Kind: captions
Language: en
this is the world's largest earthquake
simulator it's called e defense its huge
Shake table can support a 10 story
building and then move it in all
directions with the force of the world's
most destructive
earthquakes e defense has conducted more
than a 100 tests subjecting all kinds of
buildings to different simulated
earthquakes all to learn how to make
buildings more earthquake
resistant
part of this video was brought to you by
Shopify more about them later in the
video on the 17th of January 1995 at
5:46 in the morning an earthquake struck
the city of coob Japan it took Everyone
by
surprise Japan is one of the most
seismically active countries in the
world it sits on the boundary of four
tectonic plates and 90% of all
earthquakes and almost all of the
powerful ones happen at tectonic plate
boundaries but coob isn't near one this
earthquake was caused by an interplate
fault essentially a crack in the Earth's
surface that isn't at the boundary of a
tectonic plate this fault hadn't
produced any earthquakes for around a
thous years so the city was completely
unprepared the hiest
for the Quake measured a magnitude 6.9
just under the definition of a major
earthquake despite this the earthquake
killed more than 6,000 people and left
another 300,000 homeless more than 80%
of the fatalities were caused by the
collapse of buildings the total economic
cost was estimated at80 billion
US in response the government gathered
scientists for a conference on
earthquake disaster prevention and there
they agreed to build the largest
earthquake Simulator the world had ever
seen so I sent Peter to Japan for an
exclusive look inside this
facility so we're entering the world's
biggest earthquake simulator as they're
about to do an experiment so let's go
right now there's eight concrete walls
that they're going to feed seismic
signals into the shake table and they're
going to see which ones are the most
sturdy so the seismic data that they're
going to feed in is from the El Centro
earthquake which was an earthquake that
happened on the 18th of May 1940 it was
a 6.9 magnetude earthquake and it's one
of the first ones that we actually have
seismic data
from okay things are wow wow wow wow wow
wow wow oh
oh okay it's it's it's just really cool
to see such a big structure structure
kind of moving that far and that fast
wow the first test that I actually saw
uh it was on the schedule and it said
white noise so the white noise is just
all different frequencies low
frequencies high frequencies everything
in between they make this big deal
they're like oh one minute like and then
they do like the 10-second
countdown 3 2
1 and then it's just like functionally
nothing we flew all the way to Japan to
to see this so let's hope at least one
wall falls
down and I couldn't figure out why for a
long time all the structure has natural
frequency when the structure is damaged
natural frequency becomes shorter so by
inputting White Noise these components
of wide range of frequency so we can
find natural frequency of building so so
F okay input White Noise fast and after
that we inut earthquake motion and then
we inut we usually input another white
noise so we can find the change of
natural
frequency at the center of e defense is
a 20 m x 15 M Shake table which weighs
800 tons on each side there are five
hydraulic actuators which push the table
table side to side and the whole thing
is supported by another 14 actuators at
the bottom which move the table up and
down the whole facility is massive there
is one Warehouse where the shake table
is housed but it's in such high demand
that all the buildings are constructed
in a separate warehouse and then
transferred across then there is a whole
area full of giant engines and nitrogen
storage tanks just to power the shake
table oh my God this is a huge engine
using this setup the scientists can
perfectly simulate past earthquakes and
determine their effects on different
buildings the shake table can hold
masses up to 1200 tons and jolt them
with accelerations up to 15 m/s squared
that's over 1 and 1/2
G's now I know jet fighters can pull
like 10 G's as they turn but it's
another story if you're in your house
and the floor starts accelerating faster
than a falling
object the goal of the shake table is to
realistically simulate earthquakes to do
this you need two things a way of being
able to apply enough force in a precise
and controlled way and the signal data
from real
earthquakes this is how they do it I are
you okay at high elevation PR uh let's
see so this one is actuator the
actuators themselves are hydraulic
inside each one there's a 3010 piston
driven by High Press oil this is massive
this is I don't know a meter meter and a
half in diameter but to generate the
pressure needed to operate the shake
table and sustain it for minutes at a
time e defense needs huge reserves of
pressure storage that's why there's a
whole section of the warehouse with
massive high pressure storage tanks full
of nitrogen we have 20 of these red
spherical shape accumulators so we
accumulate the pressure to pressurize
these tanks liquid nitrogen is pumped in
from a large storage tank outside and as
that liquid warms up it turns into a gas
and expands 694 times its original
volume it's relatively easy to obtain
very high pressures with nitrogen then
when the pressure is needed it's
transferred to the oil using a bunch of
Pistons as the test runs the oil is
pumped to the actuators by these giant
engines but even they can't sustain the
the pressure needed to operate the shake
table for very long and so the nitrogen
pressure reserves mean that the shake
table can deliver a consistent amount of
force from the start of the test right
to the
end while a test is run the pressurized
oil needs to be pumped to the actuators
by the engines the flow to each actuator
is controlled by electronic Servo valves
meaning precisely timed and measured
forces can be applied to the table to
match any earthquake now because the
actuators can only move in one dimension
if they were fixed directly to the table
there would be no flexibility and they
would break and so the engineers at e
defense designed bespoke 7 m long
universal joints to transfer the force
from the actuators to the shake
table to simulate real earthquakes the
shaking can't be random I mean each
earthquake has its own characteristic
pattern of movement which can be
recorded using a seismometer early
seismometers were basically just a pen
attached to some Springs drawing a line
over a moving roll of paper and when
there was an earthquake the pen would
shake and draw out the pattern of
acceleration of that earthquake the
trace that was seen on the paper is
known as a seismic graph nowadays we use
geophones a geophone is made from a coil
of wire suspended around a magnet all
held together by Springs when the ground
shakes the Springs Shake causing the
wire to move up and down over the magnet
which generates a current this current
is recorded to produce a seism graph to
get the full picture of how the Earth's
surface moves in all three dimensions
three geophones are needed one oriented
in each orthogonal
Direction the strength of an earthquake
is measured on the magnitude scale the
smallest earthquake that humans can feel
is about a billion times less powerful
than the biggest earthquake ever
recorded because of this the magnitude
scale is logarithmic an increase of one
on the magnitude scale represents a
10-fold increase in the force of the
earthquake an earth earthquake under 2.5
on the magnitude scale is imperceptible
to humans these happen millions of times
every year but can only be detected by
geophones earthquakes higher than six on
the magnitude scale can damage buildings
but occur far less frequently only a few
hundred times a year
globally the most powerful earthquake
ever recorded was the great Chilean
earthquake of 1960 which measured 9.5 on
the magnitude scale it killed somewhere
between 1 and 6,000 people and caused
more than $400 million us worth of
damage but how destructive an earthquake
is isn't just determined by the
magnitude it also matters how close the
epicenter
is behind me is what was until 2022 the
world's longest suspension bridge the
Akashi kol Bridge connects honu the main
island of Japan to aaji Island nearly 4
km away the center span the distance
between the two towers is 9 1990 M and
80 cm I'm here because a few kilm that
way and 16 km underground was the
epicenter for the Great hunin Earthquake
of
1995 as the earthquake struck the bridge
was still under construction and despite
being right above the epicenter there
was no major damage to the structure but
the Earth underneath the bridge had
moved and the original plans would no
longer work
the plans would need to be modified so
that's how the world's longest
suspension bridge became 80 cm
longer after e defense opened in 2005
one of their first tests was a
comparison between two traditional
Japanese wooden houses the houses were
transported from the nearby city of
Akashi they were rebuilt on the table
and shaken at the magnitude of the coob
earthquake
the house that stayed up had been
retrofitted with wooden braces beams and
metal joints making it more earthquake
resistant the other was
unmodified this test demonstrated that
older Japanese houses are not able to
withstand powerful
earthquakes it also presented a
solution some relatively simple and
inexpensive structural reinforcement can
significantly increase earthquake
resistance in 1981 the Japanese
government introduces like all these new
building codes for new houses right and
they're like you need this kind of
seismic dampening you need this
isolation things you need these like
wooden beams of the buildings that were
built post
1981 in
coob
3% of them collapsed during this
earthquake of the ones that didn't
8.4% like about a 30 time difference
between new houses and old houses
right this this kind of like weird thing
like I was there on on day one you know
um watching like the shake table work
and I'm just kind of like looking around
uh this entire like this giant warehouse
and I see the section where it's just
like what looks like Ikea furniture can
you tell me what this is for to see the
know in room safety yeah we we place
lots of furniture in the uh structure
specimen a lot of the injuries right
that happen in earthquakes is from stuff
falling on top of
you a cabinet falling over and hitting
your head or you know you being crushed
by a fridge or something like that half
of the injuries um that were sustained
indoors in coob were from you know
Furniture falling on top of people so
one of the things that e defense does is
like how do you make sure buildings
don't collapse but it's also how do you
make sure let the insides of the
buildings are also
[Music]
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now back to
earthquakes so for this next test
they're going to feed in the seismic
signals from the Great hunchin
Earthquake which is also known as the
coob earthquake it only lasted for about
20 seconds but it had a magnitude of 6.9
and the maximum acceleration was about
.9 G which which is you know kind of
crazy to think about for an
earthquake
go oh
boy that like that
Rumble oh
man oh the whole building is oh my
God
how short that was and how powerful that
was Boy earthquakes are no joke that's a
nice way to observe an earthquake like
how else can You observe an earthquake
without being subject to that shaking
right no one has got to experience the
coob earthquake from like just right
beside it but not
shaking in KOB earthquake uh we recorded
very very large motion but it's very
short but in 2011 is Japan earthquake we
recorded very very long duration motion
like five five minutes and uh the bottom
one it's expected earthquake in future
toai Tona earthquake so we are expecting
very very long duration motion you how
do you predict what kind of earthquake
you're going to get uh ask i l
seismologist I no that's good that's
good seismologists give a 70% chance
that a magnitude 8 earthquake will occur
somewhere near the takai region home to
more than 15 million people within the
next 30 Years the nangai trough located
off the Southeast coast of Japan is
where the Eurasian plate pushes against
the Philippine plate and produces a
massive earthquake every 100 years or so
but the takai region hasn't experienced
such an earthquake in over 160 years the
government estimates that more than
320,000 people could lose their lives
most fatalities will likely be caused by
the 30m tsunami but a quarter around
82,000 could result from building
collapse this is why earthquake
preparedness is such a big
deal newly built buildings are very very
safe we you know they they have very
high seismic performance so uh even in
uh very very large earthquake uh you
know these buildings can survive except
in extreme cases most new buildings in
Japan can survive most large earthquakes
so the next challenge is to keep them
functional currently even when buildings
don't collapse water pipes often burst
leaving people without water and
electricity and so they still have to
leave their homes this is the next
challenge they're trying to solve at Eed
defense so now we can prevent a fatal
collapse but now we have to think how to
prevent this kind of functional row you
guys are now at the step that's beyond
what I was thinking right it's my my
step was like how do we make sure that
houses don't fall down and you guys are
like yeah no we figured that out we can
make sure that houses don't fall down
more or less doing this very important
work like you guys are making the world
a safer place you guys are making Japan
a safer place you're updating building
codes to make it you know so fewer
people die what I love about the story
of e defense is that Japan didn't simply
wait for more earthquakes to happen and
just hope for the best they spent
billions in research to prevent people
suffering from these disasters they
realize that while they can't predict
the next big earthquake they can make
sure that they are prepared when it does
happen