>> Earth, a 4.5-billion-year-
old planet, still evolving.
As continents shift and clash,
volcanoes erupt, and glaciers
grow and recede, the Earth's
crust is carved in numerous
and fascinating ways, leaving
a trail of geological
mysteries behind.
In this episode, an
investigation into
California's San Andreas
Fault, the greatest fault line
on Earth. 800 miles long, this
ugly scar on the landscape has
spawned Earthquake after
Earthquake.
But, for now, it waits
quietly, deep under our
cities, building up stress to
strike once again.
The San Andreas Fault is one of
the most dangerous geological
features on Earth.
S01x01 San Andreas Fault Original Air Date on February 10, 2009
-- Sync, corrected by elderman -- -- for www.addic7ed.com --
California's greatest cities
and millions of her citizens
live in constant peril.
Since records began, there
have been 13 large Earthquakes
along the San Andreas Fault.
>> Reporter: The water lines
have ruptured, there is no
water coming out of the fire
hydrants.
>> And now, America's
geologists, her rock
detectives, are warning of
a potential disaster.
>> Reporter: The major damage
has been done.
>> In the fall of 2008, more
than 300 scientists calculated
what a major Earthquake would do
to Southern California.
>> We've been conducting a
special study of a magnitude
7.8 Earthquake on the southern
San Andreas Fault, large
enough to potentially damage
tall buildings. Fire will be
very significant.
>> The definitive scientific
report presented to
politicians was codenamed
Shakeout. It forecast
thousands of deaths and
nillions of dollars of damage
in the city of Los Angeles,
which makes it crucial to
investigate the most important
question--when will the next
big Earthquake hit the San
Andreas Fault?
The latest preparations for
disaster are the climax of an
investigation that started
more than 100 years ago, in
the aftermath of the great San
Francisco Earthquake of 1906.
The Earthquake struck on a
wednesday, just before dawn.
The ground shook violently for
45 seconds, igniting fires
that raged unchecked for the
next four days.
28,000 buildings, a tenth of
the entire city, were
destroyed, and more than 3,000
people, one in every hundred
of the population, were
killed. With a magnitude of
7.8, it's in the top 20 of
North America's strongest ever
Earthquakes.
The scale of the great San
Francisco Earthquake shocked
the nation. But no one
understood what had made the
city shake.
Native American myths
explained Earthquakes as
shocks from a battle between
warring spirits. Latter-day
explorers couldn't understand
the shocks that destroyed
their mission buildings.
One spanish missionary wrote--
>>
>> "The Earth shook around me
from explosions under the
ground."
300 years later, and science
has still made little
progress. Refugees in the
ruins of San Francisco still
blamed Earthquake on
mysterious underground
explosions.
So, just three days after the
Earthquake, the state of
California asked one of the
world's most famous
Geologists, Andrew Lawson from
California State University,
to investigate what had
destroyed the city.
He and a team of 25 scientists
began collecting damage
evidence in the city and
surrounding countryside.
There were roads that had
buckled. Rail tracks that had
twisted the most startling
evidence of all? That came
near the town of Bolinas in
Marin county, to the
North of San Francisco. This
picket fence had an eight-foot
gap in the middle. Before the
earthquake, it was a solid
boundary fence, dividing
two fields. But, when he
recreated what had happened,
Lawson realized that the land
had jolted apart and torn the
fence in two.
Plotting the evidence on a map
around San Francisco revealed
a surprising pattern, because
connecting the dots drew a
straight line, and, at every
point, the Earth moved in the
same way. On the coast to the
North, inland to the South.
This line of weakness was the
culprit they were searching for.
South of San Francisco,
the suspect line ran
underneath a lake, the Laguna
De San Andreas. So now, the
earthquake perpetrator at last
had a name. Professor Lawson,
who, a decade earlier, had
identified cracks in the Earth
here as a harmless rift, now
rechristened it the San
Andreas Fault.
In modern-day San Francisco,
the buildings, the roads and
the railways have long since
been repaired. But, if you
know where to look, evidence
of the 1906 quake can still be
found.
Geologist Charlie Paull
follows in the footsteps of
Lawson's team, seeking signs
of the havoc from 1906.
He finds it on the cliffs at
Mussel rock, 12 miles south of
San Francisco.
>> The cliff is not here by
accident, there's a very good
reason why this cliff is here.
Half a mile or so of the shore
face apparently fell off in
the 1906 Earthquake, and if you
look down below us, there's a
big rotated block, um, that's
near the present-day shoreline,
and it is just inboard
of the San Andreas Fault, the
San Andreas Fault is, uh,
about a quarter of a mile
offshore here, and of course,
that's one of the major
crustal junctions, um, on
this side of North America.
>> Modern computers can now
trace how damage waves spread
out across the city. And that
pinpoints where the quake
originated along the San
Andreas.
It was offshore, about two
miles out to sea from the
Golden Gate Bridge.
So, to continue tracking the
fault, the investigation must
head out to sea. Marine
Geologists use remote
operating vehicles,
mini-submarines, to map the
sea floor.
>> What you would see is
subtle variations in the
topgraphy, or topography that
would not naturally line up.
So there might be a line on
the ocean floor that is higher
or lower on one side, and you
can use various techniques to
determine that this actually
is a fault, instead of some
other process.
>> Running south across the
seabed, the San Andreas
finally runs out of ocean, and
hits the land. This broken
line of rocks, stretching in
from the sea, marks where the
San Andreas hits land, 12
miles south of San Francisco.
>> We're here at Mussel Rock
and we're essentially standing
on the San Andreas Fault right
now. And if there was an
earthquake, I don't know what
would happen right here, but I
wouldn't want to be here.
>> This Pacific coastline,
where cliffs crumble slowly
into the sea, is the boundary
between two of the Earth's
massive continental plates.
Separated by the San Andreas
Fault, two vast, separate
blocks of the Earth's crust
lie directly alongside each
other.
Here, the continent of North
America lies slightly on top
of the adjacent section of
crust which holds the Pacific
Ocean.
The join can be seen where
these lower, darker rocks are
overlaid by light-colored
sedimentary rocks.
>> These rock types differ
by--by, uh, more than 100
million years in age. Two rock
bodies that, uh, are
not similar in any way have
been brought together.
>> The fault line was exposed
to geologists when the cliffs
collapsed here in the 1906
Earthquake. But, back then,
nobody understood how and why
the two different types of
rock were next to each other,
until around 40 years ago,
when the answer was finally
revealed by the theory of
Plate Tectonics.
The theory showed that the
Earth's crust consists of
separate, moving plates on
which the oceans and
Continents sit.
Around 200 million years ago,
the heavy Pacific Ocean plate
collided with North America,
and started sinking underneath
the lighter Continent.
Professor of Geophysics, Mark
Zoback, studies that process,
called subduction, in his
laboratory at Stanford
University.
>> For many millions of years
prior to the existence of the
San Andreas Fault, the Pacific
Plate was subducting beneath
North America, the Oceanic
Plate was diving down, and,
uh, that process went on for
well over a hundred million
years, so a tremendous amount
of activity was occurring.
>> As the unstoppable force of
one plate met the immovable
object of the other, they were
forced to change direction.
>> About 20 million years ago,
the plate motions were such
that the Pacific Plate had to
start sliding north with
respect to North America,
and now, you know, the--the
principal motion is this
sliding process between the
two plates. And 20 million
years ago, the San Andreas
Fault was born.
>> It was the moving plates
that crushed different types
of rock together, just as here
at Mussel Rock.
At last, the investigation
knows what it is dealing with.
The San Andreas Fault is 800
miles long, emerging from the
seabed north of Point Arena
in Northern California and
running down to the Salton Sea
in the south.
The evidence is coming
together. Clues from the 1906
Earthquake, such as the picket
fence that was torn apart,
prove that the land was
moving. Connecting the dots
identifies the straight line
of the San Andreas Fault.
And Mussel Rock uncovers
different plates of the
Earth's crust on either side
of the fault line.
But investigators still need
more information about how
often the San Andreas has
spawned Earthquakes in the
past.
It might help them answer the
all-important question--when
will the San Andreas strike
again?
To discover when the San
Andreas Fault will strike
again the investigation needs
to know about ancient
earthquakes that have struck
along the fault line.
But there's an immediate
problem.
>> Here in California, it's a
particular challenge, and
some of the earliest written
records were from the missions
and from the early explorers,
So only dating back into the
18th century here. Other
parts of the world, we have an
earthquake history going back
millennia.
>> The investigation moves 350
miles south of San Francisco
to a desert where the San
Andreas may have been active
for thousands of years.
There's crucial evidence here
about earthquakes from ancient
times.
>> This creek used to flow
straight across the San
Andreas Fault here, but
several earthquakes formed a
natural dam where the San
Andreas Fault wedges up here
in front of me. That created a
small pond, and now we're
looking at the dry sediments
of that pond that record the
history of earthquakes, and
that tells us quite a great
deal about the past behavior of
the San Andreas Fault.
>> Some of the clues are so
small that Hudnut's detective
work gets him down and dusty
among tiny cracks inside the
fault.
>> Sometimes we can find out
about the past behavior of
the San Andreas Fault by
looking at the tiniest
details.
>> At the bottom of this small
ancient pond, mud sediments
collected above a fine line of
pebbles. Then an earthquake
shifted the land upwards on
one side of the vertical fault
line.
>> So this layer was
originally flat, and then, in
a subsequent Earthquake, it
was broken like this along
this tiny fracture strand of
the San Andreas Fault.
>> But finding proof that this
is the site of an ancient
earthquake is only part of the
story. Hudnut needs to know
how long ago it happened.
The bare rock layers are no
help in dating his find, but
just above the fracture line
of the rocks he has found the
evidence he needs.
>> Here, a bush was burned by
a prehistoric wildfire, and
that remnant of carbon is why
you see this black stain on
the side of the trench wall.
>> The key to unlocking the
age of the rocks is carbon-14,
known as radiocarbon.
Its molecular structure
means that carbon-14 is a
more unstable isotope than
other forms of carbon.
It's absorbed by growing
plants, then radioactively
decays at a known rate, after
the plant dies. So measuring
carbon-14 in vegetation burned
in a wildfire reveals how long
ago those plants died, and
dates the rock in which the
carbon is found.
>> And through this, we can
reconstruct the evidence of
the past earthquakes.
>> Radiocarbon dating has
proved that earthquakes have
been happening along the line
of the San Andreas for
thousands of years. The
particular small earthquake
investigated by Hudnut, for
example, is around 3,500 years
old. It happened at a time
when the last Woolly Mammoths
were dying out in North America.
The investigation moves to an
even more remote desert spot.
The Carrizo Plain, 160 miles
north of Los Angeles. Here
lies a dried-up riverbed,
which takes an unusual
course. Coming down off the
hills, the creek bed takes a
sudden, sharp turn to its
right. A few hundred feet
later, it makes an equally
odd, 90-degree turn to the
left.
The creek crossed the line of
the San Andreas Fault, but
early geologists were
mystified. Why did it bend in
this way?
The scientific pioneers were
limited to studies on the
ground. Nowadays, Hudnut has an
advantage. He can take to the
air.
>> the San Andreas Fault,
Where it cuts though the
Carrizo plain, it almost looks
Like a scar, and it was caused
by repeated earthquakes in the
past.
>> Along the long line of
hills marking the course of
the San Andreas, Hudnut spots
the puzzling bends that he's
seeking.
>> Hudnut: Oh! If we could
woop along the fault through
here, that would be awesome.
Oh, there's a great angle, see
that right angle, uh, offset
channel with the elbow in it
right there? That's a classic
one right there.
>> Hudnut's aerial view of
the creek bed shows that the
river once flowed straight on
cross the fault. But, little
By little, a series of
Earthquakes along the San
Andreas dragged the creek away
from its original course.
Recreating how the land had
moved showed Hudnut that the
two parts of the creek had
traveled more than 300 feet
apart.
>> So if you imagine the North
American plate is fixed and
the Pacific Plate is moving to
the northwest, the Wallace
Creek site records that offset
because the channel is
straight across the fault,
but it's been offset through
time.
>> Earlier investigators had
already radiocarbon-dated the
land on each side of the fault
here, revealing that it took
3,000 years to change the
creek's position.
So, knowing the distance and
the time it took to do it lets
Hudnut calculate the average
speed with which the two land
masses are moving past each
other.
300 feet in 3,000 years,
one foot per decade,
just over an inch a year.
But this was never a steady,
sliding, one-inch-a-year
movement. The reality was a
series of sudden small jumps
whenever tension built up
enough between the two
moving plates to overcome
friction between the rocks and
rip the land apart with an
earthquake.
It's an important moment for
the investigation. Knowing how
fast the land is moving not
only reveals the stress that's
building up, but also the risk
of an earthquake.
The San Andreas Fault is
giving up its secrets. Clues
from a long dried-up pond
reveal the site of ancient
earthquakes. Carbon from a
prehistoric fire provides the
dates. And bends in a riverbed
prove how fast the plates are
moving along the San Andreas.
But now, the investigation has
a new mystery to solve. If the
land along the San Andreas is
moving one inch every year,
causing earthquakes, then why
has one small town along the
fault line never had any?
The investigation has
discovered how fast the land
is stretching and straining
along each side of the San
Andreas Fault, which should
help establish when that
ever-increasing stress will
snap the land apart in the
next major earthquake.
But there's a problem. One
oart of the fault line just
doesn't fit the pattern.
The small town of Hollister is
unique along the San Andreas
Fault system. It's never had
an earthquake. And the
investigation is going to find
out why.
Hollister has a population of
37,000, and nothing here is
quite the way it should be.
There are plenty of clues
suggesting that the land must
be moving here.
Sidewalks with cracks in,
curbstones way out of line and
walls that are bent out of
shape.
>> Walking through Hollister,
we can see anything that man
has built that was laid out in
a straight line may have a jog
in it. Every year it changes a
little bit, it's a progressive
thing.
>> The clues add up to one
clear conclusion. Even without
any earthquakes, the Earth in
this town in the heart of the
San Andreas system still
slides imperceptibly slowly
and effortlessly along.
>> In one sense, the damage
that you see here associated
with the creeping is, uh, is
clearly sort of under control.
But as a geologist, if you start
playing that out for tens of
thousands or hundreds of
thousands or millions of
years, the consequences of
that become enormous.
>> For many years, the
creeping ground that moved
without earthquakes remained
an unsolved mystery.
But then, the investigation
moved 100 miles south, to
another small community, where
the land also creeps along.
The village of Parkfield has a
population of just 37 people,
and a bridge which spans right
across the San Andreas Fault.
The bridge separates the
Pacific Plate on one side from
the North American Plate on
the other. And the bridge
railings have started to bend.
>> I'm, uh, right now on the
Pacific Plate on the west side
of the San Andreas Fault, and
you know, the--the San Andreas
comes off the flank of that
hill and right across that
field, right under the bridge,
and then, right over by the
corner of that building or
that fence post and then on
off to Middle Mountain.
>> The movement here around
the bridge is strikingly
similar to the slow creeping
ground of Hollister.
But there is one important
difference here in Parkfield.
Every couple of decades or so,
this village does have
earthquakes. They're just
little tremors, but they're
big enough to be recorded on
earthquake monitoring
seismographs.
That's why the village proudly
boasts of being the earthquake
capital of the world. But it's
perhaps more accurately called
the earthquake study capital
because scientists are
fascinated by the fact that
earthquakes here follow a
predictable pattern.
Elsewhere, earthquakes always
strike without warning, the
toll of death and destruction
made worse because nobody knew
they were coming. So
scientists are desperate for
any clues that might help
predict when an earthquake
could happen. And here in
Parkfield, the earthquakes
happen with astonishing
regularity, on average, every
couple of decades or so. Minor
quakes happened here in 1857,
1881, 1901, 1922, 1934 and
1966.
After the '66 Earthquake,
investigators set up a network
of monitoring instruments to
see if the fault gave any
warning before the next
earthquake arrived.
They expected it sometime
between 1988 and 1993, but it
was late. And months of
waiting stretched into years.
But still the scientists
waited, until finally, in
December 2004, the
long-awaited earthquake
arrived and was caught on
film, from a now slightly worn
and damaged camera.
The Earthquake movie may not
have seemed that impressive,
but the instruments collected
a mass of information.
The data didn't, after all,
help with earthquake
prediction, but it did
pinpoint where the earthquake
started underground, which
told investigators where to
look next, deep down under the
Parkfield countryside.
Starting slightly to one side
of the fault, the aim was to
angle in and stab into the
very heart of the San Andreas.
After three years of drilling,
long cores of rock were
extracted from the exact spot
where the Earthquake occurred.
This was first time the team leader
geologist Mark Zoback had ever
seen rocks from the center
of the San Andreas.
What we're looking at here
are cores from the
active San Andreas Fault,
from a depth of about 2 miles.
So for the Earth science community
these are like Moon rocks.
As we were trying to exhume
these cores, we had a great
deal of drilling difficulty.
The San Andreas Fault was
literally fighting back.
After 9 weeks of attempting
to recover the cores in the middle
of a huge lightening storm
almost a scene directly
out of Hollywood,
with the thunder and lightening,
these cores came to the surface.
And so it was a tremendous
feeling of satisfaction.
The lightening and thunder
just made it that much more
dramatic.
And we're all wearing gloves
we didn't want any oil
from our fingers to affect the core.
And the rule was
that you touched the core
as little as possible.
Obviously.
>> I'm not going to wait for
you guys. Oh, look at this
beautiful rock.
>> The reality was we couldn't
help ourselves, and, uh, um,
it was just such a remarkable
thing to be actually looking
at the San Andreas Fault, uh,
for the very first time
that--that we all got to touch
it a little bit.
>> Buried within the rock
cores, they found a vital
clue about the way that land
slips along the San Andreas.
They found serpentinite.
>> Serpentinite is an unusual
rock type, it was originally
formed, uh, at the base of the
Ocean crust and exhumed up
onto the continent, but the
reason that serpentinite is so
interesting is that
serpentinite is very easily
altered to talc. It allows the
rock to slide at very low
force levels, it's--talcum
powder is very slippery.
>> Talc's crystalline
structure of soft, sliding,
flat plates makes it one of
the slipperiest rocks known to
science.
>> So talc could well be, um,
a key mineral in--in deciding
how the fault is--is actually
working in--in central
California. We see that the
secret of the slipping San
Andreas Fault is actually the
rocks themselves.
>> The talc explains the tiny
earthquakes of Parkfield.
Nobody's yet drilled to
investigate the rocks at
Hollister, but scientists
suspect the talc is present
there too. Cracks in the walls
show the land creeps in
Hollister. And a bend in the
bridge reveals the same
creeping ground in a
nearby town. Rock cores,
extracted from the fault,
contain serpentinite,
leading investigators to the
softest and slipperiest
mineral, talc, which
lubricates some parts of the
Fault. The investigation is
having success, but one
crucial question remains to be
answered. What will the San
Andreas Fault do next?
The investigation into the San
Andreas Fault is trying to
predict when and where its
next major Earthquake will
strike. So far, the only
certain prediction is the far
distant future of the San
Andreas.
Look 20 million years ahead.
If the plate movements
continue to follow their
pattern, Los Angeles will end
up becoming a suburb of San
Francisco.
But predictions on a shorter
timescale are more difficult.
>> If you were to ask the
question, "can we predict
Earthquakes?" my answer would
be, "no, because I know what
your question really meant,
is, you know, 'can we predict
that an Earthquake is going to
occur on a certain fault at a
certain time that we can
specify in the future?'"
And we cannot do that. But
there are many things we can
predict. We can predict which
faults are likely to produce
the big earthquakes, we can
predict how big the
earthquakes are likely to be,
and we can even predict the
probability of the earthquake
occurrence over some period of
several decades.
>> Predictions are most
crucial where the San Andreas
runs to the south of L.A.
Here in the Coachella Valley
Desert, geological evidence of
earthquakes stretches back
1500 years and more.
And they follow a regular
pattern. Major Earthquakes
strike here with monotonous
regularity, every 200 years.
But the latest one is long
overdue. There hasn't been an
earthquake here for more than
300 years. That's a concern,
because parts of the San
Andreas Fault system run
straight from here towards the
city of Los Angeles.
The faults will transmit
earthquake shocks in a
straight line towards
California's biggest city.
Geologist Yuri Fialko
regularly monitors how the
ground moves on either side of
the fault line.
He lines up his gps equipment
precisely over a series of
metal pegs fixed into the
ground.
>> This information is crucial
for estimating how fast the
Fault slips at depth and what
is the rate of accumulation of
strain in the crust. In other
words, how close the crust is
brought to failure by a slip
of the fault at depth.
>> The repeated, ultra-precise
measurements reveal that land
here, on the surface, hardly
moves at all. This is a
problem, because deep
underground, the stresses and
strains are still building up.
>> The fault is moving, at
depth, at a fairly high speed,
and this deformation is
growing and growing and
growing with time.
>> Miles underground, the deep
fault is moving at more than
an inch a year, which tells
Fialko that in the centuries
since the last quake, the
surface should have shifted
300 inches, 25 feet or more.
But it hasn't, so sooner or
later, something's got to
give. And Fialko knows what
that something will be.
The rocks themselves.
>> And one example is this
type of rock, which is called,
uh, granite, and this is in
fact the rock out of which
most of the Earth's crust is
made.
>> A microscope reveals the
crystalline structure of the
granite. The crystals make the
rocks tough, but they have a
hidden weakness. The bonds
between them may suddenly
crack under stress.
>> Basically, once this
material solidifies, uh, it is
able to, uh, um, crack and be,
uh, sheared on the fault
surface, and the brittle
behavior of these rocks is
what lies behind the physics
of Earthquakes.
>> Granite rocks underlie all
of the San Andreas Fault, but
right here, the rock's under
greater stress than anywhere
else, because it's so many
centuries since a major quake
occurred.
>> And now we're over the
300-year limit, and so it means
that, uh, the strain, the
amount of strain that has been
accumulated on the fault at
this point is very close to
the maximum strain that this
Fault has ever seen through
its, uh, geologic record.
And this is a fault that is
capable of generating great
destructive Earthquakes.
>> Fialko believes the coming
quake could be "the big one"
that people have been talking
about for years. And the
effects could be horrific
because of the population
density of southern
California. When the last huge
quake occurred 300 years ago,
Los Angeles was just a tiny
Spanish mission community with
fewer than 100 people.
Now, it's America's
second-largest city, with
almost 11 million people living
in the Earthquake-vulnerable
Metropolitan area.
>> People who live in
California probably experience
a small or a moderate size
earthquake every year, a few
things moving in your house,
but it's really actually kind
of fun, there is no major
destruction. Um, people just
go on with their life. Uh,
much bigger events, on the
other hand, are quite a bit
different story.
>> With the threat to Los
Angeles becoming ever clearer,
the investigation is nearing
its conclusion. Data from
repeated gps measurements in
the desert reveal evidence
that stress is building up,
while examination of the rocks
of the crust show they may not
take the strain for much
longer.
All the evidence points
towards a potentially huge
earthquake building up in
Southern California.
And new experiments suggest
the coming quake could be far
worse than anyone had ever
imagined.
There is new urgency in the
investigation into the San
Andreas Fault as revealed by
recent evidence compiled by
300 of America's most
respected scientists.
They warn that Los Angeles
will be devastated if a major
quake strikes along the
Southern section of the
Fault line.
While there hasn't been a
major quake for hundreds of
years, even small ones can
still be deadly, like the
Northridge Earthquake, which
struck this L.A. suburb in 1994.
Rupturing along an offshoot of
the main San Andreas Fault,
the quake was only a magnitude
6.7, considered moderate on
the scale of Earthquake
Measurement.
But it still killed 72 people
and injured 12,000 more.
And new evidence suggests
Mother nature might have a lot
more in store for Los Angeles.
Scientists have long known
that Earthquakes generate
several distinct sets of
waves. They travel at
different speeds, each
spreading damage and
destruction out from the
epicenter.
Modern city buildings in
earthquake-prone areas like
California are engineered to
cope with such waves.
Now, new research by
Geophysicist professor Ares
Rosakis suggests that the San
Andreas may offer a new and
even more deadly threat.
Rosakis researches how
earthquakes rupture along
straight-line faults, just
like the San Andreas where it
approaches Los Angeles.
He creates his own
mini-earthquakes, representing
the San Andreas Fault by a
hairline crack in a thick,
transparent block.
This special material shows up
internal stress lines when
It's lit by a laser.
And the Earthquake is
triggered by a tiny explosion.
>> Three, two, one, zero.
The node has dropped, and the
explosion was big enough that
we even have a crack.
>> An ultra-high-speed camera
capturing ten million frames a
second, reveals a startling
and newly discovered
phenomenon.
This frozen picture reveals
stress lines speeding along the
mini San Andreas in the
milliseconds after the
explosion.
The cone to the left of this
frame is a previously
unrecognized type of shockwave
racing along the rupture line
from the Earthquake center.
On a microscopic scale, it
looks and moves exactly like
the sonic boom produced when a
supersonic aircraft, such as
Concorde, breaks the sound
barrier.
>> Because we also see mach
cones, lines that are emitted
from the rupture tips, as from
the tips of moving airplanes.
>> And, just like a sonic
boom, it can be dangerous.
>> In the same sense that we
hear the sonic boom, uh, from
the Concorde, you are going to
feel the sonic boom from the
rupture.
>> The danger comes because
many high rises just aren't
built to cope with extra
stress from this newly
discovered type of shockwave.
>> So if you are an old
building, for example, uh,
you'll shake one way, you will
accumulate some damage, and,
uh, very soon after that, you
will get very strong ground
shaking because of other types
of waves coming also.
>> The high-speed ruptures
that Rosakis calls supershear
happen where faults run in a
straight line...
which might help explain a
100-year-old mystery
surrounding the great
San Francisco quake, the
natural disaster which
launched the entire San
Andreas investigation.
The overwhelming damage in San
Francisco has long seemed
surprisingly out of proportion
to the 7.8 magnitude of the
quake. And there's a
particularly straight section
of the San Andreas approaching
San Francisco. So, many
scientists now believe that
the damage was greater than
expected because the 1906 quake
had traveled at supershear
speed.
Of greater concern to modern
emergency services is not what
happened a century ago, but
what could happen tomorrow,
because there is a similar
straight section of faulted
ground heading straight
towards Los Angeles, and if a
supershear Earthquake develops
on that line, then the
consequences could be
disastrous.
>> Here we go.
>> All of the investigation's
warnings about the San Andreas
came together in the fall of
2008, with the biggest
earthquake drill ever held in
California.
>> If this Earthquake would
have happened in reality,
there--there would have been
buildings coming down, we know
that there would be no water
now in certain areas, that's
what this exercise is all
about.
>> But what are the real
chances of Los Angeles soon
being hit by a massive
earthquake? Frighteningly, the
best scientific consensus now
warns that there's a 99 per
cent chance of a major quake
in Southern California within
the next 30 years. To better
understand the threat to L.A.,
the geologists produced their
study jointly with experts in
charge of the city's disaster
planning. And none of them
doubt that the big quake is
coming.
>> It really isn't even a
question of if anymore.
The shaking is going to be
severe for two to three
minutes.
And then it's gonna stop,
and then you're gonna have that
moment of silence that often
happens before you start
hearing the car alarms, all
those other sounds that you
have in a disaster like this.
>> The study estimates that a
major Earthquake in the L.A.
Metro area would cause 2,000
deaths, 50,000 injuries and
200 billion dollars of damage.
>> You're going to have
conflagrations developing,
tens of blocks will be on fire.
>> Reporter: The water lines
have ruptured, there is no
water coming out of the fire
hydrants.
>> That's the kind of nightmare
scenario that we're looking at.
>> This specter of disaster to
California's people and cities
motivates the search to
unravel the secrets of the San
Andreas Fault. All the
evidence is finally in.
The damage reports from the
1906 disaster show the fault's
800-mile path. The different
types of rock at Mussel Rock
provide clues to how the fault
was created 20 million years
ago. The river bends prove how
fast the land is moving. The
mineral talc explains why some
parts slip without major
quakes. The brittle granite
rocks reveal a threat to Los
Angeles, and recent lab
experiments uncover new and
more dangerous Earthquake
Shockwaves.
But one goal has eluded the
rock detectives who study
the greatest fault line on
Earth.
When will the sleeping San
Andreas come to life once
again? It could be any time.
The only certainty is that
nothing is certain in the
ever-evolving story of how the
Earth was made.
-- Sync, corrected by elderman -- -- for www.addic7ed.com --