All language subtitles for D D S02E04 Earthquakes 1080p AMZN WEB-DL DD2 0 H 264-playWEB_track3_[eng]

Little can prepare you
for the horror

of the deadly disaster
we focus on in this episode.

When the earth shakes,
buildings collapse

and the ground quite literally
opens up under your feet.

There’s absolutely no way

we can prevent
an earthquake happening.

The earthquake

is one of nature’s
most terrifying phenomena.

Throughout history,

there has been
a serious earthquake

almost every year,

and they have caused the death
of millions of people.

In this episode,

we feature
the Northridge earthquake

that struck Southern California
in 1994.

And the quake that devastated
Christchurch, New Zealand

in 2010 and 2011.

As well as the 2009 earthquake

that destroyed much
of the beautiful medieval city

of L’Aquila in Italy,

killing 300
and leaving 60,000 homeless.

With eyewitness accounts
and expert contributions,

we dig deep
into the fascinating science

and show the effects

of this destructive
and deadly disaster.

An earthquake is categorized
by any shaking of the ground

due to the action of seismic
waves in the earth’s crust.

So when an earthquake happens,

you get vibrations
sent out through the ground

in two different ways.

The first one,

which is felt at the surface
is called a P wave,

and that’s energy
traveling back and forth

from the earthquake’s source

to the surface
in this kind of orientation.

But the most damaging type
of seismic wave,

the one that causes damage
to buildings,

is called the S wave.

And that causes, sort of--

Um, that causes vibrations
to occur

in this sort of up-and-down
and side-to-side motion,

which really strongly
shakes the ground.

But what exactly causes
the powerful shock waves

that create so much mayhem?

An earthquake occurs
when stresses build up

over time on a fault.

And when that fault slips,

when one side of a fault
moves past the other side,

then that radiates
seismic energy.

It radiates waves
and the ground shakes.

An earthquake is the very
rapid movement,

wavelike movement,
of the earth’s surface.

And that can be caused by,
for example,

an undersea landslide.

It can be caused
by a volcanic eruption.

It can be caused by tectonic
plates moving past each other.

But essentially, it’s the very
rapid release of energy

that’s being felt
on the earth’s surface.

The part of the earth that
we live on is called the crust.

It’s as little as 5 kilometers
thick under the ocean

and between 45 to 50 kilometers
thick on the continents.

This crust is floating on
a soft mantle of molten rock.

And far from being solid,
the crust is actually made up

of vast,
separate tectonic plates

that are moved around
by the currents

in the molten rock
beneath them.

Where the plates meet,

they slide past each other

at the rate
of 3 to 5 centimeters a year--

About the same speed
as your fingernails grow.

But the movement
is not steady.

Earth’s plates
are shuffling around.

And as they interact
with one another,

you develop
what are called fault lines.

That’s where the earthquake
happens is on the fault line.

The plates may be
locked against each other

for many years until the strain
becomes too great,

and they suddenly
slip along a fault line,

sometimes for several meters
all at once.

The cracking rock sends out
shocks of seismic waves

in all directions,
which are felt as earthquakes.

Every year there are about
50,000 earthquakes

that are powerful enough to be
felt by anyone in the vicinity.

Around 100 are so violent

that they will damage
any nearby structures.

The shaking that is caused
by an earthquake

is not just dependent on
the magnitude of an earthquake,

but is also dependent
on how close you are

to a fault that failed.

When such a violent earthquake

occurs in the vicinity
of a village, town or city,

it is almost certain
to result in death and injury.

Earthquakes were largely a mystery

until the emergence
of the science of seismology

at the start
of the 20th century.

Since then, we have gradually
begun to understand

why and how earthquakes occur.

It had long been noticed that
earthquakes tended to occur

along clearly defined bands

that crisscrossed
the world’s surface.

Then came the discovery

that the surface
was not actually solid

but consisted
of moving sheets of rock

which were named
as tectonic plates.

The areas
where these vast plates

rubbed against each other

were seen to coincide
with the belts

where earthquakes
most often took place.

So the largest earthquakes
worldwide

happen in subduction zones.

So these are at the boundaries

where tectonic oceanic plate
meets a continental plate.

And essentially,
the oceanic plate

is pushed down
underneath the continents.

These faults are very,
very big,

and the earthquakes that happen
on them can be very large.

The largest earthquakes

can be magnitude 8
to magnitude 9 earthquakes,

such as the 2004
Sumatra earthquake

or the 2011 Tohoku earthquake
in Japan.

One of the most notable belts
of activity

is one that goes around
the edge of the Pacific Ocean.

This is where nine out of every
10 earthquakes occur.

It accounts for earthquakes
in many Pacific nations,

including New Zealand,
Japan, Alaska,

and along the vast coastline

of both North
and South America.

The area along this belt
is also known

for its volcanic activity,

giving rise to its popular
name: the Ring of Fire.

Another belt
of seismic activity

is the Alpine-Himalayan
Orogenic belt.

This stretches from the
Mediterranean through Asia

all the way to the East Indies.

As its name suggests,

the Alpine-Himalayan belt was
responsible for the formation

of many mighty mountain ranges,

from the Atlas
in North Africa,

the Alps and the Caucuses,

all the way to the Himalayas
in Asia,

which includes Mount Everest,
the highest peak in the world.

An earthquake is fundamentally
movement on a fault,

or a line of weakness
within the crust.

And that movement,
it happens many, many times

over thousands of years,
millions of years.

That can generate changes
in the ground’s surface.

If this is
your ground surface,

a normal fault will mean
that the ground

will move steadily
like this over time.

So, what that means, is you’ll
get mountains being generated

on this side and flat plains
being generated on this side.

The earthquakes from this belt

release around 15 percent
of the world’s seismic energy.

The earthquakes
in the continental regions

are generally smaller,
so magnitude 6 to magnitude 8.

But actually,
they, paradoxically,

they lead to a greater number
of deaths worldwide.

The type of earthquakes

that release
the huge amounts of energy

that cause major tremors

are called
tectonic earthquakes.

In 1906,
San Francisco was rocked

by such an earthquake

after a rupture
in the San Andreas Fault,

which forms part
of the Ring of Fire.

The ground shifted
horizontally

by as much as 6 meters
along a 430-kilometer stretch,

releasing a colossal amount
of energy.

Study of this earthquake

gave rise
to the Elastic Rebound Theory.

It states
that these earthquakes

occur when a mass of rock

is no longer strong enough
to hold the strain it is under,

and suddenly gives way
along a fault line.

As the two masses of rock
rip in opposite directions,

they may stick together
for a moment

before sliding apart again.

This irregular coming apart

is what causes
the waves of vibration

that can be seen
in the shaking of buildings

during an earthquake.

Similar seismic waves can be
set off by human activity

such as mining,
fracking for gas

and the underground testing
of nuclear devices.

Research carried out

in order to discover when a
country had run a nuclear test,

helped expand our ability
to detect seismic activity.

Earthquakes give rise

to some of the most
dramatic effects

to occur in the natural world.

They cause extraordinary shifts
in the ground,

which may rise,
fall and open up,

leading to landslides
and mudflows.

Buildings, bridges, pipelines
and other infrastructure

may be damaged
or destroyed.

Anything can be damaged
in an earthquake.

That can cause a whole host of
problems after the earthquake.

Devastation is often amplified

when buildings are built
on soft soils, sand or mud,

as this is easier for seismic
waves to travel through.

Compared to other
natural disasters,

earthquakes
are particularly dangerous.

Per event, we have more people
killed in earthquakes

than we have
in a flood or in a fire.

That is per number of people
affected by an event.

And the simple reason for this

is they’re very difficult
to predict,

but also there are other reasons

because earthquakes can trigger
other natural disasters.

They can trigger flooding.
They can trigger landslides.

They can trigger tsunamis.

Before the invention
of the seismograph,

earthquakes were measured

simply by the amount
of shaking of the ground.

With the invention
of the seismograph in 1875,

it became possible to measure

the intensity of movement
against a time scale,

so you could tell
when an earthquake had occurred

and how strong it was.

Then, in 1935,

a scale was developed
by Charles Richter,

which became known
as the Richter Scale.

For the first time,
scientists were able

to accurately compare
different earthquakes.

However, the Richter Scale
was found to be less precise

when measuring
the most powerful earthquakes,

and so a new system
was developed.

This new system measured
the distance a fault moved

and multiplied it by the force
required to cause this movement

and was called
the Moment Magnitude Scale.

On this scale,
a magnitude 1 earthquake

releases as much energy
as 170 grams of TNT.

That’s a very small tremor.

In fact,
you would not be able to feel

anything under 2.5
on the Moment Magnitude Scale.

By comparison, a magnitude 8
is the equivalent

of exploding 5.4 billion
kilograms of TNT.

That magnitude of earthquake

would completely destroy
anything near its source.

The magnitude scale
is logarithmic.

So for every unit of magnitude,

you release 30 times
more energy.

Plus two units of magnitude,

you release a thousand
times more energy.

The most powerful earthquake
ever to hit the United States

occurred in Alaska in 1964--

A magnitude 9.2.

Alaska is the area
most prone to earthquakes.

It endures a magnitude 7
earthquake almost every year.

The largest measured earthquake
anywhere in the world

was a magnitude 9.5
that struck Chile in 1960.

It killed thousands of people

and left millions homeless.

Most earthquakes occur in areas
that are known danger zones.

But sometimes,
earthquakes can be triggered

by hidden fault lines

lurking beneath the surface

on which people
have built their homes,

offices,
hospitals and schools.

Each individual fault might
only fail every hundred years,

every thousand years.

But it could still actually be
very hazardous.

So there are lots of faults

that are located, you know,
right next to a city,

but we actually don’t
even know that they exist.

Just such a concealed fault

ruptured in Los Angeles
on the 17th of January 1994.

It was 4:31 in the morning on
Martin Luther King Junior Day.

The San Fernando Valley

lies just over 30 kilometers
from downtown Los Angeles.

In the predawn darkness,

many in the densely populated
community of Northridge

were no doubt planning
to use the federal holiday

to catch up on some sleep.

But their calm was shattered

by a powerful
magnitude 6.7 quake.

It shook the ground
for a terrifying 40 seconds.

The amount of energy a magnitude
6.7 earthquake releases

is around equivalent
to what was released

during the Hiroshima
atomic bomb.

Um, so that amount of energy

directly beneath a large city
at relatively shallow depth

can actually cause quite
significant ground shaking

and result in damage.

Most earthquakes

occur less than 80 kilometers
under the surface,

but the hypocenter
of the Northridge quake

was just 20 kilometers
underground,

making this
a very shallow earthquake,

which released
a colossal amount of energy

onto the nearby surface.

The shocks were so powerful

they were even felt 440
kilometers away in Las Vegas.

The earthquake shook the ground
violently from side to side,

as well as up and down,
causing catastrophic damage.

That fault moved in
what we call a thrust movement.

So we have a geological fault
like this:

And then one side of that fault
moved upwards.

I mean, the earthquake lasted,
what, 10, 15, 30 seconds.

Well, it lasted four years
for me and my mother.

She’s 80 now,
and I don’t know how many...

In the immediate aftermath,

20 people were reported dead
and 1000 injured.

But with many unaccounted for

and feared
trapped under debris,

it soon became apparent
that the death toll would rise.

Most people die in earthquakes

because of building collapse.

It’s not the earthquake
that kills people.

It’s the building.

Rescuers began pulling people

out of the rubble,

and they were quickly joined

by the emergency services.

We couldn’t get out.

You couldn’t get out?

We couldn’t get out.

If we hadn’t been dragged out
of there,

we’d have never got out.

They told us
when we moved in

it was an earthquake-safe
building.

Several apartment buildings
caved in,

including the Northridge
Meadows apartment complex

where 16 people
lost their lives

when their homes caved in
on top of them as they slept.

They all lived
on the first floor

of the stucco building,

which collapsed
into the open void

of the car parking area
below them.

This apartment building went up
2 feet, over 2 feet

and dropped down 12,
and the rest of it was gone.

When the earthquake hit,
I knew immediately

it was different than all
the others I’ve been in.

Very strong. At one point,
I was thrown down.

I think that’s when the two top
floors came down the first.

The quake caused
catastrophic damage

to the city’s
infrastructure.

Electricity failed,

plunging the city
into blackout.

Water mains burst,
flooding the streets.

Gas from ruptured mains
was set alight, causing fires.

All the airports, including
Los Angeles International

were immediately closed.

Eight hospitals
were so severely damaged

they had to be evacuated.

Doctors were forced to perform
lifesaving surgery

in triage centers
out in the open.

The area worst hit
was the San Fernando Valley

where 3 million people
were affected by the quake.

The emergency services
performed heroically

but were under
tremendous strain.

They brought in sensitive
listening devices

to locate survivors
amongst the rubble.

By sheer luck,

the earthquake
occurred at night,

limiting the casualties

which could have been greater
had it occurred in the day.

I know there was
this large scoreboard

at a sports stadium
which collapsed.

Because it was
4:30 in the morning,

there was nobody in the stadium,

but if there’d been
a sports event going on,

a lot of people would have
been injured or killed.

A parking lot
in the local shopping center

was completely destroyed,

but as it was empty,
no one was hurt.

There was extensive damage
to the highways.

Seven major freeway bridges
collapsed.

A policeman was killed

when his motorbike pitched off
the edge of an overpass.

Another factor limiting
the number of casualties

was that buildings
had been constructed

to strict safety codes

following the Sylmar earthquake
of 1971.

Although every building
constructed since that time

survived this latest
earthquake intact,

much of Northridge did not.

Mayor Richard Riordan
declared a state of emergency

and imposed an evening curfew.

However,
there were reports of looting

and warnings
that the earthquake

might not even be over.

When an earthquake occurs,

it may not release
all its energy at once.

We have now had
more than 6000 aftershocks.

This is because
faults may rupture

both before and after.

And these aftershocks

are sometimes almost as severe

as the original earthquake.

Aftershocks can occur over quite
a protracted period of time,

partly because aftershocks
can trigger

aftershocks of their own,

but also because there are
other processes operating.

For example, fluids might be
moving through the subsurface

driven by the first earthquake

that then might, in turn,
put stress on smaller faults

and trigger extra earthquakes.

Despite the fear
of aftershocks,

people were told
that wherever possible,

by far the best thing to do
was to stay in their homes.

Damage from the earthquake
was widespread.

The Santa Monica
beach community

was particularly
badly affected.

It is built
on much less stable ground

and although
it was relatively far

from the epicenter
of the quake,

it suffered
violent ground tremors.

There’s always earthquakes
around here

but nothing like as bad
as this one.

I didn’t expect
anything like this.

The Santa Monica Freeway
collapsed,

fouling up Los Angeles traffic
for months.

Because we can’t get out,
we can’t get in,

and so we have to go
way east to go west

and way west to go east.

You have to go around
so many different areas,

and you don’t know where
you’re going half the time.

Many had to struggle
through the ravaged city

for four hours in order to find
hospitals and medical care.

The death toll
of the Northridge earthquake

was approximately 60
and 9000 people were injured.

Eighty-two thousand buildings
were damaged or destroyed,

while over 20,000 people
had to leave their homes.

California dreaming is dead.

The earthquake
occurred on a fault

that had been
previously unknown--

A so-called
"blind thrust fault"

that was hidden under
the uppermost layers of rock.

This is in no way a part
of the San Andreas Fault system.

This is part of the--

A completely different
set of plate movements

that are peculiar
to Southern California.

Experts have since found
other such buried faults,

including one that lies right
beneath downtown Los Angeles,

underlining the vulnerability
of the millions of people

who live and work in the area.

So there’s lots of faults that
are particularly quite small

in the continents

that may only have an earthquake
every thousand years

or tens of thousands of years.

So this means
that there’s lots of faults

that won’t necessarily have had
an earthquake in living memory,

but actually still pose
a very significant hazard.

President Clinton
visited Northridge

to survey the aftermath
of the quake.

Having witnessed
the devastation himself,

he requested Congress release
$6.6 billion U.S. dollars

in relief aid.

Unfortunately,
it’s going to take a while.

It’s probably going to take
as much as a year.

It doesn’t take very long
to demolish

a structurally
damaged portion,

but to replace it can take
as much as a year, we hope less.

Overall, it cost in the region

of $42 billion U.S. dollars
to repair the city,

making this one of the most
expensive disasters

ever to hit America.

So if you had
a similar earthquake

in a similar area
right now,

when there are even
more buildings in the area,

the damage will be many orders
of magnitude higher.

At the time
of the Northridge quake,

Southern California
had few systems

monitoring the tectonic plates

responsible for causing earthquakes.

Since the disaster,

several agencies,
including NASA,

have set up
an integrated network

of over 250 GPS stations
across California and Mexico,

with the aim of developing

an earthquake
early warning system.

However,
earthquake early warning

is really
a misleading term.

Current systems only kick in

when an earthquake
is already taking place.

But they do enable you to know

how strong an earthquake
is in real time

and then assess how far
the effects will be felt

in order to warn communities
within the danger zone.

In 2018,
the U.S. Geological Survey

readied a new
early warning system.

This can detect the very early
phase of an earthquake

and give warnings
of up to a minute

before the major tremors
strike.

That’s enough time
to slow down or stop trains,

shut down
dangerous industrial operations

and give people a chance
of getting to places of safety.

For earthquakes, if you have
just a few seconds of warning

before that strong
ground shaking occurs,

you might be able
to protect yourself

by getting under a table
or a desk or a doorway

and that can actually
be the difference

between life and death.

In 2019,

technology took
another leap forward

with the development
of a mobile app

to alert
Los Angeles county residents

of earthquakes
of a magnitude 5.0 or more.

And there is no doubt
that early warning is needed.

The whole of California

straddles the infamous
San Andreas Fault,

which runs for 1200 kilometers

along the entire length
of the state.

It was 1857

when the southern part
of the fault last ruptured.

San Francisco, which lies
further north on the fault,

burned for three days after
the big earthquake of 1906.

With such an active fault line
running through California,

it isn’t a question of if there
will be another earthquake,

but when.

Another New World city,

Christchurch in New Zealand,

is similar to San Francisco
in many ways.

Christchurch had its first
contact with Europeans

when Captain Cook
landed there in 1770,

just a year after the Spanish

first sighted
San Francisco Bay.

Both cities are situated
on fine natural harbors.

And both are in areas prone
to violent seismic activity.

But as with San Francisco
and so many other cities,

located in places known

for the dangers
of deadly disasters,

the advantages of its location

outweighed the risks
posed by frequent earthquakes.

Now, Christchurch,
situated on the south island,

is New Zealand’s
third-largest city

with a population
of nearly 400,000.

Christchurch is a lovely city.

It’s on the east coast of the
south island of New Zealand,

um, a great,
vibrant place to be.

It’s an important
industrial center

as well as a mecca for tourists
with its surf beaches,

modern architecture,

heritage buildings,

museums and galleries.

Despite lying
on a major fault line,

for most of the 20th century

through to the first decade
of the 21st,

Christchurch enjoyed
a long period of calm.

On the 16th of November, 1901,

the city suffered an estimated
magnitude 7 earthquake.

After this,

there was relatively
little seismic activity

for more than a hundred years.

But that calm
was shattered when,

on the 4th of September, 2010,

at just after 4:30
in the morning,

Christchurch was rocked
by a magnitude 7.1 earthquake.

It occurred 10 kilometers
below the surface

in a previously unknown fault

some 40 kilometers
west of the city.

People were jolted awake
as the first phase of the quake

caused the ground
to shake violently.

People checked on loved ones

and tried
to get out of buildings

to the safety
of open ground.

As aftershocks continued,

parts of the ground liquefied.

Some were badly injured.

Buildings and infrastructure
were seriously damaged.

But thankfully,
there were no fatalities.

The hazard in that region
thought to be smaller

than it actually was.

As residents worked to repair
their battered city

they were hampered
by frequent aftershocks.

New Zealand is quite an
interesting place tectonically.

So in the north part
of the north island,

we’ve got subduction,

where you’ve got the Pacific
plate sinking into--

Sinking beneath
the land of New Zealand.

But you’ve also got subduction
in the south.

But that happens
in the opposite direction,

so the Australian plate
is sinking there.

And so you’ve got
these two regions,

which are basically
doing this:

And so in the middle,

you have to have some sort of
fault to accommodate,

to absorb
that opposite motion.

The population heaved
a collective sigh of relief.

It seemed as if they had
escaped the full fury

of what an earthquake
could unleash.

But the relief
was short lived.

One Tuesday afternoon
just over five months later,

as the people of Christchurch
were busy at work,

attending school or college,

going about their shopping,
or having lunch,

one of those aftershocks
struck close to the city

at a depth
of only 5 kilometers.

The 2010 Darfield earthquake

released 10 times
the amount of energy

as the magnitude
6.3 Christchurch earthquake.

But the Christchurch earthquake
was so much more damaging,

because it happened
right underneath

the city of Christchurch.

Many of the buildings
that had been damaged

in the previous earthquake

collapsed completely.

The damage that’s been done
to our infrastructure,

I’ve got to say, it’s massive.

This has taken us,
not just back

to the minutes
after the earthquake

of the 4th of September
last year,

it’s taken us further back
than that.

Buildings were
severely damaged or demolished

but there were not many
serious injuries.

People in the downtown
business district of the city

were not so fortunate.

The Canterbury
television building,

a six-story office block
full of workers,

completely collapsed.

One hundred and fifteen of them
lost their lives--

More than two-thirds
of the 185 people

that were killed
in the earthquake.

Around the city
and in the suburbs,

people were injured and killed
by toppling bricks,

masonry and rockfalls.

Two city buses were buried
beneath falling walls,

killing eight people,

while some were killed

by boulders tumbling away
from cliffs,

triggered by aftershocks.

Tragic stories to be told about
Christchurch at the moment.

We’ve only lost a house,

but people
have lost their lives,

so, you know, we’re lucky.

Children attending school,

who had been
repeatedly drilled

on how to react
to an earthquake,

quickly adopted the "Turtle--"

Dropping to the ground
and covering their heads.

Thankfully, no children were
seriously hurt or killed

in any school building.

New Zealand is really good
at earthquake preparation.

They have excellent
building standards.

People are drilled in school
and at home.

And everyone is
kind of ready for an earthquake.

But here, they weren’t ready

for an earthquake that happened
directly under the city.

In the immediate aftermath
of the quake,

people rushed to find friends
or loved ones.

Others stayed
where they were most needed.

The complication is...

we have to go really,
really slowly and carefully.

So every single step of the way,
we are conscious

that there could be somebody
literally behind a desk

or a chair or whatever else.

Many gathered around

the stricken Canterbury
television building

where the majority
of casualties occurred.

As well as
the Pyne Gould building

where 18 people had died.

They helped the survivors,

many of them badly injured.

In total,
some 16,000 properties

were left severely damaged
by the violent shaking.

The Christchurch earthquake

may have also caused
more damage,

because buildings
would have been weakened

by the shaking
from the Darfield earthquake.

The Christchurch earthquake

also caused
a terrifying phenomenon

known as liquefaction.

What happens to buildings
during an earthquake

depends very much
on what they’re built.

If you built on solid rock,

the ground doesn’t shake
so strongly

as if it’s built
on sandy or muddy ground.

Parts of Christchurch were built
on a drained coastal swamp

and that shook
particularly violently

during the 2011 earthquake.

And the ground
actually liquefied.

Mud oozed up between
cracks in the pavement

and buildings sagged
because of the uneven nature

of the liquefaction
beneath them.

One of the worst examples
of this effect

occurred during the 1976
Tangshan earthquake in China

when an area of more
than 2400 square kilometers

was subject to liquefaction,

causing terrible damage to
the southern part of the city.

In the Mexico earthquake
of 1985,

the ground beneath the center
of the city liquefied,

even though the epicenter
of the earthquake

was over
350 kilometers away.

Liquefaction can even

induce soil to spew out
of the ground in sand volcanoes

and cause landslides.

In a 1964 earthquake
in Anchorage,

liquefaction resulted in a landslide

that destroyed 75 homes.

Christchurch was a really
devastating earthquake,

because we really did not know

about the location
of a fault underneath the city.

Christchurch is built to be
very seismically resistant

to the most likely culprit.

So the most likely earthquake

is going to come
from the New Zealand Alps

and they’re quite far away.

The type of shaking that we
would expect from those faults

is very different from the type
of shaking that they did get

in the Christchurch earthquake.

In Christchurch,

the fatal combination
of ground shake,

liquefaction and landslide

resulted in damage to a huge
proportion of all properties

in the greater
Christchurch area.

Older brick and mortar
constructions,

were especially vulnerable
to shaking.

Many of the city’s
iconic heritage buildings

were either damaged
or destroyed.

Both the Anglican
and the Catholic cathedrals

suffered extensive damage.

And the clock
in the famous Victoria Tower

was frozen at 12:51,

bearing lasting testament

to the very moment
the quake struck.

The cost to put right
the devastated city

was estimated
to be upwards

of $20 billion
New Zealand dollars.

Following the earthquake,

even five years
after the event,

the city has not
really recovered.

After the disaster,

the New Zealand government
set up a commission

to investigate the buildings
that were damaged

in the Christchurch
earthquakes.

Following months of inquiries,

the then-Prime Minister,
John Key,

stated that 175
out of the 185 deaths

had been caused
by structural failures.

The design and construction
of the CTV building,

where 115 lost their lives,

came under severe criticism.

If a modern city,
like Christchurch,

had been left
shockingly vulnerable

to the threat
posed by earthquakes,

what chance would a city
built 800 ago have?

That’s exactly what is revealed
in our next case study.

Many regard the beauty
and historical importance

of the 13th-century city
of L’Aquila

to be on a par
with Florence and Salzburg.

The city is situated on a hill
in the Apennine mountains,

about 130 kilometers
northeast of Rome,

overlooking the Alterno River.

Behind it’s medieval walls

lie a host of baroque
and renaissance churches,

with narrow streets giving out
onto magnificent piazzas.

L’Aquila itself sits a fairly
wide, flat mountain basin,

and it’s surrounded
by mountains on most sides.

And that difference
in the topography--

The mountainous regions
versus the flat regions,

in Italy
and many places worldwide.

is directly due
to the movement on the faults

that results in-in earthquakes.

L’Aquila is no stranger
to seismic disaster,

having been largely destroyed
by two previous earthquakes

in 1461 and again in 1703.

And a more recent,
but relatively minor quake,

in 1958.

Historical data on earthquakes
can be extremely useful,

because where we’ve had
earthquakes in the past,

we’re very likely to have
earthquakes again in future.

Then, on the 6th
of April, 2009,

at 3:32 in the morning,

the city was rocked
by a magnitude 6.3 earthquake.

It lasted for 20 seconds,
causing terrible damage

as well as death and injury
to the terrified inhabitants.

Much of Italy lies on the cusp

between the giant European
and African tectonic plates,

and has suffered
many earthquakes.

In such a seismically
active area

there are frequent,
smaller tremors.

This was the case
in the months leading up

to the devastating earthquake
in L’Aquila.

In October 2008,
the year before the disaster,

dozens of tremors
were felt in the city

and the surrounding areas.

Ninety-nine out of 100 times
a small sequence of earthquakes

is not going to result
in something big.

During the beginning of 2009,

these "seismic swarms,"
as they are called,

continued to plague the city.

Aftershocks are commonly smaller

than the earthquake
that triggered them,

but they can actually
also be larger.

And that’s expected for some
smaller amount of earthquakes.

This is actually likely the case
in L’Aquila

where there was a swarm
of smaller seismicity

in the weeks, months
before the L’Aquila earthquake.

It was not surprising

that many of the medieval
buildings disintegrated.

What did startle
and stun experts

was the damage
to modern buildings,

even those like the new
San Salvatore hospital.

It was lauded
as being earthquake proof

when it first opened
in 2000--

Just nine years later,
it lay in ruins.

Doctors had to treat victims
of the earthquake

along with their regular
patients in a courtyard.

In L’Aquila, most of the modern
buildings collapsed

and were later found
not to have been built

to the regulations in place.

Many young people
lost their lives.

University students
were killed

when a dormitory
they were housed in collapsed.

Significant damage
in L’Aquila

happened on buildings that were
built in the ’70s and ’80s,

after a good code for
earthquake resilient buildings

had been established.

So those buildings
that were built later,

and should have been resilient,

should have been
reinforced concrete

and had much more resistance
to shaking, they fell.

And they caused many deaths.

In Onna, which was one
of the small villages

right on top of a fault,

the death toll there
was around 12 percent.

So about 12 percent of people

living in that town
unfortunately died.

The damage to the cultural
heritage of the city

was said to be incalculable.

Part of the basilica
of Santa Maria di Collemaggio,

caved in completely.

Later, in June,

the European Commission

proposed granting
494 million euros

to fund the repairs
and recovery of the region.

Aftershocks continued to be
felt throughout central Italy,

a constant reminder
to the whole nation

of the terrible situation
being endured

by their fellow citizens
in L’Aquila.

Many who had lost their homes
had been rehoused,

although thousands were forced
to remain in temporary camps.

It’s difficult.

We have a tent,
and we stay--

We don’t know how long.

Next week,
maybe one month.

The city’s historic center

including the Basilica
of St. Bernardino

as well as the city hall
remained closed to the public

long after the earthquake,

shut behind a sealed off
"Red Zone,"

while they were first made safe
and then painstakingly rebuilt,

a process which appeared later

to have been hampered
by corruption

in the awarding
of public contracts.

So I visited L’Aquila about five
years after the earthquake

and actually,
it was really shocking to see

that there was still extensive
damage in the city center.

That really
was a loss of identity

to many L’Aquilans
and people that lived there,

to have such damage
to their historical city center.

In the aftermath
of the disaster,

survivors began to question

why they had not been warned
of the impending catastrophe.

The prediction of earthquakes

has long been the holy grail
of seismology.

Predicting earthquakes
is currently impossible

and may always be impossible.

While early warning systems

are capable of giving people
vital seconds

to get out of buildings
or assume safe positions,

longer-term warnings that
would enable mass evacuation,

such as have been possible for
disasters such as hurricanes,

have proved elusive.

There is no way to know
exactly when and where

an earthquake may happen.

Um, we can do
a fairly decent forecast

of where earthquakes
might happen.

So we can say,
"Yeah, this place

is very likely
to have some earthquakes,"

but we can’t say
when it’s going to happen.

So the word prediction just
doesn’t apply, unfortunately.

The whole issue of scientist’s
ability to raise the alarm

about earthquakes
was brought into sharp focus

after the L’Aquila quake.

Six scientists,

all internationally respected
seismologists

and geological experts,

along with
a government official,

were charged
with multiple manslaughter.

They were all members
of a national commission

for the forecast and prevention
of major risks.

Prosecution alleged that they
had underestimated the risks

posed by tremors
that had been felt

in the months before
the devastating earthquake

and given "inaccurate,
incomplete and contradictory"

information to the public.

Their advice was that there
had been this background

swarm of very small earthquakes

and what they said was that

whilst that could lead
to a larger earthquake,

and they certainly
couldn’t rule that out,

in most cases,

those swarms don’t normally
lead to a larger event.

The accused
all vigorously protested

the contentions
of the prosecution.

The trial of the L’Aquila
scientists was controversial

because the earthquake experts,

who met at the meeting six days
before the L’Aquila event,

actually gave very clear,
measured,

reasonable and scientifically
accurate advice.

One of the defendants,
Bernardo de Bernardinis said:

"I believe myself to be
innocent before God and men."

When they were found guilty

and sentenced
to six years in prison,

scientists from around
the world were horrified.

They felt that the trial
set a shocking precedent

which would deter experts from
sharing important knowledge,

ultimately leaving the public
less safe.

I think the trial
sets a dangerous precedent

and in particular,
has the potential to create

quite a strong chilling effect
that discourage scientists

from engaging with policymakers,
from engaging with the media

on these really important
humanitarian issues.

Enzo Boschi,
one of those found guilty,

said that he did not understand
what he had been convicted of.

Scientists maintained
that it had not been possible

to predict
what would happen in L’Aquila.

This opinion was validated

when the defendants
successfully appealed,

and their sentences
were quashed.

It’s hugely important

that scientists
engage with policymakers

and with the general public

to help feed into
preparations for emergencies

and building codes

and to make sure
that the actions

that take place
at a government level

are actually based on
a solid foundation of science.

Earthquakes kill and destroy
by causing fires,

ruptures in the ground,
landslides and tsunamis.

But more individuals die

as a result
of the collapse of buildings

and other man-made
structures.

The most important thing
that could be done worldwide

to reduce earthquake deaths

would be for governments
to enforce building codes.

So by far the most effective
action that can be taken

to protect people from
this type of deadly disaster

is to construct buildings

capable of withstanding
the vicious ground movements

that occur during a quake.

Huge advances in this field
have been achieved.

Shock absorbers made of rubber

can be incorporated
into the building’s foundation

to soak up the violent tremors.

Steel frames within buildings
are now designed

to allow the whole construction
to sway during an earthquake.

Open areas in the immediate
vicinity of buildings

have been factored
into planning

so that people
who can evacuate

have safe spaces
to congregate in.

The chance to live in
an earthquake-proof building

would be some comfort
for the millions of people

that live near
the world’s fault lines.

Without the ability to
accurately predict earthquakes,

it represents
the best chance we have

of surviving this particular
kind of deadly disaster.