The magnitude drops as you go down each row.

So, for example, the Ishikawa earthquake had 526 people losing their lives, and that magnitude was the highest at 7.

5.

So let's have a look at this in terms of a graph.

So we've taken it out of the table and put it into a graph to see if we can see any other trends and patterns.

Lucas has noticed that there is a huge difference in the number of deaths between the Hualien and Ishikawa earthquakes though the magnitude was not that different.

There must be more to it than magnitude.

Can you see that? Can you have a look at where that arrow is? The magnitude only increases a small amount.

However, the number of deaths increases a huge amount.

That's interesting, isn't it? Let's have a look at why that might be.

So there were some other reasons other than magnitude.

There was a shallow depth of focus in Ishikawa, the epicentre was close to a densely-populated area, and it triggered tsunamis and landslides as well.

Let's have a look at the focus depth.

So the closer the earthquake focus is to the surface, the stronger the surface shaking is likely to be.

You can see on the diagram the red circle onto the ground where the earthquake first emanates from.

And that is our focus.

The closer that is to the surface, the more shaking there will be.

That makes sense, doesn't it? So let's have a look at this diagram.

I have labelled on three earthquakes, a, b, and c.

Which of these earthquakes is likely to have the greatest impact? So their focus points are labelled by the letters.

Which one is likely to have the most impact? Yes, well done, it's a.

Why is that? It has a shallow focus, hasn't it? Epicentre location is another really important factor.

So where settlements are located near to the epicentre, more damage and deaths occur as the ground shaking is greater there.

The Ishikawa earthquake epicentre was near to the city of Wajima, where more than 2,000 houses collapsed, leading to fatalities.

You can see here on the map the location of the earthquake indicated by the large star.

And you can also see colours on the map which tell us more information.

If you have a look at the table at the bottom, you can see the estimated intensity of the earthquake in each of the different locations just by looking at the shaded colour.

Can you have a look now at this map? Which coastal location is likely to be worse affected? Is it a, b, or c? Correct, it's a.

Can you tell me why? Well done.

It's closest to the epicentre.

Very good.

How severe was the damage likely to be at Wajima? Can you use the key for this? Well done.

So the damage was likely to be moderate in Wajima, and that was because it was shaded this light orange colour, which shows us that the intensity was probably going to be around seven, and therefore the damage is likely to be moderate.

Next we're looking at aftershocks.

Aftershocks are lower magnitude earthquakes that happen in the days, weeks, or months after the main quake.

So they can't be a higher magnitude.

They have to be a lower magnitude.

But they are an earthquake and they are happening soon after a major quake.

So it's really rare for an earthquake to happen in isolation.

Normally there are aftershocks, and these can cause damage in their own rights.

They can prevent rescue efforts and lead to higher levels of fear and stress for the affected population.

We mentioned this before, didn't we, when we talked about the psychological impact, when we said that actually it can really stop people wanting to go back into their homes and into buildings.

The orange circles on this map represent the earthquakes in southern Turkey on the 6th of February, 2023.

This included 72 aftershocks experienced that day.

So it's one day with 72 aftershocks.

You can imagine that must be absolutely terrifying.

You're constantly on guard to see when the next quake might be.

Which statement is correct? Is it a, a dangerous earthquake event is when the ground shakes once, then the danger is over, b, further earthquakes may occur, known as aftershocks, and these can be dangerous for people and property, or c, aftershocks are significant and often greater magnitude than the main earthquake.

Well done.

Yes, so further earthquakes may occur, known as aftershocks, and these can be dangerous for people and property.

So a is incorrect, and that is because the earthquake doesn't just shake the ground once and then stop.

There's normally aftershocks.

And then c is incorrect because aftershocks are significant, that's true, but they're not of a greater magnitude than the main earthquake.

Right, preparation and response.

We're going to be looking at how being prepared can help to reduce the scale of the effects for an earthquake.

Countries with better funding should be able to prepare and respond better, but this is not always the case.

Some of the deadliest and costliest earthquake events have happened in high income countries, or wealthy countries.

So, in Japan, the 1st of September is known as Disaster Preparedness Day.

Each year, schools, businesses, and emergency services practise how they should respond to an earthquake.

So this is one example of an educational poster that encourages people to take cover during an earthquake to prevent injury from falling objects.

This is a good thing to know even if you don't live in an earthquake risk zone because nowadays many people travel, and it could be that we do end up in an earthquake risk zone at the wrong time, and we need to know this.

So our first thing to do is to drop, then cover either with your hand over your neck, or your arm over your head and neck, or under a table if you can, and hold on.

This prevents any falling debris from damaging your head and neck, which would be really vulnerable points and could cause you to lose consciousness, which would not be good.

If you go under a table, it means that even if the table collapses, that table is going to take the impacts of any falling debris.

And there's also going to be a pocket of air underneath that table, so that if the building collapses on top of you, then hopefully there will still be a pocket of air for you to breathe until the rescue teams come to get you.

True false.

Some of the costliest and deadliest earthquake events have occurred in high income countries.

Is this true or false? Well done, it's true.

Can you justify your answer? Good.

In 2004, more than 500 people died in the Ishikawa quake in Japan.

That's a prime example of a case study in which a wealthy country, such as Japan, still had many people die despite the measures that they've put in place to try and prevent that.

Time for our last practise task now.

First of all, I'd like you to plop the earthquakes using the data from the table.

I'd like you to use, probably a scatter graph would be the best one to use for this, just like we saw earlier in the lesson.

The second part of this task is to suggest why the Ishikawa earthquake had such a high death toll compared to other earthquakes in 2024.

I would like you to include the words magnitude, focus, depth, epicentre location, preparation, and secondary hazards.

Feel free to pause the video now so you've got some time to do this.

Well done, everyone.

I'm going to show you my answers, and you can just check them against yours and check if they look roughly right.

So, first of all, it was plotting the earthquakes using the data from the table.

So here we have what the graph should look like.

Does yours look like this? For the second part of the task, you were asked to suggest why Ishikawa earthquake had such a high death toll compared to other earthquakes in 2024.

Your answer may include, the earthquake in Ishikawa, Japan, had a high death toll for a number of reasons.

At 7.

5 on the moment magnitude scale, it was the highest magnitude earthquake.

Also, the location of the epicentre was close to the city of Wajima, meaning there was a larger population at risk.

In addition, there had been insufficient preparation for an earthquake of this magnitude as many older buildings did not withstand the shaking.

Lastly, secondary effects included a dangerous tsunami.

How did you do? Would you like to edit your answer at all? Time for our summary now.

Primary effects occur as a direct result of the earthquake.

For example, buildings collapse as a result of the ground shaking.

Secondary effects occur because of primary effects.

For example, a fire might be started if gas pipes are broken.

The severity of the effects of an earthquake will depend on magnitude, depth of focus, location of epicentre, aftershocks, as well as preparations for and the responses of people to the event.

Some of the deadliest and costliest earthquake events have occurred in high income countries.

I hope you've enjoyed today's lesson.

And I hope to see you next time.

Bye-bye.